Immunosuppressive role of BDNF in therapy-induced neuroendocrine prostate cancer.

Prostate stromal cells play a crucial role in the promotion of tumor growth and immune evasion in the tumor microenvironment (TME) through intricate molecular alterations in their interaction with prostate cancer (PCa) cells. While the impact of these cells on establishing an immunosuppressive response and influencing PCa aggressiveness remains incompletely understood. Our study shows that the activation of the leukemia inhibitory factor (LIF)/LIF receptor (LIFR) pathway in both prostate tumor and stromal cells, following androgen deprivation therapy (ADT), leads to the development of an immunosuppressive TME. Activation of LIF/LIFR signaling in PCa cells induces neuroendocrine differentiation (NED) and upregulates immune checkpoint expression. Inhibition of LIF/LIFR attenuates these effects, underscoring the crucial role of LIF/LIFR in linking NED to immunosuppression. Prostate stromal cells expressing LIFR contribute to NED and immunosuppressive marker abundance in PCa cells, while LIFR knockdown in prostate stromal cells reverses these effects. ADT-driven LIF/LIFR signaling induces brain-derived neurotrophic factor (BDNF) expression, which, in turn, promotes NED, aggressiveness, and immune evasion in PCa cells. Clinical analyses demonstrate elevated BDNF levels in metastatic castration-resistant PCa (CRPC) and a positive correlation with programmed death-ligand 1 (PDL1) and immunosuppressive signatures. This study shows that the crosstalk between PCa cells and prostate stromal cells enhances LIF/LIFR signaling, contributing to an immunosuppressive TME and NED in PCa cells through the upregulation of BDNF.

Dysbindin Domain-Containing 1 in Prostate Cancer: New Insights into Bioinformatic Validation of Molecular and Immunological Features.

Prostate cancer (PCa) is one of the most prevalent cancers in men, yet its pathogenic pathways remain poorly understood. Transcriptomics and high-throughput sequencing can help uncover cancer diagnostic targets and understand biological circuits. Using prostate adenocarcinoma (PRAD) datasets of various web-based applications (GEPIA, UALCAN, cBioPortal, SR Plot, hTFtarget, Genome Browser, and MetaCore), we found that upregulated dysbindin domain-containing 1 (DBNDD1) expression in primary prostate tumors was strongly correlated with pathways involving the cell cycle, mitotic in KEGG, WIKI, and REACTOME database, and transcription factor-binding sites with the DBNDD1 gene in prostate samples. DBNDD1 gene expression was influenced by sample type, cancer stage, and promoter methylation levels of different cancers, such as PRAD, liver hepatocellular carcinoma (LIHC), and lung adenocarcinoma (LUAD). Regulation of glycogen synthase kinase (GSK)-3ß in bipolar disorder and ATP/ITP/GTP/XTP/TTP/CTP/UTP metabolic pathways was closely correlated with the DBNDD1 gene and its co-expressed genes in PCa. DBNDD1 gene expression was positively associated with immune infiltration of B cells, Myeloid-derived suppressor cell (MDSC), M2 macrophages, andneutrophil, whereas negatively correlated with CD8+ T cells, T follicular helper cells, M1 macrophages, and NK cells in PCa. These findings suggest that DBNDD1 may serve as a viable prognostic marker not only for early-stage PCa but also for immunotherapies.

CHRM4/AKT/MYCN upregulates interferon alpha-17 in the tumor microenvironment to promote neuroendocrine differentiation of prostate cancer.

