Decoding m6
A mRNA methylation by reader proteins in cancer
Bing Han a
, Saisai Wei a
, Fengying Li a
, Jun Zhang a
, Zhongxiang Li b
, Xiangwei Gao a,*
a Sir Run-Run Shaw Hospital, School of Public Health, Zhejiang University School of Medicine, Hangzhou, 310058, China b Medical Research Institute, Baoan Women’s and Children’s Hospital, Jinan University, Shenzhen, 518133, China
ARTICLE INFO
Keywords:
m6
A modification
YTH domain protein
mRNA metabolism
Cancer
m6
A editor
ABSTRACT
N6
-methyladenosine (m6
A), the most prevalent internal modification in eukaryotic mRNAs, regulates gene
expression at the post-transcriptional level. The reader proteins of m6
A, mainly YTH domain-containing proteins,
specifically recognize m6
A-modified mRNAs and regulate their metabolism. Recent studies have highlighted
essential roles of m6
A readers in the initiation and development of human cancers. In this review, we summarize
recent findings about the biological functions of YTH domain proteins in cancers, the underlying mechanisms,
and clinical implications. Gene expression reprogramming by dysregulated m6
A reader proteins offers potential
targets for cancer treatment, while targeted m6
A editors and readers provide tools to manipulate m6
A meta￾bolism in cancers.
1. Introduction
Chemical modifications of RNA are critical for gene expression at the
post-transcriptional level, which subsequently induce changes in bio￾logical outputs. In particular, the N6
-methyladenosine (m6
A) modifica￾tion on RNAs, methylation at the sixth position nitrogen atom of
adenosine (A), is an essential regulator because of its high abundance: it
has been found in 0.1–0.4 % of messenger RNA (mRNA) adenosine
residues in diverse eukaryotic cells [1–3]. Despite the early discovery in
various cellular mRNAs in the 1970s, the distribution of m6
A was
recently clarified with the development of detecting methodologies
(m6
A-seq and its derivatives) [4,5]. These methods allow analyzing m6
distribution at the transcriptomic level, opening up the era of “epi￾transcriptomics”. Mapping of m6
A in different organisms revealed a
highly conserved feature of this modification. A consensus motif of m6
modification, RRACH ([G/A/U][G/A]m6
AC[U/A/C]), has been identi￾fied by the m6
A-seq data [5,6]. As for the exact positions, m6
enriched around stop codons and in the 3′ untranslated regions (3′
UTRs) [4,5]. In addition to methodological breakthrough, the charac￾terization of its enzyme system further brought this modification into
the spotlight [7]. It is now known that the m6
A modification is
dynamically regulated by methyltransferases (‘writers’) and demethy￾lases (‘erasers’) [8,9]. The writers, including core methyltransferase
components (METTL3 and METTL14) and their cofactors (WTAP,
RBM15, HAKAI, VIRMA, and ZC3H13), promote the deposition of m6
on mRNAs [10]. The reversibility of m6
A relies on erasers, including
FTO and ALKBH5, leading to the removal of m6
A modifications for a
balanced equilibrium [7,9].
2. “Reader” proteins regulate the fate of m6A-modified mRNAs
m6
A methylation alters Watson-Crick base pairing strength, RNA
secondary structure, or protein-RNA interactions, which in turn affects
gene expression by modulating almost all aspects of RNA metabolism,
including processing, localization, translation, and decay [11–13].
“reader” proteins directly regulate RNA fate. Combined approaches
involving RNA affinity chromatography and mass spectrometry have
been used to identify several m6
A readers, including YT521-B homology
domain-containing proteins (YTHDF1-3 and YTHDC1-2) [5],
insulin-like growth factor 2 (IGF2) mRNA-binding proteins (IGF2BP1-3)
[14], FMR1 [15], and heterogeneous nuclear ribonucleoprotein
(HNRNP) protein family members [16,17]. These reader proteins
decode m6
A and decide the metabolic fate of modified mRNAs, indi￾cating that they are crucial in the regulation of RNA metabolism and
post-transcriptional gene expression.
m6
A readers process RNA at least through 3 mechanisms: selectively
binding, weakening the cognate binding proteins, altering the secondary
structure of RNA and RNA-protein interactions [8]. Highly conserved
YTH domain proteins selectively bind to m6
A modifications with high
affinity and a large binding interface, further altering the secondary
structure [18]. Interestingly, these m6
A readers have distinguishing
* Corresponding author.
E-mail address: [email protected] (X. Gao).
Contents lists available at ScienceDirect
Cancer Letters
journal homepage: www.elsevier.com/locate/canlet
Received 13 May 2021; Received in revised form 25 July 2021; Accepted 28 July 2021
Cancer Letters 518 (2021) 256–265
features of RNA processing. YTHDF1 has recently been extensively
studied as a cytoplasmic m6
A reader. YTHDF1 binds to m6
A at exact G
[G > A](m6
A)C sites and promotes translation initiation by interacting
with initiation factors and ribosomes [19]. As a homologous gene of
YTHDF1, YTHDF2 was identified by RNA immunoprecipitation (RIP)
and photoactivatable ribonucleotide crosslinking and immunoprecipi￾tation (PAR-CLIP) experiments to have a conserved G(m6
A)C[U > A]
motif, and this protein plays an important role in RNA decay by
recruiting the mRNAs to processing bodies (P-bodies) [20]. With similar
sequence identity to YTHDF2, YTHDF3 facilitates m6
A-containing
mRNA translation and decay together with YTHDF1 and YTHDF2 [21,
22]. YTHDC2, another cytoplasmic YTH family member, regulates
mRNA stability by interacting with the 5′
-3′ exoribonuclease XRN1 and
enhances the translation efficiency of its targets in spermatogenesis and
oogenesis [23,24]. However, IGF2BPs represent a different facet of the
m6
A reading process, mainly promoting mRNA stability and translation
by recognizing the consensus GG(m6
A)C sequence [14]. As for
nuclear-specific m6
A readers, YTHDC1 preferentially recognizes the GG
(m6
A)C sequence and mainly functions in mRNA splicing and nuclear
export [25–27]. Heterogeneous nuclear ribonucleoprotein G and C
(HNRNPG/HNRNPC) are other two nuclear readers that bind m6
A to
regulate alternative splicing [16,28,29]. Additionally, another hnRNP
family protein, HNRNPA2B1, binds to m6
A in the pri-miRNA to facilitate
miRNA processing by recruiting a microprocessor [17] (Fig. 1).
3. Manipulating YTH domain protein-regulated m6
A metabolism
Recently developed m6
A editors offer a way to manipulate m6
specifically in individual transcripts [30–32]. Based on CRISPR/Cas
system, these editors compose a methyltransferase or a demethylase
fused with a catalytically inactive Cas proteins (dCas9 or dCas13). With
the help of guide RNAs (gRNAs), site-specific m6
A incorporation or
demethylation in specific transcripts could be achieved (Fig. 2). Studies
using these editors demonstrated that single site methylation in different
mRNA regions may play different roles, either promoting mRNA trans￾lation or degradation. In addition to these m6
A editors, targeted m6
readers have also been developed by fusing m6
A reader proteins,
YTHDF1 or YTHDF2, to dCas13b [33]. The fusion proteins can target the
reader to specific RNA of interest using gRNA (Fig. 2). Tethering tar￾geted mRNA with the fusion proteins can trigger enhanced protein
Fig. 1. The functions of m6
A reader proteins in
mRNA metabolism.
The m6
A reader proteins recognize m6
A and
determine target mRNA fate. The nuclear m6
reader proteins YTHDC1, HNRNPG, and
HNRNPA2B1 regulate mRNA splicing, nuclear
export, and pre-miRNA processing, while the
cytosolic m6
A reader proteins YTHDF1-3,
YTHDC2, and IGF2BP1-3 regulate mRNA trans￾lation and decay.
B. Han et al.
Cancer Letters 518 (2021) 256–265
production or RNA degradation. The development of dCas-based tar￾geted m6
A editors or readers reveal the effect of individual m6
A modi￾fications and dissect their functional roles.
4. The roles of YTH domain proteins in cancer initiation and
development
Abnormal epigenetic regulation contributes to cancer initiation and
development, during which m6
A has gained increasing attention in
cancer biology [34–36]. m6
A modification affects many cancer pro￾cesses through writers, erasers and readers, such as cancer initiation,
progression, metastasis, therapeutic response and cancer relapse [35].
For m6
A readers, accumulated evidence has shown that YTH domain
proteins have essential roles in various complicated cancer pathogen￾esis. Because of the various RNA fate outcomes mediated by these
readers, the m6
A machinery can play either oncogenic or
tumor-suppressor roles in different cancer contexts. YTHDF1/3 and
YTHDC2 are usually critical in promoting oncogene translation and thus
act as positive tumor markers. However, YTHDF2 is reported to have
dual roles in cancers that depend on the degradation of its target
mRNAs. We briefly summarized the recent studies on the functions of
YTH domain proteins in various cancers (Table 1). The dysregulation of
m6
A readers in human cancers highlights the potential of using these
proteins as new biomarkers and therapeutic targets in clinical practice.
