DNA damage response in human testes and testicular germ cell tumours: biology and implications for therapy

Strong apoptotic response of testis tumor cells following cisplatin treatment

Most solid metastatic cancers are resistant to chemotherapy. However, metastatic testicular germ cell tumors (TGCT) are cured in over 80% of patients using cisplatin-based combination therapy. Published data suggest that TGCTs are sensitive to cisplatin due to limited DNA repair and presumably also to a propensity to undergo apoptosis. To further investigate this aspect, cisplatin-induced activation of apoptotic pathways was investigated in cisplatin-sensitive testis tumor cells (TTC) and compared to cisplatin-resistant bladder cancer cells. Apoptosis induction was investigated using flow cytometry, caspase activation and PARP-1 cleavage. Immunoblotting and RT-PCR were applied to investigate pro- and anti-apoptotic proteins. Transfections were performed to target p53- and Fas/FasL-mediated apoptotic signaling. Immunoblotting experiments revealed p53 to be induced in TTC, but not bladder cancer cells following cisplatin. Higher levels of pro-apoptotic Bax and Noxa were observed in TTC, anti-apoptotic Bcl-2 was solely expressed in bladder cancer cells. Cisplatin led to translocation of Bax to the mitochondrial membrane in TTC, resulting in cytochrome C release. Cisplatin increased the expression of FasR mRNA and FasL protein in all tumor cell lines. Targeting the apoptotic pathway via siRNA-mediated knockdown of p53 and FAS reduced death receptor-mediated apoptosis and increased cisplatin resistance in TTC, indicating the involvement of FAS-mediated apoptosis in the cisplatin TTC response. In conclusion, both the death receptor and the mitochondrial apoptotic pathway become strongly activated in TTC following cisplatin treatment, explaining, together with attenuated DNA repair, their unique sensitivity toward platinum-based anticancer drugs.

Analysis of microsatellite instability (MSI) in pediatric gonadal and extra-gonadal germ cell tumors

Gonadal and extragonadal pediatric germ cell tumors (GCTs) are rare neoplasms with different clinical behavior. Although surgery and cisplatin-based chemotherapy are resolutive in most cases, some patients do not respond to chemotherapy and have a worse outcome. Microsatellite instability (MSI) was correlated to resistance to chemotherapy and sensitivity to immunotherapy in different neoplasms. A series of 21 pediatric GCTs were tested by immuno-histochemistry and PCR to evaluate MSI status. Next generation sequencing was applied to further evaluate cases with discordant results between immunohistochemistry and PCR. Twenty-one cases of pediatric GCT were included in the series. The mean age ranged between 1 and 10 years. Nine cases were gonadal GCTs and the remaining 12 were extra-gonadal GCTs. By immunohistochemistry, one case showed a deficit of Mismatch repair (MMR) proteins. This case was a 1-year-old children affected by gonadal yolk sac tumor. However, all cases resulted microsatellite stable (MSS) by PCR and NGS. MSI was not detected in our series of pediatric GCTs, as well as the data present in literature about adult patients with GCTs. Molecular techniques could have a role to confirm the MSI status in case of dMMR by immunohistochemistry.

RNA-Binding Proteins in Bladder Cancer

RNA-binding proteins (RBPs) are key regulators of transcription and translation, with highly dynamic spatio-temporal regulation. They are usually involved in the regulation of RNA splicing, polyadenylation, and mRNA stability and mediate processes such as mRNA localization and translation, thereby affecting the RNA life cycle and causing the production of abnormal protein phenotypes that lead to tumorigenesis and development. Accumulating evidence supports that RBPs play critical roles in vital life processes, such as bladder cancer initiation, progression, metastasis, and drug resistance. Uncovering the regulatory mechanisms of RBPs in bladder cancer is aimed at addressing the occurrence and progression of bladder cancer and finding new therapies for cancer treatment. This article reviews the effects and mechanisms of several RBPs on bladder cancer and summarizes the different types of RBPs involved in the progression of bladder cancer and the potential molecular mechanisms by which they are regulated, with a view to providing information for basic and clinical researchers.

Non-Coding RNAs and Splicing Activity in Testicular Germ Cell Tumors

Testicular germ cell tumors (TGCTs) are the most common tumors in adolescent and young men. Recently, genome-wide studies have made it possible to progress in understanding the molecular mechanisms underlying the development of tumors. It is becoming increasingly clear that aberrant regulation of RNA metabolism can drive tumorigenesis and influence chemotherapeutic response. Notably, the expression of non-coding RNAs as well as specific splice variants is deeply deregulated in human cancers. Since these cancer-related RNA species are considered promising diagnostic, prognostic and therapeutic targets, understanding their function in cancer development is becoming a major challenge. Here, we summarize how the different expression of RNA species repertoire, including non-coding RNAs and protein-coding splicing variants, impacts on TGCTs’ onset and progression and sustains therapeutic resistance. Finally, the role of transcription-associated R-loop misregulation in the maintenance of genomic stability in TGCTs is also discussed.

