Chronic thermotolerance with continued cell proliferation.
The human colon adenocarcinoma cell line, NSY42129, is capable of proliferation at 41.1 degrees C. This ability appears to be due to a type of chronic thermotolerance, as opposed to selection or adaptation, that allows these cells to traverse S phase at elevated temperatures. Four other human cell lines were studied for their ability to proliferate at 41.1 degrees C. Of those only one, also a colon adenocarcinoma, showed the ability to sustain proliferation at 41.1 degrees C. While all the cell lines examined showed increased levels of the major heat shock proteins at 41.1 degrees C, the cellular amounts of these proteins did not correlate with their ability to proliferate at 41.1 degrees C. However, the ability of the cells to proliferate at 41.1 degrees C did correlate with their ability to sustain elevated rates of synthesis of hsp70 and hsp90. These results could have implications in the clinical application of hyperthermia, particularly the use of long duration moderate hyperthermia.