518 Genetic and Epigenetic Alterations of PTPRD in Hepatocellular Carcinoma

Introduction: Genomic instability is a hallmark of ovarian cancer. MicroRNAs (miRNAs) are small RNA molecules that negatively regulate gene expression, and are often dysregulated in cancer. The aim of this study is to determine whether copy number variations (CNV) lead to altered miRNA expression and downstream effects on target gene expression in serous epithelial ovarian cancer (SEOC). Materials and Methods: CN, mRNA and miRNA expression profiling was performed on 4 SEOC (OV167, OV202, OVCAR-3, PE01) and 1 normal (HOSE) cell lines using Affymetrix Cytogenetic 2.7M Arrays, Affymetrix GeneChip Gene 1.0 ST arrays and Exiqon MiRCURY LNA arrays respectively. Chromosomal positioning of miRNAs was performed using Bowtie v 0.12.7 [1]. Results and Discussion: We determined that 60% (361/605) of miRNAs assessed were in regions of CNV in at least 2 cancer cell lines. Of these miRNAs, 32% (115/361) had changes in expression levels that correlated with CNV. One of these, miR-23a, is predicted to target AXL, an oncogenic receptor tyrosine kinase upstream of the PI3K/mTOR signalling pathway. AXL is over-expressed in ovarian cancer, and an inverse relationship was identified between the expression of AXL and miR-23a in 2 of the 4 cell lines. Axl has been previously reported to be over-expressed in 73% of ovarian tumour samples [2]. Transient transfection of miRNA mimics (Ambion) into ovarian cancer cell lines confirmed AXL down regulation after miR-23a addition. Conclusion: We demonstrate that approximately one third of miRNAs that are located in regions of CNV have altered expression which correlates with the chromosomal change. We conclude that genomic instability may contribute to miRNA dysregulation in ovarian cancer.