Abstract 2452: Dysregulated expression of the human long noncoding RNAGHSROSmay influence prostate cancer progression and resistance to docetaxe

Long noncoding RNAs (lncRNAs) play key regulatory roles in cancer progression and are novel therapeutic targets. We recently discovered the lncRNA gene, GHSROS (GHSR opposite strand), on the antisense DNA strand of the ghrelin receptor gene (GHSR). Here, we studied the expression and function of GHSROS in prostate cancer. Interrogation of microarray and RNA-seq data sets revealed that (similar to other lncRNA oncogenes) GHSROS is actively transcribed, although expressed at very low levels in cancer cell lines and tissues. By quantitative RT-PCR we demonstrate that GHSROS is highly expressed in a subset of high-grade prostate cancers (~11.4%). Moreover, the lncRNA is upregulated in high Gleason-score prostate tumors in two clinical data sets. Forced GHSROS overexpression significantly increased in vitro cell proliferation and migration of PC3, DU145, and LNCaP prostate cancer cell lines (P ≤ 0.05, Student's t-test). Increased cell proliferation observed in GHSROS-overexpressing prostate cancer cell lines was recapitulated in PC3, DU145, and LNCaP prostate cancer xenografts in NOD/SCID mice. Cell survival was significantly increased in GHSROS-overexpressing LNCaP cells treated with the cytotoxic drug docetaxel (P ≤ 0.05, Student's t-test). Docetaxel treatment also increased GHSROS expression in native LNCaP and PC3 cells in a dose-dependent manner (P ≤ 0.05, Student's t-test). These data suggest that GHSROS mediates tumor survival and resistance to docetaxel. To identify fundamental drivers of the observed tumorigenic phenotype of GHSROS-overexpressing cell lines, high-throughput RNA-seq data from in vitro cultured PC3 cells and LNCaP xenografts were examined. A quarter of the genes differentially expressed by GHSROS-overexpressing PC3 cells were also differentially expressed by GHSROS-overexpressing LNCaP xenografts. These 101 genes include several transcription factors with established roles in prostate cancer (including the androgen receptor) and genes associated with metastasis and poor prognosis. Finally, we developed two distinct antisense oligonucleotides (ASOs) targeting GHSROS, achieving >60% knockdown, and their function was assessed in vitro. ASO inhibition of GHSROS expression reciprocally regulated cell growth and migration and the expression of a range of genes. These ASOs are currently being assessed in preclinical animal models. Our findings suggest that the long noncoding RNA GHSROS reprograms prostate cancer cells toward a more aggressive phenotype and that the lncRNA represents a promising therapeutic target.