MicroRNA expression profiling of carcinoma in situ cells of the testis

NANOG controls testicular germ cell tumour stemness through regulation of MIR9-2

BACKGROUND

Testicular germ cell tumours (TGCTs) represent a clinical challenge; they are most prevalent in young individuals and are triggered by molecular mechanisms that are not fully understood. The origin of TGCTs can be traced back to primordial germ cells that fail to mature during embryonic development. These cells express high levels of pluripotency factors, including the transcription factor NANOG which is highly expressed in TGCTs. Gain or amplification of the NANOG locus is common in advanced tumours, suggesting a key role for this master regulator of pluripotency in TGCT stemness and malignancy.

METHODS

In this study, we analysed the expression of microRNAs (miRNAs) that are regulated by NANOG in TGCTs via integrated bioinformatic analyses of data from The Cancer Genome Atlas and NANOG chromatin immunoprecipitation in human embryonic stem cells. Through gain-of-function experiments, MIR9-2 was further investigated as a novel tumour suppressor regulated by NANOG. After transfection with MIR9-2 mimics, TGCT cells were analysed for cell proliferation, invasion, sensitivity to cisplatin, and gene expression signatures by RNA sequencing.

RESULTS

For the first time, we identified 86 miRNAs regulated by NANOG in TGCTs. Among these, 37 miRNAs were differentially expressed in NANOG-high tumours, and they clustered TGCTs according to their subtypes. Binding of NANOG within 2 kb upstream of the MIR9-2 locus was associated with a negative regulation. Low expression of MIR9-2 was associated with tumour progression and MIR9-2-5p was found to play a role in the control of tumour stemness. A gain of function of MIR9-2-5p was associated with reduced proliferation, invasion, and sensitivity to cisplatin in both embryonal carcinoma and seminoma tumours. MIR9-2-5p expression in TGCT cells significantly reduced the expression of genes regulating pluripotency and cell division, consistent with its functional effect on reducing cancer stemness.

CONCLUSIONS

This study provides new molecular insights into the role of NANOG as a key determinant of pluripotency in TGCTs through the regulation of MIR9-2-5p, a novel epigenetic modulator of cancer stemness. Our data also highlight the potential negative feedback mediated by MIR9-2-5p on NANOG expression, which could be exploited as a therapeutic strategy for the treatment of TGCTs.

Testicular germ cell tumour cells release microRNA-containing extracellular vesicles that induce phenotypic and genotypic changes in cells of the tumour microenvironment

Malignant germ-cell-tumours (GCTs) are characterised by microRNA (miRNA/miR-) dysregulation, with universal over-expression of miR-371~373 and miR-302/367 clusters regardless of patient age, tumour site, or subtype (seminoma/yolk-sac-tumour/embryonal carcinoma). These miRNAs are released into the bloodstream, presumed within extracellular-vesicles (EVs) and represent promising biomarkers. Here, we comprehensively examined the role of EVs, and their miRNA cargo, on (fibroblast/endothelial/macrophage) cells representative of the testicular GCT (TGCT) tumour microenvironment (TME). Small RNA next-generation-sequencing was performed on 34 samples, comprising representative malignant GCT cell lines/EVs and controls (testis fibroblast [Hs1.Tes] cell-line/EVs and testis/ovary samples). TME cells received TGCT co-culture, TGCT-derived EVs, and a miRNA overexpression system (miR-371a-OE) to assess functional relevance. TGCT cells secreted EVs into culture media. MiR-371~373 and miR-302/367 cluster miRNAs were overexpressed in all TGCT cells/subtypes compared with control cells and were highly abundant in TGCT-derived EVs, with miR-371a-3p/miR-371a-5p the most abundant. TGCT co-culture resulted in increased levels of miRNAs from the miR-371~373 and miR-302/367 clusters in TME (fibroblast) cells. Next, fluorescent labelling demonstrated TGCT-derived EVs were internalised by all TME (fibroblast/endothelial/macrophage) cells. TME (fibroblast/endothelial) cell treatment with EVs derived from different TGCT subtypes resulted in increased miR-371~373 and miR-302/367 miRNA levels, and other generic (eg, miR-205-5p/miR-148-3p) and subtype-specific (seminoma, eg, miR-203a-3p; yolk-sac-tumour, eg, miR-375-3p) miRNAs. MiR-371a-OE in TME cells resulted in increased collagen contraction (fibroblasts) and angiogenesis (endothelial cells), via direct mRNA downregulation and alteration of relevant pathways. TGCT cells communicate with nontumour stromal TME cells through release of EVs enriched in oncogenic miRNAs, potentially contributing to tumour progression.

The Role of miRNA in Testicular Cancer: Current Insights and Future Perspectives

Background and Objectives: Despite advancements in the diagnosis and treatment of testicular germ cell tumours (TGTCs), challenges persist in identifying reliable biomarkers for early detection and precise disease management. This narrative review addresses the role of microRNAs (miRNAs) as potential diagnostic tools and therapeutic targets in the treatment of TGCTs. Materials and Methods: Three databases (PubMed®, Web of Science™, and Scopus®) were queried for studies investigating the utility of miRNA as diagnostic tools, assessing their prognostic significance, and evaluating their potential to guide TGCT treatment. Different combinations of the following keywords were used, according to a free-text protocol: "miRNA", "non-coding RNA", "small RNA", "Testicular Cancer", "seminomatous testicular germ cell", "non-seminomatous testicular germ cell". Results: The potential of miRNAs as possible biomarkers for a non-invasive diagnosis of TGCT is appealing. Their integration into the diagnostic pathway for TGCT patients holds the potential to enhance the discriminative power of conventional serum tumour markers (STMs) and could expedite early diagnosis, given that miRNA overexpression was observed in 50% of GCNIS cases. Among miRNAs, miR-371a-3p stands out with the most promising evidence, suggesting its relevance in the primary diagnosis of TGCT, particularly when conventional STMs offer limited value. Indeed, it demonstrated high specificity (90-99%) and sensitivity (84-89%), with good positive predictive value (97.2%) and negative predictive value (82.7%). Furthermore, a direct relationship between miRNA concentration, disease burden, and treatment response exists, regardless of disease stages. The initial evidence of miRNA decrease in response to surgical treatment and systemic chemotherapy has been further supported by more recent results suggesting the potential utility of this tool not only in evaluating treatment response but also in monitoring residual disease and predicting disease relapse. Conclusions: MiRNAs could represent a reliable tool for accurate diagnosis and disease monitoring in the treatment of TGCT, providing more precise tools for early detection and treatment stratification. Nevertheless, well-designed clinical trials and comprehensive long-term data are needed to ensure their translation into effective clinical tools.

Molecular Characterization of Patients with Cryptorchidism: Preliminary Search for an Expression Profile Related to That of Testicular Germ-Cell Tumors

Cryptorchidism (CO) is a risk factor for the development of testicular germ-cell tumors (TGCT). This is supported by reports showing the persistence of gonocytes in CO patients. These cells are proposed to be related to the development of germ-cell neoplasia in situ (GCNIS), which is considered the precursor stage/lesion of TGCT. Therefore, it is proposed that some patients with CO could express some molecular markers related to TGCT. In this study, we analyzed testicular tissue samples from CO, TGCT, and controls. We determined the expression of POU5F1, PLAP, and KIT by immunohistochemistry and that of the hsa-miR-371-373 cluster, hsa-miR-367, and LATS2, PTEN, and IGFR1 genes by RT-qPCR. We then carried out a bioinformatic analysis to identify other possible candidate genes as tumor biomarkers. We found that 16.7% (2/12) of the CO patients presented increased expression of POU5F1, KIT, PLAP, hsa-miR-371-373, and hsa-miR-367 and decreased expression of LATS2 and IGF1R. Finally, the genes ARID4B, GALNT3, and KPNA6 were identified as other possible candidate tumor biomarkers. This is the first report describing the expression of the hsa-miR-371-373 cluster, hsa-miR-367, LATS2, and IGF1R in the testicular tissues of two CO patients with cells immune-positive to POU5F1, PLAP, and KIT, which is similar to what is observed in TGCT.

