CBX3 as a Prognostic Biomarker and Therapeutic Target in Colorectal Carcinoma

Abstract

Background

Colorectal cancer (CRC) is a common and lethal disease worldwide. The chromobox (CBX) protein family, integral to the Polycomb repressive complex 1 (PRC1), plays a crucial role in epigenetic regulation and the progression of cancer. The expression profiles, clinical importance, and roles of various CBX family members in CRC remain unclear, especially concerning nonepigenetic functions and roles in the tumor microenvironment.

Methods

The transcriptional profiles of the entire CBX family, consisting of eight members, were systematically analyzed using multiple public databases. Genomic alterations, prognostic data, and GSEA identified CBX3 as an important oncogenic gene. To explore CBX3 expression patterns and their association with immune cell infiltration in the tumor microenvironment, single-cell RNA sequencing was employed. Through experimental validation, cell proliferation, migration, apoptosis, and cell cycle analysis, the oncogenic role of CBX3 was confirmed. Experiments involving coimmunoprecipitation and immunofluorescence colocalization were performed to confirm protein–protein interactions and subcellular localization of the protein. The screening of the CMap was executed to find potential therapeutic compounds, sorted by CBX3 expression levels.

Results

The integrated analysis revealed a complicated expression pattern of CBX family members in CRC, with notable increases in CBX2, CBX3, CBX4, and CBX8, whereas CBX6 and CBX7 were decreased in tumor tissues. The prognostic analysis revealed that higher levels of CBX3, CBX4, CBX6, CBX7, and CBX8 were connected to lower overall survival rates, whereas increased CBX5 expression was associated with improved prognosis. Among all members, CBX3 was noted for having the highest frequency of alterations and the most frequent copy number gain, establishing it as a leading oncogenic driver. Single-cell analysis showed that CBX3 expression was predominantly found in malignant cells, and higher CBX3 levels were associated with increased infiltration of immunosuppressive regulatory T cells. CMap screening revealed that epidermal growth factor receptor (EGFR) inhibitors were the most significantly enriched compounds in the high CBX3 expression group. In vitro, reducing CBX3 expression decreased cell proliferation and migration, promoted apoptosis, and caused G2/M phase arrest in CRC cells. CBX3 interacts with EGFR, activating the PI3K/AKT signaling pathway and promoting epithelial–mesenchymal transition (EMT).

Conclusion

CBX3 was identified as a crucial oncogenic factor in CRC, enhancing tumor development through its interaction with EGFR and activation of the PI3K/AKT signaling pathway. CBX3 could be an indicator for predicting patient outcomes and their response to EGFR inhibitor treatment, which serves as a promising biomarker and a potential therapeutic target to advance precision medicine.