Abstract 2096: The role of microRNA-1 as a candidate tumor suppressor in cutaneous squamous cell carcinoma

Abstract

Abstract Cutaneous squamous cell carcinoma (SCC) is the second most common form of skin cancer, affecting over 250,000 people in the United States annually. Using miRNA expression arrays, we identified lower levels of microRNA-1 (miR-1) expression in skin from FVB/NJ mice, which are susceptible to chemically-induced skin cancer, compared to skin from Spr/EiJ mice, which are resistant to chemically-induced skin cancer. Additionally, murine SCC cell lines showed greatly reduced levels of miR-1 compared to normal skin. We hypothesize that decreased expression of miR-1 in susceptible mice and SCC cell lines suggests a possible role of miR-1 as a tumor suppressor in skin. To test this hypothesis, we transfected a precursor for miR-1 into a murine SCC cell line, A5, and measured proliferation and cell viability via an MTT assay at 24, 48, and 72 hours post-transfection. The growth rate for cells transfected with miR-1 was significantly decreased at 48 to 72 hours post-transfection relative to those mock-transfected cells and corresponded to miR-1 expression levels. These data are consistent with our hypothesis that miR-1 may act as a tumor suppressor in the skin. Using in silico prediction programs, we identified a number of putative targets of miR-1. The transcription factor oncogene, Ets1, emerged as an interesting potential direct target of miR-1. Ets1 has three predicted target binding sites for miR-1. Quantitative PCR and Western analyses revealed decreased Ets1 mRNA and protein expression in A5 cells transfected with miR-1 compared to mock-transfected A5 control cells. Ets1 mRNA expression is also decreased in a normal keratinocyte cell line, C5N, compared to A5 cells. From these experiments we showed that Ets1 expression shows an inverse correlation with miR-1 levels. These results suggest Ets1 is regulated by miR-1. Future studies will determine whether Ets1 is a direct target of miR-1. We will also clarify the role of Ets1 in SCC cell proliferation and migration and identify other tumor-related phenotypes associated with miR-1. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2096.