Dissertations, Theses, and Capstone Projects

Date of Degree

2-2022

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Olorunseun Ogunwobi

Committee Members

Frida Kleiman

Diana Bratu

Yu Chen

Brian Robinson

Xavier Graña-Amat

Subject Categories

Biology

Keywords

prostate cancer, FRYL, microRNA-1205, neuroendocrine prostate cancer, neuroendocrine differentiation

Abstract

Prostate cancer (PCa) is one of the most commonly diagnosed cancers among men in the United States. High mortality rates of PCa are associated with metastatic castration-resistant prostate cancer (mCRPC) due to the maintenance of androgen receptor (AR) signaling despite androgen deprivation therapies (ADTs). Resistance to second generation ADTs leads to the progression of AR-independent treatment related-neuroendocrine PCa (t-NEPC), which is observed in nearly 1 in 5 men with mCRPC and is associated with very poor outcomes. The 8q24 chromosomal locus is a region of very high PCa susceptibility that carries genetic variants associated with PCa aggressiveness. Located at this region is the PVT1 non-protein coding gene, implicated in PCa, and that encodes microRNA-1205 (miR-1205). As PVT1-encoded miRNAs are largely understudied, we sought to understand the role of miR-1205 to further implicate the importance of the 8q24 chromosomal locus in PCa. We observed that miR-1205 is underexpressed in a cohort of histologically confirmed PCa tissues, when compared to normal tissues and is also underexpressed in CRPC cells, when compared to non-CRPC cells. Our preliminary data suggest that a synthetic analog of miR-1205 inhibited tumor volume in a xenograft mouse model of CRPC, suggesting that miR-1205 may be a tumor suppressor in PCa. To understand the molecular mechanisms of miR-1205, we identified and validated FRYL as a molecular target of miR-1205 and demonstrated that miR-1205 can regulate FRYL mRNA stability. To identify additional molecular targets of miR-1205, a RNA pulldown assay was performed and sequencing of miR-1205 enriched targets (Arraystar INC) were identified (in collaboration with Dr. Konstantinos Krampis) in various PCa models. We discovered that miR-1205’s molecular signature may be involved in neural-associated pathways, including dendrite regulation and cell differentiation. Interestingly, FRYL is also predicted to regulate dendritic branching and is significantly overexpressed in NEPC tissue when compared to benign prostate tissues. Therefore, we hypothesized that miR-1205 and FRYL could be involved in PCa neuroendocrine differentiation (NED), a phenomenon that is observed in t-NEPC. Differentiation of PCa luminal cells into AR-negative neuroendocrine cells occurs as a mechanism of defense towards ADT’s. We examined miR-1205 regulation of FRYL in NED in vitro by culturing LNCaP androgen sensitive PCa cells under androgen deprivation conditions. We observed FRYL mRNA overexpresssion and significant underexpression of miR-1205 in LNCaP-NED cells when compared to undifferentiated LNCaP cells. To further characterize this mechanism, a miR-1205 mimic was used to overexpress miR-1205 in LNCaP cells. While FRYL and NEPC markers (AurA and Neuron specific enolase 2) expression decreased when miR-1205 was overexpressed, FRYL knockdown did not decrease NED markers, suggesting that miR-1205 regulates NED-specific targets in a FRYL-independent manner. In conclusion, this project provides novel insights into the role of miR-1205 in biological mechanisms that could have clinical relevance in PCa.

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