Immune cell may spread cancer

DENVER, April 24 (UPI) -- An immune cell thought to fight breast cancer may actually promote its spread, U.S. researchers say.

The mice studies linked the spread of breast cancer to the lungs to production of an inflammatory protein -- called RANK ligand -- by immune system cells known as lymphocytes.

Wei Tan and Michael Karin of the University of California, San Diego, say their findings establish RANK ligand as a potential marker to help determine breast cancer prognosis.

"Without lymphocytes, there is no metastasis," Tan said in a statement.

The researchers developed two types of mice that developed breast tumors. The first group had lymphocytes in the tumors and expressed RANK ligand while the second group did not. The cancer spread to the lungs in the first group but did not in the second group.

When the RANK ligand was injected into mice that lacked lymphocytes, the potential for the cancer to spread was restored -- indicating the RANK ligand making lymphocytes were critically important to the process. Furthermore, blocking the cascade of cellular signals that follow the docking of the RANK ligand to its receptor on tumor cells halted cancer spreading and may offer a treatment strategy.

The findings were presented at the annual meeting of the American Association for Cancer Research in Denver.