Abstract B15: Transforming growth factor β type III (TβRIII/Betaglycan) suppresses canonical Wnt signaling in ovarian cancer

Ovarian cancer remains the deadliest gynecologic malignancy and the fifth leading cause of death from cancer in women[1]. Transforming growth factor β Type III (TβRIII/Betaglycan) receptor is a ubiquitously expressed co-receptor for the TGF-β ligand superfamily[2] whose expression is significantly decreased or lost in human epithelial ovarian tumors compared to normal tissue, with loss of TβRIII expression correlating with tumor grade and ovarian cancer progression[3]. TβRIII has increasing roles in suppressing cancer progression via cell motility[4], cell adhesion[5], and cell differentiation[2], largely independent of its TGF-β co-receptor functions[2, 3]. Structurally, TβRIII is a transmembrane proteoglycan containing both heparan sulfate and chondroitin sulfate glycosaminoglycan (GAG) chain modifications in its extracellular domain[5] that can interact with non-TGF-β family members, namely FGF2, via its GAG chains to regulate tumorigenesis[2].There is increasing evidence that Wnt glycoproteins that play complex roles in cancer[1, 6-11] have a high affinity for GAG chains on proteoglycans[12, 13]. Thus, we have initiated studies to determine the possible role of TβRIII on canonical Wnt3a signaling in ovarian cancer. Using a combination of cell signaling and biochemical approaches in ovarian cancer models, we find that TβRIII suppresses Wnt3a signaling by binding Wnt3a via its heparan sulfated GAG chains, which leads to perturbation of the LRP6/Frizzled/Wnt3a complex required for Wnt3a signaling activation. Reciprocal overexpression and knockdown of TβRIII in ovarian cancer cell lines reveal that TβRIII is a strong suppressor of canonical Wnt3a signaling, largely independent of TβRIII’s role as a TGF-β co-receptor. Finally, we provide evidence, via TCF/LEF-sensitive reporter activity[14], that TβRIII chondroitin sulfate chains can promote Wnt3a signaling in the absence of its heparan sulfate chains. These results indicate an intricate mode of Wnt3a signaling regulation by TβRIII/Betaglycan, mediated by distinct functions of its heparan and chondroitin chains. Our studies suggest a critical role for TβRIII’s heparan and chondroitin sulfated GAG modifications in modulating Wnt3a signaling and, more importantly, a possible therapeutic approach to address malfunctions in the Wnt signaling pathways that lead to ovarian carcinogenesis. Citations: 1. Arend, R.C., et al., The Wnt/beta-catenin pathway in ovarian cancer: a review. Gynecol Oncol, 2013. 131(3): p. 772-9. 2. Knelson, E.H., et al., Type III TGF-beta receptor promotes FGF2-mediated neuronal differentiation in neuroblastoma. J Clin Invest, 2013. 123(11): p. 4786-98. 3. Gatza, C.E., S.Y. Oh, and G.C. Blobe, Roles for the type III TGF-beta receptor in human cancer. Cell Signal, 2010. 22(8): p. 1163-74. 4. Mythreye, K., et al., TbetaRIII/beta-arrestin2 regulates integrin alpha5beta1 trafficking, function, and localization in epithelial cells. Oncogene, 2013. 32(11): p. 1416-27. 5. Mythreye, K. and G.C. Blobe, Proteoglycan signaling co-receptors: roles in cell adhesion, migration and invasion. Cell Signal, 2009. 21(11): p. 1548-58. 6. Tung, E.K., et al., Upregulation of the Wnt co-receptor LRP6 promotes hepatocarcinogenesis and enhances cell invasion. PLoS One, 2012. 7(5): p. e36565. 7. Qi, L., et al., Wnt3a expression is associated with epithelial-mesenchymal transition and promotes colon cancer progression. J Exp Clin Cancer Res, 2014. 33(1): p. 107. 8. Lavergne, E., et al., Blocking Wnt signaling by SFRP-like molecules inhibits in vivo cell proliferation and tumor growth in cells carrying active beta-catenin. Oncogene, 2011. 30(4): p. 423-33. 9. Verras, M., et al., Wnt3a growth factor induces androgen receptor-mediated transcription and enhances cell growth in human prostate cancer cells. Cancer Res, 2004. 64(24): p. 8860-6. 10. Gatcliffe, T.A., et al., Wnt signaling in ovarian tumorigenesis. Int J Gynecol Cancer, 2008. 18(5): p. 954-62. 11. Boyer, A., A.K. Goff, and D. Boerboom, WNT signaling in ovarian follicle biology and tumorigenesis. Trends Endocrinol Metab, 2010. 21(1): p. 25-32. 12. Ai, X., et al., QSulf1 remodels the 6-O sulfation states of cell surface heparan sulfate proteoglycans to promote Wnt signaling. J Cell Biol, 2003. 162(2): p. 341-51. 13. Capurro, M., et al., Glypican-3 binds to Frizzled and plays a direct role in the stimulation of canonical Wnt signaling. J Cell Sci, 2014. 127(Pt 7): p. 1565-75. 14. Veeman, M.T., et al., Zebrafish prickle, a modulator of noncanonical Wnt/Fz signaling, regulates gastrulation movements. Curr Biol, 2003. 13(8): p. 680-5. Citation Format: Laura M. Jenkins, Archana Varadaraj, Haley Flores, Mythreye Karthikeyan. Transforming growth factor β type III (TβRIII/Betaglycan) suppresses canonical Wnt signaling in ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference: Developmental Biology and Cancer; Nov 30-Dec 3, 2015; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(4_Suppl):Abstract nr B15.