Expression of TGFβ-inducible myosin-X predicts survival and chemotherapy resistance in squamous cell lung cancer. Homo sapiens

Squamous cell lung carcinoma (SCC) corresponds to about 25% of all lung cancers. Therapeutic approaches are very limited and platinum-based chemotherapy remains the main treatment option. Despite multiple studies, there are no generally accepted predictive biomarkers for SCC. Transforming growth factor-β (TGFβ) signaling was shown to be implicated in numerous pro-tumorigenic processes, including immune evasion, inflammation and cancer metastasis. In the context of SCC epithelial-to-mesenchymal transition phenotype that is commonly mediated by TGFβ was widely observed in surgically resected specimens. However, the relation between TGFβ-induced changes and SCC progression remains to be elucidated. In the presented work, we combined phenotypic and transcriptome-wide approaches to identify novel predictive biomarkers for SCC. We show that TGFβ treatment activated Smad-mediated signal transduction and resulted in increase of migratory and invasive properties of SK-MES1 cells. Multiple actin cytoskeleton-related proteins, including myosin motor proteins such as Myosin-X, were up-regulated upon TGFβ stimulation. siRNA-mediated knockdown of Myosin-X completely abrogated TGFβ-induced collagen gel invasion. Finally, analysis of mRNA expression in paired surgically resected tissues of 151 SCC patients with corresponding 80-month clinical follow-up, showed that the mRNA expression ratio of Myosin-X in tumor and adjacent non-tumor tissue is predictive for overall survival and chemotherapy resistance independently of tumor stage. Given Myosin-X role in cellular motility and invasion, it can represent a new biomarker for aggressive disease and serve as a potential molecular target for therapeutic intervention in patients with SCC. Overall design: SK-MES-1 cells were treated with TGFb or left untreated and mRNA isolated at t=[0h, 8h, 24h, 48h] in biological triplicates.