Cisplatin Resistance in Testicular Germ Cell Tumors: Current Challenges from Various Perspectives

Testicular germ cell tumors share a marked sensitivity to cisplatin, contributing to their overall good prognosis. However, a subset of patients develop resistance to platinum-based treatments, by still-elusive mechanisms, experiencing poor quality of life due to multiple (often ineffective) interventions and, eventually, dying from disease. Currently, there is a lack of defined treatment opportunities for these patients that tackle the mechanism(s) underlying the emergence of resistance. Herein, we aim to provide a multifaceted overview of cisplatin resistance in testicular germ cell tumors, from the clinical perspective, to the pathobiology (including mechanisms contributing to induction of the resistant phenotype), to experimental models available for studying this occurrence. We provide a systematic summary of pre-target, on-target, post-target, and off-target mechanisms putatively involved in cisplatin resistance, providing data from preclinical studies and from those attempting validation in clinical samples, including those exploring specific alterations as therapeutic targets, some of them included in ongoing clinical trials. We briefly discuss the specificities of resistance related to teratoma (differentiated) phenotype, including the phenomena of growing teratoma syndrome and development of somatic-type malignancy. Cisplatin resistance is most likely multifactorial, and a combination of therapeutic strategies will most likely produce the best clinical benefit.

Further insights into testicular germ cell tumor oncogenesis: potential therapeutic targets

Introduction: Testicular germ cell tumors (TGCTs) are the most common neoplasia in the young male population, and the incidence has been constantly increasing in many parts of the world. These tumors are classified into seminomas and non-seminomas, and those divided, in turn, into yolk sac tumors, embryonal cell carcinomas, choriocarcinomas, and teratomas. Although therapeutic approaches have improved, approximately 25% of the patients relapse or, in a small number of cases, show platinum-resistant disease.Areas covered: We review several molecular targets that have recently emerged as powerful tools for both diagnosis and therapy of TGCTs. Moreover, we reviewed the most frequent deregulated pathways involved in TGCT tumorigenesis, reporting drugs that may emerge as novel therapeutic agents.Expert opinion: TGCT treatment is mainly based on platinum-derivative therapy with high cure rates. However, in the refractory patients, there are few alternative treatments. Thus, different pharmacological approaches have to be thoroughly investigated to shed new light on TGCT pathogenesis and treatment.

Oncological role of HMGA2 (Review)

The high mobility group A2 (HMGA2) protein is a non‑histone architectural transcription factor that modulates the transcription of several genes by binding to AT‑rich sequences in the minor groove of B‑form DNA and alters the chromatin structure. As a result, HMGA2 influences a variety of biological processes, including the cell cycle process, DNA damage repair process, apoptosis, senescence, epithelial‑mesenchymal transition and telomere restoration. In addition, the overexpression of HMGA2 is a feature of malignancy, and its elevated expression in human cancer predicts the efficacy of certain chemotherapeutic agents. Accumulating evidence has suggested that the detection of HMGA2 can be used as a routine procedure in clinical tumour analysis.

Testicular germ cell tumor: a comprehensive review

Testicular tumors are the most common tumors in adolescent and young men and germ cell tumors (TGCTs) account for most of all testicular cancers. Increasing incidence of TGCTs among males provides strong motivation to understand its biological and genetic basis. Gains of chromosome arm 12p and aneuploidy are nearly universal in TGCTs, but TGCTs have low point mutation rate. It is thought that TGCTs develop from premalignant intratubular germ cell neoplasia that is believed to arise from the failure of normal maturation of gonocytes during fetal or postnatal development. Progression toward invasive TGCTs (seminoma and nonseminoma) then occurs after puberty. Both inherited genetic factors and environmental risk factors emerge as important contributors to TGCT susceptibility. Genome-wide association studies have so far identified more than 30 risk loci for TGCTs, suggesting that a polygenic model fits better with the genetic landscape of the disease. Despite high cure rates because of its particular sensitivity to platinum-based chemotherapy, exploration of mechanisms underlying the occurrence, progression, metastasis, recurrence, chemotherapeutic resistance, early diagnosis and optional clinical therapeutics without long-term side effects are urgently needed to reduce the cancer burden in this underserved age group. Herein, we present an up-to-date review on clinical challenges, origin and progression, risk factors, TGCT mouse models, serum diagnostic markers, resistance mechanisms, miRNA regulation, and database resources of TGCTs. We appeal that more attention should be paid to the basic research and clinical diagnosis and treatment of TGCTs.

Chemotherapy-Induced Depletion of OCT4-Positive Cancer Stem Cells in a Mouse Model of Malignant Testicular Cancer

Testicular germ cell tumors (TGCTs) are among the most responsive solid cancers to conventional chemotherapy. To elucidate the underlying mechanisms, we developed a mouse TGCT model featuring germ cell-specific Kras activation and Pten inactivation. The resulting mice developed malignant, metastatic TGCTs composed of teratoma and embryonal carcinoma, the latter of which exhibited stem cell characteristics, including expression of the pluripotency factor OCT4. Consistent with epidemiological data linking human testicular cancer risk to in utero exposures, embryonic germ cells were susceptible to malignant transformation, whereas adult germ cells underwent apoptosis in response to the same oncogenic events. Treatment of tumor-bearing mice with genotoxic chemotherapy not only prolonged survival and reduced tumor size but also selectively eliminated the OCT4-positive cancer stem cells. We conclude that the chemosensitivity of TGCTs derives from the sensitivity of their cancer stem cells to DNA-damaging chemotherapy.

MAPK15 upregulation promotes cell proliferation and prevents DNA damage in male germ cell tumors

Germ cell tumors (GCT) are the most common malignancies in males between 15 and 35 years of age. Despite the high cure rate, achieved through chemotherapy and/or surgery, the molecular basis of GCT etiology is still largely obscure. Here, we show a positive correlation between MAPK15 (ERK8; ERK7) expression and specific GCT subtypes, with the highest levels found in the aggressive embryonal carcinomas (EC). Indeed, in corresponding cellular models for EC, MAPK15 enhanced tumorigenicity in vivo and promoted cell proliferation in vitro, supporting a role for this kinase in human GCT. At molecular level, we demonstrated that endogenous MAPK15 is necessary to sustain cell cycle progression of EC cells, by limiting p53 activation and preventing the triggering of p53-dependent mechanisms resulting in cell cycle arrest.

