NKG2D Ligands-Critical Targets for Cancer Immune Escape and Therapy
Dominik Schmiedel1, Ofer Mandelboim1
1The Lautenberg Center for General and Tumor Immunology, The BioMedical Research Institute Israel Canada of the Faculty of Medicine, The Hebrew University Hadassah Medical School, Jerusalem, Israel.
Abstract:
DNA damage, oncogene activation and excessive proliferation, chromatin modulations or oxidative stress are all important hallmarks of cancer. Interestingly, all of these abnormalities also induce a cellular stress response. By upregulating "stress-induced ligands," damaged or transformed cells can be recognized by immune cells and cleared. The human genome encodes eight functional "stress-induced ligands": MICA, MICB, and ULBP1-6. All of them are recognized by a single receptor, NKG2D, which is expressed on natural killer (NK) cells, cytotoxic T cells and other T cell subsets. The NKG2D ligand/NKG2D-axis is well-recognized as an important mediator of anti-tumor activity; however, patient data about the role of NKG2D ligands in immune surveillance and escape appears conflicting. As these ligands are often actively transcribed, tumor cells are urged to manipulate the expression of these ligands on post-transcriptional or post-translational level. Although our knowledge on the regulation of NKG2D ligand expression remains fragmentary, research of the past years revealed multiple cellular mechanisms that are adopted by tumor cells to reduce the expression of "stress-induced ligands" and therefore escape immune recognition. Here, we review the post-transcriptional and post-translational mechanisms by which NKG2D ligands are modulated in cancer cells and their impact on patient prognosis.We discuss controversies and approaches to apply our understanding of the NKG2D ligand/NKG2D-axis for cancer therapy.
Insights
Cancer cells evade immune detection by downregulating stress-induced ligands, which normally signal immune cells. This review explores how tumors manipulate these NKG2D ligands to escape the immune system and discusses therapeutic strategies.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Cancer hallmarks like DNA damage and oxidative stress trigger cellular stress responses.
- Stress-induced ligands (MICA, MICB, ULBP1-6) are upregulated by stressed cells to signal immune cells via the NKG2D receptor.
- The NKG2D ligand/NKG2D-axis is crucial for anti-tumor immunity, but its role in cancer immune surveillance is debated.
Purpose of the Study:
- To review post-transcriptional and post-translational mechanisms of NKG2D ligand modulation in cancer cells.
- To analyze the impact of these modulations on patient prognosis.
- To discuss controversies and therapeutic applications of the NKG2D ligand/NKG2D-axis in cancer therapy.
Main Methods:
- Literature review of studies on NKG2D ligand regulation in cancer.
- Analysis of patient data regarding NKG2D ligand expression and prognosis.
- Discussion of cellular mechanisms and therapeutic strategies related to the NKG2D axis.
Main Results:
- Tumor cells actively downregulate NKG2D ligands through post-transcriptional and post-translational modifications to evade immune recognition.
- Mechanisms include transcriptional silencing, altered mRNA stability, and protein degradation.
- Dysregulation of NKG2D ligands impacts anti-tumor immune responses and patient outcomes.
Conclusions:
- Understanding NKG2D ligand regulation is key to overcoming tumor immune escape.
- Targeting these mechanisms offers potential for novel cancer immunotherapies.
- Further research is needed to resolve conflicting patient data and optimize therapeutic strategies.
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