Thyroid cancer: tumor vs. precancerous lesions

Multiple lines of evidence have highlighted that long noncoding RNAs (lncRNAs) serve as a novel class of regulators of cancer biological processes. Currently, our knowledge of lncRNAs in papillary thyroid carcinoma (PTC) is still limited. Using microarray analysis, we identified a lncRNA (lncAB), which is downregulated in PTC. The decreased expression of lncAB is induced by CpG hypermethylation in the flanking region of lncAB. Overexpression of lncAB inhibited tumor growth and arrested G2/M phase in vitro and in vivo, whereas knockdown of lncAB promoted cell proliferation, colony formation, DNA replication ability, and increased G0/G1 phase. Mechanistic analyses revealed that lncAB binds to KHSRP, resulting in the mRNA degradation, high expression of CDKN1a and low expression of CDK2, and thereby repressed cell proliferation. Taken together, we provide evidence that lncAB is a tumor suppressor in PTC tumorigenesis and delineate a novel mechanism of lncRNA in PTC progression. The present study include three adults diagnosed as thyroid cancers. Total RNA was isolated for gene expression analysis that compares the two groups - tumor (n=3) and precancerous lesions (n=3) - in a pairwise manner. "lncAB" is a novel isoform of lncRNA AB074169, which was identified by RACE in thyroid cell line Nthy-ori 3. We have uploaded both isoform sequences to Genbank: BankIt2041199 Seq1(MF681781) and Seq2 (MF681782).