How Cancer Escapes the Immune System

One of the most frightening capabilities of cancer cells is their ability to "evade the body's immune system." Normally, white blood cells like CD8+ T cells and NK cells should recognize and destroy cancer cells. However, cancer develops several strategies to survive and grow. Here’s how cancer escapes immunity:

1. Recruiting Immunosuppressive White Blood Cells

Cancer can attract immune cells that suppress immunity to work on its side, such as:

• Treg (Regulatory T cells): Secretes IL-10 to strongly suppress immune responses.
• MDSC (Myeloid-Derived Suppressor Cells): Releases various inhibitory substances and supports cancer growth.
• M2d Macrophages: Transitioned macrophages that promote angiogenesis and tumor-friendly environments.

2. Shutting Down Immune Cells via “Immune Checkpoints”

Cancer cells express proteins like PD-L1, binding to PD-1 on T cells and NK cells, effectively "switching off" their function.

3. Turning the Battlefield into an Acid Sea (Warburg Effect)

Cancer cells metabolize glucose into lactic acid (Warburg Effect), creating a highly acidic environment that:

• Weakens immune cell function
• Cuts off nutrients vital for immunity

4. Hiding by Reducing MHC I Expression

Cancer cells can downregulate or alter MHC Class I proteins, making it harder for T cells to recognize them as threats.

5. Sending a “Don’t Eat Me” Signal with CD47

When under attack, cancer cells express CD47 to signal macrophages: "I'm part of the body, don't destroy me."

6. Transforming Monocytes into Allies

Cancer secretes Semaphorins to prevent monocytes from differentiating into cancer-killing macrophages and instead converts them into M2d macrophages, which support cancer growth.