Molecular model for neuroendocrine prostate cancer progression

The interplay between autophagy and ferroptosis presents a novel conceptual therapeutic framework for neuroendocrine prostate cancer

In American men, the incidence of prostate cancer (PC) is the highest among all types of cancer, making it the second leading cause of mortality associated with cancer. For advanced or metastatic PC, antiandrogen therapies are standard treatment options. The administration of these treatments unfortunately carries the potential risk of inducing neuroendocrine prostate cancer (NEPC). Neuroendocrine differentiation (NED) serves as a crucial indicator of prostate cancer development, encompassing various factors such as phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR), Yes-associated protein 1 (YAP1), AMP-activated protein kinase (AMPK), miRNA. The processes of autophagy and ferroptosis (an iron-dependent form of programmed cell death) play pivotal roles in the regulation of various types of cancers. Clinical trials and preclinical investigations have been conducted on many signaling pathways during the development of NEPC, with the deepening of research, autophagy and ferroptosis appear to be the potential target for regulating NEPC. Due to the dual nature of autophagy and ferroptosis in cancer, gaining a deeper understanding of the developmental programs associated with achieving autophagy and ferroptosis may enhance risk stratification and treatment efficacy for patients with NEPC.

Development and Characterisation of a New Patient-Derived Xenograft Model of AR-Negative Metastatic Castration-Resistant Prostate Cancer

As the treatment landscape for prostate cancer gradually evolves, the frequency of treatment-induced neuroendocrine prostate cancer (NEPC) and double-negative prostate cancer (DNPC) that is deficient for androgen receptor (AR) and neuroendocrine (NE) markers has increased. These prostate cancer subtypes are typically refractory to AR-directed therapies and exhibit poor clinical outcomes. Only a small range of NEPC/DNPC models exist, limiting our molecular understanding of this disease and hindering our ability to perform preclinical trials exploring novel therapies to treat NEPC/DNPC that are urgently needed in the clinic. Here, we report the development of the CU-PC01 PDX model that represents AR-negative mCRPC with PTEN/RB/PSMA loss and CTNN1B/TP53/BRCA2 genetic variants. The CU-PC01 model lacks classic NE markers, with only focal and/or weak expression of chromogranin A, INSM1 and CD56. Collectively, these findings are most consistent with a DNPC phenotype. Ex vivo and in vivo preclinical studies revealed that CU-PC01 PDX tumours are resistant to mCRPC standard-of-care treatments enzalutamide and docetaxel, mirroring the donor patient's treatment response. Furthermore, short-term CU-PC01 tumour explant cultures indicate this model is initially sensitive to PARP inhibition with olaparib. Thus, the CU-PC01 PDX model provides a valuable opportunity to study AR-negative mCRPC biology and to discover new treatment avenues for this hard-to-treat disease.

Treatment-related Neuroendocrine Prostate Carcinoma-Diagnostic and Molecular Correlates

Treatment-related neuroendocrine prostate cancer is a distinctive category of prostate cancer that arises after intensive suppression of the androgen receptor by next-generation therapeutic inhibition of androgen receptor signaling. The biological processes that set in motion the series of events resulting in transformation of adenocarcinoma to neuroendocrine carcinoma include genomic (loss of tumor suppressors TP53 and RB1, amplification of oncogenes N-MYC and Aurora Kinase A, dysregulation of transcription factors SOX2, achaete-scute-homolog 1, and others) as well as epigenomic (DNA methylation, EZH2 overexpression, and others). Pathologic diagnosis is key to effective therapy for this disease, and this is aided by localizing metastatic lesions for biopsy using radioligand imaging in the appropriate clinical context. As our understanding of biology evolves, there has been increased morphologic recognition and characterization of tumor phenotypes that are present in this advanced post-treatment setting. New and promising biomarkers (delta-like ligand 3 and others) have been discovered, which opens up novel therapeutic avenues including immunotherapy and antibody-drug conjugates for this lethal disease with currently limited treatment options.

ID2 Promotes Lineage Transition of Prostate Cancer through FGFR and JAK-STAT Signaling

The use of androgen receptor pathway inhibitors (ARPIs) has led to an increase in the proportion of AR-null prostate cancer, including neuroendocrine prostate cancer (NEPC) and double-negative prostate cancer (DNPC), but the mechanism underlying this lineage transition has not been elucidated. We found that ID2 expression was increased in AR-null prostate cancer. In vitro and in vivo studies confirmed that ID2 promotes PCa malignancy and can confer resistance to enzalutamide in PCa cells. We generated an ID2 UP50 signature, which is capable of determining resistance to enzalutamide and is valuable for predicting patient prognosis. Functional experiments showed that ID2 could activate stemness-associated JAK/STAT and FGFR signaling while inhibiting the AR signaling pathway. Our study indicates a potentially strong association between ID2 and the acquisition of a stem-like phenotype in adenocarcinoma cells, leading to resistance to androgen deprivation therapy (ADT) and next-generation ARPIs in prostate cancer.

Calcium signalling pathways in prostate cancer initiation and progression

Cancer cells proliferate, differentiate and migrate by repurposing physiological signalling mechanisms. In particular, altered calcium signalling is emerging as one of the most widespread adaptations in cancer cells. Remodelling of calcium signalling promotes the development of several malignancies, including prostate cancer. Gene expression data from in vitro, in vivo and bioinformatics studies using patient samples and xenografts have shown considerable changes in the expression of various components of the calcium signalling toolkit during the development of prostate cancer. Moreover, preclinical and clinical evidence suggests that altered calcium signalling is a crucial component of the molecular re-programming that drives prostate cancer progression. Evidence points to calcium signalling re-modelling, commonly involving crosstalk between calcium and other cellular signalling pathways, underpinning the onset and temporal progression of this disease. Discrete alterations in calcium signalling have been implicated in hormone-sensitive, castration-resistant and aggressive variant forms of prostate cancer. Hence, modulation of calcium signals and downstream effector molecules is a plausible therapeutic strategy for both early and late stages of prostate cancer. Based on this premise, clinical trials have been undertaken to establish the feasibility of targeting calcium signalling specifically for prostate cancer.

AR antagonists develop drug resistance through TOMM20 autophagic degradation-promoted transformation to neuroendocrine prostate cancer

BACKGROUND

Prostate cancer(PCa) is the most commonly occurring male cancer in the USA. Abiraterone or Enzalutamide have been approved for the treatment of metastatic castration-resistant prostate cancer (CRPC). However, the treatment-emergent neuroendocrine PCa (t-NEPC) may develop, resulting in drug resistance in about 10-17% CRPC patients. The detailed mechanisms remain unclear..

METHODS

The expression correlation of TOMM20 and AR in PCa was determined by analyzing publicly available datasets, or by IHC staining in tumor specimens. The protein interaction of TOMM20 and AR was validated by co-immunoprecipitation or GST pull-down assay. The impact of TOMM20 depletion on drug sensitivity were elucidated by assays of cell proliferation, invasion, sphere formation, xenograft growth and intravenous metastasis. The intracellular ROS level was measured by flow cytometry, and the NEPC transdifferentiation and characteristics of cancer stem-like cells were validated by RNA-seq, RT-PCR and western blotting.

