TCF4 induces enzalutamide resistance via neuroendocrine differentiation in prostate cancer

Current uses and resistance mechanisms of enzalutamide in prostate cancer treatment

INTRODUCTION

Prostate cancer continues to be a major cause of morbidity and mortality for men worldwide. Enzalutamide, a second-generation non-steroidal antiandrogen that blocks androgen receptor (AR) transcriptional activity, is a treatment for biochemically recurrent, metastatic, castration-sensitive, and castration-resistant tumors. Unfortunately, most patients ultimately develop resistance to enzalutamide, making long-term treatment with this agent challenging.

AREAS COVERED

We performed a literature search of PubMed without date restrictions to investigate the literature surrounding enzalutamide and discuss the current uses of enzalutamide, proposed mechanisms driving resistance, and summarize current efforts to mitigate this resistance.

EXPERT OPINION

Enzalutamide is an effective prostate cancer therapy that is currently used in biochemically recurrent and metastatic disease and for both castration-sensitive and castration-resistant tumors. Unfortunately, resistance to enzalutamide occurs in each of these scenarios. In the clinical setting, enzalutamide-resistant tumors are either AR-driven or AR-indifferent. AR-dependent resistance mechanisms include genomic or epigenomic events that result in enhanced AR signaling. Tumors that do not require AR signaling instead may depend on alternative oncogenic pathways. There are numerous strategies to mitigate enzalutamide resistance, including concurrent use of PARP inhibitors or immune therapies. Additional work is required to uncover novel approaches to treat patients in the enzalutamide-resistant setting.

Mechanism-centric regulatory network identifies NME2 and MYC programs as markers of Enzalutamide resistance in CRPC

Heterogeneous response to Enzalutamide, a second-generation androgen receptor signaling inhibitor, is a central problem in castration-resistant prostate cancer (CRPC) management. Genome-wide systems investigation of mechanisms that govern Enzalutamide resistance promise to elucidate markers of heterogeneous treatment response and salvage therapies for CRPC patients. Focusing on the de novo role of MYC as a marker of Enzalutamide resistance, here we reconstruct a CRPC-specific mechanism-centric regulatory network, connecting molecular pathways with their upstream transcriptional regulatory programs. Mining this network with signatures of Enzalutamide response identifies NME2 as an upstream regulatory partner of MYC in CRPC and demonstrates that NME2-MYC increased activities can predict patients at risk of resistance to Enzalutamide, independent of co-variates. Furthermore, our experimental investigations demonstrate that targeting MYC and its partner NME2 is beneficial in Enzalutamide-resistant conditions and could provide an effective strategy for patients at risk of Enzalutamide resistance and/or for patients who failed Enzalutamide treatment.

In vitro study of miRNA-369-3p targeting TCF4 regulating the malignant biological behavior of colon cancer cells

Background

Colorectal carcinoma (CRC) is a common malignant tumor of the digestive tract. It is characterized by a high degree of malignancy, early metastasis and poor prognosis. Studies have shown the effect of miR-369-3p on the biological function of a variety of tumors. However, the mechanism by which miR-369-3p and its potential target genes participate in the pathogenesis of CRC has not been elucidated. This study aims to study the relationship between miR-369-3p and transcription factor 4 (TCF4), to reveal the mechanism of the occurrence and development of CRC, and to provide a promising target for the treatment of CRC.

Methods

Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the miR-369-3p levels in CRC tissues and cells. miR-369-3p mimics and/or TCF4 overexpression vectors were transfected into SW480 cells. The expression of miR-369-3p and TCF4 mRNA was detected using RT-qPCR. Bioinformatics analysis predicted the binding site of miR-369-3p to the TCF4 3'UTR, and the targeting relationship was verified by a dual luciferase reporter gene assay. Cell proliferation and invasion were investigated by labeled immunofluorescence assay using BrdU antibody and Transwell assay. The oxidative stress ability of cells was determined by commercial kits. The levels of proteins related to cell proliferation and invasion were measured by western blotting.

Results

The level of miR-369-3p was significantly down-regulated in CRC tissues and cell lines, especially in SW480 cells (P<0.05). The expression of TCF4 was negatively correlated with that of miR-369-3p. High levels of miR-369-3p targeting TCF4 suppressed cell proliferation and downregulated the protein expression of Ki67 and PCNA (P<0.05). Overexpressed miR-369-3p binding TCF4 inhibited cell invasion and decreased the protein levels of vascular endothelial growth factor (VEGF) and E-cadherin (P<0.05). Furthermore, upregulation of miR-369-3p increased the activity of superoxide dismutase (SOD) while decreasing the content of malondialdehyde (MDA) and activity of lactate dehydrogenase (LDH) by blocking the expression of TCF4 (P<0.05).