Current treatment options for prostate cancer focus on targeting androgen receptor (AR) signaling. Inhibiting effects of AR may activate neuroendocrine differentiation and lineage plasticity pathways, thereby promoting the development of neuroendocrine prostate cancer (NEPC). Understanding the regulatory mechanisms of AR has important clinical implications for this most aggressive type of prostate cancer. Here, we demonstrated the tumor-suppressive role of the AR and found that activated AR could directly bind to the regulatory sequence of muscarinic acetylcholine receptor 4 (CHRM4) and downregulate its expression. CHRM4 was highly expressed in prostate cancer cells after androgen-deprivation therapy (ADT). CHRM4 overexpression may drive neuroendocrine differentiation of prostate cancer cells and is associated with immunosuppressive cytokine responses in the tumor microenvironment (TME) of prostate cancer. Mechanistically, CHRM4-driven AKT/MYCN signaling upregulated the interferon alpha 17 (IFNA17) cytokine in the prostate cancer TME after ADT. IFNA17 mediates a feedback mechanism in the TME by activating the CHRM4/AKT/MYCN signaling-driven immune checkpoint pathway and neuroendocrine differentiation of prostate cancer cells. We explored the therapeutic efficacy of targeting CHRM4 as a potential treatment for NEPC and evaluated IFNA17 secretion in the TME as a possible predictive prognostic biomarker for NEPC.

Targeting PKLR/MYCN/ROMO1 signaling suppresses neuroendocrine differentiation of castration-resistant prostate cancer.

Conventional treatment of prostate cancer (PCa) uses androgen-deprivation therapy (ADT) to inhibit androgen receptor (AR) signaling-driven tumor progression. ADT-induced PCa recurrence may progress to an AR-negative phenotype with neuroendocrine (NE) histologic features, which are associated with metabolic disturbances and poor prognoses. However, the metabolic pathways that regulate NE differentiation (NED) in PCa remain unclear. Herein, we show a regulatory mechanism in NED-associated metabolism dysfunction induced by ADT, whereby overexpression of pyruvate kinase L/R (PKLR) mediates oxidative stress through upregulation of reactive oxygen species modulator 1 (ROMO1), thereby promoting NED and aggressiveness. ADT mediates the nuclear translocation of PKLR, which binds to the MYCN/MAX complex to upregulate ROMO1 and NE-related genes, leading to altered mitochondrial function and NED of PCa. Targeting nuclear PKLR/MYCN using bromodomain and extra-terminal motif (BET) inhibitors has the potential to reduce PKLR/MYCN-driven NED. Abundant ROMO1 in serum samples may provide prognostic information in patients with ADT. Our results suggest that ADT resistance leads to upregulation of PKLR/MYCN/ROMO1 signaling, which may drive metabolic reprogramming and NED in PCa. We further show that increased abundance of serum ROMO1 may be associated with the development of NE-like PCa.

MicroRNAs as clinical tools for diagnosis, prognosis, and therapy in prostate cancer.

Prostate cancer (PCa) is one of the most commonly diagnosed cancers among men worldwide. Despite the presence of accumulated clinical strategies for PCa management, limited prognostic/sensitive biomarkers are available to follow up on disease occurrence and progression. MicroRNAs (miRNAs) are small non-coding RNAs that control gene expression through post-transcriptional regulation of their complementary target messenger RNA (mRNA). MiRNAs modulate fundamental biological processes and play crucial roles in the pathology of various diseases, including PCa. Multiple evidence proved an aberrant miRNA expression profile in PCa, which is actively involved in the carcinogenic process. The robust and pleiotropic impact of miRNAs on PCa suggests them as potential candidates to help more understand the molecular landscape of the disease, which is likely to provide tools for early diagnosis and prognosis as well as additional therapeutic strategies to manage prostate tumors. Here, we emphasize the most consistently reported dysregulated miRNAs and highlight the contribution of their altered downstream targets with PCa hallmarks. Also, we report the potential effectiveness of using miRNAs as diagnostic/prognostic biomarkers in PCa and the high-throughput profiling technologies that are being used in their detection. Another key aspect to be discussed in this review is the promising implication of miRNAs molecules as therapeutic tools and targets for fighting PCa.

Pyruvate kinase L/R links metabolism dysfunction to neuroendocrine differentiation of prostate cancer by ZBTB10 deficiency.