The Role of microRNAs in the Gonocyte Theory as Target of Malignancy: Looking for Potential Diagnostic Biomarkers

Some pediatric patients with cryptorchidism preserve cells with gonocyte characteristics beyond their differentiation period, which could support the theory of the gonocyte as a target for malignancy in the development of testicular neoplasia. One of the key molecules in gonocyte malignancy is represented by microRNAs (miRNAs). The goal of this review is to give an overview of miRNAs, a class of small non-coding RNAs that participate in the regulation of gene expression. We also aim to review the crucial role of several miRNAs that have been further described in the regulation of gonocyte differentiation to spermatogonia, which, when transformed, could give rise to germ cell neoplasia in situ, a precursor lesion to testicular germ cell tumors. Finally, the potential use of miRNAs as diagnostic and prognostic biomarkers in testicular neoplasia is addressed, due to their specificity and sensitivity compared to conventional markers, as well as their applications in therapeutics.

Examples of Inverse Comorbidity between Cancer and Neurodegenerative Diseases: A Possible Role for Noncoding RNA

Cancer is one of the most common causes of death; in parallel, the incidence and prevalence of central nervous system diseases are equally high. Among neurodegenerative diseases, Alzheimer’s dementia is the most common, while Parkinson’s disease (PD) is the second most frequent neurodegenerative disease. There is a significant amount of evidence on the complex biological connection between cancer and neurodegeneration. Noncoding RNAs (ncRNAs) are defined as transcribed nucleotides that perform a variety of regulatory functions. The mechanisms by which ncRNAs exert their functions are numerous and involve every aspect of cellular life. The same ncRNA can act in multiple ways, leading to different outcomes; in fact, a single ncRNA can participate in the pathogenesis of more than one disease—even if these seem very different, as cancer and neurodegenerative disorders are. The ncRNA activates specific pathways leading to one or the other clinical phenotype, sometimes with obvious mechanisms of inverse comorbidity. We aimed to collect from the existing literature examples of inverse comorbidity in which ncRNAs seem to play a key role. We also investigated the example of mir-519a-3p, and one of its target genes Poly (ADP-ribose) polymerase 1, for the inverse comorbidity mechanism between some cancers and PD. We believe it is very important to study the inverse comorbidity relationship between cancer and neurodegenerative diseases because it will help us to better assess these two major areas of human disease.

Epigenetic Regulation during Primordial Germ Cell Development and Differentiation

Germline development varies significantly across metazoans. However, mammalian primordial germ cell (PGC) development has key conserved landmarks, including a critical period of epigenetic reprogramming that precedes sex-specific differentiation and gametogenesis. Epigenetic alterations in the germline are of unique importance due to their potential to impact the next generation. Therefore, regulation of, and by, the non-coding genome is of utmost importance during these epigenomic events. Here, we detail the key chromatin changes that occur during mammalian PGC development and how these interact with the expression of non-coding RNAs alongside broader epitranscriptomic changes. We identify gaps in our current knowledge, in particular regarding epigenetic regulation in the human germline, and we highlight important areas of future research.

Improving outcomes in germ cell cancers using miRNA

Owing to advances in treatment paradigms across the last five decades, testicular cancer is now eminently curable. However, current serum tumour and imaging biomarkers lack adequate sensitivity, specificity, and predictive value. Subsequently, their utility in detecting active malignancy and informing treatment decisions is minimal in a large proportion of men with testicular cancer. Micro-ribonucleic acids (miRNA), pertinently miR-371a-3p, offer a new tool, which based on early data, appears to fill many of the gaps that existing biomarkers leave. This paper reviews the evolution of the technology, potential limitations, and discusses the clinical relevance of miRNA as it moves towards the clinic.

Circulating MicroRNAs, the Next-Generation Serum Biomarkers in Testicular Germ Cell Tumours: A Systematic Review

CONTEXT

Clinical management of testicular germ cell tumours (GCTs) is hampered by low sensitivity and specificity of the biomarkers currently in use. Circulating microRNAs (miRs) might offer the potential to address areas of unmet clinical need.

OBJECTIVE

To systematically evaluate the evidence for clinical applications of serum levels of miR302/367 and miR371-3 in adult testicular GCTs in terms of primary diagnosis, various clinical scenarios, and the costs of clinical implementation.

EVIDENCE ACQUISITION

We performed a critical review of PubMed/Medline, Embase and the Cochrane Library in January 2021 in accordance with Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement.

EVIDENCE SYNTHESIS

Thirty-one manuscripts addressed miR performance and potential clinical use in testicular GCT. Of these, 23 evaluated the utility in primary diagnosis, seven in early-stage disease, and 13 in metastatic disease, and two addressed the costs of clinical implementation. Of the various miRs studied, miR-371a-3p appears the most useful and potentially the only one that needs to be assayed, with an area under the receiver operating characteristic curve >0.90, sensitivity of 89-96%, and specificity of >90% for both seminoma and nonseminoma, surpassing the classic serum tumour markers. The miRs studied to date are not elevated in cases with teratoma only. Levels of miR-371a-3p correlate with primary tumour mass, clinical stage, and International Germ Cell Cancer Collaborative Group risk groups. Serial measurements mirror treatment efficacy in all clinical stages.

CONCLUSIONS

Circulating miRNA levels, particularly of miR-371a-3p, have potential for incorporation in clinical practice and may aid in clinical decision-making in various clinical scenarios in GCT.

PATIENT SUMMARY

We analysed the current evidence on the usefulness of blood levels of molecules called microRNAs in the management of testicular tumours. The microRNA-371a-3p molecule has better sensitivity and specificity than the markers currently being measured. This new biomarker may soon have a place in clinical practice.

[Diagnostic markers in urology]

Cancer diagnostics can be supplemented by disease-related biomarkers. In the course of modern patient-tailored cancer treatment, the importance of correct risk stratification, prognosis and monitoring has significantly increased. In recent years, a multitude of biomarkers and related test procedures have emerged to fulfil this purpose. The following review article summarizes the most recent developments with respect to the use of biomarkers in the diagnostics of urological cancers.

Next-generation sequencing analysis reveals segmental patterns of microRNA expression in yak epididymis

MicroRNAs (miRNAs) have emerged as potent regulators of gene expression and are widely expressed in biological systems. In reproduction, they have been shown to have a significant role in the acquisition and maintenance of male fertility, whereby deletion of Dicer in mouse germ cells leads to infertility. Evidence indicates that this role of miRNAs extends from the testis into the epididymis, controlling gene expression and contributing to regional variations in gene expression. In this study, RNA sequencing technology was used to investigate miRNA expression patterns in the yak epididymis. Region-specific miRNA expression was found in the yak epididymis. In all, 683 differentially expressed known miRNAs were obtained; 190, 186 and 307 differentially expressed miRNAs were identified for caput versus corpus, corpus versus cauda and caput versus cauda region pairs respectively. Kyoto Encyclopedia of Genes and Genomes results showed endocytosis as the most enriched pathway across region pairs, followed by protein processing in the endoplasmic reticulum, phagosome, spliceosome and biosynthesis of amino acids in region pair-specific hierarchical order. Gene ontology results showed varied enrichment in terms including cell, biogenesis, localisation, binding and locomotion across region pairs. In addition, significantly higher miR-34c expression was seen in the yak caput epididymidis relative to the corpus and cauda epididymidis.

