Analysis of the DND1 gene in men with sporadic and familial testicular germ cell tumors.

A base substitution in the mouse Dnd1 gene resulting in a truncated Dnd protein has been shown to be responsible for germ cell loss and the development of testicular germ cell tumors (TGCT) in the 129 strain of mice. We investigated the human orthologue of this gene in 263 patients (165 with a family history of TGCT and 98 without) and found a rare heterozygous variant, p. Glu86Ala, in a single case. This variant was not present in control chromosomes (0/4,132). Analysis of the variant in an additional 842 index TGCT cases (269 with a family history of TGCT and 573 without) did not reveal any additional instances. The variant, p. Glu86Ala, is within a known functional domain of DND1 and is highly conserved through evolution. Although the variant may be a rare polymorphism, a change at such a highly conserved residue is characteristic of a disease-causing variant. Whether it is disease-causing or not, mutations in DND1 make, at most, a very small contribution to TGCT susceptibility in adults and adolescents.

Frequency and heritability of WT1 mutations in nonsyndromic Wilms' tumor patients: a UK Children's Cancer Study Group Study.

PURPOSE: Constitutional WT1 mutations in patients with Wilms' tumor (WT) have specifically been associated with genitourinary abnormalities, such as cryptorchidism and hypospadias. We sought to ascertain the frequency and heritability of constitutional WT1 mutations in nonsyndromic WT patients. PATIENTS AND METHODS: Constitutional DNA from 282 patients treated at seven United Kingdom Children's Cancer Study Group centers was screened for WT1 mutations using heteroduplex analysis. Bidirectional sequencing was used to confirm the mutation and to analyze the corresponding parental DNA samples. RESULTS: Five different constitutional WT1 mutations were identified in six children. Mutations in four patients were confirmed to be de novo, and all five mutations are predicted to produce truncated protein. The WT1 mutation group had a young median age at diagnosis of 13.8 months, compared with 34.9 months in the group in whom no WT1 mutations were found; four were female and two were male; and all tumors were of favorable histology. The three tumors with known histologic subtype were stromal-predominant. Contrary to expectation, four of six mutations occurred in children with unilateral tumors without any associated genitourinary abnormality. CONCLUSION: Constitutional WT1 mutations occur with a low frequency (2.1%; 95% CI, 0.8% to 4.6%) in nonsyndromic WT patients. Most mutations occurred in children with unilateral WT without associated genitourinary abnormalities, creating difficulties in identifying individuals with germline mutations on phenotype alone. Two factors that may indicate that an individual is carrying a germline WT1 mutation are an early age of onset and stromal-predominant histology of the WT.

Localisation of susceptibility genes for familial testicular germ cell tumour.

Approximately 1700 men in the United Kingdom develop testicular germ cell tumours (TGCT) per year. Among the known risk factors a family history of disease remains one of the strongest (1, 2). Two-percent of TGCT cases report another affected family member. Epidemiological studies have shown that there is an eight to ten fold increase in relative risk of TGCT to brothers of patients and a fourfold increased risk to fathers and sons (2-5). This relative risk is considerably higher than for most other common cancers, which rarely exceeds four and strongly suggests that genes may play an important role in TGCT. Linkage analysis of the set of families compatible with X-linkage (i.e. no male to male transmission) provided the first statistically significant evidence for a TGCT predisposition locus (6). The gene called TGCT1 is located at Xq27 and seems to be associated with a risk of bilateral disease and undescended testis. However TGCT1 does not account for all TGCT pedigrees and additional susceptibility genes must exist. Our group has now genotyped 179 TGCT pedigrees and identified additional genomic regions that might also harbour TGCT susceptibility genes. This paper reviews the current data for the region at Xq27 and presents evidence for several other possible candidate regions.

Predisposition alleles for Testicular Germ Cell Tumour.

For some time, it has been known that there is a substantial genetic component to testicular germ cell tumour susceptibility, supported by several pieces of evidence, including the significantly increased familial risk and differential risk among races. However, despite extensive linkage searches on available families, no high penetrance genes have been identified. Recently genome-wide association studies have revealed three candidate loci, which confer up to a four-fold risk of developing TGCT. The genome-wide association studies for this cancer are noteworthy, because of the high effect sizes demonstrated at each loci and the biological plausibility of the genes at or near the associated SNPs, particularly KITLG.

Variants near DMRT1, TERT and ATF7IP are associated with testicular germ cell cancer.