Conclusions

MiR-369-3p inhibits the proliferation, invasion and oxidative stress of CRC cells by targeting TCF4, thus defining miR-369-3p as a potential target for the diagnosis and treatment of CRC.

Wnt Signaling and Therapeutic Resistance in Castration-Resistant Prostate Cancer

Purpose of Review

Castration-resistant prostate cancer (CRPC) is a lethal form of prostate cancer (PCa) due to the development of resistance to androgen deprivation therapy and anti-androgens. Here, we review the emerging role of Wnt signaling in therapeutic resistance of CRPC.

Recent Findings

Convincing evidence have accumulated that Wnt signaling is aberrantly activated through genomic alterations and autocrine and paracrine augmentations. Wnt signaling plays a critical role in a subset of CRPC and in resistance to anti-androgen therapies. Wnt signaling navigates CRPC through PCa heterogeneity, neuroendocrine differentiation, DNA repair, PCa stem cell maintenance, epithelial-mesenchymal-transition and metastasis, and immune evasion.

Summary

Components of Wnt signaling can be harnessed for inhibiting PCa growth and metastasis and for developing novel therapeutic strategies to manage metastatic CRPC. There are many Wnt pathway-based potential drugs in different stages of pre-clinical development and clinical trials but so far, no Wnt signaling-specific drug has been approved by FDA for clinical use in CRPC.

LNP-miR-155 cy5 Inhibitor Regulates the Copper Transporter via the β-Catenin/TCF4/SLC31A1 Signal for Colorectal Cancer Therapy

Lipid nanoparticle (LNP) delivery systems are widely used in the delivery of small-molecule drugs and nucleic acids. In this study, we prepared LNP-miR-155 by lipid nanomaterial technology and investigated the effects of LNP-miR-155 on β-catenin/transcription factor 4 (TCF4)/solute carrier family 31 member 1/copper transporter 1 (SLC31A1/CTR1) signaling and copper transport in colorectal cancer. For this, we used an LNP-miR-155 cy5 inhibitor and LNP-miR-155 cy5 mimics for the transfection of HT-29/SW480 cells. The transfection efficiency and uptake efficiency were detected by immunofluorescence. Relevant cell assays confirmed that the LNP-miR-155 cy5 inhibitor mediates the regulation of copper transport through the β-catenin/TCF4/SLC31A1 axis. The LNP-miR-155 cy5 inhibitor reduced cell proliferation, migration, and colony formation and promoted cell apoptosis. We also confirmed that miR-155 downregulates HMG box-containing protein 1 (HBP1) and adenomatous polyposis coli (APC) in cells and activates the function of β-catenin/TCF4 signaling. In addition, we found that the copper transporter, SLC31A1, is highly expressed in colorectal cancer cells. Furthermore, we also found that the complex β-catenin/TCF4 promotes the transcription of SLC31A1 by binding to its promoter region, which sustains the transport of copper from the extracellular region to the intracellular region and increases the activities of Cu2+-ATPase and superoxide dismutase (SOD). In summary, the LNP-miR-155 cy5 inhibitor regulates β-catenin/TCF4 by downregulating SLC31A1-mediated copper transport and intracellular copper homeostasis.

Epiregulin expression and secretion is increased in castration-resistant prostate cancer

Introduction

In prostate cancer, long-term treatment directed against androgens often leads to the development of metastatic castration-resistant prostate cancer, which is more aggressive and not curatively treatable. Androgen deprivation results in elevated epiregulin expression in LNCaP cells which is a ligand of EGFR. This study aims to reveal the expression and regulation of epiregulin in different prostate cancer stages enabling a more specific molecular characterization of different prostate carcinoma types.

Methods

Five different prostate carcinoma cell lines were used to characterize the epiregulin expression on the RNA and protein levels. Epiregulin expression and its correlation with different patient conditions were further analyzed using clinical prostate cancer tissue samples. Additionally, the regulation of epiregulin biosynthesis was examined at transcriptional, post-transcriptional and release level.

Results

An increased epiregulin secretion is detected in castration-resistant prostate cancer cell lines and prostate cancer tissue samples indicating a correlation of epiregulin expression with tumor recurrence, metastasis and increased grading. Analysis regarding the activity of different transcription factors suggests the involvement of SMAD2/3 in the regulation of epiregulin expression. In addition, miR-19a, -19b, and -20b are involved in post-transcriptional epiregulin regulation. The release of mature epiregulin occurs via proteolytic cleavage by ADAM17, MMP2, and MMP9 which are increased in castration-resistant prostate cancer cells.

