Cancer migration factor discovered.

Cancer migration factor discovered

With most cancers, it is not the initial growth of tumor cells but rather their ability to travel to other tissues that makes them life-threatening. Now, researchers from the National Cancer Institute (NCI) in Bethesda, Md., and several other government institutions report they have found a substance secreted by tumor cells that enables them to move about. While the work doesn't offer an immediate cancer intervention, it does suggest several new approaches to detection and treatment.

NCI's Lance A. Liotta and his co-workers isolated the substance, a protein they call autocrine motility factor (AMF), from human melanoma (skin cancer) cells that had migrated to brain tissue. When added back to a melanoma cell line in the lab, AMF stimulated the cells to squeeze through small pores in a filter. Its activity, they have found, is independent of growth factors that promote cell division.

"One of the least understood aspects of how tumor cells invade is what makes them move,' says Liotta. "We have for the first time a handle on what causes this.'

Tumor cells have been shown to secrete growth factors, while normal cells make motility factors, observes Bruce Zetter of Harvard University, who studies new blood vessel formation in tumors and in diseased hearts. "It's an interesting corollary that tumor cells can stimulate themselves to migrate,' he says. It makes them less dependent on substances produced by the body, he notes. "They have within them all the components they need to divide and metastasize [spread].'

If the finding is confirmed, AMF may prove to be clinically useful. If it also spreads to the blood, this protein could enable physicians to detect the presence or spread of cancer by a blood test. And blood levels, Liotta says, may suggest just how metastatic the cancer is. In addition, he told SCIENCE NEWS, "If we could figure out an inhibitor we might be able to prevent the transition from a [localized] cancer to a metastatic one.'

Liotta suggests that AMF works by changing the chemical composition of a molecule on cell membranes; this change may increase cell motility by making the membrane more fluid. He and his co-workers describe the isolation and purification of AMF in the May PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (Vol. 83, No. 10). Cells also move in wound healing and embryo development, and at recent scientific meetings, several European groups have discussed isolation of motility factors in those processes that may be similar to AMF, Liotta says.