PARP Inhibition Suppresses GR-MYCN-CDK5-RB1-E2F1 Signaling and Neuroendocrine Differentiation in Castration-Resistant Prostate Cancer

Glucocorticoid receptor action in prostate cancer: the role of transcription factor crosstalk

Prostate cancer is one of the most prevalent malignancies and is primarily driven by aberrant androgen receptor (AR) signaling. While AR-targeted therapies form the cornerstone of prostate cancer treatment, they often inadvertently activate compensatory pathways, leading to therapy resistance. This resistance is frequently mediated through changes in transcription factor (TF) crosstalk, reshaping gene regulatory programs and ultimately weakening treatment efficacy. Consequently, investigating TF interactions has become crucial for understanding the mechanisms driving therapy-resistant cancers. Recent evidence has highlighted the crosstalk between the glucocorticoid receptor (GR) and AR, demonstrating that GR can induce prostate cancer therapy resistance by replacing the inactivated AR, thereby becoming a driver of the disease. In addition to this oncogenic role, GR has also been shown to act as a tumor suppressor in prostate cancer. Owing to this dual role and the widespread use of glucocorticoids as adjuvant therapy, it is essential to understand GR's actions across different stages of prostate cancer development. In this review, we explore the current knowledge of GR in prostate cancer, with a specific focus on its crosstalk with other TFs. GR can directly and indirectly interact with a variety of TFs, and these interactions vary significantly depending on the type of prostate cancer cells. By highlighting these crosstalk interactions, we aim to provide insights that can guide the research and development of new GR-targeted therapies to mitigate its harmful effects in prostate cancer.

A miR-361-5p/ ORC6/ PLK1 axis regulates prostate cancer progression

Prostate cancer (PCa) is the most prevalent malignant tumor of the genitourinary system, and metastatic disease has a significant impact on the prognosis of PCa patients. As a result, knowing the processes of PCa development can help patients achieve better outcomes. Here, we investigated the expression and function of ORC6 in PCa. Our findings indicated that ORC6 was elevated in advanced PCa tissues. Patients with PCa who exhibited high levels of ORC6 had a poor prognosis. Following that, we investigated the function of ORC6 in PCa progression using a variety of functional experiments both in vivo and in vitro, and discovered that ORC6 knockdown inhibited PCa cell proliferation, growth, and migration. Furthermore, RNA-seq was employed to examine the molecular mechanism of PCa progression. The results revealed that ORC6 might promote the expression of PLK1, a serine/threonine kinase in PCa cells. We also discovered that ORC6 as a novel miR-361-5p substrate using database analysis, and miR-361-5p was found to lower ORC6 expression. Additionally, RNA immunoprecipitation (RIP) and luciferase reporter tests revealed that the transcription factor E2F1 could regulate ORC6 expression in PCa cells. PLK1 overexpression or miR-361-5p inhibitor treatment effectively removed the inhibitory effects caused by ORC6 silencing. Notably, our data showed that therapeutically targeting the miR-361-5p/ORC6/PLK1 axis may be a viable therapy option for PCa.

Binding of interleukin-1 receptor antagonist to cholinergic receptor muscarinic 4 promotes immunosuppression and neuroendocrine differentiation in prostate cancer

The tumor microenvironment (TME) of prostate cancer (PCa) is characterized by high levels of immunosuppressive molecules, including cytokines and chemokines. This creates a hostile immune landscape that impedes effective immune responses. The interleukin-1 (IL-1) receptor antagonist (IL1RN), a key anti-inflammatory molecule, plays a significant role in suppressing IL-1-related immune and inflammatory responses. Our research investigates the oncogenic role of IL1RN in PCa, particularly its interactions with muscarinic acetylcholine receptor 4 (CHRM4), and its involvement in driving immunosuppressive pathways and M2-like macrophage polarization within the PCa TME. We demonstrate that following androgen deprivation therapy (ADT), the IL1RN-CHRM4 interaction in PCa activates the MAPK/AKT signaling pathway. This activation upregulates the transcription factors E2F1 and MYCN, stimulating IL1RN production and creating a positive feedback loop that increases CHRM4 abundance in both PCa cells and M2-like macrophages. This ADT-driven IL1RN/CHRM4 axis significantly enhances immune checkpoint markers associated with neuroendocrine differentiation and treatment-resistant outcomes. Higher serum IL1RN levels are associated with increased disease aggressiveness and M2-like macrophage markers in advanced PCa patients. Additionally, elevated IL1RN levels correlate with better clinical outcomes following immunotherapy. Clinical correlations between IL1RN and CHRM4 expression in advanced PCa patients and neuroendocrine PCa organoid models highlight their potential as therapeutic targets. Our data suggest that targeting the IL1RN/CHRM4 signaling could be a promising strategy for managing PCa progression and enhancing treatment responses.

A phase II trial of apalutamide for intermediate-risk prostate cancer and molecular correlates

OBJECTIVES

To determine whether 6 months of preoperative apalutamide for intermediate-risk prostate cancer (IRPCa) reduces the aggregate postoperative radiotherapy risk and to evaluate associations of molecular perturbations with clinical outcomes in this study cohort.

PATIENTS AND METHODS

Between May 2018 and February 2020, eligible patients with IRPCa (Gleason 3 + 4 or 4 + 3 and clinical T2b-c or prostate-specific antigen level of 10-20 ng/mL) were treated with apalutamide 240 mg/day for 6 months followed by radical prostatectomy (RP) in this single-arm, phase II trial. The primary endpoint was presence of any adverse pathological feature at risk of pelvic radiation (pathological T stage after neoadjuvant therapy [yp]T3 or ypN1 or positive surgical margins). Translational studies, including germline and somatic DNA alterations and RNA and protein expression, were performed on post-apalutamide RP specimens, and assessed for associations with clinical outcomes.

RESULTS

A total of 40 patients underwent a RP, and only one patient discontinued apalutamide prior to 6 months. In all, 40% had adverse pathological features at time of RP, and the 3-year biochemical recurrence (BCR) rate was 15%, with 27.5% being not evaluable. Genomic alterations frequently seen in metastatic PCas, such as androgen receptor (AR), tumour protein p53 (TP53), phosphatase and tensin homologue (PTEN), or BReast CAncer associated gene (BRCA1/2) were underrepresented in this localised cohort. Adverse pathological features and BCR at 3-years were associated with increased expression of select cell cycle (e.g., E2F targets: adjusted P value [Padj] < 0.001, normalised enrichment score [NES] 2.47) and oxidative phosphorylation (Padj < 0.001, NES 1.62) pathways.

CONCLUSIONS

Preoperative apalutamide did not reduce the aggregate postoperative radiation risk to the pre-specified threshold in unselected men with IRPCa. However, transcriptomic analysis identified key dysregulated pathways in tumours associated with adverse pathological outcomes and BCR, which warrant future study. Further investigation of preoperative therapy is underway for men with high-risk PCa.

Integrative Molecular Analyses of the MD Anderson Prostate Cancer Patient-derived Xenograft (MDA PCa PDX) Series

PURPOSE

Develop and deploy a robust discovery platform that encompasses heterogeneity, clinical annotation, and molecular characterization and overcomes the limited availability of prostate cancer models. This initiative builds on the rich MD Anderson (MDA) prostate cancer (PCa) patient-derived xenograft (PDX) resource to complement existing publicly available databases by addressing gaps in clinically annotated models reflecting the heterogeneity of potentially lethal and lethal prostate cancer.

EXPERIMENTAL DESIGN

We performed whole-genome, targeted, and RNA sequencing in representative samples of the same tumor from 44 PDXs derived from 38 patients linked to donor tumor metadata and corresponding organoids. The cohort includes models derived from different morphologic groups, disease states, and involved organ sites (including circulating tumor cells), as well as paired samples representing heterogeneity or stages before and after therapy.

RESULTS

The cohort recapitulates clinically reported alterations in prostate cancer genes, providing a data resource for clinical and molecular interrogation of suitable experimental models. Paired samples displayed conserved molecular alteration profiles, suggesting the relevance of other regulatory mechanisms (e.g., epigenomic) influenced by the microenvironment and/or treatment. Transcriptomically, models were grouped on the basis of morphologic classification. DNA damage response-associated mechanisms emerged as differentially regulated between adenocarcinoma and neuroendocrine prostate cancer in a cross-interrogation of PDX/patient datasets.

