2006年VOA标准英语-Australian Stem Cell Discovery Could Help（在线收听）

By Claudia Blume
Hong Kong
05 January 2006

Scientists in Australia have discovered a stem cell that is expected to provide clues about how breast cancer develops, and how cancer cells evade current therapies. The discovery could be a breakthrough in the treatment of breast cancer.

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Researchers at the Victorian Breast Cancer Consortium in the Australian city of Melbourne say they have discovered the stem cell that controls the formation of breast tissue.

Stem cells are the basic building blocks of all body parts, from muscles to blood vessels to nerves.

The Australians isolated these newly identified stem cells from the breasts of female mice.

Under normal circumstances, this type of stem cell produces healthy breast tissue. But a genetic predisposition to cancer, or exposure to carcinogens (cancer-causing agents), can cause a particular cell to grow into a cancerous tumor.

The existence of these "rogue" stem cells could explain why some women begin developing breast tumors again following chemotherapy - a development that has puzzled scientists and doctors for many years.

Chemotherapy is most effective at destroying cancer cells that divide rapidly. But the newly found stem cell divides slowly: it can survive for months or even years after chemotherapy, and then break out into a new cancer.

The leader of the Australian research team, Jane Visvader, says the main goal of her team is to understand how these stem cells work, and then find a drug that will stop them from becoming malignant.

"The main goal is to understand the nature of both the normal stem cells and the stem cells that become aberrant and accumulate errors and therefore, use this information to try and design drugs to target these cells," she said.

Ms. Visvader says it could take 10 to 20 years to develop such a drug. In the next step of the research, tumor samples from human breast cancer patients will be analyzed to confirm the findings of the mouse model.

Ms. Visvader says the research team was also able to grow fully functional breasts in mice from the stem cells. But she says that growing new breasts in human patients to replace breasts removed because of cancer is only a remote possibility.

"And that is because mice and [human] breast tissue differ quite significantly in their make-up," she explained. "The hormones and growth factors that are likely to be involved in regenerating the breast will also be involved in the tumor-genic process that is leading cells to become cancerous."

In other words, the same factors that might cause a new breast to grow might also cause a new cancer.

The findings of the Australian researchers, published in the scientific journal Nature this week, have been corroborated by a Canadian research team.