5. Aberrant expression of YTH domain proteins in cancers
Emerging data have suggested that aberrant expression of YTH
proteins in many types of cancers (Table 1) could be strongly associated
with cancer progression and treatment outcomes. Many studies have
shown an increase of YTHDF1 expression in cancers, indicating a posi￾tive correlation with cancer pathogenesis (Table 1). However, how
YTHDF1 expression programs cells to adapt to long-term cancer envi￾ronmental changes remains largely unknown. DNA copy number alter￾ations [38] or transcriptional regulation [37] are both suspected to
account for the overexpression of YTHDF1 in certain cancers. For
example, in colorectal cancer (CRC), the oncogenic transcription factor
c-Myc was shown to be associated with the 5′ region of the transcription
start site of the YTHDF1 gene, indicating that c-Myc promotes YTHDF1
expression in CRC cells. Posttranscriptional regulation is also a key part
of controlling YTHDF1 expression. In the intestine, the activated
Wnt/APC signaling pathway promotes YTHDF1 translation by inter￾acting with its 5′ UTR [39]. MiR-376c was reported to directly target the
UTR of YTHDF1 in non-small-cell lung cancer (NSCLC) cells [40].
Moreover, YTHDF1 could be regulated by USF1 and c-Myc at both the
mRNA and protein levels in hepatocellular carcinoma (HCC) [49].
Despite the fact that YTHDF1 is dysregulated in cancers or at least can be
a risk factor for cancer initiation and prognosis, future research needs to
identify the upstream regulators of YTHDF1.
YTHDF2 has been found to participate in many cancers and might be
associated with cancer progression. Interestingly, YTHDF2 expression is
markedly inconsistent: it is upregulated in some types of cancers and
downregulated in others. For example, YTHDF2 is highly expressed in
bladder cancer, glioblastoma, acute myeloid leukemia (AML), lung
cancer, ovarian cancer and prostate cancer but expressed at low levels in
gastric cancer. Furthermore, YTHDF2 can act as either an oncogene or a
tumor suppresser in HCC. Similar to the situation for other m6
A readers,
evidence of how YTHDF2 responds to the cancer microenvironment is
still limited. Hypoxia has been identified as a key driver of low YTHDF2
expression in HCC, and induction of HIFs, such as HIF-1α and HIF-2α,
has been proven to mediate and enhance YTHDF2 function [78,79].
Recently, miRNAs have also been revealed as regulators of YTHDF2
expression. Luciferase reporter assays and statistical analysis confirmed
that YTHDF2 is a direct target gene of miR-145 in ovarian cancer [86]
and miR-495/miR-493-3p in prostate cancer [88,89].
6. YTH proteins in colorectal cancer
Colorectal cancer (CRC) is the third leading cause of cancer-related
death in both men and women worldwide. However, many cancer
cases and deaths could be prevented with appropriate screening and
surveillance, which indicates the high clinical need for precise tumor
biomarkers and therapeutic targets. m6
A related genes are found
abundantly expressed in colon cancer, including reader protein YTHDC1
and HNRNPC [94]. Recently, most related studies have indicated
YTHDF1 as a potential oncogene in CRC. Given that aberrant
Wnt/β-catenin signaling is the driving force for intestinal tumorigenesis,
some studies have focused on how YTHDF1 interacts with this pathway.
The studies revealed that YTHDF1 is upregulated in CRC tissues versus
normal tissues [39–41]. Deletion of the YTHDF1 gene in mouse intes￾tinal stem cells (ISCs) induces tumor shrinkage and prolongs survival by
blocking the Wnt signaling pathway [39]. In addition to playing a role in
ISCs, YTHDF1 is also involved in promoting cancer stem-cell like activity
by enhancing Wnt activity, which further regulates tumorigenicity in
human CRC [40]. According to The Cancer Genome Atlas (TCGA)
database, the expression of YTHDF1 in CRC also shows a positive cor￾relation with an important Wnt target gene, c-Myc. Mechanistically,
c-Myc activates the transcriptional activity of YTHDF1, promoting
cancer cell proliferation and increasing chemosensitivity [41]. However,
univariate and multivariate Cox regression analyses have clarified that
YTHDF1 is a negative prognostic factor for colon cancer [42]. Studies
revealed lower expression in the high-risk cancer group, indicating good
value for predicting prognosis. Further studies implied that YTHDF1
identifies the m6
A-modified ANKLE1 transcript, a tumor suppressor in
CRC [106], indicating that YTHDF1 may be required for
ANKLE1-regulated CRC inhibition and prevention. Similar to YTHDF1,
YTHDC2 contributes to colon cancer metastasis by promoting HIF-1α
translation, suggesting that YTHDC2 is a potential biomarker for diag￾nosis and treatment response evaluation for colon cancer patients [107].
In CRC, YTHDF3 was identified as a novel target of YAP signaling, by
which YTHDF3 selectively binds to m6
A-modified GAS5 to promote its
decay and triggers CRC proliferation and metastasis [92]. Unlike that of
other YTH domain proteins, the expression of YTHDF2 was unaffected in
CRC tissues compared to nontumor tissues. Nonetheless, the binding of
YTHDF2 to SOX4 mRNA can be increased to induce the degradation of
SOX4, indicating another view of the regulation and impact of m6
A on
CRC [73]. Another study shows that high expression of METTL3 pro￾motes m6
A-modified SOX2 mRNAs, which is subsequently recognized by
IGF2BP2 and leads to inhibition of SOX2 mRNA degradation [105].
Although these observations provide the significant signatures of YTH
domain proteins in CRC progression, more details and the related
mechanisms need to be uncovered.
Fig. 2. Schematic of targeted m6
A editors and readers.
Targeted m6
A editors or readers have been developed by fusing m6
A writers,
erasers, or readers to dCas13b/dCas9. The fusion proteins can target the mRNAs
of interest with the help of gRNA and regulate their metabolism.
B. Han et al.
Cancer Letters 518 (2021) 256–265
259
Table 1
Functional characterization of YTH domain-containing proteins in cancers.
m6
readers
Cancer Expression Targets and Mechanism Role Reference
YTHDF1 Breast cancer Upregulated Not mentioned. Positive prognostic signature [37]
Upregulated Positive associated with CDK1,
MKI67, VEGFA.
Positive prognostic signature [38]
Colorectal cancer Upregulated Enhances TCF7L2 translation. Oncogene [39]
Upregulated Increases Wnt/β-catenin activity. Oncogene [40]
Upregulated Not mentioned. Oncogene [41]
Downregulated Not mentioned. Negative prognostic signature [42]
Unknown Facilitates ANKLE1 expression. Tumor suppressor [43]
Gastric cancer Unaffected Not mentioned. Tumor suppressive signature [44]
Upregulated Not mentioned. Positive prognostic signature [45]
Hepatocellular
carcinoma
Upregulated Not mentioned. Oncogene [46]
Upregulated Not mentioned. Oncogene [47]
Upregulated Promotes translation of Snail. Oncogene [48]
Upregulated Promotes FZD5 mRNA translation. Oncogene [49]
Unknown Increases the stability of FOXO3
mRNA.
Oncogene [50]
Lung cancer Upregulated Promotes YAP mRNA translation. Oncogene [51,52]
Upregulated Promotes PRPF6 mRNA expression. Oncogene [53]
Upregulated Targets CDKs and Keap1-Nrf2-
AKR1C1 axis
Dual effect [54]
Upregulated Positive prognostic signature [55]
Upregulated in tumors but downregulated in
higher pathological stages
Not mentioned. Dual effect [56]
Upregulated Disrupts the Wnt/b-catenin pathway. Positive therapeutic target [57]
Melanoma Unknown Promotes HINT2 translation. Oncogene [58]
Upregulated Interactes with CDK1/2. Positive therapeutic target [59]
Ovarian cancer Upregulated Augments EIF3C translation. Oncogene [60]
Unaffected Promotes TRIM29 translation. Oncogene [61]
Cervical cancer Unknown Induces PDK4 expression. Positive therapeutic target [62]
Upregulated Enhances HK2 stability. Positive therapeutic target [63]
Squamous cell
carcinoma
Upregulated Not mentioned. Positive prognostic signature [64]
Upregulated Promotes c-Myc stability. Oncogene [65]
Upregulated Enhances TFRC expression. Positive therapeutic target [66]
Merkel Cell Carcinoma Upregulated Activates eIF3 translation. Oncogene [67]
Abdominal aortic
aneurysm
Upregulated Not mentioned. Unknown [68]
Glioma Upregulated Not mentioned. Positive prognostic signature [69]
Upregulated Not mentioned. Positive prognostic signature [70]
YTHDF2 Bladder cancer Upregulated Promotes SETD7, KLF4 degradation. Oncogene [71]
Cervical cancer Unknown Mediates GAS5 RNA degradation. Potential therapeutic target [72]
Colorectal cancer Unaffected Promotes SOX4 mRNA degradation. Potential therapeutic target [73]
Gastric cancer Downregulated Promotes FOXC2 degradation. Negative prognostic signature [74]
Glioblastoma Upregulated Stabilizes MYC, VEGFA transcripts. Potential therapeutic target [75]
Upregulated Positively correlated with PD-1, TIM-
3 and CTLA-4.
Positive prognostic signature [76]
Upregulated Facilitates LXRA, HIVEP2 mRNA
decay.
Potential prognostic signature [77]
Hepatocellular
carcinoma
Downregulated Proceses IL11, SERPINE2 mRNA
dacay.