CONCLUSIONS

We addressed the gap in clinically relevant prostate cancer models through comprehensive molecular characterization of MDA PCa PDXs, providing a discovery platform that integrates with patient data and benchmarked to therapeutically relevant consensus clinical groupings. This unique resource supports robust hypothesis generation and testing from basic, translational, and clinical perspectives.

PARP-ish: Gaps in Molecular Understanding and Clinical Trials Targeting PARP Exacerbate Racial Disparities in Prostate Cancer

PARP is a nuclear enzyme with a major function in the DNA damage response. PARP inhibitors (PARPi) have been developed for treating tumors harboring homologous recombination repair (HRR) defects that lead to a dependency on PARP. There are currently three PARPi approved for use in advanced prostate cancer (PCa), and several others are in clinical trials for this disease. Recent clinical trial results have reported differential efficacy based on the specific PARPi utilized as well as patient race. There is a racial disparity in PCa, where African American (AA) males are twice as likely to develop and die from the disease compared to European American (EA) males. Despite the disparity, there continues to be a lack of diversity in clinical trial cohorts for PCa. In this review, PARP nuclear functions, inhibition, and clinical relevance are explored through the lens of racial differences. This review will touch on the biological variations that have been explored thus far between AA and EA males with PCa to offer rationale for investigating PARPi response in the context of race at both the basic science and the clinical development levels.

Regulation of Molecular Biomarkers Associated with the Progression of Prostate Cancer

Androgen receptor signaling regulates the normal and pathological growth of the prostate. In particular, the growth and survival of prostate cancer cells is initially dependent on androgen receptor signaling. Exposure to androgen deprivation therapy leads to the development of castration-resistant prostate cancer. There is a multitude of molecular and cellular changes that occur in prostate tumor cells, including the expression of neuroendocrine features and various biomarkers, which promotes the switch of cancer cells to androgen-independent growth. These biomarkers include transcription factors (TP53, REST, BRN2, INSM1, c-Myc), signaling molecules (PTEN, Aurora kinases, retinoblastoma tumor suppressor, calcium-binding proteins), and receptors (glucocorticoid, androgen receptor-variant 7), among others. It is believed that genetic modifications, therapeutic treatments, and changes in the tumor microenvironment are contributing factors to the progression of prostate cancers with significant heterogeneity in their phenotypic characteristics. However, it is not well understood how these phenotypic characteristics and molecular modifications arise under specific treatment conditions. In this work, we summarize some of the most important molecular changes associated with the progression of prostate cancers and we describe some of the factors involved in these cellular processes.

Structural insights into the ubiquitylation strategy of the oligomeric CRL2FEM1B E3 ubiquitin ligase

Cullin-RING E3 ubiquitin ligase (CRL) family members play critical roles in numerous biological processes and diseases including cancer and Alzheimer's disease. Oligomerization of CRLs has been reported to be crucial for the regulation of their activities. However, the structural basis for its regulation and mechanism of its oligomerization are not fully known. Here, we present cryo-EM structures of oligomeric CRL2FEM1B in its unneddylated state, neddylated state in complex with BEX2 as well as neddylated state in complex with FNIP1/FLCN. These structures reveal that asymmetric dimerization of N8-CRL2FEM1B is critical for the ubiquitylation of BEX2 while FNIP1/FLCN is ubiquitylated by monomeric CRL2FEM1B. Our data present an example of the asymmetric homo-dimerization of CRL. Taken together, this study sheds light on the ubiquitylation strategy of oligomeric CRL2FEM1B according to substrates with different scales.

Blocking the E2F transcription factor 1/high-mobility group box 2 pathway enhances the intervention effects of α-santalol on the malignant behaviors of liver cancer cells

In view of the tumor-inhibiting effect of α-santalol in various cancers and the role of E2F transcription factor 1 (E2F1) as an important target for anticancer research, this study investigates the relation between α-santalol and E2F1, as well as the effect of α-santalol on liver cancer progression and the corresponding mechanism. Concretely, liver cancer cells were treated with different concentrations of α-santalol. The IC50 value of α-santalol was determined using Probit regression analysis. Then, transcription factors that are targeted by α-santalol and differentially expressed in liver cancer were screened out. The clinicopathological impact of E2F1 and its targets were evaluated and predicted. The expressions of E2F1 and high-mobility group box 2 (HMGB2) and their correlation in the liver cancer tissues were analyzed by bioinformatics. The effects of E2F1 and HMGB2 on the biological characteristics of liver cancer cells were examined through loss/gain-of-function and molecular assays. With the extension of treatment time, the inhibitory effects of 10 μmol/L and 20 μmol/L α-santalol on cancer cell survival rate were enhanced (P < 0.001). E2F1 and HMGB2 were highly expressed and positively correlated in liver cancer tissues (P < 0.05). High E2F1 expression was correlated with large tumors and high TNM stages (P < 0.05). E2F1 knockdown promoted the effects of α-santalol on dose-dependently inhibiting viability, colony formation, invasion and migration (P < 0.05). Moreover, E2F1 knockdown reduced the IC50 value and HMGB2 level, while HMGB2 overexpression produced opposite effects. HMGB2 overexpression and E2F1 knockdown mutually counteracted their effects on the IC50 value and on the viability and apoptosis of α-santalol-treated liver cancer cells (P < 0.01). Collectively, blocking the E2F1/HMGB2 pathway enhances the intervention effects of α-santalol on the proliferation, migration and invasion of liver cancer cells.

UCHL1 is a potential molecular indicator and therapeutic target for neuroendocrine carcinomas

Neuroendocrine carcinomas, such as neuroendocrine prostate cancer and small-cell lung cancer, commonly have a poor prognosis and limited therapeutic options. We report that ubiquitin carboxy-terminal hydrolase L1 (UCHL1), a deubiquitinating enzyme, is elevated in tissues and plasma from patients with neuroendocrine carcinomas. Loss of UCHL1 decreases tumor growth and inhibits metastasis of these malignancies. UCHL1 maintains neuroendocrine differentiation and promotes cancer progression by regulating nucleoporin, POM121, and p53. UCHL1 binds, deubiquitinates, and stabilizes POM121 to regulate POM121-associated nuclear transport of E2F1 and c-MYC. Treatment with the UCHL1 inhibitor LDN-57444 slows tumor growth and metastasis across neuroendocrine carcinomas. The combination of UCHL1 inhibitors with cisplatin, the standard of care used for neuroendocrine carcinomas, significantly delays tumor growth in pre-clinical settings. Our study reveals mechanisms of UCHL1 function in regulating the progression of neuroendocrine carcinomas and identifies UCHL1 as a therapeutic target and potential molecular indicator for diagnosing and monitoring treatment responses in these malignancies.

Prostate Cancer Liver Metastasis: An Ominous Metastatic Site in Need of Distinct Management Strategies

Prostate cancer liver metastasis (PCLM), seen in upwards of 25% of metastatic castration-resistant PC (mCRPC) patients, is the most lethal site of mCRPC with a median overall survival of 10-14 months. Despite its ominous prognosis and anticipated rise in incidence due to longer survival with contemporary therapy, PCLM is understudied. This review aims to summarize the existing literature regarding the risk factors associated with the development of PCLM, and to identify areas warranting further research. A literature search was conducted through Ovid MEDLINE from 2000 to March 2023. Relevant subject headings and text words were used to capture the following concepts: "Prostatic Neoplasms", "Liver Neoplasms", and "Neoplasm Metastasis". Citation searching identified additional manuscripts. Forty-one studies were retained for detailed analysis. The clinical risk factors for visceral/liver metastasis included <70 years, ≥T3 tumor, N1 nodal stage, de novo metastasis, PSA >20 ng/mL, and a Gleason score >8. Additional risk factors comprised elevated serum AST, LDH or ALP, decreased Hb, genetic markers like RB1 and PTEN loss, PIK3CB and MYC amplification, as well as numerous PC treatments either acting directly or indirectly through inducing liver injury. Further research regarding predictive factors, early detection strategies, and targeted therapies for PCLM are critical for improving patient outcomes.

