Circ-PKD2 promotes Atg13-mediated autophagy by inhibiting miR-646 to increase the sensitivity of cisplatin in oral squamous cell carcinomas

Autophagy is an evolutionally conserved catabolic process that degrades cells to maintain homeostasis. Cisplatin-activated autophagy promotes the expression of circ-PKD2, which plays a role as a tumor suppressor gene in the proliferation, migration, and invasion in oral squamous cell carcinoma (OSCC). However, the role of circ-PKD2 in regulating the sensitivity of OSCC patients to cisplatin remains to be elucidated. Overexpression of circ-PKD2 increased the formation of autophagosomes in OSCC cells and activation of proteins, such as LC3 II/I. Its activation effect on autophagy was, however, alleviated by 3-MA. Bioinformatics analyses and double luciferases reporter assays conducted in this study confirmed the existence of targeted relationships between circ-PKD2 and miR-646 and miR-646 and Atg13. Functional experiments further revealed that miR-646 reversed the autophagy and apoptosis effects of circ-PKD2 in OSCC cells treated with cisplatin. In addition, circ-PKD2 promoted the expression of ATG13 by adsorption of miR-646. Its interference with Atg13 alleviated the activation effects of circ-PKD2 on autophagy and apoptosis of miR-646. Notably, the in vivo animal experiments also confirmed that circ-PKD2 inhibited tumor proliferation and activated autophagy in OSCC cells. This study provides a theoretical basis for using circ-PKD2 as a target to regulate the sensitivity of OSCC patients to cisplatin, thus increasing its chemotherapeutic effects.