HSP70 induces TLR4 signaling in oral squamous cell carcinoma: an immunohistochemical study.

Objectives: Toll like receptors play an important role in innate and adaptive immune responses. Heat shock proteins play a significant role in cell proliferation, differentiation and oncogenesis. HSP70 acts as one of the ligands of TLR4 and binds to it in a CD14 dependent fashion to bring about proinflammatory cytokine production leading to an anti-tumor response. On the contrary, TLR4 has been implicated in carcinogenesis by secretion of anti-apoptotic proteins. Thus the aim of this study was to compare and correlate the association of HSP70 and TLR4 in various grades of oral squamous cell carcinoma.
Study Design: Twenty-seven cases of oral squamous cell carcinoma were considered. Ten cases each of well-differentiated (WDSCC) and moderately differentiated (MDSCC), 7 cases of poorly differentiated carcinoma (PDSCC) were considered. Sections were stained for HSP70 and TLR4 and were evaluated for staining degree and intensity.
Results and Conclusion: Positive expression of both HSP70 and TLR4 was found in all cases of WDSCC and MDSCC, whereas in PDSCC out of 7 cases only 6 showed positivity for TLR4 and 4 cases showed positivity for HSP70. Those cases that were positive for TLR4, also showed positivity for HSP70. HSP70 acts as a ligand and binds to TLR4 thus activating the My88 pathway resulting in production of proinflammatory cytokines, chemokines, growth factors etc., enhancing anti-cancer immunity in the early stages of disease. In later stages, TLRs expressed on cancer cells can produce anti-apoptotic proteins contributing to carcinogenesis and cancer cell proliferation.