Heat shock protein 47 expression in oral squamous cell carcinomas and upregulated by arecoline in human oral epithelial cells

Abstract

Heat shock protein 47 (HSP47) is a product of CBP2 gene located at chromosome 11q13.5, a region frequently amplified in human cancers. Areca quid chewing is a major risk factor of oral squamous cell carcinoma (OSCC). The aim of this study was to compare HSP47 expression in normal human oral epithelium and OSCC and further to explore the potential mechanisms that may lead to induce HSP47 expression. Thirty-two OSCC specimens and ten normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry. The oral epithelial cell line OC2 cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, glutathione precursor N-acetyl-l-cysteine (NAC), extracellular signal-regulated protein kinase (ERK) inhibitor PD98059, phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, cyclooxygenase-2 inhibitor NS-398, and tyrosine kinase inhibitor herbimycin A were added to find the possible regulatory mechanisms. HSP47 expression was significantly higher in OSCC specimens than normal epithelium (P<0.05). No significant difference in HSP47 expression was observed with respect to age, sex, T category, stage, and differentiation (P>0.05). The lower HSP47 expression was associated with lymph node metastasis (P=0.015). Arecoline was found to elevate HSP47 expression in a dose- and time-dependent manner (P<0.05). The addition of NAC, PD98059, LY294002, NS398, and herbimycin A markedly inhibited the arecoline-induced HSP47 expression (P<0.05). Our findings demonstrated that HSP47 expression is significantly upregulated in areca quid chewing-associated OSCCs. HSP47 could be used clinically as a marker for lymph node metastasis of oral carcinogenesis. In addition, arecoline-induced HSP47 expression was downregulated by NAC, PD98059, LY294002, NS398, and herbimycin A.