Personalized medicine for metastatic prostate cancer: The paradigm of PARP inhibitors

Despite remarkable progress in the last decade, metastatic prostate cancer (mPCa) remains incurable. The approval of PARP inhibitors (PARPis) represents a milestone in this field, which definitively enters the era of precision medicine, as mPCa is often enriched for defects of homologous recombination repair genes. PARPis are now used as single agents for patients with metastatic castration-resistant PCa. Moreover, combinations of PARPis plus androgen-receptor targeted agents and immune checkpoint inhibitors, and earlier applications of PARPis in the metastatic hormone-sensitive PCa are under evaluation, representing the possible upcoming applications of these agents. Mechanisms of sensitization and resistance have been only partially elucidated. In our review, we summarize the current clinical evidence regarding PARPis in mPCa and the future directions of these targeted agents.

CDK5: an oncogene or an anti-oncogene: location location location

Recent studies have uncovered various physiological functions of CDK5 in many nonneuronal tissues. Upregulation of CDK5 and/or its activator p35 in neurons promotes healthy neuronal functions, but their overexpression in nonneuronal tissues is causally linked to cancer of many origins. This review focuses on the molecular mechanisms by which CDK5 recruits diverse tissue-specific substrates to elicit distinct phenotypes in sixteen different human cancers. The emerging theme suggests that CDK5's role as an oncogene or anti-oncogene depends upon its subcellular localization. CDK5 mostly acts as an oncogene, but in gastric cancer, it is a tumor suppressor due to its unique nuclear localization. This indicates that CDK5's access to certain nuclear substrates converts it into an anti-oncogenic kinase. While acting as a bonafide oncogene, CDK5 also activates a few cancer-suppressive pathways in some cancers, presumably due to the mislocalization of nuclear substrates in the cytoplasm. Therefore, directing CDK5 to the nucleus or exporting tumor-suppressive nuclear substrates to the cytoplasm may be promising approaches to combat CDK5-induced oncogenicity, analogous to neurotoxicity triggered by nuclear CDK5. Furthermore, while p35 overexpression is oncogenic, hyperactivation of CDK5 by inducing p25 formation results in apoptosis, which could be exploited to selectively kill cancer cells by dialing up CDK5 activity, instead of inhibiting it. CDK5 thus acts as a molecular rheostat, with different activity levels eliciting distinct functional outcomes. Finally, as CDK5's role is defined by its substrates, targeting them individually or in conjunction with CDK5 should create potentially valuable new clinical opportunities.

SPOP Mutations Target STING1 Signaling in Prostate Cancer and Create Therapeutic Vulnerabilities to PARP Inhibitor-Induced Growth Suppression

PURPOSE

Speckle-type POZ protein (SPOP) is important in DNA damage response (DDR) and maintenance of genomic stability. Somatic heterozygous missense mutations in the SPOP substrate-binding cleft are found in up to 15% of prostate cancers. While mutations in SPOP predict for benefit from androgen receptor signaling inhibition (ARSi) therapy, outcomes for patients with SPOP-mutant (SPOPmut) prostate cancer are heterogeneous and targeted treatments for SPOPmut castrate-resistant prostate cancer (CRPC) are lacking.

EXPERIMENTAL DESIGN

Using in silico genomic and transcriptomic tumor data, proteomics analysis, and genetically modified cell line models, we demonstrate mechanistic links between SPOP mutations, STING signaling alterations, and PARP inhibitor vulnerabilities.

RESULTS

We demonstrate that SPOP mutations are associated with upregulation of a 29-gene noncanonical (NC) STING (NC-STING) signature in a subset of SPOPmut, treatment-refractory CRPC patients. We show in preclinical CRPC models that SPOP targets and destabilizes STING1 protein, and prostate cancer-associated SPOP mutations result in upregulated NC-STING-NF-κB signaling and macrophage- and tumor microenvironment (TME)-facilitated reprogramming, leading to tumor cell growth. Importantly, we provide in vitro and in vivo mechanism-based evidence that PARP inhibitor (PARPi) treatment results in a shift from immunosuppressive NC-STING-NF-κB signaling to antitumor, canonical cGAS-STING-IFNβ signaling in SPOPmut CRPC and results in enhanced tumor growth inhibition.

CONCLUSIONS

We provide evidence that SPOP is critical in regulating immunosuppressive versus antitumor activity downstream of DNA damage-induced STING1 activation in prostate cancer. PARPi treatment of SPOPmut CRPC alters this NC-STING signaling toward canonical, antitumor cGAS-STING-IFNβ signaling, highlighting a novel biomarker-informed treatment strategy for prostate cancer.

Overexpression of RACGAP1 by E2F1 Promotes Neuroendocrine Differentiation of Prostate Cancer by Stabilizing EZH2 Expression

Neuroendocrine prostate cancer (NEPC) is a lethal subtype of prostate cancer. It is characterized by the loss of androgen receptor (AR) signaling in neuroendocrine transdifferentiation, and finally, resistance to AR-targeted therapy. With the application of a new generation of potent AR inhibitors, the incidence of NEPC is gradually increasing. The molecular mechanism of neuroendocrine differentiation (NED) after androgen deprivation therapy (ADT) remains largely unclear. In this study, using NEPC-related genome sequencing database analyses, we screened RACGAP1, a common differentially expressed gene. We investigated RACGAP1 expression in clinical prostate cancer specimens by IHC. Regulated pathways were examined by Western blotting, qRT-PCR, luciferase reporter, chromatin immunoprecipitation, and immunoprecipitation assays. The corresponding function of RACGAP1 in prostate cancer was analyzed by CCK-8 and Transwell assays. The changes of neuroendocrine markers and AR expression in C4-2-R and C4-2B-R cells were detected in vitro. We confirmed that RACGAP1 contributed to NE transdifferentiation of prostate cancer. Patients with high tumor RACGAP1 expression had shorter relapse-free survival time. The expression of RACGAP1 was induced by E2F1. RACGAP1 promoted neuroendocrine transdifferentiation of prostate cancer by stabilizing EZH2 expression in the ubiquitin-proteasome pathway. Moreover, overexpression of RACGAP1 promoted enzalutamide resistance of castration-resistant prostate cancer (CRPC) cells. Our results showed that the upregulation of RACGAP1 by E2F1 increased EZH2 expression, which drove NEPC progression. This study explored the molecular mechanism of NED and may provide novel methods and ideas for targeted therapy of NEPC.

Characterization and therapeutic perspectives of differentiation-inducing therapy in malignant tumors

Cancer is a major public health issue globally and is one of the leading causes of death. Although available treatments improve the survival rate of some cases, many advanced tumors are insensitive to these treatments. Cancer cell differentiation reverts the malignant phenotype to its original state and may even induce differentiation into cell types found in other tissues. Leveraging differentiation-inducing therapy in high-grade tumor masses offers a less aggressive strategy to curb tumor progression and heightens chemotherapy sensitivity. Differentiation-inducing therapy has been demonstrated to be effective in a variety of tumor cells. For example, differentiation therapy has become the first choice for acute promyelocytic leukemia, with the cure rate of more than 90%. Although an appealing concept, the mechanism and clinical drugs used in differentiation therapy are still in their nascent stage, warranting further investigation. In this review, we examine the current differentiation-inducing therapeutic approach and discuss the clinical applications as well as the underlying biological basis of differentiation-inducing agents.

Targeting Key Players of Neuroendocrine Differentiation in Prostate Cancer

Neuroendocrine prostate cancer (NEPC) is a highly aggressive subtype of prostate cancer (PC) that commonly emerges through a transdifferentiation process from prostate adenocarcinoma and evades conventional therapies. Extensive molecular research has revealed factors that drive lineage plasticity, uncovering novel therapeutic targets to be explored. A diverse array of targeting agents is currently under evaluation in pre-clinical and clinical studies with promising results in suppressing or reversing the neuroendocrine phenotype and inhibiting tumor growth and metastasis. This new knowledge has the potential to contribute to the development of novel therapeutic approaches that may enhance the clinical management and prognosis of this lethal disease. In the present review, we discuss molecular players involved in the neuroendocrine phenotype, and we explore therapeutic strategies that are currently under investigation for NEPC.

