Genetic heterogeneity in familial nonmedullary thyroid carcinoma: Exclusion of linkage to RET, MNG1, and TCO in 56 families

Epidemiological studies show a very high relative risk for first degree rel atives of probands with thyroid cancer. The familial form of nonmedullary t hyroid carcinoma (NMTC) gives a more severe phenotype and appears earlier t han its sporadic counterpart. Moreover, benign thyroid pathologies are ofte n observed in NMTC kindreds. Little is known about the genetic risk factors of the disease. To study them, an international consortium has been organi zed at the International Agency for Research on Cancer over the past 2 yr t o collect biological samples from NMTC families. The only genes known to be directly involved in susceptibility to NMTC are MNG1 on chromosome 14q32 a nd TCO on chromosome 19q13.2, previously localized by us and others. In add ition to those two genes, the genes for Cowden's syndrome and familial aden omatous polyposis are associated with thyroid cancer, but not as an indicat ive phenotype. Another important gene in thyroid carcinogenesis is RET, whi ch is mutated in the majority of cases of hereditary medullary thyroid canc er and rearranged in an important fraction of sporadic cases of NMTC. Here we report the result of a linkage analysis performed on the 56 more informa tive kindreds we have collected through the international consortium. Linka ge analysis using both parametric and nonparametric methods excluded MNG1, TCO, and RET as major genes of susceptibility to NMTC and demonstrated that this trait is characterized by genetic heterogeneity.