RESULTS

The protein level of TOMM20 is positively correlated with AR in PCa cells and specimens. TOMM20 protein physically interacts with AR. AR antagonists induced the protein degradation of TOMM20 through autophagy-lysosomal pathway, thereby elevating the intracellular ROS level and activating PI3K/AKT signaling pathway. When TOMM20 was depleted, PCa cells underwent EMT, acquired the characteristics of cancer stem-like cells, and developed resistance to AR antagonists. The stable depletion of TOMM20 promoted the transdifferentiation of PCa adenocarcinoma into NEPC and metastasis. Conversely, the rescue of TOMM20 re-sensitized the resistant PCa cells to AR antagonists.

CONCLUSIONS

TOMM20 protein degradation induced by AR antagonists promoted the transdifferentiation of PCa to NEPC, thereby revealing a novel molecular mechanism by which AR antagonists develop drug resistance through mitochondrial outer membrane-mediated signaling pathway. These findings suggested that the decreasing or loss of TOMM20 expression in PCa tissues might become a useful predictor of PCa resistance to AR antagonists.

The Molecular Basis and Clinical Consequences of Chronic Inflammation in Prostatic Diseases: Prostatitis, Benign Prostatic Hyperplasia, and Prostate Cancer

Chronic inflammation is now recognized as one of the major risk factors and molecular hallmarks of chronic prostatitis, benign prostatic hyperplasia (BPH), and prostate tumorigenesis. However, the molecular mechanisms by which chronic inflammation signaling contributes to the pathogenesis of these prostate diseases are poorly understood. Previous efforts to therapeutically target the upstream (e.g., TLRs and IL1-Rs) and downstream (e.g., NF-κB subunits and cytokines) inflammatory signaling molecules in people with these conditions have been clinically ambiguous and unsatisfactory, hence fostering the recent paradigm shift towards unraveling and understanding the functional roles and clinical significance of the novel and relatively underexplored inflammatory molecules and pathways that could become potential therapeutic targets in managing prostatic diseases. In this review article, we exclusively discuss the causal and molecular drivers of prostatitis, BPH, and prostate tumorigenesis, as well as the potential impacts of microbiome dysbiosis and chronic inflammation in promoting prostate pathologies. We specifically focus on the importance of some of the underexplored druggable inflammatory molecules, by discussing how their aberrant signaling could promote prostate cancer (PCa) stemness, neuroendocrine differentiation, castration resistance, metabolic reprogramming, and immunosuppression. The potential contribution of the IL1R-TLR-IRAK-NF-κBs signaling molecules and NLR/inflammasomes in prostate pathologies, as well as the prospective benefits of selectively targeting the midstream molecules in the various inflammatory cascades, are also discussed. Though this review concentrates more on PCa, we envision that the information could be applied to other prostate diseases. In conclusion, we have underlined the molecular mechanisms and signaling pathways that may need to be targeted and/or further investigated to better understand the association between chronic inflammation and prostate diseases.

Spatial Gene Expression Analysis Reveals Characteristic Gene Expression Patterns of De Novo Neuroendocrine Prostate Cancer Coexisting with Androgen Receptor Pathway Prostate Cancer

Neuroendocrine prostate carcinoma (NEPC) accounts for less than 1% of prostate neoplasms and has extremely poorer prognosis than the typical androgen receptor pathway-positive adenocarcinoma of the prostate (ARPC). However, very few cases in which de novo NEPC and APRC are diagnosed simultaneously in the same tissue have been reported. We report herein a 78-year-old man of de novo metastatic NEPC coexisting with ARPC treated at Ehime University Hospital. Visium CytAssist Spatial Gene Expression analysis (10× genetics) was performed using formalin-fixed, paraffin-embedded (FFPE) samples. The neuroendocrine signatures were upregulated in NEPC sites, and androgen receptor signatures were upregulated in ARPC sites. TP53, RB1, or PTEN and upregulation of the homologous recombination repair genes at NEPC sites were not downregulated. Urothelial carcinoma markers were not elevated. Meanwhile, Rbfox3 and SFRTM2 levels were downregulated while the levels of the fibrosis markers HGF, HMOX1, ELN, and GREM1 were upregulated in the tumor microenvironment of NEPC. In conclusion, the findings of spatial gene expression analysis in a patient with coexisting ARPC and de novo NEPC are reported. The accumulation of cases and basic data will help with the development of novel treatments for NEPC and improve the prognosis of patients with castration-resistant prostate cancer.

Therapeutic targeting of histone lysine demethylase KDM4B blocks the growth of castration-resistant prostate cancer

Epigenetics is an emerging mechanism for tumorigenesis. Treatment that targets epigenetic regulators is becoming an attractive strategy for cancer therapy. The role of epigenetic therapy in prostate cancer (PCa) remains elusive. Previously we demonstrated that upregulation of histone lysine demethylase KDM4B correlated with the appearance of castration resistant prostate cancer (CRPC) and identified a small molecular inhibitor of KDM4B, B3. In this study, we further investigated the role of KDM4B in promoting PCa progression and tested the efficacy of B3 using clinically relevant PCa models including PCa cell line LNCaP and 22Rv1 and xenografts derived from these cell lines. In loss and gain-functional studies of KDM4B in PCa cells, we found that overexpression of KDM4B in LNCaP cells enhanced its tumorigenicity whereas knockdown of KDM4B in 22Rv1 cells reduced tumor growth in castrated mice. B3 suppressed the growth of 22Rv1 xenografts and sensitized tumor to anti-androgen receptor (AR) antagonist enzalutamide inhibition. B3 also inhibited 22Rv1 tumor growth synergistically with rapamycin, leading to cell apoptosis. Comparative transcriptomic analysis performed on KDM4B knockdown and B3-treated 22Rv1 cells revealed that B3 inhibited both H3K9me3 and H3K27me3 demethylase activities. Our studies establish KDM4B as a target for CRPC and B3 as a potential therapeutic agent. B3 as monotherapy or in combination with other anti-PCa therapeutics offers proof of principle for the clinical translation of epigenetic therapy targeting KDMs for CRPC patients.

A bibliometric study of the top 100 most-cited papers in neuroendocrine prostate cancer

Background

This study used bibliometrics to define and analyze the characteristics of the first 100 most cited papers on the topic of neuroendocrine prostate cancer (NEPC).

Methods

We explored the Web of Science Core Collection database, and screened the top 100 most frequently cited articles and reviews with the title NEPC or small cell prostate cancer (SCPC). We conducted bibliometrics research on the screening results to identify the most influential journals and authors in the field of NEPC.

Results

The first 100 most cited papers have been cited a total of 14,795 times, from 73 to 833 times (mean ± standard deviation, 147.95 ± 101.68). All top 100 most cited papers were published from 1984 to 2019, and the total number of citations for papers published in 2016 was significantly higher than that for papers published in other years. The journal with the largest number of published papers is "Prostate" (n=8). "Neuroendocrine differentiation" has become the most frequently used author keyword. "Oncology" is the most popular topic in the field of NEPC.

Conclusion

We analyzed the first 100 most cited papers in the NEPC field by collecting detailed information, which provide guiding opinions for finding the most influential journals and authors in NEPC-related fields. We hope to help researchers and readers in this field improve their understanding of NEPC research trends and provide ideas for future research from a unique perspective.