High-throughput sequencing reveals differential expression of miRNAs in yak and cattleyak epididymis

Cattleyaks (CY) are interspecific hybrids between cattle (Bos taurus) and yak (Bos gruniens, YK) exhibiting the same prominent adaptability and higher performances than YK. MiRNAs have played an important role in the acquisition and maintenance of male fertility in reproduction, where deletion of Dicer in mice germ cells results in infertility. According to a body of evidence, the function of miRNA in the male reproductive system extends from the testis into the epididymis and, as such, regulates gene expression and contributes to regional gene expression variations. Using RNA sequencing on biological replicates, we described differentially expressed miRNAs profiles for tissue from epididymis of YK and CY. In the present study, High-throughput sequencing analysis showed that 55 differentially expressed (DE) miRNAs were identified in the epididymis of YK and CY. Among these, 43 DE miRNAs were upregulated while the remaining 12 DE miRNAs were downregulated between epididymis of YK and CY. Our results showed that the top most important DE miRNAs, bta-miR-449c, bta-miR-539, bta-miR-136, bta-miR-504, bta-miR-31 and bta-miR-222 were found to be involved in the reproductive system of CY. In addition, some targeted genes, Clusterins (CLU), Retinoic Acid Receptor a (RARa) and Hydroxy acyl glutathione Hydrolase (HAGH) and HSPH1 targeted by bta-miR-2411-3p and bta-miR-1298 were involved in the sperm motility, sperm morphology and post-testicular sperm maturation. Furthermore, GO and KEGG analyses were performed to classify the functions of target genes for DE miRNAs. In addition, RT-qPCR validation of the DE miRNAs and its targeted genes revealed that putative miRNAs are involved in the male CY infertility by altering the gene expression. Present findings may not only increase our understanding of the molecular mechanisms regulated by the miRNAs in epididymis, but also provide a valuable information to understand the male infertility mechanism of CY.

Liquid Biopsies in the Clinical Management of Germ Cell Tumor Patients: State-of-the-Art and Future Directions

Liquid biopsies constitute a minimally invasive means of managing cancer patients, entailing early diagnosis, follow-up and prediction of response to therapy. Their use in the germ cell tumor field is invaluable since diagnostic tissue biopsies (which are invasive) are often not performed, and therefore only a presumptive diagnosis can be made, confirmed upon examination of the surgical specimen. Herein, we provide an overall review of the current liquid biopsy-based biomarkers of this disease, including the classical, routinely used serum tumor markers—the promising microRNAs rapidly approaching the introduction into clinical practice—but also cell-free DNA markers (including DNA methylation) and circulating tumor cells. Finally, and importantly, we also explore novel strategies and challenges for liquid biopsy markers and methodologies, providing a critical view of the future directions for liquid biopsy tests in this field, highlighting gaps and unanswered questions.

Comparative rna-seq analysis of region-specific miRNA expression in the epididymis of cattleyak

The epididymis is the site of post-testicular sperm maturation, which constitutes the acquisition of sperm motility and the ability to recognize and fertilize oocytes. The role of miRNA in male reproductive system, including the control of different steps leading to proper fertilization such as gametogenesis, sperm maturation and maintenance of male fertility where the deletion of Dicer in mouse germ cells led to infertility, has been demonstrated. The identification of miRNA expression in a region-specific manner will therefore provide valuable insight into the functional differences between the regions of the epididymis. In this study, we employed RNA-seq technology to explore the expression pattern of miRNAs and establish some miRNAs of significant interest with regard to epididymal sperm maturation in the CY epididymis. We identified a total of 431 DE known miRNAs; 119, 185 and 127 DE miRNAs were detected for caput versus corpus, corpus versus cauda and caput versus cauda region pairs, respectively. Our results demonstrate region-specific miRNA expression in the CY epididymis. The GO and KEGG enrichment for the predicted target genes indicated the functional values of miRNAs. Furthermore, we observed that the expression of miR-200a was downregulated in the caput, compared with cauda. Since the family of miR-200 has previously been suggested to contribute to the distinct physiological function of sperm maturation in epididymis of adult rat, we speculate that the downregulation of miR-200a in CY caput epididymis may play an important role of sperm maturation in the epididymis of CY. Therefore, our findings may not only increase our understanding of the molecular mechanisms regulated by the miRNA functions in region-specific miRNA expression in the CY epididymis, it could provide a valuable information to understand the mechanism of male infertility of CY.

The metastatic potential of seminomatous germ cell tumours is associated with a specific microRNA pattern

BACKGROUND

Seminomatous germ cell tumours (SGCT) are the most frequent malignancy in young men. Reliable prognostic biomarkers for the prediction of metastasis at diagnosis and the risk of relapse in clinical stage I (CSI) are lacking. Adjuvant therapies carry a risk of overtreatment, whereas salvage therapies have a risk of high toxicities. Thus, the identification of reliable prognostic biomarkers is highly desirable to identify patients who will benefit from early adjuvant treatment. MicroRNAs (miRNAs) regulate tumour development and progression, and their potential as biomarkers has already been proven in a variety of malignancies.

OBJECTIVES

The aim of our study was to define a specific miRNA expression pattern that discriminates metastatic from non-metastatic primary SGCT.

MATERIALS AND METHODS

Total RNA was isolated from 24 formalin-fixed paraffin-embedded (FFPE) primary SGCT tumours (10 non-metastatic, five metachronously and nine synchronously metastatic) and from 10 normal testicular tissue samples. Microarray analysis was performed for global miRNA expression profiling. The results were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Statistical analysis was performed using SPSS.

RESULTS

Microarray analyses revealed a specific miRNA pattern that distinguishes metastatic from non-metastatic SGCT. Sixty-three miRNAs were differentially expressed in metastatic compared to non-metastatic tumours (P < .01). Microarray results were confirmed by qRT-PCR for three out of five selected miRNAs (miR-29c-5p, miR-506-3p and miR-371a-5p; P < .05). All five miRNAs (miR-29c-5p, miR-506-3p, miR-1307-5p, miR-371a-5p and miR-371a-3p) showed differential expression between tumour and normal tissues (P < .05).

CONCLUSION

Metastatic primary SGCTs are characterized by a specific miRNA expression pattern. Therefore, specific miRNAs could represent a new tool to predict the metastatic potential in SGCT patients.

Graded expression of microRNA-371a-3p in tumor tissues, contralateral testes, and in serum of patients with testicular germ cell tumor

Background: Serum levels of microRNA-371a-3p represent a specific tumor marker of testicular germ cell tumors (GCTs) but the origin of circulating miR-371a-3p is not finally resolved. The correlation between miR-levels in tissue and serum is unclear.

Results: MiR-levels in GCT tissue are 399-fold higher than in contralateral testicular tissue and 5843-fold higher than in non-testicular tissue. MiR tissue levels correlate with corresponding serum levels (r² = 0.181). ISH detected miR-371a-3p intracellularly in GCT cells except teratoma. A low expression was also detected in normal testicular germ cells.

