Immunotherapy: Looking through cancer's invisibility cloak

The human body is bombarded daily with infectious agents and other toxins resulting in potentially cancer-causing damage to DNA.

Normally, these attacks do not lead to chronic diseases such as cancer or viral infections but usually cause an acute, self-limited disease that is resolved within a matter of days. However, chronic viral infection or cancer occurs when these assaults overwhelm the ability of the immune system to eliminate unhealthy cells.

One goal of research in treating cancer is to develop methods to harness and enhance the body's natural tendency to defend itself against malignant tumors.

Immunotherapy is the new method in using the body’s natural defense system to fight off cancer.

To understand the basis of cancer immunotherapy, it first helps to know how the immune system hunts and kills more typical prey such as viruses, bacteria and parasites.

Among the system’s complex network of cells, proteins and activity pathways, two biological warriors — T cells and antibodies — deserve special mention.

Both of these play a critical role in helping the body kill abnormal cells found in tumors and block tumor growth.

Immune Cell Warriors

T cells are white blood cells that can recognize and bind to foreign or abnormal cells. The interaction between the T-cell and its target is highly specific, much like a key fits a lock. Upon recognition of an unfamiliar or abnormal cell — like those that are cancerous or infected with a virus — the T cells trigger an immune response that blasts away the abnormal cells.

Small numbers of specific types of T cells recognize and eliminate virally infected or cancerous cells. In immunotherapy, these very small numbers of T cells that find and fight tumor cells are removed from the patient and duplicated until they number in the billions, the amount necessary to combat the overwhelming cancer in the patient.

The expanded population of tumor fighting cells is then infused back into the patient, where they seek out and destroy tumor cells.

"By creating 'armies' of T-cells that are augmented to find and kill cancer cells, we are aiming to develop a new generation of cancer treatments that can have better results and far fewer side effects for patients than current chemotherapy drugs or radiation treatments," said Dr. Cassian Yee, a researcher at the Fred Hutchinson Cancer Research Center.

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