Showcase of Undergraduate Research and Creative Endeavors (SOURCE)

Effects of Oncogenic MicroRNA on RYBP Expression in Glioblastoma Cells

Glioblastoma multiforme (GBM) is a grade IV malignant tumor of the nervous system. GBMs are primarily cancers of astrocytes, a type of glial cell responsible for axon guidance and synaptic support. Due to a low survival rate and limited, invasive treatment options, the development of targeted therapeutics that address the underlying molecular pathology of GBM is urgently needed. RYBP (RING1- and YY1-binding protein) is a type of Polycomb protein that is downregulated in about 50% of GBM patients, and it behaves as a tumor suppressor in multiple cancers (including lung, breast, and esophageal, among others). Thus, we wondered how GBM cells downregulate RYBP. MicroRNAs are short non-coding RNAs that bind to the 3’ untranslated region (UTR) of complementary mRNA transcripts. MicroRNA binding to an mRNA inhibits protein synthesis. We analyzed the 3’ UTR of RYBP using online prediction software and identified putative binding sites for miR-9-5p, miR-125b-5p, and miR-128-3p. We thus hypothesized that by inhibiting miR-9, 125, and 128 in GBM cells, RYBP expression would be restored. We transfected specific miRNA inhibitors into U-87 cells and isolated total protein after 24 hours. Total protein was then quantified using a Modified Lowry assay and analyzed by SDS-PAGE and Western blot. However, we did not detect RYBP protein expression when cells were treated with any miRNA inhibitor or negative control. Therefore, we cannot conclude that miR-9, 125, or 128 directly regulate RYBP in U-87 GBM cells.