Neuroendocrine differentiation (NED) frequently occurs in androgen-deprivation therapy (ADT)-resistant prostate cancer (PCa) and is typically associated with metabolic pathway alterations, acquisition of lineage plasticity, and malignancy. There is no conventional therapeutic approach for PCa patients with NED pathologic features because the molecular targets are unknown. Here, we evaluated the regulatory mechanism of NED-associated metabolic reprogramming induced by ADT. We detected that the loss of the androgen-responsive transcription factor, zinc finger, and BTB domain containing 10 (ZBTB10), can activate pyruvate kinase L/R (PKLR) to enhance a NED response that is associated with glucose uptake by PCa cells. PKLR exhibits a tumor-promoting effect in PCa after ADT, but ZBTB10 can compensate for the glucose metabolism and NED capacity of PKLR through the direct transcriptional downregulation of PKLR. Targeting PKLR by drug repurposing with FDA-approved compounds can reduce the aggressiveness and NED of ADT-resistant PCa. We demonstrated that PKLR acts as a modulator to activate NED in PCa enhancement by loss of ZBTB10, thereby enabling PCa cells to mount a glycolysis response essential for therapeutic resistance. Our findings highlight the broad relation between NED and metabolic dysfunction to provide gene expression-based biomarkers for NEPC treatment.

PCK1 regulates neuroendocrine differentiation in a positive feedback loop of LIF/ZBTB46 signalling in castration-resistant prostate cancer.

BACKGROUND: Castration-resistant prostate cancer (CRPC) patients frequently develop neuroendocrine differentiation, with high mortality and no effective treatment. However, the regulatory mechanism that connects neuroendocrine differentiation and metabolic adaptation in response to therapeutic resistance of prostate cancer remain to be unravelled. METHODS: By unbiased cross-correlation between RNA-sequencing, database signatures, and ChIP analysis, combining in vitro cell lines and in vivo animal models, we identified that PCK1 is a pivotal regulator in therapy-induced neuroendocrine differentiation of prostate cancer through a LIF/ZBTB46-driven glucose metabolism pathway. RESULTS: Upregulation of PCK1 supports cell proliferation and reciprocally increases ZBTB46 levels to promote the expression of neuroendocrine markers that are conducive to the development of neuroendocrine characteristic CRPC. PCK1 and neuroendocrine marker expressions are regulated by the ZBTB46 transcription factor upon activation of LIF signalling. Targeting PCK1 can reduce the neuroendocrine phenotype and decrease the growth of prostate cancer cells in vitro and in vivo. CONCLUSION: Our study uncovers LIF/ZBTB46 signalling activation as a key mechanism for upregulating PCK1-driven glucose metabolism and neuroendocrine differentiation of CRPC, which may yield significant improvements in prostate cancer treatment after ADT using PCK1 inhibitors.

TCF7L1 regulates cytokine response and neuroendocrine differentiation of prostate cancer.

Neuroendocrine differentiation (NED) is associated with WNT signaling activation and can be significantly observed after failure of androgen-deprivation therapy (ADT) for prostatic adenocarcinomas. Cytokine signaling is stimulated in NED prostate cancer; however, how ADT-upregulated WNT signaling promotes activation of cytokine signaling and contributes to NED of prostate cancer is poorly understood. In this study, we identified ADT-mediated upregulation of transcription factor 7 like 1 (TCF7L1), which increases the cytokine response and enhances NED of prostate cancer through interleukin (IL)-8/C-X-C motif chemokine receptor type 2 (CXCR2) signaling activation. ADT induced the secretion of WNT4 which upon engagement of TCF7L1 in prostate cancer cells, enhanced IL-8 and CXCR2 expressions. TCF7L1 directly binds to the regulatory sequence region of IL-8 and CXCR2 through WNT4 activation, thus upregulating IL-8/CXCR2 signaling-driven NED and cell motility. Analysis of prostate tissue samples collected from small-cell neuroendocrine prostate cancer (SCPC) and castration-resistant prostate cancer (CRPC) tumors showed an increased intensity of nuclear TCF7L1 associated with CXCR2. Our results suggest that induction of WNT4/TCF7L1 results in increased NED and malignancy in prostate cancer that is linked to dysregulation of androgen receptor signaling and activation of the IL-8/CXCR2 pathway.

Interplay of Epidermal Growth Factor Receptor and Signal Transducer and Activator of Transcription 3 in Prostate Cancer: Beyond Androgen Receptor Transactivation.

