The axon guidance molecule semaphorin 3F is a negative regulator of tumor progression and proliferation in ileal neuroendocrine tumors

Novel therapeutic approaches in GEP-NETs based on genetic and epigenetic alterations

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are heterogeneous malignancies with distinct prognosis based on primary tumor localization, grade, stage and functionality. Surgery remains the only curative option in localized tumors, but systemic therapy is the mainstay of treatment for patients with advanced disease. For decades, the therapeutic landscape of GEP-NETs was limited to chemotherapy regimens with low response rates. The arrival of novel agents such as somatostatin analogues, peptide receptor radionuclide therapy, tyrosine kinase inhibitors or mTOR-targeted drugs, has changed the therapeutic paradigm of GEP-NETs. However, the efficacy of these agents is limited in time and there is scarce knowledge of optimal treatment sequencing. In recent years, massive parallel sequencing techniques have started to unravel the genomic intricacies of these tumors, allowing us to better understand the mechanisms of resistance to current treatments and to develop new targeted agents that will hopefully start an era for personalized treatment in NETs. In this review we aim to summarize the most relevant genomic aberrations and signaling pathways underlying GEP-NET tumorigenesis and potential therapeutic strategies derived from them.

Semaphorin 3F induces colorectal cancer cell chemosensitivity by promoting P27 nuclear export

Colorectal adenocarcinoma (CRC) is the third most common malignancy worldwide. Metastatic CRC has a poor prognosis because of chemotherapy resistance. Our previous study demonstrated that semaphorin 3F (SEMA3F) signaling may contribute to reversing chemotherapy resistance in CRC cells by reducing E-cadherin and integrin αvβ3 expression levels. Another study showed that upregulation of p27 significantly increase the expression of E-cadherin and integrin. This study aimed to evaluate the effect of SEMA3F on P27 and whether it can reverse resistance in CRC cells. We compared the chemosensitivity of human colorectal cancer cell lines with different SEMA3F expression levels to 5-Fu through cell experiment and animal experiment. Then the interaction between SEMA3F and p27 and its possible mechanism were explored by Western Blot, immunofluorescence and immunocoprecipitation. We also compared the disease-free survival of 118 CRC patients with high or low expression of SEMA3F.The results showed that overexpresstion of SEMA3F enhanced the chemotherapy sensitivity and apoptosis of CRC cells in vitro and in vivo. Among 118 postoperative CRC specimens, the disease-free survival of patients with positive SEMA3F expression was significantly longer than that with negative SEMA3F expression after adjuvant treatment. Upregulation of SEMA3F in multicellular spheroid culture (MSC) could increase p27 phosphorylation at serine 10 (Ser10), subsequently promote the cytosolic translocation of P27. Overall, our results reveal a novel molecular mechanism: SEMA3F mediates the degradation of p27 and regulates its subcellular localization to enhance chemosensitivity to 5-Fu in CRC cells, rather than inhibits p27 expression.

Angiogenesis in NENs, with a focus on gastroenteropancreatic NENs: from biology to current and future therapeutic implications

Neuroendocrine neoplasms (NENs) are highly vascularized malignancies arising from cells of the diffuse neuroendocrine system. An intricated cross-talk exists between NEN cells and the tumor microenvironment, and three main molecular circuits (VEGF/VEGFR pathway, FGF-dependent signaling and PDGF/PDGFR axis) have been shown to regulate angiogenesis in these neoplasms. Multiple randomized trials have investigated antiangiogenic agents over the past two decades, and sunitinib is currently approved for the treatment of advanced, progressive, G1/G2 pancreatic NENs. In recent years, two phase III clinical trials have demonstrated the efficacy and safety of surufatinib, a multi-tyrosine kinase angioimmune inhibitor, in patients with well-differentiated pancreatic and extrapancreatic NENs, and two studies of this agent are currently underway in Europe and US. The HIF-2α inhibitor belzutifan has recently received regulatory approval for the treatment of tumors arising in the context of Von-Hippel Lindau syndrome including pancreatic NENs, and a study of this drug in patients with sporadic tumors is presently ongoing. Combinations of antiangiogenic agents with chemotherapeutics and targeted drugs have been tested, with accumulating toxicities being a matter of concern. The potential of antiangiogenic agents in fine-tuning the immune microenvironment of NENs to enhance the activity of immune checkpoint inhibitors has been only partially elucidated, and further research should be carried out at this regard. Here, we review the current understanding of the biology of angiogenesis in NENs and provide a summary of the latest clinical investigations on antiangiogenic drugs in this malignancy.

