The downside of 'inappropriate messaging': new insight into the development of testicular germ cell tumours in young men?

Overexpression of melanoma-associated antigen A2 has a clinical significance in embryonal carcinoma and is associated with tumor progression

INTRODUCTION

Melanoma-associated antigen A2 (MAGE-A2) is a member of the cancer-testis antigen family differentially overexpressed in a variety of malignancies and is associated with tumor development. However, clinical significance and prognostic value of MAGE-A2 in different histological subtypes of testicular germ cell tumors (TGCTs) have not been explored.

MATERIALS AND METHODS

Here, we aimed to investigate the clinical significance and prognostic impact of MAGE-A2 expression in TGCTs compared to benign tumors as well as adjacent normal tissues and then between seminomas and non-seminomas groups using immunohistochemistry on tissue microarrays.

RESULTS

The results indicated a statistically significant difference between overexpression of MAGE-A2 and histological subtypes of TGCTs. A statistically significant association was found between a high level of nuclear expression of MAGE-A2 protein and advanced pT stage (P = 0.022), vascular invasion (P = 0.037), as well as involvement of rete testis (P = 0.022) in embryonal carcinomas. Increased nuclear expression of MAGE-A2 was observed to be associated with more aggressive behaviors and tumor progression rather than cytoplasmic expression in these cases. Further, high level nuclear expression of MAGE-A2 had shorter disease-specific survival (DSS) or progression-free survival (PFS) compared to patients with moderate and low expression of MAGE-A2, however, without a statistically significant association.

CONCLUSION

Our results confirm that increased nuclear expression of MAGE-A2 has a clinical significance in embryonal carcinomas and is associated with progression of disease. Moreover, MAGE-A2 may act as a potential predictive biomarker for the prognosis in embryonal carcinomas if follow-up period becomes longer. Further investigations for the biological function of MAGE-A2 are required in future studies.

DMRT1 repression using a novel approach to genetic manipulation induces testicular dysgenesis in human fetal gonads

STUDY QUESTION

Does loss of DMRT1 in human fetal testis alter testicular development and result in testicular dysgenesis?

SUMMARY ANSWER

DMRT1 repression in human fetal testis alters the expression of key testicular and ovarian determining genes, and leads to focal testicular dysgenesis.

WHAT IS KNOWN ALREADY

Testicular dysgenesis syndrome (TDS) is associated with common testicular disorders in young men, but its etiology is unknown. DMRT1 has been shown to play a role in the regulation of sex differentiation in the vertebrate gonad. Downregulation of DMRT1 in male mice results in trans-differentiation of Sertoli cells into granulosa (FOXL2⁺) cells resulting in an ovarian gonadal phenotype.

STUDY DESIGN, SIZE, DURATION

To determine the effect of DMRT1 repression on human fetal testes, we developed a novel system for genetic manipulation, which utilizes a Lentivral delivered miRNA during short-term in vitro culture (2 weeks). A long-term (4–6 weeks) ex vivo xenograft model was used to determine the subsequent effects of DMRT1 repression on testicular development and maintenance. We included first and second-trimester testis tissue (8–20 weeks gestation; n = 12) in the study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human fetal testes were cultured in vitro and exposed to either of two DMRT1 miRNAs (miR536, miR641), or to scrambled control miRNA, for 24 h. This was followed by a further 14 days of culture (n = 3–4), or xenografting (n = 5) into immunocompromised mice for 4–6 weeks. Tissues were analyzed by histology, immunohistochemistry, immunofluorescence and quantitative RT-PCR. Endpoints included histological evaluation of seminiferous cord integrity, mRNA expression of testicular, ovarian and germ cell genes, and assessment of cell number and protein expression for proliferation, apoptosis and pluripotency factors. Statistical analysis was performed using a linear mixed effect model.

MAIN RESULTS AND THE ROLE OF CHANCE

DMRT1 repression (miR536/miR641) resulted in a loss of DMRT1 protein expression in a sub-population of Sertoli cells of first trimester (8–11 weeks gestation) human fetal testis; however, this did not affect the completion of seminiferous cord formation or morphological appearance. In second-trimester testis (12–20 weeks gestation), DMRT1 repression (miR536/miR641) resulted in disruption of seminiferous cords with absence of DMRT1 protein expression in Sertoli (SOX9⁺) cells. No differences in proliferation (Ki67⁺) were observed and apoptotic cells (CC3⁺) were rare. Expression of the Sertoli cell associated gene, SOX8, was significantly reduced (miR536, 34% reduction, P = 0.031; miR641 36% reduction, P = 0.026), whilst SOX9 expression was unaffected. Changes in expression of AMH (miR536, 100% increase, P = 0.033), CYP26B1 (miR641, 38% reduction, P = 0.05) and PTGDS (miR642, 30% reduction, P = 0.0076) were also observed. Amongst granulosa cell associated genes, there was a significant downregulation in R-spondin 1 expression (miR536, 76% reduction, P < 0.0001; miR641, 49% reduction, P = 0.046); however, there were no changes in expression of the granulosa cell marker, FOXL2. Analysis of germ cell associated genes demonstrated a significant increase in the expression of the pluripotency gene OCT4 (miR536, 233%, P < 0.001). We used the xenograft system to investigate the longer-term effects of seminiferous cord disruption via DMRT1 repression. As was evident in vitro for second-trimester samples, DMRT1 repression resulted in focal testicular dysgenesis similar to that described in adults with TDS. These dysgenetic areas were devoid of germ cells, whilst expression of FOXL2 within the dysgenetic areas, indicated trans-differentiation from a male (Sertoli cell) to female (granulosa cell) phenotype.

