SB was shown to cause cell cycle changes at different concentrations in breast cancer cells and gingival fibroblasts. SB was also demonstrated to improve DNA methylation in cultured fibroblasts. Even though SB effects a marked effect in-vitro, it exhibits a low strength in vivo, almost certainly due to its rapid metabolism. Pivaloyloxymethyl butyrate AN9 also known, a kind of BA, designed and tested in our laboratory, is significantly more potent thanBAin the induction of cytodifferentiation, Natural products supplier inhibition of cancer cell growth, gene expression and histone hyperacetylation in cell cultures and in vivo models. Pivanex also demonstrates significant actions in mice models in contrast 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, caused a partial answer in a single 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 advanced after one or two previous chemotherapy regimens, the 1 year survival rate achieved with Pivanex was 4-7, with a median survival of 1-1. 1 weeks. Pivanex caused apoptosis followed by improvements in apoptotic Meristem regulating proteins in cells derived from N CLL patients. K562 cells are considered as pluripotent hematopoietic progenitor cells, expressing markers for granulocytic, erythroid, monocytic and megakaryocytic lineages. This cell line, expressing BCR ABL/p210 tyrosine kinase, is well known to be specially resistant to apoptosis and multiple drug resistance is demonstrated by it. Many studies have suggested the p210 bcr abl is mixed up in Ubiquitin ligase inhibitor inhibition of differentiation and apoptosis of K562 cells, because the inhibition of p210 BCR ABL triggered erythroid differentiation and apoptosis. Pivanex and DNA certain anti neoplastic agents were shown to cause the complete growth inhibition of mouse monocytic leukemia Mm 1. Our results with Doxorubicin show that mix of Doxorubicin and Pivanex paid down bcl 2 levels and increased apoptosis in B CLL people cells over additively. In this study we show the effect of Pivanex and Pivanex coupled with STI571 on K562 cells, as a model for CML. Pivanex was found to down regulate bcr abl protein and in doing this, might boost the reaction of K562 cells to imatinib. Structure culture services and products were received as follows: RPMI channel from Bio Lab Ltd., Laboratories, Jerusalem, Israel; identified bovine calf serum from Hyclone Laboratories, Utah, USA; glutamine, penicillin and streptomycin from Beth Haemek, Biological Industries, Israel. All other chemicals were obtained from Sigma Chemicals, St. Louis, MO, USA, except where otherwise indicated.