Epigenetics: A way to understand the origin and biology of testicular germ cell tumors

Epigenetic Factors and ncRNAs in Testicular Cancer

Testicular cancer is the most prevalent tumor among males aged 15 to 35, resulting in a significant number of newly diagnosed cases and fatalities annually. Non-coding RNAs (ncRNAs) have emerged as key regulators in various cellular processes and pathologies, including testicular cancer. Their involvement in gene regulation, coding, decoding, and overall gene expression control suggests their potential as targets for alternative treatment approaches for this type of cancer. Furthermore, epigenetic modifications, such as histone modifications, DNA methylation, and the regulation by microRNA (miRNA), have been implicated in testicular tumor progression and treatment response. Epigenetics may also offer critical insights for prognostic evaluation and targeted therapies in patients with testicular germ cell tumors (TGCT). This comprehensive review aims to present the latest discoveries regarding the involvement of some proteins and ncRNAs, mainly miRNAs and lncRNA, in the epigenetic aspect of testicular cancer, emphasizing their relevance in pathogenesis and their potential, given the fact that their specific expression holds promise for prognostic evaluation and targeted therapies.

Epigenetic Regulation of Driver Genes in Testicular Tumorigenesis

In testicular germ cell tumor type II (TGCT), a seminoma subtype expresses an induced pluripotent stem cell (iPSC) panel with four upregulated genes, OCT4/POU5F1, SOX17, KLF4, and MYC, and embryonal carcinoma (EC) has four upregulated genes, OCT4/POU5F1, SOX2, LIN28, and NANOG. The EC panel can reprogram cells into iPSC, and both iPSC and EC can differentiate into teratoma. This review summarizes the literature on epigenetic regulation of the genes. Epigenetic mechanisms, such as methylations of cytosines on the DNA string and methylations and acetylations of histone 3 lysines, regulate expression of these driver genes between the TGCT subtypes. In TGCT, the driver genes contribute to well-known clinical characteristics and the driver genes are also important for aggressive subtypes of many other malignancies. In conclusion, epigenetic regulation of the driver genes are important for TGCT and for oncology in general.

Epigenetics and Testicular Cancer: Bridging the Gap Between Fundamental Biology and Patient Care

Testicular cancer is the most common solid tumor affecting young males. Most testicular cancers are testicular germ cell tumors (TGCTs), which are divided into seminomas (SGCTs) and non-seminomatous testicular germ cell tumors (NSGCTs). During their development, primordial germ cells (PGCs) undergo epigenetic modifications and any disturbances in their pattern might lead to cancer development. The present study provides a comprehensive review of the epigenetic mechanisms–DNA methylation, histone post-translational modifications, bivalent marks, non-coding RNA–associated with TGCT susceptibility, initiation, progression and response to chemotherapy. Another important purpose of this review is to highlight the recent investigations regarding the identification and development of epigenetic biomarkers as powerful tools for the diagnostic, prognostic and especially for epigenetic-based therapy.

Molecular Biology of Pediatric and Adult Male Germ Cell Tumors

Simple Summary

Although testicular germ cell tumors (TGCTs) are rare pediatric malignancies, they are the most common malignancies in young adult men. The similarities and differences between TGCTs in adults and children, taking into account the clinic presentation, biology, and molecular changes, are underexplored. In this paper, we aim to provide an overview of the molecular aspects of TGCTs, drawing a parallel between the findings in adult and pediatric groups.

Abstract

Cancer is a leading cause of death by disease in children and the second most prevalent of all causes in adults. Testicular germ cell tumors (TGCTs) make up 0.5% of pediatric malignancies, 14% of adolescent malignancies, and are the most common of malignancies in young adult men. Although the biology and clinical presentation of adult TGCTs share a significant overlap with those of the pediatric group, molecular evidence suggests that TGCTs in young children likely represent a distinct group compared to older adolescents and adults. The rarity of this cancer among pediatric ages is consistent with our current understanding, and few studies have analyzed and compared the molecular basis in childhood and adult cancers. Here, we review the major similarities and differences in cancer genetics, cytogenetics, epigenetics, and chemotherapy resistance between pediatric and adult TGCTs. Understanding the biological and molecular processes underlying TGCTs may help improve patient outcomes, and fuel further investigation and clinical research in childhood and adult TGCTs.