Pptential therapeutic target [78]
Downregulated Destabilizing EGFR mRNA. Tumor suppressor [79]
Unknown Mediates SOCS2 mRNA degradation. Potential therapeutic target [80]
Upregulated Not mentioned. Positive prognostic signature [81]
Upregulated Increases OCT4 translation. Potential therapeutic target [82]
Acute myeloid
leukemia
Upregulated Destabilizes TNFRSF1B mRNA. Potential therapeutic target [83]
Unknown Reduces PFKP, LDHB expression. Negative prognostic signature [84]
Lung cancer Upregulated Facilitates 6PGD mRNA translation. Potential prognostic signature [85]
Ovarian cancer Upregulated Inversely correlated with miR-145. Positive therapeutic target [86]
Pancreatic cancer Unknown Promotes PER1 mRNA degradation. Potential diagnostic and
Prostate cancer Upregulated Facilitates MOB3B mRNA
degradation.
Potential therapeutic target [88]
Upregulated Not mentioned. Positive therapeutic target [89]
Upregulated Induces LHPP, NKX3-1 mRNA
degradation.
Potential diagnostic and
therapeutic target
YTHDF3 Breast cancer Upregulated Positive associated with CDK1,
MKI67, VEGFA.
Positive prognostic signature [38]
Upregulated Induces ST6GALNAC5, GJA1
translation.
Potential prognostic signature [91]
Colorectal cancer Upregulated Facilitates GAS5 degradation. Potential prognostic signature [92]
Hepatocellular
carcinoma
Unknown Enhancing Zeb1 mRNA stability. Potential therapeutic target [93]
YTHDC1 Colorectal cancer Upregulated Not mentioned. Positive therapeutic target [94]
Glioblastoma Unaffected Promotes SRSF decay. Potential therapeutic target [95]
(continued on next page)
B. Han et al.
Cancer Letters 518 (2021) 256–265
7. YTH proteins in liver cancer
Hepatocellular carcinoma (HCC) is the most common type of pri￾mary liver cancer [108]. The high prevalence of HCC has long been
attributed to chronic viral hepatitis, while other risk factors, particularly
genetic or epigenetic susceptibility, are gaining importance. Studies
have shown that HCC is highly associated with abnormal m6
A deposi￾tion [80,109]. Interestingly, m6
A modification in these studies showed
quite different effects on HCC progression: METTL3 promoted HCC via
m6
A modification, but METTL14 was an adverse prognostic factor in
HCC patients. Thus, the final outcome of m6
A modification in HCC could
be determined by assessing m6
A-containing mRNAs and their readers.
Recently, a correlation analysis using the TCGA database showed
that YTHDF1 is significantly overexpressed in HCC and positively
associated with pathology stage, implying that YTHDF1 is a potential
new therapeutic and prognostic marker in HCC [46]. Another similar
study revealed the independent predictive value of both YTHDF1 and
METTL3 for HCC patient overall survival [47]. In addition, in vitro and
in vivo evidence indicated that YTHDF1 induces the progression of
migration, invasion and epithelial-mesenchymal transition (EMT) in
HCC cells by regulating Snail mRNA translation [48]. In addition, Wnt
receptor-FZD5 is another YTHDF1 target at the translational level in
HCC. YTHDF1 promotes HCC cell proliferation and metastasis by
accelerating the translational output of FZD5 mRNA in an m6
A-de￾pendent manner [49]. For HCC therapy, resistance to sorafenib (a
first-line treatment for advanced HCC) remains a problem in developing
individual therapeutic strategies. YTHDF1 was demonstrated to have an
important role in modifying the hypoxic tumor environment by identi￾fying FOXO3 mRNA. This study validated that METTL3 mediates and
that YTHDF1 recognizes FOXO3 methylation, leading to inhibition of the
autophagy signaling pathway to maintain sorafenib sensitivity in HCC
[110]. Therefore, YTHDF1 may act as an oncogene and has the potential
to serve as a positive molecular biomarker for evaluating the prognosis
and treatment response of HCC patients. As a synergy factor of YTHDF1
in protein synthesis, YTHDF3 enhances the stability and lifetime of
m6
A-methylated Zeb1 mRNA. Upregulated Zeb1 mediates circ_K￾IAA1429 expression, leading to a robust driving force for HCC migra￾tion, invasion and EMT [93].
However, the performance of YTHDF2 in HCC is more complicated,
as shown above. YTHDF2 can work as both a molecular ‘rheostat’ and an
‘accelerator’, which depends on the mRNAs it processes. When its binds
to interleukin 11 (IL11)/serpin family E member 2 (SERPINE2) or EGFR,
YTHDF2 may act as a tumor suppressor [78,79]. In contrast, when
YTHDF2 recognizes OCT4 mRNA, it promotes HCC development and
cancer metastasis [82]. In addition, there are several other studies
showing that YTHDF2 has the potential to participate in HCC-related
phenotypes, such as proliferation and migration [80] and immune cell
infiltration [81], but further exploration is needed to determine the
specific regulatory mechanisms.
8. YTH proteins in lung cancer
Lung cancer is a molecularly heterogeneous disease [111]. Under￾standing the molecular biology of lung cancer is helpful for finding
promising strategies for early prognosis and treatment. Lung cancer is
classified into two types: NSCLC and small-cell lung cancer (SCLC).
NSCLC is the most common type, of which lung adenocarcinoma (LUAD)
is the most common subtype. Recently, METTL3 was identified as a
potential therapeutic target for patients with lung cancer as it promotes
the translation of oncogenes [112,113]. The functions of m6
A readers in
lung cancer remain largely unknown; the possible functions are dis￾cussed below.
The YAP signaling pathway plays a critical role in lung cancer,
including in tumorigenesis, aggressiveness, metastasis, and resistance to
drug treatment [114]. As a central component of the YAP signaling
pathway, YTHDF1 is recruited to m6
A-modified YAP mRNA, inducing
NSCLC drug resistance and metastasis by promoting YAP translation
[51,52]. Another m6
A target, PRPF6, screened by LUAD TCGA dataset
analysis, was shown to be positively expressed with YTHDF1. In this
study, the authors found that YTHDF1-dependent PRPF6 m6
A methyl￾ation is a key regulator of ATTM-induced anticancer effects. The
mechanism mediated by the m6
A-PRPF6-YTHDF1 axis indicates an op￾portunity for overcoming the side effects caused by ATTM therapy by
scavenging H2S [53]. Consistently, according to different datasets from
the TCGA and Gene Expression Omnibus (GEO), YTHDF1 is overex￾pressed in LUAD patients versus normal controls [115]. In addition,
YTHDF1, together with 5 other m6
A-related genes, was screened to build
a risk scoring signature that was strongly related to pathological stage,
sex and overall survival, indicating that YTHDF1 has good predictive
value in LAUD [56]. Additionally, m6
A modification was found to
participate in lung cancer cell metabolism via its reader YTHDF2 [85].
In this study, upregulated YTHDF2 bound to 6-phosphogluconate dehy￾drogenase (6PGD) and promoted 6PGD mRNA translation, indicating
that YTHDF2 is a lung cancer promoter. IGF2BPs are also detected
abnormally upregulated in LAUD tissue [103]. After irradiation, m6
level of VANGL1 is upregulated, as well as the VANGL1 mRNA stability
regulated by IGF2BP2/3, suggesting a regulatory role of IGF2BPs in
LUAD radio resistance [104].
Resistance to hypoxia-induced apoptosis, leading to distinctive
hypoxia adaption in de novo lung adenocarcinomas (ADCs), has been an
inevitable barrier leading to poor clinical outcomes of NSCLC treatment.
The search for more specific hallmarks and treatments in both ADC and
hypoxia-adapted NSCLC has become necessary and urgent. In the two
different progressions of NSCLC, YTHDF1 behaves in completely distinct
manners and provides us with new insights into cancer biology [54]. In
ADC, YTHDF1 deficiency impedes cancer progression by inhibiting
NSCLC cell proliferation and xenograft tumor formation through regu￾lating the translation activity of cyclin proteins. However, lower
expression of YTHDF1 is correlated with a worse clinical outcome
Table 1 (continued )
m6
readers
Cancer Expression Targets and Mechanism Role Reference
Hepatocellular
carcinoma
Upregulated Not mentioned. Positive prognostic target [96]
Prostate cancer Unknown Mediates Cd44v5-Luc splicing. Positive therapeutic target
YTHDC2 Colon cancer Upregulated Promotes translation of HIF-1α and
Twist1.
Potential prognostic signature [98]
Lung adenocarcinoma Downregulated Promotes SLC7A11 mRNA decay. Negative prognostic signature
Negative prognostic signature
[99]
Downregulated Not mentioned. [100]
IGF2BPs Breast cancer Unknown Promotes CERS6 mRNA stability. Potential therapeutic
signature
Gastric cancer Upregulated Promotes HDGF mRNA stability. Potential prognostic
biomarker
Lung cancer Upregulated Not mentioned. Positive prognostic signature [103]
Unknown Enhances VANGL1 mRNA stability. Potential therapeutic target [104]
Colorectal cancer Upregulated Prevents SOX2 mRNA degradation. Potential biomarker
B. Han et al.
Cancer Letters 518 (2021) 256–265
261
because of the resistance to cisplatin treatment in cancerous cells.