To understand MAPK15-dependent mechanisms impinging on p53 activation, we demonstrate that this kinase efficiently protects cells from DNA damage. Moreover, we show that the ability of MAPK15 to control the autophagic process is necessary for basal management of DNA damage and for tumor formation controlled by the kinase.

In conclusion, our findings suggest that MAPK15 overexpression may contribute to the malignant transformation of germ cells by controlling a “stress support” autophagic pathway, able to prevent DNA damage and the consequent activation of the p53 tumor suppressor. Moreover, in light of these results, MAPK15-specific inhibitors might represent new tools to enhance the therapeutic index of cytotoxic therapy in GCT treatment, and to increase the sensitivity to DNA-damaging drugs in other chemotherapy-resistant human tumors.

High RNA-Binding Motif Protein 3 (RBM3) Expression is Independently Associated with Prolonged Overall Survival in Intestinal-Type Gastric Cancer

Background

High expression of the RNA-binding motif protein 3 (RBM3) has previously been described as a favorable clinicopathological factor in several cancers, including ovarian cancer, colorectal cancer, prostate cancer, and breast cancer. The aim of this study was to examine the prognostic implications of RBM3 expression in gastric cancer.

Material/Methods

Immunohistochemical analysis of RBM3 expression from 123 patients showed that upregulated RBM3 was mainly found in intestinal-type (n=78, case=59) cancer compared to diffuse-type (n=15, case=8) and mixed-type (n=30, case=17). There were no significant differences in RBM3 expression in subgroups of clinicopathological parameters. RBM3 expression was strongly associated with p53 but not with Ki-67. Cox univariate analysis revealed that high RBM3 expression was closely associated with prolonged overall survival time (HR 0.504, 95% CI: 0.300–0.845, P=0.009). Multivariate analysis remained supporting these associations when adjusted for age, sex, tumor size, differentiation grade, TNM stage, lymphatic invasion, and Ki-67 and p53 expression (HR 0.541, 95% CI: 0.308–0.952, P=0.033), where Lauren grade was not included. Lauren grade was the only factor with independent prognostic significance in a model adjusted for all factors. These results were confirmed by Kaplan-Meier analysis.

Results

Therefore, together with the upregulated RBM3 expression observed in intestinal-type of Lauren grade, we suggest that upregulation of RBM3 is partially responsible for the favorable overall survival in cases with intestinal Lauren grade, which is demonstrated by the box diagram and Kaplan-Meier analysis. Our results showed that high RBM3 expression in gastric cancer is mainly found in intestinal-type of Lauren grade and is associated with longer overall survival time.

Conclusion

We found that RBM3 is a potential biomarker of good prognosis and deserves further validation.

Investigational targeted therapies for the treatment of testicular germ cell tumors

INTRODUCTION

Germ cell tumors (GCTs) are the most common malignancy among men aged between 15 to 45. Despite high cure rates of >90% over all GCTs, 3 to 5% of patients will still die of platinum-refractory disease. New systemic treatment options are needed to improve treatment success in this challenging setting.

AREAS COVERED

To review targeted treatment options and preclinical developments in platinum-refractory GCTs, a comprehensive literature search of PubMed, Medline and scientific meeting abstracts on published clinical trials and reports on molecularly targeted approaches was conducted. Outcomes of platinum-refractory disease and of patients failing high-dose chemotherapy remain poor. Currently, no molecularly targeted treatment has shown clinically meaningful activity in unselected patient populations in clinical trials, but individual patients may achieve short-lived objective responses by treatment with sunitinib, brentuximab vedotin or imatinib. Targeted trials based on molecular selection of patients have not yet been performed.

EXPERT OPINION

The limited activity of targeted agents in refractory GCT is disappointing. Assessment of druggable biomarkers and marker-stratified treatment may help individual patients, but is largely lacking. The low incidence and high curability of GCTs make the design of larger clinical trials difficult. The potential of novel agents, i.e. immune-checkpoint inhibitors, remains to be elucidated.

Ex vivo culture of human fetal gonads: manipulation of meiosis signalling by retinoic acid treatment disrupts testis development

STUDY QUESTION

What are the effects of experimentally manipulating meiosis signalling by addition of retinoic acid (RA) in cultured human fetal gonads?

SUMMARY ANSWER

RA-treatment accelerated meiotic entry in cultured fetal ovary samples, while addition of RA resulted in a dysgenetic gonadal phenotype in fetal testis cultures.

WHAT IS KNOWN ALREADY

One of the first manifestations of sex differentiation is the initiation of meiosis in fetal ovaries. In contrast, meiotic entry is actively prevented in the fetal testis at this developmental time-point. It has previously been shown that RA-treatment mediates initiation of meiosis in human fetal ovary ex vivo.

