Expression of heat shock protein 72 in renal cell carcinoma: possible role and prognostic implications in cancer patients.

Renal cancer cells from 43 patients and normal renal cells from 10 of them were studied for the expression of highly stress-inducible heat shock protein 72 (HSP72) by means of immunoperoxidase analysis. It was found that HSP72 was expressed in a significantly higher percentage of renal cancer cells than normal renal cells (P = 0.0001), the mean percentage of positive cells being 33.1 +/- 18% and 8 +/- 5%, respectively. Moreover, a percentage of HSP72-positive cells that was less than the cut-off point (18%, mean value of normal cells +2 S.D.) significantly correlated with shorter disease-free survival (P = 0.002). The renal cancer cell populations taken from the 21 patients who relapsed after a median time of 13 months (range 3-73 months) had a significantly lower percentage of HSP72-positive cells (mean value 25.1 +/- 17%) than the cells taken from the patients who remained tumour-free (mean value 40.8 +/- 15%) after a median period of 72 months (range 19-96 months, P = 0.003). It was also demonstrated that HSP72 expression can be significantly increased by 48-h in vitro incubation with rIFN-gamma (P = 0.007). These data suggest that HSP72 may represent a favourable prognostic factor regardless of stage and histological grade and its expression may be increased by treatment with rIFN-gamma. Further studies are needed in order to investigate the relationship between HSP72 and the immunoeffector cells.