Localisation of susceptibility genes for familial testicular germ cell tumour

Runs of homozygosity and testicular cancer risk

BACKGROUND

Testicular germ cell tumour (TGCT) is highly heritable but > 50% of the genetic risk remains unexplained. Epidemiological observation of greater relative risk to brothers of men with TGCT compared to sons has long alluded to recessively acting TGCT genetic susceptibility factors, but to date none have been reported. Runs of homozygosity (RoH) are a signature indicating underlying recessively acting alleles and have been associated with increased risk of other cancer types.

OBJECTIVE

To examine whether RoH are associated with TGCT risk.

METHODS

We performed a genome-wide RoH analysis using GWAS data from 3206 TGCT cases and 7422 controls uniformly genotyped using the OncoArray platform.

RESULTS

Global measures of homozygosity were not significantly different between cases and controls, and the frequency of individual consensus RoH was not significantly different between cases and controls, after correction for multiple testing. RoH at three regions, 11p13-11p14.3, 5q14.1-5q22.3 and 13q14.11-13q.14.13, were, however, nominally statistically significant at p < 0.01. Intriguingly, RoH200 at 11p13-11p14.3 encompasses Wilms tumour 1 (WT1), a recognized cancer susceptibility gene with roles in sex determination and developmental transcriptional regulation, processes repeatedly implicated in TGCT aetiology.

DISCUSSION AND CONCLUSION

Overall, our data do not support a major role in the risk of TGCT for recessively acting alleles acting through homozygosity, as measured by RoH in outbred populations of cases and controls.

Familial testicular germ cell tumor: no associated syndromic pattern identified

Background

Testicular germ cell tumor (TGCT) is the most common malignancy in young men. Familial clustering, epidemiologic evidence of increased risk with family or personal history, and the association of TGCT with genitourinary (GU) tract anomalies have suggested an underlying genetic predisposition. Linkage data have not identified a rare, highly-penetrant, single gene in familial TGCT (FTGCT) cases. Based on its association with congenital GU tract anomalies and suggestions that there is an intrauterine origin to TGCT, we hypothesized the existence of unrecognized dysmorphic features in FTGCT.

Methods

We evaluated 38 FTGCT individuals and 41 first-degree relatives from 22 multiple-case families with detailed dysmorphology examinations, physician-based medical history and physical examination, laboratory testing, and genitourinary imaging studies.

Results

The prevalence of major abnormalities and minor variants did not significantly differ between either FTGCT individuals or their first-degree relatives when compared with normal population controls, except for tall stature, macrocephaly, flat midface, and retro-/micrognathia. However, these four traits were not manifest as a constellation of features in any one individual or family. We did detect an excess prevalence of the genitourinary anomalies cryptorchidism and congenital inguinal hernia in our population, as previously described in sporadic TGCT, but no congenital renal, retroperitoneal or mediastinal anomalies were detected.

Conclusions

Overall, our study did not identify a constellation of dysmorphic features in FTGCT individuals, which is consistent with results of genetic studies suggesting that multiple low-penetrance genes are likely responsible for FTGCT susceptibility.

The rise of testicular germ cell tumours: the search for causes, risk factors and novel therapeutic targets

Since the beginning of the 20th century there has been a decline in the reproductive vitality of men within the Western world. The declining sperm quantity and quality has been associated with increased overt disorders of sexual development including hypospadias, undescended testes and type II testicular germ cell tumours (TGCTs). The increase in TGCTs cannot be accounted for by genetic changes in the population. Therefore exposure to environmental toxicants appears to be a major contributor to the aetiology of TGCTs and men with a genetic predisposition are particularly vulnerable. In particular, Type II TGCTs have been identified to arise from a precursor lesion Carcinoma in situ (CIS), identified as a dysfunctional gonocyte; however, the exact triggers for CIS development are currently unknown. Therefore the transition from gonocytes into spermatogonia is key to those studying TGCTs. Recently we have identified seven miRNA molecules (including members of the miR-290 family and miR-136, 463* and 743a) to be significantly changed over this transition period. These miRNA molecules are predicted to have targets within the CXCR4, PTEN, DHH, RAC and PDGF pathways, all of which have important roles in germ cell migration, proliferation and homing to the spermatogonial stem cell niche. Given the plethora of potential targets affected by each miRNA molecule, subtle changes in miRNA expression could have significant consequences e.g. tumourigenesis. The role of non-traditional oncogenes and tumour suppressors such as miRNA in TGCT is highlighted by the fact that the majority of these tumours express wild type p53, a pivotal tumour suppressor usually inactivated in cancer. While treatment of TGCTs is highly successful, the impact of these treatments on fertility means that identification of exact triggers, earlier diagnosis and alternate treatments are essential. This review examines the genetic factors and possible triggers of type II TGCT to highlight target areas for potential new treatments.

Mutational analysis of proto-oncogene Dbl on Xq27 in testicular germ cell tumors reveals a rare SNP in a patient with bilateral undescended testis

OBJECTIVES

An abundance of X chromosomes in testicular germ cell tumors (TGCTs), and a candidate TGCTs susceptibility gene (TGCT1) on Xq27 highlight the potential involvement of X chromosomes in TGCT pathogenesis. However, the TGCT1 on Xq27 has so far not been identified. We hypothesized that a somatic mutation of dbl oncogene on Xq27 may play a role for the development of TGCTs.

METHODS

We have screened 41 TGCT tissues for dbl mutations using single-strand conformation polymorphism (SSCP) analysis. These tissues are composed of 25 seminomatous TGCTs tissues and 16 non-seminomatous TGCTs tissues, including two cases with a rhabdomyosarcoma component.

RESULTS

Somatic mutations were not detected in the 25 exons of dbl in these TGCTs. However, we found a rare single nucleotide polymorphism (SNP) (T to C nucleotide change) within intron 22 in one out of the 41 TGCTs cases (2%). Furthermore, the sample with the rare SNP was identified as the sole TGCTs case associated with bilateral undescended testis in our series.

CONCLUSIONS

Our results indicate that proto-oncogene dbl is not a major target for sporadic TGCTs. However, the rare SNP in dbl may affect the susceptibility to undescended testis. Determining the frequency of this SNP in patients with various types of undescended testis in different ethnic groups is a warranted study.

