Effects of combinations of 7beta-hydroxycholesterol and anticancer drugs or ionizing radiation on the proliferation of cultured tumor cells.

Oxysterols compose a large class of natural substances endowed in a number of cases with marked antiproliferative and cytotoxic activities. The consequences of treatments combining 7beta-hydroxycholesterol (7beta-OHC) or XG-142 (a galactose-linked hydrosoluble derivative of 7beta-OHC) with drugs used in cancer chemotherapy or gamma radiation has been evaluated upon a variety of tumor cell lines: Hep-G2, U937, K562 cells, its adriamycin-resistant variant K562 Adr+ and RDM4. Proliferation was assessed by the Uptiblue assay and the [3H]Thymidine incorporation test. Results indicated that 7beta-OHC increased the sensitivity of tumor cells to adriamycin, VP-16, 5-FU and bleomycin to various degrees. 7beta-OHC was found to reinforce the susceptibility of K562 adriamycin-resistant cells to this drug. In RDM4 cells, an enhanced radiosensitivity by 7beta-OHC was also obtained, whereas XG-142 was less efficient in provoking such an effect.