Drug resistance and cross-sensitivity in cultured human osteosarcoma cells.

The sensitivity, cross-sensitivity, acquired resistance and restoration of sensitivity to adriamycin (ADR) in cultured human osteosarcoma (OST) cells were studied from the viewpoints of cell proliferation and cell cycle pattern by flow cytometry. OST cells resistant to ADR were produced by a treatment which consists of a 40-hour exposure to high doses of ADR and subsequent cultivation for 6 weeks and was repeated five times. ADR-resistant cells showed cross-resistance to methotrexate (MTX), and vincristine (VCR), and collateral sensitivity to cisplatin (CDDP). Treatment of the ADR-resistant cells with ADR and verapamil, a Ca-antagonist, resulted in an increased inhibition of sarcoma cell growth.