Depletion of YTHDF1 in hypoxic solid tumors makes cancerous cells
more resistant to cisplatin-dependent chemotherapy by regulating the
Keap1-Nrf2-AKR1C1 axis. In contrast, YTHDC2 is frequently suppressed
in LUAD [99,100]. Mouse model studies have shown that YTHDC2
preferentially binds to SLC7A11 mRNA and decreases tumorigenesis by
suppressing cystine uptake and blocking the downstream antioxidant
program [99].
9. YTH proteins in other cancers
The mRNAs recognized by YTH domain-containing proteins largely
determine their roles in the progression of specific cancers. In oral
squamous cell carcinoma, c-Myc is a direct YTHDF1 target gene and is
responsible for the acceleration of tumor growth [65]. The negative p53
regulators YY1 and MDM2 are targets stimulated by YTHDF2 to promote
human keratinocyte transformation in arsenic carcinogenesis [116]. In
ocular melanoma, YTHDF1 inhibits the progression of both uveal and
Fig. 3. Deregulation of m6
A reader proteins in human cancers.
A comprehensive overview of m6
A readers in human carcinogenesis, including proliferation, migration, invasion, metastasis, and chemoresistance regulation. These
readers specifically identify m6
A-modified mRNAs and subsequently regulate critical signaling pathways in the pathogenesis of cancers. Red box line indicates
upregulated expression and oncogenic functions. Blue line indicates downregulated expression and tumor suppresive functions. Black line indicates contradicted
roles within different studies. Dashed gray line indicates unaffected or unknown roles.
B. Han et al.
Cancer Letters 518 (2021) 256–265
262
conjunctival melanoma by promoting the translation of the tumor sup￾pressor HINT2 [58]. Notably, in addition to being recognized by
YTHDF3 in CRC, the tumor suppressor GAS is also identified by YTHDF2
in cervical cancer and acts as a critical molecule for cervical cancer
progression [72]. YTHDF2 also binds to FOXC2, TNFRSF1B, PER1, and
MOB3B in gastric cancer, AML, pancreatic cancer and prostate cancer,
respectively, providing similar insights into the underlying mechanisms
of carcinogenesis induced by RNA degradation [74,83,87,88]. In glio￾blastoma (GBM), despite different target transcripts, YTHDF1/2 and
YTHDC1 display similar function on GBM growth and progression,
indicating positive prognostic and therapeutic prospects of these readers
[69,70,75–77,95].
Studies have also indicated that more than one individual transcript
participates in m6
A reader-mediated effects in cancers. In ovarian cancer
and Merkel cell carcinoma, YTHDF1 augments m6
A-modified EIF3C
translation and concomitantly increases the global translational output,
thus facilitating tumorigenesis and cancer metastasis [60,67]. Addi￾tionally, YTHDF1 has been verified to bind to m6
A-modified PDK4 or
HK2 and promote cancer cell metabolic processes, such as glycolysis or
the Warburg effect in cervical cancer, which suggests that YTHDF1
could be a promising therapeutic target [62,63]. Similarly, a group of
transcripts encoding lysosomal proteases in dendritic cells are methyl￾ated and then recognized by YTHDF1. Deletion of YTHDF1 markedly
inhibits these cathepsins, thus enhancing the antitumor response of
antigen-specific CD8+ T cells [117]. In bladder cancer, SETD7 and KLF4
were both identified as direct targets of YTHDF2 through transcriptome
sequencing and confirmed with methylated RNA immunoprecipitation
(MeRIP)-RT-qPCR [71].
In addition, other studies have indicated a positive correlation be￾tween YTHDF1 expression and cancer development, but there is a lack of
mechanistic evidence in abdominal aortic aneurysm [118] and head and
neck squamous cell carcinoma [119]. Likewise, low expression of
YTHDC2 is significantly associated with worse overall survival in lung
cancer patients. However, the potential RNAs that interact with
YTHDC2 still need to be explored [100]. Further research is required to
decipher the specific targets of m6
A readers in these cancers, which may
contribute to the understanding of their clinical significance and po￾tential applications.
10. Conclusions and future perspectives
In this review, we summarized nearly all the recent findings on YTH
domain-containing proteins in cancers. Dysregulation of m6
A readers in
cancer tissues results in abnormal mRNA metabolism of oncogenes and
tumor suppressors, leading to the acceleration or delay of cancer
development (Fig. 3). However, our understanding of how YTH proteins
contribute to these processes remains incomplete. It is essential to
identify the intrinsic and extrinsic signals that regulate the recruitment
of YTH proteins to m6
A-modified mRNAs and to identify these tran￾scripts in a specific biological environment. In addition, the mechanisms
that control the expression and activities of YTH proteins remain largely
unknown. Therefore, future elucidation of the accurate roles of YTH
proteins in regulating gene expression in cancers with new tools and
methods is needed.
The crucial role of m6
A readers in cancer initiation and progression
provides potential targets for the treatment of cancers. Indeed, inhibi￾tion of YTHDF1 showed therapeutic potential alone or in combination
with anti-PD-L1 immunotherapy in CRC [39,117]. However,
small-molecule agents targeting YTH proteins, by blocking their inter￾action with m6
A-modified mRNAs or other regulatory proteins, remain
to be identified or developed. These small molecules might serve as a
potential way to inhibit dysregulated mRNA metabolism by YTH pro￾teins in cancer. On the other hand, targeted m6
A editors and readers
based on CRISPR/dCas system have been recently developed [30–33].
Taking advantage of these tools, manipulating the oncogenic or tumor
suppressive mRNAs of interest with specific editors or readers could be
achieved to modulate cancer cell characteristics. Of note, Li et al. have
used dCas13b-ALKBH5 to demethylate m6
A modifications on oncogene
transcripts such as EGFR and MYC, resulting in altered cancer cell pro￾liferation in vitro [31]. However, whether these tools could be applied to
cancer treatment remains to be explored.
Author contributions
All the authors summerized and discussed. B.H. and X.G. wrote the
manuscript.
Declaration of competing interest
The authors declare that they have no conflict of interest.
Acknowledgements
This work was supported by grants from National Natural Science
Foundation of China (82073110 and 81672847 to X.G.), Zhejiang Youth
Talent Support Program (ZJWR0308085 to X.G.), Zhejiang Provincial
Natural Science Foundation of China (LQ19C050004 to S.W.), and
Guangdong Provincial Science and Technology Project
(2017A020214008).
References
[1] R. Desrosiers, K. Friderici, F. Rottman, Identification of methylated nucleosides in
messenger RNA from Novikoff hepatoma cells, Proc. Natl. Acad. Sci. U.S.A. 71
(1974) 3971–3975.
[2] C.M. Wei, A. Gershowitz, B. Moss, Methylated nucleotides block 5’ terminus of
HeLa cell messenger RNA, Cell 4 (1975) 379–386.
[3] J.M. Adams, S. Cory, Modified nucleosides and bizarre 5′
-termini in mouse
myeloma mRNA, Nature 255 (1975) 28–33.
[4] K.D. Meyer, Y. Saletore, P. Zumbo, O. Elemento, C.E. Mason, S.R. Jaffrey,
Comprehensive analysis of mRNA methylation reveals enrichment in 3’ UTRs and
near stop codons, Cell 149 (2012) 1635–1646.
[5] D. Dominissini, S. Moshitch-Moshkovitz, S. Schwartz, M. Salmon-Divon, L. Ungar,
S. Osenberg, K. Cesarkas, J. Jacob-Hirsch, N. Amariglio, M. Kupiec, R. Sorek,
G. Rechavi, Topology of the human and mouse m6A RNA methylomes revealed
by m6A-seq, Nature 485 (2012) 201–206.
[6] B. Linder, A.V. Grozhik, A.O. Olarerin-George, C. Meydan, C.E. Mason, S.
R. Jaffrey, Single-nucleotide-resolution mapping of m6A and m6Am throughout
the transcriptome, Nat. Methods 12 (2015) 767–772.
[7] G. Jia, Y. Fu, X. Zhao, Q. Dai, G. Zheng, Y. Yang, C. Yi, T. Lindahl, T. Pan, Y.
G. Yang, C. He, N6-methyladenosine in nuclear RNA is a major substrate of the
obesity-associated FTO, Nat. Chem. Biol. 7 (2011) 885–887.
[8] Y. Fu, D. Dominissini, G. Rechavi, C. He, Gene expression regulation mediated
through reversible m(6)A RNA methylation, Nat. Rev. Genet. 15 (2014) 293–306.
[9] G. Zheng, J.A. Dahl, Y. Niu, P. Fedorcsak, C.M. Huang, C.J. Li, C.B. Vagbo, Y. Shi,
W.L. Wang, S.H. Song, Z. Lu, R.P. Bosmans, Q. Dai, Y.J. Hao, X. Yang, W.M. Zhao,
W.M. Tong, X.J. Wang, F. Bogdan, K. Furu, Y. Fu, G. Jia, X. Zhao, J. Liu, H.
E. Krokan, A. Klungland, Y.G. Yang, C. He, ALKBH5 is a mammalian RNA
demethylase that impacts RNA metabolism and mouse fertility, Mol. Cell. 49
(2013) 18–29.
[10] T. Lence, C. Paolantoni, L. Worpenberg, J.Y. Roignant, Mechanistic insights into
m(6)A RNA enzymes, Biochim. Biophys. Acta Gene Regul. Mech. 1862 (2019)
222–229.
