A diagnostic and predictive lncRNA lnc-MPEG1-1 promotes the proliferation and metastasis of papillary thyroid cancer cells by occupying miR-766-5p

Long non-coding RNAs (lncRNAs) act as important biological regulators in human cancers. The purpose of this study was to identify promising biomarkers for improved diagnosis and prognosis of papillary thyroid cancer (PTC). We analyzed the lncRNA expression profile of PTC patients and identified five upregulated and three downregulated lncRNAs as diagnostic biomarkers for PTC in our cohorts, which were confirmed using The Cancer Genome Atlas (TCGA) data. Several lncRNAs have been linked with lymph node (LN) metastasis in patients with PTC. A nomogram combining two lncRNAs, lncMPEG1-1:1 and lnc-ABCA12-5:2, with age, T stage, histological type, and predicted LN metastasis was developed. The area under the curve of the developed nomogram was 0.77 (0.73???0.81) in the TCGA training cohort and 0.88 (0.79??? 0.96) in our validation cohort. In particular, in vivo and in vitro experiments showed that overexpression of lncMPEG1-1:1 in PTC cell lines promoted the proliferation and migration of PTC. lnc-MPEG1-1:1 is overexpressed in the cytoplasm of PTC cells and functionally promotes cellular proliferation and migration and functions as a competitive endogenous RNA (ceRNA) by competitively occupying the shared binding sequences of miR-766-5p. lnc-MPEG1-1:1 knockdown suppressed epithelial-mesenchymal transition by miR-766-5p in PTC cells. Collectively, these results revealed a lncMPEG1-1:1/miR-766-5p pathway for thyroid cancer progression and suggest that a nomogram effectively predicted the LN metastasis in PTC.