Dissecting the molecular pathways of (testicular) germ cell tumour pathogenesis; from initiation to treatment-resistance

Human type II germ cell tumours (GCTs) originate from an embryonic germ cell, either as a primordial germ cell or gonocyte. This start determines the biological as well as clinical characteristics of this type of cancer, amongst others their totipotency as well as their overall (exceptional) sensitivity to DNA damaging agents. The histology of the precursor lesion, either carcinoma in situ or gonadoblastoma, depends on the level of testicularization (i.e. testis formation) of the gonad. The impact of either intrinsic (genetic) - and environmental factors involved in the pathogenesis is demonstrated by disorders of sex development as well as testicular dysgenesis syndrome as risk factors, including cryptorchidism, hypospadias and disturbed fertility as parameters. This knowledge allows identification of individuals at risk for development of this type of cancer, being a population of interest for screening. Factors known to regulate pluripotency during embryogenesis are proven to be of diagnostic value for type II GCTs, including OCT3/4, even applicable for non-invasive screening. In addition, presence of stem cell factor, also known as KITLG, allows distinction between delayed matured germ cells and the earliest stages of malignant transformation. This is of special interest because of the identified association between development of type II GCTs of the testis and a limited number of single nucleotide polymorphisms, including some likely related to KITL. Transition from the precursor lesion to an invasive cancer is associated with gain of the short arm of chromosome 12, in which multiple genes might be involved, including KRAS2 and possibly NANOG (pseudogenes). While most precursor lesions will progress to an invasive cancer, only a limited number of cancers will develop treatment resistance. Putative explanatory mechanisms are identified, including presence of microsatellite instability, BRAF mutations, apoptosis suppression and p21 sub-cellular localization. It remains to be investigated how these different pathways integrate to each other and how informative they are at the patient-individual level. Further understanding will allow development of more targeted treatment, which will benefit quality of life of these young cancer patients.

What is new in cryptorchidism and hypospadias--a critical review on the testicular dysgenesis hypothesis

It has been hypothesized that poor semen quality, testis cancer, undescended testis, and hypospadias are symptoms of one underlying entity--the testicular dysgenesis syndrome--leading to increasing male fertility impairment. Though testicular cancer has increased in many Western countries during the past 40 years, hypospadias rates have not changed with certainty over the same period. Also, recent studies demonstrate that sperm output may have declined in certain areas of Europe but is probably not declining across the globe as indicated by American studies. However, at the same time, there is increasing recognition of male infertility related to obesity and smoking. There is no certain evidence that the rates of undescended testes have been increasing with time during the last 50 years. In more than 95% of the cases, hypospadias is not associated with cryptorchidism, suggesting major differences in pathogenesis. Placental abnormality may occasionally cause both cryptorchidism and hypospadias, as it is also the case in many other congenital malformations. The findings of early orchidopexy lowering the risk of both infertility and testicular cancer suggest that the abnormal location exposes the cryptorchid testis to infertility and malignant transformation, rather than there being a primary abnormality. Statistically, 5% of testicular cancers only are caused by cryptorchidism. These data point to the complexity of pathogenic and epidemiologic features of each component and the difficulties in ascribing them to a single unifying process, such as testicular dysgenesis syndrome, particularly when so little is known of the actual mechanisms of disease.

Familial testicular germ cell tumors in adults: 2010 summary of genetic risk factors and clinical phenotype

Familial aggregations of testicular germ cell tumor (FTGCT) have been well described, suggesting the existence of a hereditary TGCT subset. Approximately 1.4% of newly diagnosed TGCT patients report a positive family history of TGCT. Sons and siblings of TGCT patients have four- to sixfold and eight- to tenfold increases in TGCT risk respectively. Segregation analyses suggest an autosomal recessive mode of inheritance. Linkage analyses have identified several genomic regions of modest interest, although no high-penetrance cancer susceptibility gene has been mapped yet. These data suggest that the combined effects of multiple common alleles, each conferring modest risk, might underlie familial testicular cancer. Families display a mild phenotype: the most common number of affected families is 2. Age at diagnosis is 2-3 years younger for familial versus sporadic cases. The ratio of familial seminoma to nonseminoma is 1.0. FTGCT is more likely to be bilateral than sporadic TGCT. This syndrome is cancer site specific. Testicular microlithiasis is a newly recognized FTGCT component. Candidate gene-association studies have implicated the Y chromosome gr/gr deletion and PDE11A gene mutations as genetic modifiers of FTGCT risk. Two genomewide association studies of predominantly sporadic but also familial cases of TGCT have implicated the KIT-ligand, SPRY4, and BAK1 genes as TGCT risk modifiers. All five loci are involved in normal testicular development and/or male infertility. These genetic data provide a novel insight into the genetic basis of FTGCT, and an invaluable guide to future TGCT research.

Familial testicular germ cell tumours

This article defines familial testicular germ cell tumours (FTGCTs) as testicular germ cell tumours (TGCTs) diagnosed in at least two blood relatives, a situation which occurs in 1-2% of all cases of TGCT. Brothers and fathers of TGCT patients have an 8-10- and 4-6-fold increased risk of TGCT, respectively, and an even higher elevated risk of TGCT in twin brothers of men with TGCT has been observed, suggesting that genetic elements play an important role in these tumours. Nevertheless, previous linkage studies with multiple FTGCT families did not uncover any high-penetrance genes and it has been concluded that the combined effects of multiple common alleles, each conferring a modest risk, might underlie FTGCT. In agreement with this assumption, recent candidate gene-association analyses have identified the chromosome Y gr/gr deletion and mutations in the PDE11A gene as genetic modifiers of FTGCT risk. Moreover, two genome-wide association studies of predominantly sporadic but also familial cases of TGCT have identified three additional susceptibility loci, KITLG, SPRY4 and BAK1. Notably, all five loci are involved in the biology of primordial germ cells, representing the cell of origin of TGCT, suggesting that the tumours arise as a result of disturbed testicular development.