Discussion

The results demonstrate epiregulin regulation by different mechanism and suggest a potential role as a diagnostic tool to detect molecular alterations in prostate cancer progression. Additionally, although EGFR inhibitors false in prostate cancer, epiregulin could be a therapeutic target for patients with castration-resistant prostate cancer.

What genes are differentially expressed in individuals with schizophrenia? A systematic review

Schizophrenia is a severe, complex mental disorder characterized by a combination of positive symptoms, negative symptoms, and impaired cognitive function. Schizophrenia is highly heritable (~80%) with multifactorial etiology and complex polygenic genetic architecture. Despite the large number of genetic variants associated with schizophrenia, few causal variants have been established. Gaining insight into the mechanistic influences of these genetic variants may facilitate our ability to apply these findings to prevention and treatment. Though there have been more than 300 studies of gene expression in schizophrenia over the past 15 years, none of the studies have yielded consistent evidence for specific genes that contribute to schizophrenia risk. The aim of this work is to conduct a systematic review and synthesis of case-control studies of genome-wide gene expression in schizophrenia. Comprehensive literature searches were completed in PubMed, EmBase, and Web of Science, and after a systematic review of the studies, data were extracted from those that met the following inclusion criteria: human case-control studies comparing the genome-wide transcriptome of individuals diagnosed with schizophrenia to healthy controls published between January 1, 2000 and June 30, 2020 in the English language. Genes differentially expressed in cases were extracted from these studies, and overlapping genes were compared to previous research findings from the genome-wide association, structural variation, and tissue-expression studies. The transcriptome-wide analysis identified different genes than those previously reported in genome-wide association, exome sequencing, and structural variation studies of schizophrenia. Only one gene, GBP2, was replicated in five studies. Previous work has shown that this gene may play a role in immune function in the etiology of schizophrenia, which in turn could have implications for risk profiling, prevention, and treatment. This review highlights the methodological inconsistencies that impede valid meta-analyses and synthesis across studies. Standardization of the use of covariates, gene nomenclature, and methods for reporting results could enhance our understanding of the potential mechanisms through which genes exert their influence on the etiology of schizophrenia. Although these results are promising, collaborative efforts with harmonization of methodology will facilitate the identification of the role of genes underlying schizophrenia.

Exploring the Wnt Pathway as a Therapeutic Target for Prostate Cancer

Aberrant activation of the Wnt pathway is emerging as a frequent event during prostate cancer that can facilitate tumor formation, progression, and therapeutic resistance. Recent discoveries indicate that targeting the Wnt pathway to treat prostate cancer may be efficacious. However, the functional consequence of activating the Wnt pathway during the different stages of prostate cancer progression remains unclear. Preclinical work investigating the efficacy of targeting Wnt signaling for the treatment of prostate cancer, both in primary and metastatic lesions, and improving our molecular understanding of treatment responses is crucial to identifying effective treatment strategies and biomarkers that help guide treatment decisions and improve patient care. In this review, we outline the type of genetic alterations that lead to activated Wnt signaling in prostate cancer, highlight the range of laboratory models used to study the role of Wnt genetic drivers in prostate cancer, and discuss new mechanistic insights into how the Wnt cascade facilitates prostate cancer growth, metastasis, and drug resistance.

Small interfering RNA targeting N-cadherin regulates cell proliferation and migration in enzalutamide-resistant prostate cancer

Enzalutamide is one of the options for treating patients with castration-resistant or metastatic prostate cancer. However, a substantial proportion of patients become resistant to enzalutamide after a period of treatment. Cells in these tumors typically exhibit increased proliferative and migratory capabilities, in which N-cadherin (CDH2) appear to serve an important role. In the present study, by up- and downregulating the expression of CDH2, the possible effects of CDH2 on the prostate cancer cell line LNCaP were investigated. Male sex hormone-sensitive LNCaP cells treated with 10 µM enzalutamide were named LNCaP enzalutamide-resistant (EnzaR) cells. Reverse transcription-PCR, western blotting and immunofluorescence staining were used to measure CDH2, E-cadherin, α-SMA, Snail and Slug expression. Transfection with the pCMV-CDH2 plasmid was performed for CDH2 upregulation, whilst transfection with small interfering RNA (siRNA)-CDH2 was performed for CDH2 downregulation. MTT and Cell Counting Kit-4 assays were used to evaluate the proportion of viable cancer cells. Subsequently, gap closure assay was performed to evaluate the migratory capability of both LNCaP and LNCaP EnzaR cell lines. CDH2 expression was found to be increased in LNCaP EnzaR cells compared with that in LNCaP cells. CDH2 overexpression increased cell viability and migration in both LNCaP and LNCaP EnzaR cell lines. By contrast, the opposite trend was observed after CDH2 expression was knocked down. CDH2 expression also showed a high association with that of four epithelial-mesenchymal transition markers, which was confirmed by western blotting. Based on these results, it was concluded that knocking down CDH2 expression using siRNA transfection mediated significant influence on LNCaP EnzaR cell physiology, which may be a potential therapeutic option for prostate cancer treatment.