[11] I.A. Roundtree, M.E. Evans, T. Pan, C. He, Dynamic RNA modifications in gene
expression regulation, Cell 169 (2017) 1187–1200.
[12] B.S. Zhao, I.A. Roundtree, C. He, Post-transcriptional gene regulation by mRNA
modifications, Nat. Rev. Mol. Cell Biol. 18 (2017) 31–42.
[13] C. Roost, S.R. Lynch, P.J. Batista, K. Qu, H.Y. Chang, E.T. Kool, Structure and
thermodynamics of N6-methyladenosine in RNA: a spring-loaded base
modification, J. Am. Chem. Soc. 137 (2015) 2107–2115.
[14] H. Huang, H. Weng, W. Sun, X. Qin, H. Shi, H. Wu, B.S. Zhao, A. Mesquita, C. Liu,
C.L. Yuan, Y.C. Hu, S. Huttelmaier, J.R. Skibbe, R. Su, X. Deng, L. Dong, M. Sun,
C. Li, S. Nachtergaele, Y. Wang, C. Hu, K. Ferchen, K.D. Greis, X. Jiang, M. Wei,
L. Qu, J.L. Guan, C. He, J. Yang, J. Chen, Recognition of RNA N(6)-
methyladenosine by IGF2BP proteins enhances mRNA stability and translation,
Nat. Cell Biol. 20 (2018) 285–295.
[15] R.R. Edupuganti, S. Geiger, R.G.H. Lindeboom, H. Shi, P.J. Hsu, Z. Lu, S.Y. Wang,
M.P.A. Baltissen, P. Jansen, M. Rossa, M. Muller, H.G. Stunnenberg, C. He,
T. Carell, M. Vermeulen, N(6)-methyladenosine (m(6)A) recruits and repels
proteins to regulate mRNA homeostasis, Nat. Struct. Mol. Biol. 24 (2017)
870–878.
[16] N. Liu, K.I. Zhou, M. Parisien, Q. Dai, L. Diatchenko, T. Pan, N6-methyladenosine
alters RNA structure to regulate binding of a low-complexity protein, Nucleic
Acids Res. 45 (2017) 6051–6063.
B. Han et al.
Cancer Letters 518 (2021) 256–265
263
[17] C.R. Alarcon, H. Goodarzi, H. Lee, X. Liu, S. Tavazoie, S.F. Tavazoie, HNRNPA2B1
is a mediator of m(6)a-dependent nuclear RNA processing events, Cell 162 (2015)
1299–1308.
[18] D. Theler, C. Dominguez, M. Blatter, J. Boudet, F.H. Allain, Solution structure of
the YTH domain in complex with N6-methyladenosine RNA: a reader of
methylated RNA, Nucleic Acids Res. 42 (2014) 13911–13919.
[19] X. Wang, B.S. Zhao, I.A. Roundtree, Z. Lu, D. Han, H. Ma, X. Weng, K. Chen,
H. Shi, C. He, N(6)-methyladenosine modulates messenger RNA translation
efficiency, Cell 161 (2015) 1388–1399.
[20] X. Wang, Z. Lu, A. Gomez, G.C. Hon, Y. Yue, D. Han, Y. Fu, M. Parisien, Q. Dai,
G. Jia, B. Ren, T. Pan, C. He, N6-methyladenosine-dependent regulation of
messenger RNA stability, Nature 505 (2014) 117–120.
[21] H. Shi, X. Wang, Z. Lu, B.S. Zhao, H. Ma, P.J. Hsu, C. Liu, C. He, YTHDF3
facilitates translation and decay of N(6)-methyladenosine-modified RNA, Cell
Res. 27 (2017) 315–328.
[22] A. Li, Y.S. Chen, X.L. Ping, X. Yang, W. Xiao, Y. Yang, H.Y. Sun, Q. Zhu, P. Baidya,
X. Wang, D.P. Bhattarai, Y.L. Zhao, B.F. Sun, Y.G. Yang, Cytoplasmic m(6)A
reader YTHDF3 promotes mRNA translation, Cell Res. 27 (2017) 444–447.
[23] P.J. Hsu, Y. Zhu, H. Ma, Y. Guo, X. Shi, Y. Liu, M. Qi, Z. Lu, H. Shi, J. Wang,
Y. Cheng, G. Luo, Q. Dai, M. Liu, X. Guo, J. Sha, B. Shen, C. He, Ythdc2 is an N(6)-
methyladenosine binding protein that regulates mammalian spermatogenesis,
Cell Res. 27 (2017) 1115–1127.
[24] J. Kretschmer, H. Rao, P. Hackert, K.E. Sloan, C. Hobartner, ¨ M.T. Bohnsack, The
m6A reader protein YTHDC2 interacts with the small ribosomal subunit and the
–3′ exoribonuclease XRN1, RNA 24 (2018) 1339–1350.
[25] C. Xu, X. Wang, K. Liu, I.A. Roundtree, W. Tempel, Y. Li, Z. Lu, C. He, J. Min,
Structural basis for selective binding of m6A RNA by the YTHDC1 YTH domain,
Nat. Chem. Biol. 10 (2014) 927–929.
[26] W. Xiao, S. Adhikari, U. Dahal, Y.S. Chen, Y.J. Hao, B.F. Sun, H.Y. Sun, A. Li, X.
L. Ping, W.Y. Lai, X. Wang, H.L. Ma, C.M. Huang, Y. Yang, N. Huang, G.B. Jiang,
H.L. Wang, Q. Zhou, X.J. Wang, Y.L. Zhao, Y.G. Yang, Nuclear m(6)A reader
YTHDC1 regulates mRNA splicing, Mol. Cell. 61 (2016) 507–519.
[27] I.A. Roundtree, G.Z. Luo, Z. Zhang, X. Wang, T. Zhou, Y. Cui, J. Sha, X. Huang,
L. Guerrero, P. Xie, E. He, B. Shen, C. He, YTHDC1 mediates nuclear export of N
(6)-methyladenosine methylated mRNAs, Elife 6 (2017) e31311.
[28] N. Liu, Q. Dai, G. Zheng, C. He, M. Parisien, T. Pan, N(6)-methyladenosine￾dependent RNA structural switches regulate RNA-protein interactions, Nature
518 (2015) 560–564.
[29] K.I. Zhou, H. Shi, R. Lyu, A.C. Wylder, Z. Matuszek, J.N. Pan, C. He, M. Parisien,
T. Pan, Regulation of Co-transcriptional pre-mRNA splicing by m(6)A through the
low-complexity protein hnRNPG, Mol. Cell. 76 (2019) 70–81.
[30] X.M. Liu, J. Zhou, Y. Mao, Q. Ji, S.B. Qian, Programmable RNA N(6)-
methyladenosine editing by CRISPR-Cas9 conjugates, Nat. Chem. Biol. 15 (2019)
865–871.
[31] J. Li, Z. Chen, F. Chen, G. Xie, Y. Ling, Y. Peng, Y. Lin, N. Luo, C.M. Chiang,
H. Wang, Targeted mRNA demethylation using an engineered dCas13b-ALKBH5
fusion protein, Nucleic Acids Res. 48 (2020) 5684–5694.
[32] C. Wilson, P.J. Chen, Z. Miao, D.R. Liu, Programmable m(6)A modification of
cellular RNAs with a Cas13-directed methyltransferase, Nat. Biotechnol. 38
(2020) 1431–1440.
[33] S. Rauch, C. He, B.C. Dickinson, Targeted m(6)A reader proteins to study
epitranscriptomic regulation of single RNAs, J. Am. Chem. Soc. 140 (2018)
11974–11981.
[34] X. Deng, R. Su, H. Weng, H. Huang, Z. Li, J. Chen, RNA N(6)-methyladenosine
modification in cancers: current status and perspectives, Cell Res. 28 (2018)
507–517.
[35] H. Huang, H. Weng, J. Chen, m(6)A modification in coding and non-coding RNAs:
roles and therapeutic implications in cancer, Canc. Cell 37 (2020) 270–288.
[36] W. Zhao, X. Qi, L. Liu, S. Ma, J. Liu, J. Wu, Epigenetic regulation of m(6)A
modifications in human cancer, Mol. Ther. Nucleic Acids 19 (2020) 405–412.
[37] L. Liu, X. Liu, Z. Dong, J. Li, Y. Yu, X. Chen, F. Ren, G. Cui, R. Sun, N6-
methyladenosine-related genomic targets are altered in breast cancer tissue and
associated with poor survival, J. Canc. 10 (2019) 5447–5459.
[38] R. Anita, A. Paramasivam, J.V. Priyadharsini, S. Chitra, The m6A readers YTHDF1
and YTHDF3 aberrations associated with metastasis and predict poor prognosis in
breast cancer patients,, Am. J. Canc. Res. 10 (2020) 2546–2554.
[39] B. Han, S. Yan, S. Wei, J. Xiang, K. Liu, Z. Chen, R. Bai, J. Sheng, Z. Xu, X. Gao,
YTHDF1-mediated translation amplifies Wnt-driven intestinal stemness, EMBO
Rep. 21 (2020) e49229.
[40] Y. Bai, C. Yang, R. Wu, L. Huang, S. Song, W. Li, P. Yan, C. Lin, D. Li, Y. Zhang,
YTHDF1 regulates tumorigenicity and cancer stem cell-like activity in human
colorectal carcinoma, Front. Oncol. 9 (2019) 332.