Epidemiology of testicular cancer

Testicular cancer is of interest and importance because its incidence has been increasing in most countries over the past four decades. Although it remains an uncommon malignancy overall accounting for 1-2% of all tumours in men, testicular cancer is the most common malignancy in young men. There is marked geographical variation in the incidence of testicular cancer, with the highest incidence among men in Nordic countries and lowest incidence among men in the Middle East and Asia. The association between some risk factors, including cryptorchidism, a previous history of testicular cancer and a family history of testicular cancer, and the incidence of testicular cancer has been widely reported. We reviewed published reports and present the evidence to support or refute the association between the well-established and the less well-established risk factors and the incidence of testicular cancer.

Younger age-at-diagnosis for familial malignant testicular germ cell tumor

One of the clinical hallmarks of hereditary cancer susceptibility disorders is a younger-than-usual age at diagnosis. Familial aggregation of testicular germ cell tumor (TGCT) has been reported, but data on whether familial TGCT cases are diagnosed at an earlier age are inconclusive. Here we compared the age at diagnosis of familial TGCT cases with that of population cases in several countries. Familial TGCT is defined as affected individuals from families with >or=2 cases of TGCT. Age at diagnosis of familial cases from the United States, Canada, United Kingdom, Australia and New Zealand, Norway, and Hungary was compared to cases identified in population-based cancer registries from the respective country, using the generalized estimation equation method. Age at diagnosis was statistically significantly younger for familial TGCT cases from North America (P = 0.024), the United Kingdom (P < 0.0001), and Australia and New Zealand (P = 0.0033) compared with population cases. When stratified by histology, the difference in age at diagnosis distribution between familial and population cases was observed for seminoma cases from North America (P = 0.002) and the United Kingdom (P < 0.0001) and non-seminoma cases from the United Kingdom (P = 0.029) and Australia and New Zealand (P = 0.0023). In summary, we found that the age at diagnosis for familial TGCT cases is, on the average, 2-3 years younger than that for the population cases in North America, United Kingdom, and Australia and New Zealand. The younger age at diagnosis might be suggestive of a genetic basis for familial TGCT.

[Molecular pathology of testicular germ cell tumors: an update]

Germ cell tumors (GCT) comprise a heterogeneous group of benign and malignant tumors. Based on their different biological characteristics and their origin, five types of GCT are classified. Among these, malignant seminomatous and non-seminomatous GCT in males and females are designated as type II GCT. They occur most frequently as malignant testicular GCTs. Many characteristics of type II GCT can be linked to embryonic stem cells. Intratubular germ cell neoplasia, unclassified (IGCNU) is the precursor of type II GCT and derives from undifferentiated germ cells, gonocytes, which persist in the newborn testis and escape the normal differentiation process. It is suggested that Exon-17-activated mutations of the receptor tyrosine kinase, c-KIT, occur early in germ cell development and that gonocytes with an activated c-KIT receptor are restricted in their differentiation, thereby escaping normal development. New diagnostic markers for neoplastic germ cells, including OCT3/4 and AP-2gamma, are specifically detected in IGCNU, seminomas and embryonal carcinomas and are helpful in the differentiation of type II GCT from other malignant tumors.

The International Testicular Cancer Linkage Consortium: a clinicopathologic descriptive analysis of 461 familial malignant testicular germ cell tumor kindred

OBJECTIVES

Familial aggregation of testicular germ cell tumor (TGCT) has been reported, but it is unclear if familial TGCT represents a unique entity with distinct clinicopathologic characteristics. Here we describe a collection of familial TGCT cases from an international consortium, in an effort to elucidate any clinical characteristics that are specific to this population.

MATERIALS AND METHODS

Families with >or=2 cases of TGCT enrolled at 18 of the sites participating in the International Testicular Cancer Linkage Consortium were included. We analyzed clinicopathologic characteristics of 985 cases from 461 families.

RESULTS

A majority (88.5%) of families had only 2 cases of TGCT. Men with seminoma (50% of cases) had an older mean age at diagnosis than nonseminoma cases (P = 0.001). Among individuals with a history of cryptorchidism, TGCT was more likely to occur in the ipsilateral testis (kappa = 0.65). Cousin pairs appeared to represent a unique group, with younger age at diagnosis and a higher prevalence of cryptorchidism than other families.

CONCLUSIONS

Clinicopathologic characteristics in these familial TGCT cases were similar to those generally described for nonfamilial cases. However, we observed a unique presentation of familial TGCT among cousin pairs. Additional studies are needed to further explore this observation.

Testicular cancer and genetics knowledge among familial testicular cancer family members

PURPOSE

It was our aim to determine baseline levels of testicular cancer and genetics knowledge among members of families with Familial Testicular Cancer (FTC).

METHODS

This is a sub-study of an ongoing National Cancer Institute (NCI) multidisciplinary, etiologically-focused, cross-sectional study of FTC. We evaluated 258 male and female participants including testicular cancer (TC) survivors, blood relatives and spouses to assess factors associated with a Genetic Knowledge Scale (GKS) and Testicular Cancer Knowledge Scale (TCKS).

RESULTS

Knowledge levels were generally low, with genetic knowledge lower than TC knowledge (p < 0.01). Men with a personal TC history scored highest on TC knowledge, while gender, age and education differentially influenced knowledge levels, particularly among unaffected relatives.

CONCLUSIONS

Prior to identifying FTC susceptibility genes, we recommend tailoring FTC genetic education to the different informational needs of TC survivors, their spouses and relatives, in preparation for the day when clinical susceptibility testing may be available.

Genes, chromosomes and the development of testicular germ cell tumors of adolescents and adults

Testicular germ cell tumors (TGCTs) of adults and adolescents are thought to be derived from primordial germ cells or gonocytes. TGCTs develop postpuberty from precursor lesions known as intratubular germ cell neoplasia undifferentiated. The tumors can be divided into two groups based on their histology and clinical behavior; seminomas resemble primordial germ cells or gonocytes and nonseminomas resemble embryonic or extraembryonic tissues at various stages of differentiation. The most undifferentiated form of nonseminoma, embryonal carcinoma, resembles embryonic stem cells in terms of morphology and expression profiling, both mRNAs and microRNAs. Evidence supports both environmental factors and genetic predisposition underlying the development of TGCTs. Various models of development have been proposed and are discussed. In TGCTs, gain of material from the short arm of chromosome 12 is invariable: genes from this region include the proto-oncogene KRAS, which has activating mutations in approximately 10% of tumors or is frequently overexpressed. A number of different approaches to increase the understanding of the development and progression of TGCTs have highlighted the involvement of KIT, RAS/RAF/MAPK, STAT, and PI3K/AKT signaling. We review the role of these signaling pathways in this process and the potential influence of environmental factors in the development of TGCTs.

