Prostate cancer is one of the most frequently diagnosed cancers and the second leading cause of cancer-related deaths in male population. While localized prostate cancer can be successfully treated with surgery or radiation therapy, the metastatic disease has no curable options. Metastasis can be developed as a result of failed therapy of localized cancer or present at initial diagnosis. As metastasis is the most common cause of prostate cancer-related death, developing novel approaches and improving the efficiency of existing therapies for the metastatic prostate cancer treatment will significantly improve patients’ survival. <div><br><div>The first-line treatment option for metastatic prostate cancer and localized prostate cancer with high risk of recurrence is androgen deprivation therapy (ADT) that decreases androgen receptor (AR) signaling. However, targeting AR signaling inevitably leads to AR reactivation and cancer progression to the castration-resistant prostate cancer (CRPC) that has no curable treatment options. Moreover, about 30% of CRPC cases progress to neuroendocrine prostate cancer (NEPC), highly aggressive and lethal type of prostate cancer. </div><div><br></div><div>Recently my group has shown that protein arginine methyltransferase 5 (PRMT5) functions as an activator of AR expression in hormone-naïve prostate cancer (HNPC). In this dissertation, I demonstrate that PRMT5 also functions as an epigenetic activator of AR transcription in CRPC via symmetric dimethylation of H4R3 at the AR promoter. This epigenetic activation is dependent on pICln, a PRMT5 interaction partner involved in spliceosome assembly, and independent of MEP50, the canonical cofactor of PRMT5. PRMT5 and pICln, but not MEP50, were required for the expression of AR signaling pathway genes. In clinical samples of both HNPC and CRPC, nuclear PRMT5 and pICln protein expressions were highly positively correlated with nuclear AR protein expression. In xenograft tumors, targeting PRMT5 or pICln significantly decreased tumor growth and AR expression. </div><div><br></div><div>Overall, this work identifies PRMT5/pICln as a therapeutic target for HNPC and CRPC treatment that needs to be further evaluated in clinical setting. </div></div>

Sex differences exist in the functioning of the two brain corticosteroid receptor systems. Ovarian steroid replacement alters receptor mRNA expression, receptor binding capacities, and receptor affinity. The abundance of both mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) message can be reduced by estrogen. Progesterone is able to partially antagonize the action of estrogen and to induce MR transcription. The effect of estrogen on receptor binding capacity is more modest than its transcriptional actions. Estrogen decreases MR binding more reliably than it does GR. Progesterone has high affinity for the MR and can substantially reduce MR affinity for corticoids. Androgen apparently regulates corticoid receptor transcription but may not affect binding capacity. Estrogen and androgen are both more potent in regulating pituitary-adrenal function than would be suggested by their actions on receptor binding parameters.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20970号 / 医博第4316号 / 新制||医||1026(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 小川 修, 教授 戸井 雅和, 教授 万代 昌紀 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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The current standard treatment of prostate cancer by androgen deprivation therapy involves using drugs such as bicalutamide (Casodex) to antagonistically block androgen receptors that are normally present within prostate cells. Usually, the therapy is successful in the short run at limiting the growth of prostate cancer. However, in virtually all cases tumors begin to grow aggressively again after several months of treatment and new therapies must be started. The mechanism by which these prostate cells transform from androgen sensitive to androgen independent and anti-androgen resistant is unclear. In this study, we investigated the role of microRNAs, small 15 to 18 nucleotide regulatory RNAs, in regulating the desensitization of prostate cancer cells to the androgen receptor antagonist drug bicalutamide. In order to identify significant microRNAs, quantitative PCR was used to obtain genome-wide microRNA expression levels of 885 human microRNAs at different timepoints for androgen sensitive LNCaP cancer cells treated with bicalutamide and for untreated control cells in tissue culture. Analysis of microRNA expression by clustering analysis and by statistical comparisons of treatment groups resulted in identification of 28 microRNAs that have altered expression in the progression process. In silico target prediction analysis was performed with the microRNAs shown to have altered expression, and a group of genes predicted to be under microRNA regulatory control during cancer progression to resistance was identified. A microRNA expression profile can be useful in developing more effective prognostic and therapeutic tools for prostate cancer.

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