Using the Immune System to Fight Cancer

Recently, the prestigious magazine Science published its list of Breakthroughs of the Year 2013. At the very top of this list was cancer immunotherapy.

Cancer immunotherapy is a promising field of research that focuses on using a person’s immune system to fight cancer. How does this work? Normally, a person’s immune system fights off bacterial and viral infections, and deals with any other foreign microbes and substances that shouldn’t be in their body. But somehow the immune system often overlooks cancerous tumors. The idea behind cancer immunotherapy is to stimulate and train a person’s immune system to also attack cancerous tumors.

One area of focus for cancer immunotherapy has been on T cells, and specifically activating them to fight cancerous tumors. T cells, also called T lymphocytes, are important players in the immune system’s response to fighting off a threat.

In the late 1980s, researchers found that there’s a receptor on the surface of T cells that blocks them from functioning. The receptor was called CTLA-4 (for cytotoxic T–lymphocyte antigen 4). Some wondered whether blocking CTLA-4 would uninhibit the T cells, and allow the immune system to fight off cancerous tumors. While in 1996 this approach was shown to be promising in mice (antibodies against CTLA-4 significantly shrank mouse tumors), big companies were hesitant to adopt the novel immunotherapy strategy, and results in patients didn’t come about until 2010. These results were quite promising; patients with metastatic melanoma lived about 60% as long as patients treated with an anti-CTLA-4 antibody.

Similarly, a molecule found in dying T cells has also been of interest for fighting cancer. This molecule is called PD-1 (for programmed death 1). Antibodies made against PD-1 (to block its function in the death of T-cells) were tested in patients with different types of cancer in 2006, and doctors found that tumors in multiple patients significantly shrank. Other promising cancer immunotherapies have also been developed.

That all said, there have been complications associated with these treatments (which can also be very expensive), including inconsistent success rates and potentially dangerous side effects. We clearly still have much to learn about how the therapies actually work to fight cancerous tumors, and how to improve them in general.

But even with the hurdles, cancer immunotherapy is still a very promising avenue for treating cancer, and the story so far helps remind us of the importance of exploring novel solutions to a problem, even if we’ve already adopted standardized approaches to tackle it.

For further reading:

• Jennifer Couzin-Frankel’s article “Cancer Immunotherapy” in Science
• Science’s article “Breakthrough of the Year 2013”
• Teisha J. Rowland’s book Biology Bytes: Digestible Essays on Stem Cells and Modern Medicine