Testicular microlithiasis in siblings: clinical implications

Testicular microlithiasis is a relatively uncommon condition in children. It is characterized by the presence of microcalcifications within the testicular parenchyma. Although it is a benign finding, underlying diseases and other conditions must be ruled out because testicular microlithiasis has been found in association with both benign and malignant lesions in the testes and other tissues. We present two brothers with testicular microlithiasis, and highlight the prevalence, natural history, associated malignant conditions and follow-up recommendations of children diagnosed with testicular microlithiasis.

Clinical and genetic aspects of testicular germ cell tumours

In this paper we review clinical and genetic aspects of testicular germ cell tumours (TGCTs). TGCT is the most common type of malignant disorder in men aged 1540 years. Its incidence has increased sharply in recent years. Fortunately, survival of patients with TGCT has improved enormously, which can chiefly be attributed to the cisplatin-based polychemotherapy that was introduced in the nineteen eighties to treat patients with metastasized TGCT. In addition, new strategies have been developed in the surgical approach to metastasized/non-metastasized TGCT and alterations have been made to the radiotherapy technique and radiation dose for seminoma. Family history of TGCT is among the strongest risk factors for this tumour type. Although this fact and others suggest the existence of genetic predisposition to develop TGCT, no germline mutations conferring high risk of developing TGCT have been identified so far. A small deletion, referred to as gr/gr, identified on the Y chromosome is probably associated with only a modest increase in TGCT risk, and linkage of familial TGCT to the Xq27 region has not been confirmed yet. Whether highly penetrant TGCT-predisposing mutations truly exist or familial clustering of TGCT can be explained by combinations of weak predispositions, shared in utero or postnatal risks factors and coincidental somatic mutations is an intriguing puzzle, still waiting to be solved.

Susceptibility alleles for testicular germ cell tumour: a review

Family history is among the strongest and most consistent of the risk factors for testicular germ cell tumour (TGCT). Brothers of affected cases have an 8- to10-fold relative risk and fathers/sons have a risk between four and sixfold. The familial relative risk of TGCT is higher than for most other cancer types, which rarely exceeds four. The high relative risk suggests that inherited susceptibility to TGCT may account for a substantial fraction of TGCT cases. The search for TGCT susceptibility genes has proven difficult and a recent genome-wide linkage study for TGCT susceptibility loci demonstrated no statistically significant regions of linkage with all LOD scores less than two. Moreover, a previous report of linkage to a region on Xq27 was not replicated. The results from genetic linkage analysis demonstrate that TGCT susceptibility is likely to be due to several genes, each with a modest effect on disease risk. The Y chromosome, which cannot be analysed by genetic linkage, carries a number of testis- and germ cell-specific genes. We recently demonstrated that a deletion on the Y chromosome known as 'gr/gr' is a rare, low-penetrance allele that is associated with susceptibility to TGCT. Based on the evidence from the linkage search the 'gr/gr' deletion represents one of possibly many TGCT susceptibility alleles, and new and emerging technologies will be employed in future work to identify these genes.

Environmental, occupational and familial risks for testicular cancer: a hospital-based case-control study

Testicular cancer (TC) risk factors remain largely unknown, except for personal history of cryptorchidism and familial history of TC. We conducted a hospital-based case-control study on familial, environmental and occupational conditions in which we compared 229 cases and 800 controls. TC was correlated with cryptorchidism (OR = 3.02; CI: 1.90-4.79), a history of cryptorchidism in relatives (OR = 2.85; CI: 1.70-4.79), and TC (OR = 9.58; CI: 4.01-22.88], prostate cancer (OR = 1.80; CI: 1.08-3.02) and breast cancer (OR = 1.77; CI: 1.20-2.60) in relatives. Living in a rural area or having regular gardening activity (growing fruit or vegetables) was associated with an increased risk of TC (OR = 1.63; CI: 1.16-2.29; OR = 1.84; CI: 1.23-2.75). Regarding occupation, we found a relationship with employment in metal trimming (OR = 1.96; CI: 1.00-3.86), chemical manufacture (OR = 1.88; CI: 1.14-3.10), industrial production of glue (OR = 2.21; CI: 1.15-4.25), and welding (OR = 2.84; CI: 1.51-5.35). In a multivariate model, only a history of cryptorchidism in the men, cryptorchidism in relatives, TC, and breast cancer remained significant. Our findings contribute further evidence to a pattern of TC risk factors, which include the significant weight of personal reproductive history and also of testicular and breast cancer in relatives. By including in a multivariate model variables linked to environmental and occupational exposure and related to familial cancer history, neither living in a rural area nor any occupational exposure appeared to be a potential environmental TC risk factor.

Expression of SpanX mRNA in testicular germ cell tumors

The function of SpanX proteins is unknown, evidence is accumulating to suggest their involvement in tumorigenesis. A locus in Xq27, where the SpanX gene family is located, has been associated with testicular germ cell tumor (TGCT) onset. Therefore, we evaluated the presence of SpanX mRNA in six TGCT cases by RT-PCR. The results showed that SpanX mRNA is present in TGCT, confirming transcriptional activity of these genes in such tumors.

Familial testicular cancer: interest in genetic testing among high-risk family members

PURPOSE

This study is part of an ongoing National Cancer Institute multidisciplinary, etiologically-focused, cross-sectional study of Familial Testicular Cancer (FTC). The current report targets interest in clinical genetic testing for susceptibility to FTC.

METHODS

Demographics, knowledge, health beliefs, and psychological and social factors were evaluated as covariates related to interest in genetic testing.

RESULTS

The majority (66%) of 229 participants (64 affected men, 66 unaffected men, and 99 women) from 47 multiple-case FTC families expressed interest in having a genetic test within 6 months, should such a test become available. Interest was similar among the three subgroups mentioned above. Worries about insurance discrimination based on genetic test results were associated with a significantly lower interest in testing. Alternatively, participants were more likely to be interested in genetic testing if they were younger and had higher levels of family support, a physician's recommendation supporting testing, cancer distress, and a need for information to inform the health care of their children.