Conclusions: Circulating miR-371a-3p is specifically derived from GCT tissue. The miR is present in GCT cells except teratoma. A low expression is also found in normal testicular tissue but not in non-testicular tissue. MiR-371a-3p levels in tissue and serum correlate significantly. This study underscores the usefulness of serum miR-371a-3p as tumor marker of GCT.

Patients and methods: Expression levels of miR-371a-3p were concurrently measured in tissues of GCT, contralateral testes (n = 38), and in serum (n = 36) with real time PCR. For control, 5 healthy testicles and 4 non-testicular tissue samples were examined. MiR-levels were compared using descriptive statistical methods. We also performed in situ hybridization (ISH) of GCT tissue with a probe specific for miR-371a-3p.

Application of miRNAs in the diagnosis and monitoring of testicular germ cell tumours

Testicular germ cell tumours (TGCTs) are the most frequent cancer type in young men and originate from the common precursor germ cell neoplasia in situ (GCNIS). For decades, clinical management of patients with TGCT has relied on classic serum tumour markers: α-fetoprotein, human chorionic gonadotropin subunit-β and lactate dehydrogenase. In the past 10 years, microRNAs have been shown to outperform classic serum tumour markers in the diagnosis of primary tumours and in follow-up monitoring and prediction of relapse. miR-371a-3p is the most consistent marker and exhibits >90% diagnostic sensitivity and specificity in TGCT. However, miR-371a-3p cannot be used to diagnose GCNIS or mature teratoma. Future efforts must technically standardize the microRNA-based methods internationally and introduce miR-371a-3p as a molecular liquid biopsy-based marker for TGCTs in the clinic.

Predicting Gonadal Germ Cell Cancer in People with Disorders of Sex Development; Insights from Developmental Biology

The risk of gonadal germ cell cancer (GGCC) is increased in selective subgroups, amongst others, defined patients with disorders of sex development (DSD). The increased risk is due to the presence of part of the Y chromosome, i.e., GonadoBlastoma on Y chromosome GBY region, as well as anatomical localization and degree of testicularization and maturation of the gonad. The latter specifically relates to the germ cells present being at risk when blocked in an embryonic stage of development. GGCC originates from either germ cell neoplasia in situ (testicular environment) or gonadoblastoma (ovarian-like environment). These precursors are characterized by presence of the markers OCT3/4 (POU5F1), SOX17, NANOG, as well as TSPY, and cKIT and its ligand KITLG. One of the aims is to stratify individuals with an increased risk based on other parameters than histological investigation of a gonadal biopsy. These might include evaluation of defined susceptibility alleles, as identified by Genome Wide Association Studies, and detailed evaluation of the molecular mechanism underlying the DSD in the individual patient, combined with DNA, mRNA, and microRNA profiling of liquid biopsies. This review will discuss the current opportunities as well as limitations of available knowledge in the context of predicting the risk of GGCC in individual patients.

Cluster miRNAs and cancer: Diagnostic, prognostic and therapeutic opportunities

MiRNAs are class of noncoding RNA important for gene expression regulation in many plants, animals and viruses. MiRNA clusters contain a set of two or more miRNA encoding genes, transcribed together as polycistronic miRNAs. Currently, there are approximately 159 miRNA clusters reported in the human genome consisting of miRNAs ranging from two or more miRNA genes. A large proportion of clustered miRNAs resides in and around the fragile sites or cancer associated genomic hotspots and plays an important role in carcinogenesis. Altered expression of miRNA cluster can be pro-tumorigenic or anti-tumorigenic and can be targeted for clinical management of cancer. Over the past few years, manipulation of miRNA clusters expression is attempted for experimental purpose as well as for diagnostic, prognostic and therapeutic applications in cancer. Re-expression of miRNAs by epigenetic therapy, genome editing such as clustered regulatory interspaced short palindromic repeats (CRISPR) and miRNA mowers showed promising results in cancer therapy. In this review, we focused on the potential of miRNA clusters as a biomarker for diagnosis, prognosis, targeted therapy as well as strategies for modulating their expression in a therapeutic context. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Processing > Processing of Small RNAs RNA in Disease and Development > RNA in Disease Regulatory RNAs/RNAi/Riboswitches > Biogenesis of Effector Small RNAs.

Different Clinical Presentations and Management in Complete Androgen Insensitivity Syndrome (CAIS)

Complete androgen insensitivity syndrome (CAIS) is an X-linked recessive genetic disorder resulting from maternally inherited or de novo mutations involving the androgen receptor gene, situated in the Xq11-q12 region. The diagnosis is based on the presence of female external genitalia in a 46, XY human individual, with normally developed but undescended testes and complete unresponsiveness of target tissues to androgens. Subsequently, pelvic ultrasound or magnetic resonance imaging (MRI) could be helpful in confirming the absence of Mullerian structures, revealing the presence of a blind-ending vagina and identifying testes. CAIS management still represents a unique challenge throughout childhood and adolescence, particularly regarding timing of gonadectomy, type of hormonal therapy, and psychological concerns. Indeed this condition is associated with an increased risk of testicular germ cell tumour (TGCT), although TGCT results less frequently than in other disorders of sex development (DSD). Furthermore, the majority of detected tumoral lesions are non-invasive and with a low probability of progression into aggressive forms. Therefore, histological, epidemiological, and prognostic features of testicular cancer in CAIS allow postponing of the gonadectomy until after pubertal age in order to guarantee the initial spontaneous pubertal development and avoid the necessity of hormonal replacement therapy (HRT) induction. However, HRT is necessary after gonadectomy in order to prevent symptoms of hypoestrogenism and to maintain secondary sexual features. This article presents differential clinical presentations and management in patients with CAIS to emphasize the continued importance of standardizing the clinical and surgical approach to this disorder.

Distinct Metabolic Features of Seminoma and Embryonal Carcinoma Revealed by Combined Transcriptome and Metabolome Analyses

Seminoma and embryonal carcinoma (EC), two typical types of testicular germ cell tumors (TGCTs), present significant differences in growth behavior, expression characteristics, differentiation potential, clinical features, therapy, and prognosis. The purpose of this study was to compare the distinctive or preference metabolic pathways between seminoma and EC. The Cancer Genome Atlas revealed that many genes encoding metabolic enzymes could distinguish between seminoma and EC. Using well-characterized cell line models for seminoma (Tcam-2 cells) and EC (NT2 cells), we characterized their metabolite profiles using ultraperformance liquid chromatography coupled to Q-TOF mass spectrometry (UPLC/Q-TOF MS). In general, the integrated results from transcriptome and metabolite profiling revealed that seminoma and EC exhibited distinctive characteristics in the metabolisms of amino acids, glucose, fatty acids, sphingolipids, nucleotides, and drugs. Notably, an attenuation of citric acid cycle/mitochondrial oxidative phosphorylation and sphingolipid biosynthesis as well as an increase in arachidonic acid metabolism and (very) long-chain fatty acid abundance occurred in seminoma as compared with EC. Our study suggests histologic subtype-dependent metabolic reprogramming in TGCTs and will lead to a better understanding of the metabolic signatures and biology of TGCT subtypes.

Cellular origin of microRNA-371a-3p in healthy males based on systematic urogenital tract tissue evaluation

BACKGROUND

The microRNA-371a-3p (miR-371a-3p) has been reported to be an informative liquid biopsy (serum and plasma) molecular biomarker for both diagnosis and follow-up of patients with a malignant (testicular) germ cell tumor ((T)GCT). It is expressed in all histological cancer elements, with the exception of mature teratoma. However, normal testis, semen, and serum of males with a disrupted testicular integrity without a TGCT may contain miR-371a-3p levels above threshold, of which the cellular origin is unknown.

