SB was demonstrated to induce cell cycle changes at different levels in breast cancer cells and gingival fibroblasts. SB was also demonstrated to increase DNA methylation in cultured fibroblasts. Although SB results a marked influence in vitro, it reveals a low efficiency in vivo, most-likely due to its rapid metabolism. Pivaloyloxymethyl butyrate AN9 also known, a derivative of BA, tested and developed in our laboratory, is a lot more powerful thanBAin the induction of cytodifferentiation, supplier Celecoxib inhibition of cancer cell growth, gene expression and histone hyperacetylation in cell cultures and in vivo models. Pivanex also demonstrates significant activities in mice models on the other hand with BA. It had been found that Pivanexinduced antiproliferative results in 21 primary samples of acute leukemia and 20 primary samples of chronic lymphocytic leukemia patients cells Pivanex in a phase I clinical trial including non small cell lung cancer, induced a partial response in one individual while six other patients with other malignancies experienced stable disease for 4 10 months. In a phase II clinical trial with NSCLC individuals, in whom cancer had progressed after one or two previous chemotherapy regimens, the 1 year survival rate attained with Pivanex was 47%, with a median survival of 11. 1 weeks. Pivanex caused apoptosis accompanied by improvements in apoptotic Cellular differentiation regulating proteins in cells based on T CLL patients. K562 cells are considered as pluripotent hematopoietic progenitor cells, expressing markers for monocytic, granulocytic, erythroid and megakaryocytic lineages. This cell line, expressing BCR ABL/p210 tyrosine kinase, is famous to be particularly resistant to apoptosis and multiple drug resistance is demonstrated by it. A few studies have suggested that the p210 bcr abl is involved in the Oprozomib Proteasome inhibitors inhibition of differentiation and apoptosis of K562 cells, since the inhibition of p210 BCR ABL triggered erythroid differentiation and apoptosis. DNA and pivanex specific anti neoplastic agents were demonstrated to induce the complete growth inhibition of mouse monocytic leukemia Mm 1. Our results with Doxorubicin have shown that mixture of Doxorubicin and Pivanex paid off bcl 2 levels and enhanced apoptosis in B CLL individuals cells greater than additively. In this study we show the effect of Pivanex and Pivanex along with STI571 on K562 cells, as a model for CML. Pivanex was found to down regulate bcr abl protein and in doing so, might improve the reaction of K562 cells to imatinib. Structure culture products were received as follows: RPMI choice from Bio Lab Ltd., Laboratories, Jerusalem, Israel; described bovine calf serum from Hyclone Laboratories, Utah, USA; glutamine, penicillin and streptomycin from Beth Haemek, Biological Industries, Israel. All the chemicals were purchased from Sigma Chemicals, St. Louis, MO, USA, except where otherwise indicated.