Updates to the Management of Patients With Relapsed or Refractory Indolent Follicular and Marginal Zone Lymphomas

Although follicular lymphoma (FL) and marginal zone lymphoma (MZL) share similarities, the 2 diseases have distinct biologic differences that affect their presentation and treatment. Stage I disease is more common in MZL than in FL due to marginal zone biology, for example, and stage I MZL is curable by surgery or radiation therapy. Newer therapies for both FL and MZL provide chemotherapy-free options, but they are not identical. Brüton’s tyrosine kinase inhibitors are active in relapsed or refractory MZL but not in FL, for example. CAR T-cell therapy has just been approved for treatment of FL and is an ongoing area of investigation for both diseases.

Genetic Drivers of Ileal Neuroendocrine Tumors

Simple Summary

Although ileal neuroendocrine tumors are the most common tumors of the small intestine, they are not well-defined at the genetic level. Unlike most cancers, they have an unusually low number of mutations, and also lack recurrently mutated genes. Moreover ileal NETs have been difficult to study in the laboratory because there were no animal models and because cell lines were generally unavailable. But recent advances, including the first ileal NET mouse model as well as methods for culturing patient tumor samples, have been described and have already helped to identify IGF2 and CDK4 as two of the genetic drivers for this tumor type. These advances may help in the development of new treatments for patients.

Abstract

The genetic causes of ileal neuroendocrine tumors (ileal NETs, or I-NETs) have been a mystery. For most types of tumors, key genes were revealed by large scale genomic sequencing that demonstrated recurrent mutations of specific oncogenes or tumor suppressors. In contrast, genomic sequencing of ileal NETs demonstrated a distinct lack of recurrently mutated genes, suggesting that the mechanisms that drive the formation of I-NETs may be quite different than the cell-intrinsic mutations that drive the formation of other tumor types. However, recent mouse studies have identified the IGF2 and RB1 pathways in the formation of ileal NETs, which is supported by the subsequent analysis of patient samples. Thus, ileal NETs no longer appear to be a cancer without genetic causes.

Exploring the Epigenome in Gastroenteropancreatic Neuroendocrine Neoplasias

Gastroenteropancreatic neuroendocrine neoplasias are a diverse group of neoplasms with different characteristics in terms of site, biological behaviour and metastatic potential. In comparison to other cancers, they are genetically quiet, harbouring relatively few somatic mutations. It is increasingly becoming evident that epigenetic changes are as relevant, if not more so, as somatic mutations in promoting oncogenesis. Despite significant tumour heterogeneity, it is obvious that DNA methylation, histone and chromatin modifications and microRNA expression profiles are distinctive for GEP-NEN subtypes and may correlate with clinical outcome. This review summarises existing knowledge on epigenetic changes, identifying potential contributions to pathogenesis and oncogenesis. In particular, we focus on epigenetic changes pertaining to well-differentiated neuroendocrine tumours, which make up the bulk of NENs. We also highlight both similarities and differences within the subtypes of GEP-NETs and how these relate and compare to other types of cancers. We relate epigenetic understanding to existing treatments and explore how this knowledge may be exploited in the development of novel treatment approaches, such as in theranostics and combining conventional treatment modalities. We consider potential barriers to epigenetic research in GEP-NENs and discuss strategies to optimise research and development of new therapies.

