knk-437 and Fever

Although heat shock proteins (HSP) are well known to contribute to thermotolerance, they only play a supporting role in the phenomenon. Recently, it has been reported that heat sensitivity depends on heat-induced DNA double-strand breaks (DSB), and that thermotolerance also depends on the suppression of DSB formation. However the critical elements involved in thermotolerance have not yet been fully identified. Heat produces DSB and leads to cell death through denaturation and dysfunction of heat-labile repair proteins such as DNA polymerase-beta (Pol beta). Here the authors show that thermotolerance was partially suppressed in Pol beta(-/-) mouse embryonic fibroblasts (MEF) when compared to the wild-type MEF, and was also suppressed in the presence of the HSP inhibitor, KNK437, in both cell lines. Moreover, the authors found that heat-induced gamma H2AX was suppressed in the thermotolerant cells. These results suggest that Pol beta at least contributes to thermotolerance through its reactivation and stimulation by Hsp27 and Hsp70. In addition, it appears possible that fewer DSB were formed after a challenging heat exposure because preheat-induced Hsp27 and Hsp70 can rescue or restore other, as yet unidentified, heat-labile proteins besides Pol beta. The present novel findings provide strong evidence that Pol beta functions as a critical element involved in thermotolerance and exerts an important role in heat-induced DSB.

Topics: Animals; Benzhydryl Compounds; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; DNA Breaks, Double-Stranded; DNA Polymerase beta; Fever; Fibroblasts; Flow Cytometry; Heat-Shock Proteins; Hot Temperature; Humans; Lung Neoplasms; Mice; Models, Biological; Pyrrolidinones

A newly synthesized reagent, KNK437, has been found specifically to inhibit the synthesis of heat shock proteins in vitro. In this study, we investigated the effects of KNK437 on the synthesis of heat shock proteins and the induction of thermotolerance in transplantable tumors in vivo. SCC VII cells were grown in vivo and transplanted into C3H/He mice. The concentrations of KNK437 in the tumors and the sera of the mice were examined by high-performance liquid chromatography. Hsp72 synthesis was examined by Western immunoblot analysis. The response to hyperthermia was evaluated in terms of the delay in tumor growth. KNK437 had low toxicity in vivo. The concentration of KNK437 in the tumors gradually increased and reached a peak 6 h after i.p. injection. Hsp72 were synthesized 8 h after hyperthermia at 44 degrees C for 10 min, and their synthesis was inhibited by administration of KNK437 6 h before hyperthermia. At a concentration of 200 mg/kg, KNK437 alone showed no antitumor effects and did not increase the thermosensitivity of nontolerant tumors. The same dose of KNK437 enhanced the antitumor effects of fractionated heat treatment at 44 degrees C in a synergistic manner. This study strongly suggests the inhibition of thermotolerance via the inhibition of HSP72 in vivo. The inhibition of thermotolerance by KNK437 may help to improve the efficacy of clinical fractionated hyperthermia.

Topics: Animals; Benzhydryl Compounds; Cell Division; Chromatography, High Pressure Liquid; Electrophoresis, Polyacrylamide Gel; Fever; Heat-Shock Proteins; Humans; Immunoblotting; Injections, Subcutaneous; Male; Mice; Mice, Inbred C3H; Mice, Inbred ICR; Molecular Structure; Neoplasm Transplantation; Pyrrolidinones; Temperature; Tumor Cells, Cultured