Localization to Xq27 of a susceptibility gene for testicular germ-cell tumours.

Testicular germ-cell tumours (TGCT) affect 1 in 500 men and are the most common cancer in males aged 15-40 in Western European populations. The incidence of TGCT has risen dramatically over the last century. Known risk factors for TGCT include a history of undescended testis (UDT), testicular dysgenesis, infertility, previously diagnosed TGCT (ref. 7) and a family history of the disease. Brothers of men with TGCT have an 8-10-fold risk of developing TGCT (refs 8,9), whereas the relative risk to fathers and sons is fourfold (ref. 9). This familial relative risk is much higher than that for most other types of cancer. We have collected samples from 134 families with two or more cases of TGCT, 87 of which are affected sibpairs. A genome-wide linkage search yielded a heterogeneity lod (hlod) score of 2.01 on chromosome Xq27 using all families compatible with X inheritance. We obtained a hlod score of 4.7 from families with at least one bilateral case, corresponding to a genome-wide significance level of P=0.034. The proportion of families with UDT linked to this locus was 73% compared with 26% of families without UDT (P=0.03). Our results provide evidence for a TGCT susceptibility gene on chromosome Xq27 that may also predispose to UDT.

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.

Case of interstitial 12q deletion in association with Wilms tumor.

A 14-month-old boy presenting with Wilms tumor (WT) was found to have a small de novo deletion of the long arm of chromosome 12 (12q11-12q13.11). Microsatellite analysis of this region from constitutional DNA showed that the paternal allele was absent between the markers D12S331 and D12S1713 (inclusive). In the WT there was no evidence of loss of the maternal chromosome. Constitutional chromosome abnormalities can often point to the presence of genes that are important in disease, and the deletion of chromosome 12 in this patient may indicate a gene involved in WT. To determine whether a WT predisposition locus exists at 12q we examined the region in two familial Wilms tumor (FWT) pedigrees unlinked to the known FWT genes on chromosomes 17q (FWT1), 19q (FWT2), and 11p (WT1). In both families WT did not segregate with chromosome 12q markers located within the deletion boundaries.

Do all patients with bilateral testis cancer have a hereditary predisposition?

An international study has demonstrated that patients with bilateral testicular cancer are significantly more likely to have brothers with testis cancer than those with unilateral disease. This, together with other evidence, implies that patients with bilateral disease are likely to carry a predisposing genotype. But is it the great majority of them which is thus predisposed? We show that if as few as half of these patients have the predisposing genotype, its penetrance would have to be 80%, causing 38% of resulting cases to be bilateral. Evidence from the International Testis Cancer Linkage Consortium shows that the proportion of familial cases with bilateral disease is much lower. It is likely that at least the majority of cases of bilateral testis cancer arise as a result of a predisposing genotype.

A physical analysis of the Y chromosome shows no additional deletions, other than Gr/Gr, associated with testicular germ cell tumour.

Testicular germ cell tumour (TGCT) is the most common malignancy in men aged 15-45 years. A small deletion on the Y chromosome known as 'gr/gr' was shown to be associated with a two-fold increased risk of TGCT, increasing to three-fold in cases with a family history of TGCT. Additional deletions of the Y chromosome, known as AZFa, AZFb and AZFc, are described in patients with infertility; however, complete deletions of these regions have not been identified in TGCT patients. We screened the Y chromosome in a series of TGCT cases to evaluate if additional deletions of Y were implicated in TGCT susceptibility. Single copy Y chromosome STS markers with an average inter-marker spacing of 128 kb were examined in constitutional DNA of 271 index TGCT patients. Three markers showed evidence of deletions, sY1291, indicative of 'gr/gr' (eight out of 271; 2.9%), Y-DAZ3 contained within 'gr/gr' (21 out of 271; 7.7%) and a single deletion of the marker G66152 was identified in one TGCT case. No other markers demonstrated deletions. While several regions of the Y chromosome are known to be deleted and associated with infertility, our study provides no evidence to suggest regions of Y deletion, other than 'gr/gr', are associated with susceptibility to TGCT in UK patients.

Testicular microlithiasis as a familial risk factor for testicular germ cell tumour.

Testicular microlithiasis (TM) is characterised by small intratesticular calcifications, which can be visualised by ultrasound. Men with testicular germ cell tumour (TGCT) have a higher frequency of TM than men without TGCT. To clarify the association between TGCT and TM and to investigate the relationship between TGCT susceptibility and TM, we recruited TGCT patients with and without family history of TGCT, unaffected male relatives and healthy male controls from the UK. Testicular ultrasound data were analysed from 328 men. Testicular microlithiasis was more frequent in TGCT cases than controls (36.7 vs 17.8%, age adjusted P<0.0001) and in unaffected male relatives than controls (34.5 vs 17.8%, age adjusted P=0.02). Testicular germ cell tumour case and matched relative pairs showed greater concordance for TM than would be expected by chance (P=0.05). We show that TM is present at a higher frequency in relatives of TGCT cases than expected by chance indicating that TM is a familial risk factor for TGCT. Although the familiality of TM could be due to shared exposures, it is likely that there exists a genetic susceptibility to TM that also predisposes to TGCT. We suggest that TM is an alternative manifestation of a TGCT susceptibility allele.

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.

Evidence for susceptibility genes to familial Wilms tumour in addition to WT1, FWT1 and FWT2.

Three loci have been implicated in familial Wilms tumour: WT1 located on chromosome 11p13, FWT1 on 17q12-q21, and FWT2 on 19q13. Two out of 19 Wilms tumour families evaluated showed strong evidence against linkage at all three loci. Both of these families contained at least three cases of Wilms tumour indicating that they were highly likely to be due to genetic susceptibility and therefore that one or more additional familial Wilms tumour susceptibility genes remain to be found.

Somatic mutations of KIT in familial testicular germ cell tumours.

Somatic mutations of the KIT gene have been reported in mast cell diseases and gastrointestinal stromal tumours. Recently, they have also been found in mediastinal and testicular germ cell tumours (TGCTs), particularly in cases with bilateral disease. We screened the KIT coding sequence (except exon 1) for germline mutations in 240 pedigrees with two or more cases of TGCT. No germline mutations were found. Exons 10, 11 and 17 of KIT were examined for somatic mutations in 123 TGCT from 93 multiple-case testicular cancer families. Five somatic mutations were identified; four were missense amino-acid substitutions in exon 17 and one was a 12 bp in-frame deletion in exon 11. Two of seven TGCT from cases with bilateral disease carried KIT mutations compared with three out of 116 unilateral cases (P=0.026). The results indicate that somatic KIT mutations are implicated in the development of a minority of familial as well as sporadic TGCT. They also lend support to the hypothesis that KIT mutations primarily take place during embryogenesis such that primordial germ cells with KIT mutations are distributed to both testes.