Molecular mechanisms underlying the development of neuroendocrine prostate cancer

Prostate cancer is the most common non-cutaneous cancer and the second leading cause of cancer-associated deaths among men in the United States. Androgen deprivation therapy (ADT) is the standard of care for advanced prostate cancer. While patients with advanced prostate cancer initially respond to ADT, the disease frequently progresses to a lethal metastatic form, defined as castration-resistant prostate cancer (CRPC). After multiple rounds of anti-androgen therapies, 20-25% of metastatic CRPCs develop a neuroendocrine (NE) phenotype. These tumors are classified as neuroendocrine prostate cancer (NEPC). De novo NEPC is rare and accounts for less than 2% of all prostate cancers at diagnosis. NEPC is commonly characterized by the expression of NE markers and the absence of androgen receptor (AR) expression. NEPC is usually associated with tumor aggressiveness, hormone therapy resistance, and poor clinical outcome. Here, we review the molecular mechanisms underlying the emergence of NEPC and provide insights into the future perspectives on potential therapeutic strategies for NEPC.

Identification and Validation of Three Hub Genes Involved in Cell Proliferation and Prognosis of Castration-Resistant Prostate Cancer

Background

The acquisition of castration resistance is lethal and inevitable in most prostate cancer patients under hormone therapy. However, effective biomarkers and therapeutic targets for castration-resistant prostate cancer remain to be defined.

Methods

Comprehensive bioinformatics tools were used to screen hub genes in castration-resistant prostate cancer and were verified in androgen-dependent prostate cancer and castration-resistant prostate cancer in TCGA and the SU2C/PCF Dream Team database, respectively. Gene set enrichment analysis and in vitro experiments were performed to determine the potential functions of hub genes involved in castration-resistant prostate cancer progression.

Results

Three hub genes were screened out by bioinformatics analysis: MCM4, CENPI, and KNTC1. These hub genes were upregulated in castration-resistant prostate cancer and showed high diagnostic and prognostic value. Moreover, the expression levels of the hub genes were positively correlated with neuroendocrine prostate cancer scores, which represent the degree of castration-resistant prostate cancer aggression. Meanwhile, in vitro experiments confirmed that hub gene expression was increased in castration-resistant prostate cancer cell lines and that inhibition of hub genes hindered cell cycle transition, resulting in suppression of castration-resistant prostate cancer cell proliferation, which confirmed the gene set enrichment analysis results.

Conclusions

MCM4, CENPI, and KNTC1 could serve as candidate diagnostic and prognostic biomarkers of castration-resistant prostate cancer and may provide potential preventive and therapeutic targets.

Focus on the tumor microenvironment: A seedbed for neuroendocrine prostate cancer

The tumor microenvironment (TME) is a microecology consisting of tumor and mesenchymal cells and extracellular matrices. The TME plays important regulatory roles in tumor proliferation, invasion, metastasis, and differentiation. Neuroendocrine differentiation (NED) is a mechanism by which castration resistance develops in advanced prostate cancer (PCa). NED is induced after androgen deprivation therapy and neuroendocrine prostate cancer (NEPC) is established finally. NEPC has poor prognosis and short overall survival and is a major cause of death in patients with PCa. Both the cellular and non-cellular components of the TME regulate and induce NEPC formation through various pathways. Insights into the roles of the TME in NEPC evolution, growth, and progression have increased over the past few years. These novel insights will help refine the NEPC formation model and lay the foundation for the discovery of new NEPC therapies targeting the TME.

Advances in neuroendocrine prostate cancer research: From model construction to molecular network analyses

Prostate cancer is the most common cancer among men and has a high incidence and associated mortality worldwide. It is an androgen-driven disease in which tumor growth is triggered via ligand-mediated signaling through the androgen receptor (AR). Recent evidence suggests that the widespread use of effective AR pathway inhibitors may increase the occurrence of neuroendocrine prostate cancer (NEPC), an aggressive and treatment-resistant AR-negative variant; however, mechanisms controlling NEPC development remain to be elucidated. Various preclinical models have recently been developed to investigate the mechanisms driving the NEPC differentiation. In the present study, we summarized strategies for the development of NEPC models and proposed a novel method for model evaluation, which will help in the timely and accurate identification of NEPC by virtue of its ability to recapitulate the heterogeneity of prostate cancer. Moreover, we discuss the origin and the mechanism of NEPC. The understanding of the regulatory network mediating neuroendocrine differentiation presented in this review could provide valuable insights into the identification of novel drug targets for NEPC as well as into the causes of antiandrogenic drug resistance.

Reprogramming hormone sensitive prostate cancer to a lethal neuroendocrine cancer lineage by mitochondrial pyruvate carrier (MPC)

Cell lineage reprogramming is the main approach for cancer cells to acquire drug resistance and escape targeted therapy. The use of potent targeted therapies in cancers has led to the development of highly aggressive carcinoma, including neuroendocrine prostate cancer (NEPC). Although metabolic reprogramming has been reported to be essential for tumor growth and energy production, the relationship between metabolic reprogramming and lineage differentiation which can cause hormone therapy resistance has never been reported in prostate cancer (PCa). Moreover, as there is still no efficient therapy for NEPC, it is urgent to reverse this lineage differentiation during the hormone therapy. Here for the first time, we used in vitro and in vivo human PCa models to study the effect of metabolic reprogramming on the lineage differentiation from the androgen receptor (AR)–dependent adenocarcinoma to AR-independent NEPC. This lineage differentiation leads to antiandrogen drug resistance and tumor development. This phenotype is enabled by the loss of mitochondrial pyruvate carrier (MPC), the gate for mitochondrial pyruvate influx, and can be reversed by MPC overexpression. Morphologic and cellular studies also demonstrate that the pyruvate kinase M2 (PKM2) involved epithelium–mesenchymal transition process mediated this lineage alteration. Its inhibition is a potential treatment for MPC-lo tumors. All of these results suggest that metabolic rewiring can act as a starter for increased cellular plasticity which leads to antiandrogen therapy resistance through lineage differentiation. This study provides us with a potent treatment target for therapy-induced, enzalutamide-resistant NE-like prostate cancer.

1.

Metabolic rewiring induced by mitochondrial pyruvate carrier (MPC) loss can act as a starter for increased cellular lineage plasticity from adenocarcinoma into neuroendocrine prostate cancer (NEPC).

2.

An M2-pyruvate kinase (PKM2) involved epithelium–mesenchymal transition (EMT) process mediated this lineage switch from the androgen receptor (AR)–dependent adenocarcinoma to AR-independent neuroendocrine prostate cancer (NEPC); this process is induced by the decrease of mitochondria pyruvate influx.

3.

Mitochondria pyruvate influx can be a potential target for the NEPC treatment.

Targeting protein arginine methyltransferase 5 (PRMT5) suppresses radiation-induced neuroendocrine differentiation and sensitizes prostate cancer cells to radiation

Prostate cancer remains the second leading cause of cancer death among American men. Radiation therapy (RT) is a potentially curative treatment for localized prostate cancer, and failure to control localized disease contributes to the majority of prostate cancer deaths. Neuroendocrine differentiation (NED) in prostate cancer, a process by which prostate adenocarcinoma cells transdifferentiate into neuroendocrine-like (NE-like) cells, is an emerging mechanism of resistance to cancer therapies and contributes to disease progression. NED also occurs in response to treatment to promote the development of treatment-induced neuroendocrine prostate cancer (NEPC), a highly-aggressive and terminal stage disease. We previously demonstrated that by mimicking clinical RT protocol, fractionated ionizing radiation (FIR) induces prostate cancer cells to undergo NED in vitro and in vivo. Here, we performed transcriptomic analysis and confirmed that FIR-induced NE-like cells share some features of clinical NEPC, suggesting that FIR-induced NED represents a clinically-relevant model. Further, we demonstrated that protein arginine methyltransferase 5 (PRMT5), a master epigenetic regulator of the DNA damage response and a putative oncogene in prostate cancer, along with its cofactors pICln and MEP50, mediate FIR-induced NED. Knockdown of PRMT5, pICln, or MEP50 during FIR-inhibited NED sensitized prostate cancer cells to radiation. Significantly, PRMT5 knockdown in prostate cancer xenograft tumors in mice during FIR prevented NED, enhanced tumor killing, significantly reduced and delayed tumor recurrence, and prolonged overall survival. Collectively, our results demonstrate that PRMT5 promotes FIR-induced NED and suggests that targeting PRMT5 may be a novel and effective radiosensitization approach for prostate cancer RT.