Prostate cancer (PCa) is one of the most common cancers in the world and causes thousands of deaths every year. Conventional therapy for PCa includes surgery and androgen deprivation therapy (ADT). However, about 10-20% of all PCa cases relapse; there is also the further development of castration resistant adenocarcinoma (CRPC-Adeno) or neuroendocrine (NE) PCa (CRPC-NE). Due to their androgen-insensitive properties, both CRPC-Adeno and CRPC-NE have limited therapeutic options. Accordingly, this study reveals the inductive mechanisms of CRPC (for both CRPC-Adeno and CRPC-NE) and fulfils an urgent need for the treatment of PCa patients. Although previous studies have illustrated the emerging roles of epidermal growth factor receptors (EGFR), signal transducer, and activator of transcription 3 (STAT3) signaling in the development of CRPC, the regulatory mechanisms of this interaction between EGFR and STAT3 is still unclear. Our recent studies have shown that crosstalk between EGFR and STAT3 is critical for NE differentiation of PCa. In this review, we have collected recent findings with regard to the involvement of EGFR and STAT3 in malignancy progression and discussed their interactions during the development of therapeutic resistance for PCa.

Nerve growth factor interacts with CHRM4 and promotes neuroendocrine differentiation of prostate cancer and castration resistance.

Nerve growth factor (NGF) contributes to the progression of malignancy. However, the functional role and regulatory mechanisms of NGF in the development of neuroendocrine prostate cancer (NEPC) are unclear. Here, we show that an androgen-deprivation therapy (ADT)-stimulated transcription factor, ZBTB46, upregulated NGF via ZBTB46 mediated-transcriptional activation of NGF. NGF regulates NEPC differentiation by physically interacting with a G-protein-coupled receptor, cholinergic receptor muscarinic 4 (CHRM4), after ADT. Pharmacologic NGF blockade and NGF knockdown markedly inhibited CHRM4-mediated NEPC differentiation and AKT-MYCN signaling activation. CHRM4 stimulation was associated with ADT resistance and was significantly correlated with increased NGF in high-grade and small-cell neuroendocrine prostate cancer (SCNC) patient samples. Our results reveal a role of the NGF in the development of NEPC that is linked to ZBTB46 upregulation and CHRM4 accumulation. Our study provides evidence that the NGF-CHRM4 axis has potential to be considered as a therapeutic target to impair NEPC progression.

EGFR-upregulated LIFR promotes SUCLG2-dependent castration resistance and neuroendocrine differentiation of prostate cancer.

Neuroendocrine (NE) differentiation is a well-recognized phenotypic change of prostate cancer after androgen deprivation therapy (ADT), and it ultimately develops into an aggressive subset of this disease. However, the contribution of signaling pathways that lead to metabolic disorders and NE differentiation of prostate cancer remains unclear. In this study, we identified that ADT induced upregulation of the succinate-CoA ligase GDP-forming beta subunit (SUCLG2), which regulates succinate metabolism and NE differentiation of prostate cancer. We demonstrated a connection that upregulation of epidermal growth factor receptor (EGFR)-leukemia inhibitory factor receptor (LIFR) signaling induced SUCLG2 expression in prostate cancer cells. The LIFR is upregulated by nuclear EGFR, which acts as a transcriptional regulator, directly binds to the LIFR promoter, and drives NE differentiation and glycolysis of prostate cancer. LIFR upregulation is associated with SUCLG2, which increased succinate synthesis and enzymatic activities of mitochondrial nucleoside diphosphate kinase (NDPK) in prostate cancer cells. Knockdown of SUCLG2 suppressed NE differentiation in cultured cells and reduced prostate tumor growth in a xenograft model. Analysis of prostate tissue samples showed increased intensity of nuclear EGFR associated with the LIFR and SUCLG2 in castration-resistant prostate cancer tumors. Our study provides a mechanism whereby ADT upregulates EGFR-LIFR signaling that activates SUCLG2, which subsequently stimulates the metabolic changes associated with NE differentiation and aggressive prostate cancer phenotype.

