v-myb-oncogene of avian myeloblastosis virus transforms myelomonocytic cells in vitro and induces acute monoblastic leukemia in vivo. The transforming effect of the v-myb can be suppressed using phorbol ester (TPA) or histone deacetylase inhibitor trichostatin A (TSA), the inducers of cell differentiation that are in clinical trials. In this study, we used proteomics-based approach to identify proteins with variable expression in differentiated BM2 cells. Proteome variations induced by TPA and TSA were compared to examine the mechanism of differentiation-promoting effects of these drugs. We found that expression of several proteins participating in cell cytoskeleton rearrangement, heat shock response, proteosynthesis and cell signaling was altered in TPA- or TSA-treated cells. We present here the first comparative proteome analysis of v-myb-transformed monoblasts BM2 focused on identification of proteins involved in their terminal differentiation.