SPC25 upregulates CCND1 to promote the progression of esophageal squamous cell carcinoma by MDM2-mediated E2F1 ubiquitination and stabilization

Abstract

Abstract Background The occurrence and development of esophageal squamous cell carcinoma (ESCC) are closely related to the overexpression of multiple oncogenes. Thus, it is of great urgent to explore new targets and therapeutic implications in ESCC. Methods We first identified the expression and interaction with prognosis of SPC25 in 88 primary ESCCs by IHC and verified by the Cancer Genome Atlas (TCGA) database. Then, stable shSPC25 cell lines of ESCC were constructed to evaluate its function of cell proliferation, migration, apoptosis, and cell cycle by western blot, Celigo cell counting, transwell, and flow cytometry analysis. Moreover, the potential mechanism was explored by performing microarray and bioanalysis and verified by RT‒qPCR, western blot, and rescue experiments in vitro and in vivo. Furthermore, coimmunoprecipitation, CHIP, luciferase reporter, and ubiquitination assays were performed to investigate the critical mechanism by which CCND1 affects SPC25 in ESCC. Results In this study, we identified that SPC25 is highly expressed in ESCC and promotes the proliferation, metastasis, and invasion of ESCC cells. Then, the underlying cellular mechanisms were explored. By performing microarray and bioanalysis, we found that CCND1 is a potential target of SPC25, and it is also upregulated in ESCC. Further experiments showed that E2F1, as the transcription factor of CCND1, is downregulated by the ubiquitination pathway after SPC25 knockdown, which in turn regulates the expression level of CCND1 in cells. In addition, SPC25 regulates E2F1 ubiquitination via the ubiquitin ligase MDM2. Conclusions Collectively, we demonstrated that the aberrant expression of SPC25 inhibited E2F1 ubiquitination to promote CCND1 expression, thus contributing to tumorigenesis, which provided new insights and therapeutic implications in ESCC.