Interaction of hyperthermia with Taxol in human MCF-7 breast adenocarcinoma cells

Hyperthermia treatments (43oC, 1h) were performed on exponentially growing MCF-7 breast adenocarcinoma cells at the beginning, middle, or end of 24h incubations of the cells in vitro with Taxol (paclitaxel). When the cells were heated at the beginning or middle of the Taxol incubation, the hyperthermia treatment protected against the toxic effect of each of the Taxol concentrations examined (5, 10 and 100nM). Consistent with earlier studies, Taxol treatment at 37oC resulted in an accumulation of greater than 94% of the cells in G2/M at 24h. Heating the cells at the middle or end of the Taxol treatment resulted in a similar accumulation. However, heat treatment during the first hour of Taxol exposure resulted in a significantly smaller percentage of cells ( 50% ) in G2/M. HPLC analysis showed that at 37oC, Taxol uptake into MCF-7 cells approached maximum within 0.25h and increased only slightly more over the next 11.75h. The parental Taxol level was markedly lower by 24h. In contrast, 1h hyperthermia treat...