Abstract 4547: Enhanced anti-tumor effect of WNT pathway antagonists in combination with taxanes

Abstract

Abstract The Wnt/beta-catenin pathway, which signals through the Frizzled (FZD) receptor family and several co-receptors, has long been implicated in cancer. We have previously demonstrated that inhibition of WNT/beta-catenin signaling by vantictumab (anti-FZD) or OMP-54F28 (FZD8-Fc) inhibits tumor growth, decreases tumorigenicity and induces differentiation in solid tumors. The anti-tumor effect of our Wnt antagonists is most evident in combination with chemotherapeutic agents. We sought to determine if the anti-tumor effect of Wnt pathway inhibitors varied with different chemotherapeutic agents. We compared the growth inhibitory effect of vantictumab and OMP-54F28 with either taxanes (paclitaxel and nab-paclitaxel) or with DNA synthesis inhibitors (gemcitabine and carboplatin) in patient-derived tumor xenografts. In a model for pancreatic ductal carcinoma, vantictumab with nab-paclitaxel was more efficacious than vantictumab with gemcitabine in inhibiting tumor growth and Wnt target gene expression (at doses of nab-paclitaxel and gemcitabine that were equivalent in their single-agent growth-inhibitory effects). Histologic analysis indicated that nab-paclitaxel increased mitotic cells and beta-catenin levels. Importantly, the addition of vantictumab to nab-paclitaxel reversed the nab-paclitaxel-induced increase in mitotic cells and beta-catenin expression. An independent experiment in a serous ovarian cancer xenograft model also showed enhanced anti-tumor activity when combining OMP-54F28 with either paclitaxel or nab-paclitaxel compared to the combination with carboplatin. A potential mechanism to account for these results involves on the observation that Wnt/beta-catenin signaling is under cell cycle control and peaks at the G2/M phase. Taxanes inhibit microtubule function and block the cell cycle at G2/M. In contrast, other chemotherapeutic agents, such as platinum compounds and nucleoside analogs, inhibit DNA synthesis and block cell proliferation at S phase. We hypothesize that combination of Wnt blockade with chemotherapeutic agents, such as taxanes, that induce G2/M arrest may result in optimal anti-tumor activity. Citation Format: Wan-Ching Yen, Marcus M. Fischer, John Lewicki, Austin Gurney, Timothy Hoey. Enhanced anti-tumor effect of WNT pathway antagonists in combination with taxanes. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4547. doi:10.1158/1538-7445.AM2014-4547