Sustained delivery of PARP inhibitor Talazoparib for the treatment of BRCA-deficient ovarian cancer

Background

Ovarian cancer has long been known to be the deadliest cancer associated with the female reproductive system. More than 15% of ovarian cancer patients have a defective BRCA-mediated homologous recombination repair pathway that can be therapeutically targeted with PARP inhibitors (PARPi), such as Talazoparib (TLZ). The expansion of TLZ clinical approval beyond breast cancer has been hindered due to the highly potent systemic side effects resembling chemotherapeutics. Here we report the development of a novel TLZ-loaded PLGA implant (InCeT-TLZ) that sustainedly releases TLZ directly into the peritoneal (i.p.) cavity to treat patient-mimicking BRCA-mutated metastatic ovarian cancer (mOC).

Methods

InCeT-TLZ was fabricated by dissolving TLZ and PLGA in chloroform, followed by extrusion and evaporation. Drug loading and release were confirmed by HPLC. The in vivo therapeutic efficacy of InCeT-TLZ was carried out in a murine Brca2^-/-p53^R172H/-Pten^-/- genetically engineered peritoneally mOC model. Mice with tumors were divided into four groups: PBS i.p. injection, empty implant i.p. implantation, TLZ i.p. injection, and InCeT-TLZ i.p. implantation. Body weight was recorded three times weekly as an indicator of treatment tolerance and efficacy. Mice were sacrificed when the body weight increased by 50% of the initial weight.

Results

Biodegradable InCeT-TLZ administered intraperitoneally releases 66 μg of TLZ over 25 days. In vivo experimentation shows doubled survival in the InCeT-TLZ treated group compared to control, and no significant signs of toxicity were visible histologically in the surrounding peritoneal organs, indicating that the sustained and local delivery of TLZ greatly maximized therapeutic efficacy and minimized severe clinical side effects. The treated animals eventually developed resistance to PARPi therapy and were sacrificed. To explore treatments to overcome resistance, in vitro studies with TLZ sensitive and resistant ascites-derived murine cell lines were carried out and demonstrated that ATR inhibitor and PI3K inhibitor could be used in combination with the InCeT-TLZ to overcome acquired PARPi resistance.

Conclusion

Compared to intraperitoneal PARPi injection, the InCeT-TLZ better inhibits tumor growth, delays the ascites formation, and prolongs the overall survival of treated mice, which could be a promising therapy option that benefits thousands of women diagnosed with ovarian cancer.

Patient-Derived Tumor Organoids Can Predict the Progression-Free Survival of Patients With Stage IV Colorectal Cancer After Surgery

BACKGROUND

Recent studies have shown patient-derived tumor organoids can predict the drug response of patients with cancer. However, the prognostic value of patient-derived tumor organoid-based drug tests in predicting the progression-free survival of patients with stage IV colorectal cancer after surgery remains unknown.

OBJECTIVE

This study aimed to explore the prognostic value of patient-derived tumor organoid-based drug tests in patients with stage IV colorectal cancer after surgery.

DESIGN

Retrospective cohort study.

SETTINGS

Surgical samples were obtained from patients with stage IV colorectal cancer at the Nanfang Hospital.

PATIENTS

A total of 108 patients who underwent surgery with successful patient-derived tumor organoid culture and drug testing were recruited between June 2018 and June 2019.

INTERVENTIONS

Patient-derived tumor organoid culture and chemotherapeutic drug testing.

MAIN OUTCOMES MEASURES

Progression-free survival.

RESULTS

According to the patient-derived tumor organoid-based drug test, 38 patients were drug sensitive and 76 patients were drug resistant. The median progression-free survival was 16.0 months in the drug-sensitive group and 9.0 months in the drug resistant group ( p < 0.001). Multivariate analyses showed that drug resistance (HR, 3.38; 95% CI, 1.84-6.21; p < 0.001), right-sided colon (HR, 3.50; 95% CI, 1.71-7.15; p < 0.001), mucinous adenocarcinoma (HR, 2.47; 95% CI, 1.34-4.55; p = 0.004), and non-R0 resection (HR, 2.70; 95% CI, 1.61-4.54; p < 0.001) were independent predictors of progression-free survival. The new patient-derived tumor organoid-based drug test model, which includes the patient-derived tumor organoid-based drug test, primary tumor location, histological type, and R0 resection, was more accurate than the traditional clinicopathological model in predicting progression-free survival ( p = 0.001).

LIMITATIONS

A single-center cohort study.

CONCLUSIONS

Patient-derived tumor organoids can predict progression-free survival in patients with stage IV colorectal cancer after surgery. Patient-derived tumor organoid drug resistance is associated with shorter progression-free survival, and the addition of patient-derived tumor organoid drug tests to existing clinicopathological models improves the ability to predict progression-free survival.

Development and validation of a tumor immune cell infiltration-related gene signature for recurrence prediction by weighted gene co-expression network analysis in prostate cancer

Introduction: Prostate cancer (PCa) is the second most common malignancy in men. Despite multidisciplinary treatments, patients with PCa continue to experience poor prognoses and high rates of tumor recurrence. Recent studies have shown that tumor-infiltrating immune cells (TIICs) are associated with PCa tumorigenesis.

Methods: The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets were used to derive multi-omics data for prostate adenocarcinoma (PRAD) samples. The CIBERSORT algorithm was used to calculate the landscape of TIICs. Weighted gene co-expression network analysis (WGCNA) was performed to determine the candidate module most significantly associated with TIICs. LASSO Cox regression was applied to screen a minimal set of genes and construct a TIIC-related prognostic gene signature for PCa. Then, 78 PCa samples with CIBERSORT output p-values of less than 0.05 were selected for analysis. WGCNA identified 13 modules, and the MEblue module with the most significant enrichment result was selected. A total of 1143 candidate genes were cross-examined between the MEblue module and active dendritic cell-related genes.

Results: According to LASSO Cox regression analysis, a risk model was constructed with six genes (STX4, UBE2S, EMC6, EMD, NUCB1 and GCAT), which exhibited strong correlations with clinicopathological variables, tumor microenvironment context, antitumor therapies, and tumor mutation burden (TMB) in TCGA-PRAD. Further validation showed that the UBE2S had the highest expression level among the six genes in five different PCa cell lines.

Discussion: In conclusion, our risk-score model contributes to better predicting PCa patient prognosis and understanding the underlying mechanisms of immune responses and antitumor therapies in PCa.

Gankyrin-mediated interaction between cancer cells and tumor-associated macrophages facilitates prostate cancer progression and androgen deprivation therapy resistance

Increasing evidence reveals that the interaction between tumor cells and tumor-associated macrophages (TAMs) facilitates the progression of prostate cancer, but the related mechanisms remained unclear. This study determined how gankyrin, a component of the 19S regulatory complex of the 26S proteasome, regulates the progression and androgen deprivation therapy (ADT) resistance of prostate cancer through tumor cell-TAM interactions. In vitro functional experiments and in vivo subcutaneous tumor models were used to explore the biological role and molecular mechanisms of gankyrin in prostate cancer cell-TAM interactions. 234 prostate cancer patients were randomly divided into training and validation cohorts to examine the prognostic value of gankyrin through immunohistochemistry (IHC) and statistical analyses, and high gankyrin expression was correlated with poor prognosis. In addition, gankyrin facilitated the progression and ADT resistance of prostate cancer. Mechanistically, gankyrin recruited and upregulated non-POU-domain-containing octamer-binding protein (NONO) expression, resulting in increased androgen receptor (AR) expression. AR then bound to the high-mobility group box 1 (HMGB1) promoter to trigger HMGB1 transcription, expression, and secretion. Moreover, HMGB1 was found to promote the recruitment and activation of TAMs, which secrete IL-6 to reciprocally promote prostate cancer progression, ADT resistance and gankyrin expression via STAT3, resulting in formation of a gankyrin/NONO/AR/HMGB1/IL-6/STAT3 positive feedback loop. Furthermore, targeting the interaction between tumor cells and TAMs by blocking this loop inhibited ADT resistance in a tumor xenograft model. Taken together, the data show that gankyrin serves as a reliable prognostic indicator and therapeutic target for prostate cancer patients.

