Abstract 1926: The effect of Beta-Catenin upon the tumor molecular biology and growth in HNSCC: role of cancer stem cells

Abstract

Abstract Overview: Head and neck squamous cell carcinomas (HNSCC) are the sixth most prevalent type of malignancy worldwide. Recent reports have demonstrated that nearly every tumor contain a small subpopulation of cells called cancer stem-like cells (CSCs), which are responsible for tumor maintenance, metastasis relapse and therapeutic resistance. Recent studies demonstrate that even established HNSCC cell lines contain a definite sub-population of CSC providing us with the opportunity to discerning their roles in progression, treatment, and relapse of the disease. Background: We have previously demonstrated that a definite subpopulation of CSCs exists in most HNSCC cell lines. Significant differences were seen between the HPV+ and HPV- subtypes, confirmed by analyses of stem-ness genes and EMT markers. In vivo tumor xenograft formation has established the heightened tumorigenicity of CSCs. We investigated the molecular and functional roles of Beta-catenin in HNSCC CSCs by shRNA knock down and then subjecting the knocked down (KD) cells to various molecular analysis and in-vivo tumor formations in nude mice. We have also identified SOX2 as a down-stream effector gene that could exert the tumor promoting effects of Beta-catenin. The promoter region of the Sox2 gene was found to contain several putative Beta-catenin binding sites. Methods & Results: After identifying CSCs by in-vitro Sphere Forming (SFA) capabilities and molecular gene signatures, we have knocked down both Beta-catenin and Sox2 in both HPV+ and HPV- HNSCC cell lines (UMSCC47 and UMSCC6). SFA with the Beta-catenin KD-cells depicts a 50% decrease in sphere formation ability. Molecular analyses show lower expression of stemness genes: Sox2 (~ 3 fold) and Oct4 (~ 2 fold); metastatic genes: N-cadherin (~ 2.5 fold), Vimentin (~ 3 fold), Twist (~ 4 fold), Snail (~ 2.5 fold), Slug (~ 2.5 fold) and Hif-1alpha (~ 1.5 fold). Two tissue microarrays (TMA) were stained for Oct4, Sox2, and CD44 gene expression by multiplex RNA in situ hybridization. Nearly all tumor cells expressed high levels of CD44. Cells high in both Oct4 and Sox2 were quantified within duplicate cores and correlated with local control (TMA-1) and radiation response (TMA-2). Conclusions: Initial molecular analyses depicted that upon loss of Beta-catenin, the crucial stem-ness genes are negatively affected and the loss of stem-ness is also reinforced by decreased sphere formations. Both the metastatic and hypoxic gene signatures are markedly altered. We expect similar outcomes with the in-vivo tumor formations in nude mice. Citation Format: Austin Maas, Anirban Chatterjee, Lisa Sudmeier, Kwang Nickel, Randall J. Kimple. The effect of Beta-Catenin upon the tumor molecular biology and growth in HNSCC: role of cancer stem cells [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 1926. doi:10.1158/1538-7445.AM2017-1926