Correction: Fararjeh, A-F S., et al. ZBTB46, SPDEF, ETV6 Novel Potential Biomarkers and Therapeutic Targets in Castration Resistance Prostate Cancer. Int. J. Mol. Sci. 2019, 20, 2802.

The authors wish to make the following correction to this paper [...].

Ras and Wnt Interaction Contribute in Prostate Cancer Bone Metastasis.

Prostate cancer (PCa) is one of the most prevalent and malignant cancer types in men, which causes more than three-hundred thousand cancer death each year. At late stage of PCa progression, bone marrow is the most often metastatic site that constitutes almost 70% of metastatic cases of the PCa population. However, the characteristic for the osteo-philic property of PCa is still puzzling. Recent studies reported that the Wnt and Ras signaling pathways are pivotal in bone metastasis and that take parts in different cytological changes, but their crosstalk is not well studied. In this review, we focused on interactions between the Wnt and Ras signaling pathways during each stage of bone metastasis and present the fate of those interactions. This review contributes insights that can guide other researchers by unveiling more details with regard to bone metastasis and might also help in finding potential therapeutic regimens for preventing PCa bone metastasis.

ZBTB46, SPDEF, and ETV6: Novel Potential Biomarkers and Therapeutic Targets in Castration-Resistant Prostate Cancer.

Prostate cancer (PCa) is the second most common killer among men in Western countries. Targeting androgen receptor (AR) signaling by androgen deprivation therapy (ADT) is the current therapeutic regime for patients newly diagnosed with metastatic PCa. However, most patients relapse and become resistant to ADT, leading to metastatic castration-resistant PCa (CRPC) and eventually death. Several proposed mechanisms have been proposed for CRPC; however, the exact mechanism through which CRPC develops is still unclear. One possible pathway is that the AR remains active in CRPC cases. Therefore, understanding AR signaling networks as primary PCa changes into metastatic CRPC is key to developing future biomarkers and therapeutic strategies for PCa and CRPC. In the current review, we focused on three novel biomarkers (ZBTB46, SPDEF, and ETV6) that were demonstrated to play critical roles in CRPC progression, epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) drug resistance, and the epithelial-to-mesenchymal transition (EMT) for patients treated with ADT or AR inhibition. In addition, we summarize how these potential biomarkers can be used in the clinic for diagnosis and as therapeutic targets of PCa.

Leukemia Inhibitory Factor Promotes Castration-resistant Prostate Cancer and Neuroendocrine Differentiation by Activated ZBTB46.

PURPOSE: The molecular targets for castration-resistant prostate cancer (CRPC) are unknown because the disease inevitably recurs, and therapeutic approaches for patients with CRPC remain less well understood. We sought to investigate regulatory mechanisms that result in increased therapeutic resistance, which is associated with neuroendocrine differentiation of prostate cancer and linked to dysregulation of the androgen-responsive pathway. EXPERIMENTAL DESIGN: The underlying intracellular mechanism that sustains the oncogenic network involved in neuroendocrine differentiation and therapeutic resistance of prostate cancer was evaluated to investigate and identify effectors. Multiple sets of samples with prostate adenocarcinomas and CRPC were assessed via IHC and other assays. RESULTS: We demonstrated that leukemia inhibitory factor (LIF) was induced by androgen deprivation therapy (ADT) and was upregulated by ZBTB46 in prostate cancer to promote CRPC and neuroendocrine differentiation. LIF was found to be induced in patients with prostate cancer after ADT and was associated with enriched nuclear ZBTB46 staining in high-grade prostate tumors. In prostate cancer cells, high ZBTB46 output was responsible for the activation of LIF-STAT3 signaling and neuroendocrine-like features. The abundance of LIF was mediated by ADT-induced ZBTB46 through a physical interaction with the regulatory sequence of LIF. Analysis of serum from patients showed that cases of higher tumor grade and metastatic prostate cancer exhibited higher LIF titers. CONCLUSIONS: Our findings suggest that LIF is a potent serum biomarker for diagnosing advanced prostate cancer and that targeting the ZBTB46-LIF axis may therefore inhibit CRPC development and neuroendocrine differentiation after ADT.

