Abstract 485: Epidermal growth factor-like repeats of Tenascin C promote melanoma cell invasion, possibly by enabling mesenchymal to ameboid migration transition

Abstract

Abstract In malignant melanoma, the most dangerous skin cancer, Tenascin-C (TNC) is overexpressed, especially at the invasive fronts of invasive melanomas. We found that the migration and invasiveness of a set of melanoma cell lines correlates with levels of TNC expression suggesting, surprisingly, that the melanoma cells themselves provide much of this matrix component. Adding TNC to matrices enhanced individual cell migration in cells that did not express much TNC, whereas it did not enhance the rapid motility of the cells expressing high levels. As TNC is a multidomain protein, the signaling pathways that promote this motogenic invasiveness are not obvious. Herein, we examined the potential role of the EGF-like repeats of TNC that have been shown to preferentially activate motogenic-signaling cascades. To analyze the effects of EGFL signaling on melanoma migration and invasion, we overexpressed TNC fragment containing the assembly and EGFL domains of TNC (TNCEGFL). Interestingly, this led to impaired cell migration in in vitro wound healing assays and live cell tracking experiments. This was likely due to a shift in the adhesion-contractility balance during cell migration. TNCEGFL expressing cells presented a spindle-shaped morphology and formed cords in culture. Expression of TNCEGFL delayed melanoma cell attachment and spreading, as determined in cell adhesion and inverted centrifugation assays. This anti-adhesive phenotype was concomitant with increased MLC2 phosphorylation. Inhibition of ROCK activity, which drives transcellular contractility, restored adhesion of TNCEGFL expressing cells and improved migration in 2D. In distinction to the findings in 2D, TNCEGFL expressing cells had higher invasion potential in Matrigel invasion assays, with cells expressing high TNC having rounded “ameboid” morphology, underlying the importance of morphological shifts, and possibly ROCK signaling, in 3D movement through barrier matrices during invasion and dissemination. These results imply that TNCEGFL repeats are involved in melanoma invasion both by directly influencing cell migration and indirectly changing the tumor microenvironment composition, possibly allowing transition from mesenchymal to ameboid migrational mode. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 485. doi:1538-7445.AM2012-485