[41] Y. Nishizawa, M. Konno, A. Asai, J. Koseki, K. Kawamoto, N. Miyoshi,
H. Takahashi, N. Nishida, N. Haraguchi, D. Sakai, T. Kudo, T. Hata, C. Matsuda,
T. Mizushima, T. Satoh, Y. Doki, M. Mori, H. Ishii, Oncogene c-Myc promotes
epitranscriptome m6A reader YTHDF1 expression in colorectal cancer,
Oncotarget 9 (2017) 7476–7486.
[42] T. Liu, C. Li, L. Jin, C. Li, L. Wang, The prognostic value of m6A RNA methylation
regulators in colon adenocarcinoma,, Med. Sci. Mon. Int. Med. J. Exp. Clin. Res.
25 (2019) 9435–9445.
[43] J. Tian, P. Ying, J. Ke, Y. Zhu, Y. Yang, Y. Gong, D. Zou, X. Peng, N. Yang,
X. Wang, S. Mei, Y. Zhang, C. Wang, R. Zhong, J. Chang, X. Miao, ANKLE1 N(6)
-Methyladenosine-related variant is associated with colorectal cancer risk by
maintaining the genomic stability, Int. J. Canc. 146 (2020) 3281–3293.
[44] C. Zhang, M. Zhang, S. Ge, W. Huang, X. Lin, J. Gao, J. Gong, L. Shen, Reduced
m6A modification predicts malignant phenotypes and augmented Wnt/PI3K-Akt
signaling in gastric cancer, Canc. Med. 8 (2019) 4766–4781.
[45] T. Liu, S. Yang, Y.P. Cheng, X.L. Kong, D.D. Du, X. Wang, Y.F. Bai, L.H. Yin, Y.
P. Pu, G.Y. Liang, The N6-methyladenosine (m6A) methylation gene YTHDF1
reveals a potential diagnostic role for gastric cancer,, Canc. Manag. Res. 12
(2020) 11953–11964.
[46] X. Zhao, Y. Chen, Q. Mao, X. Jiang, W. Jiang, J. Chen, W. Xu, L. Zhong, X. Sun,
Overexpression of YTHDF1 is associated with poor prognosis in patients with
hepatocellular carcinoma, Canc. Biomarkers 21 (2018) 859–868.
[47] Y. Zhou, Z. Yin, B. Hou, M. Yu, R. Chen, H. Jin, Z. Jian, Expression profiles and
prognostic significance of RNA N6-methyladenosine-related genes in patients
with hepatocellular carcinoma: evidence from independent datasets, Canc.
Manag. Res. 11 (2019) 3921–3931.
[48] X. Lin, G. Chai, Y. Wu, J. Li, F. Chen, J. Liu, G. Luo, J. Tauler, J. Du, S. Lin, C. He,
H. Wang, RNA m(6)A methylation regulates the epithelial mesenchymal
transition of cancer cells and translation of Snail, Nat. Commun. 10 (2019) 2065.
[49] X. Liu, J. Qin, T. Gao, C. Li, B. He, B. Pan, X. Xu, X. Chen, K. Zeng, M. Xu, C. Zhu,
Y. Pan, H. Sun, L. Sun, T. Xu, S. Wang, YTHDF1 facilitates the progression of
hepatocellular carcinoma by promoting FZD5 mRNA translation in an m6A￾dependent manner, Mol. Ther. Nucleic Acids 22 (2020) 750–765.
[50] Z. Lin, Y. Niu, A. Wan, D. Chen, H. Liang, X. Chen, L. Sun, S. Zhan, L. Chen,
C. Cheng, X. Zhang, X. Bu, W. He, G. Wan, RNA m(6) A methylation regulates
sorafenib resistance in liver cancer through FOXO3-mediated autophagy, EMBO
J. 39 (12) (2020) e103181.
[51] D. Jin, J. Guo, Y. Wu, J. Du, L. Yang, X. Wang, W. Di, B. Hu, J. An, L. Kong, L. Pan,
G. Su, m(6)A mRNA methylation initiated by METTL3 directly promotes YAP
translation and increases YAP activity by regulating the MALAT1-miR-1914-3p￾YAP axis to induce NSCLC drug resistance and metastasis, J. Hematol. Oncol. 12
(2019) 135.
[52] D. Jin, J. Guo, Y. Wu, L. Yang, X. Wang, J. Du, J. Dai, W. Chen, K. Gong, S. Miao,
X. Li, H. Sun, m(6)A demethylase ALKBH5 inhibits tumor growth and metastasis
by reducing YTHDFs-mediated YAP expression and inhibiting miR-107/LATS2-
mediated YAP activity in NSCLC, Mol. Canc. 19 (2020) 40.
[53] X. Li, N. Li, L. Huang, S. Xu, X. Zheng, A. Hamsath, M. Zhang, L. Dai, H. Zhang, J.
J. Wong, M. Xian, C.T. Yang, J. Liu, Is hydrogen sulfide a concern during
treatment of lung adenocarcinoma with ammonium tetrathiomolybdate? Front.
Oncol. 10 (2020) 234.
[54] Y. Shi, S. Fan, M. Wu, Z. Zuo, X. Li, L. Jiang, Q. Shen, P. Xu, L. Zeng, Y. Zhou,
Y. Huang, Z. Yang, J. Zhou, J. Gao, H. Zhou, S. Xu, H. Ji, P. Shi, D.D. Wu, C. Yang,
Y. Chen, YTHDF1 links hypoxia adaptation and non-small cell lung cancer
progression, Nat. Commun. 10 (2019) 4892.
[55] Y. Zhang, X. Liu, L. Liu, J. Li, Q. Hu, R. Sun, Expression, Prognostic Significance,
Of m6A-related genes in lung adenocarcinoma, Med. Sci. Mon. Int. Med. J. Exp.
Clin. Res. 26 (2020) e919644.
[56] J. Zhu, M. Wang, D. Hu, Deciphering N(6)-methyladenosine-related genes
signature to predict survival in lung adenocarcinoma, BioMed Res. Int. 2020
(2020) 2514230.
[57] J. Zhou, D. Xiao, T. Qiu, J. Li, Z. Liu, Loading MicroRNA-376c in extracellular
vesicles inhibits properties of non-small cell lung cancer cells by targeting
YTHDF1, Technol. Canc. Res. Treat. 19 (2020), 1533033820977525.
[58] R. Jia, P. Chai, S. Wang, B. Sun, Y. Xu, Y. Yang, S. Ge, R. Jia, Y.G. Yang, X. Fan, m
(6)A modification suppresses ocular melanoma through modulating HINT2
mRNA translation, Mol. Canc. 18 (2019) 161.
[59] T. Li, M. Gu, A. Deng, C. Qian, Increased expression of YTHDF1 and HNRNPA2B1
as potent biomarkers for melanoma: a systematic analysis, Canc. Cell Int. 20
(2020) 239.
[60] T. Liu, Q. Wei, J. Jin, Q. Luo, Y. Liu, Y. Yang, C. Cheng, L. Li, J. Pi, Y. Si, H. Xiao,
L. Li, S. Rao, F. Wang, J. Yu, J. Yu, D. Zou, P. Yi, The m6A reader YTHDF1
promotes ovarian cancer progression via augmenting EIF3C translation,, Nucleic
Acids Res. 48 (2020) 3816–3831.
[61] L. Hao, J.M. Wang, B.Q. Liu, J. Yan, C. Li, J.Y. Jiang, F.Y. Zhao, H.Y. Qiao, H.
Q. Wang, m6A-YTHDF1-mediated TRIM29 upregulation facilitates the stem cell￾like phenotype of cisplatin-resistant ovarian cancer cells, Biochim. Biophys. Acta
Mol. Cell Res. 1868 (2021) 118878.
[62] Z. Li, Y. Peng, J. Li, Z. Chen, F. Chen, J. Tu, S. Lin, H. Wang, N6-methyladenosine
regulates glycolysis of cancer cells through PDK4, Nat. Commun. 11 (2020) 2578.
[63] Q. Wang, X. Guo, L. Li, Z. Gao, X. Su, M. Ji, J. Liu, N6-methyladenosine METTL3
promotes cervical cancer tumorigenesis and Warburg effect through YTHDF1/
HK2 modification, Cell Death Dis. 11 (2020) 911.
[64] L.C. Xinyuan Zhao, Development and validation of a m6A RNA methylation
regulators-based signature for predicting the prognosis of head and neck
squamous cell carcinoma, Am. J. Canc. Res. 9 (2019) 14.
[65] W. Zhao, Y. Cui, L. Liu, X. Ma, X. Qi, Y. Wang, Z. Liu, S. Ma, J. Liu, J. Wu, METTL3
facilitates oral squamous cell carcinoma tumorigenesis by enhancing c-myc
stability via YTHDF1-mediated m(6)A modification, Mol. Ther. Nucleic Acids 20
(2020) 1–12.
[66] J. Ye, Z. Wang, X. Chen, X. Jiang, Z. Dong, S. Hu, W. Li, Y. Liu, B. Liao, W. Han,
J. Shen, M. Xiao, YTHDF1-enhanced iron metabolism depends on TFRC m6
methylation, Theranostics 10 (2020) 12072–12089.