Role of transcription factors and chromatin modifiers in driving lineage reprogramming in treatment-induced neuroendocrine prostate cancer

Therapy-induced neuroendocrine prostate cancer (NEPC) is a highly lethal variant of prostate cancer that is increasing in incidence with the increased use of next-generation of androgen receptor (AR) pathway inhibitors. It arises via a reversible trans-differentiation process, referred to as neuroendocrine differentiation (NED), wherein prostate cancer cells show decreased expression of AR and increased expression of neuroendocrine (NE) lineage markers including enolase 2 (ENO2), chromogranin A (CHGA) and synaptophysin (SYP). NEPC is associated with poor survival rates as these tumors are aggressive and often metastasize to soft tissues such as liver, lung and central nervous system despite low serum PSA levels relative to disease burden. It has been recognized that therapy-induced NED involves a series of genetic and epigenetic alterations that act in a highly concerted manner in orchestrating lineage switching. In the recent years, we have seen a spurt in research in this area that has implicated a host of transcription factors and epigenetic modifiers that play a role in driving this lineage switching. In this article, we review the role of important transcription factors and chromatin modifiers that are instrumental in lineage reprogramming of prostate adenocarcinomas to NEPC under the selective pressure of various AR-targeted therapies. With an increased understanding of the temporal and spatial interplay of transcription factors and chromatin modifiers and their associated gene expression programs in NEPC, better therapeutic strategies are being tested for targeting NEPC effectively.

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.

Is the glucocorticoid receptor a key player in prostate cancer?: A literature review

Glucocorticoids act through the glucocorticoid receptor (GR) and exert pleiotropic effects in different cancer types. In prostate cancer cells, GR and androgen receptor (AR) share overlapping transcriptomes and cistromes. Under enzalutamide treatment, GR signaling can bypass AR activation and promote castration resistance via the expression of a subset of AR-target genes. However, GR-dependent growth under enhanced antiandrogen inhibition occurs only in a subset of primed cells. On the other hand, glucocorticoids have been used successfully in the treatment of prostate cancer for many years. In the context of AR signaling, GR competes with AR for DNA-binding and has the potential to halt the proliferation rate of prostate cancer cells. Their target genes overlap by <50% and they execute unique functions in vivo. In addition, even when AR and GR upregulate the same transcriptional target gene, the effect might not be identical in magnitude. Besides being able to drive tumor proliferation, GR is also a key player in prostate cancer cell survival. Stimulation of GR activity can undermine the effects of enhanced antiandrogen treatment, chemotherapy and radiotherapy. GR activation in prostate cancer can increase prosurvival gene expression. Identifying the full spectrum of GR activity will inform the optimal use of glucocorticosteroids in prostate cancer. It will also determine the best strategies to target the protumorigenic effects of GR.

Expanding Therapeutic Opportunities for Extrapulmonary Neuroendocrine Carcinoma

Poorly differentiated neuroendocrine carcinomas (PD-NEC) are rare cancers garnering interest as they become more commonly encountered in the clinic. This is due to improved diagnostic methods and the increasingly observed phenomenon of "NE lineage plasticity," whereby nonneuroendocrine (non-NE) epithelial cancers transition to aggressive NE phenotypes after targeted treatment. Effective treatment options for patients with PD-NEC are challenging for several reasons. This includes a lack of targetable, recurrent molecular drivers, a paucity of patient-relevant preclinical models to study biology and test novel therapeutics, and the absence of validated biomarkers to guide clinical management. Although advances have been made pertaining to molecular subtyping of small cell lung cancer (SCLC), a PD-NEC of lung origin, extrapulmonary (EP)-PD-NECs remain understudied. This review will address emerging SCLC-like, same-organ non-NE cancer-like and tumor-type-agnostic biological vulnerabilities of EP-PD-NECs, with the potential for therapeutic exploitation. The hypotheses surrounding the origin of these cancers and how "NE lineage plasticity" can be leveraged for therapeutic purposes are discussed. SCLC is herein proposed as a paradigm for supporting progress toward precision medicine in EP-PD-NECs. The aim of this review is to provide a thorough portrait of the current knowledge of EP-PD-NEC biology, with a view to informing new avenues for research and future therapeutic opportunities in these cancers of unmet need.

The lactate-NAD+ axis activates cancer-associated fibroblasts by downregulating p62

Reduced p62 levels are associated with the induction of the cancer-associated fibroblast (CAF) phenotype, which promotes tumorigenesis in vitro and in vivo through inflammation and metabolic reprogramming. However, how p62 is downregulated in the stroma fibroblasts by tumor cells to drive CAF activation is an unresolved central issue in the field. Here we show that tumor-secreted lactate downregulates p62 transcriptionally through a mechanism involving reduction of the NAD⁺/NADH ratio, which impairs poly(ADP-ribose)-polymerase 1 (PARP-1) activity. PARP-1 inhibition blocks the poly(ADP-ribosyl)ation of the AP-1 transcription factors, c-FOS and c-JUN, which is an obligate step for p62 downregulation. Importantly, restoring p62 levels in CAFs by NAD⁺ renders CAFs less active. PARP inhibitors, such as olaparib, mimick lactate in the reduction of stromal p62 levels, as well as the subsequent stromal activation both in vitro and in vivo, which suggests that therapies using olaparib would benefit from strategies aimed at inhibiting CAF activity.

Differential Expression of E2F Transcription Factors and Their Functional and Prognostic Roles in Human Prostate Cancer

Given the tumor heterogeneity, most of the current prognostic indicators cannot accurately evaluate the prognosis of patients with prostate cancer, and thus, the best opportunity to intervene in the progression of this disease is missed. E2F transcription factors (E2Fs) have been reported to be involved in the growth of various cancers. Accumulating studies indicate that prostate cancer (PCa) carcinogenesis is attributed to aberrant E2F expression or E2F alteration. However, the expression patterns and prognostic value of the eight E2Fs in prostate cancer have yet to be explored. In this study, The Cancer Genome Atlas (TCGA), Kaplan–Meier Plotter, Metascape, the Kyoto Encyclopedia of Genes and Genomes (KEGG), CIBERSORT, and cBioPortal and bioinformatic analysis were used to investigate E2Fs in patients with PCa. Our results showed that the expression of E2F1–3, E2F5, and E2F6 was higher in prostate cancer tissues than in benign tissues. Furthermore, elevated E2F1–3 and E2F5 expression levels were associated with a higher Gleason score (GS), advanced tumor stage, and metastasis. Survival analysis suggested that high transcription levels of E2F1–3, E2F5, E2F6, and E2F8 were associated with a higher risk of biochemical recurrence. In addition, we developed a prognostic model combining E2F1, E2F6, Gleason score, and the clinical stage that may accurately predict a biochemical recurrence-free survival. Functional enrichment analysis revealed that the E2F family members and their neighboring genes were mainly enriched in cell cycle-related pathways. Somatic mutations in different subgroups were also investigated, and immune components were predicted. Further experiments are warranted to clarify the biological associations between Pca-related E2F family genes, which may influence prognosis via the cell cycle pathway.

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.

Role of MicroRNAs in Neuroendocrine Prostate Cancer

Therapy-induced neuroendocrine prostate cancer (t-NEPC/NEPC) is an aggressive variant of prostate cancer (PCa) that frequently emerges in castration-resistant prostate cancer (CRPC) under the selective pressure of androgen receptor (AR)-targeted therapies. This variant is extremely aggressive, metastasizes to visceral organs, tissues, and bones despite low serum PSA, and is associated with poor survival rates. It arises via a reversible trans-differentiation process, referred to as ‘neuroendocrine differentiation’ (NED), wherein PCa cells undergo a lineage switch and exhibit neuroendocrine features, characterized by the expression of neuronal markers such as enolase 2 (ENO2), chromogranin A (CHGA), and synaptophysin (SYP). The molecular and cellular mechanisms underlying NED in PCa are complex and not clearly understood, which contributes to a lack of effective molecular biomarkers for diagnosis and therapy of this variant. NEPC is thought to derive from prostate adenocarcinomas by clonal evolution. A characteristic set of genetic alterations, such as dual loss of retinoblastoma (RB1) and tumor protein (TP53) tumor suppressor genes and amplifications of Aurora kinase A (AURKA), NMYC, and EZH2, has been reported to drive NEPC. Recent evidence suggests that microRNAs (miRNAs) are important epigenetic players in driving NED in advanced PCa. In this review, we highlight the role of miRNAs in NEPC. These studies emphasize the diverse role that miRNAs play as oncogenes and tumor suppressors in driving NEPC. These studies have unveiled the important role of cellular processes such as the EMT and cancer stemness in determining NED in PCa. Furthermore, miRNAs are involved in intercellular communication between tumor cells and stromal cells via extracellular vesicles/exosomes that contribute to lineage switching. Recent studies support the promising potential of miRNAs as novel diagnostic biomarkers and therapeutic targets for NEPC.

