INTRACELLULAR-DISTRIBUTION OF HSP70 DURING LONG-DURATION MODERATE HYPERTHERMIA

Hyperthermia causes cell killing and is also an effective radiosensiti zer. In recent years, the protocol of long duration moderate hyperther mia (LDMH) has been used to treat cancer patients in the clinic. Howev er, the results of many studies indicate that some tumour cells may re veal the capability to express chronic thermotolerance, a factor of po tentially critical impact in the efficacy of clinical hyperthermia. Pr eviously it has been reported that two out of five human cell lines st udied were able to proliferate at 41.1 degrees C. In the present study , the intracellular distribution of hsp70 during LDMH was measured as a potential marker for chronic thermotolerance with continued cell pro liferation. In all cell lines studied, hsp70 became localized in the n ucleus immediately after the cells were shifted from 37 degrees C to 4 1.1 degrees C. However, in the two cell lines which recovered and cont inued to proliferate, NSY42129 and HT29, hsp70 was delocalized from th e nucleus within 4 h. Conversely, in the cell lines for which 41.1 deg rees C was lethal, hsp70 did not delocalize from the nucleus but rathe r became localized in the nucleolar regions. Neither the NSY42129 cell s nor the HT29 cells showed any preferential nucleolar punctate staini ng. Thus, it appears that the pattern of hsp70 nuclear localization an d delocalization is related to the cells' ability to survive moderate heat shocks.