The polymorphism rs944289 predisposes to papillary thyroid carcinoma through a large intergenic noncoding RNA gene of tumor suppressor type

Abstract

A genome-wide association study of papillary thyroid carcinoma (PTC) pinpointed two independent SNPs (rs944289 and rs965513) located in regions containing no annotated genes (14q13.3 and 9q22.33, respectively). Here, we describe a unique, long, intergenic, noncoding RNA gene (lincRNA) named Papillary Thyroid Carcinoma Susceptibility Candidate 3 ( PTCSC3 ) located 3.2 kb downstream of rs944289 at 14q.13.3 and the expression of which is strictly thyroid specific. By quantitative PCR, PTCSC3 expression was strongly down-regulated ( P = 2.84 × 10 −14 ) in thyroid tumor tissue of 46 PTC patients and the risk allele (T) was associated with the strongest suppression (genotype [TT] ( n = 21) vs. [CT] ( n = 19), P = 0.004). In adjacent unaffected thyroid tissue, the genotype [TT] was associated with up-regulation of PTCSC3 ([TT] ( n = 21) vs. [CT] ( n = 19), P = 0.034). The SNP rs944289 was located in a binding site for the CCAAT/enhancer binding proteins (C/EBP) α and β. The risk allele destroyed the binding site in silico. Both C/EBPα and C/EBPβ activated the PTCSC3 promoter in reporter assays ( P = 0.0009 and P = 0.0014, respectively) and the risk allele reduced the activation compared with the nonrisk allele (C) ( P = 0.026 and P = 0.048, respectively). Restoration of PTCSC3 expression in PTC cell line cells (TPC-1 and BCPAP) inhibited cell growth ( P = 0.002 and P = 0.019, respectively) and affected the expression of genes involved in DNA replication, recombination and repair, cellular movement, tumor morphology, and cell death. Our data suggest that SNP rs944289 predisposes to PTC through a previously uncharacterized, long intergenic noncoding RNA gene ( PTCSC3 ) that has the characteristics of a tumor suppressor.