The in vitro effect of poly (I:C) on cell morphology of a metastatic pharyngeal cell line

Toll-like receptor 3 (TLR3) belongs to a family of TLRs, which are activated by ligands of bacterial and viral origin. Following ligation, TLRs induce different cellular responses including immune response, apoptosis, cell proliferation, cell migration, etc. TLR3 is induced by dsRNA or its analogue poly (I:C). In our previous research, we have noticed the morphological change in Detroit 562 cells after poly (I:C) stimulation resulting in mesenchymal phenotype. Here we have studied the pathways involved in the observed phenomenon by analyzing cell morphometric parameters. We have demonstrated that the observed changed morphology is not a consequence of increased apoptosis. Rho inhibitor also did not abrogate the induced morphological change, however, it induced the formation of short sheet-like sprouts and the combination of Rho inhibitor and poly (I:C) induced lamellipodia-like structures and more filopodia-like thin antennae sprouts. Finally, we have shown that Rac1 activation and epithelial to mesenchymal transition (EMT) markers (vimentin, fibronectin and Snail) are increased after poly (I:C) stimulation. Since we have previously shown increased migration of Detroit 562 cells after poly (I:C) stimulation, we conclude here that this and the morphological change are the result of EMT and Rac1 activation.