CBX2 Expression in Colorectal Mucosa-adenoma-adenocarcinoma Sequence

Objective To investigate the expression of chromobox 2 (CBX2) in colorectal adenoma (CRA) and colorectal cancer (CRC), and analyse its correlation with various clinicopathological parameters. Study design Observational study. Place and duration of study Pathology Department, Huashan Hospital, Fudan University, from December 2019 to December 2020. Methodology The mRNA level of CBX2 in colorectal mucosa, CRA and CRC was evaluated in gene expression profiling interactive analysis (GEPIA) and gene expression omnibus (GEO) dataset, then verified by quantitative real-time PCR (qRT-PCR). CBX2 expression by immunohistochemistry was determined in 122 samples, then its correlation was analysed with various clinicopathological parameters. Diagnostic value of CBX2 was estimated by the receiver operating characteristic curve (ROC). Prognostic value of CBX2 mRNA expression was evaluated via the Kaplan-Meier method in GEPIA. Results CBX2 expression rate in CRC (89.8%) was greater than adenoma (37.74%) and mucosa (20%). CBX2 protein levels were highest in adenocarcinoma and lowest in mucosa with intermediate level in adenoma. The area under curve (AUC) of CBX2 was 0.810 and 0.734, respectively, in distinguishing CRA from mucosa and CRC from CRA. CBX2 hyperexpression was not significantly correlated with clinicopathological variables, either in CRA or CRC. Kaplan-Meier survival analysis revealed that CBX2 mRNA hyperexpression was not associated with overall survival (OS) of CRC. Although the disease-free survival (DFS) of high CBX2 patients was shorter than those with low expression, but no obvious significance was found in colon adenocarcinoma (COAD, p=0.052) and rectal adenocarcinoma (READ, p=0.097). Conclusion CBX2 expression progressively increased in the sequence of mucosa-adenoma-carcinoma, which may be used as a diagnostic biomarker and therapeutic target for CRA and CRC. Key Words: CBX2, Colorectal adenoma, Colorectal cancer, Biomarker.