"Cancer Genes"

They can turn cells malignant

A crucial yet mysterious step in the development of cancer appears to be alterations, possibly by chemicals, to the DNA (deoxyribonucleic acid) carried in the thousands of genes in the body's cells. Scientists have theorized that though many genes may be affected, relatively few, dubbed "cancer genes," have the power to transform a cell from a healthy to a cancerous state. Evidence to support this theory came to light last week with word that researchers, using new genetic-engineering techniques, have isolated several genes from human tumor cells and found that at least two were capable of making normal cells malignant.

The work, reported by the Long Island, N.Y., newspaper Newsday, has not yet appeared in a scientific journal. At the Massachusetts Institute of Technology, a team headed by Molecular Biologist Robert Weinberg isolated a gene from a bladder tumor, and parts of genes from leukemia and colon tumors. Molecular Biologist Michael Wigler, working with a team at the Cold Spring Harbor Laboratory on Long Island, isolated a second bladder-tumor gene and identified a gene common to cancerous lung and colon cells. A group led by Molecular Biologist Geoffrey Cooper of Harvard's Sidney Farber Cancer Institute isolated a chicken leukemia gene. The researchers discovered that both bladder genes, when inserted into normal mouse cells being grown in laboratory dishes, transform some of the cells. It is not yet known if the other genes that have been isolated can do the same.

The findings may help scientists understand the process by which normal cells are converted into cancerous ones. Says Weinberg: "Isolation should make it possible to analyze genes down to the details of their structure and to see exactly what kind of mutation or alteration in the DNA induced the normal cell to behave differently." Scientists still do not know whether more than one gene in a cell must be altered for the cell to become malignant. Nor do they know which proteins are made at the genes' commands. Proteins regulate the activities of the cell. When instructions for their production go awry, so do the cell's workings. Once the cancer genes' proteins are identified, says Weinberg, "we can begin to ask how their presence in a cell is able to perturb or subvert normal cellular metabolism."

Eventually, doctors may be able to fashion a screening test for cancer based on the concentration of these proteins in patients' blood. Such an assay might also help monitor therapy. "Isolating these genes," says Weinberg, "could make dozens of things possible."

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