Genomic landscape of platinum resistant and sensitive testicular cancers

While most testicular germ cell tumours (TGCTs) exhibit exquisite sensitivity to platinum chemotherapy, ~10% are platinum resistant. To gain insight into the underlying mechanisms, we undertake whole exome sequencing and copy number analysis in 40 tumours from 26 cases with platinum-resistant TGCT, and combine this with published genomic data on an additional 624 TGCTs. We integrate analyses for driver mutations, mutational burden, global, arm-level and focal copy number (CN) events, and SNV and CN signatures. Albeit preliminary and observational in nature, these analyses provide support for a possible mechanistic link between early driver mutations in RAS and KIT and the widespread copy number events by which TGCT is characterised.

Current knowledge of risk factors for testicular germ cell tumors

The development of the human gonads is tightly regulated by the correct sequential expression of many genes and hormonal activity. Disturbance of this regulation does not only prevent proper development of the gonads, but it also contributes to the development of testicular germ cell tumors. Recent genetic studies, especially genome-wide association studies, have made great progress in understanding genetic susceptibility. Although there is strong evidence of inherited risks, many environmental factors also contribute to the development of testicular germ cell tumors. Histopathological studies have shown that most testicular germ cell tumors arise from germ cell neoplasia in situ, which is thought to be arrested and transformed primordial germ cells. Seminoma has features identical to germ cell neoplasia in situ or primordial germ cells, whereas non-seminoma shows varied differentiation. Seminomas and embryonic cell carcinomas have the feature of pluripotency, which is thought to be the cause of histological heterogeneity and mixed pathology in testicular germ cell tumors. Testicular germ cell tumors show high sensitivity to chemotherapies, but 20-30% of patients show resistance to standard chemotherapy. In the present review, the current knowledge of the epidemiological and genomic factors for the development of testicular germ cell tumors is reviewed, and the mechanisms of resistance to chemotherapies are briefly mentioned.

Racial and Ethnic Disparities in the Incidence of Pediatric Extracranial Embryonal Tumors

Background

Few studies have comparatively assessed differences in the incidence of childhood cancer by race and ethnicity that could inform etiologic research. We aimed to identify disparities in the incidence of pediatric extracranial embryonal tumors by race and ethnicity in the United States using a population-based cancer registry.

Methods

Cases of extracranial embryonal tumors among children age 0 to 19 years diagnosed between 2000 and 2010 were retrieved from the Surveillance, Epidemiology, and End Results Program 18 (n = 8188). Age-standardized incidence rates and incidence rate ratios (IRRs) were obtained by race/ethnicity. Whites were the reference group. The percentage of families living below the poverty line by county was used to stratify by socioeconomic status (SES).

Results

All minority groups had a lower incidence of neuroblastoma (Hispanics: IRR = 0.53, 95% confidence interval [CI] = 0.47 to 0.59; blacks: IRR = 0.70, 95% CI = 0.61 to 0.81; Native-Hawaiian/Asian-Pacific-Islander (API): IRR = 0.56, 95% CI = 0.46 to 0.67; and American Indian/Alaska Native (AI/AN): IRR = 0.28, 95% CI = 0.15 to 0.48) while Hispanics had a higher incidence of retinoblastoma (IRR = 1.26, 95% CI = 1.07 to 1.48). Incidence of nephroblastoma was lower among Hispanics (IRR = 0.80, 95% CI = 0.71 to 0.91) and API (IRR = 0.43, 95% CI = 0.33 to 0.56) while equivalent for blacks. Similarly, incidence of rhabdomyosarcoma was low among Hispanics (IRR = 0.85, 95% CI = 0.74 to 0.98) and API (IRR = 0.61, 95% CI = 0.47 to 0.79) while equivalent for blacks. However, incidence of hepatoblastoma was low among blacks (IRR = 0.44, 95% CI = 0.28 to 0.68) while equivalent for Hispanics and API. Incidence of germ cell tumors was higher among Hispanics (IRR = 1.30, 95% CI = 1.19 to 1.42) and lower among blacks (IRR = 0.52, 95% CI = 0.44 to 0.61) and API (IRR = 0.79, 95% CI = 0.67 to 0.93). No effect modification by SES was observed.