We conducted a genome-wide association study for testicular germ cell tumor, genotyping 298,782 SNPs in 979 affected individuals and 4,947 controls from the UK and replicating associations in a further 664 cases and 3,456 controls. We identified three new susceptibility loci, two of which include genes that are involved in telomere regulation. We identified two independent signals within the TERT-CLPTM1L locus on chromosome 5, which has previously been associated with multiple other cancers (rs4635969, OR=1.54, P=1.14x10(-23); rs2736100, OR=1.33, P=7.55x10(-15)). We also identified a locus on chromosome 12 (rs2900333, OR=1.27, P=6.16x10(-10)) that contains ATF7IP, a regulator of TERT expression. Finally, we identified a locus on chromosome 9 (rs755383, OR=1.37, P=1.12x10(-23)), containing the sex determination gene DMRT1, which has been linked to teratoma susceptibility in mice.

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.

A genome-wide association study of testicular germ cell tumor.

We conducted a genome-wide association study for testicular germ cell tumor (TGCT), genotyping 307,666 SNPs in 730 cases and 1,435 controls from the UK and replicating associations in a further 571 cases and 1,806 controls. We found strong evidence for susceptibility loci on chromosome 5 (per allele OR = 1.37 (95% CI = 1.19-1.58), P = 3 x 10(-13)), chromosome 6 (OR = 1.50 (95% CI = 1.28-1.75), P = 10(-13)) and chromosome 12 (OR = 2.55 (95% CI = 2.05-3.19), P = 10(-31)). KITLG, encoding the ligand for the receptor tyrosine kinase KIT, which has previously been implicated in the pathogenesis of TGCT and the biology of germ cells, may explain the association on chromosome 12.

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.

Somatic KIT mutations occur predominantly in seminoma germ cell tumors and are not predictive of bilateral disease: report of 220 tumors and review of literature.

Mutations in the KIT gene occur in approximately 8% of all testicular germ cell tumors (TGCT) and KIT is the most frequently mutated known cancer gene. One report has shown that 93% of patients with bilateral disease have a mutation at codon 816 of the KIT gene. Importantly, this suggests that the identification of a mutation in KIT is predictive of the development of a contralateral TGCT. We investigated the frequency and type of mutations in KIT in a series of 220 tumors from 211 patients with TGCTs and extragonadal germ cell tumors. In 170 patients with unilateral TGCT and no additional germ cell tumour, we identified one exon 11 mutation in a patient with unilateral TGCT and eight activating KIT mutations in exon 17 (9/175, 5.1%). In 32 patients with bilateral TGCT, one patient had an activating KIT mutation in exon 17 (3.1%). The incidence of activating KIT mutations in sporadic TGCT vs. familial TGCT was not significantly different. All mutations were identified in seminomas. Three extragonadal primary germ cell tumors were examined and in one tumor an activating KIT mutation was demonstrated in the pineal germinoma. Interestingly, this mutation was also seen in the patient's testicular seminoma. We find no evidence for an increased frequency of KIT mutations in bilateral TGCT.

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.

The Y deletion gr/gr and susceptibility to testicular germ cell tumor.

Testicular germ cell tumor (TGCT) is the most common cancer in young men. Despite a considerable familial component to TGCT risk, no genetic change that confers increased risk has been substantiated to date. The human Y chromosome carries a number of genes specifically involved in male germ cell development, and deletion of the AZFc region at Yq11 is the most common known genetic cause of infertility. Recently, a 1.6-Mb deletion of the Y chromosome that removes part of the AZFc region--known as the "gr/gr" deletion--has been associated with infertility. In epidemiological studies, male infertility has shown an association with TGCT that is out of proportion with what can be explained by tumor effects. Thus, we hypothesized that the gr/gr deletion may be associated with TGCT. Using logistic modeling, we analyzed this deletion in a large series of TGCT cases with and without a family history of TGCT. The gr/gr deletion was present in 3.0% (13/431) of TGCT cases with a family history, 2% (28/1,376) of TGCT cases without a family history, and 1.3% (33/2,599) of unaffected males. Presence of the gr/gr deletion was associated with a twofold increased risk of TGCT (adjusted odds ratio [aOR] 2.1; 95% confidence interval [CI] 1.3-3.6; P = .005) and a threefold increased risk of TGCT among patients with a positive family history (aOR 3.2; 95% CI 1.5-6.7; P = .0027). The gr/gr deletion was more strongly associated with seminoma (aOR 3.0; 95% CI 1.6-5.4; P = .0004) than with nonseminoma TGCT (aOR 1.5; 95% CI 0.72-3.0; P = .29). These data indicate that the Y microdeletion gr/gr is a rare, low-penetrance allele that confers susceptibility to TGCT.