OBJECTIVES

Therefore, a series of relevant tissues (frozen and formalin-fixed paraffin-embedded (FFPE), when available) from the complete male urogenital tract (i.e., kidney to urethra and testis to urethra) and semen was investigated for miR-371a-3p levels using targeted quantitative RT-PCR (qRT-PCR).

MATERIALS AND METHODS

In total, semen of males with normospermia (n = 11) and oligospermia (n = 3) was investigated, as well as 88 samples derived from 32 different patients. The samples represented one set of tissues related to the entire male urogenital tract (11 anatomical locations), three sets for 10 locations, and four sets for six locations.

RESULTS

All testis parenchyma (n = 17) cases showed low miR-371a-3p levels. Eight out of 14 (57%) semen samples showed detectable miR-371a-3p levels, irrespective of the amount of motile spermatozoa, but related to sperm concentration and matched Johnsen score (Spearman's rho correlation coefficient 0.849 and 0.871, p = 0.000, respectively). In all other tissues investigated, miR-371a-3p could not be detected.

DISCUSSION

This study demonstrates that the miR-371a-3p in healthy adult males is solely derived from the germ cell compartment.

CONCLUSIONS

The observation is important in the context of applying miR-371a-3p as molecular liquid biopsy biomarker for diagnosis and follow-up of patients with malignant (T)GCT. Moreover, miR-371a-3p might be an informative seminal biomarker for testicular germ cell composition.

Human Germ Cell Tumors are Developmental Cancers: Impact of Epigenetics on Pathobiology and Clinic

Current (high throughput omics-based) data support the model that human (malignant) germ cell tumors are not initiated by somatic mutations, but, instead through a defined locked epigenetic status, representative of their cell of origin. This elegantly explains the role of both genetic susceptibility as well as environmental factors in the pathogenesis, referred to as 'genvironment'. Moreover, it could also explain various epidemiological findings, including the rising incidence of this type of cancer in Western societies. In addition, it allows for identification of clinically relevant and informative biomarkers both for diagnosis and follow-up of individual patients. The current status of these findings will be discussed, including the use of high throughput DNA methylation profiling for determination of differentially methylated regions (DMRs) as well as chromosomal copy number variation (CNV). Finally, the potential value of methylation-specific tumor DNA fragments (i.e., XIST promotor) as well as embryonic microRNAs as molecular biomarkers for cancer detection in liquid biopsies will be presented.

Clinical utility of plasma miR-371a-3p in germ cell tumors

Germ cell tumours predominantly of the testis ((T)GCTs) are remarkably chemotherapy sensitive. However, a small proportion of patients fail to be cured with cisplatin-based combination chemotherapy. miR-371a-3p is a new liquid biopsy biomarker for (T)GCTs. The aim of this study was to evaluate clinical utility of plasma miR-371a-3p level in patients starting systemic chemotherapy. Patients were included before the first cycle (N = 180) and second cycle (N = 101) of systemic first line chemotherapy, treated between July 2010 and May 2017. Plasma miR-371a-3p levels were measured with the ampTSmiR test and compared to disease characteristics and outcome. Pretreatment plasma miR-371a-3p levels were increased in 51.7% of cases and associated with number of metastatic sites, presence of lung, retroperitoneal, and mediastinal lymph node metastases, S - stage, IGCCCG risk group, and response to therapy. Patients with a negative pretreatment plasma level had better progression-free survival (PFS) and overall survival (OS) compared to patients being positive for miR-371a-3p (hazard ratio [HR] = 0.26, 95% confidence interval [CI] 0.09-0.71, P = 0.02 for PFS and HR = 0.21, 95% CI 0.07-0.67, P = 0.03 for OS, respectively). Patients negative for miR-371a-3p in both samples had a superior PFS (HR = 0.10, 95% CI 0.01-21.49, P = 0.02) and OS (HR = 0.08, 95% CI 0.01-27.81, P = 0.008) compared to patients with miR-371a-3p positive in both samples (multivariate analyses were non-significant). In total 68% of the patients were S0. This study demonstrates clinical value of plasma miR-371a-3p level in chemotherapy naïve (T)GCT patients starting first line of chemotherapy to predict prognosis.

Testicular cancer

Testicular cancer is the most common malignancy among men between 14 and 44 years of age, and its incidence has risen over the past two decades in Western countries. Both genetic and environmental factors contribute to the development of testicular cancer, for which cryptorchidism is the most common risk factor. Progress has been made in our understanding of the disease since the initial description of carcinoma in situ of the testis in 1972 (now referred to as germ cell neoplasia in situ), which has led to improved treatment options. The combination of surgery and cisplatin-based chemotherapy has resulted in a cure rate of >90% in patients with testicular cancer, although some patients become refractory to chemotherapy or have a late relapse; an improved understanding of the molecular determinants underlying tumour sensitivity and resistance may lead to the development of novel therapies for these patients. This Primer provides an overview of the biology, epidemiology, diagnosis and current treatment guidelines for testicular cancer, with a focus on germ cell tumours. We also outline areas for future research and what to expect in the next decade for testicular cancer.

Elucidating human male germ cell development by studying germ cell cancer

Human germ cell development is regulated in a spatio-temporal manner by complex regulatory networks. Here, we summarize results obtained in germ cell tumors and respective cell lines and try to pinpoint similarities to normal germ cell development. This comparison allows speculating about the critical and error-prone mechanisms, which when disturbed, lead to the development of germ cell tumors. Short after specification, primordial germ cells express markers of pluripotency, which, in humans, persists up to the stage of fetal/infantile spermatogonia. Aside from the rare spermatocytic tumors, virtually all seminomas and embryonal carcinomas express markers of pluripotency and show signs of pluripotency or totipotency. Therefore, it appears that proper handling of the pluripotency program appears to be the most critical step in germ cell development in terms of tumor biology. Furthermore, data from mice reveal that germline cells display an epigenetic signature, which is highly similar to pluripotent cells. This signature (poised histone code, DNA hypomethylation) is required for the rapid induction of toti- and pluripotency upon fertilization. We propose that adult spermatogonial cells, when exposed to endocrine disruptors or epigenetic active substances, are prone to reinitiate the pluripotency program, giving rise to a germ cell tumor. The fact that pluripotent cells can be derived from adult murine and human testicular cells further corroborates this idea.

Testicular cancer from diagnosis to epigenetic factors

Testicular cancer (TC) is one of the most common neoplasms that occurs in male and includes germ cell tumors (GCT), sex cord-gonadal stromal tumors and secondary testicular tumors. Diagnosis of TC involves the evaluation of serum tumor markers alpha-fetoprotein, human chorionic gonadotropin and lactate dehydrogenase, but clinically several types of immunohistochemical markers are more useful and more sensitive in GCT, but not in teratoma. These new biomarkers are genes expressed in primordial germ cells/gonocytes and embryonic pluripotency-related cells but not in normal adult germ cells and they include PLAP, OCT3/4 (POU5F1), NANOG, SOX2, REX1, AP-2γ (TFAP2C) and LIN28. Gene expression in GCT is regulated, at least in part, by DNA and histone modifications, and the epigenetic profile of these tumours is characterised by genome-wide demethylation. There are different epigenetic modifications in TG-subtypes that reflect the normal developmental switch in primordial germ cells from an under- to normally methylated genome. The main purpose of this review is to illustrate the findings of recent investigations in the classification of male genital organs, the discoveries in the use of prognostic and diagnostic markers and the epigenetic aberrations mainly affecting the patterns of DNA methylation/histone modifications of genes (especially tumor suppressors) and microRNAs (miRNAs).

