Cancer immunology is the study of how the immune system interacts with cancer—both in recognizing and eliminating tumor cells, and in how tumors evade immune responses. It forms the foundation of modern immunotherapies, which aim to harness the immune system to treat cancer.

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### 🧬 Key Concepts in Cancer Immunology

#### 1. Immunosurveillance - The immune system constantly scans for abnormal cells. - Tumor cells can be destroyed before they form detectable cancers. - This process involves cytotoxic T cells, NK cells, and macrophages.

#### 2. Immunoediting This is a dynamic process in three phases: - Elimination: Immune system destroys tumor cells. - Equilibrium: Some tumor cells survive but are kept in check. - Escape: Tumors evolve to evade immune detection and grow uncontrollably.

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### 🧪 Key Players

- Cytotoxic CD8+ T cells: Kill tumor cells directly. - Helper CD4+ T cells: Support immune response via cytokine release. - Regulatory T cells (Tregs): Suppress anti-tumor immunity (often hijacked by tumors). - Tumor-associated macrophages (TAMs): Can promote or suppress tumor growth. - Myeloid-derived suppressor cells (MDSCs): Inhibit T cell responses. - Dendritic cells (DCs): Present tumor antigens to T cells.

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### 🧠 Tumor Immune Evasion Strategies

- Downregulating MHC class I to avoid T cell recognition - Expressing immune checkpoint ligands (e.g., PD-L1) to turn off T cells - Creating an immunosuppressive microenvironment (e.g., via TGF-β, IL-10) - Recruiting Tregs and MDSCs to suppress immunity - Shedding antigens or mutating to avoid immune recognition

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### 💉 Immunotherapy Approaches

1. Checkpoint inhibitors

1. Block inhibitory signals like PD-1/PD-L1 and CTLA-4
2. Boost T cell activity (e.g., nivolumab, pembrolizumab)

2. CAR-T cell therapy

1. T cells engineered to express chimeric antigen receptors targeting specific cancer antigens (e.g., CD19 in B-cell malignancies)

3. Cancer vaccines

1. Stimulate immune system to recognize tumor antigens

4. Oncolytic viruses

1. Viruses that selectively infect and kill tumor cells while activating immunity

5. Cytokine therapies

1. IL-2, IFN-α to boost immune responses (though with side effects)

6. Bi-specific T cell engagers (BiTEs)

1. Link T cells to cancer cells (e.g., blinatumomab)

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### 🧬 Current Research & Challenges

- Tumor heterogeneity: Different clones may escape immune detection. - Immune-related adverse events (irAEs) from overactivation of the immune system - Non-responsive tumors: “Cold tumors” that lack T cell infiltration - Development of biomarkers to predict response to therapy (e.g., PD-L1 expression, tumor mutational burden)

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### 🔬 Clinical Examples

- Melanoma: Among the first cancers successfully treated with checkpoint inhibitors - Lung cancer: Improved survival with PD-1/PD-L1 inhibitors - Glioblastoma: Immunotherapy is under investigation but faces immune privilege of the brain and a suppressive microenvironment

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### 📌 Take-home Message

Cancer immunology reveals the complex battle between tumors and the immune system. By understanding and manipulating this interaction, immunotherapy has revolutionized oncology, especially for cancers once considered untreatable.