The synthetic retinoid ST1926 attenuates prostate cancer growth and potentially targets prostate cancer stem-like cells.

Retinoids are vitamin A derivatives that regulate crucial biological processes such as cellular proliferation, apoptosis, and differentiation. The use of natural retinoids in cancer therapy is limited due to their toxicity and the acquired resistance by cancer cells. Therefore, synthetic retinoids were developed, such as the atypical adamantyl retinoid ST1926 that provides enhanced bioavailability and reduced toxicity. We have assessed the in vitro and in vivo antitumor properties and mechanism of action of ST1926 in targeting cancer stem-like cells population of human prostate cancer (PCa) cell lines, DU145 and PC3, and mouse PCa cell lines, PLum-AD and PLum-AI. We demonstrated that ST1926 substantially reduced proliferation of PCa cells and induced cell cycle arrest, p53-independent apoptosis, and early DNA damage. It also decreased migration and invasion of PCa cells and significantly reduced prostate spheres formation ability in vitro denoting sufficient eradication of the self-renewal ability of the highly androgen-resistant cancer stem cells. Importantly, ST1926 potently inhibited PCa tumor growth and progression in vivo. Our results highlight the potential of ST1926 in PCa therapy and warrant its clinical development.

RAB14 activates MAPK signaling to promote bladder tumorigenesis.

Bladder cancer (BC) is a fatal invasive malignancy accounting for approximately 5% of all cancer deaths in humans; however, the underlying molecular mechanisms and potential targeted therapeutics for BC patients remain unclear. We report herein that RAB14 was overexpressed in BC tissues and cells with high metastatic potential and its abundance was significantly associated with lymph node metastasis (P = 0.001), a high-grade tumor stage (P = 0.009), poor differentiation (P < 0.001) and unfavorable prognoses of BC patients (P = 0.003, log-rank test). Interference by RAB14 mediated a reduction in the TWIST1 protein and inhibited cell migration and invasion (P < 0.05). Moreover, silencing RAB14 reduced cell proliferation and induced apoptosis in vitro and suppressed tumorigenesis in a mouse xenograft model. We demonstrated that RAB14-promoted BC cancer development and progression were associated with activation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase signaling through upregulation of MAPK1/MAPK8 and downregulation of dual-specificity protein phosphatase 6/Src homology 2 domain containing transforming protein/Fos proto-oncogene, AP-1 transcription factor subunit (FOS). We provide evidence that RAB14 acts as a tumor promoter and modulates the invasion and metastatic potential of BC cells via activating the MAPK pathway.

Androgen deprivation-induced ZBTB46-PTGS1 signaling promotes neuroendocrine differentiation of prostate cancer.

Androgen receptor (AR) targeting is an important therapeutic strategy for treating prostate cancer. Most tumors progress to castration-resistant prostate cancer (CRPC) and develop the neuroendocrine (NE) phenotype under androgen deprivation therapy (ADT). The molecular basis for NE transdifferentiation after ADT remains incompletely understood. Herein, we show that an immunocyte expression protein, ZBTB46, induces inflammatory response gene expression and contributes to NE differentiation of prostate cancer cells. We demonstrated a molecular mechanism whereby ZBTB46 can be regulated by the androgen-responsive gene, SPDEF, and is associated with NE prostate cancer (NEPC) differentiation. In addition, ZBTB46 acts as a transcriptional coactivator that binds to the promoter of prostaglandin-endoperoxide synthase 1 (PTGS1) and transcriptionally regulated PTGS1 levels. Overexpression of ZBTB46 decreases the sensitivity of the combination of enzalutamide and a PTGS1 inhibitor; however, knockdown of ZBTB46 sensitizes the PTGS1 inhibitor and reduces tumor malignancy. ZBTB46 is inversely correlated with SPDEF and is increased in higher tumor grades and small-cell NE prostate cancer (SCNC) patients, which are positively associated with PTGS1. Our findings suggest that the induction of ZBTB46 results in increased PTGS1 expression, which is associated with NEPC progression and linked to the dysregulation of the AR-SPDEF pathway.