Conclusions

Unique incidence patterns of childhood extracranial embryonal tumors exist by race and ethnicity in the United States. The interplay between race/ethnicity and genetics, epigenetics, and gene-environment interactions in the causation of these cancers deserves further investigation.

Clinical utility of kallikrein-related peptidases (KLK) in urogenital malignancies

Kallikrein-related peptidases (KLK), which represent a major tissue-associated proteolytic system, stand for a rich source of biomarkers that may allow molecular classification, early diagnosis and prognosis of human malignancies as well as prediction of response or failure to cancer-directed drugs. International research points to an important role of certain KLKs in female and male urogenital tract malignancies, in addition to cancers of the lung, brain, skin, head and neck, and the gastrointestinal tract. Regarding the female/male urogenital tract, remarkably, all of the KLKs are expressed in the normal prostate, testis, and kidney whereas the uterus, the ovary, and the urinary bladder are expressing a limited number of KLKs only. Most of the information regarding KLK expression in tumour-affected organs is available for ovarian cancer; all of the 12 KLKs tested so far were found to be elevated in the malignant state, depicting them as valuable biomarkers to distinguish between the normal and the cancerous phenotype. In contrast, for kidney cancer, a series of KLKs was found to be downregulated, while other KLKs were not expressed. Evidently, depending on the type of cancer or cancer stage, individual KLKs may show characteristics of a Janus-faced behaviour, by either expanding or inhibiting cancer progression and metastasis.

Epigenetic Targeting of Platinum Resistant Testicular Cancer

The involvement of epigenetic aberrations in the development and progression of tumors is now well established. However, little is known of the epigenetic alterations in testicular cancer and particularly in platinum refractory germ cell tumors. Germ cell derived testicular cancers, as compared to somatic tumors, appear to have a unique epigenetic profile that features more extensive DNA hypomethylation. Emerging data from clinical specimens suggest that epigenetic aberrations, especially DNA hypermethylation, can contribute to chemotherapy resistance and poor clinical outcomes in testicular germ cell tumors. Recent data indicate that testicular cancer cells, even those resistant to platinum, are highly sensitive to low doses of demethylating agents. Based on these promising preclinical studies, we suggest that DNA methylation inhibitors in combination with chemotherapeutic agents may offer a path to overcome acquired drug resistance in testicular cancer, laying the foundation and rationale for testing this class of epigenetic drugs in the clinical setting. In this mini-review we provide a brief overview of the promise of DNA methylation therapy to treat patients with refractory cancer of the testes.

Global network random walk for predicting potential human lncRNA-disease associations

There is more and more evidence that the mutation and dysregulation of long non-coding RNA (lncRNA) are associated with numerous diseases, including cancers. However, experimental methods to identify associations between lncRNAs and diseases are expensive and time-consuming. Effective computational approaches to identify disease-related lncRNAs are in high demand; and would benefit the detection of lncRNA biomarkers for disease diagnosis, treatment, and prevention. In light of some limitations of existing computational methods, we developed a global network random walk model for predicting lncRNA-disease associations (GrwLDA) to reveal the potential associations between lncRNAs and diseases. GrwLDA is a universal network-based method and does not require negative samples. This method can be applied to a disease with no known associated lncRNA (isolated disease) and to lncRNA with no known associated disease (novel lncRNA). The leave-one-out cross validation (LOOCV) method was implemented to evaluate the predicted performance of GrwLDA. As a result, GrwLDA obtained reliable AUCs of 0.9449, 0.8562, and 0.8374 for overall, novel lncRNA and isolated disease prediction, respectively, significantly outperforming previous methods. Case studies of colon, gastric, and kidney cancers were also implemented, and the top 5 disease-lncRNA associations were reported for each disease. Interestingly, 13 (out of the 15) associations were confirmed by literature mining.

