NeuroD1 Expression in Human Prostate Cancer: Can It Contribute to Neuroendocrine Differentiation Comprehension?

Therapeutic Exploitation of Neuroendocrine Transdifferentiation Drivers in Prostate Cancer

Neuroendocrine prostate cancer (NEPC), an aggressive and lethal subtype of prostate cancer (PCa), often arises as a resistance mechanism in patients undergoing hormone therapy for prostate adenocarcinoma. NEPC is associated with a significantly poor prognosis and shorter overall survival compared to conventional prostate adenocarcinoma due to its aggressive nature and limited response to standard of care therapies. This transdifferentiation, or lineage reprogramming, to NEPC is characterised by the loss of androgen receptor (AR) and prostate-specific antigen (PSA) expression, and the upregulation of neuroendocrine (NE) biomarkers such as neuron-specific enolase (NSE), chromogranin-A (CHGA), synaptophysin (SYP), and neural cell adhesion molecule 1 (NCAM1/CD56), which are critical for NEPC diagnosis. The loss of AR expression culminates in resistance to standard of care PCa therapies, such as androgen-deprivation therapy (ADT) which target the AR signalling axis. This review explores the drivers of NE transdifferentiation. Key genetic alterations, including those in the tumour suppressor genes RB1, TP53, and PTEN, and changes in epigenetic regulators, particularly involving EZH2 and cell-fate-determining transcription factors (TFs) such as SOX2, play significant roles in promoting NE transdifferentiation and facilitate the lineage switch from prostate adenocarcinoma to NEPC. The recent identification of several other key novel drivers of NE transdifferentiation, including MYCN, ASCL1, BRN2, ONECUT2, and FOXA2, further elucidates the complex regulatory networks and pathways involved in this process. We suggest that, given the multifactorial nature of NEPC, novel therapeutic strategies that combine multiple modalities are essential to overcome therapeutic resistance and improve patient outcomes.

NEUROD1: transcriptional and epigenetic regulator of human and mouse neuronal and endocrine cell lineage programs

Transcription factors belonging to the basic helix-loop-helix (bHLH) family are key regulators of cell fate specification and differentiation during development. Their dysregulation is implicated not only in developmental abnormalities but also in various adult diseases and cancers. Recently, the abilities of bHLH factors have been exploited in reprogramming strategies for cell replacement therapy. One such factor is NEUROD1, which has been associated with the reprogramming of the epigenetic landscape and potentially possessing pioneer factor abilities, initiating neuronal developmental programs, and enforcing pancreatic endocrine differentiation. The review aims to consolidate current knowledge on NEUROD1's multifaceted roles and mechanistic pathways in human and mouse cell differentiation and reprogramming, exploring NEUROD1 roles in guiding the development and reprogramming of neuroendocrine cell lineages. The review focuses on NEUROD1's molecular mechanisms, its interactions with other transcription factors, its role as a pioneer factor in chromatin remodeling, and its potential in cell reprogramming. We also show a differential potential of NEUROD1 in differentiation of neurons and pancreatic endocrine cells, highlighting its therapeutic potential and the necessity for further research to fully understand and utilize its capabilities.

Yin Yang 1 promotes the neuroendocrine differentiation of prostate cancer cells via the non-canonical WNT pathway (FYN/STAT3)

BACKGROUND

A growing number of studies have shown that Yin Yang 1 (YY1) promotes the development of multiple tumours. The purpose of the current study was to determine the mechanism by which YY1 mediates neuroendocrine differentiation of prostate cancer (NEPC) cells undergoing cellular plasticity.

METHODS

Using the Cancer Genome Atlas and Gene Expression Omnibus (GEO) databases, we bioinformatically analyzed YY1 expression in prostate cancer (PCa). Aberrant YY1 expression was validated in different PCa tissues and cell lines via quantitative reverse transcription polymerase chain reaction, western blotting, and immunohistochemistry. In vivo and in vitro functional assays verified the oncogenicity of YY1 in PCa. Further functional assays showed that ectopic expression of YY1 promoted cellular plasticity in PCa cells via epithelial-mesenchymal transition induction and neuroendocrine differentiation.

