Monday, March 29, 2010

EU Scientists Discover How Some Cancer Tumors Elude Immune System

EU-funded scientists have discovered that tumors can elude the immune system's radar by imitating lymph nodes' characteristics. The breakthrough gives the research world new insight into the role of the lymphatic system, and may even lead to new cancer treatments. Results from the project are published online in the journal Science. EU support for the work came from the European Research Council (ERC), which is financed under the Ideas Programme of the Seventh Framework Programme (FP7).

In the introduction to their published paper, the authors explain that cancer's progression, metastasis, and resistance to therapy is largely a result of the way a tumor interacts with its host immune cells. Immune cells can recognize tumors, but many tumors are able to manipulate these cells to bypass immune surveillance.

The study undertaken by the team from Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland has demonstrated that tumors are able to escape attack by creating a tolerant microenvironment and by mimicking key features of lymph nodes. 'The tumor tricks the body into thinking it is healthy tissue,' explained Professor Melody Swartz, head of the Laboratory of Lymphatic and Cancer Bioengineering (LLCB) at the EPFL.

The EPFL team's objective was to understand how tumors induce immune tolerance, allowing the tumor to develop and spread. They studied mouse models of melanoma (a type of skin cancer) to focus on a particular protein called CCL21 (chemokine (C-C motif) ligand 21) that is usually found in healthy lymph nodes. This protein attracts T (thymus) cells and programs them to carry out important immune functions.

The researchers found that some tumors are able to secrete this protein to create lymphoid-like tissue at the external layer of the tumor. T cells are then led to believe that the tumor is not an enemy that should be eradicated, which allows the tumor to remain undetected by the immune system.

They write, 'We suggest that by altering the tumor microenvironment, CCL21-secreting tumors shift the host immune response from immunogenic to tolerogenic, thereby facilitating tumor progression.'

EPFL's Dr Jacqueline Shields said, 'The finding that tumors can attract naïve and regulatory T cells, and educate them, has important implications for tumor immunotherapy.'

Given the fact that a tumor will only advance if it eludes the immune system's defenses from the outset, the research has uncovered one way in which tumor progress can potentially be prevented. This represents a significant step forward for the development of cancer therapies. The findings have also opened up potential new research into the relationship between lymphatic systems and cancer research.

For more information, please visit:
Science: http://www.sciencemag.org/
Ecole Polytechnique Fédérale de Lausanne (EPFL): http://www.epfl.ch/index.fr.html
European Research Council:  http://erc.europa.eu/

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