Background/purpose: Heat shock proteins (HSPs) are synthesized by cells in response to various stress conditions, including carcinogenesis. Some studies also showed that they might predict clinical prognosis. The aim of this study is to detect the expression of HSP70 and HSP90alpha in children with Wilms tumor and explore its clinical significance.
Methods: The expression of HSP70 and HSP90alpha was evaluated in the tissue specimens of 30 patients (13 males and 17 females aged 5 months to 9 years with mean age of 37.4 +/- 23.9 months) with Wilms tumor by histochemistry and reverse transcriptase polymerase chain reaction techniques. According to the NWTS3 study criteria, all patients were favorable histological types, including mesenchymal type in 6, blastemal type in 12, and epithelium type in 7, and mixed type in 5. The clinical staging of the tumor included stage I in 4, stage II in 8, stage III in 12, and stage IV in 6.
Results: On the reverse transcriptase polymerase chain reaction study, the amount of HSP70 and HSP90alpha mRNA in the tumor tissue was lower than in the controls. The HSP70 to beta-actin ratio was 0.74 +/- 0.14 and 1.38 +/- 0.22 in the tumor tissue and the normal kidney, respectively (P < .0001). The HSP90alpha to beta-actin ratio was 0.60 +/- 0.14 and 0.96 +/- 0.15 in the tumor tissue and the normal kidney, respectively (P < .0001). On immunolabeling, the expression of HSP70 and HSP90alpha was confined to blastemal and epithelial components, whereas the tumor stroma was negative. The expression of HSP70 and HSP90alpha was mainly located in the cytoplasm of the tubular epithelial cell, mesangial cell, and endothelial cell in the normal kidney. The positive expression rates of HSP70 and HSP90alpha proteins were significantly lower in the tumor group (73.3%, 22/30; 76.7%, 23/30) than in the control group (100%, 30/30; 100%, 30/30), P = .002 and P = 0.005, respectively. Positive correlation was found between HSP70 gene and protein expression (r = 0.64, P < .0001). Positive correlation was also found between HSP90alpha gene and protein expression (r = 0.67, P < .0001). HSP70 and HSP90alpha gene and protein expression showed no correlation with its corresponding tumor stages (P > .05). The expression of HSP70 and HSP90alpha genes was significantly higher in children who survived when compared with those patients who died during the follow-up period, P = .017 and P = 0.004, respectively. The positive expression rates of HSP70 and HSP90alpha proteins were also significantly higher in children who survived (82.6%, 19/23; 87.0%, 20/23) than in those who died (42.9%, 3/7; 42.9%, 3/7), P = .037 and P = 0.016, respectively.
Conclusions: The expression of HSP70 and HSP90alpha decreased in Wilms tumor and is confined to blastemal and epithelial components; it was higher in patients who survived, which suggested that they might be of prognostic value.