RESULTS

Androgen deprivation therapy induced a decrease in YY1 protein ubiquitination, enhanced its stability, and thus enhanced the transcriptional activity of FZD8. Castration enhanced FZD8 binding to Wnt9A and mediated cellular plasticity by activating the non-canonical Wnt (FZD8/FYN/STAT3) pathway.

CONCLUSIONS

We identified YY1 as a novel dysregulated transcription factor that plays an important role in NEPC progression in this study. We believe that an in-depth investigation of the mechanism underlying YY1-mediated disease may lead to improved NEPC therapies.

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.

Perineural invasion-associated biomarkers for tumor development

Perineural invasion (PNI) is the process of neoplastic invasion of peripheral nerves and is considered to be the fifth mode of cancer metastasis. PNI has been detected in head and neck tumors and pancreatic, prostate, bile duct, gastric, and colorectal cancers. It leads to poor prognostic outcomes and high local recurrence rates. Despite the increasing number of studies on PNI, targeted therapeutic modalities have not been proposed. The identification of PNI-related biomarkers would facilitate the non-invasive and early diagnosis of cancers, the establishment of prognostic panels, and the development of targeted therapeutic approaches. In this review, we compile information on the molecular mediators involved in PNI-associated cancers. The expression and prognostic significance of molecular mediators and their receptors in PNI-associated cancers are analyzed, and the possible mechanisms of action of these mediators in PNI are explored, as well as the association of cells in the microenvironment where PNI occurs.

The Role of Perineural Invasion in Prostate Cancer and Its Prognostic Significance

Simple Summary

Prostate cancer is one of the most frequently diagnosed cancers in men worldwide. Perineural invasion (PNI), the movement of cancer cells along nerves, is a commonly observed approach to tumor spread and is important in both research and clinical practice of prostate cancer. However, despite many studies reporting on molecules and pathways involved in PNI, understanding its clinical relevance remains insufficient. In this review, we aim to summarize the current knowledge of mechanisms and prognostic significance of PNI in prostate cancer, which may provide new perspectives for future studies and improved treatment.

Abstract

Perineural invasion (PNI) is a common indication of tumor metastasis that can be detected in multiple malignancies, including prostate cancer. In the development of PNI, tumor cells closely interact with the nerve components in the tumor microenvironment and create the perineural niche, which provides a supportive surrounding for their survival and invasion and benefits the nerve cells. Various transcription factors, cytokines, chemokines, and their related signaling pathways have been reported to be important in the progress of PNI. Nevertheless, the current understanding of the molecular mechanism of PNI is still very limited. Clinically, PNI is commonly associated with adverse clinicopathological parameters and poor outcomes for prostate cancer patients. However, whether PNI could act as an independent prognostic predictor remains controversial among studies due to inconsistent research aim and endpoint, sample type, statistical methods, and, most importantly, the definition and inclusion criteria. In this review, we provide a summary and comparison of the prognostic significance of PNI in prostate cancer based on existing literature and propose that a more standardized description of PNI would be helpful for a better understanding of its clinical relevance.

NeuroD1 promotes tumor cell proliferation and tumorigenesis by directly activating the pentose phosphate pathway in colorectal carcinoma

Tumor metabolic reprogramming ensures that cancerous cells obtain sufficient building blocks, energy, and antioxidants to sustain rapid growth and for coping with oxidative stress. Neurogenic differentiation factor 1 (NeuroD1) is upregulated in various types of tumors; however, its involvement in tumor cell metabolic reprogramming remains unclear. In this study, we report that NeuroD1 is positively correlated with glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in the pentose phosphate pathway (PPP), in colorectal cancer cells. In addition, the regulation of G6PD by NeuroD1 alters tumor cell metabolism by stimulating the PPP, leading to enhanced production of nucleotides and NADPH. These, in turn, promote DNA and lipid biosynthesis in tumor cells, while decreasing intracellular levels of reactive oxygen species. Mechanistically, we showed that NeuroD1 binds directly to the G6PD promoter to activate G6PD transcription. Consequently, tumor cell proliferation and colony formation are enhanced, leading to increased tumorigenic potential in vitro and in vivo. These findings reveal a novel function of NeuroD1 as a regulator of G6PD, whereby its oncogenic activity is linked to tumor cell metabolic reprogramming and regulation of the PPP. Furthermore, NeuroD1 represents a potential target for metabolism-based anti-tumor therapeutic strategies.