[67] E. Orouji, W.K. Peitsch, A. Orouji, R. Houben, J. Utikal, Oncogenic role of an
epigenetic reader of m6A RNA modification: YTHDF1 in Merkel cell carcinoma,
Cancers 12 (2020) 202.
[68] Y. He, J. Xing, S. Wang, S. Xin, Y. Han, J. Zhang, Increased m6A methylation level
is associated with the progression of human abdominal aortic aneurysm, Ann.
Transl. Med. 7 (2019) 797.
B. Han et al.
Cancer Letters 518 (2021) 256–265
264
[69] C. Xu, B. Yuan, T. He, B. Ding, S. Li, Prognostic values of YTHDF1 regulated
negatively by mir-3436 in Glioma, J. Cell Mol. Med. 24 (2020) 7538–7549.
[70] A.A. Yarmishyn, Y.P. Yang, K.H. Lu, Y.C. Chen, Y. Chien, S.J. Chou, P.H. Tsai, H.
I. Ma, C.S. Chien, M.T. Chen, M.L. Wang, Musashi-1 promotes cancer stem cell
properties of glioblastoma cells via upregulation of YTHDF1, Canc. Cell Int. 20
(2020) 597.
[71] H. Xie, J. Li, Y. Ying, H. Yan, K. Jin, X. Ma, L. He, X. Xu, B. Liu, X. Wang, X. Zheng,
L. Xie, METTL3/YTHDF2 m(6) A axis promotes tumorigenesis by degrading
SETD7 and KLF4 mRNAs in bladder cancer, J. Cell Mol. Med. 24 (2020)
4092–4104.
[72] X. Wang, J. Zhang, Y. Wang, Long noncoding RNA GAS5-AS1 suppresses growth
and metastasis of cervical cancer by increasing GAS5 stability, Am. J. Transl. Res.
11 (2019) 4909–4921.
[73] X. Chen, M. Xu, X. Xu, K. Zeng, X. Liu, B. Pan, C. Li, L. Sun, J. Qin, T. Xu, B. He,
Y. Pan, H. Sun, S. Wang, METTL14-mediated N6-methyladenosine modification
of SOX4 mRNA inhibits tumor metastasis in colorectal cancer, Mol. Canc. 19
(2020) 106.
[74] X. Shen, K. Zhao, L. Xu, G. Cheng, J. Zhu, L. Gan, Y. Wu, Z. Zhuang, YTHDF2
inhibits gastric cancer cell growth by regulating FOXC2 signaling pathway, Front.
Genet. 11 (2020) 592042.
[75] D. Dixit, B. Prager, R. Gimple, H. Poh, Y. Wang, Q. Wu, Z. Qiu, R. Kidwell, L. Kim,
Q. Xie, K. Vitting-Seerup, S. Bhargava, Z. Dong, L. Jiang, Z. Zhu, P. Hamerlik,
S. Jaffrey, J. Zhao, X. Wang, J. Rich, The RNA m6A reader YTHDF2 maintains
oncogene expression and is a targetable dependency in glioblastoma stem cells,
Canc. Discov. 11 (2020) 480–499.
[76] X. Lin, Z. Wang, G. Yang, G. Wen, H. Zhang, YTHDF2 correlates with tumor
immune infiltrates in lower-grade glioma, Aging 12 (2020) 18476–18500.
[77] R. Fang, X. Chen, S. Zhang, H. Shi, Y. Ye, H. Shi, Z. Zou, P. Li, Q. Guo, L. Ma,
C. He, S. Huang, EGFR/SRC/ERK-stabilized YTHDF2 promotes cholesterol
dysregulation and invasive growth of glioblastoma, Nat. Commun. 12 (2021) 177.
[78] J. Hou, H. Zhang, J. Liu, Z. Zhao, J. Wang, Z. Lu, B. Hu, J. Zhou, Z. Zhao, M. Feng,
H. Zhang, B. Shen, X. Huang, B. Sun, M.J. Smyth, C. He, Q. Xia, YTHDF2
reduction fuels inflammation and vascular abnormalization in hepatocellular
carcinoma, Mol. Canc. 18 (2019) 163.
[79] L. Zhong, D. Liao, M. Zhang, C. Zeng, X. Li, R. Zhang, H. Ma, T. Kang, YTHDF2
suppresses cell proliferation and growth via destabilizing the EGFR mRNA in
hepatocellular carcinoma, Canc. Lett. 442 (2019) 252–261.
[80] M. Chen, L. Wei, C.T. Law, F.H. Tsang, J. Shen, C.L. Cheng, L.H. Tsang, D.W. Ho,
D.K. Chiu, J.M. Lee, C.C. Wong, I.O. Ng, C.M. Wong, RNA N6-methyladenosine
methyltransferase-like 3 promotes liver cancer progression through YTHDF2-
dependent posttranscriptional silencing of SOCS2, Hepatology 67 (2018)
2254–2270.
[81] X.Y. Shao, J. Dong, H. Zhang, Y.S. Wu, L. Zheng, Systematic analyses of the role of
the reader protein of N (6)-methyladenosine RNA methylation, YTH domain
family 2, in liver hepatocellular carcinoma, Front. Mol. Biosci. 7 (2020) 577460.
[82] C. Zhang, S. Huang, H. Zhuang, S. Ruan, Z. Zhou, K. Huang, F. Ji, Z. Ma, B. Hou,
X. He, YTHDF2 promotes the liver cancer stem cell phenotype and cancer
metastasis by regulating OCT4 expression via m6A RNA methylation, Oncogene
39 (2020) 4507–4518.
[83] J. Paris, M. Morgan, J. Campos, G.J. Spencer, A. Shmakova, I. Ivanova,
C. Mapperley, H. Lawson, D.A. Wotherspoon, C. Sepulveda, M. Vukovic, L. Allen,
A. Sarapuu, A. Tavosanis, A.V. Guitart, A. Villacreces, C. Much, J. Choe, A. Azar,
L.N. van de Lagemaat, D. Vernimmen, A. Nehme, F. Mazurier, T.C.P. Somervaille,
R.I. Gregory, D. O’Carroll, K.R. Kranc, Targeting the RNA m(6)A reader YTHDF2
selectively compromises cancer stem cells in acute myeloid leukemia, Cell Stem
Cell 25 (2019) 137–148.
[84] Y. Qing, L. Dong, L. Gao, C. Li, Y. Li, L. Han, E. Prince, B. Tan, X. Deng, C. Wetzel,
C. Shen, M. Gao, Z. Chen, W. Li, B. Zhang, D. Braas, J. Ten Hoeve, G.J. Sanchez,
H. Chen, L.N. Chan, C.W. Chen, D. Ann, L. Jiang, M. Muschen, G. Marcucci, D.
R. Plas, Z. Li, R. Su, J. Chen, R-2-hydroxyglutarate attenuates aerobic glycolysis in
leukemia by targeting the FTO/m(6)A/PFKP/LDHB axis, Mol. Cell. 81 (2021)
922–939.
[85] H. Sheng, Z. Li, S. Su, W. Sun, X. Zhang, L. Li, J. Li, S. Liu, B. Lu, S. Zhang,
C. Shan, YTH domain family 2 promotes lung cancer cell growth by facilitating 6-
phosphogluconate dehydrogenase mRNA translation, Carcinogenesis 41 (2020)
541–550.
[86] J. Li, L. Wu, M. Pei, Y. Zhang, YTHDF2, a protein repressed by miR-145, regulates
proliferation, apoptosis, and migration in ovarian cancer cells, J. Ovarian Res. 13
(2020) 111.
[87] X. Guo, K. Li, W. Jiang, Y. Hu, W. Xiao, Y. Huang, Y. Feng, Q. Pan, R. Wan, RNA
demethylase ALKBH5 prevents pancreatic cancer progression by
posttranscriptional activation of PER1 in an m6A-YTHDF2-dependent manner,
Mol. Canc. 19 (2020) 91.
[88] C. Du, C. Lv, Y. Feng, S. Yu, Activation of the KDM5A/miRNA-495/YTHDF2/
m6A-MOB3B axis facilitates prostate cancer progression, J. Exp. Clin. Canc. Res.
39 (2020) 223.
[89] J. Li, S. Meng, M. Xu, S. Wang, L. He, X. Xu, X. Wang, L. Xie, Downregulation of N
6 -methyladenosine binding YTHDF2 protein mediated by miR-493-3p suppresses
prostate cancer by elevating N 6 -methyladenosine levels, Oncotarget 9 (2017)
3752–3764.
[90] J. Li, H. Xie, Y. Ying, H. Chen, H. Yan, L. He, M. Xu, X. Xu, Z. Liang, B. Liu,
X. Wang, X. Zheng, L. Xie, YTHDF2 mediates the mRNA degradation of the tumor
suppressors to induce AKT phosphorylation in N6-methyladenosine-dependent
way in prostate cancer, Mol. Canc. 19 (2020) 152.
[91] G. Chang, L. Shi, Y. Ye, H. Shi, L. Zeng, S. Tiwary, J. Huse, L. Huo, L. Ma, Y. Ma,
S. Zhang, J. Zhu, V. Xie, P. Li, L. Han, C. He, S. Huang, YTHDF3 induces the
translation of mA-enriched gene transcripts to promote breast cancer brain
metastasis, Canc. Cell 38 (2020) 857–871.
