Medicine: Advances in the War on Cancer

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New research finds promising leads in the genes of tumor cells

What causes nice, healthy, law-abiding cells to go berserk, proliferate wildly and thus produce the phenomenon called cancer? The answer, scientists have long suspected, lies in the genetic material of the cells. Somehow genes, composed of the molecule deoxyribonucleic acid (DNA), have been made abnormal, perhaps by such environmental factors as cigarette smoke and radiation.

In recent months, scientists in three fields have made remarkable progress in documenting how these genetic changes take place. Cell geneticists, studying chromosomes, the discrete units into which genes are packaged, have begun to associate specific abnormalities—an extra chromosome, a missing piece of a chromosome—with specific types of cancer. Virologists have clarified the role that viruses can play in altering DNA. And molecular biologists have used the new tools of genetic engineering to pinpoint precisely which gene, out of the tens of thousands present in every human cell, is responsible for causing a tumor.

Even more exciting is the fact that work in these three disciplines has begun to converge. The mood was electric when 400 scientists gathered last month at the University of Chicago for the Bristol-Myers Symposium on Cancer Research. Researchers reeled off findings that the journals have not been able to keep up with. Said Conference Chairman Janet Rowley, a geneticist at the University of Chicago: "Ten years ago, few of us had any notion the progress would be so rapid, even explosive."

The first breaks in cancer genetics came from the field of virology. Scientists have known since 1908 that a virus could cause malignant tumors in chickens. Over the decades, it was found that viruses could cause tumors in mice, cats, cows and a menagerie of other species. But not until 1980 did anyone identify a virus that causes cancer in human cells: Dr. Robert Gallo of the National Cancer Institute in Bethesda, Md., isolated a virus that can transform normal human white blood cells into the malignant type found in a rare cancer called T-cell leukemia. The same virus was found last year to be responsible for a relatively high rate of both T-cell leukemia and a form of lymphoma (cancer of the lymphatic system) in Japan. Says Gallo: "There is strong evidence that this virus will be important for a number of human cancers."

Researchers are also learning just how a cancer virus can alter normal cell DNA. Some cancer viruses contain cancer-causing genes, or oncogenes. When these genes are isolated and then transferred into healthy cell cultures in the laboratory, they create malignant cells. In the past decade, more than 15 oncogenes have been found in cancer viruses.