Neuroendocrine cells in prostate cancer correlate with poor outcomes: a systematic review and meta-analysis

OBJECTIVES

To perform a systematic review and meta-analysis of the literature to understand the variation in the reporting of neuroendocrine staining and determine the influence of reporting neuroendocrine staining at diagnosis on patient outcomes.

METHODS

Medical databases were searched to identify studies in which adenocarcinoma specimens were stained with any of the following four neuroendocrine markers: chromogranin A (CgA), neuron-specific enolase (NSE), synaptophysin and CD56. The prevalence of neuroendocrine staining and correlation of the prevalence of neuroendocrine staining to patient outcomes were analysed using a random-effects model. All statistical tests were two-sided.

RESULTS

Sixty-two studies spanning 7616 patients were analysed. The pooled prevalence for the most common marker, CgA (41%), was similar to that of NSE (39%) and higher than that of synaptophysin (31%). The prevalence of CgA staining was significantly influenced by reporting criteria, where objective thresholds reduced the variation in prevalence to 26%. No correlation was found between CgA prevalence and tumour grade. Patients positive for CgA staining using objective criteria had more rapid biochemical progression (hazard ratio [HR] 1.98, 95% confidence interval [CI] 1.49 to 2.65) and poorer prostate cancer-specific survival (HR 7.03, 95% CI 2.55 to 19.39) compared to negative patients, even among those with low-risk cancers.

CONCLUSION

Discrepancies in the reported prevalence of neuroendocrine cells in adenocarcinoma are driven by the inconsistent scoring criteria. This study unequivocally demonstrates that when neuroendocrine cell staining is assessed with objective criteria it identifies patients with poor clinical outcomes. Future studies are needed to determine the exact quantifiable thresholds for use in reporting neuroendocrine cell staining to identify patients at higher risk of progression.

Neural Transcription Factors in Disease Progression

Progression to the malignant state is fundamentally dependent on transcriptional regulation in cancer cells. Optimum abundance of cell cycle proteins, angiogenesis factors, immune evasion markers, etc. is needed for proliferation, metastasis or resistance to treatment. Therefore, dysregulation of transcription factors can compromise the normal prostate transcriptional network and contribute to malignant disease progression.The androgen receptor (AR) is considered to be a key transcription factor in prostate cancer (PCa) development and progression. Consequently, androgen pathway inhibitors (APIs) are currently the mainstay in PCa treatment, especially in castration-resistant prostate cancer (CRPC). However, emerging evidence suggests that with increased administration of potent APIs, prostate cancer can progress to a highly aggressive disease that morphologically resembles small cell carcinoma, which is referred to as neuroendocrine prostate cancer (NEPC), treatment-induced or treatment-emergent small cell prostate cancer. This chapter will review how neuronal transcription factors play a part in inducing a plastic stage in prostate cancer cells that eventually progresses to a more aggressive state such as NEPC.