Class-3 semaphorins: Potent multifunctional modulators for angiogenesis-associated diseases

Semaphorins, the neuronal guidance cues, were shown to have broad influences on pathophysiological processes such as bone remodeling, immune responses, and angiogenesis. In particular, Class-3 Semaphorins (SEMA3) is considered a vital regulator involved in angiogenesis. Scientific evidence has pointed to the role of angiogenesis in many diseases, and numerous efforts have been made to explore the possibilities of curing those diseases by targeting angiogenesis. Nevertheless, the efficacies are limited owing to the complex mechanisms of angiogenesis. Hence, investigating the mechanisms of SEMA3 in angiogenesis may contribute to novel therapeutics for diseases. Previous reviews mainly focused on the various functions of semaphorins in one particular disease, and the specific angiogenesis mechanism of SEMA3 in diverse diseases has not been well elucidated. Additionally, the role of SEMA3 in angiogenesis remains elusive, as contradicting results have been found in different disease types. Some evidence from recent studies implies that, while most SEMA3 molecules inhibit pathological angiogenesis in different diseases, occasionally SEMA3 may also promote angiogenesis. This review summarizes the specific role of SEMA3 in a variety of angiogenesis-associated diseases, and documents SEMA3 may be a promising therapeutic target for treating angiogenesis-associated diseases.

SEMA3F Promotes Liver Hepatocellular Carcinoma Metastasis by Activating Focal Adhesion Pathway

Previous studies have shown that semaphorin-3F (SEMA3F) functions as a tumor suppressor in several tumor types. However, the role of SEMA3F in the metastasis and prognosis of liver hepatocellular carcinoma (LIHC) remains unknown. In this study, by performing bioinformatics analysis on the transcriptome profiles from The Cancer Genome Atlas (TCGA), we demonstrated that SEMA3F was significantly upregulated in LIHC tissues, compared with normal controls. Moreover, the expression value of SEMA3F was positively correlated with patients' pathological stages and tumor metastasis, predicting a poor overall survival. Besides, SEMA3F expression level was negatively correlated with its methylation level, but positively correlated with its gene copy number. Differential expression analysis of LIHC samples with high or low SEMA3F expression values suggested that 983 genes were differentially expressed, among which 723 genes were upregulated and 260 genes were downregulated. Furthermore, enrichment analysis of differentially expressed genes revealed that SEMA3F was involved in the activation of focal adhesion pathway, which induced tumor metastasis. Taken together, our results suggested that the oncogenic function of SEMA3F promoted hepatocellular carcinoma metastasis by activating focal adhesion pathway.

Neuropilin-2 contributes to tumor progression in preclinical models of small intestinal neuroendocrine tumors

The identification of novel regulators of tumor progression is a key challenge to gain knowledge on the biology of small intestinal neuroendocrine tumors (SI-NETs). We recently identified the loss of the axon guidance protein semaphorin 3F as a protumoral event in SI-NETs. Interestingly the expression of its receptor neuropilin-2 (NRP-2) was still maintained. This study aimed at deciphering the potential role of NRP-2 as a contributor to SI-NET progression. The role of NRP-2 in SI-NET progression was addressed using an approach integrating human tissue and serum samples, cell lines and in vivo models. Data obtained from human SI-NET tissues showed that membranous NRP-2 expression is present in a majority of tumors, and is correlated with invasion, metastatic abilities, and neovascularization. In addition, NRP-2 soluble isoform was found elevated in serum samples from metastatic patients. In preclinical mouse models of NET progression, NRP-2 silencing led to a sustained antitumor effect, partly driven by the downregulation of VEGFR2. In contrast, its ectopic expression conferred a gain of aggressiveness, driven by the activation of various oncogenic signaling pathways. Lastly, NRP-2 inhibition led to a decrease of tumor cell viability, and sensitized to therapeutic agents. Overall, our results point out NRP-2 as a potential therapeutic target for SI-NETs, and will foster the development of innovative strategies targeting this receptor. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Molecular prognostic factors in small-intestinal neuroendocrine tumours

BACKGROUND

Small-intestinal neuroendocrine tumours (SI-NETs) represent a heterogeneous group of rare tumours. In recent years, basic research in SI-NETs has attempted to unravel the molecular events underlying SI-NET tumorigenesis.

