Background

Papillary thyroid carcinoma is the most frequent histological subtype of thyroid cancer with a high incidence. We aimed to explore the function of circular RNA_0039411 (circ_0039411) and its associated mechanism in papillary thyroid carcinoma progression.

Methods

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot assay were conducted to determine the expression of RNA and protein, respectively. The colony formation ability, migration, invasion, and apoptosis were analyzed by colony formation assay, transwell migration assay, transwell invasion assay, and flow cytometry. Cell glycolytic metabolism was analyzed using fluorescence-based glucose assay kit and fluorescence-based lactate assay kit. Dual-luciferase reporter assay and RNA-Pull-Down Assay were performed to validate the binding between microRNA-423-5p (miR-423-5p) and circ_0039411 or SRY-box transcription factor 4 (SOX4). The xenograft tumor model was used to assess the role of circ_0039411 in the tumor growth in vivo.

Results

Circ_0039411 was highly expressed in papillary thyroid carcinoma tissues and cell lines compared with adjacent normal tissues and NTHY-ORI3.1 cells. Circ_0039411 interference suppressed the colony formation ability, migration, invasion, and glycolysis but promoted the apoptosis of papillary thyroid carcinoma cells. MiR-423-5p was a target of circ_0039411 in papillary thyroid carcinoma cells. Circ_0039411 knockdown-mediated effects in papillary thyroid carcinoma cells were largely overturned by the silence of miR-423-5p. MiR-423-5p bound to the 3′ untranslated region (3′UTR) of SOX4. SOX4 overexpression largely reversed circ_0039411 silencing-mediated effects in papillary thyroid carcinoma cells. Circ_0039411 positively regulated SOX4 expression by sponging miR-423-5p in papillary thyroid carcinoma cells. Circ_0039411 silencing notably suppressed the growth of xenograft tumors in vivo.

Conclusion

Circ_0039411 promoted the malignant behaviors of papillary thyroid carcinoma cells partly depending on the regulation of the miR-423-5p/SOX4 axis.