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.

Single-cell RNA sequencing reveals spatiotemporal heterogeneity and malignant progression in pancreatic neuroendocrine tumor

Aims: Using Single-cell RNA sequencing (scRNA-seq), we explored the spatiotemporal heterogeneity of pancreatic neuroendocrine tumors (pNETs) and the underlying mechanism for malignant progression.

Methods: scRNA-seq was conducted on three tumor tissues (two primary tissues from different sites, one liver metastatic lesion), one normal liver tissue, and peripheral blood mononuclear cells from one patient with a metastatic G2 pNET, followed by bioinformatics analysis and validation in a pNETs cohort.

Results: The transcriptome data of 24.544 cells were obtained. We identified subpopulations of functional heterogeneity within malignant cells, immune cells, and fibroblasts. There were intra- and inter-heterogeneities of cell subpopulations for malignant cells, macrophages, T cells, and fibroblasts among all tumor sites. Cell trajectory analysis revealed several hallmarks of carcinogenesis, including the hypoxia pathway, metabolism reprogramming, and aggressive proliferation, which were activated at different stages of tumor progression. Evolutionary analysis based on mitochondrial mutations defined two dominant clones with metastatic capacity. Finally, we developed a gene signature (PCSK1 and SMOC1) defining the metastatic potential of the tumor and its prognostic value was validated in a cohort of thirty G1/G2 patients underwent surgical resection.

Conclusions: Our scRNA-seq analysis revealed intra- and intertumor heterogeneities in cell populations, transcriptional states, and intercellular communications among primary and metastatic lesions of pNETs. The single-cell level characterization of the spatiotemporal dynamics of malignant cell progression provided new insights into the search for potential novel prognostic biomarkers of pNETs.

miR-20a/TCF4 axis-mediated inhibition of hepatocytes proliferation impairs liver regeneration in mice PHx model by regulating CDC2 and CDC6

MicroRNAs have emerged as essential regulators in the biological process of liver regeneration by modulating the post‐transcriptional expression of the target genes. In the present study, we found miR‐20a expression is decreased remarkably in three rodent liver regeneration models using miRNA PCR array and Venn diagram analysis. Inhibition of miR‐20a expression enhanced hepatocytes proliferation in vivo and in vitro. In contrast, overexpression of miR‐20a reduces hepatocytes proliferation and subsequently impaired liver regeneration in the mouse PHx model. Moreover, we have identified TCF4 as a target gene of miR‐20a using the PCR Array and luciferase assay. Next, mice with TCF4 deficiency were used to establish the PHx model and subjected to the examination of liver regeneration capacity. We found TCF4‐deficient mice exhibited impaired liver regeneration compared with control. Given that TCF4 acts as a transcription factor, we sort to elucidate the downstream genes involved in liver regeneration. Promoter analysis and Chip assay confirmed that TCF4 enhances CDC2 and CDC6 expression through binding to the promoter region and leads to the proliferation and cell cycle progression in hepatocytes. In conclusion, this study provides evidence that the miR20a‐TCF4‐CDC2/6 axis plays an essential role during liver regeneration.

Transcription factor 4 expression in circulating tumor cells from castration-resistant prostate cancer

INTRODUCTION

Neuroendocrine differentiation is partly caused by antiandrogen therapy and exhibits an androgen receptor-independent growth mechanism. We hypothesized that the expression of transcription factor 4, an inducer of neuroendocrine differentiation, in circulating tumor cells is related to drug resistance in castration-resistant prostate cancer.

CASE PRESENTATION

We evaluate the messenger ribonucleic acid expression of transcription factor 4 in circulating tumor cells from 17 patients with castration-resistant prostate cancer and compared these levels between patients receiving antiandrogen therapies and those who were resistant to antiandrogen therapies and receiving chemotherapies. The expression of transcription factor 4 in circulating tumor cells was significantly higher among patients receiving chemotherapies.

CONCLUSION

This study shows that transcription factor 4 is higher in the group of patients who were judged by their physicians to need chemotherapy treatment.

