Abstract

Purpose
This study examined the roles of nuclear factor erythroid 2-related factor 2 (NRF2) and programmed death ligand 1 (PD-L1) in colon carcinogenesis, underscoring on sex and differences in tumor location.
Materials and Methods
A total of 378 participants were enrolled from Seoul National University Bundang Hospital: 88 healthy controls (HC), 139 patients with colorectal adenoma (AD), and 151 patients with colorectal cancer (CRC). Quantitative real-time polymerase chain reaction (PCR), methylation-specific PCR, and immunohistochemistry (IHC) were performed utilizing tumor samples from patients and normal mucosa in the HC group.
Results
NRF2 mRNA expression was higher in the CRC group than in the HC and AD groups, with decreased NRF2 methylation in the AD and CRC groups. NRF2 protein expression, as evaluated by IHC, increased in the AD and CRC groups relative to that in the HC group. PD-L1 protein expression was remarkably higher in the CRC group than in the HC and AD groups. These patterns were consistent in both males and females. In sex- and CRC location-specific analyses, NRF2 methylation was lower in female than in male patients with CRC. NRF2 protein expression was significantly higher in females, particularly in patients with right-sided CRC. Moreover, females exhibited increased PD-L1 mRNA expression compared to males in the AD group, and PD-L1 mRNA levels were higher in females with right-sided CRC than in those with cancer at other locations.
Conclusion
Differences in NRF2 and PD-L1 expression indicate site-specific colon carcinogenesis based on sex, particularly in females with right-sided CRC.

• Keywords: Carcinogenesis, Sex characteristics, Nuclear factor erythroid 2-related factor 2, Programmed death ligand 1