STUDY DESIGN, SIZE, DURATION

This was a controlled ex vivo study of human fetal gonads treated with RA in 'hanging-drop' tissue cultures. The applied experimental set-up preserves germ cell-somatic niche interactions and the investigated outcomes included tissue integrity and morphology, cell proliferation and survival and the expression of markers of meiosis and sex differentiation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Tissue from 24 first trimester human fetuses was included in this study, all from elective terminations at gestational week (GW) 7-12. Gonads were cultured for 2 weeks with and without addition of 1 µM RA. Samples were subsequently formalin-fixed and investigated by immunohistochemistry and cell counting. Proteins investigated and quantified included; octamer-binding transcription factor 4 (OCT4), transcription factor AP-2 gamma (AP2γ) (embryonic germ cell markers), SRY (sex determining region Y)-box 9 (SOX9), anti-Müllerian hormone (AMH) (immature Sertoli cell markers), COUP transcription factor 2 (COUP-TFII) (marker of interstitial cells), forkhead box L2 (FOXL2) (granulosa cell marker), H2A histone family, member X (γH2AX) (meiosis marker), doublesex and mab-3 related transcription factor 1 (DMRT1) (meiosis regulator), cleaved poly ADP ribose polymerase (PARP), cleaved Caspase 3 (apoptosis markers) and Ki-67 antigen (Ki-67) (proliferation marker). Also, proliferation was determined using a 5'-bromo-2'-deoxyuridine (BrdU) incorporation assay.

MAIN RESULTS AND THE ROLE OF CHANCE

A novel ex vivo 'hanging-drop' culture model for human fetal gonads was successfully established. Continued proliferation of cells without signs of increased apoptosis was observed after 2 weeks of culture. In cultured fetal ovaries treated with RA, an increased number of meiotic germ cells (P < 0.05) and DMRT1-positive oogonia initiating meiosis (P < 0.05) was observed, which is in agreement with a previous study. In fetal testes, RA-treatment resulted in a decreased number of gonocytes (P < 0.05), a reduced percentage of proliferating gonocytes (P < 0.05), altered expression pattern of the somatic cell markers AMH and COUP-TFII, as well as disrupted seminiferous cord structure and testis morphology.

LIMITATIONS, REASONS FOR CAUTION

The number of samples included in this study was relatively small due to the limited availability of human fetal tissue.

WIDER IMPLICATIONS OF THE FINDINGS

The hanging-drop culture, similarly to other organ culture approaches, allows studies of germ cell-somatic niche interactions and determination of effects after manipulating specific signalling pathways. Our novel finding of disrupted fetal testis development after treatment with RA indicates that abnormal meiosis regulation can potentially cause gonadal dysgenesis. Further studies will elucidate the exact mechanisms and timing of observed effects.

STUDY FUNDING/COMPETING INTERESTS

This work was supported in part by an ESPE Research Fellowship, sponsored by Novo Nordisk A/S to A.Jø. Additional funding for this project was obtained from The Research Council of the Capital Region of Denmark (E.R.-D.M.), The Research Fund at Rigshospitalet (A.Ju. and J.E.N.), Familien Erichssens Fund (A.Jø.), Dagmar Marshalls Fund (A.Jø.) and Aase & Ejnar Danielsens Fund (A.Jø.). The authors have no conflicts of interest.

Low RBM3 protein expression correlates with clinical stage, prognostic classification and increased risk of treatment failure in testicular non-seminomatous germ cell cancer

Background

Expression of the RNA-binding motif protein 3 (RBM3) has been shown to correlate with favourable clinicopathological parameters and prognosis in several cancer diseases. The aim of this study was to examine the expression and prognostic ability of RBM3 in patients with testicular non-seminomatous germ cell tumours (NSGCT).

Patients and Methods

Immunohistochemical RBM3 expression was analysed in tissue microarrays with tumours from 206 patients. Chi-square test was applied to analyze associations between RBM3 expression and clinicopathological parameters. Kaplan-Meier analysis was used to assess the impact of RBM3 expression on cancer-specific survival (CSS) and failure-free survival (FFS). Cox regression proportional hazards models were used to estimate the relative risk for failure.

Results

In the entire cohort, there was a significant association between clinical stage (p=0.044) and RBM3 expression. Weak RBM3 expression correlated with a significantly reduced FFS [79.3% versus 90.4% (p=0.019)] and CSS [87.5% versus 97.3% (p=0.047)]. For patients with metastatic disease (n = 88), significant associations were found between RBM3 expression and IGCCC group (p=0.007). The FFS was significantly inferior for patients with low tumour-specific RBM3 expression [59.3% versus 79.0% (p=0.013)], and this association remained significant in a multivariable model for patients with metastatic disease (HR=3.67; 95% CI 1.14, 11.89).

Conclusion

Low RBM3 expression is an independent predictor of treatment failure in metastatic NSGCT, in relation to the prognostic factors included in the International Germ Cell Consensus Classification (IGCCC). These findings suggest that RBM3 may be a potential biomarker for treatment stratification in patients with metastatic non-seminomatous germ cell tumours, and therefore merit further validation.

Cisplatin resistance in germ cell tumours: models and mechanisms

Recent years have led to a better understanding of the mechanisms underlying cisplatin response and resistance in germ cell tumours (GCT), and several promising targets have been identified. Two main mechanisms of the responsiveness to DNA damaging agents have been postulated. Firstly, GCT readily activate a DNA damage response, but show deficits in several damage repair pathways. In particular, they have been found to have defects in interstrand crosslink repair and in homologous recombination (HR). Secondly, GCT, especially embryonal carcinoma (EC) cells, show a hypersensitive apoptotic response to DNA damage, which activates p53, and leads to up-regulation of the pro-apoptotic factors Noxa, Puma and Fas in non-resistant EC. These cells fail to activate p21 which induces a G1/S arrest, but accumulate in G2/M phase. In the absence of functional p53, family members like p73 and GTAp63 might be important in initiating this response. Mechanisms involved in cisplatin resistance are as follows: down-regulation of Oct4 (e.g. as a result of hypoxia, treatment with retinoic acid or exposure to cisplatin) and failure to induce Puma and Noxa; changes in the expression levels of micro-RNAs such as miR-17/-106b, miR-302a, or miR-371 to -373; elevated levels of MDM2 and cytoplasmic translocation of p21 by phosphorylation; and activation of the PDGFRβ/PI3K/pAKT pathway. Several approaches to overcome resistance have been successfully examined in vitro and in vivo, including PARP inhibitors, especially in cells showing deficient HR-repair; stabilization of p53 using nutlin-3; inhibition of several components of the PI3K/pAKT pathway using small molecules; and DNA demethylation by 5-azacytidine or 5-aza-deoxy-cytidine, among others. Many of these substances deserve further exploration, alone or in combination with DNA damaging agents, and the most promising approaches should be taken forward to clinical testing. Targeted therapy based on mechanistic insights holds the promise to turn cisplatin-resistant GCT into a curable disease.

