XRN2, governed by RNA-binding protein PTBP3, promotes the invasiveness of esophageal squamous cell carcinoma

Metastasis contributes to treatment failure and poor prognosis of esophageal squamous cell carcinoma (ESCC) patients. The 5'-3' exoribonuclease 2 (XRN2) is related to the pathogenesis and progression of various malignancies through its roles in transcription termination and metastasis promotion, but its function in ESCC remains unclear. Bioinformatic analysis showed that XRN2 was significantly overexpressed in ESCC tissues and was identified as a risk factor for ESCC patients. The analysis of our own cohort confirmed that XRN2 expression was overexpressed and significantly correlated with cancer stage in patients (P = 0.0100). Gain- and loss- of function analyses revealed that XRN2 promoted ESCC cell growth, migration and invasion capabilities, as well as experimental lung colonization foci. Interestingly, we found that the RNA level of XRN2 was upregulated by the RNA-binding protein polypyrimidine tract binding protein 3 (PTBP3). Specifically, PTBP3 bound to CUUUC motifs of the 3'UTR of XRN2, prolonging the half-life of XRN2 RNA. PTBP3 was found to be significantly overexpressed in ESCC, where its expression level correlated with tumor stage (P = 0.0164) and tumor size (P = 0.0495), positioning it as a risk factor for ESCC patients. PTBP3 upregulation promoted ESCC cell growth, migration, and invasion in vitro and in vivo. Notably, knockdown of XRN2 reversed the tumor promotion effects induced by PTBP3 overexpression. Collectively, our data reveal a novel function of XRN2 in ESCC metastasis and the critical roles of the PTBP3/XRN2 axis in ESCC metastasis, highlighting its promise as a novel therapeutic target in ESCC.