A defective gene linked to a rare eye cancer has also been linked to breast cancer and a common form of lung cancer, researchers say.

The gene was the first of a newly discoveredgroup of anti-cancer genes that normally protect against cancer but allow cancer to appear when defective, said Ray White of the Howard Hughes Medical Institute at the University of Utah in Salt Lake City.Similar anti-cancer genes now have also been linked to colon cancer, another common and lethal form of cancer.

The findings that the gene is linked to breast cancer and so-called small-cell lung cancer suggest that it and other anti-cancer genes could play a major role in many types of human cancer, White told genetics students at the Jackson Laboratory in Bar Harbor on Monday.

Identifying those genes and determining how they go wrong does not mean cancer will then be eliminated, White said. But the understanding of these genetic abnormalities is crucial to ultimately being able to wipe out cancer, he said.

Over the shorter term, he said, understanding the genetics of cancer might allow doctors to diagnose subtypes of common cancers and learn to treat them better.

The gene was identified in children with a rare eye cancer known as retinoblastoma. White and Webster Cavenee at the Ludwig Institute for Cancer Research in Montreal were among the scientists who made that initial discovery and learned how the gene worked.

Later, those retinoblastoma children were found to develop osteosarcoma, a bone cancer, also as a result of defects in the retinoblastoma gene.

More recently, researchers at the University of California, San Francisco, led by Wen-Hwa Lee and Eva Lee, have found that the gene is defective in certain breast cancer cells grown in the laboratory.

About the same time, Frederic Kaye and colleagues at the National Cancer Institute-Navy Medical Oncology Branch reported seeing retinoblastoma gene defects in small-cell lung cancer cells in the laboratory.

"It may well be that the majority of small-cell lung cancers involve a lesion in the retinoblastoma gene as well as several others," said White.

Retinoblastoma affects perhaps 1,000 Americans annually, but small-cell lung cancer strikes 30,000 people in the United States every year, and breast cancer strikes 130,000.

Suddenly, a gene that was important only in a rare disease is now seen to be significant in two of the most important and most devastating human cancers.

Meanwhile, White had identified a similar anti-cancer gene in a rare form of inherited colon cancer.

He said Monday he has now shown that this anti-cancer gene plays a role in the much more common non-inherited form of colon cancer that is another one of the country's leading cancer killers.

Bert Vogelstein of the Johns Hopkins University School of Medicine in Baltimore also has identified several other genetic defects associated with colon cancer.

He estimated that perhaps as many as seven genetic defects must occur for colon cancer to develop. He said he and White have now identified five of those defects.

"You can look at these genetic alterations as the causes of cancer - just as you can look at bacteria as the causes of infection," Vogelstein said in a telephone interview. "Except it's more complicated in cancer."