Can germ cell neoplasia in situ be diagnosed by measuring serum levels of microRNA371a-3p?

Purpose

Diagnosing germ cell neoplasia in situ (GCNis) can detect germ cell tumours (GCTs) at the pre-invasive stage. To date, testicular biopsy with the potential of surgical complications is the only way of safely diagnosing GCNis. Recently, microRNAs (miRs) 371-3, and miR 367 were shown to be valuable serum biomarkers of GCTs. We explored the usefulness of these candidate miRs as a marker for GCNis.

Methods

27 patients with GCNis and no concomitant GCT were enrolled. All patients underwent measuring serum levels of miR-371a-3p and miR-367-3p before treatment, 11 had repeat measurement after treatment, 2 also had testicular vein blood examinations. Serum levels were measured by quantitative PCR. In addition, four orchiectomy specimens of patients with GCT were examined immunohistochemically and by in situ hybridization (ISH) with a probe specific for miR-371a-3p to look for the presence of this miR in GCNis cells.

Results

The median serum level of miR-371a-3p was significantly higher in patients with GCNis than in controls, miR-367 levels were not elevated. Overall, 14 patients (51.9%) had elevated serum levels of miR-371a-3p. The highest levels were found in patients with bilateral GCNis. Levels in testicular vein serum were elevated in both of the cases. After treatment, all elevated levels dropped to normal. In two orchiectomy specimens, miR-371a-3p was detected by ISH in GCNis cells.

Conclusions

Measuring miR-371a-3p serum levels can replace control biopsies after treatment of GCNis. In addition, the test can guide clinical decision making regarding the need of testicular biopsy in cases suspicious of GCNis.

Loss of miR-514a-3p regulation of PEG3 activates the NF-kappa B pathway in human testicular germ cell tumors

Deregulation of microRNAs (miRNAs) contributes to the development and progression of many cancer types; however, their functions in the pathogenesis of testicular germ cell tumor (TGCT) remain unclear. Here, we determined miRNA expression profiles of TGCTs and normal testes using small RNA sequencing, and identified several deregulated miRNAs in TGCTs, including the miR-506~514 cluster. In functional studies in vitro we demonstrated that miR-514a-3p induced apoptosis through direct regulation of the paternally expressed gene 3 (PEG3), and ectopically expressed PEG3 could rescue the apoptotic effect of miR-514a-3p overexpression. Silencing of PEG3 or miR-514a-3p overexpression reduced nuclear accumulation of p50 and NF-κB reporter activity. Furthermore, PEG3 was co-immunoprecipitated with tumor necrosis factor receptor-associated factor 2 (TRAF2) in TGCT cell lysates. We propose a model of PEG3-mediated activation of NF-κB in TGCT. Loss of miR-514a-3p expression in TGCT increases PEG3 expression that recruits TRAF2 and activates the NF-kappa B pathway, which protects germ cells from apoptosis. Importantly, we observed strong expression of PEG3 and nuclear p50 in the majority of TGCTs (83% and 78%, respectively). In conclusion, our study describes a novel function for miR-514a-3p in TGCT and highlights an unrecognized mechanism of PEG3 regulation and NF-κB activation in TGCT.

The epigenetics of testicular germ cell tumors: looking for novel disease biomarkers

Testicular germ cell tumors (TGCT) are a group of heterogeneous, biologically diverse and clinically challenging neoplasms. Despite the relatively low incidence and mortality rates, a subgroup of patients with disseminated disease relapse after conventional therapy and have a dismal prognosis. Moreover, TGCT afflict mostly young men and have therapeutic peculiarities, with some patients showing resistance to cisplatin-based treatments and others being troubled by irreversible side effects, such as infertility. Most TGCT share a common tumorigenic pathway and are cytogenetically similar, making room for Epigenetics to explain its heterogeneity at pathological and clinical level. In this review, we summarize the foremost epigenetic alterations among TGCT focusing on their clinical potential as diagnostic, prognostic and predictive biomarkers.

The biology of germ cell tumors in disorders of sex development

Development of a malignant germ cell tumor, i.e., germ cell cancer (GCC) in individuals with disorders of sex development (DSD) depends on a number of (epi-)genetic factors related to early gonadal- and germ cell development, possibly related to genetic susceptibility. Fetal development of germ cells is orchestrated by strict processes involving specification, migration and the development of a proper gonadal niche. In this review we will discuss the early (epi-)genetic events in normal and aberrant germ cell and gonadal development. Focus will be on the formation of the precursor lesions of GCC in individuals who have DSD. In our view, expression of the different embryonic markers in, and epigenetic profile of the precursor lesions reflects the developmental stage in which these cells are blocked in their maturation. Therefore, these are not a primary pathogenetic driving force. Progression later in life towards a full blown cancer likely depends on additional factors such as a changed endocrine environment in a susceptible individual. Genetic susceptibility is, as evidenced by the presence of specific risk genetic variants (SNPs) in patients with a testicular GCC, related to genes involved in early germ cell and gonadal development.

What Is Trophoblast? A Combination of Criteria Define Human First-Trimester Trophoblast

Controversy surrounds reports describing the derivation of human trophoblast cells from placentas and embryonic stem cells (ESC), partly due to the difficulty in identifying markers that define cells as belonging to the trophoblast lineage. We have selected criteria that are characteristic of primary first-trimester trophoblast: a set of protein markers, HLA class I profile, methylation of ELF5, and expression of microRNAs (miRNAs) from the chromosome 19 miRNA cluster (C19MC). We tested these criteria on cells previously reported to show some phenotypic characteristics of trophoblast: bone morphogenetic protein (BMP)-treated human ESC and 2102Ep, an embryonal carcinoma cell line. Both cell types only show some, but not all, of the four trophoblast criteria. Thus, BMP-treated human ESC have not fully differentiated to trophoblast. Our study identifies a robust panel, including both protein and non-protein-coding markers that, in combination, can be used to reliably define cells as characteristic of early trophoblast.

The present and future of serum diagnostic tests for testicular germ cell tumours

Testicular germ cell tumours (GCTs) are the most common malignancy occurring in young adult men and the incidence of these tumours is increasing. Current research priorities in this field include improving overall survival for patients classified as being 'poor-risk' and reducing late effects of treatment for patients classified as 'good-risk'. Testicular GCTs are broadly classified into seminomas and nonseminomatous GCTs (NSGCTs). The conventional serum protein tumour markers α-fetoprotein (AFP), human chorionic gonadotrophin (hCG) and lactate dehydrogenase (LDH) show some utility in the management of testicular malignant GCT. However, AFP and hCG display limited sensitivity and specificity, being indicative of yolk sac tumour (AFP) and choriocarcinoma or syncytiotrophoblast (hCG) subtypes. Furthermore, LDH is a very nonspecific biomarker. Consequently, seminomas and NSGCTs comprising a pure embryonal carcinoma subtype are generally negative for these conventional markers. As a result, novel universal biomarkers for testicular malignant GCTs are required. MicroRNAs are short, non-protein-coding RNAs that show much general promise as biomarkers. MicroRNAs from two 'clusters', miR-371-373 and miR-302-367, are overexpressed in all malignant GCTs, regardless of age (adult or paediatric), site (gonadal or extragonadal) and subtype (seminomas, yolk sac tumours or embryonal carcinomas). A panel of four circulating microRNAs from these two clusters (miR-371a-3p, miR-372-3p, miR-373-3p and miR-367-3p) is highly sensitive and specific for the diagnosis of malignant GCT, including seminoma and embryonal carcinoma. In the future, circulating microRNAs might be useful in diagnosis, disease monitoring and prognostication of malignant testicular GCTs, which might also reduce reliance on serial CT scanning. For translation into clinical practice, important practical considerations now need addressing.