Patterns of DNA damage response in intracranial germ cell tumors versus glioblastomas reflect cell of origin rather than brain environment: implications for the anti-tumor barrier concept and treatment

The DNA damage response (DDR) machinery becomes commonly activated in response to oncogenes and during early stages of development of solid malignancies, with an exception of testicular germ cell tumors (TGCTs). The active DDR signaling evokes cell death or senescence but this anti-tumor barrier can be breached by defects in DDR factors, such as the ATM-Chk2-p53 pathway, thereby allowing tumor progression. The DDR barrier is strongly activated in brain tumors, particularly gliomas, due to oxidative damage and replication stress. Here, we took advantage of rare human primary intracranial germ cell tumors (PIGCTs), to address the roles of cell-intrinsic factors including cell of origin, versus local tissue environment, in the constitutive DDR activation in vivo. Immunohistochemical analysis of 7 biomarkers on a series of 21 PIGCTs (germinomas and other subtypes), 20 normal brain specimens and 20 glioblastomas, revealed the following: i) The overall DDR signaling (γH2AX) and activation of the ATM-Chk2-p53 pathway were very low among the PIGCTs, reminiscent of TGCTs, and contrasting sharply with strong DDR activation in glioblastomas; ii) Except for one case of embryonal carcinoma, there were no clear aberrations in the ATM-Chk2-p53 pathway components among the PIGCT cohort; iii) Subsets of PIGCTs showed unusual cytosolic localization of Chk2 and/or ATM. Collectively, these results show that PIGCTs mimic the DDR activation patterns of their gonadal germ cell tumor counterparts, rather than the brain tumors with which they share the tissue environment. Hence cell-intrinsic factors and cell of origin dictate the extent of DDR barrier activation and also the ensuing pressure to select for DDR defects. Our data provide conceptually important insights into the role of DNA damage checkpoints in intracranial tumorigenesis, with implications for the differential biological responses of diverse tumor types to endogenous stress as well as to genotoxic treatments such as ionizing radiation or chemotherapy.

Unravelling mechanisms of cisplatin sensitivity and resistance in testicular cancer

Testicular cancer is the most frequent solid malignant tumour type in men 20-40 years of age. At the time of diagnosis up to 50% of the patients suffer from metastatic disease. In contrast to most other metastatic solid tumours, the majority of metastatic testicular cancer patients can be cured with highly effective cisplatin-based chemotherapy. This review aims to summarise the current knowledge on response to chemotherapy and the biological basis of cisplatin-induced apoptosis in testicular cancer. The frequent presence of wild-type TP53 and the low levels of p53 in complex with the p53 negative feed-back regulator MDM2 contribute to cisplatin sensitivity. Moreover, the high levels of the pluripotency regulator Oct4 and as a consequence of Oct4 expression high levels of miR-17/106b seed family and pro-apoptotic Noxa and the low levels of cytoplasmic p21 (WAF1/Cip1) appear to be causative for the exquisite sensitivity to cisplatin-based therapy of testicular cancer. However, resistance of testicular cancer to cisplatin-based therapy does occur and can be mediated through aberrant levels of the above mentioned key players. Drugs targeting these key players showed, at least pre-clinically, a sensitising effect to cisplatin treatment. Further clinical development of such treatment strategies will lead to new treatment options for platinum-resistant testicular cancers.

Critical role of CCDC6 in the neoplastic growth of testicular germ cell tumors

Background

DNA damage response has been clearly described as an anti-cancer barrier in early human tumorigenesis. Moreover, interestingly, testicular germ cell tumors (TGCTs) have been reported to lack the DNA Damage Response (DDR) pathway activation.

CCDC6 is a pro-apoptotic phosphoprotein substrate of the kinase ataxia telangectasia mutated (ATM) able to sustain DNA damage checkpoint in response to genotoxic stress and is commonly rearranged in malignancies upon fusion with different partners.

In our study we sought to determine whether CCDC6 could have a role in the patho-genesis of testicular germ cell tumors.

Methods

To achieve this aim, analysis for CCDC6 expression has been evaluated on serial sections of the mouse testis by immunohistochemistry and on separate populations of murine testicular cells by western blot. Next, the resistance to DNA damage-induced apoptosis and the production of reactive oxygen species has been investigated in GC1 cells, derived from immortalized type B murine germ cells, following CCDC6 silencing. Finally, the CCDC6 expression in normal human testicular cells, in Intratubular Germ Cell Neoplasia Unclassified (IGCNU), in a large series of male germ cell tumours and in the unique human seminoma TCam2 cell line has been evaluated by immunohistochemistry and by Western Blot analyses.

Results

The analysis of the CCDC6 expression revealed its presence in Sertoli cells and in spermatogonial cells. CCDC6 loss was the most consistent feature among the primary tumours and TCam2 cells. Interestingly, following treatment with low doses of H₂O₂, the silencing of CCDC6 in GC1 cells caused a decrease in the oxidized form of cytochrome c and low detection of Bad, PARP-1 and Caspase 3 proteins. Moreover, in the silenced cells, upon oxidative damage, the cell viability was protected, the γH2AX activation was impaired and the Reactive Oxygen Species (ROS) release was decreased.