CONCLUSIONS

This study reveals social and relationship factors that FTC survivors and their relatives considered important when contemplating the use of new genetic technologies. This is the first study describing hypothetical interest in genetic testing for familial testicular cancer.

Hominoid-specific SPANXA/D genes demonstrate differential expression in individuals and protein localization to a distinct nuclear envelope domain during spermatid morphogenesis

Human sperm protein associated with the nucleus on the X chromosome consists of a five-member gene family (SPANXA1, SPANXA2, SPANXB, SPANXC and SPANXD) clustered at Xq27.1. Evolved from an ancestral SPANX-N gene family (at Xq27 and Xp11) present in all primates as well as in rats and mice, the SPANXA/D family is present only in humans, bonobos, chimpanzees and gorillas. Among hominoid-specific genes, the SPANXA/D gene family is considered to be undergoing rapid positive selection in its coding region. In this study, RT-PCR of human testis mRNA from individuals showed that, although all SPANXA/D genes are expressed in humans, differences are evident. In particular, SPANXC is expressed only in a subset of men. The SPANXa/d protein localized to the nuclear envelope of round, condensing and elongating spermatids, specifically to regions that do not underlie the developing acrosome. During spermiogenesis, the SPANXa/d-positive domain migrated into the base of the head as the redundant nuclear envelope that protrudes into the residual cytoplasm. Post-testicular modification of the SPANXa/d proteins was noted, as were PEST (proline, glutamic acid, serine, and threonine rich regions) domains. It is concluded that the duplication of the SPANX-N gene family that occurred 6-11 MYA resulted in a new gene family, SPANXA/D, that plays a role during spermiogenesis. The SPANXa/d gene products are among the few examples of X-linked nuclear proteins expressed following meiosis. Their localization to non-acrosomal domains of the nuclear envelope adjacent to regions of euchromatin and their redistribution to the redundant nuclear envelope during spermiogenesis provide a biomarker for the redundant nuclear envelope of spermatids and spermatozoa.

Xenobiotics with estrogen or antiandrogen action — disruptors of the male reproductive system

The environmental and life-style changes associated with developing industry and agriculture, especially the exposure to endocrine disrupting chemicals (xenobiotics), are considered as causes of the increasing incidence of male reproductive system disorders. Most of the xenobiotics, which harmfully influence the male reproductive system, reveal estrogen-like (xenoestrogens) or anti-androgenic activity. Recent data have revealed physiological roles of estrogens in the male, however, there are evidences that estrogen-like substances may lead to many undesirable symptoms in the male i.e. gonadal dysgenesis, genital malformations, cryptorchidism, decreased fertility potential and testicular neoplastic changes. The number of xenoestrogens is still growing in the environment, whereas the mechanisms of their action are still not exactly known. They can be harmful not only to the present but potentially also to the next generations.

Testicular Germ Cell Tumors: A Paradigm for the Successful Treatment of Solid Tumor Stem Cells

Treatment of testicular germ cell tumors (TGCTs) has been a success primarily due to the exquisite responsiveness of this solid tumor to cisplatin-based therapy. Despite the promise of cure for the majority of TGCT patients, the effectiveness of therapy for some patients is limited by toxicity and the problem of resistance. There is compelling rationale to further understand the biology of TGCTs in order to better treat other solid tumors and to address the shortcomings of present TGCT therapies. TGCTs contain undifferentiated pluripotent stem cells, known as embryonal carcinoma, that share many properties with human embryonic stem cells. The importance of cancer stem cells in the initiation, progression and treatment of solid tumors is beginning to emerge. We discuss TGCTs in the context of solid tumor curability and targeted cancer stem cell therapy.

Dysfunction of the mitotic:meiotic switch as a potential cause of neoplastic conversion of primordial germ cells

Germ cell tumours (GCT) are thought to arise as the result of a defect in early development, probably shortly after arrival of the migrating primordial germ cells (PGC) in the genital ridge when, if in a male genital ridge, the germ cells arrest in mitosis, but in a female genital ridge they enter meiosis. We suggest that dysfunction of the mitotic:meiotic switch, with cells aberrantly co-expressing functions pertinent to both states, might provide the genetic instability that could initiate tumour development. If this hypothesis is correct, GCT could arise because of disruption in the function of any one of a number of different genes involved in controlling mitosis and meiosis, rather than being dependent upon a single prominent susceptibility gene. The Notch signalling system is one candidate system for controlling the switch and we have identified expression of Notch2 and Notch4 in seminomas and carcinoma in situ. Thus those two members of the Notch family are candidates for proto-oncogenes that could play a role in GCT development. We have also identified a human homologue of the synaptonemal complex protein, SCP3, and have found its apparently aberrant expression in some established EC cell lines. One possibility is that abnormal regulation of such proteins involved in the synaptonemal complex could also lead to genetic instability in PGC and so also initiate tumour development.

Expression of SpanX proteins in normal testes and in testicular germ cell tumours

We investigated the expression of the SpanX protein family in cells of normal testes and in testicular germ cell tumours, mainly seminomas and embryonal carcinomas, using an immunohistochemical approach. Most of the normal germ cells, belonging to spermatogonial and primary spermatocytic classes, showed a strong nuclear positivity. In contrast, post-meiotic germ cells showed diffused cytoplasmic and sometimes also perinuclear localization of the signal. The vast majority of cells were also positive in eight seminomas, six embryonal cell carcinomas and one teratocarcinoma. In all seminomas, nuclei were either exclusively or preferentially labelled; whereas, the nuclear signal intensity decreased in parallel with the appearance of some cytoplasmic staining in embryonal carcinomas. In conclusion, these data suggest that the SpanX protein family is not exclusively expressed post-meiotically and that seminomas and embryonal carcinomas may originate from SpanX-positive carcinoma-in-situ cell.

Testicular germ-cell cancer

Testicular germ-cell tumours (TGCTs) represent the model of a curable malignancy; sensitive tumour markers, accurate prognostic classification, logical series of management trials, and high cure rates in both seminomas and non-seminomas have enabled a framework of effective cancer therapy. Understanding the molecular biology of TGCT could help improve treatment of other cancers. The typical presentation in young adults means that issues of long-term toxicity become especially important in judging appropriate management. A focus of recent developments has been to tailor aggressiveness of treatment to the severity of the prognosis. Recent changes affect the most common subtypes and include the reduction of chemotherapy for patients who have metastastic non-seminomas and a good prognosis, and alternatives to adjuvant radiotherapy in stage I seminomas. We summarise advances in the understanding and management of TGCT during the past decade.

