STAT6 suppresses cervical cancer progression through DDX1-mediated transcriptional activation of GADD45A

Cervical cancer remains a major threat to women's health, and its molecular mechanisms require further investigation. Signal transducer and activator of transcription 6 (STAT6) has context-dependent functions in malignancy, but its role in cervical cancer remains unclear. Here, we found that STAT6 expression was reduced overall in cervical cancer tissues and cell lines. STAT6 overexpression inhibited cervical cancer cell proliferation, migration, invasion, and epithelial-mesenchymal transition-associated phenotypes, whereas STAT6 depletion exerted the opposite effects. STAT6 overexpression also suppressed xenograft tumor growth. Mechanistically, GADD45A was identified as a direct transcriptional target of STAT6. RT-qPCR and Western blot analyses showed that STAT6 positively regulated GADD45A expression, while luciferase reporter and ChIP-qPCR assays demonstrated that STAT6 bound to site 3 of the GADD45A promoter and enhanced its transcriptional activity. DDX1 was subsequently identified as a STAT6-interacting protein by IP-MS and validated by reciprocal Co-IP assays. DDX1 depletion reduced STAT6 occupancy at the GADD45A promoter, whereas DDX1 promoted the association between STAT6 and the transcriptional co-activator p300. Furthermore, p300 depletion attenuated the DDX1-induced increases in GADD45A promoter activity and endogenous GADD45A expression, indicating that DDX1 enhances STAT6-dependent transcription at least partially through p300. GADD45A depletion partially reversed the inhibitory effects of STAT6 on malignant phenotypes in vitro and tumor growth in vivo. Consistently, STAT6 overexpression increased GADD45A expression and reduced Ki-67 staining in xenograft tissues, whereas GADD45A depletion partially reversed these changes. Collectively, our findings identify a STAT6-DDX1-GADD45A regulatory axis in cervical cancer. DDX1 enhances STAT6-dependent GADD45A transcription by facilitating STAT6 promoter occupancy and its association with p300, thereby contributing to the tumor-suppressive effects of STAT6. These results provide mechanistic insight into the regulation of cervical cancer progression.