ELOVL5-Mediated Long Chain Fatty Acid Elongation Contributes to Enzalutamide Resistance of Prostate Cancer

Simple Summary

The resistance mechanism of hormonal therapy has been a long-sought-after but not-yet-understood research topic in the prostate cancer (PCa) field. Here, we provide new mechanistic insights into how long-chain fatty acid contributes to enzalutamide resistance of prostate cancer. We demonstrated that ELOLV5-mediated polyunsaturated fatty acids (PUFAs) upregulation and the lipid raft-derived activation of AKT-mTOR pathway drives the therapy resistance and neuroendocrine differentiation (NED) of prostate cancer. Thus, ELOVL5 could be a potential candidate for therapeutically targeting the therapy-resistant NE-like PCa.

Abstract

Prostate cancer (PCa) exhibits an elevated level of de novo lipogenesis that provides both energy and basic metabolites for its malignant development. Long-chain polyunsaturated fatty acids (PUFAs) are elongated and desaturated from palmitate but their effects on PCa progression remain largely unknown. Here, we showed that PUFAs were significantly upregulated by androgen deprivation therapy (ADT) and elevated in neuroendocrine (NE)-like PCa cells. The key enzyme of PUFA elongation, ELOVL5, was overexpressed in NE-like PCa cells as well. Furthermore, we demonstrated that knocking down ELOVL5 in enzalutamide resistant NE-like PCa cells diminished the neuroendocrine phenotypes and enzalutamide resistance, while overexpressing ELOVL5 augmented the enzalutamide resistance of PCa cells in vitro and in vivo. Mechanistically, ELOVL5-mediated PUFA elongation enhanced the lipid raft-associated AKT-mTOR signaling activation and therefore contributes to the enzalutamide resistance. These findings suggest that ELOLV5-mediated PUFA elongation may be a potential novel target for the treatment of enzalutamide resistant NE-like PCa.

Comparative study of neuroendocrine acquisition and biomarker expression between neuroendocrine and usual prostatic carcinoma

BACKGROUND

Neuroendocrine prostatic carcinoma (NEPC) is uncommon. The pathogenesis, clinical association, and clinical implications of this disease are still evolving.

METHODS

Clinicopathologic, immunohistochemical and genomic studies were used to investigate the incidence of NEPC in various clinicopathologic settings and the expression of various biomarkers in NEPC and non-NEPC as well as small cell NEPC. The study included 45 treatment-naïve Gleason pattern (GP) 3 and 94 GP 4/5, 43 post-radiation, 60 post-androgen deprivation therapy (ADT), 38 lymph node metastatic and 9 small cell prostatic adenocarcinomas (PCs).

RESULTS

NEPC was found in 7% GP3, 10% GP4/5, 9% post-radiation, 18% post-ADT, and 5% lymph node metastatic PCs, respectively. Compared with treatment-naïve PCs, post-ADT PCs showed significantly increased incidence of NEPC (p < .05) while no significant difference was noted between low- and high-grade PCs, post-radiation, and lymph node metastatic PCs. Serotonin was uniformly positive in NE cells of benign glands but negative in NEPC. Significant increase of Bcl-2 and Auro A and decrease of prostein were noted in NEPC (p < .05). No significant changes in the expression of other biomarkers were found. In addition, small cell NEPC was strongly associated with ADT (44%) and high Gleason score (≥8, 100%) and often presented with alterations of TP53/RB1 and ARID1A/B or other genes crucial to genomic fidelity.

CONCLUSION

Given that no specific treatment for NEPC is presently available, the findings in this study have significant implications in the better understanding of this often-deadly disease both clinically and pathogenetically as well as future patient management, including targeted therapy.

Novel Target Opportunities in Non-Metastatic Castrate Resistant Prostate Cancer

Nearly one third of men will incur biochemical recurrence after treatment for localized prostate cancer. Androgen deprivation therapy (ADT) is the therapeutic mainstay; however, some patients will transition to a castrate resistant state (castrate resistant prostate cancer, CRPC). Subjects with CRPC may develop symptomatic metastatic disease (mCRPC) and incur mortality several years later. Prior to metastatic disease, however, men acquire non-metastatic CRPC (nmCRPC) which lends the unique opportunity for intervention to delay disease progression and symptoms. This review addresses current therapies for nmCRPC, as well as novel therapeutics and pathway strategies targeting men with nmCRPC.

The evolutionarily conserved long non-coding RNA LINC00261 drives neuroendocrine prostate cancer proliferation and metastasis via distinct nuclear and cytoplasmic mechanisms

Metastatic neuroendocrine prostate cancer (NEPC) is a highly aggressive disease, whose incidence is rising. Long noncoding RNAs (lncRNAs) represent a large family of disease- and tissue-specific transcripts, most of which are still functionally uncharacterized. Thus, we set out to identify the highly conserved lncRNAs that play a central role in NEPC pathogenesis. To this end, we performed transcriptomic analyses of donor-matched patient-derived xenograft models (PDXs) with immunohistologic features of prostate adenocarcinoma (AR⁺ /PSA⁺ ) or NEPC (AR^- /SYN⁺ /CHGA⁺ ) and through differential expression analyses identified lncRNAs that were upregulated upon neuroendocrine transdifferentiation. These genes were prioritized for functional assessment based on the level of conservation in vertebrates. Here, LINC00261 emerged as the top gene with over 3229-fold upregulation in NEPC. Consistently, LINC00261 expression was significantly upregulated in NEPC specimens in multiple patient cohorts. Knockdown of LINC00261 in PC-3 cells dramatically attenuated its proliferative and metastatic abilities, which are explained by parallel downregulation of CBX2 and FOXA2 through distinct molecular mechanisms. In the cell cytoplasm, LINC00261 binds to and sequesters miR-8485 from targeting the CBX2 mRNA, while inside the nucleus, LINC00261 functions as a transcriptional scaffold to induce SMAD-driven expression of the FOXA2 gene. For the first time, these results demonstrate hyperactivation of the LINC00261-CBX2-FOXA2 axes in NEPC to drive proliferation and metastasis, and that LINC00261 may be utilized as a therapeutic target and a biomarker for this incurable disease.

