LAUSR

Objectives: Oral squamous cell carcinoma (OSCC) is an aggressive malignancy characterized by molecular heterogeneity and locoregional spread associated with high morbidity. Aggressive cancers are thought to arise from populations of cancer initiating cells (CICs) that exhibit the properties of stem cells and drive tumor development, recurrence and resistance to therapy. The transcriptional regulator, β-catenin, has been implicated in OSCC CICs. Nuclear β-catenin has been shown to recruit the chromatin remodeling CREB binding protein (CBP) to drive expression of proliferation and survival genes, as well as genes that maintain stem-like phenotypes. We hypothesized that targeting β-catenin-CBP interaction will inhibit CICs in oral tumors and restore an epithelial phenotype. Methods: To test tumor aggressive potential of OSCC CICs, we used zebrafish as a model system. We isolated CD44+CD24 hi CD29 hi cells fom aggressive HSC-3 OSCC cells by FACS and assayed their ability to drive tumor growth and metastases in zebrafish compared to unsorted and CD44+CD24 low CD29 low cells. In addition, we examined the role of the β-catenin/CBP axis in the aggressive phenotype of these cells. We also assessed whether the β-catenin/CBP axis affected CICs in tumors from immune competent HPV+ mice. Results: Zebrafish injected with subpopulation of cells co-expressing CD44+CD24 hi CD2 hi primitive cell surface markers drove rapid tumor growth and metastases, followed by unsorted and sorted CD44+CD24 low CD29 low . Treatment of CD44+CD24 hi CD29 hi cells with a small molecule inhibitor of the β-catenin-CBP interaction, ICG-001, interfered with tumor growth and metastases in zebrafish. Further, ICG-001 inhibited tumor growth in immunocompetent HPV+ murine model. On a cellular level, ICG-001 promoted membrane localization of β-catenin, enhanced E-cadherin adhesion and restored epithelial phenotype. Significantly, ICG-001 gene signatures tracked with reduced overall patient survival in the cancer genome atlas, TCGA. Conclusion: Our studies indicate that the β-catenin/CBP axis promotes OSCC CICs and that ICG-001 may be an effective therapeutic agent for this malignancy. Support: Evans Center for Interdisciplinary Biomedical Research ARC funding AU 5303015 8000000. Citation Format: Khalid Alamoud, Khikmet Sadykov, Vinay Kartha, Stefano Monti, Anna Belkina, Jennifer Snyder-Cappione, Sara Pai, Maria Kukuruzinska. Targeting β-catenin/CBP signaling in OSCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 803. doi:10.1158/1538-7445.AM2017-803