AIM

We aim to provide an overview of the current literature regarding prognostic and predictive molecular factors in patients with SI-NETs.

METHOD

A PubMed search was conducted on (epi)genetic prognostic factors in SI-NETs from 2000 until 2019.

RESULTS

The search yielded 1522 articles of which 20 reviews and 35 original studies were selected for further evaluation. SI-NETs are mutationally quiet tumours with a different genetic make-up compared to pancreatic NETs. Loss of heterozygosity at chromosome 18 is the most frequent genomic aberration (44-100%) followed by mutations of CDKN1B in 8%. Prognostic analyses were performed in 16 studies, of which 8 found a significant (epi)genetic association for survival or progression. Loss of heterozygosity at chromosome 18, gains of chromosome 4, 5, 7, 14 and 20p, copy gain of the SRC gene and low expression of RASSF1A and P16 were associated with poorer survival. In comparison with genetic mutations, epigenetic alterations are significantly more common in SI-NETs and may represent more promising targets in the treatment of SI-NETs.

CONCLUSION

SI-NETs are mutationally silent tumours. No biomarkers have been identified yet that can easily be adopted into current clinical decision making. SI-NETs may represent a heterogeneous disease and larger international studies are warranted to translate molecular findings into precision oncology.

The landscape of molecular alterations in pancreatic and small intestinal neuroendocrine tumours

Gastroenteropancreatic Neuroendocrine Neoplasms (GEP-NENs) arise throughout the gut and feature varying biological behaviour and malignant potential. GEP-NENs include two genetically different entities, well-differentiated neuroendocrine tumours (NETs) and poorly differentiated neuroendocrine carcinomas (NEC). NECs are characterized by a dismal prognosis and by distinctive TP53 and RB1 inactivation which sets them apart from NETs. The latter, conversely, have a wide spectrum of aggressiveness and molecular alterations. Knowledge on their biology has recently expanded thanks to high-throughput studies focused on two important groups of well-differentiated neuroendocrine neoplasms: pancreatic (PanNETs) and small intestinal (SiNETs) tumours. PanNETs have been among the most studied also due to genetic syndromes featuring their onset. Research stemming from this observation has uncovered the inactivation of MEN1, VHL, TSC1/2, and the hyperactivation of the PI3K/mTOR pathway as distinctive biological features of these neoplasms. Next-Generation Sequencing added information on the role of telomere lengthening via ATRX/DAXX inactivation in a fraction of PanNETs, while other display shortened telomeres and recurrent chromosomal alterations. The data so far disclosed a heterogeneous combination of driver events, yet converging into four pathways including DNA damage repair, cell cycle regulation, PI3K/mTOR signalling and telomere maintenance. SiNETs showed a lesser relationship with mutational driver events, even in the case of familial cases. High throughput studies identified putative driver mutations in CDKN1 and APC which, however, were reported in a minor fraction (∼10%) of cases. Tumorigenesis of SiNETs seems to depend more on chromosomal alterations (loss of chromosome 8, gains at 4, 5 and 20) and epigenetic events, which converge to hyperactivate the PI3K/mTOR, MAPK and Wnt pathways. While calling for further integrative studies, these data lay previous and recent findings in a more defined frame and provide clinical research with several candidate markers for patient stratification and companion diagnostics.

