Epitranscriptomic mechanisms in prostate and breast cancer

Woodcock, Corinne

Epitranscriptomic mechanisms in prostate and breast cancer

Publication Date

July 29, 2022

Creator

Woodcock, Corinne

Abstract

Prostate (PCa) and breast cancer (BC) are two of the most commonly diagnosed cancers and leading causes of cancer related deaths. The androgen (AR) and estrogen (ER) receptors are members of the steroid receptor family of ligand dependent transcription factors which play essential physiological roles in gene expression and splicing but are also implicated in PCa and BC. Cancer therapies that target AR and ER function, including androgen deprivation therapy (ADT), AR signalling inhibitors (ARSI), and selective estrogen receptor modulators (SERMs) are critical for improved patient outcomes. However, the emergence of treatment resistance is common. For example, treatment-emergent castrate resistant PCa (CRPC) is attributable to a number of mechanisms including aberrant expression and splicing of the AR. N6-methyladenosine (m6A) is the most abundant post-transcriptional modification in mRNA and is regulated through the METTL3 methyltransferase complex and ALKBH5 and FTO demethylases. The dynamic regulation of m6A alters mRNA function, including gene expression, alternative splicing, and translation. m6A and its regulatory proteins have also recently been implicated in disease, notably in cancers. However, there is little known about the role of m6A demethylases in nuclear receptor signalling in PCa and BC. The convergence of nuclear receptor and m6A-related epitranscriptomic mechanisms on the regulation of gene expression and splicing supports the hypothesis that m6A regulates endocrine signalling in PCa and BC. To test this hypothesis, the expression of the ALKBH5 and FTO m6A demethylases was examined in large PCa and invasive BC cohorts and functional studies completed. In BC patient specimens, high ALKBH5 expression was found to be associated with clinical factors pertinent to better prognosis, whereas high FTO expression was correlated with factors associated with poor prognosis. ALKBH5 and FTO were expressed in PCa patient specimens, including in advanced tumour types. Functional studies of ALKBH5 and FTO in PCa cell lines identified a role for m6A in basal and androgen regulated gene expression and alternative splicing. Additionally, CRISPR-Cas9 knockout of FTO was shown to regulate AR expression and sensitise CRPC cell line 22Rv1 to enzalutamide, thereby implicating m6A in ADT resistance. Collectively, these data indicate a role for ALKBH5 and FTO, and by inference m6A, in PCa and BC. Furthermore, this study provides evidence of a role for m6A in treatment resistance in PCa, highlighting it as a potential novel therapeutic target to prevent or treat CRPC.

Item Type

ethesis

Thesis Type

PhD

Supervisors