LIMITATIONS, REASONS FOR CAUTION

Human fetal testis tissue is a limited resource; however, we were able to demonstrate significant effects of DMRT1 repression on the expression of germ and somatic cell genes, in addition to the induction of focal testicular dysgenesis, using these limited samples. In vitro culture may not reflect all aspects of human fetal testis development and function; however, the concurrent use of the xenograft model which represents a more physiological system supports the validity of the in vitro findings.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings have important implications for understanding the role of DMRT1 in human testis development and in the origin of testicular dysgenesis. In addition, we provide validation of a novel system that can be used to determine the effects of repression of genes that have been implicated in gonadal development and associated human reproductive disorders.

STUDY FUNDING/COMPETING INTEREST(S)

This project was funded by a Wellcome Trust Intermediate Clinical Fellowship (Grant No. 098522) awarded to RTM. LBS was supported by MRC Programme Grant MR/N002970/1. RAA was supported by MRC Programme Grant G1100357/1. RMS was supported by MRC Programme Grant G33253. This work was undertaken in the MRC Centre for Reproductive Health which is funded by the MRC Centre grant MR/N022556/1. The funding bodies had no input into the conduct of the research or the production of this manuscript. The authors have declared no conflicts of interest.

The bromodomain inhibitor JQ1 triggers growth arrest and apoptosis in testicular germ cell tumours in vitro and in vivo

Type II testicular germ cell cancers (TGCT) are the most frequently diagnosed tumours in young men (20–40 years) and are classified as seminoma or non‐seminoma. TGCTs are commonly treated by orchiectomy and chemo‐ or radiotherapy. However, a subset of metastatic non‐seminomas (embryonal carcinomas) displays only incomplete remission or relapse and requires novel treatment options. Recent studies have shown effective application of the small‐molecule inhibitor JQ1 in tumour therapy, which interferes with the function of ‘bromodomain and extraterminal (BET)’ proteins. JQ1‐treated TGCT cell lines display up‐regulation of genes indicative for DNA damage and cellular stress response and induce cell cycle arrest. Embryonal carcinoma (EC) cell lines, which presented as JQ1 sensitive, display down‐regulation of pluripotency factors and induction of mesodermal differentiation. In contrast, seminoma‐like TCam‐2 cells tolerated higher JQ1 concentrations and were resistant to differentiation. ECs xenografted in vivo showed a reduction in tumour size, proliferation rate and angiogenesis in response to JQ1. Finally, the combination of JQ1 and the histone deacetylase inhibitor romidepsin allowed for lower doses and less frequent application, compared with monotherapy. Thus, we propose that JQ1 in combination with romidepsin may serve as a novel therapeutic option for (mixed) TGCTs.

Clinical observations on chemotherapy curable malignancies: unique genetic events, frozen development and enduring apoptotic potential

BACKGROUND

A select number of relatively rare metastatic malignancies comprising trophoblast tumours, the rare childhood cancers, germ cells tumours, leukemias and lymphomas have been routinely curable with chemotherapy for more than 30 years. However for the more common metastatic malignancies chemotherapy treatment frequently brings clinical benefits but cure is not expected. Clinically this clear divide in outcome between the tumour types can appear at odds with the classical theories of chemotherapy sensitivity and resistance that include rates of proliferation, genetic development of drug resistance and drug efflux pumps. We have looked at the clinical characteristics of the chemotherapy curable malignancies to see if they have any common factors that could explain this extreme differential sensitivity to chemotherapy.

DISCUSSION

It has previously been noted how the onset of malignancy can leave malignant cells fixed with some key cellular functions remaining frozen at the point in development at which malignant transformation occurred. In the chemotherapy curable malignancies the onset of malignancy is in each case closely linked to one of the unique genetic events of; nuclear fusion for molar pregnancies, choriocarcinoma and placental site trophoblast tumours, gastrulation for the childhood cancers, meiosis for testicular cancer and ovarian germ cell tumours and VDJ rearrangement and somatic hypermutation for acute leukemia and lymphoma. These processes are all linked to natural periods of supra-physiological apoptotic potential and it appears that the malignant cells arising from them usually retain this heightened sensitivity to DNA damage. To investigate this hypothesis we have examined the natural history of the healthy cells during these processes and the chemotherapy sensitivity of malignancies arising before, during and after the events. To add to the debate on chemotherapy resistance and sensitivity, we would argue that malignancies can be functionally divided into 2 groups. Firstly those that arise in cells with naturally heightened apoptotic potential as a result of their proximity to the unique genetic events, where the malignancies are generally chemotherapy curable and then the more common malignancies that arise in cells of standard apoptotic potential that are not curable with classical cytotoxic drugs.

Male infertility: assessment of juvenile testicular dysfunction and risk for malignancy in cryptorchid boys based on resin section evaluation

Infertility is sometimes more a man's problem than a woman's, failure of one or both of the testes to descend (cryptorchidism) being the most frequent genital malformation in boys. Untreated, the undescended testis impairs germ cell development and significantly reduces adult fertility. A-dark spermatogonia are the stem cells for all future spermatozoa, and their depletion can be reliably estimated in resin semithin sections. Additionally, there is an increased risk of testicular preneoplasia in the form of carcinoma in situ (CIS) cells. The authors report how the pathologic biopsy examination of juvenile cryptorchid testes can assess infertility and malignancy risk.