[92] W. Ni, S. Yao, Y. Zhou, Y. Liu, P. Huang, A. Zhou, J. Liu, L. Che, J. Li, Long
noncoding RNA GAS5 inhibits progression of colorectal cancer by interacting
with and triggering YAP phosphorylation and degradation and is negatively
regulated by the m(6)A reader YTHDF3, Mol. Canc. 18 (2019) 143.
[93] M. Wang, Y. Yang, J. Yang, J. Yang, S. Han, circ_KIAA1429 accelerates
hepatocellular carcinoma advancement through the mechanism of m(6)A￾YTHDF3-Zeb1, Life Sci. 257 (2020) 118082.
[94] X. Liu, L. Liu, Z. Dong, J. Li, Y. Yu, X. Chen, F. Ren, G. Cui, R. Sun, Expression
patterns and prognostic value of m(6)A-related genes in colorectal cancer, Am. J.
Transl. Res. 11 (2019) 3972–3991.
[95] F. Li, Y. Yi, Y. Miao, W. Long, T. Long, S. Chen, W. Cheng, C. Zou, Y. Zheng,
X. Wu, J. Ding, K. Zhu, D. Chen, Q. Xu, J. Wang, Q. Liu, F. Zhi, J. Ren, Q. Cao,
W. Zhao, N(6)-Methyladenosine modulates nonsense-mediated mRNA decay in
human glioblastoma, Canc. Res. 79 (2019) 5785–5798.
[96] J. Liu, G. Sun, S. Pan, M. Qin, R. Ouyang, Z. Li, J. Huang, The Cancer Genome
Atlas (TCGA) based m(6)A methylation-related genes predict prognosis in
hepatocellular carcinoma,, Bioengineered 11 (2020) 759–768.
[97] H.J. Luxton, B.S. Simpson, I.G. Mills, N.R. Brindle, Z. Ahmed, V. Stavrinides,
S. Heavey, S. Stamm, H.C. Whitaker, The oncogene metadherin interacts with the
known splicing proteins YTHDC1, Sam68 and T-STAR and plays a novel role in
alternative mRNA splicing,, Cancers 11 (2019) 1233.
[98] Y. Li, J.N. Zheng, E.H. Wang, C.J. Gong, K.F. Lan, X. Ding, The m6A reader
protein YTHDC2 is a potential biomarker and associated with immune infiltration
in head and neck squamous cell carcinoma, PeerJ 8 (2020) e10385.
[99] L. Ma, T. Chen, X. Zhang, Y. Miao, X. Tian, K. Yu, X. Xu, Y. Niu, S. Guo, C. Zhang,
S. Qiu, Y. Qiao, W. Fang, L. Du, Y. Yu, J. Wang, The m(6)A reader YTHDC2
inhibits lung adenocarcinoma tumorigenesis by suppressing SLC7A11-dependent
antioxidant function, Redox Biol 38 (2021) 101801.
[100] S. Sun, Q. Han, M. Liang, Q. Zhang, J. Zhang, J. Cao, Downregulation of m(6) A
reader YTHDC2 promotes tumor progression and predicts poor prognosis in non￾small cell lung cancer, Thorac. Canc. 11 (2020) 3269–3279.
[101] G. Bao, J. Huang, W. Pan, X. Li, T. Zhou, Long noncoding RNA CERS6-AS1
functions as a malignancy promoter in breast cancer by binding to IGF2BP3 to
enhance the stability of CERS6 mRNA, Canc. Med. 9 (2020) 278–289.
[102] Q. Wang, C. Chen, Q. Ding, Y. Zhao, Z. Wang, J. Chen, Z. Jiang, Y. Zhang, G. Xu,
J. Zhang, J. Zhou, B. Sun, X. Zou, S. Wang, METTL3-mediated m(6)A modification
of HDGF mRNA promotes gastric cancer progression and has prognostic
significance, Gut 69 (2020) 1193–1205.
[103] W. Guo, Q. Huai, H. Wan, L. Guo, P. Song, S. Gao, J. He, Prognostic impact of
IGF2BP3 expression in patients with surgically resected lung adenocarcinoma,
DNA Cell Biol. 40 (2021) 316–331.
[104] C.C. Hao, C.Y. Xu, X.Y. Zhao, J.N. Luo, G. Wang, L.H. Zhao, X. Ge, X.F. Ge, Up￾regulation of VANGL1 by IGF2BPs and miR-29b-3p attenuates the detrimental
effect of irradiation on lung adenocarcinoma, J. Exp. Clin. Canc. Res. 39 (2020)
256.
[105] T. Li, P.S. Hu, Z. Zuo, J.F. Lin, X. Li, Q.N. Wu, Z.H. Chen, Z.L. Zeng, F. Wang,
J. Zheng, D. Chen, B. Li, T.B. Kang, D. Xie, D. Lin, H.Q. Ju, R.H. Xu, METTL3
facilitates tumor progression via an m(6)A-IGF2BP2-dependent mechanism in
colorectal carcinoma, Mol. Canc. 18 (2019) 112.
[106] J. Tian, P. Ying, J. Ke, Y. Zhu, Y. Yang, Y. Gong, D. Zou, X. Peng, N. Yang,
X. Wang, S. Mei, Y. Zhang, C. Wang, R. Zhong, J. Chang, X. Miao, ANKLE1 N
-Methyladenosine-related variant is associated with colorectal cancer risk by
maintaining the genomic stability, Int. J. Canc. 146 (2020) 3281–3293.
[107] A. Tanabe, K. Tanikawa, M. Tsunetomi, K. Takai, H. Ikeda, J. Konno, T. Torigoe,
H. Maeda, G. Kutomi, K. Okita, M. Mori, H. Sahara, RNA helicase YTHDC2
promotes cancer metastasis via the enhancement of the efficiency by which HIF-
1alpha mRNA is translated, Canc. Lett. 376 (2016) 34–42.
[108] F. Bray, J. Ferlay, I. Soerjomataram, R.L. Siegel, L.A. Torre, A. Jemal, Global
cancer statistics 2018: GLOBOCAN estimates of incidence and mortality
worldwide for 36 cancers in 185 countries, CA A Cancer J. Clin. 68 (2018)
394–424.
[109] J.Z. Ma, F. Yang, C.C. Zhou, F. Liu, J.H. Yuan, F. Wang, T.T. Wang, Q.G. Xu, W.
P. Zhou, S.H. Sun, METTL14 suppresses the metastatic potential of hepatocellular
carcinoma by modulating N(6) -methyladenosine-dependent primary MicroRNA
processing, Hepatology 65 (2017) 529–543.
[110] Z. Lin, Y. Niu, A. Wan, D. Chen, H. Liang, X. Chen, L. Sun, S. Zhan, L. Chen,
C. Cheng, X. Zhang, X. Bu, W. He, G. Wan, RNA m(6) A methylation regulates
sorafenib resistance in liver cancer through FOXO3-mediated autophagy, EMBO
J. 39 (2020) e103181.
[111] R.S. Herbst, D. Morgensztern, C. Boshoff, The biology and management of non￾small cell lung cancer, Nature 553 (2018) 446–454.
[112] J. Choe, S. Lin, W. Zhang, Q. Liu, L. Wang, J. Ramirez-Moya, P. Du, W. Kim,
S. Tang, P. Sliz, P. Santisteban, R.E. George, W.G. Richards, K.K. Wong, N. Locker,
F.J. Slack, R.I. Gregory, mRNA circularization by METTL3-eIF3h enhances
translation and promotes oncogenesis, Nature 561 (2018) 556–560.
[113] S. Lin, J. Choe, P. Du, R. Triboulet, R.I. Gregory, The m(6)A methyltransferase
METTL3 promotes translation in human cancer cells, Mol. Cell. 62 (2016)
335–345.
[114] F. Lo Sardo, S. Strano, G. Blandino, YAP and TAZ in lung cancer: oncogenic role
and clinical targeting, Cancers 10 (2018) 137.
[115] Y. Zhang, X. Liu, L. Liu, J. Li, Q. Hu, R. Sun, Expression and Prognostic
Significance of m6A-Related Genes in Lung Adenocarcinoma, Med. Sci. Mon. 26
(2020) e919644.
B. Han et al.
Cancer Letters 518 (2021) 256–265
265
[116] T. Zhao, D. Sun, M. Zhao, Y. Lai, Y. Liu, Z. Zhang, N(6)-methyladenosine mediates
arsenite-induced human keratinocyte transformation by suppressing p53
activation, Environ. Pollut. 259 (2020) 113908.
[117] D. Han, J. Liu, C. Chen, L. Dong, Y. Liu, R. Chang, X. Huang, Y. Liu, J. Wang,
U. Dougherty, M.B. Bissonnette, B. Shen, R.R. Weichselbaum, M.M. Xu, C. He,
Anti-tumour immunity controlled through mRNA m(6)A methylation and
YTHDF1 in dendritic cells, Nature 566 (2019) 270–274.
[118] Y. He, J. Xing, S. Wang, S. Xin, Y. Han, J. Zhang, Increased m6A methylation level
is associated with the progression of human abdominal aortic aneurysm, Ann.
Transl. Med. 7 (2019) 797.
[119] X. Zhao, L. Cui, Development and validation of a mA RNA methylation regulators￾based signature for predicting the prognosis of head and neck squamous cell
carcinoma, Am. J. Canc. Res. 9 (2019) 2156–2169.
B. Han et al.