RB1 loss overrides PARP inhibitor sensitivity driven by RNASEH2B loss in prostate cancer

Current targeted cancer therapies are largely guided by mutations of a single gene, which overlooks concurrent genomic alterations. Here, we show that RNASEH2B, RB1, and BRCA2, three closely located genes on chromosome 13q, are frequently deleted in prostate cancer individually or jointly. Loss of RNASEH2B confers cancer cells sensitivity to poly(ADP-ribose) polymerase (PARP) inhibition due to impaired ribonucleotide excision repair and PARP trapping. When co-deleted with RB1, however, cells lose their sensitivity, in part, through E2F1-induced BRCA2 expression, thereby enhancing homologous recombination repair capacity. Nevertheless, loss of BRCA2 resensitizes RNASEH2B/RB1 co-deleted cells to PARP inhibition. Our results may explain some of the disparate clinical results from PARP inhibition due to interaction between multiple genomic alterations and support a comprehensive genomic test to determine who may benefit from PARP inhibition. Last, we show that ATR inhibition can disrupt E2F1-induced BRCA2 expression and overcome PARP inhibitor resistance caused by RB1 loss.

Aggressive variants of prostate cancer: underlying mechanisms of neuroendocrine transdifferentiation

Prostate cancer is a hormone-driven disease and its tumor cell growth highly relies on increased androgen receptor (AR) signaling. Therefore, targeted therapy directed against androgen synthesis or AR activation is broadly used and continually improved. However, a subset of patients eventually progresses to castration-resistant disease. To date, various mechanisms of resistance have been identified including the development of AR-independent aggressive variant prostate cancer based on neuroendocrine transdifferentiation (NED). Here, we review the highly complex processes contributing to NED. Genetic, epigenetic, transcriptional aberrations and posttranscriptional modifications are highlighted and the potential interplay of the different factors is discussed. Background Aggressive variant prostate cancer (AVPC) with traits of neuroendocrine differentiation emerges in a rising number of patients in recent years. Among others, advanced therapies targeting the androgen receptor axis have been considered causative for this development. Cell growth of AVPC often occurs completely independent of the androgen receptor signal transduction pathway and cells have mostly lost the typical cellular features of prostate adenocarcinoma. This complicates both diagnosis and treatment of this very aggressive disease. We believe that a deeper understanding of the complex molecular pathological mechanisms contributing to transdifferentiation will help to improve diagnostic procedures and develop effective treatment strategies. Indeed, in recent years, many scientists have made important contributions to unravel possible causes and mechanisms in the context of neuroendocrine transdifferentiation. However, the complexity of the diverse molecular pathways has not been captured completely, yet. This narrative review comprehensively highlights the individual steps of neuroendocrine transdifferentiation and makes an important contribution in bringing together the results found so far.

Patient-derived xenograft models of neuroendocrine prostate cancer

In recent years, patient-derived xenografts (PDXs) have attracted much attention as clinically relevant models for basic and translational cancer research. PDXs retain the principal histopathological and molecular heterogeneity of their donor tumors and remain stable across passages. These characteristics allow PDXs to offer a reliable platform for better understanding cancer biology, discovering biomarkers and therapeutic targets, and developing novel therapies. A growing interest in generating neuroendocrine prostate cancer (NEPC) PDX models has been demonstrated, and such models have proven useful in several areas. This review provides a comprehensive summary of currently available NEPC PDX collections, encompassing 1) primary or secondary sites where patient samples were collected, 2) donor patients' treatment histories, 3) morphological features (i.e., small cell and large cell), and 4) genomic alterations. We also highlight suitable models for various research purposes, including identifying therapeutic targets and evaluating drug responses in models with specific genomic backgrounds. Finally, we provide perspectives on the current knowledge gaps and shed light on future applications and improvements of NEPC PDXs.

Novel Oncogenic Transcription Factor Cooperation in RB-Deficient Cancer

The retinoblastoma tumor suppressor (RB) is a critical regulator of E2F-dependent transcription, controlling a multitude of protumorigenic networks including but not limited to cell-cycle control. Here, genome-wide assessment of E2F1 function after RB loss in isogenic models of prostate cancer revealed unexpected repositioning and cooperation with oncogenic transcription factors, including the major driver of disease progression, the androgen receptor (AR). Further investigation revealed that observed AR/E2F1 cooperation elicited novel transcriptional networks that promote cancer phenotypes, especially as related to evasion of cell death. These observations were reflected in assessment of human disease, indicating the clinical relevance of the AR/E2F1 cooperome in prostate cancer. Together, these studies reveal new mechanisms by which RB loss induces cancer progression and highlight the importance of understanding the targets of E2F1 function. SIGNIFICANCE: This study identifies that RB loss in prostate cancer drives cooperation between AR and E2F1 as coregulators of transcription, which is linked to the progression of advanced disease.

The long noncoding RNA H19 regulates tumor plasticity in neuroendocrine prostate cancer

Neuroendocrine (NE) prostate cancer (NEPC) is a lethal subtype of castration-resistant prostate cancer (PCa) arising either de novo or from transdifferentiated prostate adenocarcinoma following androgen deprivation therapy (ADT). Extensive computational analysis has identified a high degree of association between the long noncoding RNA (lncRNA) H19 and NEPC, with the longest isoform highly expressed in NEPC. H19 regulates PCa lineage plasticity by driving a bidirectional cell identity of NE phenotype (H19 overexpression) or luminal phenotype (H19 knockdown). It contributes to treatment resistance, with the knockdown of H19 re-sensitizing PCa to ADT. It is also essential for the proliferation and invasion of NEPC. H19 levels are negatively regulated by androgen signaling via androgen receptor (AR). When androgen is absent SOX2 levels increase, driving H19 transcription and facilitating transdifferentiation. H19 facilitates the PRC2 complex in regulating methylation changes at H3K27me3/H3K4me3 histone sites of AR-driven and NEPC-related genes. Additionally, this lncRNA induces alterations in genome-wide DNA methylation on CpG sites, further regulating genes associated with the NEPC phenotype. Our clinical data identify H19 as a candidate diagnostic marker and predictive marker of NEPC with elevated H19 levels associated with an increased probability of biochemical recurrence and metastatic disease in patients receiving ADT. Here we report H19 as an early upstream regulator of cell fate, plasticity, and treatment resistance in NEPC that can reverse/transform cells to a treatable form of PCa once therapeutically deactivated.

Elevated expression of long noncoding RNA H19 is seen in clinical samples of neuroendocrine prostate cancer (PCa). Here the authors show H19 promotes plasticity from luminal to neuroendocrine by epigenetic reprogramming.

Delineating the Molecular Events Underlying Development of Prostate Cancer Variants with Neuroendocrine/Small Cell Carcinoma Characteristics

The treatment landscape of prostate cancer has changed dramatically following the advent of novel systemic therapies, most of which target the androgen receptor (AR). Agents such as abiraterone, enzalutamide, apalutamide, darolutamide were designed to further suppress androgen receptor signaling following gonadal suppression achieved by first-line androgen deprivation therapies. These potent AR targeting agents are increasingly used in the earlier stages of the disease spectrum with the goal of delaying disease progression and extending survival. Although these therapies are effective in controlling prostate tumors dependent on or addicted to AR signaling, prostate tumors surviving the onslaught of potent treatments may evolve and develop drug resistance. A substantial proportion of treatment failures can be explained by the development of treatment-induced aggressive prostate cancer variants such as neuroendocrine/small cell carcinoma. These emerging disease entities demand detailed characterization and precise definitions. We postulate that these treatment-induced prostate cancer entities should be defined molecularly to overcome the drawbacks associated with the current clinical and pathological definitions. A precise molecular definition conforms with current knowledge on the molecular evolution of this disease entity and will enable early detection and early intervention.

