Histone Deacetylase Inhibitor M344 Inhibits Cell Proliferation and Induces Apoptosis in Human THP-1 Leukemia Cells.

Histone acetylation plays an important role in the silencing and activation of genes involved in tumoregenesis. Trichostatin A, originally identified as an anti-fungal drug, is a potent inhibitor of histone deacetylase (HDAC) with potential anti-tumor activity. In this study, we investigated the effect of M344, an amide analogues of trichostatin A, on the growth and differentiation of THP-1 human leukemia cells. We showed that at low doses, (< 0.2 muM), M344 could inhibit the growth of THP-1 cells at G1 phase in vitro with low cytotoxic effect. Low dose of M344 exerted some differentiating effect on THP-1 cells as judged by the expression of c-fms proto-oncogene (M-CSF receptor) and appearance of adherent cells. Growth arrest induced by M344 is associated with increased levels of cyclin-dependent protein kinase inhibitor p21 and cyclin E, in agreement with G1 phase arrest. At higher doses (2 muM), M344 could induce THP-1 cells to undergo apoptosis, which was associated with the cleavage of PARP, cytochrome c release and activation of both caspases-8, -9, followed by the activation of caspase-3. In addition, M344 could increase the levels of pro-apoptotic protein Bax but decreased the levels of anti-apoptotic protein XIAP. M344 is a potent activator of NF-kappaB transcription factor. RT-PCR assay showed that the M344 could transiently increase IL-1 expression yet markedly decreased TNF-alpha expression. Our results show that M344 is a potent growth inhibitor and inducer of apoptosis in human leukemia cells and suggest potential therapeutic strategies of HDAC inhibitors for patients with leukemias.