Attack on cancer cells.

Attack on cancer cells 

Interferon is being tested as an agent to fight cancers (SN: 7/27/85, p. 58) as well as viruses. Results reported by Gilbert Jay and his colleagues at the National Cancer Institute in Bethesda, Md., indicate how this natural chemical may help fight malignancies and suggest new means of bolstering the immune system's attack.

Jay has been investigating the cancer-related role of the "classical transplantation antigens," those cell-surface proteins responsible for rejection of transplanted organs. He suggests cancer cells may evade the host immune system by omitting one group of these proteins, called class I antigens, from cell surfaces. Interferon's role, then, in fighting cancer may be to stimulate cancer cells to reveal their class I antigens, thereby making them better targets for immune attack.

Jay used recombinant DNA techniques to insert extra copies of the gene for a class I antigen into malignant (transformed) cells that do not normally show high levels of the surface proteins. The cells were no longer able to cause tumors. Treatment with interferon can also make malignant cells produce class I antigens. In animal experiments, the scientists injected malignant cells that normally cause tumors, then injected interferon. Jay says, "There was complete protection against this tumor."

Another approach to the problem is to enhance the immune system's sensitivity to the scarce class I antigens that may be present on malignant cells. "The low level may be sufficient if the animal's immune system is angry enough," Jay says. He immunized animals with a dose of malignant cells treated with interferon (or given extra genes of a class I antigen). He also injected the animals with malignant cells of the same type but which had not undergone antigen-producing treatment. Instead of developing fast-growing tumors, the animals remained healthy. The immunization was successfully given a week before, on the same day or two days after injection of the malignant cells. Jay speculates that it may be possible to immunize patients against their own tumor cells.