Deficiency of NEIL3 Enhances the Chemotherapy Resistance of Prostate Cancer

Acquired treatment resistance is an important cause of death in prostate cancer, and this study aimed to explore the mechanisms of chemotherapy resistance in prostate cancer. We employed castration-resistant prostate cancer (CRPC), neuroendocrine prostate cancer (NEPC), and chemotherapy-resistant prostate cancer datasets to screen for potential target genes. The Cancer Genome Atlas (TCGA) was used to detect the correlation between the target genes and prognosis and clinical characteristics. Nei endonuclease VIII-like 3 (NEIL3) knockdown cell lines were constructed with RNA interference. Prostate cancer cells were treated with enzalutamide for the androgen deprivation therapy (ADT) model, and with docetaxel and cisplatin for the chemotherapy model. Apoptosis and the cell cycle were examined using flow cytometry. RNA sequencing and western blotting were performed in the knockdown Duke University 145 (DU145) cell line to explore the possible mechanisms. The TCGA dataset demonstrated that high NEIL3 was associated with a high T stage and Gleason score, and indicated a possibility of lymph node metastasis, but a good prognosis. The cell therapy models showed that the loss of NEIL3 could promote the chemotherapy resistance (but not ADT resistance) of prostate cancer (PCa). Flow cytometry revealed that the loss of NEIL3 in PCa could inhibit cell apoptosis and cell cycle arrest under cisplatin treatment. RNA sequencing showed that the knockdown of NEIL3 changes the expression of neuroendocrine-related genes. Further western blotting revealed that the loss of NEIL3 could significantly promote the phosphorylation of ATR serine/threonine kinase (ATR) and ATM serine/threonine kinase (ATM) under chemotherapy, thus initiating downstream pathways related to DNA repair. In summary, the loss of NEIL3 promotes chemotherapy resistance in prostate cancer, and NEIL3 may serve as a diagnostic marker for chemotherapy-resistant patients.

Non-Coding RNAs Set a New Phenotypic Frontier in Prostate Cancer Metastasis and Resistance

Prostate cancer (PCa) mortality remains a significant public health problem, as advanced disease has poor survivability due to the development of resistance in response to both standard and novel therapeutic interventions. Therapeutic resistance is a multifaceted problem involving the interplay of a number of biological mechanisms including genetic, signaling, and phenotypic alterations, compounded by the contributions of a tumor microenvironment that supports tumor growth, invasiveness, and metastasis. The androgen receptor (AR) is a primary regulator of prostate cell growth, response and maintenance, and the target of most standard PCa therapies designed to inhibit AR from interacting with androgens, its native ligands. As such, AR remains the main driver of therapeutic response in patients with metastatic castration-resistant prostate cancer (mCRPC). While androgen deprivation therapy (ADT), in combination with microtubule-targeting taxane chemotherapy, offers survival benefits in patients with mCRPC, therapeutic resistance invariably develops, leading to lethal disease. Understanding the mechanisms underlying resistance is critical to improving therapeutic outcomes and also to the development of biomarker signatures of predictive value. The interconversions between epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET) navigate the prostate tumor therapeutic response, and provide a novel targeting platform in overcoming therapeutic resistance. Both microRNA (miRNA)- and long non-coding RNA (lncRNA)-mediated mechanisms have been associated with epigenetic changes in prostate cancer. This review discusses the current evidence-based knowledge of the role of the phenotypic transitions and novel molecular determinants (non-coding RNAs) as contributors to the emergence of therapeutic resistance and metastasis and their integrated predictive value in prostate cancer progression to advanced disease.

Androgen Receptor Signaling and the Emergence of Lethal Neuroendocrine Prostate Cancer With the Treatment-Induced Suppression of the Androgen Receptor: A Literature Review

Androgen receptor signaling primarily influences both the normal growth and proliferation of the prostate gland and the development of prostatic carcinoma. While localized prostate cancers are typically managed with definitive therapies like surgery and radiotherapy, many patients have recurrences in the form of metastatic disease. Androgen deprivation therapy, by way of castration via orchiectomy or with drugs like luteinizing hormone-releasing hormone (commonly called gonadotropin-releasing hormone) agonists and luteinizing hormone-releasing hormone antagonists, is the primary mode of therapy for advanced castration-sensitive prostate cancer. Castration resistance invariably develops in these patients. Further treatment has shifted to newer anti-androgen drugs like enzalutamide or abiraterone and taxane-based chemotherapy. Prolonged inhibition of the androgen receptor signaling pathway causes androgen receptor-independent clonal evolution which leads to the development of treatment-emergent neuroendocrine prostate cancer. All prostate cancers at the initial presentation should undergo evaluation for the markers of neuroendocrine differentiation. Detection of serum biomarkers of neuroendocrine differentiation and circulating tumor cells is a prospective non-invasive method of detecting neuroendocrine transdifferentiation in patients undergoing treatment with androgen receptor pathway inhibitors. It is essential to perform a biopsy in the presence of red flags of neuroendocrine differentiation. Alisertib, an Aurora kinase inhibitor, showed promising clinical benefit in a subgroup of patients with certain molecular alterations. A thorough understanding of the molecular and clinical programming of treatment-emergent neuroendocrine prostate cancer can potentially lead to the development of drugs to prevent the development of this lethal variant of prostate cancer.

Clinical and Biological Features of Neuroendocrine Prostate Cancer

PURPOSE OF REVIEW

Neuroendocrine prostate cancer (NEPC) is an aggressive histologic subtype of prostate cancer that most commonly arises in later stages of prostate cancer as a mechanism of treatment resistance. The poor prognosis of NEPC is attributed in part to late diagnosis and a lack of effective therapeutic agents. Here, we review the clinical and molecular features of NEPC based on recent studies and outline future strategies and directions.

RECENT FINDINGS

NEPC can arise "de novo" but most commonly develops as a result of lineage plasticity whereby prostate cancer cells adopt alternative lineage programs as a means to bypass therapy. Dependence on androgen receptor (AR) signaling is lost as tumors progress from a prostate adenocarcinoma to a NEPC histology, typically manifested by the downregulation of AR, PSA, and PSMA expression in tumors. Genomic analyses from patient biopsies combined with preclinical modeling have pointed to loss of tumor suppressors RB1 and TP53 as key facilitators of lineage plasticity. Activation of oncogenic drivers combined with significant epigenetic changes (e.g., EZH2 overexpression, DNA methylation) further drives tumor proliferation and expression of downstream neuronal and neuroendocrine lineage pathways controlled in part by pioneer and lineage determinant transcription factors (e.g., SOX2, ASCL1, BRN2). These biologic insights have provided a framework for the study of this subgroup of advanced prostate cancers and have started to provide rationale for the development of biomarker-driven therapeutic strategies. Further study of the dynamic process that leads to NEPC is required for the development of effective strategies to identify and treat patients developing lineage plasticity as a mechanism of treatment resistance.

The Intimate Relationship Among EMT, MET and TME: A T(ransdifferentiation) E(nhancing) M(ix) to Be Exploited for Therapeutic Purposes

Simple Summary

Intratumoral heterogeneity is considered the major cause of drug resistance and hence treatment failure in cancer patients. Tumor cells are known for their phenotypic plasticity that is the ability of a cell to reprogram and change its identity to eventually adopt multiple phenotypes. Tumor cell plasticity involves the reactivation of developmental programs, the acquisition of cancer stem cell properties and an enhanced potential for retro- or transdifferentiation. A well-known transdifferentiation mechanism is the process of epithelial-mesenchymal transition (EMT). Current evidence suggests a complex interplay between EMT, genetic and epigenetic alterations, and various signals from the tumor microenvironment (TME) in shaping a tumor cell’s plasticity. The vulnerabilities exposed by cancer cells when residing in a plastic or stem-like state have the potential to be exploited therapeutically, i.e., by converting highly metastatic cells into less aggressive or even harmless postmitotic ones.

