INTRACELLULAR CALCIUM CHANGES AND CHEMOSENSITIVITIES OF HUMAN EPIDERMOID CARCINOMA CELL-LINES AFTER EXPOSURE TO CISPLATIN

In order to elucidate the mechanisms of cisplatin (cis-diamminedichlor oplatinum; CDDP)-resistant tumor cells, we previously established a CD DP-resistant KB cell line (KBrc cells) from a parental KB cell line de rived from epidermoid carcinoma (KB cells). The KBrc cells were resist ant to 5 kinds of platinum (Pt) drugs. Intracellular Pt concentrations in KBrc cells were lower than in KB cells. Decrease of intracellular Pt concentrations was one of the CDDP-resistant mechanisms. When we me asured changes of intracellular calcium ion concentration ([Ca2+]i) du ring exposure to high-dose CDDP, a sustained elevation of the [Ca2+]i level was observed in the KB cells. These results suggest that the mec hanisms underlying CDDP resistance involve changes in calcium channels and an alteration of calcium homeostasis in the tumor cell line.