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Updated: Jul 27, 2026
Tailoring In Vivo Cytotoxicity Assays to Study Immunodominance in Tumor-specific CD8+ T Cell Responses
Published on: May 6, 2019
Alterations in signal transduction molecules in T lymphocytes from tumor-bearing mice
H Mizoguchi1, J J O'Shea, D L Longo
1Biological Response Modifiers Program, National Cancer Institute, Frederick Cancer Research and Development Center, MD 21702.
Abstract:
Impaired immune responses occur frequently in cancer patients or in tumor-bearing mice, but the mechanisms of the tumor-induced immune defects remain poorly understood. In an in vivo murine colon carcinoma model (MCA-38), animals bearing a tumor longer than 26 days develop CD8+ T cells with impaired cytotoxic function, decreased expression of the tumor necrosis factor-alpha and granzyme B genes, and decreased ability to mediate an antitumor response in vivo. T lymphocytes from tumor-bearing mice expressed T cell antigen receptors that contained low amounts of CD3 gamma and completely lacked CD3 zeta, which was replaced by the Fc epsilon gamma-chain. Expression of the tyrosine kinases p56lck and p59fyn was also reduced. These changes could be the basis of immune defects in tumor-bearing hosts.
Insights
Tumor growth impairs CD8+ T cell function by altering T cell receptor components and reducing key signaling molecules. This study identifies molecular changes contributing to immune defects in cancer patients.
Area of Science:
- Immunology
- Oncology
- Molecular Biology
Background:
- Cancer patients and tumor-bearing animals often exhibit impaired immune responses, but the underlying mechanisms are not fully understood.
- Tumor-induced immune suppression is a significant barrier to effective cancer therapy.
Purpose of the Study:
- To investigate the molecular mechanisms behind tumor-induced immune defects in a murine colon carcinoma model.
- To identify specific changes in T lymphocytes that correlate with impaired anti-tumor immunity.
Main Methods:
- Utilized an in vivo murine colon carcinoma model (MCA-38).
- Analyzed CD8+ T cell function, including cytotoxic activity and gene expression (tumor necrosis factor-alpha, granzyme B).
- Examined T cell receptor (TCR) complex components (CD3 gamma, CD3 zeta) and associated tyrosine kinases (p56lck, p59fyn) in tumor-bearing mice.
Main Results:
- Mice with tumors longer than 26 days showed CD8+ T cells with reduced cytotoxic function and decreased expression of tumor necrosis factor-alpha and granzyme B.
- T lymphocytes from tumor-bearing mice exhibited altered TCRs, with low CD3 gamma, absent CD3 zeta, and replacement by the Fc epsilon gamma-chain.
- Expression of tyrosine kinases p56lck and p59fyn was significantly reduced in T cells from tumor-bearing hosts.
Conclusions:
- The observed alterations in TCR components and reduced tyrosine kinase expression provide a molecular basis for the impaired T cell function in tumor-bearing hosts.
- These findings contribute to understanding tumor-induced immune suppression and may inform strategies to restore anti-tumor immunity.
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