Abstract

Intratumoral heterogeneity is considered the major cause of drug unresponsiveness in cancer and accumulating evidence implicates non-mutational resistance mechanisms rather than genetic mutations in its development. These non-mutational processes are largely driven by phenotypic plasticity, which is defined as the ability of a cell to reprogram and change its identity (phenotype switching). Tumor cell plasticity is characterized by the reactivation of developmental programs that are closely correlated with the acquisition of cancer stem cell properties and an enhanced potential for retrodifferentiation or transdifferentiation. A well-studied mechanism of phenotypic plasticity is the epithelial-mesenchymal transition (EMT). Current evidence suggests a complex interplay between EMT, genetic and epigenetic alterations, and clues from the tumor microenvironment in cell reprogramming. A deeper understanding of the connections between stem cell, epithelial–mesenchymal, and tumor-associated reprogramming events is crucial to develop novel therapies that mitigate cell plasticity and minimize the evolution of tumor heterogeneity, and hence drug resistance. Alternatively, vulnerabilities exposed by tumor cells when residing in a plastic or stem-like state may be exploited therapeutically, i.e., by converting them into less aggressive or even postmitotic cells. Tumor cell plasticity thus presents a new paradigm for understanding a cancer’s resistance to therapy and deciphering its underlying mechanisms.

MicroRNAs in treatment-induced neuroendocrine differentiation in prostate cancer

Prostate cancer is a condition commonly associated with men worldwide. Androgen deprivation therapy remains one of the targeted therapies. However, after some years, there is biochemical recurrence and metastatic progression into castration-resistant prostate cancer (CRPC). CRPC cases are treated with second-line androgen deprivation therapy, after which, these CRPCs transdifferentiate to form neuroendocrine prostate cancer (NEPC), a highly aggressive variant of CRPC. NEPC arises via a reversible transdifferentiation process, known as neuroendocrine differentiation (NED), which is associated with altered expression of lineage markers such as decreased expression of androgen receptor and increased expression of neuroendocrine lineage markers including enolase 2, chromogranin A and synaptophysin. The etiological factors and molecular basis for NED are poorly understood, contributing to a lack of adequate molecular biomarkers for its diagnosis and therapy. Therefore, there is a need to fully understand the underlying molecular basis for this cancer. Recent studies have shown that microRNAs (miRNAs) play a key epigenetic role in driving therapy-induced NED in prostate cancer. In this review, we briefly describe the role of miRNAs in prostate cancer and CRPCs, discuss some key players in NEPCs and elaborate on miRNA dysregulation as a key epigenetic process that accompanies therapy-induced NED in metastatic CRPC. This understanding will contribute to better clinical management of the disease.

Resistance to second generation antiandrogens in prostate cancer: pathways and mechanisms

Androgen deprivation therapy targeting the androgens/androgen receptor (AR) signaling continues to be the mainstay treatment of advanced-stage prostate cancer. The use of second-generation antiandrogens, such as abiraterone acetate and enzalutamide, has improved the survival of prostate cancer patients; however, a majority of these patients progress to castration-resistant prostate cancer (CRPC). The mechanisms of resistance to antiandrogen treatments are complex, including specific mutations, alternative splicing, and amplification of oncogenic proteins resulting in dysregulation of various signaling pathways. In this review, we focus on the major mechanisms of acquired resistance to second generation antiandrogens, including AR-dependent and AR-independent resistance mechanisms as well as other resistance mechanisms leading to CRPC emergence. Evolving knowledge of resistance mechanisms to AR targeted treatments will lead to additional research on designing more effective therapies for advanced-stage prostate cancer.

Androgen Deprivation Induces Reprogramming of Prostate Cancer Cells to Stem-Like Cells

In the past few years, cell plasticity has emerged as a mode of targeted therapy evasion in prostate adenocarcinoma. When exposed to anticancer therapies, tumor cells may switch into a different histological subtype, such as the neuroendocrine phenotype which is associated with treatment failure and a poor prognosis. In this study, we demonstrated that long-term androgen signal depletion of prostate LNCaP cells induced a neuroendocrine phenotype followed by re-differentiation towards a “stem-like” state. LNCaP cells incubated for 30 days in charcoal-stripped medium or with the androgen receptor antagonist 2-hydroxyflutamide developed neuroendocrine morphology and increased the expression of the neuroendocrine markers βIII-tubulin and neuron specific enolase (NSE). When cells were incubated for 90 days in androgen-depleted medium, they grew as floating spheres and had enhanced expression of the stem cell markers CD133, ALDH1A1, and the transporter ABCB1A. Additionally, the pluripotent transcription factors Nanog and Oct4 and the angiogenic factor VEGF were up-regulated while the expression of E-cadherin was inhibited. Cell viability revealed that those cells were resistant to docetaxel and 2-hidroxyflutamide. Mechanistically, androgen depletion induced the decrease in AMP-activated kinase (AMPK) expression and activation and stabilization of the hypoxia-inducible factor HIF-1α. Overexpression of AMPK in the stem-like cells decreased the expression of stem markers as well as that of HIF-1α and VEGF while it restored the levels of E-cadherin and PGC-1α. Most importantly, docetaxel sensitivity was restored in stem-like AMPK-transfected cells. Our model provides a new regulatory mechanism of prostate cancer plasticity through AMPK that is worth exploring.

Cell plasticity in cancer: A complex interplay of genetic, epigenetic mechanisms and tumor micro-environment

Cell plasticity, also known as lineage plasticity is defined as the ability of a cell to reprogram and change its phenotype identity. Cell plasticity is context dependent and occurs during the development of an embryo, tissue regeneration, wound healing. However when deregulated and aberrant it also contributes to cancer initiation, progression, metastases and resistance to therapies. Tumors cells exhibit varying forms of cell plasticity in each stage of the disease to evade normal regulation as would have occurred in normal cell division and homeostasis. Current evidence demonstrates complex interplay between the genes, epigenes, tumor microenvironment and the EMT in cell reprogramming and cancer cell plasticity. Herein we present experimental evidence and evolving new developments in cell plasticity in cancer cells. Additionally "Deregulated/aberrant/hijacked cell plasticity" could be considered as an additional hallmark of a cancer. In the future, combining the advances in next generation sequencing and single cell RNA techniques with evolving AI (artificial intelligence) technologies such as deep learning techniques may predict the trajectories of cancer cells and assist in navigating through the complex intricacies of the cancers. A durable, precise, personalized oncologic treatment could be a reality.

Molecular Links Between Angiogenesis and Neuroendocrine Phenotypes in Prostate Cancer Progression

As a common therapy for prostate cancer, androgen deprivation therapy (ADT) is effective for the majority of patients. However, prolonged ADT promotes drug resistance and progression to an aggressive variant with reduced androgen receptor signaling, so called neuroendocrine prostate cancer (NEPC). Until present, NEPC is still poorly understood, and lethal with no effective treatments. Elevated expression of neuroendocrine related markers and increased angiogenesis are two prominent phenotypes of NEPC, and both of them are positively associated with cancers progression. However, direct molecular links between the two phenotypes in NEPC and their mechanisms remain largely unclear. Their elucidation should substantially expand our knowledge in NEPC. This knowledge, in turn, would facilitate the development of effective NEPC treatments. We recently showed that a single critical pathway regulates both ADT-enhanced angiogenesis and elevated expression of neuroendocrine markers. This pathway consists of CREB1, EZH2, and TSP1. Here, we seek new insights to identify molecules common to pathways promoting angiogenesis and neuroendocrine phenotypes in prostate cancer. To this end, our focus is to summarize the literature on proteins reported to regulate both neuroendocrine marker expression and angiogenesis as potential molecular links. These proteins, often described in separate biological contexts or diseases, include AURKA and AURKB, CHGA, CREB1, EZH2, FOXA2, GRK3, HIF1, IL-6, MYCN, ONECUT2, p53, RET, and RB1. We also present the current efforts in prostate cancer or other diseases to target some of these proteins, which warrants testing for NEPC, given the urgent unmet need in treating this aggressive variant of prostate cancer.