Genome-wide linkage screen for testicular germ cell tumour susceptibility loci

A family history of disease is a strong risk factor for testicular germ cell tumour (TGCT). In order to identify the location of putative TGCT susceptibility gene(s) we conducted a linkage search in 237 pedigrees with two or more cases of TGCT. One hundred and seventy-nine pedigrees were evaluated genome-wide with an average inter-marker distance of 10 cM. An additional 58 pedigrees were used to more intensively investigate several genomic regions of interest. Genetic linkage analysis was performed with the ALLEGRO software using two model-based parametric analyses and a non-parametric analysis. Six genomic regions on chromosomes 2p23, 3p12, 3q26, 12p13-q21, 18q21-q23 and Xq27 showed heterogeneity LOD (HLOD) scores of greater than 1, with a maximum HLOD of 1.94 at 3q26. Genome-wide simulation studies indicate that the observed number of HLOD peaks greater than one does not differ significantly from that expected by chance. A TGCT locus at Xq27 has been previously reported. Of the 237 pedigrees examined in this study, 66 were previously unstudied at Xq27, no evidence for linkage to this region was observed in this new pedigree set. Overall, the results indicate that no single major locus can account for the majority of the familial aggregation of TGCT, and suggests that multiple susceptibility loci with weak effects contribute to the disease.

A discussion of the biology of testicular cancer and current concepts in the management of stage I and bilateral disease

This case was the subject of a Grand Round Presentation at the Royal Marsden Hospital, Sutton, UK on 8 June 2004. A case of metachronous, bilateral testicular germ-cell tumours (TGCTs) arising in a patient with a family history of this disease was presented. The second primary was managed conservatively. The rationale and outcome of this approach was presented, along with a discussion of the management of early stage TGCTs and the genetics of familial and bilateral disease.

Fertility Among Brothers of Patients with Testicular Cancer

OBJECTIVE

Patients with testicular cancer have decreased fertility prior to the diagnosis of cancer, although it is not clear whether the subfertility is the result of an emerging tumor, or whether subfertility and testicular cancer share causes. To test if they share causes, we assessed fertility among brothers of patients with testicular cancer.

METHODS

We compared 5,613 siblings (2,878 brothers) of patients with germ-cell testicular cancer, diagnosed in Sweden from 1960 to 2002, with 6,151 population controls (3,202 men). Using the Swedish Multi-Generation Register, we obtained information on the number of children born (until December 2003) from cases (n = 9,480) and controls (n = 10,739). Fertility was measured using two indicators, (a) offspring twinning rates, as dizygotic twinning is reduced by male subfertility, and (b) number of children. We used unconditional logistic regression, and analyzed brothers and sisters separately. Analyses on the number of children were restricted to subjects (39%) born prior to 1954, for whom information on reproductive life until age 50 was available.

RESULTS

Brothers, but not sisters, of patients with testicular cancer were less likely to have unlike-sex twins than controls (for unlike-sex twins, the odds ratio for the father being a sibling of testicular cancer patient was 0.53; 95% confidence interval, 0.26-1.09). The likelihood of being a brother of a patient with testicular cancer decreased monotonically with increasing number of children (P = 0.05), whereas no association was observed for the sisters.

CONCLUSION

The decreased fertility found among brothers of patients with testicular cancer argues in favor of shared causes between cancer-associated subfertility and testicular cancer. Genetic links and shared environment could explain the association.

Retinoic acid represses a cassette of candidate pluripotency chromosome 12p genes during induced loss of human embryonal carcinoma tumorigenicity

Testicular germ cell tumors (TGCTs) are the most common carcinomas of young men aged 15-35. The molecular events involved in TGCT genesis are poorly understood. TGCTs have near universal amplification of the short arm of chromosome 12, however positional cloning efforts have not identified causative genes on 12p involved in formation or progression of TGCTs. Human embryonal carcinoma (EC) are the stem cells of TGCTs and are pluripotent. EC cells terminally differentiate toward a neuronal lineage with all-trans retinoic acid (RA) treatment resulting in a concomitant G1 cell cycle arrest and loss of tumorigenicity. Our efforts to define the molecular mechanisms of RA-mediated tumor cell differentiation at a critical "commitment to differentiate" window has identified a cassette of genes on 12p that are repressed with RA precisely as EC cells lose tumorigenic potential. These are Nanog, CD9, EDR1 (PHC1), SCNN1A, GDF3, Glut3 and Stella. The master pluripotency regulator Oct4 is located on chromosome 6 and is also repressed by RA. Notably, knockdown of Oct4 with siRNA results in repression of basal Nanog, EDR1, GDF3 and Stella gene expression. Nanog has recently been identified to play a role in maintenance of the pluripotency of mouse embryonic stem cells and CD9, EDR1, GDF3, and Stella have each been implicated as stem cell markers. Since RA suppresses the tumorigenicity of EC cells, these genes may have a critical role in the etiology of TGCTs, suggesting a link between enforced pluripotency and transformation.

Risk of Contralateral Testicular Cancer: A Population-based Study of 29 515 U.S. Men

BACKGROUND

Although risk estimates for synchronous and metachronous contralateral testicular cancers vary widely, many clinicians recommend routine biopsy of the contralateral testis for patients diagnosed with unilateral testicular cancer. We evaluated the risk of contralateral testicular cancer and survival in a large population-based cohort of men diagnosed with testicular cancer before age 55 years.

METHODS

For 29 515 testicular cancer cases reported to the National Cancer Institute's Surveillance, Epidemiology and End Results Program from 1973 through 2001, we estimated the prevalence of synchronous contralateral testicular cancer, the observed-to-expected ratio (O/E) and 15-year cumulative risk of metachronous contralateral testicular cancer, and the 10-year overall survival rate of both synchronous and metachronous contralateral testicular cancer, using the Kaplan-Meier method for the two latter assessments. Age-adjusted multivariable analyses were used to examine risk according to histologic type of the original cancer.

