Modulation of 9-nitrocamptothecin-induced apoptosis by hyperthermia in human leukemia HL-60 cells

We have investigated whether hyperthermia (HT) treatment at 43 degrees C fo r 15-60 min can affect the extent of apoptosis induced in human leukemia HL -60 cells by the anticancer drug 9-nitrocamptothecin (9NC). Quantitative ch anges in the apoptotic (Ap) fraction in the cell cultures were monitored by flow cytometry. The results showed that (i) heating for 15 min prior to or concurrently with 9NC exposure had no effect on the Ap fraction generated by the drug alone, whereas 60 min heating resulted in an increase in the Ap fraction; and (ii) heating of the cells at 6-24 h after exposure to the dr ug enhanced the Ap fraction, These results indicate that appropriate schedu ling of HT and 9NC treatments may lead to thermochemotherapy protocols that will result in increased SNC-induced death of human leukemia cells. [(C) 1 999 Lippincott Williams & Wilkins.]