Beyond the known genome: long non-coding RNAs as novel therapeutic targets and biomarkers for metastatic prostate cancer

Recent evidence indicates that non-coding RNAs (NC-RNAs) play crucial functions in physiological and pathological cellular processes. Long non-coding RNAs (lncRNAs) are the most abundant NC-RNA class, accounting for 10–20,000 genes. Despite this, the role of only a few of them (approxim. 40) has been characterized. Many lncRNAs show a tissue-specific expression pattern and are altered in cancer cells. For this reason, it has been suggested that they may be useful as biomarkers in oncology.

We performed RNA-Seq. on non-metastatic and metastatic prostate cancer (PCa) tumor tissue xenografts. Our analysis revealed 159 up- and 77 down-regulated lncRNAs in the metastatic samples. We validated the differential expression of 7 up-regulated lncRNas in metastatic xenografts (QPCR). Using pooled plasma samples from 3 three patient groups (normal, localized PCa and metastatic PCa) one lncRNA (JUPITER) assayed to date differentiates amongst the three groups. We hypothesize that lncRNAs play critical roles in PCa progression and can be exploited as biomarkers and therapy targets. To address these hypotheses we will: 1: Characterize the function of selected lncRNAs. We will select the most up-regulated lncRNAs in metastatic vs. primary PCa xenografts and assay their expression in a panel of PCa cell lines. Once we identify 2-3 cell lines expressing the highest levels of a transcript, we will silence it using siRNAs. Silenced and control-treated cells will be assayed for proliferation, migration, invasion, apoptosis, and cell cycle progression. 2: Measure by QPCR the expression of selected lncRNas on RNA extracted from freshly frozen prostate samples (normal prostate, prostate intraepithelial neoplasia, local and metastatic PCa). For each gene, we will statistically compute correlations with clinico-pathological variables (grade, stage, PSA level). 3: Further analyze lncRNAs as biomarkers. The expression of JUPITER (and other differentially expressed lncRNAs) will be assayed in individual plasma samples from patients with different PCa stages, in order to estimate the optimal threshold values for early detection of metastatic PCa (ROC curve).

While localized PCa is a treatable disease, progression to a metastatic and drug-resistant cancer accounts for 4000 deaths annually in Canada. Understanding the mechanisms of Pca progression and identifying new molecular markers and therapeutic targets will allow better disease management and ultimately reduce deaths. In brief, we discovered a long non-coding RNA (PCAT18) that is expressed exclusively by prostate cancer cells and is required for prostate cancer cell growth and motility. This gene can be used as a biomarker and as a therapeutic target for metastatic prostate cancer.