REDUCTION OF SUSCEPTIBILITY TO NK LYSIS IN CISPLATIN-RESISTANT K562 CELL-LINES

The development of resistance to cisplatin (CDDP) occurs both in vitro and in vivo. We cultured K562 cells with continuous exposure to gradu ally increasing doses of CDDP and produced CDDP resistant K562 subline s. CDDP-resistant sublines were found to be cross-sensitive to Mit-C a nd cross-resistant to DXR and cyclophosphamide. These sublines were te sted for their susceptibility to NK-mediated lysis using NK cells isol ated from 10 healthy donors and 12 patients with breast cancer. K562/B 6 and K562/C9 CDDP-resistant sublines were more resistant (22 +/- 5 % and 19 +/- 3 % lysis.respectively for Ca patients, and 34 +/- 6 and 31 +/- 5 % for healthy donors) than the maternal K562 cells (36 +/- 3 % for Ca patients and 55 +/- 5 % for healthy individuals). The correlati on of cisplatin resistance, with a diminished susceptibility by NK lys is, should permit the selection of patients suitable for cisplatin-bas ed chemotherapy.