A susceptibility locus for papillary thyroid carcinoma on chromosome 8q24.

Papillary thyroid carcinoma (PTC) displays higher heritability than most other cancers. To search for genes predisposing to PTC, we performed a genome-wide linkage analysis in a large family with PTC and melanoma. Among several peaks the highest was at 8q24, with a maximum nonparametric linkage (NPL) score of 7.03. Linkage analysis was then broadened to comprise 25 additional PTC families that produced a maximum NPL score of 3.2, P = 0.007 at the 8q24 locus. Fine mapping with microsatellite markers was compatible with linkage to the 8q24 locus in 10 of the 26 families. In the large family, a approximately 320 Kb haplotype was shared by individuals with PTC, melanoma, or benign thyroid disease, but not by unaffected individuals. A 12 Kb haplotype of 8 SNP markers within the larger haplotype was shared by 9 of the 10 families in which the 8q24 locus was compatible with linkage. The shared haplotype is located within 2 known overlapping protein-coding genes, thyroglobulin (TG) and Src-like adaptor (SLA). Resequencing of the coding and control regions of TG and SLA did not disclose putative mutations in PTC patients. Embedded in the TG-SLA region are three likely noncoding RNA genes, one of which (AK023948) harbors the 8-SNP haplotype. Resequencing of AK023948 and one of the other RNA genes did not reveal candidate mutations. Gene expression analysis indicated that AK023948 is significantly down-regulated in most PTC tumors. The putative noncoding RNA gene AK023948 is a candidate susceptibility gene for PTC.