The role and mechanism of RNA m6A modification in the pathogenesis and drug-resistance of prostate cancer

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PROJECT TITLE: The role and mechanism of RNA m6A modification in the pathogenesis and drug-resistance of prostate cancer PROJECT SUMMARY (ABSTRACT): Background: N6-methyladenosine (m6A) modification is the most prevalent and abundant internal modification in eukaryotic messenger RNAs (mRNAs) and plays diverse and important roles in normal biological processes. Emerging evidence suggest that m6A and m6A-assicated proteins also play critical roles in human diseases including cancers. Prostate cancer (PCa) is the most commonly diagnosed cancer with the second leading estimated deaths at the United States for more than a decade. Androgens and androgen receptor (AR) regulate normal growth and function of the prostate gland. However, aberrant regulation of androgens and AR signaling pathway are closely associated with PCa pathogenesis and progression. Thus, androgen deprivation therapies (ADT) or targeting AR function have always been the mainstay of therapeutic strategy against advanced prostate cancers. However, the current therapeutic strategies cannot cure most PCa patients due to drug resistance and relapse, and eventually develop metastatic, castration-resistant prostate cancer (mCRPC), a lethal stage of the disease. The acquired resistance to abiraterone and enzalutamide is considered as the main problem for the treatment failure and relapse of PCa. Therefore, it is crucial to elucidate the molecular mechanisms underlying PCa pathogenesis and drug resistance, which may contribute to the development of effective new therapeutic approaches to overcome the limitations of current treatment for PCa. RNA m6A modification is deposited by m6A methyltransferase complex composed of three core subunits METTL3, METTL14 and WTAP and may have functions as an important regulator of gene expression that can affect mRNA transcription, splicing, export, stability, and translation. Previously, we have reported that METTL3-catalyzed m6A modification of target mRNA plays critical oncogenic roles in human cancers including PCa, but its definitive roles in AR signaling activation and especially in drug-resistant AR signaling remain elusive. Our preliminary data imply that m6A modification on enhancer RNAs (eRNAs), which are regulatory RNAs transcribed from non-coding enhancer elements, may also have roles in drug resistance in PCa, which requires further systematic studies. The goal of this proposal is to prove the central hypothesis that METTL3-mediated RNA m6A modification plays essential roles in AR signaling, PCa pathogenesis and drug resistance. The m6A methylome of chromatin-associated regulator RNAs (carRNAs) and nascent RNAs will be mapped, analyzed and correlated with the genome-wide binding of AR and transcriptional machineries. Also, the role of YTHDC1, a nuclear m6A reader protein, will be systemically examined to investigate its relationship with the transactivation of AR and genome-wide distribution, as it has been known to regulate transcriptional activation or repression via binding to m6A-modified RNAs. Loss- and gain-of-function experiments will address the widespread impact of RNA m6A modification in controlling the activation of AR signaling and downstream gene expression, and thus will help uncover the molecular mechanism underlying the role of m6A modification in PCa pathogenesis. Finally, the effects of m6A modification manipulation in the AR signaling regulation with drug-resistant AR mutations will be explored using a xenograft PCa mouse model, as well as a patient-derived xenograft (PDX) models and a panel of assays will be placed to examine the underlying molecular mechanism. Our proposed study will successfully reveal the role of RNA m6A modification in AR signaling and PCa pathogenesis, and help evaluate the clinical potential pharmacological inhibition of m6A modification in PCa, especially metastatic and drug resistant PCa.