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The inhibitor of DNA binding protein 4 (ID4) is a dominant negative regulator of basic helix loop helix (bHLH) family of transcription factors.1 Recently, Patel et al., demonstrated that inhibitor of differentiation 4 (ID4) acts as a tumor suppressor and its loss, frequently observed in prostate cancer, promotes castration-resistant prostate cancer (CRPC) through constitutive androgen receptor (AR) activation.2 However, the mechanism by which loss of ID4 promotes constitutively active AR signaling in the CRPC conditions is unknown. The rationale of the present study was to unravel the underlying molecular mechanisms through which loss of ID4 potentiates AR signaling in this setting. Initially, chromatin immunoprecipitation (ChIP) assay results demonstrated a significant increase in binding of AR to its respective response elements on PSA, FKBP51, TMPRSS2, and ETV1 promoters in L(-)ID4 cells, further implicating constitutive AR activity. Among the notable findings, proteomic profiling between prostate cancer cell line LNCaP (L+ns) and LNCaP lacking ID4 (L(-)ID4) revealed elevated protein levels of Heat shock protein 27 (Hsp27) and the 52-kDa FK506-binding protein (FKBP52), suggesting a role for these AR-associated co-chaperones in promoting constitutively active AR signaling in L(-)ID4 cells. Interestingly, protein interaction studies further confirmed a direct interaction between ID4 and FKBP52 in vitro but not with AR. Recent evidences suggest that FKBP52 is a positive regulator of AR signaling in cellular and whole animal models.3-6 Thus, we hypothesized that ID4 acts as a tumor suppressor by selectively regulating AR activity through interaction with FKBP52. To address the underlying mechanism, we blocked the FKBP52-AR signaling using a specific inhibitory compound known as MJC13.4, 6-7 The results demonstrated that MJC13 effectively inhibited AR-dependent expression and activity in a dose-dependent manner. In addition, xenograft studies further confirmed that inhibiting FKBP52-regulated AR activity via MJC13 significantly attenuated the growth of subcutaneous L(-)ID4 xenografts in vivo. Collectively, our results suggested that ID4 selectively regulates AR activity through direct interaction with FKBP52 in vitro, and, its loss promotes CRPC through FKBP52-mediated AR signaling. Increased AR signaling along with a subsequent decrease in ID4 expression levels in prostate cancer strongly supports this model.

Prostate cancer (PCa) is the most common cancer in American men. Although initial androgen deprivation therapy (ADT) confers a five year survival rate of 99%, the relapse of metastatic and drug resistant PCa (CRPC- Castration-Resistant PCa) continues to account for most deaths. How certain PCa cells develop into CRPC is the key question in the field. In addressing it, attention has focused on epigenetic factors that contribute to CRPC development. Herein we investigated the role and regulation of histone demethylase PHF8 during PCa neuroendocrine differentiation (NED) and progression into CRPC. We utilized bioinformatic analyses and biochemical approaches in PCa/CRPC cell line and mouse models to unravel the following results: First, we discovered that PHF8 post-transcriptionally clusters with cell cycle genes during NED and into CRPC via an AR/MYC/miR-22 regulatory axis. We showed that this axis is dysregulated in CRPC cells to allow enhanced cell proliferation and resistance to the clinical AR antagonist drug Xtandi® (enzalutamide). Second, we revealed that PHF8 is necessary for hypoxia induced NED by demethylating repressive H3K9me2 and H3K27me2, above maintaining active H3K4me3 on select NED genes. Importantly, we unveiled that PHF8 sustains HIF1α expression in CRPC cells via a regulatory role associated with full length AR. Third, we recapitulated the role of PHF8 in vivo by excising its floxed allele in the prostate of TRAMP mice -Transgenic Adenocarcinoma of the Mouse Prostate. We observed that KO of Phf8 lowered tumor burden in part by sustaining Ezh2 expression during NED transition into CRPC. In conclusion, our data implicates PHF8 in multiple oncogenic roles and regulations during PCa NED into CRPC. Our results lay a foundation for understanding the dynamics of histone modifying enzymes during PCa progression and hint at designing small molecule inhibitors against PHF8 as a novel CRPC therapeutic target.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23081号 / 医博第4708号 / 新制||医||1049(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 中本 裕士, 教授 小川 誠司, 教授 武田 俊一 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

