Abstract 216: Attenuation of cancer-initiating cells stemness properties by abrogating S100A4 calcium binding ability in head and neck cancers

Abstract

Abstract Background: Epithelial-mesenchymal transition (EMT) is a process that epithelial cells acquire a migratory mesenchymal phenotype or stem cell (SC) properties. Further, up regulation of Vimentin and Nanog is closely related to EMT and stemness properties, respectively. S100A4, a member of calcium-binding proteins, is competent to induce EMT and directly controlled by Wnt/β-catenin signaling pathway. Calcium binding activity of S100A4 has been highly associated with the regulation of downstream targets and development of a metastatic phenotype. In addition, we recently demonstrate that S100A4 plays a crucial role in the maintenance of head and neck cancer-initiating cells (HN-CIC) population. Moreover, inhibition of S100A4 decreased the HN-CICs stemness and self-renewal property, both in vitro and in vivo. However, the regulation of S100A4 and the molecular targets to control HN-CICs stemness capability are remained unclear. Methods: In this study, we establish the stable cells harboring the mutations with calcium-binding sites or a deletion of the last 15 amino-acid residues of S100A4 in head and neck squamous cell carcinomas (HNSCC) to investigate the mechanism of S100A4 enhances stemness properties of CICs through in vitro and in vivo assays. Results: We found that cells expressing the mutant S100A4 result in decreasing of anchorage independent growth ability when it compare to the cells harboring wild-type S100A4 in HNSCC. The immunoblot analyses showed that wild-type S100A4 not only increased the protein level of Vimentin and Nanog but also decreased the expression of E-cadherin. Inversely, the mutant S100A4 reduced the protein level of Vimentin and Naong and increased the expression E-cadherin in HNSCCs. To further investigate the connection between S100A4 and stemness determinants, we enriched the HN-CICs from wild-type S100A4 and mutants S100A4 HNSCC cells, respectively, by sphere formation. The results showed that the mutants S100A4 sphere cells displayed much less stemness markers, the cell surface CD133 and GRP78. Finally, the tumorigenic ability of wild-type S100A4 and mutants S100A4 HNSCC cells, which would be enhanced by acquisition of stemness properties, is further under examination by xenotransplantation. Conclusion: Our study provides a hint that Ca2+ binding ability of S100A4 plays an important role in the maintenance of self-renewal and stemness properties of HN-CICs. The study of how modulators of Ca2+ dependent processes operate the stem-like properties and the tumorigenicity of HN-CICs are needed for further elucidation. Citation Format: Li-Hao Cheng, Jeng-Fan Lo. Attenuation of cancer-initiating cells stemness properties by abrogating S100A4 calcium binding ability in head and neck cancers. [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 216. doi:10.1158/1538-7445.AM2014-216