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Updated: Oct 26, 2025
An In Vivo Estrogen Deficiency Mouse Model for Screening Exogenous Estrogen Treatments of Cardiovascular Dysfunction After Menopause
Published on: August 13, 2019
The Enhanced Inhibitory Effect of Estrogen on PD-L1 Expression Following Nrf2 Deficiency in the AOM/DSS Model of
Changhee Kang1, Chin-Hee Song1, Nayoung Kim1,2
1Departments of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, South Korea.
Abstract:
Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a dual role in carcinogenesis. We previously reported that Nrf2 deficiency enhances the anti-tumorigenic effect of 17β-estradiol (E2) in an azoxymethane (AOM)/dextran sodium sulfate (DSS) model of colitis-associated cancer (CAC). Herein, we aimed to determine a possible explanation for our recent work and investigated the immune microenvironment represented by programmed death-ligand 1 (PD-L1) expression. One week after the AOM injection, mice were administered with DSS in drinking water for seven days; daily E2 injections were intraperitoneally administered during this period. The mice were sacrificed 16 weeks after AOM injection and analyzed for PD-L1 expression in the distal colon tissues using Western blotting and immunohistochemistry (IHC). Based on Western blotting results, PD-L1 expression was reduced in Nrf2 knockout (KO) female and E2-treated male mice when compared with their wild-type counterparts, following AOM/DSS treatment; this supports the association of PD-L1 expression with tumor progression. Additionally, this finding was in good agreement with the IHC results for PD-L1. Furthermore, we observed that PD-L1 is predominantly expressed in stromal cells rather than on epithelial cells in the colon. Western blotting revealed that PD-L1 expression in the colon positively correlates with expressions of inducible nitric oxide synthase (iNOS) (male, P = 0.002; female, P <0.001) and cyclooxygenase-2 (COX-2) (male, P <0.001; female, P <0.001). Collectively, our findings indicate that estrogen ameliorates the immune microenvironment represented by PD-L1 expression and enhances its effect in the absence of Nrf2.
Insights
Nuclear factor erythroid 2-related factor 2 (Nrf2) deficiency enhances 17β-estradiol
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Nuclear factor erythroid 2-related factor 2 (Nrf2) has a complex role in cancer development.
- Previous studies indicated Nrf2 deficiency amplifies 17β-estradiol's (E2) anti-tumor effects in colitis-associated cancer (CAC).
Purpose of the Study:
- To investigate the immune microenvironment, specifically programmed death-ligand 1 (PD-L1) expression, as a potential mechanism behind Nrf2's role in CAC.
- To explore the correlation between PD-L1, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) in the context of E2 treatment and Nrf2 status.
Main Methods:
- Utilized an azoxymethane (AOM)/dextran sodium sulfate (DSS) mouse model for CAC induction.
- Administered E2 and DSS to mice with varying Nrf2 statuses (wild-type and knockout).
- Analyzed PD-L1, iNOS, and COX-2 expression in colon tissues via Western blotting and immunohistochemistry (IHC).
Main Results:
- PD-L1 expression was reduced in Nrf2 knockout mice and E2-treated male mice, correlating with reduced tumor progression.
- PD-L1 was primarily expressed in stromal cells, not epithelial cells, of the colon.
- PD-L1 expression positively correlated with iNOS and COX-2 levels in both male and female mice.
Conclusions:
- Estrogen (E2) appears to improve the immune microenvironment by modulating PD-L1 expression.
- The anti-tumor effects of E2 may be enhanced in the absence of Nrf2, potentially through immune modulation.
- PD-L1, iNOS, and COX-2 are key components of the tumor microenvironment influenced by Nrf2 and E2 in CAC.
