Expression of 70-kDa heat shock protein in oral lesions: marker of biological stress or pathogenicity

We showed differential expression of HSP70 during oral tumorigenesis. The precise functional role of HSP70 overexpression in the pathogenesis of betel and tobacco related oral cancer remains to be determined. To evaluate the utility of HSP70 as an indicator of the biological stress experienced by tumour cells or the malignant potential of oral epithelial lesions and predicting clinical outcome, its expression was assessed in different stages of oral carcinogenesis by immunohistochemical analysis and correlated with clinicopathological parameters. Overexpression of HSP70 protein was observed in 38 of 64 (59%) dysplastic lesions and 92 of 125 (74%) oral squamous cell carcinomas (SCCs) which included 76 of 105 cases (72%) of primary oral SCCs and 16 of 20 (80%) of recurrent oral SCCs. A significant correlation of HSP70 expression was observed with severity of dysplasia (P=0.0006767), poor histological differentiation of primary tumours (P=0.0184348), increase primary tumour size (P=0.0221103) and consumption of betel and tobacco (P<0.01). Follow-up studies showed that in patients with premalignant lesions the median transition time (premalignancy to malignancy) was significantly shorter in HSP70 overexpressing cases than those showing basal level of HSP70 (P=0.012). Oral cancer patients with elevated levels of HSP70 showed decreased median disease-free survival time (no recurrence/metastasis) than those showing basal HSP70 immunoreactivity (P=0.0246). The results suggest that HSP70 expression may not be a mere marker of biological stress but may also be implicated in the pathogenesis of oral cancer.