Genetics and Epigenetics of Gastroenteropancreatic Neuroendocrine Neoplasms

Gastroenteropancreatic (GEP) neuroendocrine neoplasms (NENs) are heterogeneous regarding site of origin, biological behavior, and malignant potential. There has been a rapid increase in data publication during the last 10 years, mainly driven by high-throughput studies on pancreatic and small intestinal neuroendocrine tumors (NETs). This review summarizes the present knowledge on genetic and epigenetic alterations. We integrated the available information from each compartment to give a pathway-based overview. This provided a summary of the critical alterations sustaining neoplastic cells. It also highlighted similarities and differences across anatomical locations and points that need further investigation. GEP-NENs include well-differentiated NETs and poorly differentiated neuroendocrine carcinomas (NECs). NENs are graded as G1, G2, or G3 based on mitotic count and/or Ki-67 labeling index, NECs are G3 by definition. The distinction between NETs and NECs is also linked to their genetic background, as TP53 and RB1 inactivation in NECs set them apart from NETs. A large number of genetic and epigenetic alterations have been reported. Recurrent changes have been traced back to a reduced number of core pathways, including DNA damage repair, cell cycle regulation, and phosphatidylinositol 3-kinase/mammalian target of rapamycin signaling. In pancreatic tumors, chromatin remodeling/histone methylation and telomere alteration are also affected. However, also owing to the paucity of disease models, further research is necessary to fully integrate and functionalize data on deregulated pathways to recapitulate the large heterogeneity of behaviors displayed by these tumors. This is expected to impact diagnostics, prognostic stratification, and planning of personalized therapy.

Identification of prognostic biomarkers in colorectal cancer using a long non-coding RNA-mediated competitive endogenous RNA network

Colorectal cancer (CRC) is a highly malignant gastrointestinal tumor accompanied by poor prognosis. Long non-coding RNA (lncRNA) plays an important role in the progression and physiology of tumors as it competes with endogenous RNAs, including miRNA and mRNA. In the present study, a multi-step computational method was used to build a CRC-related functional lncRNA-mediated competitive endogenous RNA (ceRNA) network (LMCN). lncRNAs with more degrees and betweenness centrality (BC) were screened out as hub lncRNAs. Then functional enrichment analyses of lncRNAs were carried out from the Gene Ontology (GO) and Reactome pathway databases based on the 'guilt by association' principle. As a result, lncRNAs in the LMCN displayed specific topological characteristics in accordance with the regulatory correlation of coding mRNAs in CRC pathology. HCP5, EPB41L4A-AS1, SNHG12, and LINC00649 were screened out as hub lncRNAs which were more significantly related to the development and prognosis of CRC. The hub lncRNAs in CRC were obviously involved in functions of cell cycle arrest, vacuolar transport, histone modification, and in pathways of GPCR, signaling by Rho GTPases, axon guidance pathways, meaning that they might be potential biomarkers for diagnosis, evaluation and gene-targeted therapy of CRC. Thus, the LMCN construction method could accelerate lncRNA discovery and therapeutic development in CRC.

Class-3 Semaphorins and Their Receptors: Potent Multifunctional Modulators of Tumor Progression

Semaphorins are the products of a large gene family containing 28 genes of which 21 are found in vertebrates. Class-3 semaphorins constitute a subfamily of seven vertebrate semaphorins which differ from the other vertebrate semaphorins in that they are the only secreted semaphorins and are distinguished from other semaphorins by the presence of a basic domain at their C termini. Class-3 semaphorins were initially characterized as axon guidance factors, but have subsequently been found to regulate immune responses, angiogenesis, lymphangiogenesis, and a variety of additional physiological and developmental functions. Most class-3 semaphorins transduce their signals by binding to receptors belonging to the neuropilin family which subsequently associate with receptors of the plexin family to form functional class-3 semaphorin receptors. Recent evidence suggests that class-3 semaphorins also fulfill important regulatory roles in multiple forms of cancer. Several class-3 semaphorins function as endogenous inhibitors of tumor angiogenesis. Others were found to inhibit tumor metastasis by inhibition of tumor lymphangiogenesis, by direct effects on the behavior of tumor cells, or by modulation of immune responses. Notably, some semaphorins such as sema3C and sema3E have also been found to potentiate tumor progression using various mechanisms. This review focuses on the roles of the different class-3 semaphorins in tumor progression.