Altered micro-ribonucleic acid expression profiles of extracellular microvesicles in the seminal plasma of patients with oligoasthenozoospermia

OBJECTIVE

To determine whether microRNA (miRNA) expression profile is different in extracellular microvesicles collected from seminal plasma of men with oligoasthenozoospermia, to gain further insight into molecular mechanisms underlying male infertility.

DESIGN

Microarray with quantitative real-time polymerase chain reaction validation and Western blot analysis confirmation.

SETTING

University research and clinical institutes.

PATIENT(S)

A total of 24 men, including 12 oligoasthenozoospermic subfertile men and 12 normozoospermic men.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Statistically significant altered miRNA expression profiles in oligoasthenozoospermic subfertile men compared with normozoospermic fertile men.

RESULT(S)

Extracellular microvesicles including exosomes were isolated from seminal plasma by ultracentrifugation. Presence of exosome-specific proteins was confirmed by Western blotting. In the extracellular microvesicles, we analyzed 1,205 miRNAs by microarray and identified 36 miRNAs with altered expression levels in oligoasthenozoospermic compared with normozoospermic fertile men. Seven miRNAs were overexpressed and 29 miRNAs were underexpressed in oligoasthenozoospermic men. Using quantitative real-time polymerase chain reaction as an independent method, we confirmed the significantly higher expression levels of miR-765 and miR-1275 and the significantly lower expression level of miR-15a in oligoasthenozoospermic subfertile men as compared with the normozoospermic men.

CONCLUSION(S)

We identified altered expression levels of miRNAs in extracellular microvesicles from seminal plasma as part of the molecular events in the male genital tract. These miRNAs may help to understand the molecular mechanisms underlying male infertility.

MicroRNAs as regulators of beta-cell function and dysfunction

In the last decade, there has been an explosion in both the number of and knowledge about miRNAs associated with both type 1 and type 2 diabetes. Even though we are presently in the initial stages of understanding how this novel class of posttranscriptional regulators are involved in diabetes, recent studies have demonstrated that miRNAs are important regulators of the islet transcriptome, controlling apoptosis, differentiation and proliferation, as well as regulating unique islet and beta-cell functions and pathways such as insulin expression, processing and secretion. Furthermore, a large number of miRNAs have been linked to diabetogenic processes induced by elevated levels of glucose, free fatty acids and inflammatory cytokines. Thus, miRNAs are novel therapeutic targets with the potential of protecting the beta-cell, and there is proof of principle that miRNA antagonists, so-called antagomirs, are effective in vivo for other disorders. miRNAs are exported out of cells in exosomes, raising the intriguing possibility of cell-to-cell communication between distant tissues via miRNAs and that miRNAs can be used as biomarkers of beta-cell function, mass and survival. The purpose of this review is to provide a status on how miRNAs control beta-cell function and viability in health and disease.

Testicular germ cell tumours

Testicular germ cell tumours are at the crossroads of developmental and neoplastic processes. Their cause has not been fully elucidated but differences in incidences suggest that a combination of genetic and environment factors are involved, with environmental factors predominating early in life. Substantial progress has been made in understanding genetic susceptibility in the past 5 years on the basis of the results of large genome-wide association studies. Testicular germ cell tumours are highly sensitive to radiotherapy and chemotherapy and hence have among the best outcomes of all tumours. Because the tumours occur mainly in young men, preservation of reproductive function, quality of life after treatment, and late effects are crucial concerns. In this Seminar, we provide an overview of advances in the understanding of the epidemiology, genetics, and biology of testicular germ cell tumours. We also summarise the consensus on how to treat testicular germ cell tumours and focus on a few controversies and improvements in the understanding of late effects of treatment and quality of life for survivors.

MicroRNAs in Testicular Cancer Diagnosis and Prognosis

Testicular cancer processes a unique and clear miRNA expression signature. This differentiates testicular cancer from most other cancer types, which are usually more ambiguous when assigning miRNA patterns. As such, testicular cancer may represent a unique cancer type in which miRNAs find their use as biomarkers for cancer diagnosis and prognosis, with a potential to surpass the current available markers usually with low sensitivity. In this review, we present literature findings on miRNAs associated with testicular cancer, and discuss their potential diagnostic and prognostic values, as well as their potential as indicators of drug response in patients with testicular cancer.

The SOX17/miR-371-5p/SOX2 axis inhibits EMT, stem cell properties and metastasis in colorectal cancer

Cancer stem cells (CSCs) and EMT-type cells, which share molecular characteristics with CSCs, have been believed to play critical roles in tumor metastasis. Although much progress has been garnered in elucidating the molecular pathways that trigger EMT, stemness and metastasis, a number of key mechanistic gaps remain elusive. In the study, miR-371-5p was obviously down-regulated in primary CRC tissues compared with matched adjacent normal mucosa and correlated significantly with differentiation, tumor size, lymphatic and liver metastases. MiR-371-5p could attenuate proliferation, invasion in vitro and metastasis in vivo in CRC cells. It also suppressed EMT by regulating Wnt/β-catenin signaling and strongly decreased the CRC stemness phenotypes. Moreover, demethylation of SOX17 induced miR-371-5p expression and consequently suppressed its direct target SOX2 in CRC cells. MiR-371-5p was necessary for SOX17 mediated cancer-related traits and SOX2 was a functional target of miR-371-5p. A positive relationship between SOX17 and miR-371-5p expression and a negative one between miR-371-5p and SOX2 expression were observed in CRC cell lines and tissues. In conclusion, we identified miR-371-5p as an important “oncosuppressor” in CRC progression and elucidated a novel mechanism of the SOX17/miR-371-5p/SOX2 axis in the regulation of EMT, stemness and metastasis, which may be a potential therapeutic target.

Male Reproductive Disorders and Fertility Trends: Influences of Environment and Genetic Susceptibility

It is predicted that Japan and European Union will soon experience appreciable decreases in their populations due to persistently low total fertility rates (TFR) below replacement level (2.1 child per woman). In the United States, where TFR has also declined, there are ethnic differences. Caucasians have rates below replacement, while TFRs among African-Americans and Hispanics are higher. We review possible links between TFR and trends in a range of male reproductive problems, including testicular cancer, disorders of sex development, cryptorchidism, hypospadias, low testosterone levels, poor semen quality, childlessness, changed sex ratio, and increasing demand for assisted reproductive techniques. We present evidence that several adult male reproductive problems arise in utero and are signs of testicular dysgenesis syndrome (TDS). Although TDS might result from genetic mutations, recent evidence suggests that it most often is related to environmental exposures of the fetal testis. However, environmental factors can also affect the adult endocrine system. Based on our review of genetic and environmental factors, we conclude that environmental exposures arising from modern lifestyle, rather than genetics, are the most important factors in the observed trends. These environmental factors might act either directly or via epigenetic mechanisms. In the latter case, the effects of exposures might have an impact for several generations post-exposure. In conclusion, there is an urgent need to prioritize research in reproductive physiology and pathophysiology, particularly in highly industrialized countries facing decreasing populations. We highlight a number of topics that need attention by researchers in human physiology, pathophysiology, environmental health sciences, and demography.