Conclusions

Therefore, our results suggest that the loss of CCDC6 could aid the spermatogonial cells to be part of a pro-survival pathway that helps to evade the toxic effects of endogenous oxidants and contributes to testicular neoplastic growth.

Decreased expression of RNA-binding motif protein 3 correlates with tumour progression and poor prognosis in urothelial bladder cancer

Background

Low nuclear expression of the RNA-binding motif protein 3 (RBM3) has previously been found to be associated with poor prognosis in several cancer forms e.g. breast, ovarian, colorectal, prostate cancer and malignant melanoma. The aim of this study was to examine the prognostic impact of RBM3 expression in urinary bladder cancer.

Methods

Immunohistochemical RBM3 expression was examined in tumours from 343 patients with urothelial bladder cancer. Chi-square and Spearman’s correlation tests were applied to explore associations between RBM3 expression and clinicopathological characteristics. The impact of RBM3 expression on disease-specific survival (DSS), 5-year overall survival (OS) and progression-free survival (PFS) was assessed by Kaplan-Meier analysis and Cox proportional hazards modelling.

Results

Reduced nuclear RBM3 expression was significantly associated with more advanced tumour (T) stage (p <0.001) and high grade tumours (p=0.004). Negative RBM3 expression was associated with a significantly shorter DSS (HR=2.55; 95% CI 1.68-3.86)) and 5-year OS (HR=2.10; 95% CI 1.56-2.82), also in multivariable analysis (HR=1.65; 95% CI 1.07-2.53 for DSS and HR=1.54; 95% CI 1.13-2.10 for 5-year OS). In patients with Ta and T1 tumours expressing reduced RBM3 levels, Kaplan-Meier analysis revealed a significantly shorter PFS (p=0.048) and 5-year OS (p=0.006).

Conclusion

Loss of RBM3 expression is associated with clinically more aggressive tumours and an independent factor of poor prognosis in patients with urothelial bladder cancer and a potentially useful biomarker for treatment stratification and surveillance of disease progression.

Types, causes, detection and repair of DNA fragmentation in animal and human sperm cells

Concentration, motility and morphology are parameters commonly used to determine the fertilization potential of an ejaculate. These parameters give a general view on the quality of sperm but do not provide information about one of the most important components of the reproductive outcome: DNA. Either single or double DNA strand breaks can set the difference between fertile and infertile males. Sperm DNA fragmentation can be caused by intrinsic factors like abortive apoptosis, deficiencies in recombination, protamine imbalances or oxidative stress. Damage can also occur due to extrinsic factors such as storage temperatures, extenders, handling conditions, time after ejaculation, infections and reaction to medicines or post-testicular oxidative stress, among others. Two singular characteristics differentiate sperm from somatic cells: Protamination and absence of DNA repair. DNA repair in sperm is terminated as transcription and translation stops post-spermiogenesis, so these cells have no mechanism to repair the damage occurred during their transit through the epididymis and post-ejaculation. Oocytes and early embryos have been shown to repair sperm DNA damage, so the effect of sperm DNA fragmentation depends on the combined effects of sperm chromatin damage and the capacity of the oocyte to repair it. In this contribution we review some of these issues.

High MCM3 expression is an independent biomarker of poor prognosis and correlates with reduced RBM3 expression in a prospective cohort of malignant melanoma

Background

Malignant melanoma is the most lethal form of skin cancer with a variable clinical course even in patients with thin melanomas and localized disease. Despite increasing insights into melanoma biology, no prognostic biomarkers have yet been incorporated into clinical protocols. Reduced expression of the RNA binding motif protein 3 (RBM3) has been shown to correlate with tumour progression and poor prognosis in melanoma and several other cancer forms. In ovarian cancer, an inverse association was found between expression of RBM3 and the minichromosome maintenance 3 (MCM3) gene and protein. In melanoma, gene expression analysis and immunohistochemical validation has uncovered MCM3 as a putative prognostic biomarker. The aim of the present study was to examine the associations of MCM3 expression with clinical outcome and RBM3 expression in a prospective, population-based cohort of melanoma.

Methods

Immunohistochemical MCM3 expression was examined in 224 incident cases of primary melanoma from the Malmö Diet and Cancer Study, previously analysed for RBM3 expression. Spearman´s Rho and Chi-Square tests were used to explore correlations between MCM3 expression, clinicopathological factors, and expression of RBM3 and Ki67. Kaplan Meier analysis, the log rank test, and univariable and multivariable Cox proportional hazards modelling were used to assess the impact of MCM3 expression on disease-free survival (DFS) and melanoma-specific survival (MSS).

Results

High MCM3 expression was significantly associated with unfavourable clinicopathological features and high Ki67 expression. A significant inverse correlation was seen between expression of MCM3 and RBM3 (p = 0.025). High MCM3 expression was associated with a reduced DFS (HR = 5.62) and MSS (HR = 6.03), and these associations remained significant in multivariable analysis, adjusted for all other factors (HR = 5.01 for DFS and HR = 4.96 for MSS). RBM3 expression remained an independent prognostic factor for MSS but not DFS in the multivariable model.