Understanding aberrant RNA splicing to facilitate cancer diagnosis and therapy

Almost all genes in normal cells undergo alternative RNA splicing to generate a greater extent of diversification of gene products for normal cellular functions. RNA splicing is tightly regulated and closely interplays with genetic and epigenetic machinery. While DNA polymorphism and somatic mutations modulate alternative splicing patterns, RNA splicing also controls genomic stability, chromatin organization, and transcriptome. Tumor cells, in turn, often take advantage of aberrant RNA splicing to develop, grow and progress into therapy-resistant tumors. Understanding alternative RNA splicing in tumor cells would, therefore, provide us opportunities to gain further insights into tumor biology, identify diagnostic or prognosis biomarkers, as well as to design effective therapeutic means to control tumor progression. Here, we provide an overview of RNA splicing mechanisms and use prostate cancer as an example to review recent advancements in our understanding of RNA splicing in cancer progression and therapy resistance. We also discuss emerging diagnostic and therapeutic potentials of RNA splicing events or RNA splicing factors.

Phospholipase D2 in prostate cancer: protein expression changes with Gleason score

BACKGROUND

Phospholipases D1 and D2 (PLD1/2) are implicated in tumorigenesis through their generation of the signalling lipid phosphatidic acid and its downstream effects. Inhibition of PLD1 blocks prostate cell growth and colony formation. Here a role for PLD2 in prostate cancer (PCa), the major cancer of men in the western world, is examined.

METHODS

PLD2 expression was analysed by immunohistochemistry and western blotting. The effects of PLD2 inhibition on PCa cell viability and cell motility were measured using MTS, colony forming and wound-healing assays.

RESULTS

PLD2 protein is expressed about equally in luminal and basal prostate epithelial cells. In cells from different Gleason-scored PCa tissue PLD2 protein expression is generally higher than in non-tumorigenic cells and increases in PCa tissue scored Gleason 6-8. PLD2 protein is detected in the cytosol and nucleus and had a punctate appearance. In BPH tissue stromal cells as well as basal and luminal cells express PLD2. PLD2 protein co-expresses with chromogranin A in castrate-resistant PCa tissue. PLD2 inhibition reduces PCa cell viability, colony forming ability and directional cell movement.

CONCLUSIONS

PLD2 expression correlates with increasing Gleason score to GS8. PLD2 inhibition has the potential to reduce PCa progression.

Abi1 loss drives prostate tumorigenesis through activation of EMT and non-canonical WNT signaling

Background

Prostate cancer development involves various mechanisms, which are poorly understood but pointing to epithelial mesenchymal transition (EMT) as the key mechanism in progression to metastatic disease. ABI1, a member of WAVE complex and actin cytoskeleton regulator and adaptor protein, acts as tumor suppressor in prostate cancer but the role of ABI1 in EMT is not clear.

Methods

To investigate the molecular mechanism by which loss of ABI1 contributes to tumor progression, we disrupted the ABI1 gene in the benign prostate epithelial RWPE-1 cell line and determined its phenotype. Levels of ABI1 expression in prostate organoid tumor cell lines was evaluated by Western blotting and RNA sequencing. ABI1 expression and its association with prostate tumor grade was evaluated in a TMA cohort of 505 patients and metastatic cell lines.

Results

Low ABI1 expression is associated with biochemical recurrence, metastasis and death (p = 0.038). Moreover, ABI1 expression was significantly decreased in Gleason pattern 5 vs. pattern 4 (p = 0.0025) and 3 (p = 0.0012), indicating an association between low ABI1 expression and highly invasive prostate tumors. Disruption of ABI1 gene in RWPE-1 cell line resulted in gain of an invasive phenotype, which was characterized by a loss of cell-cell adhesion markers and increased migratory ability of RWPE-1 spheroids. Through RNA sequencing and protein expression analysis, we discovered that ABI1 loss leads to activation of non-canonical WNT signaling and EMT pathways, which are rescued by re-expression of ABI1. Furthermore, an increase in STAT3 phosphorylation upon ABI1 inactivation and the evidence of a high-affinity interaction between the FYN SH2 domain and ABI1 pY421 support a model in which ABI1 acts as a gatekeeper of non-canonical WNT-EMT pathway activation downstream of the FZD2 receptor.

Conclusions

ABI1 controls prostate tumor progression and epithelial plasticity through regulation of EMT-WNT pathway. Here we discovered that ABI1 inhibits EMT through suppressing FYN-STAT3 activation downstream from non-canonical WNT signaling thus providing a novel mechanism of prostate tumor suppression.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0410-y) contains supplementary material, which is available to authorized users.

Whole-Genome and Transcriptional Analysis of Treatment-Emergent Small-Cell Neuroendocrine Prostate Cancer Demonstrates Intraclass Heterogeneity

Therapeutic resistance in metastatic castration-resistant prostate cancer (mCRPC) can be accompanied by treatment-emergent small-cell neuroendocrine carcinoma (t-SCNC), a morphologically distinct subtype. We performed integrative whole-genome and -transcriptome analysis of mCRPC tumor biopsies including paired biopsies after progression, and multiple samples from the same individual. t-SCNC was significantly less likely to have amplification of AR or an intergenic AR-enhancer locus, and demonstrated lower expression of AR and its downstream transcriptional targets. Genomic and transcriptional hallmarks of t-SCNC included biallelic loss of RB1, elevated expression levels of CDKN2A and E2F1, and loss of expression of the AR and AR-responsive genes including TMPRSS2 and NKX3-1. We identified three tumors that converted from adenocarcinoma to t-SCNC and demonstrate spatial and temporal intrapatient heterogeneity of metastatic tumors harboring adenocarcinoma, t-SCNC, or mixed expression phenotypes, with implications for treatment strategies in which dual targeting of adenocarcinoma and t-SCNC phenotypes may be necessary. IMPLICATIONS: The t-SCNC phenotype is characterized by lack of AR enhancer gain and loss of RB1 function, and demonstrates both interindividual and intraindividual heterogeneity.Visual Overview: http://mcr.aacrjournals.org/content/molcanres/17/6/1235/F1.large.jpg.

RNA Splicing of the BHC80 Gene Contributes to Neuroendocrine Prostate Cancer Progression

BACKGROUND

Prostate adenocarcinoma (AdPC) progression to treatment-induced neuroendocrine prostate cancer (t-NEPC) is associated with poor patient survival. While AdPC and t-NEPC share similar genomes, they possess distinct transcriptomes, suggesting that RNA splicing and epigenetic mechanisms may regulate t-NEPC development.

OBJECTIVE

To characterize the role of alternative RNA splicing of the histone demethylase BHC80 during t-NEPC progression.

DESIGN, SETTING, AND PARTICIPANTS

The expression of BHC80 splice variants (BHC80-1 and BHC80-2) were compared between AdPC and t-NEPC patient tumors. Regulatory mechanisms of RNA splicing of the BHC80 gene were studied, and the signal pathways mediated by BHC80 splice variants were investigated in t-NEPC cell and xenograft models.

