Hereditary non-polyposis colorectal cancer: identification of mutation carriers and assessing pathogenicity of mutations

Polymorphisms in XPD, XPC and the risk of death in patients with urinary bladder neoplasms

We conducted a follow-up study on 311 patients with urinary bladder neoplasms to investigate the association of polymorphisms in DNA repair and cell growth regulatory genes with the clinical outcomes of this disease. We found that patients carrying the variant allele of XPD (K751Q) polymorphism were at lower risk of death (p = 0.04) than the noncarriers. Patients that were simultaneous carriers of variant alleles from XPD (K751Q) and XPC (K939Q) polymorphisms, showed lower risk of death than the other patients (p = 0.001). The variant allele carriers of MSH6 (G39E) polymorphism showed a higher risk for highly malignant disease (TaG3 +T1) than the non-carriers (p = 0.03). The variant allele carriers of XRCC1 (R399Q) polymorphism showed lower risk for recurrence (TaG2; p = 0.05) and death (T2+; p = 0.03) after instillation and radiotherapy than the non-carriers. After radiotherapy, an inverse association of the variant allele of OGG1 (S326C) polymorphism was observed with the risk of death (T2 +; p = 0.04). A significant low-risk for stage progression (p = 0.03) was observed in patients carrying the variant allele of H-ras (H27H) polymorphism. Our results are consistent with the notion that the XPD (K751Q) polymorphism either individually or in combination with the XPC (K939Q) polymorphism modulates the risk of death in patients with urinary bladder neoplasms.

Two Swedish founder MSH6 mutations, one nonsense and one missense, conferring high cumulative risk of Lynch syndrome

Lynch syndrome, or hereditary non-polyposis colorectal cancer (HNPCC), is a cancer susceptibility syndrome caused by germline mutations in mismatch-repair genes, predominantly MLH1, MSH2 and MSH6. A majority of the mutations reported are truncating, but for MSH6, missense mutations constitute over one third. Few have been proven pathogenic in functional studies or shown to segregate in families. In this study, we show segregation of the putative pathogenic MSH6 missense mutation c.1346T>C p.Leu449Pro with microsatellite instability-high Lynch syndrome-related tumours lacking MSH6 expression in a large 17th century pedigree. Another large family with the MSH6 nonsense c.2931C>G, p.Tyr977X mutation is similar in tumour spectra, age of onset and cumulative risk. These MSH6 families, despite their late age of onset, have a high lifetime risk of all Lynch syndrome-related cancers, significantly higher in women (89% by age 80) than in men (69%). The gender differences are in part explained by high endometrial (70%) and ovarian (33%) cancer risks added upon the high colorectal cancer risk (60%). The several occurrences of breast cancer are not due to the MSH6 mutations. These findings are of great importance for counselling, management and surveillance of families with MSH6 mutations.

Case report: familial gastric cancer and chordoma in the same family

Gastric cancers are the second most common malignancy in the world and represent a major burden to all societies even though the incidence of disease is decreasing in the industrialized world. The aetiology of the disease is complex and is believed to be primarily due to environmental factors but a small proportion of cases are recognised as being associated with genetic factors. Two inherited forms of stomach cancer have been identified, one which is associated with familial clusterings of stomach cancer and the other being a subgroup of families that belong to hereditary non polyposis colorectal cancer (or Lynch syndrome). In this report we present a small nuclear family which is unusual in that there is a clustering of malignancy which includes stomach cancer, colorectal cancer and chordoma. Genetic analysis failed to reveal any causative mutation in genes associated with HNPCC or in E-cadherin. Together, the clinical picture in this family may indicate that other genetic factors are behind this family's clustering of malignancy.