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

The expression of two small stress proteins, αB crystallin and the 27-kDa heat shock protein (HSP27), was studied quantitatively and immunohistochemically in normal kidney and renal tumors in rats. Levels of αB 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 αB 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 αB crystallin, whereas HSP27 staining was positive in glomerular and interstitial vascular walls and epithelial cells of proximal and distal tubules. Positive immunostaining for αB crystallin was demonstrated in six of nine renal cell tumors (67%) studied and for HSP27 in all of the nine cases (100%).