PARP5B is required for nonhomologous end joining during tumorigenesis in vivo

Poly(ADP-ribose) polymerases (PARP) act as DNA damage sensors that produce poly(ADP-ribose) (PAR) chains at double-strand breaks, facilitating the recruitment of repair factors. Cancers with homologous recombination defects are sensitive to small molecule PARP inhibitors. Despite PARP5B gene copy number changes in many cancers, the effects of this genetic alteration on tumor phenotype are largely unknown. To better understand this clinical finding, we characterized a PARP5B null mutation in a carcinogen-induced in vivo head and neck squamous cell carcinoma (SCC) model. Reduced PARP5B expression inhibited tumor growth, induced primary tumor differentiation and apoptosis, and inhibited cell proliferation and metastasis. Loss of PARP5B expression-induced ataxia telangiectasia and Rad3 related (ATR) activation and depleted the cancer stem cell fraction. PARP5B null tumor cells lacked 53BP1+ double-strand break foci, ATM activation, and p53 induction compared to PARP5B+/+ cancers. PARP5B null SCC expresses a multiprotein complex containing PML, pRPA, Rad50, Rad51, XRCC1, proliferating cell nuclear antigen (PCNA), and Mcm2, suggesting an HR-mediated repair mechanism at DNA replication foci. Low doses of etoposide combined with the PARP5B inhibitor XAV939 induced senescence and apoptosis in human SCC lines. NBS1 overexpression in these cells inhibited the effects of low-dose etoposide/XAV939 treatment. Our results indicate that PARP5B inhibition is new targeted cancer therapy.

PARP and CDK4/6 Inhibitor Combination Therapy Induces Apoptosis and Suppresses Neuroendocrine Differentiation in Prostate Cancer

We analyzed the efficacy and mechanistic interactions of PARP inhibition (PARPi; olaparib) and CDK4/6 inhibition (CDK4/6i; palbociclib or abemaciclib) combination therapy in castration-resistant prostate cancer (CRPC) and neuroendocrine prostate cancer (NEPC) models. We demonstrated that combined olaparib and palbociblib or abemaciclib treatment resulted in synergistic suppression of the p-Rb1-E2F1 signaling axis at the transcriptional and posttranslational levels, leading to disruption of cell-cycle progression and inhibition of E2F1 gene targets, including genes involved in DDR signaling/damage repair, antiapoptotic BCL-2 family members (BCL-2 and MCL-1), CDK1, and neuroendocrine differentiation (NED) markers in vitro and in vivo In addition, olaparib + palbociclib or olaparib + abemaciclib combination treatment resulted in significantly greater growth inhibition and apoptosis than either single agent alone. We further showed that PARPi and CDK4/6i combination treatment-induced CDK1 inhibition suppressed p-S70-BCL-2 and increased caspase cleavage, while CDK1 overexpression effectively prevented the downregulation of p-S70-BCL-2 and largely rescued the combination treatment-induced cytotoxicity. Our study defines a novel combination treatment strategy for CRPC and NEPC and demonstrates that combination PARPi and CDK4/6i synergistically promotes suppression of the p-Rb1-E2F1 axis and E2F1 target genes, including CDK1 and NED proteins, leading to growth inhibition and increased apoptosis in vitro and in vivo Taken together, our results provide a molecular rationale for PARPi and CDK4/6i combination therapy and reveal mechanism-based clinical trial opportunities for men with NEPC.

A New Old Target: Androgen Receptor Signaling and Advanced Prostate Cancer

Owing to the development of multiple novel therapies, there has been major progress in the treatment of advanced prostate cancer over the last two decades; however, the disease remains invariably fatal. Androgens and the androgen receptor (AR) play a critical role in prostate carcinogenesis, and targeting the AR signaling axis with abiraterone, enzalutamide, darolutamide, and apalutamide has improved outcomes for men with this lethal disease. Targeting the AR and elucidating mechanisms of resistance to these agents remains central to drug development efforts. This review provides an overview of the evolution and current approaches for targeting the AR in advanced prostate cancer. It describes the biology of AR signaling, explores AR-targeting resistance mechanisms, and discusses future perspectives and promising novel therapeutic strategies. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Castration-Induced Downregulation of SPARC in Stromal Cells Drives Neuroendocrine Differentiation of Prostate Cancer

Fatal neuroendocrine differentiation (NED) of castration-resistant prostate cancer is a recurrent mechanism of resistance to androgen deprivation therapies (ADT) and antiandrogen receptor pathway inhibitors (ARPI) in patients. The design of effective therapies for neuroendocrine prostate cancer (NEPC) is complicated by limited knowledge of the molecular mechanisms governing NED. The paucity of acquired genomic alterations and the deregulation of epigenetic and transcription factors suggest a potential contribution from the microenvironment. In this context, whether ADT/ARPI induces stromal cells to release NED-promoting molecules and the underlying molecular networks are unestablished. Here, we utilized transgenic and transplantable mouse models and coculture experiments to unveil a novel tumor-stroma cross-talk that is able to induce NED under the pressure of androgen deprivation. Castration induced upregulation of GRP78 in tumor cells, which triggers miR29-b-mediated downregulation of the matricellular protein SPARC in the nearby stroma. SPARC downregulation enabled stromal cells to release IL6, a known inducer of NED. A drug that targets GRP78 blocked NED in castrated mice. A public, human NEPC gene expression dataset showed that Hspa5 (encoding for GRP78) positively correlates with hallmarks of NED. Finally, prostate cancer specimens from patients developing local NED after ADT showed GRP78 upregulation in tumor cells and SPARC downregulation in the stroma. These results point to GRP78 as a potential therapeutic target and to SPARC downregulation in stromal cells as a potential early biomarker of tumors undergoing NED. SIGNIFICANCE: Tumor-stroma cross-talk promotes neuroendocrine differentiation in prostate cancer in response to hormone therapy via a GRP78/SPARC/IL6 axis, providing potential therapeutic targets and biomarkers for neuroendocrine prostate cancer.

Post-translational modifications of CDK5 and their biological roles in cancer

Post-translational modifications (PTMs) of Cyclin-dependent kinase 5 (CDK5) have emerged as important regulatory mechanisms that modulate cancer development in patients. Though CDK5 is an atypical member of the cyclin-dependent kinase family, its aberrant expression links to cell proliferation, DNA damage response, apoptosis, migration and angiogenesis in cancer. Current studies suggested that, new PTMs on CDK5, including S-nitrosylation, sumoylation, and acetylation, serve as molecular switches to control the kinase activity of CDK5 in the cell. However, a majority of these modifications and their biological significance in cancer remain uncharacterized. In this review, we discussed the role of PTMs on CDK5-mediated signaling cascade, and their possible mechanisms of action in malignant tumors, as well as the challenges and future perspectives in this field. On the basis of the newly identified regulatory signaling pathways of CDK5 related to PTMs, researchers have investigated the cancer therapeutic potential of chemical compounds, small-molecule inhibitors, and competitive peptides by targeting CDK5 and its PTMs. Results of these preclinical studies demonstrated that targeting PTMs of CDK5 yields promising antitumor effects and that clinical translation of these therapeutic strategies is warranted.

Therapy considerations in neuroendocrine prostate cancer: what next?

Lineage plasticity and histologic transformation to small cell neuroendocrine prostate cancer (NEPC) is an increasingly recognized mechanism of treatment resistance in advanced prostate cancer. This is associated with aggressive clinical features and poor prognosis. Recent work has identified genomic, epigenomic, and transcriptome changes that distinguish NEPC from prostate adenocarcinoma, pointing to new mechanisms and therapeutic targets. Treatment-related NEPC arises clonally from prostate adenocarcinoma during the course of disease progression, retaining early genomic events and acquiring new molecular features that lead to tumor proliferation independent of androgen receptor activity, and ultimately demonstrating a lineage switch from a luminal prostate cancer phenotype to a small cell neuroendocrine carcinoma. Identifying the subset of prostate tumors most vulnerable to lineage plasticity and developing strategies for earlier detection and intervention for patients with NEPC may ultimately improve prognosis. Clinical trials focused on drug targeting of the lineage plasticity process and/or NEPC will require careful patient selection. Here, we review emerging targets and discuss biomarker considerations that may be informative for the design of future clinical studies.

