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New cancer markers may allow early diagnosis

New genetic and protein markers in blood and tissue may allow much earlier diagnisis of cancer (U.S. National Cancer Institute)

Scientists are beginning to recognise genetic and protein markers in blood and tissue that point to the onset of cancer, allowing even earlier diagnosis and the saving of countless lives.

The markers, found in the blood and tissue of patients whose spreading cancer killed them, should serve as early tests for the spread - or metastasis - of cancer, U.S. researchers told a meeting of the American Association of Cancer Research in Washington. If caught early enough, cancer is highly curable.

"People don't die because they got cancer. People die because they got cancer and we didn't detect it at a point where we could do something about it," Dr Andrew von Eschenbach, head of the U.S. National Cancer Institute, told a news conference. Metastasis is responsible for 90% of cancer deaths.

Dr Joan Massague of the Memorial Sloan-Kettering Cancer Centre in New York and colleagues have been making a painstaking search for the products used by cancer cells to spread.

The tumour cells must first travel around the body, find the bone, brain or other tissue they will invade and then literally break in. Each process will require different genes and proteins.

The research team started with tissue samples taken from a patient who died of breast cancer, but Massague said they were making similar findings in samples from other breast cancer patients as well as those with prostate cancer and melanoma.

First, they inoculated them into specially bred mice - a standard first step in cancer research. The mice develop tumours made up of human cells, which can be studied.

They noted which genes were overactive in those tumours and then did a reverse test - genetically engineering normal cells with those genes and seeing if they metastasized in mice. Using this method, they identified 48 genes and their protein products that seem to help tumour cells spread, Massague said.

Some of them are 'secretory products': proteins sent out by the cells, which can be measured in the blood. One is MMP-1 (matrix metalloproteinase 1), an enzyme frequently targeted by cancer researchers. It is used by cells to break open the collagen bonds that hold other cells together.

"We are finding in serum samples of patients with metastatic breast cancer that they have high levels of MMP-1," Massague said.

Another is interleukin-11, which is active in osteoclasts - the cells that break down bone. "The tumour cell growing as it metastasizes in bone needs to eliminate the bone matrix in order to have room to grow," Massague said.
