Cancer cells have a ticket to ride
Spreading cancer cells have learned a thing or two from their nemesis, the immune system. Just like the immune system’s white blood cells, or leukocytes, cancer cells rely on the process known as leukocyte trafficking to migrate through the body, according to a report in the Feb. 28 Nature by cancer researchers at Schering-Plough/DNAX Research Institute in Palo Alto, Calif.
For a stable, sedentary cell to change into one that can pick up and leave requires several structural changes. For example, the cell’s internal skeleton of protein fibers must transform to enable amoebalike motion, so the cell can creep along tissues. Traveling cancer cells also require a means to home in on and adhere to particular tissues.
Both white blood cells and metastasizing cancer cells seem to require the help of proteins called chemokines, say the researchers. On their membranes, white blood cells have chemokine receptors that serve as on-board homing devices, enabling the cells to follow chemical signals coming from tissues that need their help. The researchers suspected that chemokine receptors were permitting cancer cells to listen in on messages intended for the immune cells.
Sure enough, specific chemokines are present in lungs, liver, bone marrow, lymph nodes, and the other organs that cancer cells tend to invade. To confirm that chemokines attract cancer cells, the researchers used antibodies to neutralize chemokines in mice harboring tumors. The cancer didn’t spread in these mice as it did in those with functioning chemokines. Pharmaceutical scientists are now searching intensely for chemokine blockers that may be useful in cancer treatment, say the authors.