Analysis of ALK, IDH1, IDH2 and MMP8 somatic mutations in differentiated thyroid cancers

Anaplastic lymphoma kinase (ALK), isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) and matrix metalloproteinase 8 (MMP8) gene mutations have been frequently reported in human cancers; however, to the best of our knowledge, they have not been specifically examined in differentiated thyroid cancers (DTCs). Therefore, the present study aimed to determine the somatic mutational frequencies of these genes in DTCs. Mutational analysis of the ALK (exons 23, 24 and 25), IDH1 (exon 4), IDH2 (exon 4), and MMP8 (all exons 1-10) was performed in 126, 271, 271 and 50 DTCs, respectively. All the indicated exons were PCR-amplified and the PCR products were directly sequenced by Sanger sequencing. The present study identified a high frequency (86%; 43/50) of MMP8 single nucleotide polymorphism (SNP) and also found some rare SNPs of this gene (S3C, T32I, L310P and K460T) in DTCs but no somatic mutation in ALK, IDH1, IDH2 and MMP8. Analyses of 414 DTCs from The Cancer Genome Atlas revealed rare ALK (1%) and MMP8 (0.24%) mutations and none in IDH1 and IDH2. Conversely, analyses of 117 aggressive thyroid cancers [84, poorly differentiated thyroid cancer (PDTC); 33, anaplastic thyroid cancer (ATC)] from the Memorial Sloan Kettering Cancer Center cohort revealed ALK mutations in 3% of ATCs and fusions in 3.6% of PDTCs. IDH1 mutation was identified in 1.25% of PDTCs but not in ATC. IDH2 mutation was identified in 3% of ATCs but not in PDTC. The present study demonstrated that these genes are less frequently mutated in DTCs, but common in ATCs and PDTCs. It suggests that these genes serve a role in a small portion of DTCs and a more important role in ATCs and PDTCs and may serve as potential therapeutic targets in these subsets.