The Tumor Microenvironment in Neuroendocrine Tumors: Biology and Therapeutic Implications

Neuroendocrine tumors (NETs) include a heterogeneous group of malignancies arising in the diffuse neuroendocrine system and characterized by indolent growth. Complex interactions take place among the cellular components of the microenvironment of these tumors, and the recognition of the molecular mediators of their interplay and cross talk is crucial to discover novel therapeutic targets. NET cells overexpress a plethora of proangiogenic molecules including vascular endothelial growth factor, platelet-derived growth factor, fibroblast growth factor, semaphorins, and angiopoietins that promote both recruitment and proliferation of endothelial cell precursors, thus resulting among the most vascularized cancers with a microvessel density 10-fold higher than epithelial tumors. Also, NETs operate multifaceted interactions with stromal cells, both at local and distant sites, and whether their paracrine secretion of serotonin, connective tissue growth factor, and transforming growth factor β primarily drives the fibroblast activation to enhance the tumor proliferation, on the other side NET-derived profibrotic factors accelerate the extracellular matrix remodeling and contribute to heart valves and/or mesenteric fibrosis development, namely, major complications of functioning NETs. However, at present, little is known on the immune landscape of NETs, but accumulating evidence shows that tumor-infiltrating neutrophils, mast cells, and/or macrophages concur to promote the neoangiogenic switch of these tumors by either direct or indirect mechanisms. On the other hand, immune checkpoint molecules are heterogeneously expressed in NETs' surrounding cells, and it is unclear whether or not tumor-infiltrating lymphocytes are antitumor armed within the microenvironment, given their low mutational load. Here, we review the current knowledge on both gastroenteropancreatic and pulmonary NETs' microenvironment as well as both established and innovative treatments aimed at targeting the tumor-host interplay.

Role of the tumor microenvironment in digestive neuroendocrine tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) represent a group of heterogeneous tumors whose incidence increased over the past few years. Around half of patients already present with metastatic disease at the initial diagnosis. Despite extensive efforts, cytotoxic and targeted therapies have provided only limited efficacy for patients with metastatic GEP-NETs, mainly due to the development of a certain state of resistance. One factor contributing to both the failure of systemic therapies and the emergence of an aggressive tumor phenotype may be the tumor microenvironment (TME), comprising dynamic and adaptative assortment of extracellular matrix components and non-neoplastic cells, which surround the tumor niche. Accumulating evidence shows that the TME can simultaneously support both tumor growth and metastasis and contribute to a certain state of resistance to treatment. In this review, we summarize the current knowledge of the TME of GEP-NETs and discuss the current therapeutic agents that target GEP-NETs and those that could be of interest in the (near) future.

Class 3 semaphorins modulate the invasive capacity of rheumatoid arthritis fibroblast-like synoviocytes

Objective

Class 3 semaphorins regulate diverse cellular processes relevant to the pathology of RA, including immune modulation, angiogenesis, apoptosis and invasive cell migration. Therefore, we analysed the potential role of class 3 semaphorins in the pathology of RA.

Methods

Protein and mRNA expression in RA synovial tissue, SF and fibroblast-like synoviocytes (FLS) were determined by immunoblotting and quantitative PCR (qPCR). RA FLS migration and invasion were determined using wound closure and transwell invasion assays, respectively. PlexinA1, neuropilin-1 and neuropilin-2 expression was knocked down using small interfering RNA (siRNA). Activation of FLS intracellular signalling pathways was assessed by immunoblotting.

Results

mRNA expression of semaphorins (Sema)3B, Sema3C, Sema3F and Sema3G was significantly lower in the synovial tissue of early arthritis patients at baseline who developed persistent disease compared with patients with self-limiting disease after 2 years follow-up. Sema3B and Sema3F expression was significantly lower in arthritis patients fulfilling classification criteria for RA compared with those who did not. FLS expression of Sema3A was induced after stimulation with TNF, IL-1β or lipopolysaccharides (LPS), while Sema3B and Sema3F expression was downregulated. Exogenously applied Sema3A induced the migration and invasive capacity of FLS, while stimulation with Sema3B or Sema3F reduced spontaneous FLS migration, and platelet-derived growth factor induced cell invasion, effects associated with differential regulation of MMP expression and mediated by the PlexinA1 and neuropilin-1 and -2 receptors.

