Abstract B14: PVT1-derived non-coding RNAs in prostate cancer in men of African ancestry

Prostate cancer (PCa) is the most common non-skin cancer and the second leading cause of cancer-related death for men in the U.S. Males of African Ancestry (MoAA) have a higher incidence of PCa, compared to Caucasian males (CM). In fact, African ancestry is a confirmed, non-modifiable risk factor for PCa with a 2.5 fold greater risk of lethal PCa in MoAA compared to CM. Discovery of biomarkers with diagnostic, prognostic, and therapeutic applications are necessary to address this profound health disparity. The chromosomal region 8q24 is associated with aggressive PCa in MoAA and variants of this region have been identified to interact with the PVT1 non-coding gene in PCa. PVT1 is located at 8q24 and is transcribed into a long non-coding RNA that has been implicated in PCa. In previous work where we identified at least 12 exons of PVT1, we observed that exon 9 of PVT1 is significantly upregulated in aggressive PCa cell lines derived from MoAA and that silencing expression of PVT1 exon 9 induces apoptosis and cell cycle arrest in aggressive PCa cells derived from MoAA. PVT1 also encodes six annotated microRNAs and we have reported that one of them, miR-1207-3p, has prognostic value in PCa, is differentially expressed in the prostate tumor tissues of MoAA versus CM, and directly binds to the 39 UTR of Fibronectin type III domain containing 1 (FNDC1) to regulate a novel FNDC1/fibronectin (FN1)/androgen receptor (AR) pathway upregulated in metastatic PCa. To further identify racially differentiated cancer-risk factors in the PVT1 locus, we scanned for signatures of population differentiation and positive natural selection using the latest (Release GRCh38) full-genome variability panel from the 1000 Genomes Project. A string of 75 single-nucleotide polymorphisms (SNPs) in a 26-kb region spanning PVT1 exons 4A and 4B consistently show the highest level of genetic differentiation (Fst ~ 0.25) between the African and non-African populations. Nucleotide sequences in the 26-kb region fall into two major phylogenetic clades, including a clade present in all human populations (“Cosmopolitan Clade”), and another clade present nearly exclusively in non-African populations. To investigate the biological functions of the 26-kb element and its potential role in cancer, we examined the expression of PVT1 exons 4A and 4B in a panel of eight PCa cell lines modeling various clinical characteristics, and found that PVT1 exons 4A and 4B are overexpressed in PCa cell lines derived from aggressive PCa in MoAA. Functional studies upon silencing of PVT1 exons 4A and 4B showed an inhibition of cell proliferation when PVT1 exon 4B was silenced in aggressive PCa cells derived from MoAA. To discover all the molecular targets of miR-1207-3p, we designed and synthesized a novel synthetic biotinylated miR-1207-3p duplex and a novel synthetic biotinylated scramble duplex as control, and then we proceeded to validate these novel tools. Our data show that the novel synthetic biotinylated miR-1207-3p duplex directly binds to the 39 UTR of FNDC1 and inhibits the FNDC1/FN1/AR pathway. Wound healing assays revealed that our synthetic biotinylated miR-1207-3p duplex significantly inhibits cellular migration in PCa cells derived from MoAA by up to 40% when compared with the scramble duplex. Furthermore, Annexin V staining analysis demonstrated that our synthetic biotinylated miR-1207-3p duplex increased apoptosis by nearly 2-fold in PCa cells derived from MoAA compared to scramble duplex. These results show that our synthetic biotinylated miR-1207-3p duplex significantly inhibits migration and induces apoptosis. These data demonstrate the importance of PVT1-derived non-coding RNAs in PCa in MoAA, and provide the basis for larger studies to evaluate prognostic, diagnostic, and therapeutic applications of miR-1207-3p, PVT1 exon 9, PVT1 exon 4A and PVT1 exon 4B in PCa. Note: This abstract was not presented at the conference. Citation Format: Adeodat Ilboudo, Dibash Das, Michelle Naidoo, Lia Di, Weigang Qiu, Olorunseun Ogunwobi. PVT1-derived non-coding RNAs in prostate cancer in men of African ancestry. [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr B14.