RESULTS

A total of 175 men presented with synchronous contralateral testicular cancer; 287 men developed metachronous contralateral testicular cancer (O/E = 12.4 [95% confidence interval {CI} = 11.0 to 13.9]; 15-year cumulative risk = 1.9% [95% CI = 1.7% to 2.1%]). In the multivariable analysis, only nonseminomatous histology of the first testicular cancer was associated with a statistically significantly decreased risk of metachronous contralateral testicular cancer (hazard ratio [HR] = 0.60, 95% confidence interval [CI] = 0.46 to 0.79; P<.001). Increasing age at first testicular cancer diagnosis was associated with decreasing risk of nonseminomatous metachronous contralateral testicular cancer (odds ratio = 0.90, 95% CI = 0.86 to 0.94). The 10-year overall survival rate after metachronous contralateral testicular cancer diagnosis was 93% (95% CI = 88% to 96%), and that after synchronous contralateral testicular cancer was 85% (95% CI = 78% to 90%).

CONCLUSIONS

The low cumulative risk of metachronous contralateral testicular cancer and favorable overall survival of patients diagnosed with metachronous contralateral testicular cancer is in accordance with the current U.S. approach of not performing a biopsy on the contralateral testis.

Fusion of the SUMO/Sentrin-specific protease 1 gene SENP1 and the embryonic polarity-related mesoderm development gene MESDC2 in a patient with an infantile teratoma and a constitutional t(12;15)(q13;q25)

Recently, we identified a patient with an infantile sacrococcygeal teratoma and a constitutional t(12;15)(q13;q25). Here, we show that, as a result of this chromosomal translocation, the SUMO/Sentrin-specific protease 1 gene (SENP1) on chromosome 12 and the embryonic polarity-related mesoderm development gene (MESDC2) on chromosome 15 are disrupted and fused. Both reciprocal SENP1-MESDC2 (SEME) and MESDC2-SENP1 (MESE) fusion genes are transcribed in tumor-derived cells and their open reading frames encode aberrant proteins. As a consequence of this, and in contrast to wild-type (WT) MESDC2, the translocation-associated SEME protein is no longer targeted to the endoplasmatic reticulum, leading to a presumed loss-of-function as a chaperone for the WNT co-receptors LRP5 and/or LRP6. Ultimately, this might lead to abnormal development and/or routing of germ cell tumor precursor cells. SUMO, a post-translational modifier, plays an important role in several cellular key processes and is cleaved from its substrates by WT SENP1. Using a PML desumoylation assay, we found that translocation-associated MESE proteins exhibit desumoylation capacities similar to those observed for WT SENP1. We speculate that spatio-temporal disturbances in desumoylating activities during critical stages of embryonic development might have predisposed the patient. Together, the constitutional t(12;15)(q13;q25) translocation revealed two novel candidate genes for neonatal/infantile GCT development: MESDC2 and SENP1.

Defining minimum genomic regions of imbalance involved in testicular germ cell tumors of adolescents and adults through genome wide microarray analysis of cDNA clones

Identifying changes in DNA copy number can pinpoint genes that may be involved in tumor development. Here we have defined the smallest overlapping regions of imbalance (SORI) in testicular germ cell tumors other than the 12p region, which has been previously investigated. Definition of the regions was achieved through comparative genomic hybridization (CGH) analysis of a 4559 cDNA clone microarray. A total of 14 SORI were identified, which involved at least five of the 11 samples analysed. Many of these refined regions were previously reported using chromosomal or allelic imbalance studies. The SORI included gain of material from the regions 4q12, 17q21.3, 22q11.23 and Xq22, and loss from 5q33, 11q12.1, 16q22.3 and 22q11. Comparison with parallel chromosomal CGH data supported involvement of most regions. The various SORI span between one and 20 genes and highlight potential oncogenes/tumor suppressor genes to be investigated further.

Testicular germ-cell tumours in a broader perspective

The germ-cell tumours are a fascinating group of neoplasms because of their unusual biology and the spectacular therapeutic results that have been obtained in these tumours. Traditionally, this group of neoplasms is presented in an organ-oriented approach. However, recent clinical and experimental data convincingly demonstrate that these neoplasms are one disease with separate entities that can manifest themselves in different anatomical sites. We propose five entities, in which the developmental potential is determined by the maturation stage and imprinting status of the originating germ cell. Recent progress begins to explain the apparent unpredictable development of germ-cell tumours and offers a basis for understanding their exquisite sensitivity to therapy.

Testicular, Other Genital, and Breast Cancers in First-Degree Relatives of Testicular Cancer Patients and Controls

Previous studies showed an increased prevalence of testicular cancer among fathers and brothers of testicular cancer patients. We examined whether testicular, other genital, and breast cancers aggregate in parents and siblings of testicular cancer patients in a population-based case-control study, including males, ages 15 to 69 years at diagnosis, with primary malignant tumors of the testes or extragonadal germ cell tumors. Controls were ascertained through the mandatory registries of residents and frequency matched to the cases by age and region of residence. In a face-to-face interview, 269 cases and 797 controls provided health-related information on parents and siblings. We calculated odds ratios (OR) and corresponding 95% confidence intervals (95% CI) based on the generalized estimating equations technique, adjusting for the matching variables and relatives' age. Three (1.1%) fathers and eight (3.2%) brothers of cases were affected with testicular cancer compared with four (0.5%) fathers and two (0.2%) brothers of controls. The OR (95% CI) of familial testicular cancer was 6.6 (2.35-18.77). Only nonseminoma patients had fathers with testicular cancer, whereas the affected brothers were all related to seminoma patients. Overall, we found an increased risk for genital other than testicular cancers (OR 2.5, 95% CI 1.43-4.43). For breast cancer, we detected an increased risk in sisters (OR 9.5, 95% CI 2.01-45.16, adjusted for age of study participant and age of sister) but not in mothers. Our findings support the hypothesis that testicular and other genital cancers have a common familial component that may be due to genetic and shared exogenous factors such as estrogen exposure during fetal development.

