OBJECTIVETo explore the blockade effect of phenylbutyrate (PB), a histone deacetylase inhibitor, on the in vitro biological function of AML1/ETO to reverse its transcription repression and induce Kasumi-1 cells to differentiate and apoptosis.

METHODSKasumi-1 cells were treated with PB at different concentrations in suspension culture. Cell proliferation was analysed by MTT assay, morphological changes by light and electron microscopy, expression of myeloid-specific differentiation antigen and cell cycle by flow cytometry, cell apoptosis by annexin V staining, agarose gel electrophoresis and flow cytometry.

RESULTSPB treatment caused a dose-dependent inhibition of the cell proliferation. The IC(50) was about 2.3 mmol/L. PB treatment led to a progressive decline in the fraction of S-phase cells and increase in G(0)/G(1) cells. PB induced a time- and dose-dependent increase in expression of myeloid cell surface protein CD(11b) and CD(13). A dose-dependent increase in early apoptosis for 2 days treatment, late apoptosis for 3 days treatment. The DNA ladder of apoptosis was observed on agarose gel electrophoresis for 5 days treatment. Morphological features of monocytoid differentiation and apoptosis were seen on Wright-Giemsa staining smears.

CONCLUSIONPB treatment could inhibit proliferation of Kasumi-1 cells, induce partial differentiation, apoptosis and accumulation of cells in G(0)/G(1) phase.