We sought to elucidate the role of a potentially oncogenic microRNA, microRNA-10b (mir-10b), in mediating the pathology of glioblastoma multiforme (GBM). MicroRNAs are small noncoding RNAs that play a critical role in developmental and physiological processes and are implicated in the pathogenesis of several human diseases including cancer. MicroRNAs function by regulating target gene expression post-transcriptionally. We have previously assessed the expression pattern of 241 mature human microRNAs in the NCI60 panel of cell lines and in a set of corresponding normal tissues (Gaur et al., 2007, Cancer Research. 67(6):2456-68). We found that microRNA expression patterns mark specific biological characteristics of tumors and/or mediate biological activities important for their pathobiology. In CNS tumor-derived cell lines, we identified mir-10b as a candidate oncogene, as it is expressed at higher levels in human GBM lines an primary GBM tissue than it is in normal brain tissue. Using several target prediction algorithms we identified a member of the homeobox family, Homeobox D10 (HOXD10), as a potential target of mir-10b. Our in vitro studies demonstrate that down regulation of mir-10b in GBM-derived cell lines results in increased expression levels of HOXD10. Additionally, our data indicate that down-regulation of mir-10b in human GBM lines leads to decreased proliferation and decreased anchorage independent colony formation in soft agar. Importantly, using a xenograft model in immune-deficient nude mice, we have observed human that GBM lines in which mir-10b expression is inhibited exhibit decreased tumor formation and growth in vivo. Furthermore, the decreased colony formation in soft agar observed as a result of mir-10b inhibition in GBM-derived cell lines is significantly antagonized by expression of siRNAs complementary to HOXD10 mRNA. Also, over expression of HOXD10 in GBM cell lines results in differentiation and decreased proliferation. Further experiments are ongoing to identify the specific role of HOXD10 in mediating the pathologic characteristics of GBM. An understanding of the pathways mediated by HOXD10 signaling may provide novel opportunities for therapeutic intervention. The National Brain Tumor Society (ABG) and the Theodora B. Betz Foundation (MAI) supported this work.

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 2100.