Tumor-Related Protein May Fight Cancer
In research that could lead to human clinical studies next year, researchers have shown that transferring tumor-related proteins from one species to another may trigger a strong immune-system attack against cancer.
Researchers at Memorial Sloan-Kettering Cancer Center in New York have found that injecting a protein found on the surface of human melanoma cancer cells into a cancer-ridden mouse will cause the rodent’s immune system to attack and kill the mouse’s own cancers.
Next year, said Dr. Alan N. Houghton, chief of clinical immunology at Sloan-Kettering, researchers hope to receive federal approval to try the experimental therapy on human melanoma patients.
“We will reverse what we have done in the laboratory,” he said. “We would put mouse cells into humans.”
Houghton said that both mice and humans can develop melanoma, a type of cancer originating in pigment-producing cells, usually in the skin. Melanoma cells have on their surface an antigen, called gp75, which is similar to antigens on the surface of normal pigment cells. For this reason, the body’s immune system may fail to attack and control the tumor cells.
But the researcher said that when the gp75 from humans is injected into mice, the rodent’s immune system is awakened to the presence of the cancer and mounts a powerful attack.
In their research, reported in last week’s issue of the Proceedings of the National Academy of Sciences, Houghton and his team injected 10 mice with mouse melanoma cells, causing them to develop the cancers. They then injected five of the mice with human gp75.
Later, the researchers analyzed the lungs of the animals. Tumors were widespread in those that received no human gp75. But tumors were reduced by 95% in the mice injected with human gp75.
Even insect cells could be used to awaken the immune system attack against the cancer, Houghton said.
Cultured insect cells were genetically altered so that they produced gp75 and the protein was then injected into cancer-laden mice.
“We saw a marked decrease in lung tumors among these mice,” Houghton said. “The decrease was about two-thirds below that of the controls [cancer-ridden mice without the insect cells].”
The technique actually causes the rodent immune system to attack all pigment-producing cells, he said. For this reason, some of the black mice in the experiment developed white patches of hair. The pigment in animals’ eyes, however, was not affected.
After injections of the human gp75 were stopped, the white hair turned black again, but the tumors did not return, he said.
Houghton said a similar phenomenon occurs in humans. Patients treated for melanoma sometimes develop patches of pigment-free, white skin, a condition called vitiligo.
“This is usually associated with a good outcome,” he said.
Dr. Herman N. Eisen, a National Academy of Sciences member who reviewed the study, said the research “is an interesting and important set of observations. It demands a very vigorous extension.”
Though the study centered on melanoma, Houghton said modified versions of the technique could possibly be effective against breast, prostate and colon cancer.