Conclusions

These findings provide validation of the utility of MCM3 expression as an independent biomarker for prognostication of patients with primary melanoma. Moreover, the inverse association and prognostic impact of MCM3 and RBM3 expression indicate a possible interaction of these proteins in melanoma progression, the functional basis for which merits further study.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1814908129755401

High RBM3 expression in prostate cancer independently predicts a reduced risk of biochemical recurrence and disease progression

BACKGROUND

High expression of the RNA-binding protein RBM3 has previously been found to be associated with good prognosis in breast cancer, ovarian cancer, malignant melanoma and colorectal cancer. The aim of this study was to examine the prognostic impact of immunohistochemical RBM3 expression in prostate cancer.

FINDINGS

Immunohistochemical RBM3 expression was examined in a tissue microarray with malignant and benign prostatic specimens from 88 patients treated with radical prostatectomy for localized disease. While rarely expressed in benign prostate gland epithelium, RBM3 was found to be up-regulated in prostate intraepithelial neoplasia and present in various fractions and intensities in invasive prostate cancer. High nuclear RBM3 expression was significantly associated with a prolonged time to biochemical recurrence (BCR) (HR 0.56, 95% CI: 0.34-0.93, p = 0.024) and clinical progression (HR 0.09, 95% CI: 0.01-0.71, p = 0.021). These associations remained significant in multivariate analysis, adjusted for preoperative PSA level in blood, pathological Gleason score and presence or absence of extracapsular extension, seminal vesicle invasion and positive surgical margin (HR 0.41, 95% CI: 0.19-0.89, p = 0.024 for BCR and HR 0.06, 95% CI: 0.01-0.50, p = 0.009 for clinical progression).

CONCLUSION

Our results demonstrate that high nuclear expression of RBM3 in prostate cancer is associated with a prolonged time to disease progression and, thus, a potential biomarker of favourable prognosis. The value of RBM3 for prognostication, treatment stratification and follow-up of prostate cancer patients should be further validated in larger studies.

Carcinoma in situ testis displays permissive chromatin modifications similar to immature foetal germ cells

Background:

The majority of testicular germ cell cancers develop through a pre-invasive carcinoma in situ (CIS) stage. The CIS cell is a neoplastic counterpart of foetal germ cells. During their development, foetal germ cells undergo extensive and essential epigenetic modifications, but little is known about epigenetic patterns in CIS cells.

Methods:

Immunohistochemistry was used to investigate epigenetic patterns in CIS, germ cell tumours, normal adult and foetal testicular tissue.

Results:

CIS cells show low levels of DNA methylation and repressive histone modifications H3K9me2 and H3K27me3, but high levels of H3K9 acetylation, H3K4 methylation and H2A.Z, which all are associated with an activated and accessible chromatin structure. Collectively this renders a permissive chromatin structure and in accordance high levels of RNA polymerase II activity and proliferation (Ki-67 and mitotic index) is observed in CIS cells. Epigenetic patterns similar to that of CIS cells were observed in human gonocytes present within sex cords in foetal testes but correspond to migrating primordial germ cell in mice. Development of overt tumours involves epigenetic repression of the chromatin.

Conclusion:

CIS cells have a permissive and foetal-like chromatin structure, which is associated with a high transcriptional and proliferative activity, likely empowering neoplastic transformation. Developmental epigenetic cues in foetal germ cells are substantially different between humans and mice.

The DNA-damage response in human biology and disease

The prime objective for every life form is to deliver its genetic material, intact and unchanged, to the next generation. This must be achieved despite constant assaults by endogenous and environmental agents on the DNA. To counter this threat, life has evolved several systems to detect DNA damage, signal its presence and mediate its repair. Such responses, which have an impact on a wide range of cellular events, are biologically significant because they prevent diverse human diseases. Our improving understanding of DNA-damage responses is providing new avenues for disease management.

Impaired DNA damage response--an Achilles' heel sensitizing cancer to chemotherapy and radiotherapy

Despite the progress in targeting particular molecular abnormalities specific to different cancers (targeted therapy), chemo- and radiotherapies are still the most effective of all anticancer modalities. Induction of DNA damage and inhibition of cell proliferation are the objects of most chemotherapeutic agents and radiation. Their effectiveness was initially thought to be due to the high rate of proliferation of cancer cells. However, normal cell proliferation rate in some tissues often exceeds that of curable tumors. Most tumors have impaired DNA damage response (DDR) and the evidence is forthcoming that this confers sensitivity to chemo- or radiotherapy. DDR is a complex set of events which elicits a plethora of molecular interactions engaging signaling pathways designed to: (a) halt cell cycle progression and division to prevent transfer of DNA damage to progeny cells; (b) increase the accessibility of the damaged sites to the DNA repair machinery; (c) engage DNA repair mechanisms and (d) activate the apoptotic pathway when DNA cannot be successfully repaired. A defective DDR makes cancer cells unable to effectively stop cell cycle progression, engage in DNA repair and/or trigger the apoptotic program when treated with DNA damaging drugs. With continued exposure to the drug, such cells accumulate DNA damage which leads to their reproductive death that may have features of cell senescence. Cancers with nonfunctional BRCA1 and BRCA2 are particularly sensitive to combined treatment with DNA damaging drugs and inhibitors of poly(ADP-ribose) polymerase. Antitumor strategies are being designed to treat cancers having particular defects in their DDR, concurrent with protecting normal cells.