Conclusion

Our data suggest that modulation of class 3 semaphorin signaling could be a novel therapeutic strategy for modulating the invasive behaviour of FLS in RA.

The protective value of miR-204-5p for prognosis and its potential gene network in various malignancies: a comprehensive exploration based on RNA-seq high-throughput data and bioinformatics

Purpose

The prognostic role of miR-204-5p (previous ID: miR-204) is varied and inconclusive in diverse types of malignant neoplasm. Therefore, the purposes of the study comprehensively explore the overall prognostic role of miR-204-5p based on high-throughput microRNA sequencing data, and to investigate the potential role of miR-204-5p via bioinformatics approaches.

Materials and Methods

The data of microRNA sequencing and survival were downloaded from The Cancer Genome Atlas (TCGA), and the prognostic value of miR-204-5p was analyzed by using Kaplan-Meier and univariate cox regressions. Then a meta-analysis was conducted with all TCGA data and relevant studies collected from literature. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated. The prospective molecular mechanism of miR-204-5p was also assessed at a functional level with Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-to-protein interactions (PPI) network.

Results

From TCGA data, the prognostic value of miR-204-5p obviously varied among 20 types of cancers. The pooled HR was 0.928 (95% CI: 0.774-1.113, P = 0.386, 6203 cases of malignancies). For the meta-analysis based on 15 studies from literature, the pooled HR was 0.420 (95% CI: 0.306-0.576, P < 0.001, 1783 cases of malignancies) for overall survival (OS). Furthermore, the combined HR from both TCGA and literature was 0.708 (95% CI: 0.600-0.834, P < 0.001, 7986 cases of malignancies). Subgroup analyses revealed that miR-204-5p could act as a prognostic marker in cancers of respiratory system and digestive system. Functional analysis was conducted on genes predicted as targets (n = 2057) after the overlay genes from six out of twelve software were extracted. Two significant KEGG pathways were enriched (hsa04360: Axon guidance and hsa04722: Neurotrophin signaling pathway). PPI network revealed some hub genes/proteins (CDC42, SOS1, PIK3R1, MAPK1, PLCG1, ESR1, MAPK11, and AR).

Conclusions

The current study demonstrates that over-expression of miR-204-5p could be a protective factor for a certain group of cancers. Clinically, the low miR-204-5p level could gain a predictive value for a poor survival in cancers of respiratory system and digestive system. The detailed molecular mechanisms of miR-204-5p remain to be verified.

Epigenetics of gastroenteropancreatic neuroendocrine tumors: A clinicopathologic perspective

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a heterogeneous group of rare tumors whose site-specific tumor incidence and clinical behavior vary widely. Genetic alterations associated with familial inherited syndromes have been well defined; however, the genetic profile of sporadic tumors is less clear as their tumorigenesis does not appear to be controlled by classic oncogenes such as P53, RB, or KRAS. Even within GEP-NETs, there are no common oncogenic drivers; for example, DAXX/ATRX mutations are strongly implicated in the tumorigenesis of pancreatic but not small bowel NETs. Accordingly, the dysregulation of epigenetic mechanisms has been hypothesized as a potential regulator of GEP-NET tumorigenesis and has become a major focus of recent studies. Despite the heterogeneity of tumor cohorts evaluated in these studies, it is obvious that there are methylation patterns, chromatin remodeling alterations, and microRNA and long non-coding RNA (lncRNA) differential expression profiles that are distinctive of GEP-NETs, some of which are correlated with significant differences in clinical outcomes. Several translational studies have provided convincing data identifying potential prognostic biomarkers, and some of these have demonstrated preliminary success as serum biomarkers that can be used clinically. Nevertheless, there are many opportunities to further define the mechanisms by which these epigenetic modifications influence tumorigenesis, and this will provide better insight into their prognostic and therapeutic utility. Furthermore, these findings form the foundation for future studies evaluating the clinical efficacy of epigenetic modifications as prognostic biomarkers, as well as potential therapeutic targets.