Unravelling the molecular mechanisms of prostate cancer evolution from genotype to phenotype

Prostate cancer (PC) is the most frequently diagnosed cancer and the second leading cause of cancer-related death in men in the Western society. Unfortunately, although the vast majority of patients are initially responsive to androgen-deprivation therapy (ADT), most cases eventually develop from hormone-sensitive prostate cancer (HSPC) to castration-resistant prostate cancer (CRPC). The main reason is PC heterogeneity and evolution during therapy. PC evolution is a continuously progressive process with combination of genomic alterations including canonical AR, TMPRSS2-ERG fusion, SPOP/FOXA1, TP53/RB1/PTEN, BRCA2. Meanwhile, signaling pathways including PI3K, WNT/β-catenin, SRC, IL-6/STAT3 are activated, to promote epithelial mesenchymal transition (EMT), cancer stem cell (CSC)-like features/stemness and neuroendocrine differentiation (NED) of PC. These improve our understanding of the genotype-phenotype relationships. The identification of canonical genetic alterations and signaling pathway activation in PC has shed more insight into genetic background, molecular subtype and disease landscape of PC evolution, resulting in a more flexible role of individual therapies targeting diverse genotype and phenotype presentation.

PARP Inhibitors in Cancer Diagnosis and Therapy

Targeting of PARP enzymes has emerged as an effective therapeutic strategy to selectively target cancer cells with deficiencies in homologous recombination signaling. Currently used to treat BRCA-mutated cancers, PARP inhibitors (PARPi) have demonstrated improved outcome in various cancer types as single agents. Ongoing efforts have seen the exploitation of PARPi combination therapies, boosting patient responses as a result of drug synergisms. Despite great successes using PARPi therapy, selecting those patients who will benefit from single agent or combination therapy remains one of the major challenges. Numerous reports have demonstrated that the presence of a BRCA mutation does not always result in synthetic lethality with PARPi therapy in treatment-naïve tumors. Cancer cells can also develop resistance to PARPi therapy. Hence, combination therapy may significantly affect the treatment outcomes. In this review, we discuss the development and utilization of PARPi in different cancer types from preclinical models to clinical trials, provide a current overview of the potential uses of PARP imaging agents in cancer therapy, and discuss the use of radiolabeled PARPi as radionuclide therapies.

Long Non-coding RNA SENP3-EIF4A1 Functions as a Sponge of miR-195-5p to Drive Triple-Negative Breast Cancer Progress by Overexpressing CCNE1

Triple-negative breast cancer (TNBC) has high malignancy and limited treatment, so novel molecular therapeutic targets are urgently needed. Cyclin E1 (CCNE1) promotes progression in breast cancer, but its role and inherent mechanisms in TNBC are yet to be elucidated. Competing endogenous RNA (ceRNA) may be a potential mechanism. CCNE1 was selected though bioinformatics and clinical samples, and cell lines were utilized to verify CCNE1 expression by qRT-PCR and western blot. Predicting tools provided potential miR-195-5p and SENP3-EIF4A1 and tested from multilevel. Functional experiments were conducted in vitro and in vivo. Luciferase reporter assay and RNA immunoprecipitation experiments were implemented to ensure the interaction between miR-195-5p and SENP3-EIF4A1/CCNE1 in TNBC. Bioinformatics found DNA hypermethylation of miR-195-5p and preliminarily verified. Mechanistically, SENP3-EIF4A1-miR-195-5p-associated ceRNA could drive TNBC progress though regulating CCNE1. DNA hypermethylation of miR-195-5p might be another reason. In summary, SENP3-EIF4A1-miR-195-5p-CCNE1 axis promotes TNBC progress and may contribute to the novel diagnosis and treatment of TNBC.

Androgen receptor signaling-targeted therapy and taxane chemotherapy induce visceral metastasis in castration-resistant prostate cancer

BACKGROUND

Visceral metastasis (VM), an important poor prognostic factor of prostate cancer (PC), is not commonly observed in castration sensitive status but is often observed after castration-resistant progression. However, the site, timing of emergence, and incidence of VM in castration-resistant patients have not yet been fully elucidated.

METHODS

Demographic, surgical, pathological, and follow-up data of PC patients treated at Kanazawa University Hospital between January 2000 and December 2016 were retrospectively analyzed using their medical charts. From this data, risk factors of VM and survival of patients with VM were elucidated.

RESULTS

Of 1364 patients, 21 (1.5%) had VM at diagnosis. Of 179 (13.1%) castration-resistant patients, 55 experienced emergence of new VM during treatment course. Incidence of new VM, especially nonlung, such as liver and adrenal metastases, increased significantly in proportion with the number of prescribed treatments. Multivariate analysis revealed that T stage, M stage, age, and treatment history with androgen receptor (AR) signaling-targeted agents and/or taxanes significantly increased the risk of VM. Compared with the group with VM at diagnosis, survival after diagnosis of VM following treatment was significantly shorter.

CONCLUSION

Although sequential use of new AR signaling-targeted agents and taxanes for castration-resistant PC (CRPC) is a standard treatment strategy, it often results in development of VM. Elucidating the mechanisms of VM are essential to improve survival in patients with CRPC.

MicroRNA determinants of neuroendocrine differentiation in metastatic castration-resistant prostate cancer

Therapy-induced neuroendocrine prostate cancer (NEPC), an extremely aggressive variant of castration-resistant prostate cancer (CRPC), is increasing in incidence with the widespread use of highly potent androgen receptor (AR)-pathway inhibitors (APIs) such as Enzalutamide (ENZ) and Abiraterone and arises via a reversible trans-differentiation process, referred to as neuroendocrine differentiation (NED). The molecular basis of NED is not completely understood leading to a lack of effective molecular markers for its diagnosis. Here, we demonstrate for the first time, that lineage switching to NE states is accompanied by key miRNA alterations including downregulation of miR-106a~363 cluster and upregulation of miR-301a and miR-375. To systematically investigate the key miRNAs alterations driving therapy-induced NED, we performed small RNA-NGS in a retrospective cohort of human metastatic CRPC clinical samples + PDX models with adenocarcinoma features (CRPC-adeno) vs those with neuroendocrine features (CRPC-NE). Further, with the application of machine learning algorithms to sequencing data, we trained a 'miRNA classifier' that could robustly classify 'CRPC-NE' from 'CRPC-Adeno' cases. The performance of classifier was validated in an additional cohort of mCRPC patients and publicly available PCa cohorts. Importantly, we demonstrate that miR-106a~363 cluster pleiotropically regulate cardinal nodal proteins instrumental in driving NEPC including Aurora Kinase A, N-Myc, E2F1 and STAT3. Our study has important clinical implications and transformative potential as our 'miRNA classifier' can be used as a molecular tool to stratify mCRPC patients into those with/without NED and guide treatment decisions. Further, we identify novel miRNA NED drivers that can be exploited for NEPC therapeutic targeting.

Resistance Mechanisms to Taxanes and PARP Inhibitors in Advanced Prostate Cancer

The clinical landscape concerning advanced prostate cancer is rapidly changing and reaching beyond androgen deprivation therapy and androgen receptor targeted therapies. Taxane chemotherapy is a critical tool in the management of advanced prostate cancer. Additionally, novel drug classes such as PARP inhibitors are being investigated. Despite tremendous progress, resistance to therapy remains as a major impediment to further improvement. Resistance mechanisms appear diverse and are not fully known or understood. This review will highlight recent advances in research regarding mechanisms of resistance to both taxanes (such as increased drug efflux capacity) and PARP inhibitors (such as reversion mutations which restore DNA-repair proficiency). Understanding resistance to therapy promises to remove barriers blocking progress toward improved patient outcomes.