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Functional Characterization of Regulatory Macrophages That Inhibit Graft-reactive Immunity
Published on: June 7, 2017
Targeting RARγ Decreases Immunosuppressive Macrophage Polarization and Reduces Tumor Growth
Jihyeon Park1, Jisun Oh2, Sang-Hyun Min3
1College of Pharmacy, Kyungpook National University, Daegu 41566, Republic of Korea.
Abstract:
Tumor-associated macrophages (TAMs) play a critical role in the tumor microenvironment (TME), interacting with cancer cells and other components to promote tumor growth. Given the influence of TAMs on tumor progression and resistance to therapy, regulating the activity of these macrophages is crucial for improving cancer treatment outcomes. TAMs often exhibit immunosuppressive phenotypes (commonly referred to as M2-like macrophages), which suppress immune responses and contribute to drug resistance. Therefore, inhibiting immunosuppressive polarization offers a promising strategy to impede tumor growth. This study revealed retinoic acid receptor gamma (RARγ), a nuclear receptor, as a key regulator of immunosuppressive polarization in THP-1 macrophages. Indeed, the inhibition of RARγ, either by a small molecule or gene silencing, significantly reduced the expression of immunosuppressive macrophage markers. In a three-dimensional tumor spheroid model, immunosuppressive macrophages enhanced the proliferation of HCT116 colorectal cancer cells, which was significantly hindered by RARγ inhibition. These findings suggest that targeting RARγ reprograms immunosuppressive macrophages and mitigates the tumor-promoting effects of TAMs, highlighting RARγ as a promising therapeutic target for developing novel anti-cancer strategies.
Insights
Targeting retinoic acid receptor gamma (RARγ) reprograms immunosuppressive tumor-associated macrophages (TAMs). Inhibiting RARγ reduces immunosuppressive markers and hinders cancer cell proliferation, offering a novel anti-cancer strategy.
Area of Science:
- Immunology
- Oncology
- Molecular Biology
Background:
- Tumor-associated macrophages (TAMs) are key players in the tumor microenvironment (TME), promoting tumor growth and therapy resistance.
- TAMs often display immunosuppressive M2-like phenotypes, hindering anti-tumor immune responses.
- Regulating TAM activity is crucial for improving cancer treatment outcomes.
Purpose of the Study:
- To identify key regulators of immunosuppressive polarization in TAMs.
- To investigate the role of retinoic acid receptor gamma (RARγ) in TAM function.
- To evaluate RARγ inhibition as a potential therapeutic strategy against cancer.
Main Methods:
- Utilized THP-1 macrophages to study immunosuppressive polarization.
- Employed small molecule inhibitors and gene silencing to inhibit RARγ.
- Assessed the expression of immunosuppressive macrophage markers.
- Used a three-dimensional tumor spheroid model with HCT116 colorectal cancer cells.
Main Results:
- Retinoic acid receptor gamma (RARγ) was identified as a key regulator of immunosuppressive macrophage polarization.
- Inhibition of RARγ significantly reduced the expression of immunosuppressive macrophage markers.
- RARγ inhibition hindered the proliferation of colorectal cancer cells in a tumor spheroid model.
Conclusions:
- Targeting RARγ reprograms immunosuppressive TAMs towards a less tumor-promoting phenotype.
- RARγ inhibition mitigates the pro-tumorigenic effects of TAMs.
- RARγ represents a promising therapeutic target for novel anti-cancer strategies.
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