Cooperation among heterogeneous prostate cancer cells in the bone metastatic niche

The growth of disseminated tumor cells into metastatic lesions depends on the establishment of a favorable microenvironment in the stroma of the target organs. Here we show that mice treated with anakinra, an antagonist of the interleukin (IL)-1β receptor (IL-1R), or harboring a targeted deletion of IL-1R are significantly less prone to develop bone tumors when inoculated in the arterial circulation with human prostate cancer (PCa) cells expressing IL-1β. Interestingly, human mesenchymal stem cells exposed in vitro to medium conditioned by IL-1β-expressing cancer cells responded by upregulating S100A4, a marker of cancer-associated fibroblasts (CAFs), and this effect was blocked by anakinra. Analogously, the stroma adjacent to skeletal metastases generated in mice by IL-1β-expressing cancer cells showed a dramatic increase in S100A4, COX-2 and the alteration of 30 tumor-related genes as measured by Nanostring analysis. These effects were not observed in the stroma associated with the rare and much smaller metastases generated by the same cells in IL-1R knockout animals, confirming that tumor-secreted IL-1β generates skeletal CAFs and conditions the surrounding bone microenvironment. In skeletal lesions from patients with metastatic PCa, histological and molecular analyses revealed that IL-1β is highly expressed in cancer cells in which the androgen receptor (AR) is not detected (AR-), whereas this cytokine is uniformly absent in the AR-positive (AR+) metastatic cells. The stroma conditioned by IL-1β-expressing cancer cells served as a supportive niche also for coexisting IL-1β-lacking cancer cells, which are otherwise unable to generate tumors after independently seeding the skeleton of mice. This niche is established very early following tumor seeding and hints to a role of IL-1β in promoting early colonization of PCa at the skeletal level.

The role of high cell density in the promotion of neuroendocrine transdifferentiation of prostate cancer cells

Background

Tumor heterogeneity and the plasticity of cancer cells present challenges for effective clinical diagnosis and therapy. Such challenges are epitomized by neuroendocrine transdifferentiation (NED) and the emergence of neuroendocrine-like cancer cells in prostate tumors. This phenomenon frequently arises from androgen-depleted prostate adenocarcinoma and is associated with the development of castration-resistant prostate cancer and poor prognosis.

Results

In this study, we showed that NED was evoked in both androgen receptor (AR)-positive and AR-negative prostate epithelial cell lines by growing the cells to a high density. Androgen depletion and high-density cultivation were both associated with cell cycle arrest and deregulated expression of several cell cycle regulators, such as p27^Kip1, members of the cyclin D protein family, and Cdk2. Dual inhibition of Cdk1 and Cdk2 using pharmacological inhibitor or RNAi led to modulation of the cell cycle and promotion of NED. We further demonstrated that the cyclic adenosine 3′, 5′-monophosphate (cAMP)-mediated pathway is activated in the high-density conditions. Importantly, inhibition of cAMP signaling using a specific inhibitor of adenylate cyclase, MDL-12330A, abolished the promotion of NED by high cell density.

Conclusions

Taken together, our results imply a new relationship between cell cycle attenuation and promotion of NED and suggest high cell density as a trigger for cAMP signaling that can mediate reversible NED in prostate cancer cells.

Duodenal gangliocytic paraganglioma, a rare entity among GEP-NET: a case report with immunohistochemical and molecular study

Gastroenteropancreatic neuroendocrine tumors are the most incident neuroendocrine tumors. In the new WHO classification (2010) the embryological derivation of each neoplastic entity is one of the most important parameters. Gangliocytic Paraganglioma is a tumor originating in the hindgut, a rare neoplasm, generally affecting the second portion of the duodenum, the majority of which are benign.

Cases of gangliocytic paraganglioma with local metastasis or local recurrence have also been reported.

We describe a GP in a 48-year-old caucasian male with an unusual site (4th portion of duodenum) and an interesting immunohistochemical and molecular pattern. In particular, we examined the expression of some neuroendocrine markers and a marker of neuronal differentiation, NeuroD1, whose expression can help to better understand the nature of this neoplasia.

Control of IGFBP-2 Expression by Steroids and Peptide Hormones in Vertebrates

IGFBP-2 (1) has been described as a brain tumor oncogene (2) and is widely expressed in cancers from different origins (3-8). IGFBP-2 alone cannot cause malignant transformation, yet progression of brain tumors to higher grade (9) and also has been provided as a protective element in earlier stages of multistage colon carcinogenesis (10). Therefore, it is crucial to understand the factors that determine expression patterns of IGFBP-2 under normal and malignant conditions. The present review provides a comprehensive update of known factors that have an impact on expression of IGFBP-2.