Current Concepts of Epigenetics in Testicular Cancer

Testicular germ cell tumors (GCTs) are characterized into seminomas (SGCTs) and non-seminomatous testicular germ cell tumors (NSGCTs). Serum tumor markers (STMs) play an important role in testicular cancer as they provide useful information for diagnosis, staging, and detection of recurrence. Nonetheless, additional tumor markers for early diagnosis and therapeutic options are required to enhance specificity of serological diagnosis of testes cancers. Epigenetics is defined as inherited changes in gene expression that are not encoded in the DNA structure. Epigenetic changes include DNA methylation, histone modifications, and microRNA (miRNA) regulation. It is through the study of epigenetics that diagnostic methods for early detection and novel therapeutic strategies may be established for testicular cancer. We performed a comprehensive review of the English medical literature in PubMed by combining search terms including DNA methylation, histone modifications, microRNA (miRNA) regulation, epigenetics, and testicular cancer. DNA methylation is the most extensively studied epigenetic modification. It consists of the addition of a methyl group to nucleotide bases. It has been reported that SGCT contain reduced levels of DNA methylation compared to NSGCT. MiRNAs are small non-coding RNAs that regulate posttranscriptional gene expression. It has been suggested that miRNAs may play a role in the pathogenesis of GCT. Specific expression patterns have been displayed by various miRNAs in patients with GCT. Histones are proteins intertwined with coiled, double-stranded genomic DNA that form a structure known as a nucleosome. The most widely studied histone modifications include acetylation, methylation, and phosphorylation. Methylation of histone proteins has been found in all types of NSGCT. Epigenetics may offer an additional and effective tool in establishing a diagnosis of GCT of the testes, including prognostic information and perhaps enabling targeted treatment in patients with testicular GCT.

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.

Dimethyl sulfoxide induces chemotherapeutic resistance in the treatment of testicular embryonal carcinomas

Dimethyl sulfoxide (DMSO) is an amphipathic molecule that is used as a solvent in biological studies and as a vehicle for drug therapy. The present study was designed to evaluate the potential effects of DMSO as a solvent in the treatment of testicular embryonal carcinomas (ECs). DMSO was applied to two human EC cell lines (NEC8 and NEC14), with the treated cells evaluated in relation to cisplatin (CDDP) resistance, differentiation (using Vimentin, Fibronectin, TRA-1-60, and SSEA-1 and -3 as markers) and stemness (denoted by expression of SOX2 and OCT3/4). Furthermore, DNA methyltransferase (DNMT-1, -3A and -3L) expression and methylation status were analyzed. DMSO induced resistance to CDDP, aberrant differentiation and reduction of stemness-related markers in each of the EC cell lines. The expression levels of DNMT-3L and -3A were reduced in response to DMSO, while this treatment also affected DNA methylation. The data demonstrated that DMSO perturbed differentiation, reduced stemness and induced resistance to CDDP in human EC cells. Therefore, DMSO could reduce drug efficacy against EC cells and its use should be carefully managed in the clinical application of chemotherapy.

Intratubular germ cell neoplasia of the testis: a brief review

Germ cell tumors of the testis may be divided into 3 broad categories according to age at presentation. The tumors in the pediatric age group include teratoma and yolk sac tumor. These tumors are generally not associated with convincing intratubular neoplasia. The second group consists of tumors presenting in third and fourth decade of life and include seminoma, embryonal carcinoma, yolk sac tumor, choriocarcinoma, and teratoma as well as mixed germ cell tumors. The precursor cell for these tumors is an abnormal gonocyte that fails to differentiate completely into spermatogonia. These abnormal cells stay dormant in the gonad during intrauterine life as well as infancy and childhood, but undergo proliferation during puberty and can be identified as intratubular germ cell neoplasia unclassified (IGCNU). These tumor cells continue to manifest protein expression pattern that resembles primitive germ cells (PLAP, c-KIT, OCT3/4). After a variable interval following puberty, IGCNU cells may acquire ability to penetrate the seminiferous tubules and present as an overt germ cell tumor. Acquisition of isochrome 12 and other genetic abnormalities are usually associated with this transition. The level of DNA methylation generally determines the phenotype of the germ cell tumor. The third type of germ cell tumors is spermatocytic seminoma, which is a rare tumor encountered later in life usually in fifth and sixth decade. The cell of origin of this tumor is probably postpubertal mature spermatogonia which acquire abnormal proliferative capability probably due to gain of chromosome 9 resulting in activation and amplification of genes such as DMRT1. The tumor cells manifest many of the proteins normally expressed by mature sperms such as VASA, SSX2, and occasionally OCT2. Although spermatocytic seminoma may also have an intratubular growth phase, it completely lacks features of IGCNU.

