Scientists
discover how cancer spreads

Scientists have discovered how cancer--particularly a deadly form of the disease like breast cancer--spreads from a primary site to other places in the body. Their findings could open doors for new ways of treating and preventing advanced disease.

Instead of a cell just breaking off from a tumor and traveling through the bloodstream to another organ where it forms a secondary tumor--a process called metastasis--researchers in the United States have shown that the cancer sends out envoys to prepare the new site. Intercepting those envoys or blocking their action with drugs might help to prevent the spread of cancer, or help to treat it in patients in which it has already occurred.

"We are basically looking at all the earlier steps that are involved in metastasis that we weren't previously aware of. It is complex, but we are opening the door to all these things that occur before the tumor cell implants itself," said professor David Lyden of Cornell University. "It is a map to where the metastasis will occur."

Cancer's ability to colonize other organs is what makes the disease so deadly. Once the cancer has spread beyond its original site it is much more difficult to treat.

In research reported in the journal Nature, Lyden and his colleagues describe what happens before the arrival of the cancerous cells at the new site. "The authors show that tumor cells can mobilize normal bone marrow cells, causing them to migrate to particular regions and change the local environment so as to attract and support a developing metastasis," Patricia Steeg of the National Cancer Institute in Bethesda, Md., said in a commentary.

Cells at the site of the metastasis multiply and produce a protein called fibronectin, which acts like a glue to attract and trap the bone marrow cells to create a landing pad or nest for the cancer cells. "These nests provide attachment factors for the tumor cells to implant and nurture them. It causes them not only to bind but to proliferate. Once that all takes place, we have a fully formed metastatic site or secondary tumor," said Lyden.

Without the landing pad, the cancerous cell could not colonize the organ.

In animal and laboratory studies, the scientists looked at how breast, lung, and esophageal cancer spread. The envoys from the tumor determine the site of the secondary site. Lyden said measuring the number of special bone marrow cells circulating in the body could help to determine whether a cancer is likely to spread.

"This opens up the door to new concepts of how metastasis is taking place. If we can understand all these multiple processes, we can develop new drugs that block each step. That way we have a much better future than just trying to treat the tumor cell, which is almost like a last step in this process." (Reuters)