Matrix Stiffening and EGFR Cooperate to Promote the Collective Invasion of Cancer Cells.

In squamous cell carcinoma (SCC), tissue invasion by collectively invading cells requires physical forces applied by tumor cells on their surrounding extracellular matrix (ECM). Cancer-related ECM is composed of thick collagen bundles organized by carcinoma-associated fibroblasts (CAF) within the tumor stroma. Here, we show that SCC cell collective invasion is driven by the matrix-dependent mechano-sensitization of EGF signaling in cancer cells. Calcium (Ca2+) was a potent intracellular second messenger that drove actomyosin contractility. Tumor-derived matrix stiffness and EGFR signaling triggered increased intracellular Ca2+ through CaV1.1 expression in SCC cells. Blocking L-type calcium channel expression or activity using Ca2+ channel blockers verapamil and diltiazem reduced SCC cell collective invasion both in vitro and in vivo These results identify verapamil and diltiazem, two drugs long used in medical care, as novel therapeutic strategies to block the tumor-promoting activity of the tumor niche.Significance: This work demonstrates that calcium channels blockers verapamil and diltiazem inhibit mechano-sensitization of EGF-dependent cancer cell collective invasion, introducing potential clinical strategies against stromal-dependent collective invasion.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/18/5229/F1.large.jpg Cancer Res; 78(18); 5229-42. ©2018 AACR.

Epigenetic switch drives the conversion of fibroblasts into proinvasive cancer-associated fibroblasts.

Carcinoma-associated fibroblasts (CAF) mediate the onset of a proinvasive tumour microenvironment. The proinflammatory cytokine LIF reprograms fibroblasts into a proinvasive phenotype, which promotes extracellular matrix remodelling and collective invasion of cancer cells. Here we unveil that exposure to LIF initiates an epigenetic switch leading to the constitutive activation of JAK1/STAT3 signalling, which results in sustained proinvasive activity of CAF. Mechanistically, p300-histone acetyltransferase acetylates STAT3, which, in turn, upregulates and activates the DNMT3b DNA methyltransferase. DNMT3b methylates CpG sites of the SHP-1 phosphatase promoter, which abrogates SHP-1 expression, and results in constitutive phosphorylation of JAK1. Sustained JAK1/STAT3 signalling is maintained by DNA methyltransferase DNMT1. Consistently, in human lung and head and neck carcinomas, STAT3 acetylation and phosphorylation are inversely correlated with SHP-1 expression. Combined inhibition of DNMT activities and JAK signalling, in vitro and in vivo, results in long-term reversion of CAF-associated proinvasive activity and restoration of the wild-type fibroblast phenotype.