MiR-618 inhibits anaplastic thyroid cancer by repressing XIAP in one ATC cell line.

X-linked inhibitor of apoptosis protein (XIAP) is a major factor in cancer growth and progression. Reduction of XIAP induces apoptosis of anaplastic thyroid cancer (ATC), which accounts for more than 50% of thyroid cancer mortality. MicroRNAs (miRNAs) are short non-coding RNA molecules, which modulate gene expression via interaction with mRNA by binding to the 3'-untranslated region (3'-UTR), playing a critical role in cell proliferation, migration, and invasion. In this study, we recruited the ATC cell line 8305C and normal human thyroid cell Nthy-ori 3-1, aiming to find the miRNA which could regulate XIAP and therefore inhibit the growth and invasion of ATC. We first used quantitative real-time PCR (qPCR) to reveal that XIAP mRNA expression was 4.6±0.56 folds (P=0.029) up-regulated in 8305C cells, compared with Nthy-ori 3-1 cells. Then miR-618, predicted to target XIAP directly, was detected 0.24±0.06 folds (P=0.019) down-regulated in 8305C cells. Next we used Luciferase assay showing that XIAP was a target gene of miR-618, which could repress the XIAP expression at both mRNA and protein levels. After that, CCK-8 assay was performed to show that over-expression of miR-618 could inhibit the growth of 8305C cells. Finally, we employed transwell method to prove that miR-618 could prevent the invasion and migration of 8305C cells. In conclusion, our collective data showed that over-expression of miR-618 could inhibit ATC cells by targeting XIAP gene.