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 gradually increasing doses of CDDP and produced CDDP resistant K562 sublines. CDDP-resistant sublines were found to be cross-sensitive to Mit-C and cross-resistant to DXR and cyclophosphamide. These sublines were tested for their susceptibility to NK-mediated lysis using NK cells isolated from 10 healthy donors and 12 patients with breast cancer. K562/B6 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 correlation of cisplatin resistance, with a diminished susceptibility by NK lysis, should permit the selection of patients suitable for cisplatin-based chemotherapy.