CBX8 promotes tumorigenesis and confers radioresistance in esophageal squamous cell carcinoma cells through targeting APAF1.

As a transcriptional repressor, Chromobox 8 (CBX8) overexpression is found to be associated with tumorigenesis in several cancers. However, its role in radiotherapy resistance remains poorly characterized. Our study is the first to explore the correlation between CBX8 and radioresistance. We report here that CBX8 is upregulated in Esophageal Squamous Cell Carcinoma (ESCC) tissues and cells and serves as an indicator of poor prognosis for ESCC patients. CBX8 knockdown inhibits cell proliferation, colony formation capability, DNA repair and promotes cell apoptosis. Moreover, the transcriptome sequencing analysis demonstrates that CBX8 downregulates the expression of Apoptotic protease activating factor 1 (APAF1), which is the core protein that mediates mitochondrial apoptotic pathways. APAF1 depletion could abrogate apoptosis induced by CBX8 knockdown in irradiated ESCC cells. Our results provide novel insight into CBX8 as a therapeutic target to improve the radiosensitivity of ESCC.