No abstract

The expression of tight junction proteins is frequently altered in epithelial cancers. The loss of cell-cell adhesion associates with enhanced metastatic potential, which underlies the role of altered expression pattern of tight junction component claudins (CLDNs). Our study assessed the expression of CLDN 1, 2, 3, 4, 7, 8 and 10 in squamous cell carcinoma of the head and neck region (HNSCC) including oropahrynx, larynx, and hypopharynx in comparison to normal epithelial tissue of the same patient. The surgical samples were examined by tissue microarray and immunohistochemistry, the expression was calculated by H-score, which took account of intensity and percentage of positivity as well. Both normal and cancerous tissue proved negative for CLDN 3, 8 and 10. Normal epithelia showed mild expression of CLDN 4, but the minimal positivity disappeared in squamous cancer. In case of CLDN 1 and CLDN 7 we demonstrated significantly increased intensity in cancer, while CLDN 2 showed decreased expression compared with normal epithelium. The normal polarity and distribution of claudins were lost in HNSCC. Moreover, preserved expression of CLDN 2 (but not that of 1 and 7) was associated with better survival, which suggested a potential prognostic role of CLDN 2.

Background: Anti-EGFR antibody therapy is still one of the clinical choices in head and neck squamous cell carcinoma (HNSCC) patients, but the emergence of cetuximab resistance questioned its effectiveness and reduced its applicability. Although several possible reasons of resistance against the antibody treatment and alternative therapeutic proposals have been described (EGFR alterations, activation of other signaling pathways), there is no method to predict the effectiveness of anti-EGFR antibody treatments and to suggest novel therapeutics. Our study investigated the effect of EGFR R521K alteration on efficiency of cetuximab therapy of HNSCC cell lines and tried to find alternative therapeutic approaches against the resistant cells.Methods: After genetic characterization of HNSCC cells, we chose one wild type and one R521K+ cell line for in vitro proliferation and apoptosis tests, and in vivo animal models using different therapeutic agents.Results: Although the cetuximab treatment affected EGFR signalization in both cells, it did not alter in vitro cell proliferation or apoptosis. In vivo cetuximab therapy was also ineffective on R521K harboring tumor xenografts, while blocked the tumor growth of EGFR-wild type xenografts. Interestingly, the cetuximab-resistant R521K tumors were successfully treated with c-MET tyrosine kinase inhibitor SU11274.Conclusion: Our results suggest that HNSCC cell line expressing the R521K mutant form of EGFR does not respond well to cetuximab treatment in vitro or in vivo, but hopefully might be targeted by c-MET tyrosine kinase inhibitor treatment.