NeuroD1 regulation of migration accompanies the differential sensitivity of neuroendocrine carcinomas to TrkB inhibition

The developmental transcription factor NeuroD1 is anomalously expressed in a subset of aggressive neuroendocrine tumors. Previously, we demonstrated that TrkB and neural cell adhesion molecule (NCAM) are downstream targets of NeuroD1 that contribute to the actions of neurogenic differentiation 1 (NeuroD1) in neuroendocrine lung. We found that several malignant melanoma and prostate cell lines express NeuroD1 and TrkB. Inhibition of TrkB activity decreased invasion in several neuroendocrine pigmented melanoma but not in prostate cell lines. We also found that loss of the tumor suppressor p53 increased NeuroD1 expression in normal human bronchial epithelial cells and cancer cells with neuroendocrine features. Although we found that a major mechanism of action of NeuroD1 is by the regulation of TrkB, effective targeting of TrkB to inhibit invasion may depend on the cell of origin. These findings suggest that NeuroD1 is a lineage-dependent oncogene acting through its downstream target, TrkB, across multiple cancer types, which may provide new insights into the pathogenesis of neuroendocrine cancers.

NeuroD1 regulates survival and migration of neuroendocrine lung carcinomas via signaling molecules TrkB and NCAM

Small-cell lung cancer and other aggressive neuroendocrine cancers are often associated with early dissemination and frequent metastases. We demonstrate that neurogenic differentiation 1 (NeuroD1) is a regulatory hub securing cross talk among survival and migratory-inducing signaling pathways in neuroendocrine lung carcinomas. We find that NeuroD1 promotes tumor cell survival and metastasis in aggressive neuroendocrine lung tumors through regulation of the receptor tyrosine kinase tropomyosin-related kinase B (TrkB). Like TrkB, the prometastatic signaling molecule neural cell adhesion molecule (NCAM) is a downstream target of NeuroD1, whose impaired expression mirrors loss of NeuroD1. TrkB and NCAM may be therapeutic targets for aggressive neuroendocrine cancers that express NeuroD1.

HOX D13 expression across 79 tumor tissue types

HOX genes control normal development, primary cellular processes and are characterized by a unique genomic network organization. Locus D HOX genes play an important role in limb generation and mesenchymal condensation. Dysregulated HOXD13 expression has been detected in breast cancer, melanoma, cervical cancer and astrocytomas. We have investigated the epidemiology of HOXD13 expression in human tissues and its potential deregulation in the carcinogenesis of specific tumors. HOXD13 homeoprotein expression has been detected using microarray technology comprising more than 4,000 normal and neoplastic tissue samples including 79 different tumor categories. Validation of HOXD13 expression has been performed, at mRNA level, for selected tumor types. Significant differences are detectable between specific normal tissues and corresponding tumor types with the majority of cancers showing an increase in HOXD13 expression (16.1% normal vs. 57.7% cancers). In contrast, pancreas and stomach tumor subtypes display the opposite trend. Interestingly, detection of the HOXD13 homeoprotein in pancreas-tissue microarrays shows that its negative expression has a significant and adverse effect on the prognosis of patients with pancreatic cancer independent of the T or N stage at the time of diagnosis. Our study provides, for the first time, an overview of a HOX protein expression in a large series of normal and neoplastic tissue types, identifies pancreatic cancer as one of the most affected by the HOXD13 hoemoprotein and underlines the way homeoproteins can be associated to human cancerogenesis.

