Study on the mechanism of circ-PDE5A inhibiting the progression of esophageal squamous cell carcinoma

Objective: Esophageal squamous carcinoma (ESCC) is one of the most common gastrointestinal tumors, and the PI3K/AKT signaling pathway plays a key role in the development of ESCC. circRNAs have been reported to be involved in the regulation of PI3K/AKT signaling, but the underlying mechanisms are unclear. This study aimed to identify protein-coding circRNAs and investigate their function in ESCC. Design: Differential expression of circRNAs between ESCC tissues and adjacent normal tissues was identified using circRNA microarray analysis. A novel protein encoded by circ-PDE5A was identified by LC-MS/MS. Molecular biological methods were used to explore the biological functions and regulatory mechanisms of circ-PDE5A and its encoded PDE5A-500aa novel protein in ESCC. Construction of a nanoplatform for the coupling of circRNAs to investigate the therapeutic translation value of circ-PDE5A. Results: We found that circ-PDE5A expression was downregulated in ESCC cells and tissues, and its low expression was associated with later clinicopathological staging and poorer prognosis. Functionally, circ-PDE5A inhibited ESCC proliferation and metastasis in vitro and in vivo by encoding the novel PDE5A-500aa protein, which was identified as a key player in regulating PI3K/AKT signaling activation in ESCC. Mechanistically, the novel PDE5A-500aa protein binds directly to PIK3IP1 and promotes USP14-mediated deubiquitination of the k48-linked polyubiquitin chain at residue K198 of PIK3IP1, thereby attenuating PI3K/AKT pathway in ESCC. In addition, the circ-PDE5A plasmid-coupled reduction-responsive nanoplatform successfully inhibited ESCC growth and metastasis. Conclusions: circ-PDE5A represents an epigenetic mechanism regulating PI3K/ATK signaling and serves as a novel and promising therapeutic target and prognostic marker for ESCC. Three pairs of ESCC tissues and adjacent normal tissues were analyzed for differentially expressed circRNA using the Arraystar Human circRNA Array analysis.