Chromosomes, genes, and development of testicular germ cell tumors

A literature review found 265 articles on testicular germ cell tumors (TGCTs) detailing the copy number of chromosomal regions and expression of 245 genes. An initial precursor stage, intratubular germ cell neoplasia (IGCN), is characterized by triploidization and an upregulation of KIT, ALPP, CCDN2, and ZNF354A, and a downregulation of CDKN2D. TGCT regularly have a series of chromosomal aberrations: a decrease in copy number at 4q21 approximately qter and 5q14 approximately qter; an increase at 7p21 approximately pter, 7q21 approximately q33, and 8q12 approximately q23 (especially high increase in seminoma); a decrease at 11p11 approximately p15 and 11q14 approximately q24; an increase at 12p11 approximately pter; a decrease at 13q14 approximately q31; an increase of 17q11 approximately q21 (only for nonseminoma); a decrease of 18q12 approximately qter; and an increase at 21q21 approximately qter, 22q11 approximately qter (only for seminoma), and Xq. Macroscopically overt TGCT is associated with a characteristic series of abnormalities in the retinoblastoma pathway including upregulation of cyclin D2 and p27 and downregulation of RB1 and the cyclin-dependent kinase inhibitors p16, p18, p19, and p21. TGCT thus has a synergistic pattern in gene expressions of the retinoblastoma pathway that is rare in other malignancies.

Genetic predisposition to testicular germ-cell tumours

Testicular germ-cell tumours (TGCT) are the most common neoplasm in young men. Various studies have suggested the existence of an inherited predisposition to development of these tumours. Genome-wide screens subsequently provided evidence of a TGCT susceptibility gene on chromosome Xq27 (TGCT1) that might also predispose to cryptorchism. However, this putative gene has yet to be identified, and other TGCT susceptibility genes probably exist. Completion of the human gene map and advances in genetic research will facilitate further investigation of genetic predisposition to TGCT. Insight into inheritance of TGCT might lead to the identification of individuals at increased risk of developing the disorder, increase our understanding of the mutation pathways that lead to sporadic cases, and contribute to improvement in diagnosis and treatment. Clinicians should record the family history of cancer and urogenital differentiation defects in patients with TGCT.

Bilateral germ-cell tumours: 22-year experience at the Institut Gustave Roussy

The aim of this study was to describe the incidence, clinical and histological characteristics, treatment and long-term follow-up of bilateral germ-cell tumours (BGCT) of the testis in order to determine in what respects they differ significantly from unilateral germ-cell tumours. In all, 31 patients with BGCT had metachronous tumours and 14 had synchronous tumours. Among the metachronous tumours, 61% occurred more than 5 years after the first tumour. The overall incidence of BGCT in patients with testicular germ-cell tumours (TGCT) was 1.9%. The incidence was 3.2% in patients presenting with a seminoma and 1.4 % in patients presenting with a nonseminomatous germ-cell tumour (NSGCT). Patients under 30 years of age at the time of the initial diagnosis had a higher incidence of bilateral tumours compared with older men. The outcome of BGCT was excellent. A high association was found between BGCT, sterility and suspected genetic risk factors for TGCT. These results argue against a systematic contralateral biopsy at diagnosis of first TGCT in all patients, but emphasise the importance of patient education and of the need to better identify patients at risk for a second TGCT. Therapeutic indications for synchronous BGCT, including conservative treatment, need to be better defined.

Increased predisposition to cancer in brothers and offspring of testicular tumor patients

Cancer susceptibility was examined in first-degree relatives of 293 testicular tumor patients (TTPs) and 586 age-matched healthy males. Significantly increased risk was found in the families of TTPs (OR: 1.4; CI: 1.08-1.79), however, except for testicular cancer of 7 brothers (OR: 11.7; CI: 1.42-256.5), and 6 various childhood tumors (bilateral Wilms' tumor, neuroblastoma, medulloblastoma, ALL, histiocytosis-X, testicular tumor) of 200 offspring (OR: 12.9; CI: 1.54-286.2), no association with other malignancies was observed. No differences were seen between the fertility of patients and controls when occupational or socio-economic status of the families was taken into account. However, the majority of the controls (85%) fathered the first child between 20-30 years of age, while only 61% of TTPs had the first child in the same age group. TTPs fathered more girls than boys (P=0.009), and the lower male - higher female ratio of index children was also identical, irrespective of the conception taking place before or after the father's treatment. Occupations did not, but smoking might have influenced cancer susceptibility of the patients. Aggregation of fraternal testicular tumors, and both dramatically increased cancer risk and altered sex ratio of the offspring indicate a remarkable role of hereditary factors in tumorigenesis and later consequences of a certain portion of testicular malignancies, which must be refined by molecular studies.

Cytogenetic and molecular analysis of a family with three brothers afflicted with germ-cell cancer

A thorough cytogenetic investigation and an analysis of detailed questionnaires were performed in a family with three brothers afflicted with germ-cell tumors (GCTs), in an attempt to detect a congenital factor related either to a hereditary genetic background or an environmental/lifestyle influence. One brother had an intracranial tumor in the pineal region and the two others had testicular tumors. Peripheral blood was studied by traditional karyotyping, multicolor-FISH, high-resolution comparative genomic hybridization (HR-CGH), and molecular analysis of selected loci on sex chromosomes (Yq11 region, TSPY, and the androgen receptor gene); however, no abnormalities were detected. The HR-CGH analysis of microdissected histological components of the overt tumors and the adjacent carcinoma in situ demonstrated a pattern of genomic imbalances characteristic for sporadic GCTs, including gain of 12p. The questionnaire and interview revealed a history of different cancers in the extended family, and a possible in utero and/or infantile exposure of the three brothers with GCTs to compounds suspected of endocrine-disrupting properties. Although no genetic aberration was detected in this family, we suspect the presence of a recessive hereditary factor pre-disposing to cancer, which probably was manifested as GCTs in the three brothers because of an adverse effect of an environmental factor on the early germ-cell differentiation.

Current views on the pathogenesis of testicular germ cell tumours and perspectives for future research: highlights of the 5th Copenhagen Workshop on Carcinoma in situ and Cancer of the Testis

This review article highlights the most important contributions presented at the 5th Copenhagen Workshop on Carcinoma in situ and Cancer of the Testis, which was held in Denmark, August 29-31, 2002. The major themes that emerged at the meeting are critically discussed and perspectives for future research in this field are presented.