UNRAVELING PATHWAYS THAT DRIVE CISPLATIN CHEMORESISTANCE IN ORAL CARCINOMA CELL LINES

Abstract

<h3>Objectives</h3> Investigate the mechanisms that contribute to cancer stem cells (CSCs) accumulation and chemoresistance phenotype in cisplatin chemoresistant cell lines. <h3>Study Design</h3> CAL27 and SCC9 cell lines were treated with cisplatin until the establishment of the chemoresistance (CisR). RNA-seq and gene ontology (GO) analysis were performed to identify genes and biologic processes modified by chemoresistance. CSC accumulation was assessed by flow cytometry and sphere formation. Aggressiveness was investigated by clonogenic assay, MTS assay, Ki-67 immunostaining, wound healing assay, invasion, and tumor growth in a xenograft model. Epithelial mesenchymal transition (EMT) was detected by changes in E-cadherin and vimentin. <h3>Results</h3> The transcriptome of chemoresistant cell lines revealed upregulation of genes involved with proliferation, cell migration, and stemness, including TGFβ-2 and TGFβR-2; an increase in inflammatory processes; and an association with activation of EMT. RNA-seq also revealed downregulation of genes related to adhesion and drug metabolism. Chemoresistant cells presented accumulation of CSCs as well as increased proliferation, migration, and invasion. Increases in vimentin and decreases in E-cadherin were observed in CisR cell lines, suggesting activation of EMT. For CAL27 CisR we also observed a high in vivo tumorigenic potential. <h3>Conclusions</h3> A reprogramming in the expression of genes signaling stemness and tumor aggressiveness drives chemoresistance induced by cisplatin.