Abstract 1551: Soluble tissue transglutaminase modulates cellular adhesion to matrix and peritoneal metastasis in ovarian cancer

Abstract

Abstract Background: Tissue transglutaminase (TG2) is a secreted protein that binds fibronectin (FN) and exerts protein transamidating activity in the presence of Ca2+. We previously reported that TG2 is upregulated in ovarian cancer (OC) cells and enhances intraperitoneal (ip) metastasis. TG2 is secreted abundantly in OC ascites, yet the function of soluble (s) TG2 remains unknown. We hypothesized that sTG2 acts as a permissive factor in the ECM by promoting cancer cell proliferation and adhesion to the matrix. Materials and Methods: Recombinant his6-tagged full length human TG2 and its inactive enzymatic mutant C277S were purified by immobilized metal (Co2+) affinity and anion exchange chromatography. OV90 and A2780 OC cells that do not express endogenous TG2 were used. Solid phase adhesion assay measured adhesion to ECM proteins, MTT assay measured cell proliferation and an ip xenograft model quantified tumor formation and metastasis. Results: S-TG2 enhanced cell adhesion to FN (p = 0.01) and vitronectin (VN, p = 0.01), but not to collagen and laminin. A neutralizing antibody to α5β1 and to αVβ3 blocked sTG2 induced cell adhesion to FN or to VN, respectively, suggesting that sTG2 modulates cell interaction with the matrix via integrins. Digestion of FN with matrix metallo-proteinase 2 blocked OC cell adhesion to digested fragments of FN, while addition of sTG2 restored OC cells’ binding to this protease-digested matrix (p = 0.02). This suggests that the soluble enzyme may facilitate the interaction of OC cells with a protease-remodeled matrix remodeled, similar to the tumor ECM. Enzymatically inactive soluble C277S TG2 enhanced OC cell adhesion to FN to the same extent as wild type TG2. In contrast, an antibody raised against the FN-binding domain of TG2 blocked sTG2 induced OC cell adhesion to FN (p =0.01). These data suggest that the interaction between TG2 and FN, but not the transamidating activity, is important to sTG2-mediated cell interaction with the ECM. When added to conditioned media, sTG2 (2.5ug/mL) increased OC cell proliferation by 20% (p = 0.01). Biweekly ip inoculation of 2.5ug sTG2 increased peritoneal dissemination of OV90 cells in nude mice (11.38 vs. 27.75, p = 0.02), but did not affect tumor volume (412.3 vs. 578.2 mm3, p = 0.34). Conclusions: These data demonstrate that sTG2 increases OC cell adhesion to the ECM and peritoneal metastasis. The key mechanism involved in this process is the interaction between sTG2, FN, and integrins. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1551. doi:10.1158/1538-7445.AM2011-1551