How Does Cancer Escape the Immune System?

How Does Cancer Escape the Immune System?

31 March 2016,   By ,   0 Comments

Researchers have long questioned how tumors can grow in a healthy immune system. This question is even more important today, as immune-targeted therapies are fundamentally changing what it means to treat cancer. 

New evidence suggests that tumor development is heavily influenced by our immune system. This theory, termed “cancer immuno-editing,” can be broken down into three phases: elimination, equilibrium, and escape. In this edition of Guided By Science, we explore the three phases of cancer immuno-editing to understand the battle between cancer and the immune system.

Elimination

Throughout our lives, the immune system will encounter abnormal cells and cancerous changes. In the elimination phase, the immune system recognizes and eliminates abnormal cells before they can become advanced cancers. Elimination is carried out by tumor-specific T cells, which are immune cells developed specifically to target and attack cancer. To better understand how the immune system attacks cancer, consider the figure below.

cancer elimination

Equilibrium

If tumor cells escape destruction, they can persist in a delicate balance of growth and immune suppression. During this equilibrium phase, the immune system is able to keep tumor cells from growing out of control, but unable to eliminate them completely. Researchers believe that the back-and-forth interactions between tumor cells and the immune system during this phase can cause tumors to develop new adaptations to evade the immune system.

Escape

In the escape phase, tumors use powerful adaptations to disrupt equilibrium and suppress the immune system. A common method deployed by tumors is to manipulate checkpoint pathways, which act as natural “brakes” for an immune response. As illustrated below, when checkpoint pathways like CTLA-4 or PD-1 are activated, a signal is triggered that “turns off” active T cells.

escaping cancer

Immune-Targeted Therapies

As researchers better understand the battle between cancer and the immune system, powerful new therapies are emerging. The heart of immunotherapy research is focused on the T cell’s ability to attack and eliminate cancer. Checkpoint inhibitors that target PD-1 and other immune checkpoints are now the backbone of immuno-oncology. Many experts believe the future of cancer therapy will focus on combining checkpoint inhibitors with other therapies that activate the patient’s immune system. Recent studies suggest combination therapies may be able to stop the tumor’s ability to suppress the immune system and improve a patient’s immune response.


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