Etiology and early pathogenesis of malignant testicular germ cell tumors: towards possibilities for preinvasive diagnosis

Malignant testicular germ cell tumors (TGCT) are the most frequent cancers in Caucasian males (20-40 years) with an 70% increasing incidence the last 20 years, probably due to combined action of (epi)genetic and (micro)environmental factors. It is expected that TGCT have carcinoma in situ(CIS) as their common precursor, originating from an embryonic germ cell blocked in its maturation process. The overall cure rate of TGCT is more than 90%, however, men surviving TGCT can present long-term side effects of systemic cancer treatment. In contrast, men diagnosed and treated for CIS only continue to live without these long-term side effects. Therefore, early detection of CIS has great health benefits, which will require an informative screening method. This review described the etiology and early pathogenesis of TGCT, as well as the possibilities of early detection and future potential of screening men at risk for TGCT. For screening, a well-defined risk profile based on both genetic and environmental risk factors is needed. Since 2009, several genome wide association studies (GWAS) have been published, reporting on single-nucleotide polymorphisms (SNPs) with significant associations in or near the genes KITLG, SPRY4, BAK1, DMRT1, TERT, ATF7IP, HPGDS, MAD1L1, RFWD3, TEX14, and PPM1E, likely to be related to TGCT development. Prenatal, perinatal, and postnatal environmental factors also influence the onset of CIS. A noninvasive early detection method for CIS would be highly beneficial in a clinical setting, for which specific miRNA detection in semen seems to be very promising. Further research is needed to develop a well-defined TGCT risk profile, based on gene-environment interactions, combined with noninvasive detection method for CIS.

Changes in the expression profiles of claudins during gonocyte differentiation and in seminomas

Testicular germ cell tumors (TGCTs) are the most common type of cancer in young men and their incidence has been steadily increasing for the past decades. TGCTs and their precursor carcinoma in situ (CIS) are thought to arise from the deficient differentiation of gonocytes, precursors of spermatogonial stem cells. However, the mechanisms relating failed gonocyte differentiation to CIS formation remain unknown. The goal of this study was to uncover genes regulated during gonocyte development that would show abnormal patterns of expression in testicular tumors, as prospective links between failed gonocyte development and TGCT. To identify common gene and protein signatures between gonocytes and seminomas, we first performed gene expression analyses of transitional rat gonocytes, spermatogonia, human normal testicular, and TGCT specimens. Gene expression arrays, pathway analysis, and quantitative real-time PCR analysis identified cell adhesion molecules as a functional gene category including genes downregulated during gonocyte differentiation and highly expressed in seminomas. In particular, the mRNA and protein expressions of claudins 6 and 7 were found to decrease during gonocyte transition to spermatogonia, and to be abnormally elevated in seminomas. The dynamic changes in these genes suggest that they may play important physiological roles during gonocyte development. Moreover, our findings support the idea that TGCTs arise from a disruption of gonocyte differentiation, and position claudins as interesting genes to further study in relation to testicular cancer.

Involvement of epigenetic modifiers in the pathogenesis of testicular dysgenesis and germ cell cancer

Testicular germ cell cancer manifests mainly in young adults as a seminoma or non-seminoma. The solid tumors are preceded by the presence of a non-invasive precursor cell, the carcinoma in situ cell (CIS), which shows great similarity to fetal germ cells. It is therefore hypothesized that the CIS cell is a fetal germ cell that has been arrested during development due to testicular dysgenesis. CIS cells retain a fetal and open chromatin structure, and recently several epigenetic modifiers have been suggested to be involved in testicular dysgenesis in mice. We here review the possible involvement of epigenetic modifiers with a focus on jumonji C enzymes in the development of testicular dysgenesis and germ cell cancer in men.

Diversity and functional convergence of small noncoding RNAs in male germ cell differentiation and fertilization

The small noncoding RNAs (sncRNAs) are considered as post-transcriptional key regulators of male germ cell development. In addition to microRNAs (miRNAs) and PIWI-interacting RNAs (piRNAs), other sncRNAs generated from small nucleolar RNAs (snoRNAs), tRNAs, or rRNAs processing may also play important regulatory roles in spermatogenesis. By next-generation sequencing (NGS), we characterized the sncRNA populations detected at three milestone stages in male germ differentiation: primordial germ cells (PGCs), pubertal spermatogonia cells, and mature spermatozoa. To assess their potential transmission through the spermatozoa during fertilization, the sncRNAs of mouse oocytes and zygotes were also analyzed. Both, microRNAs and snoRNA-derived small RNAs are abundantly expressed in PGCs but transiently replaced by piRNAs in spermatozoa and endo-siRNAs in oocytes and zygotes. Exhaustive analysis of miRNA sequence variants also shows an increment of noncanonical microRNA forms along male germ cell differentiation. RNAs-derived from tRNAs and rRNAs interacting with PIWI proteins are not generated by the ping-pong pathway and could be a source of primary piRNAs. Moreover, our results strongly suggest that the small RNAs-derived from tRNAs and rRNAs are interacting with PIWI proteins, and specifically with MILI. Finally, computational analysis revealed their potential involvement in post-transcriptional regulation of mRNA transcripts suggesting functional convergence among different small RNA classes in germ cells and zygotes.

An oncofetal and developmental perspective on testicular germ cell cancer

Germ cell tumors (GCTs) represent a diverse group of tumors presumably originating from (early fetal) developing germ cells. Most frequent are the testicular germ cell cancers (TGCC). Overall, TGCC is the most frequent malignancy in Caucasian males (20-40 years) and remains an important cause of (treatment related) mortality in these young men. The strong association between the phenotype of TGCC stem cell components and their totipotent ancestor (fetal primordial germ cell or gonocyte) makes these tumors highly relevant from an onco-fetal point of view. This review subsequently discusses the evidence for the early embryonic origin of TGCCs, followed by an overview of the crucial association between TGCC pathogenesis, genetics, environmental exposure and the (fetal) testicular micro-environment (genvironment). This culminates in an evaluation of three genvironmentally modulated hallmarks of TGCC directly related to the oncofetal pathogenesis of TGCC: (1) maintenance of pluripotency, (2) cell cycle control/cisplatin sensitivity and (3) regulation of proliferation/migration/apoptosis by KIT-KITL mediated receptor tyrosine kinase signaling. Briefly, TGCC exhibit identifiable stem cell components (seminoma and embryonal carcinoma) and progenitors that show large and consistent similarities to primordial/embryonic germ cells, their presumed totipotent cells of origin. TGCC pathogenesis depends crucially on a complex interaction of genetic and (micro-)environmental, i.e. genvironmental risk factors that have only been partly elucidated despite significant effort. TGCC stem cell components also show a high degree of similarity with embryonic stem/germ cells (ES) in the regulation of pluripotency and cell cycle control, directly related to their exquisite sensitivity to DNA damaging agents (e.g. cisplatin). Of note, (ES specific) micro-RNAs play a pivotal role in the crossover between cell cycle control, pluripotency and chemosensitivity. Moreover, multiple consistent observations reported TGCC to be associated with KIT-KITL mediated receptor tyrosine kinase signaling, a pathway crucially implicated in proliferation, migration and survival during embryogenesis including germ cell development. In conclusion, TGCCs are a fascinating model for onco-fetal developmental processes especially with regard to studying cell cycle control, pluripotency maintenance and KIT-KITL signaling. The knowledge presented here contributes to better understanding of the molecular characteristics of TGCC pathogenesis, translating to identification of at risk individuals and enhanced quality of care for TGCC patients (diagnosis, treatment and follow-up).