Expression of heat shock protein 70 (HSP70) in patients with colorectal adenocarcinoma--immunohistochemistry and Western blot analysis

Abstract

The role of heat shock protein 70 (HSP70) expression has been investigated in various types of tumors. There are only little and controversial data about its clinical relevance in colorectal carcinoma, one of the most common carcinomas observed in humans. In this study we investigated expression of HSP70 in human colonic carcinoma and possible correlation with clinicopathology. To assess patterns (cytosolic and membrane) of HSP70 expression, the 48 surgically removed colorectal adenocarcinomas and 12 normal colonic and rectal mucosal samples were examined by immunohistochemistry and Western-blot. According to results of immunohistochemistry, expression of cytoplasmic HSP72 was significantly higher in colorectal carcinoma compared with normal and adjacent mucosa (p<0.01). In addition, there was significant increase in HSP72 expression in lymph node-positive compared to node-negative group (p<0.001). Dukes C2 stage of colonic cancer showed significantly higher immunohistochemical score than Dukes B2 and B1 stage groups (p< 0.05 i.e. p< 0.02). There was no relation between expression of HSP72 and degree of tumor differentiation. Using Western blot analyses, we noticed elevated levels of cytosolic HSP70 in colorectal cancer cells compared to normal. Densitometric analysis of blots of plasma membrane HSP70 expression has shown decrease in colorectal cancer cells compared to normal mucosa. According to our results, overexpression of HSP72 in malignant tissues of patients with colorectal carcinoma is related to tumor progression, suggesting that these proteins could play an important role not only in tumorigenesis but also in the development of drug resistance. Further research is necessary to clarify the mechanisms responsible for differential HSP70 expression as well as its definitive role in colorectal cancer.