Key driver of metastasis identified

In a recent issue of Cancer Research, a journal of the American Association for Cancer Research, lead researcher David Waisman, Ph.D., professor in the Departments of Biochemistry and Molecular Biology and Pathology, and Canada Research Chair in Cancer Research at Dalhousie University, detailed the key role the macrophage cell surface protein S100A10 plays in allowing macrophages to move to the site of tumor growth – a process that is essential to tumor development.

Waisman said the findings are an example of the complicated biology of cancer.

“We used to think that the only cells that mattered in a tumor were the cancer cells, and that's it, but now we are beginning to see that other cells must collaborate with cancer cells to drive tumor growth and permit an evolution of the cancer cells into metastatic cells. This change is what causes poor prognosis and ultimately what kills the patient,” he said.

Waisman and colleagues discovered that tumors will not grow without macrophage assistance. These macrophages must come from the blood or from other locations in the tissues. How they are able to move through the tissues or from the blood supply into the tumor had always been a mystery.

These macrophages need to chew their way through the tissue that forms a barrier around the growing tumor in order to move into the tumor site and combine with the cancer cells. The researchers found on the outside surface of the macrophage is a protein called S100A10, which enables the macrophage to remove the tissue barriers retarding migration to the tumor site.

Theoretically, blocking either the macrophages or S100A10 chemically could slow, or even stop, tumor growth.

“We found that the protein, S100A10, acts like a pair of scissors on the outside of the macrophages that empowers the macrophages with the ability to chew their way through tissues and enter the tumor site where they release substances that stimulate cancer cell growth and metastatic evolution,” said Waisman.

He said the next step is to figure out exactly how S100A10 functions as a molecular scissor and also to identify pharmaceutical agents that can block the action of S100A10, thereby preventing the movement of macrophages to the tumor site. By understanding exactly how S100A10 works at the molecular level, it may even be possible to design agents which block its activity.

The study was funded by a grant from the Canadian Cancer Society Research Institute and the Canadian Institutes of Health Research.

Follow the AACR on Twitter: @aacr #aacr

Follow the AACR on Facebook: http://www.facebook.com/aacr.org

The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, the AACR is the world's oldest and largest professional organization dedicated to advancing cancer research. The membership includes 33,000 laboratory, translational and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and more than 90 other countries. The AACR marshals the full spectrum of expertise from the cancer community to accelerate progress in the prevention, diagnosis and treatment of cancer through high-quality scientific and educational programs. It funds innovative, meritorious research grants, research fellowships and career development awards to young investigators, and it also funds cutting-edge research projects conducted by senior researchers.

The AACR has numerous fruitful collaborations with organizations and foundations in the U.S. and abroad, and functions as the Scientific Partner of Stand Up To Cancer, a charitable initiative that supports groundbreaking research aimed at getting new cancer treatments to patients in an accelerated time frame. The AACR Annual Meeting attracts more than 17,000 participants who share the latest discoveries and developments in the field. Special Conferences throughout the year present novel data across a wide variety of topics in cancer research, treatment and patient care, and Educational Workshops are held for the training of young cancer investigators. The AACR publishes seven major peer-reviewed journals: Cancer Discovery; Cancer Research; Clinical Cancer Research; Cancer Epidemiology, Biomarkers & Prevention; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Prevention Research. In 2010, AACR journals received 20 percent of the total number of citations given to oncology journals. The AACR also publishes Cancer Today, a magazine for cancer patients, survivors and their caregivers, which provides practical knowledge and new hope for cancer survivors.

A major goal of the AACR is to educate the general public and policymakers about the value of cancer research in improving public health, the vital importance of increases in sustained funding for cancer research and biomedical science, and the need for national policies that foster innovation and the acceleration of progress against the 200 diseases we call cancer.