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Protective Efficacy and Pulmonary Immune Response Following Subcutaneous and Intranasal BCG Administration in Mice
Published on: September 19, 2016
NK cells mediate preventive efficacy of intravenous BCG against lung metastasis in mice
Claudia Guerrero1,2, Marta Casal1,2, Cristina Alierta1,2
1Grupo de Genética de Micobacterias, Departamento de Microbiología y Medicina Preventiva, Facultad de Medicina, Universidad de Zaragoza, IIS-Aragon, Zaragoza, Spain.
Abstract:
Lung metastases frequently arise from primary tumors, including bladder cancer, and represent a critical negative prognostic factor. Natural Killer (NK) cells have shown to play a vital role in controlling metastasis. Consequently, tumor cells have evolved specific mechanisms to evade NK cell-mediated immune surveillance, promoting metastasis and resistance to immunotherapy. In this study, we investigated the prophylactic and therapeutic potential of intravenous Bacillus Calmette-Guerin (BCG) in preventing lung metastases from bladder cancer cells using a murine model. We demonstrated that prophylactic BCG administration significantly reduced tumor burden and prolonged survival, largely through NK cell activation. However, BCG treatment was ineffective when administered over established tumors, likely due to tumor-driven immune evasion mechanisms. Our results revealed the contribution of interferon-gamma (IFN-γ) to tumor resistance. Tumor cells exposed to IFN-γ were more resistant to BCG in vivo, which correlated with the overexpression of immune checkpoint molecules, whereas disruption of the IFN-γ signaling pathway in tumor cells partially restored the therapeutic efficacy of BCG. Our findings highlight the importance of understanding tumor immune escape mechanisms and suggest that BCG could be a promising treatment for preventing lung metastases in bladder cancer.
Insights
Prophylactic Bacillus Calmette-Guerin (BCG) prevents lung metastases in bladder cancer by activating Natural Killer (NK) cells. However, BCG is ineffective against established tumors due to immune evasion, highlighting the need to understand these mechanisms.
Area of Science:
- Immunology
- Oncology
- Cancer Metastasis
Background:
- Lung metastases are a significant negative prognostic factor in bladder cancer.
- Natural Killer (NK) cells are crucial for controlling metastasis.
- Tumor cells develop mechanisms to evade NK cell surveillance, promoting metastasis and immunotherapy resistance.
Purpose of the Study:
- To investigate the prophylactic and therapeutic potential of intravenous Bacillus Calmette-Guerin (BCG) in preventing lung metastases from bladder cancer.
- To explore the role of NK cells and interferon-gamma (IFN-γ) in BCG efficacy and tumor immune evasion.
Main Methods:
- A murine model of bladder cancer lung metastasis was used.
- Prophylactic and therapeutic administration of intravenous BCG was evaluated.
- NK cell activation, tumor burden, survival rates, and IFN-γ signaling pathways were assessed.
Main Results:
- Prophylactic BCG significantly reduced tumor burden and prolonged survival, primarily through NK cell activation.
- BCG treatment was ineffective against established tumors, linked to tumor-driven immune evasion.
- Interferon-gamma (IFN-γ) exposure increased tumor resistance to BCG, associated with immune checkpoint molecule overexpression.
- Disrupting IFN-γ signaling partially restored BCG efficacy.
Conclusions:
- BCG shows promise as a prophylactic treatment to prevent lung metastases in bladder cancer.
- Understanding tumor immune escape mechanisms, particularly IFN-γ-mediated resistance, is critical for optimizing cancer immunotherapy.
- Targeting IFN-γ signaling may enhance the therapeutic efficacy of BCG for bladder cancer metastasis.
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