INHIBITION OF CELL-PROLIFERATION AND GLUTATHIONE-S-TRANSFERASE BY ASCORBYL ESTERS AND INTERFERON IN MOUSE GLIOMA

Mouse glioma-26 (G-26) cell line established in this laboratory was us ed in the study. The in vitro effect of ascorbyl esters, viz., ascorby l-palmitate (As-P), -stearate (As-S) and mouse interferon-alpha/beta ( MulFN-alpha/beta) on the glioma cell viability, proliferation and glut athione S-transferase (GST) activity was investigated. Cell viability and proliferation were examined by colorimetric MTT assay and [H-3]-th ymidine incorporation, respectively. Incubation (24h) of G-26 cells wi th As-S, As-P or MulFN-alpha/beta, resulted in a dose dependent decrea se in cell viability (IC50= 125 muM As-S; 175 muM As-P and 3.6 x 10(4) U/ml MulFN-alpha/beta) and proliferation (IC50 = 157muM As-S; 185muM As-P and 3.6x 10(4) U/ml MulFN-alpha/beta). A combined exposure to 175 muM As-S and 800 U/ml of MulFN-alpha/beta resulted in a greater than a n additive effect on cell viability and proliferation. The inhibition of cell proliferation/viability by interferon was species specific and was observed only with homologous MulFN-alpha/beta, but not with huma n interferon-alpha lymphoblastoid or human interferon-beta. Ascorbyl e sters inhibited cytosolic GST activity (1.50 = 15.0muM As-S and 28.5mu M As-P) towards 1-chloro-2,4-dinitrobenzene in a dose dependent manner . The apparent Ki values for affinity purified GST, deduced from Dixon plots were 0.95muM and 2.0muM for As-S and As-P, respectively. Signif icant inhibition of GST was also observed in the cytosol isolated from G-26 cells exposed to 300muM As-S or 800 U/ml MulFN-alpha/beta.