Epigenetic dimension of oxygen radical injury in spermatogonial epithelial cells

The present work reports a direct role of mitochondrial oxidative stress induced aberrant chromatin regulation, as a central phenomenon, to perturbed genomic integrity in the testicular milieu. Oxygen-radical injury following N-succinimidyl N-methylcarbamate treatment in mouse spermatogonial epithelial (GC-1 spg) cells induced functional derailment of mitochondrial machinery. Mitophagy resulted in marked inhibition of mitochondrial respiration and reduced mtDNA copy number. Impaired cell cycle progression along with altered H3K9me1, H4K20me3, H3, AcH3 and uH2A histone modifications were observed in the treated cells. Dense heterochromatin foci and aberrant expression of HP1α in nuclei of treated cells implied onset of senescence associated secretory phenotype mediated through nuclear accumulation of NF-κB. Neoplastic nature of daughter clones, emerged from senescent mother phenotypes was confirmed by cytogenetic instability, aberrant let-7a and let-7b miRNA expression and anchorage independent growth. Together, our results provide the first insights of redox-dependent epigenomic imbalance in spermatogonia, a previously unknown molecular paradigm.

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).

CMTM3 inhibits human testicular cancer cell growth through inducing cell-cycle arrest and apoptosis

Human CMTM3 has been proposed as a putative tumor suppressor gene. The loss of CMTM3 has been found in several carcinomas. However, the regulation of CMTM3 expression and its function in tumor progression remain largely unknown. Here, we investigated the regulation of CMTM3 expression, function and molecular mechanism in human testicular cancer cells. CMTM3 was frequently downregulated or silenced in testicular cancer cell lines and tumor tissues but highly expressed in normal testis tissues. The re-expression of CMTM3 significantly suppressed the colony formation, proliferation, and migration capacity of testicular cancer cells by inducing a G2 cell cycle arrest and apoptosis. Moreover, the re-expression of CMTM3 activated the transcription of p53, induced p53 accumulation, up-regulated the expression of p21, and increased the cleavage of caspase 9, 8, 3, and PARP. The downregulation of CMTM3 in clinical tumor tissues was associated with the methylation of a single CpG site located within the Sp1/Sp3-responsive region of the core promoter. These results indicate that CMTM3 can function as tumor suppressor through the induction of a G2 cell cycle arrest and apoptosis. CMTM3 is thus involved in testicular cancer pathogenesis, and it is frequently at least partially silenced by the methylation of a single, specific CpG site in tumor tissues.

Emerging clinical importance of the cancer biomarkers kallikrein-related peptidases (KLK) in female and male reproductive organ malignancies

Background

Tumor tissue-associated KLKs (kallikrein-related peptidases) are clinically important biomarkers that may allow prognosis of the cancer disease and/or prediction of response/failure of cancer patients to cancer-directed drugs. Regarding the female/male reproductive tract, remarkably, all of the fifteen KLKs are expressed in the normal prostate, breast, cervix uteri, and the testis, whereas the uterus/endometrium and the ovary are expressing a limited number of KLKs only.

Conclusions

Most of the information regarding elevated expression of KLKs in tumor-affected organs is available for ovarian cancer; depicting them as valuable biomarkers in the cancerous phenotype. In contrast, for breast cancer, a series of KLKs was found to be downregulated. However, in breast cancer, KLK4 is elevated which is also true for ovarian and prostate cancer. In such cases, selective synthetic KLK inhibitors that aim at blocking the proteolytic activities of certain KLKs may serve as future candidate therapeutic drugs to interfere with tumor progression and metastasis.

Current and future biologic markers for disease progression and relapse in testicular germ cell tumors: a review

Testicular germ cell tumors represent a biologically unique disease process. These tumors are exquisitely sensitive to platinum-based chemotherapy, can be cured with surgical metastasectomy, and are known for the integration of biologic markers to stage and assign risk. Exploring further biologic markers that offer insight into the molecular mechanisms that contribute to disease biology is important. In this review, we attempt to summarize the utility of the current and some future biologic markers for disease monitoring and relapse.

