Abstract
Thyroid cancer is the most commonly diagnosed endocrine cancer, with the incidence of 14.42 per 100,000 person-years in 2010-2013. It is important to conduct an in-depth exploration into the molecular mechanisms of thyroid cancer, providing insights into the improvements of therapy. Long non-coding RNAs (lncRNAs) act as oncogenes or tumor suppressors in thyroid cancer by sponging microRNAs (miRNAs), however, the functions of numerous lncRNAs are still unknown. In the present study, via the comprehensive analysis of microarray data derived from papillary thyroid tumors and the RNA sequencing of thyroid tumors from The Cancer Genome Atlas database, EGF like and EMI domain containing 1 (EGFEM1P) expression levels in papillary thyroid tumors and normal adjacent tissues were explored. Reverse transcription-quantitative PCR was used to detect EGFEM1P, microRNA (miR)-369-3p and T cell factor 4 (TCF4) expression levels. Western blotting was used to detect TCF4 protein and cleaved caspase-3/8 expression levels. Cell proliferative ability and apoptosis were assessed using the Cell Counting Kit-8 assay and flow cytometry, respectively. The interactions between EGFEM1P and miR-369-3p, and miR-369-3p and TCF4, were determined using the dual-luciferase reporter assay. The results demonstrated that EGFEM1P was upregulated in papillary thyroid tumors and thyroid cancer cells compared with normal adjacent tissues and human normal thyroid epithelial Nthy-ori 3-1 cell line. In the examined thyroid cancer cells, EGFEM1P was demonstrated to interact with miR-369-3p and decreased miR-369-3p expression levels. Thereafter, TCF4 was determined to be a target gene of miR-369-3p and EGFEM1P promoted TCF4 expression via regulating miR-369-3p expression levels. At last, it was found that EGFEM1P expression promoted rapid cell proliferation and inhibited cell apoptosis in thyroid cancer cells via acting as a miR-369-3p sponge. In conclusion EGFEM1P promoted thyroid cancer progression via acting as a sponge of the miR-369-3p/TCF4 axis.