Novel Strategies for Treating Castration-Resistant Prostate Cancer

The development of castration resistance is an inevitable pathway for the vast majority of patients with advanced prostate cancer. Recently, there have been significant breakthroughs in the understanding and management options of castration-resistant prostate cancer. Three novel hormonal agents showed survival benefits in non-metastatic patients. As for metastatic disease, there was an even wider range of management options being investigated. This review summarized advances in the management of castration-resistant prostate cancer (CRPC) including emerging data on novel imaging techniques and treatment strategies.

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.

WLS-Wnt signaling promotes neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC) is a lethal prostate cancer subtype arising as a consequence of more potent androgen receptor (AR) targeting in castration-resistant prostate cancer (CRPC). Its molecular pathogenesis remains elusive. Here, we report that the Wnt secretion mediator Wntless (WLS) is a major driver of NEPC and aggressive tumor growth in vitro and in vivo. Mechanistic studies showed that WLS is a transcriptional target suppressed by AR that activates the ROR2/PKCδ/ERK signaling pathway to support the neuroendocrine (NE) traits and proliferative capacity of NEPC cells. Analysis of clinical samples and datasets revealed that WLS was highly expressed in CRPC and NEPC tumors. Finally, treatment with the Wnt secretion inhibitor LGK974 restricted NE prostate tumor xenograft growth in mice. These findings collectively characterize the contribution of WLS to NEPC pathogenesis and suggest that WLS is a potential therapeutic target in NEPC.

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WLS is highly expressed in neuroendocrine prostate cancer clinical samples

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WLS is a transcriptional target suppressed by androgen receptor

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WLS drives neuroendocrine prostate cancer through the ROR2/PKCδ/ERK pathway

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Wnt secretion inhibitor treatment limits neuroendocrine prostate tumor growth in mice

An up-to-date evaluation of darolutamide for the treatment of prostate cancer

Introduction: Currently, in prostate cancer, an increasing number of novel drugs are being used to delay its advancement to metastatic castration-resistant prostate cancer (mCRPC). Apalutamide, enzalutamide, and most recently, darolutamide (novel androgen receptor antagonists) have been approved for nonmetastatic castration-resistant prostate cancer (nmCRPC).Areas covered: The authors have evaluated darolutamide, covering all aspects of the clinical development, competence, and safety profile of the drug.Expert opinion: The unique structure of darolutamide is characterized by a high affinity for androgen receptors and detainment of antagonist activity in mutant isoforms of androgen receptors. In clinical practice, this is the main reason that makes darolutamide exceptional in terms of safety and efficacy compared to other drugs in this category. Darolutamide is considered to have the lowest probability for adverse events (AEs) compared to apalutamide and enzalutamide. Future studies, along with real-world clinical data are warranted to improve personalized treatment strategies as well as sequencing treatment between approved novel drugs.

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.

Silencing TCF4 Sensitizes Melanoma Cells to Vemurafenib Through Inhibiting GLUT3-Mediated Glycolysis

Background

Vemurafenib is a selective BRAF inhibitor with significant early effects in melanoma, but resistance will develop with the duration of treatment. Therefore, overcoming vemurafenib resistance can effectively improve the survival rate of melanoma. The transcriptional activity of TCF4 is necessary to maintain the malignant phenotype of cancer cells. However, the effect of TCF4 on melanoma sensitivity to vemurafenib and the underlying mechanism is unclear.

Methods

Vemurafenib-resistant A375 (A375/Vem) and SK-Mel-28 (SK-Mel-28/Vem) cells were constructed by administering increasing concentrations of vemurafenib, and the expression of TCF4 was examined in parent and vemurafenib-resistant cells. TCF4 loss-function cells models were established in A375/Vem and SK-Mel-28/Vem cells, respectively. Cell survival, clone formation, and cell apoptosis were assessed. The downstream target gene of TCF4 was verified by chromatin immunoprecipitation. Finally, the effect of TCF4 on melanoma cells glycolysis was investigated and were performed.

Results

TCF4 expression was increased in vemurafenib-resistant melanoma cells, and knocking down TCF4 could promote the sensitivity of melanoma cells to vemurafenib. Mechanism investigation revealed that TCF4 could interact with GLUT3 and silencing TCF4 could inhibit GLUT3 expression. In addition, overexpression of GLUT3 reversed the growth and glycolysis of tumor cells that were inhibited by TCF4 knockdown.

Conclusion

Our study demonstrates that TCF4 downregulation sensitizes melanoma cells to vemurafenib through inhibiting GLUT3-mediated glycolysis. These findings support TCF4 as an oncogene and provide new mechanism by which TCF4 confers chemotherapy resistance in melanoma.