Human testicular (non)seminomatous germ cell tumours: the clinical implications of recent pathobiological insights

Human germ cell tumours (GCTs) comprise several types of neoplasias with different pathogeneses and clinical behaviours. A classification into five subtypes has been proposed. Here, the so-called type II testicular GCTs (TGCTs), ie the seminomas and non-seminomas, will be reviewed with emphasis on pathogenesis and clinical implications. Various risk factors have been identified that define subpopulations of men who are amenable to early diagnosis. TGCTs are omnipotent, able to generate all differentiation lineages, both embryonic and extra-embryonic, as well as the germ cell lineage itself. The precursor lesion, composed of primordial germ cells/gonocytes, is referred to as carcinoma in situ of the testis (CIS) and gonadoblastoma of the dysgenetic gonad. These pre-malignant cells retain embryonic characteristics, which probably explains the unique responsiveness of the derived tumours to DNA-damaging agents. Development of CIS and gonadoblastoma is crucially dependent on the micro-environment created by Sertoli cells in the testis, and granulosa cells in the dysgenetic gonad. OCT3/4 has high sensitivity and specificity for CIS/gonadoblastoma, seminoma, and embryonal carcinoma, and is useful for the detection of CIS cells in semen, thus a promising tool for non-invasive screening. Overdiagnosis of CIS due to germ cell maturation delay can be avoided using immunohistochemical detection of stem cell factor (SCF). Immunohistochemistry is helpful in making the distinction between seminoma and embryonal carcinoma, especially SOX17 and SOX2. The different non-seminomatous histological elements can be recognized using various markers, such as AFP and hCG, while others need confirmation. The value of micro-satellite instability as well as BRAF mutations in predicting treatment resistance needs validation in prospective trials. The availability of representative cell lines, both for seminoma and for embryonal carcinoma, allows mechanistic studies into the initiation and progression of this disease.

Microsatellite instability, mismatch repair deficiency, and BRAF mutation in treatment-resistant germ cell tumors

PURPOSE

Mismatch repair (MMR) deficiency and microsatellite instability (MSI) are associated with cisplatin resistance in human germ cell tumors (GCTs). BRAF mutation (V600E) is found in MSI colorectal cancers. The role of RAS/RAF pathway mutations in GCT treatment response is unknown.

PATIENTS AND METHODS

Two patient cohorts were investigated: 100 control GCTs (50 seminomas and 50 nonseminomas) and 35 cisplatin-based chemotherapy-resistant GCTs. MMR proteins were analyzed by immunohistochemistry, and eight microsatellite loci were examined for MSI. Tumors were assessed for specific BRAF and KRAS mutations.

RESULTS

Resistant tumors showed a higher incidence of MSI than controls: 26% versus 0% in two or more loci (P < .0001). All resistant tumors were wild-type KRAS, and two controls (2%) contained a KRAS mutation. There was a significantly higher incidence of BRAF V600E mutation in resistant tumors compared with controls: 26% versus 1% (P < .0001). BRAF mutations were highly correlated with MSI (P = .006), and MSI and mutated BRAF were correlated with weak or absent staining for hMLH1 (P = .017 and P = .008). Low or absent staining of hMLH1 was correlated with promoter hypermethylation (P < .001). Tumors lacking expression of hMLH1 or MSH6 were significantly more frequent in resistant GCTs than in controls (P = .001 and 0.0036, respectively). Within the subgroup of resistant tumors, patients with MSI showed a trend to longer progression-free survival (P = .068).

CONCLUSION

We report for the first time a correlation between a gene mutation--BRAF V600E--and cisplatin resistance in nonseminomatous GCTs. Furthermore, a correlation between MMR deficiency, MSI, and treatment failure is confirmed.

Molecular Pathology of the Genitourinary Tract: Molecular Pathology of Kidney and Testes

With the advent of newer molecular technologies, our knowledge of cellular mechanisms with tumors of the kidney and testis has grown exponentially. Molecular technologies have led to better understanding of interplay between the von Hippel-Lindau gene and angiogenic cytokines in renal cancer and isochromosome 12p in testicular neoplasms. The result has been development of antiangiogenic-targeted therapy within recent years that has become the mainstay treatment for metastatic renal cell cancer. In the near future, classification and diagnosis of renal and testicular tumors through morphologic analysis will be supplemented by molecular information correlating to prognosis and targeted therapy. This article outlines tumor molecular pathology of the kidney and testis encompassing current genomic, epigenomic, and proteonomic findings.

Endogenous DNA damage and testicular germ cell tumors

Testicular germ cell tumors are comprised of two histologic groups, seminomas and non-seminomas. We postulated that the possible divergent pathogeneses of these histologies may be partially explained by variable levels of net endogenous DNA damage. To test our hypothesis, we conducted a case-case analysis of 51 seminoma and 61 non-seminoma patients using data and specimens from the Familial Testicular Cancer study and the U.S. Radiologic Technologists cohort. A lymphoblastoid cell line was cultured for each patient and the alkaline comet assay was used to determine four parameters: tail DNA, tail length, comet distributed moment (CDM) and Olive tail moment (OTM). Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using logistic regression. Values for tail length, tail DNA, CDM and OTM were modelled as categorical variables using the 50th and 75th percentiles of the seminoma group. Tail DNA was significantly associated with non-seminoma compared with seminoma (OR(50th percentile) = 3.31, 95% CI: 1.00, 10.98; OR(75th percentile) = 3.71, 95% CI: 1.04, 13.20; p for trend = 0.039). OTM exhibited similar, albeit statistically non-significant, risk estimates (OR(50th percentile) = 2.27, 95% CI: 0.75, 6.87; OR(75th percentile) = 2.40, 95% CI: 0.75, 7.71; p for trend = 0.12) whereas tail length and CDM showed no association. In conclusion, the results for tail DNA and OTM indicate that net endogenous levels are higher in patients who develop non-seminoma compared with seminoma. This may partly explain the more aggressive biology and younger age-of-onset of this histologic subgroup compared with the relatively less aggressive, later-onset seminoma.