Positive feedback loop SP1/SNHG1/miR-199a-5p promotes the malignant properties of thyroid cancer

Abstract Abundant evidences have demonstrated the essential roles of long noncoding RNA (lncRNA) in the papillary thyroid cancer (PTC). Here, we aim to explore the biological roles of lncRNA SNHG1 in the PTC tumorigenesis. Firstly, we discovered the ectopically expressed ncRNAs using lncRNA microarray profiling. Among these candidate lncRNAs, SNHG1 was identified to be up-regulated in both PTC tissue and cells. Functionally, knockdown of SNHG1 repressed the proliferation, invasion and tumor growth in vitro and in vivo. Mechanistically, SNHG1 sponged miR-199a-5p by complementary binding with specificity protein 1 (SP1) 3′-UTR. Interestingly, transcription factor SP1 targeted the promoter region of SNHG1 to promote its transcriptional level. The interaction within lncRNA, miRNA and target mRNA constructed the feedback loop of SP1/SNHG1/miR-199a-5p/SP1 in PTC. Collectively, these findings unveil the potential regulation of SNHG1 on the PTC tumorigenesis via feedback loop, providing a novel insight for PTC.