DIFFERENTIAL INDUCTION OF CELL-DEATH IN HUMAN GLIOMA CELL-LINES BY SODIUM-NITROPRUSSIDE

BACKGROUND, High grade gliomas represent very aggressive and lethal fo rms of human cancer, which often exhibit recurrence after surgical int ervention and resistance tr conventional chemotherapeutic and radiolog ic treatment. The clinically approved antihypertensive agent sodium ni troprusside (SNP) has been shown to induce cytotoxicity toward a numbe r of carcinoma cell lines in vitro. METHODS, Three human glioma cell l ines were examined for susceptibility to the cytotoxic effects of SNP. The role of the protein kinase C (PKC)alpha gene in mediating resista nce to SNP-induced killing in U343 cells was investigated using antise nse oligonucleotide inhibition. Stable transfection and overexpression of the PKC alpha gene in the SNP-susceptible cell line U251 was perfo rmed to further implicate PKC alpha as a mediating factor in SNP cytot oxicity. In addition, the presence of bcl-2 protein in these cells was examined for possible correlation(s) with resistance to SNP. RESULTS, Exposure of U251 cells and LN-Z308 cells to 0.5 mM SNP resulted in si gnificant cytotoxicity over a 72-hour period. U343 cells were resistan t to SNP killing. U343 cells were shown to exhibit higher basal levels of PKC alpha and bcl-2 than either U251 or LN-Z308 cells. bcl-2 expre ssion and resistance to SNP toxicity both were decreased by the introd uction of PKC alpha antisense oligonucleotides into U343 cells. Conver sely, enhanced PKC activity in PKC alpha-transfected U251 clones was a ssociated with increased bcl-2 expression and greater resistance to SN P-induced toxicity relative to control transfected cells. CONCLUSIONS, SNP can induce cytotoxicity in glioma cells. The susceptibility of th ese glioma cells to nitroprusside-induced killing appears to be correl ated inversely with bcl-2 and PE;C activity. bcl-2 levels in these cel ls can be altered through modulation of PKC signaling, specifically, b y induction or inhibition of PKC alpha. These in vitro results provide an interesting basis for further study into the potential use of SNP for treatment elf human gliomas in patients receiving combination ther apy wish conventional chemotherapeutic agents that exhibit PKC inhibit ory activity. (C) 1998 American Cancer Society.