RESULTS

Global transcriptome analyses identified that the BHC80-2 variant is highly expressed in t-NEPC. Compared with the known histone demethylation activities of the BHC80 gene, we discovered a novel nonepigenetic action of BHC80-2, whereby BHC80-2 is localized in the cytoplasm to trigger the MyD88-p38-TTP pathway, which results in increased RNA stability of multiple tumor-promoting cytokines. While BHC80-2 does not induce neuroendocrine differentiation of cancer cells, it stimulates cell proliferation and tumor progression independent of androgen receptor signaling. Blockade of BHC80-2-regulated MyD88 signaling suppresses growth of several t-NEPC cell spheroid and xenograft models.

CONCLUSIONS

Gain of function of BHC80-2 through alternative RNA splicing activates immune responses of cancer cells to promote t-NEPC development.

PATIENT SUMMARY

The main obstacle to develop effective therapies for patients with t-NEPC is the lack of understanding on how t-NEPC is developed. Our study not only identifies a previously unknown BHC80-2-MyD88 signaling pathway that plays an important role during t-NEPC development, but also provides a proof of principle that targeting this signal pathway may offer an avenue to treat t-NEPC.

Clinical characteristics, treatment outcomes and potential novel therapeutic options for patients with neuroendocrine carcinoma of the prostate

Background

Neuroendocrine carcinomas of the prostate (NEPCs) are rare tumors with poor prognosis. While platinum and etoposide-based chemotherapy regimens (PE) are commonly applied in first-line for advanced disease, evidence for second-line therapy and beyond is very limited.

Methods

Retrospective analysis of all patients with NEPCs including mixed differentiation with adenocarcinoma component and well differentiated neuroendocrine tumors (NETs, carcinoids) at two high-volume oncological centers between 12/2000 and 11/2017.

Results

Of 46 identified patients 39.1 % had a prior diagnosis of prostatic adenocarcinoma only, 43.5 % had a mixed differentiation at NEPC diagnosis, 67.4 % developed visceral metastases, 10.9 % showed paraneoplastic syndromes. Overall survival (OS) from NEPC diagnosis was 15.5 months, and significantly shorter in patients with a prior prostatic adenocarcinoma (5.4 vs. 32.7 months, p=0.005). 34 patients received palliative first-line systemic therapy with a median progression-free survival (PFS) of 6.6 months, mostly PE. Overall response rate (ORR) for PE was 48.1 %. 19 patients received second-line therapy, mostly with poor responses. Active regimens were topotecan (1 PR, 3 PD), enzalutamide (1 SD), abiraterone (1 SD), FOLFIRI (1 SD), and ipilimumab+nivolumab (1 PR). One patient with prostatic carcinoid was sequentially treated with octreotide, peptide receptor radionuclide therapy and everolimus, and survived for over 9 years.

Conclusions

EP in first-line shows notable ORR, however limited PFS. For second-line therapy, topotecan, FOLFIRI, enzalutamide, abiraterone and immune checkpoint blockade are treatment options. Prostatic carcinoids can be treated in analogy to well differentiated gastrointestinal NETs.

Targeting androgen receptor-independent pathways in therapy-resistant prostate cancer

Since androgen receptor (AR) signaling is critically required for the development of prostate cancer (PCa), targeting AR axis has been the standard treatment of choice for advanced and metastatic PCa. Unfortunately, although the tumor initially responds to the therapy, treatment resistance eventually develops and the disease will progress. It is therefore imperative to identify the mechanisms of therapeutic resistance and novel molecular targets that are independent of AR signaling. Recent advances in pathology, molecular biology, genetics and genomics research have revealed novel AR-independent pathways that contribute to PCa carcinogenesis and progression. They include neuroendocrine differentiation, cell metabolism, DNA damage repair pathways and immune-mediated mechanisms. The development of novel agents targeting the non-AR mechanisms holds great promise to treat PCa that does not respond to AR-targeted therapies.

Evolving concepts in prostatic neuroendocrine manifestations: from focal divergent differentiation to amphicrine carcinoma

Prostatic neuroendocrine manifestations encompass a heterogeneous spectrum of morphologic entities. In the era of evidence-based and precision-led treatment, distinction of biologically relevant clinical manifestations expanded the evolving clinical role of pathologists. Recent observations on the occurrence of hormone therapy-induced aggressive prostatic cancers with neuroendocrine features have triggered the need to refine the spectrum and nomenclature of prostatic neuroendocrine manifestations. Although the morphologic assessment still remains the basis of the diagnostic workup of prostatic neoplasms, the application of ancillary biomarkers is crucial in the accurate classification of such presentations. This review provides a diagnostic roadmap for the practicing pathologist by reviewing the characteristic morphologic, immunohistochemical, and molecular correlates of various faces of prostatic neuroendocrine manifestations.

Neuroendocrine differentiation of prostate cancer leads to PSMA suppression

Prostate-specific membrane antigen (PSMA) is overexpressed in most prostate adenocarcinoma (AdPC) cells and acts as a target for molecular imaging. However, some case reports indicate that PSMA-targeted imaging could be ineffectual for delineation of neuroendocrine (NE) prostate cancer (NEPC) lesions due to the suppression of the PSMA gene (FOLH1). These same reports suggest that targeting somatostatin receptor type 2 (SSTR2) could be an alternative diagnostic target for NEPC patients. This study evaluates the correlation between expression of FOLH1, NEPC marker genes and SSTR2. We evaluated the transcript abundance for FOLH1 and SSTR2 genes as well as NE markers across 909 tumors. A significant suppression of FOLH1 in NEPC patient samples and AdPC samples with high expression of NE marker genes was observed. We also investigated protein alterations of PSMA and SSTR2 in an NE-induced cell line derived by hormone depletion and lineage plasticity by loss of p53. PSMA is suppressed following NE induction and cellular plasticity in p53-deficient NEPC model. The PSMA-suppressed cells have more colony formation ability and resistance to enzalutamide treatment. Conversely, SSTR2 was only elevated following hormone depletion. In 18 NEPC patient-derived xenograft (PDX) models we find a significant suppression of FOLH1 and amplification of SSTR2 expression. Due to the observed FOLH1-supressed signature of NEPC, this study cautions on the reliability of using PMSA as a target for molecular imaging of NEPC. The observed elevation of SSTR2 in NEPC supports the possible ability of SSTR2-targeted imaging for follow-up imaging of low PSMA patients and monitoring for NEPC development.

Selective Actionable and Druggable Protein Kinases Drive the Progression of Neuroendocrine Prostate Cancer

Current clinical anti-androgen therapies in advanced prostate cancer (PCa) are driving an increased incidence of neuroendocrine prostate cancer (NEPC), a histological variant exhibiting reduced androgen receptor levels and expression of neuroendocrine markers. The mechanisms underlying the development of NEPC are poorly understood. A set of available data from a well-validated xenograft model of NEPC was used to analyze the exact role of protein kinase (PK) played in the development of NEPC. Fifty-four actionable and druggable PKs, mainly enriched in PI3K-Akt, mTOR, and MAPK signaling pathways, were screened out from the drastically changed PKs during NEPC transdifferentiation. Further analysis based on the crosstalk of these above signaling pathways finally singled out 10 PKs considered drivers and therapeutic targets in the development and treatment of NEPC. In vitro, the variation trend of PK expression observed during NEPC transdifferentiation could be recapitulated in PCa cell lines with different malignant degree. The predicted kinase targets exhibited different sensibilities in the restriction of PC3 cell growth. Selective actionable and druggable PKs may act as drivers in the progression of NEPC, and most of them can be used as potential therapeutic targets in clinical practice.