Many studies in cell biology have addressed the roles of HSPs as molecular chaperones, including protein folding and unfolding, translocation, and prevention of inappropriate protein aggregation [
7,
19]. These findings show an association between HSPs and cell proliferation and the prevention of apoptosis [
20]. While HSP expression has been recognized as a factor of prognostic value in certain tumors, the data are limited and the results often contradictory. For example, inducible HSP72 has been shown to be a negative prognostic factor for disease-free survival (DFS) in patients with lymph node-negative breast cancer [
21], whereas other authors have shown that HSP72 positively correlates with estrogen receptors and inversely with expression of mutant p53 [
22]. Santarosa et al. demonstrated prognostic implications of expression of HSP70 in patients suffering from renal cancer [
23]. Although some evidence indicates that HSPs are involved in various aspects of cell transformation and immune response against cancer [
24], their biological role and its implications for the clinical course in cancer patients are not clear. In OSCC, the number of positive nodes, macroscopic extracapsular spread, and tumor infiltration of the resection margins have been described as significant prognostic factors [
1,
2]. Studies concerning HSP70 as a prognostic factor in esophageal carcinoma suggest that reduction of HSP70 expression is significantly correlated with poor prognosis [
16,
25]. Although several studies have been performed to elucidate the relationship between HSPs and tumors in various organs, to our knowledge, there are comparatively few reports related to OSCC. Sugarman et al. reported that HSP70 expression is not a definitive marker of oral malignancy or malignant potential [
26]. In terms of prognostic significance, Ito et al. examined 24 specimens of patients suffering from OSCC. Although HSP immunohistochemistry revealed changes in HSP expression during tumorigenesis of squamous epithelium of the tongue, there was no correlation between HSP staining and survival period, stage, lymph node metastasis, histological grade, or p53 immunostaining [
27]. These results are in line with those of Gandour-Edwards et al, who found that HSPs were expressed in normal upper respiratory tract squamous mucosa, and their role in carcinoma thus remains unclear. None of the markers (p53, HSP27, or HSP70) demonstrated prognostic significance for 5-year survival. We confirm the previously identified association of cervical lymph node metastases with decreased survival [
5].
The results of the previously published data are not in line with the findings of the present study. In this study, we demonstrated that for patients suffering from T2-tumors, positive expression of HSP70 results in a significantly lower mortality risk compared with patients with negative expression. The main difference regarding the study design may be that, in contrast to previous studies, our patient population was divided according to tumor stages in the different T-stadium of the tumor. The purpose of this division was to analyze the prognostic significance of each T-stadium separately. Considering the entire patient group, our findings would suggest the same result: HSP70 has no prognostic implications for our patients. Also in the seperated T3- and T4-tumors, HSP 70 did not show any prognostic significance. Only after focusing on patients suffering from T2-tumors could a significant difference be detected. The survival of patients suffering from T2 tumors with positive HSP70 expression was 8 times higher than that for patients with negative HSP70 expression.