Increase in shedding of intercellular adhesion molecule-1 in human malignant melanoma cell lines treated with hyperthermia in vitro.

Human malignant melanoma cell lines were found to increase shedding of soluble intercellular adhesion molecule-1 (sICAM-1) into the culture medium when the cells were treated with hyperthermia at 41-43 degrees C for 3-6 hr in vitro. The content of ICAM-1 in the cell lysate was also found to be increased after hyperthermia. The increased rate of ICAM-1 concentration in the cells was at maximum when they were incubated at 41 degrees C for 3 hr. Also, the melanoma cell lines heat-treated at 41 degrees C showed more intense immunofluorescence in the ICAM-1 expression on the cell surface. It remains to be investigated further whether the effects of hyperthermia on the ICAM-1 expression in melanoma cells is to augment membrane ICAM-1 expression, which in turn leads to shedding of soluble ICAM-1 or only to acceleration of shedding of sICAM-1 by unknown mechanisms.