DNA methylation in germ cell tumour aetiology: current understanding and outstanding questions

Germ cell tumours (GCTs) are a diverse group of neoplasms that can be histologically subclassified as either seminomatous or non-seminomatous. These two subtypes have distinct levels of differentiation and clinical characteristics, the non-seminomatous tumours being associated with poorer prognosis. In this article, we review how different patterns of aberrant DNA methylation relate to these subtypes. Aberrant DNA methylation is a hallmark of all human cancers, but particular subsets of cancers show unusually high frequencies of promoter region hypermethylation. Such a 'methylator phenotype' has been described in non-seminomatous tumours. We discuss the possible cause of distinct methylation profiles in GCTs and the potential of DNA methylation to provide new targets for therapy. We also consider how recent developments in our understanding of this epigenetic modification and the development of genome-wide technologies are shedding new light on the role of DNA methylation in cancer aetiology.

An alkylphenol mix promotes seminoma derived cell proliferation through an ERalpha36-mediated mechanism

Long chain alkylphenols are man-made compounds still present in industrial and agricultural processes. Their main use is domestic and they are widespread in household products, cleansers and cosmetics, leading to a global environmental and human contamination. These molecules are known to exert estrogen-like activities through binding to classical estrogen receptors. In vitro, they can also interact with the G-protein coupled estrogen receptor. Testicular germ cell tumor etiology and progression are proposed to be stimulated by lifelong estrogeno-mimetic exposure. We studied the transduction signaling pathways through which an alkyphenol mixture triggers testicular cancer cell proliferation in vitro and in vivo. Proliferation assays were monitored after exposure to a realistic mixture of 4-tert-octylphenol and 4-nonylphenol of either TCam-2 seminoma derived cells, NT2/D1 embryonal carcinoma cells or testis tumor in xenografted nude mice. Specific pharmacological inhibitors and gene-silencing strategies were used in TCam-2 cells in order to demonstrate that the alkylphenol mix triggers CREB-phosphorylation through a rapid, ERα36-PI3kinase non genomic pathway. Microarray analysis of the mixture target genes revealed that this pathway can modulate the expression of the DNA-methyltransferase-3 (Dnmt3) gene family which is involved in DNA methylation control. Our results highlight a key role for ERα36 in alkylphenol non genomic signaling in testicular germ cell tumors. Hence, ERα36-dependent control of the epigenetic status opens the way for the understanding of the link between endocrine disruptor exposure and the burden of hormone sensitive cancers.

Acute hypersensitivity of pluripotent testicular cancer-derived embryonal carcinoma to low-dose 5-aza deoxycytidine is associated with global DNA Damage-associated p53 activation, anti-pluripotency and DNA demethylation

Human embryonal carcinoma (EC) cells are the stem cells of nonseminoma testicular germ cells tumors (TGCTs) and share remarkable similarities to human embryonic stem (ES) cells. In prior work we found that EC cells are hypersensitive to low nanomolar doses of 5-aza deoxycytidine (5-aza) and that this hypersensitivity partially depended on unusually high levels of the DNA methyltransferase, DNMT3B. We show here that low-dose 5-aza treatment results in DNA damage and induction of p53 in NT2/D1 cells. In addition, low-dose 5-aza results in global and gene specific promoter DNA hypomethylation. Low-dose 5-aza induces a p53 transcriptional signature distinct from that induced with cisplatin in NT2/D1 cells and also uniquely downregulates genes associated with pluripotency including NANOG, SOX2, GDF3 and Myc target genes. Changes in the p53 and pluripotency signatures with 5-aza were to a large extent dependent on high levels of DNMT3B. In contrast to the majority of p53 target genes upregulated by 5-aza that did not show DNA hypomethylation, several other genes induced with 5-aza had corresponding decreases in promoter methylation. These genes include RIN1, SOX15, GPER, and TLR4 and are novel candidate tumors suppressors in TGCTs. Our studies suggest that the hypersensitivity of NT2/D1 cells to low-dose 5-aza is multifactorial and involves the combined activation of p53 targets, repression of pluripotency genes, and activation of genes repressed by DNA methylation. Low-dose 5-aza therapy may be a general strategy to treat those tumors that are sustained by cells with embryonic stem-like properties.GEO NUMBER FOR THE MICROARRAY DATA: GSE42647.