MODULATION EFFECTS OF HEXAMETHYLENE BISACETAMIDE ON GROWTH AND DIFFERENTIATION OF CULTURED HUMAN-MALIGNANT GLIOMA-CELLS

The modulation effects of hexamethylene bisacetamide (HMBA), a differe ntiation-inducing agent, on growth and differentiation of cells from h uman malignant glioma cell line SHG-44 were studied. At cytostatic dos es (2.5 mM, 5 mM, 7.5 mM, and 10 mM for 15 days), HMBA exerted a marke d inhibitory effect on cell proliferation. Exposure to HMBA (5 mM and 10 mM for 12 days) also resulted in an accumulation of cells in G(0)/G (1) phase and a decrease of cells in S phase as analyzed by flow cytom etry. The reversible effects of 7.5 mM HMBA and 10 mM HMBA on cell pro liferation and 10 mM HMBA on disruption of cell cycle distribution wer e observed when HMBA was removed from culture media on Day 6 and repla ced with HMBA-free media. Colony-forming efficiency (CFE) in soft agar was remarkably decreased by HMBA (2.5 mM, 5 mM, 7.5 mM, and 10 mM for 14 days), and in 7.5 mM HMBA- and IO mM HMBA-treated cells, the CFEs were reduced to 25% and 12.5%, respectively, of that in untreated cell s. Cells treated with HMBA (5 mM and 10 mM for 15 days) remained tumor igenic in athymic nude mice, but the growth rates of the xenografts we re much slower than those in the control group. The effects of HMBA on cell proliferation, cell cycle distribution, CFE, and growth of xenog rafts were dose dependent. A more mature phenotype was confirmed by th e morphological changes from spindle shape to large polygonal stellate shape and remarkably elevated expression of glial fibrillary acidic p rotein in cells exposed to HMBA (5 mM, 10 mM fur 15 days). Our results showed that a more differentiated phenotype with marked growth arrest was induced in SHG-44 cells by HMBA.