Elevated concentrations of the small stress protein HSP27 in rat renal tumors

The expression of two small stress proteins, alpha B crystallin and the 27-kDa heat shock protein (HSP27), was studied quantitatively and immunohistochemically in normal kidney and renal tumors in rats. Levels of alpha B crystallin in renal cell tumors tended to be higher than in normal kidney (P = 0.07), but with a wide range of values, whereas they were significantly lower in mesenchymal tumors (P < 0.0001). In contrast, HSP27 concentrations in both renal cell (mean +/- SD: 1790 +/- 940 ng/mg protein, n = 15) and mesenchymal (1260 +/- 1080 ng/mg protein, n = 10) tumors were significantly higher than the normal kidney value (142 +/- 30 ng/mg protein, n = 10, P < 0.0001). A positive correlation was found between alpha B crystallin and HSP27 levels limited to the renal cell tumor case (Pearson's correlation coefficient, r = 0.68, P < 0.01). Immunohistochemistry revealed the loops of Henle to be positive for alpha B crystallin, whereas HSP27 staining was positive in glomerular and interstitial vascular walls and epithelial cells of proximal and distal tubules. Positive immunostaining for alpha B crystallin was demonstrated in six of nine renal cell tumors (67%) studied and for HSP27 in all of the nine cases (100%).