1 ABSTRACT Introduction and aim of the study Circulating tumor cells (CTCs) are a promising tool of identifying patients with castration- resistant prostate cancer (CRPC) who will benefit from often demanding cytotoxic therapy. The aim of this work was to evaluate the prognostic significance of CTC in docetaxel-treated CRPC patients. During the project, we also tested the various methods of CTC cultivation and studied their genetic profile as well as the genetic profile of histological specimen at the time of diagnosis. Patients and methods A total of 39 patients who met the CRPC criteria and were indicated for docetaxel chemotherapy were included in the prospective study. Blood collection for CTC analysis was done in all patients before chemotherapy and on the first day of the fourth or fifth cycle of docetaxel. In parallel, CTCs were cultivated. Isolation and detection of CTC was done using the AdnaTest system, which consists of immunomagnetic separation and subsequent detection of mRNA from the CTC lysate. The primary objective of the study was to evaluate the overall survival (OS) of patients. Survival analysis was performed using the Kaplan-Meier method of estimating the survival distribution function. The impact of individual factors was tested using the Log-rank test, the Wilcoxon test and the Cox...

This study focused on the role of RANKL in prostate cancer EMT progression and metastasis. Activation of RANK, a receptor activator of NF-kB, by its ligand RANKL, in a paracrine manner is responsible for osteoclast differentiation and bone remodeling. RANK activation in cancer cells, however, is thought to be promoted by both autocrine and paracrine mechanisms because RANKL has been shown to be derived from either tumor or its microenvironment, such as osteoblasts, infiltrating inflammatory cells and stromal fibroblasts. In the present study, we demonstrated that autocrine and paracrine RANKL-RANK signaling could be responsible for driving prostate cancer bone metastasis by promoting epithelial to mesenchymal transition (EMT). We further characterized a novel converging RANKL-c-Met signaling network in which the activation of RANKL was found to promote the expression of both RANKL and c-Met in an autocrine manner in prostate cancer cells. The induced RANKL and c-Met in prostate cancer cells is biologically functional and contributes to increased osteoclastogenesis, epithelial to mesenchymal transition (EMT), cell motility, migration and invasion and conferred bone and soft tissue metastases. Remarkably, RANKL expression by 1,000 prostate cancer cells can provoke bone and soft tissue metastases of a “dormant” population of prostate cancer cells which by themselves failed to form tumors and colonize mouse skeleton, suggesting RANKL can serve as a factor in “reawakening” cancer dormancy to initiate the re-growth and metastasis of cancer cells. We also showed that RANKL-induced RANKL feed-forward autocrine regulation is mediated through cMyc transactivation, allowing the establishment of a “vicious cycle” further promoting prostate cancer growth and metastasis. The converging RANKL-c-Met signaling network is therefore a novel target that could be further manipulated for delaying the lethal progression of castration-resistant human prostate cancer bone metastasis.

Introduction: Together with the introduction of new therapeutic options in castration- resistant prostate cancer (CRPC), an advance in individual disease characterization is required. Since common biopsy methods are not suitable for the majority of CRPC patients, one possible solution is the liquid biopsy that is, the analysis of circulating tumor cells (CTCs) isolated from the cancer patients' blood. Methods: A method based on the immunomagnetic enrichment of CTCs and subsequent PCR detection of tumor-associated genes (AdnaTest, Qiagen) was characterized and used for the detection of CTCs in 41 CRPC patients. Each patient was screened at the time of CRPC diagnosis and after the 3rd cycle of docetaxel therapy. A panel of genes associated with therapeutic decision-making was established and validated. Quantitative PCR (qPCR) method on a BioMark platform (Fluidigm, USA) was used to determine the expression of the gene panel in the CTC-enriched and primary tumor samples and the results were analyzed. Results: CTCs were found in 85% and 45% of CRPC patients before and during the therapy, respectively. The presence of CTCs, as well as EGFR and AR PCR fragments, was associated with a decreased sPSA response and lower survival. The gene expression of the CTC- enriched and primary tumor samples differed...

