BRAF regulates circPSD3/miR-526b/RAP2A axis to hinder papillary thyroid carcinoma progression.

Background: Papillary thyroid carcinoma (PTC) is a common malignant tumor. BRAF mutation has become a common molecular event in PTC pathogenesis. Circular RNA PSD3 (circPSD3) is known to be highly expressed in PTC. However, the bio-functional role of circPSD3 and its possible relationship with the BRAF in PTC is not clear. This study aims to probe the biofunction and molecular mechanism of circPSD3 in PTC pathogenesis.

Methods: RT-qPCR was utilized to measure the expression of circPSD3 and BRAF in PTC tissues and cells. The CCK-8 and EdU assays were employed to assess cell viability and proliferation. Cell apoptosis was quantified using flow cytometry. The migratory and invasive capabilities of the cells were evaluated via wound healing and transwell assays. The interaction between RNAs was investigated using luciferase reporter assay. Additionally, xenograft tumor experiments were conducted to validate our findings in vivo.

Results: Data showed that circPSD3 was highly expressed in PTC patients and cell lines. CircPSD3 was found to promote cell growth and migration and inhibit apoptosis in PTC cells. Results also revealed that circPSD3 upregulated RAP2A expression by specifically sponging miR-526b. Interestingly, inhibiting miR-526b reversed the tumorigenic properties of circPSD3 in PTC. Additionally, BRAF expression was low in PTC patients, and overexpression of BRAF hampered PTC development by downregulating circPSD3 and RAP2A while upregulating miR-526b expressions.

Conclusions: Our study reveals that circPSD3 is a key regulator promoting PTC progression via the circPSD3/miR-526b/RAP2A pathway. Furthermore, we found that overexpressing BRAF, which inhibits circPSD3, significantly hampers the progression of PTC.