Neuroendocrine cancer-specific up-regulating mechanism of insulin-like growth factor binding protein-2 in small cell lung cancer

Small cell lung cancer (SCLC) exhibits insulin-like growth factor-dependent growth. SCLC is the most aggressive among known in vivo lung cancers, whereas in vitro growth of SCLC is paradoxically slow as compared with that of non-SCLC (NSCLC). In this study, we demonstrate that SCLC cells overexpress insulin-like growth factor binding protein (IGFBP)-2 via NeuroD, a neuroendocrine cell-specific transcription factor. Chromatin immunoprecipitation, electrophoretic mobility shift, and IGFBP-2 promoter assays all revealed that NeuroD binds to the E-box in the 5'-untranslated region of IGFBP-2. A NeuroD transgene in both airway epithelial and NSCLC cells up-regulated the transcription of IGFBP-2 and retarded cell growth. Recombinant IGFBP-2 repressed the growth of both airway epithelial and NSCLC cells in a dose-dependent manner. A NeuroD-specific small interfering RNA repressed IGFBP-2 expression in SCLC, and neutralization of IGFBP-2 and an IGFBP-2-specific small interfering RNA increased SCLC cell growth. Pathological samples of SCLC also expressed IGFBP-2 abundantly, as compared with NSCLC, and showed only rare (8%) IGFBP-2 promoter methylation, whereas the IGFBP-2 promoter was methylated in 71% of adenocarcinomas and 29% of squamous cell carcinomas. These findings suggest that 1) SCLC has an IGFBP-2 overexpression mechanism distinct from NSCLC, 2) secreted IGFBP-2 contributes to the slow growth of SCLC in vitro, and 3) the epigenetic alterations in the IGFBP-2 promoter contribute to the striking differences in IGFBP-2 expression between SCLC and NSCLC in vivo.

Oct4A is expressed by a subpopulation of prostate neuroendocrine cells

BACKGROUND

Cancer stem cells are defined by their self-renewal and multi-potential capabilities and are hypothesized to be the source of primary and recurrent cancers. The stem cell properties of self-renewal and pluripotency in embryonic stem cells and germ cells are regulated by Oct4A, a splice variant of the POU5F1 (Oct3/4) gene, while the function of the alternative splice variant, Oct4B, is unknown. Rare cells that express Oct4 were identified in several somatic cancers, however, the differential contributions of the Oct4A and Oct4B variants were not determined.

METHODS

Oct4A expression and co-localization with lineage markers was performed with PCR and immunohistochemistry.

RESULTS

Rare Oct4A expressing cells are present in human benign and malignant prostate glands and the number of Oct4A expressing cells increases in prostate cancers with high Gleason scores. Oct4A expressing cells were non-proliferative, and did not co-express markers of basal epithelial cell or luminal epithelial cell differentiation, or AMACR, a marker of prostate cancer epithelial cells. A subpopulation of the Oct4A expressing cells co-expressed Sox2, an embryonic stem cell marker, but did not express other putative stem cell markers, such as ABCG2, NANOG or CD133. The majority of Oct4A expressing cells co-expressed chromogranin A, and a subset of Oct4A expressing cells co-expressed synaptophysin, both markers of neuroendocrine differentiation.

CONCLUSION

The increased number of cells that expressed Oct4A in prostate cancer compared to benign prostate, and in cancers of increasing grade, suggests that Oct4A/Chromogranin A co-expressing cells represent neuroendocrine cells in prostate cancer.

Neuroendocrine differentiation in prostate cancer: from lab to bedside

OBJECTIVES

To discuss the current knowledge on induction, production, sustenance and promotion of neuroendocrine differentiation in human prostate cancer.

METHODS

Review of the literature using PubMed search and scientific journal publications.

RESULTS

Morphological evidence explains some functional relationship between neuroendocrine and neoplastic surrounding cells. Transdifferentiation phenomenon and new biochemical pathways could be included in the development of androgen independence and prostate cancer progression.

CONCLUSION

Multiple evidence seems to confirm that a synergistic functional network between epithelial PSA secretory cells and neuroendocrine intraprostatic system is the main trigger for the induction and sustenance of neuroendocrine differentiation. The development of new antineoplastic molecules should consider the multiple interference of the intercellular network.