miR-744-5p mediates lncRNA HOTTIP to regulate the proliferation and apoptosis of papillary thyroid carcinoma cells.

Papillary thyroid carcinoma (PTC) is the most common malignancy in thyroid. miR-744–5p plays an efficient role in various cancers, but its role in PTC remains unknown. In this work, we aimed to explore the function of miR-744–5p and the mechanism by which miR-744–5p acted in PTC. We observed that miR-744–5p expression was significantly declined in PTC tissues and cell lines. The high level of miR-744–5p is significantly associated with a better clinical picture of PTC patients. Overexpression of miR-744–5p inhibited the proliferation, arrested the cell cycle, and promoted the apoptosis in PTC cells. Oppositely, down-regulation of miR-744–5p reversed the above tendencies. We also found that miR-744–5p down-regulated its downstream genes c-myc and attenuated cell proliferation induced by c-myc. Long non-coding RNA (lncRNA) HOTTIP was found to be up-regulated and to act as an oncogene in PTC. In this study, miR-744–5p bound to HOTTIP and was negatively regulated by HOTTIP. In conclusion, miR-744-5p acts as a tumor suppressor to inhibit proliferation and promotes the apoptosis of PTC cells via targeting c-myc. Moreover, miR-744-5p expression interferes with lncRNA HOTTIP ability to promote proliferation and downregulate apoptosis in papillary thyroid carcinoma.