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Immune System Can Hurt As Well As Help Fight Cancer, Study Shows

Date:
October 1, 2008
Source:
University of Pennsylvania School of Medicine
Summary:
Researchers at the University of Pennsylvania School of Medicine have found that some proteins of the immune system can promote tumor growth. Investigators found that instead of fighting tumors, the protein C5a, which is produced during an immune response to a developing tumor, helps tumors build molecular shields against T-cell attack.
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Model of the C5a molecule, part of the immune complement system.
Credit: John D. Lambris, PhD, University of Pennsylvania School of Medicine

Researchers at the University of Pennsylvania School of Medicine have found that some proteins of the immune system can promote tumor growth. Investigators found that instead of fighting tumors, the protein C5a, which is produced during an immune response to a developing tumor, helps tumors build molecular shields against T-cell attack. These findings appeared online this week in Nature Immunology.

C5a is part of the complement system, one of the body’s immune defenses against pathogens. When activated, the system’s proteins rid the body of microbes and foreign cells. Many cancer treatments are aimed at boosting the immune system to kill tumors.

 “Until now, everyone thought that the complement system was there to eliminate tumor cells. We found that in some conditions, the complement system can promote tumor growth, depending on the specific tumor and the specific environment in which the tumors are developing,” says John Lambris, PhD, the Dr. Ralph and Sallie Weaver Professor of Research Medicine.

However, Penn researchers found that in a mouse model, activation of the complement system in tumor tissue leads to the generation of C5a, which recruits myeloid-derived suppressor cells (MDSC) to tumors. These MDSCs block the function of  CD8+ T cells, which would normally dismantle a tumor.

Researchers also found that blocking the C5a receptor on cell surfaces impairs tumor growth at the same rate of Paclitaxel, a chemotherapy drug. This discovery could lead to new cancer treatments with far fewer side effects than chemotherapy, surmise the investigators.

“Researchers are trying to introduce immune therapies and anti-tumor vaccines, but most of these vaccines fail,” says Lambris. “We show in this study a possible mechanism how to overcome this problem.” Lambris and his team are conducting studies that apply the approaches outlined in this paper to five models of cancer.

In addition to Lambris, Penn co-authors are Maciej M. Markiewski, Robert A. DeAngelis, Salome K Ricklin-Lichtsteiner, Anna Koutoulaki, Fabian Benencia (now at the University of Ohio), and George Coukos, as well as Craig Gerard, Children’s Hospital, Boston. The National Institutes of Health provided funding for this research.


Story Source:

The above story is based on materials provided by University of Pennsylvania School of Medicine. Note: Materials may be edited for content and length.


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University of Pennsylvania School of Medicine. "Immune System Can Hurt As Well As Help Fight Cancer, Study Shows." ScienceDaily. ScienceDaily, 1 October 2008. <www.sciencedaily.com/releases/2008/09/080929153458.htm>.
University of Pennsylvania School of Medicine. (2008, October 1). Immune System Can Hurt As Well As Help Fight Cancer, Study Shows. ScienceDaily. Retrieved May 28, 2015 from www.sciencedaily.com/releases/2008/09/080929153458.htm
University of Pennsylvania School of Medicine. "Immune System Can Hurt As Well As Help Fight Cancer, Study Shows." ScienceDaily. www.sciencedaily.com/releases/2008/09/080929153458.htm (accessed May 28, 2015).

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