Investigation of the effects of epidermal growth factor receptor inhibition on claudins in lung cancer cell lines

Tight junctions are membranous structures present in epithelial, endothelial and mesothelial cells. It is a multiprotein complex that links between adjacent cells of both epithelial and endothelial cell layers. It has been reported that tight junction proteins of the pump inhibitor YM201636 inhibit the endocytic recycling of CLDN1 and CLDN2 and disrupt their tight junctions. EGFR is a transmembrane glycoprotein present in the cell membrane, and there is a critical importance in the regulation of cell proliferation. To inhibit EGFR function in cancer cells, molecules that inhibit intracellular tyrosine kinase signaling or neutralizing antibodies against EGFR and its ligands are used. Canertinib (CI-1033) is a tyrosine kinase inhibitor that inhibits EGFR, HER2 and HER4 invitro conditions. In this thesis study, it is aimed to elucidate the relationship between EGFR and claudins, which is a structural component of tight junctions. For this, EGFR mutant and wild-type lung cancer cell lines HCC827 and H1299 were used, and the cytotoxic and apoptotic effects of CI-1033 and YM201636 agents were investigated and their effects on EGFR and claudin mRNA and protein levels were investigated. XTT in cytotoxicity analyzes, Annexin / PI in apoptosis assays, quantitative RT-PCR and western blot methods in determining mRNA and protein levels were used. The IC50 for CI-1033 was determined to be 2.170 and 16.42 μM for the HCC827 and H1299 cell lines respectively. YM201636 showed cytotoxic effect at 11.07 μM in the EGFR mutant HCC827 cell line whereas EGFR did not affect cell viability at 75 μM concentration in wild-type H1299 cells. The agents YM201636 caused a significant increase in EGFR, CLDN1 and CLDN3 mRNA expression levels in HCC827 cells, and in H1299 cells, the level of CLDN1 mRNA decreased significantly after administration of YM201636. CI-1033 and YM201636 inhibitors exerted different effects on CLDN expression in EGFR mutant and wild-type cell lines. Key Words: lung cancer; tight junction; claudins; EGFR