Le cancer de la prostate représente actuellement un problème majeur de santé publique. L’hormonothérapie, par privation de l’axe androgénique, constitue aujourd’hui la seule arme thérapeutique efficace pour les formes avancées. Malgré un taux important de réponse initiale, une forme de résistance survient inéluctablement, conduisant pour la plupart au décès du patient. La progression tumorale vers la résistance à la castration est un processus multifactoriel. Elle peut être associée à une dérégulation de l’axe du récepteur des androgènes, l’activation de voies de survie cellulaire, et favoriser une différenciation cellulaire vers l’acquisition d’un phénotype neuroendocrine androgéno-indépendant. L’objectif de la recherche actuelle repose donc sur l’identification de nouveaux biomarqueurs de résistance thérapeutique afin de proposer de nouvelles cibles permettant de contrecarrer la résistance à la castration. La caractérisation d’une signature moléculaire associée à l’émergence d’une différenciation neuroendocrine du cancer de la prostate résistant à la castration a permis d’identifier la Neuropiline-1, une glycoprotéine transmembranaire impliquée dans le développement neuronal et vasculaire. La répression de la voie du récepteur des androgènes au cours de l’hormonothérapie régule dynamiquement l’expression de la Neuropiline-1 et favorise la résistance à la castration associée à une différenciation neuroendocrine. La Neuropiline-1 joue donc un rôle important dans la résistance thérapeutique puisqu’elle favorise la neuro-transdifférenciation, l’activation de voie de survie cellulaire et altère la sensibilité des cellules cancéreuses à la chimiothérapie. L’étude des voies de signalisation associées à la Neuropiline-1 a permis d’identifier la voie des PKCs, impliquée dans la régulation de la différenciation neuroendocrine du cancer de la prostate. Par conséquent, nous montrons pour la première fois que le ciblage de cette voie activée par la Neuropiline-1 bloque l’évolution tumorale vers la résistance à la castration et augmente l’efficacité d’une chimiothérapie à base de docétaxel sur des modèles précliniques in vivo. Parallèlement, la caractérisation des ligands de la Neuropiline a permis d’identifier de nouveaux partenaires dont la Pléiotrophine, comme nouveau ligand associé aux activités biologiques de la Neuropiline-1 dans la carcinogenèse prostatique. L’ensemble de ces travaux apporte de nouvelles connaissances sur la caractérisation de la résistance thérapeutique du cancer de la prostate, et fournit un réel intérêt clinique porteur d’espoir dans la prise en charge de la maladie neuroendocrine résistante à la castration. / Prostate cancer currently represents a major public health problem. Hormone therapy, by deprivation of androgen signaling axis represents the only efficient treatment for advanced forms. Despite effective initial response, a form of resistance inevitably occurs, leading mostly to patient's death. Tumor progression to castration resistance is a multifactorial process. It can be associated to dysregulation of the androgen receptor axis and activation of cell survival pathways, and thus promotes cell differentiation towards the acquisition of an androgen-independent neuroendocrine phenotype. Therefore, the goal of current research is based on the identification of new biomarkers of therapeutic resistance to propose new targets to counteract the castration resistance. The characterization of a molecular signature associated with the emergence of a neuroendocrine castration-resistant prostate cancer identified Neuropilin-1, a transmembrane glycoprotein involved in vascular and neuronal development. Down-regulation of androgen receptor axis during hormone therapy dynamically regulates the expression of Neuropilin-1 and promotes resistance to castration associated with neuroendocrine differentiation. Thus, Neuropilin-1 plays an important role in the therapeutic resistance since it favors the neuro-transdifferentiation, activation of cell survival pathway and alters the sensitivity of cancer cells to chemotherapy. Moreover, the study of signaling pathways associated with Neuropilin-1 and involved in the regulation of the neuroendocrine differentiation of prostate cancer has identified the PKCs pathway. We show for the first time that targeting this pathway activated by Neuropilin-1 blocks tumor evolution towards resistance to castration and increases the efficacy of docetaxel-based chemotherapy in preclinical models in vivo. In parallel, the characterization of Neuropilin’s ligands identified new partners, including Pleiotrophin, as a new ligand associated with Neuropilin-1 biological activities in prostate carcinogenesis. All this work provides new knowledge in the characterization of therapeutic resistance in prostate cancer, and supports a real promising clinical value in the treatment of neuroendocrine castration-resistant form of the disease.

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Zur Therapie des metastasierten hormonsensitiven oder kastrationsresistenten Prostatakarzinoms (mHSPC, mCRPC) gab es in den letzten Jahren zahlreiche neue Erkenntnisse aus klinischen Studien. Die neu zugelassenen Behandlungsoptionen machen die Therapieplanung und Therapiesequenz anspruchsvoller. Hinzu kommt, dass die Lokaltherapie des metastasierten Prostatakarzinoms zunehmend an Bedeutung gewinnt. Im neuen Update 6.2 der S3-Leitlinie zum Prostatakarzinom vom Oktober 2021 wurden die neuen Entwicklungen bei den Empfehlungen zur Behandlung des mHSPC und mCRPC umgesetzt, deren wichtigsten Neuerungen und die daraus resultierenden Empfehlungen für die Praxis dargestellt werden. / There have been numerous new findings from clinical trials in recent years regarding the treatment of metastatic hormone-sensitive or castration-resistant prostate cancer. The newly approved treatment options make therapy planning and therapy sequencing more challenging. In addition, local therapy of metastatic prostate cancer is becoming increasingly important. In the new German guidelines on prostate cancer (version 6.2, October 2021), new developments in the recommendations for the treatment of mHSPC and mCRPC were implemented, and their most important resulting recommendations for the clinical practice are presented in this review.