LA JOLLABy carefully controlling the levels of two proteins, researchers at the Salk Institute have discovered how to keep mammary stem cellsthose that can form breast tissuealive and functioning in the lab. The new ability to propagate mammary stem cells is allowing them to study both breast development and the formation of breast cancers.
"What we've shown is that we can take these cells out of a mouse and study them and regulate them in the laboratory by providing them with a specific factor," says Peter C. Gray, a staff scientist in Salk's Clayton Foundation Laboratories for Peptide Biology, who collaborated on the new work with Benjamin T. Spike, a senior research associate in the laboratory of Salk Professor Geoffrey M. Wahl.
The results of the study were published in the April 8th issue of the journal Stem Cell Reports.
Mammary stem cells can give rise to new breast cells during fetal development, adolescence or lactation and may also play a role in breast cancer, so they represent a highly promising avenue for breast cancer research. But isolating the stem cells and maintaining them in the lab to study has been difficult.
"There was a lot of prior work demonstrating that mammary-specific stem cells exist, but it was virtually impossible to isolate them in numbers from an adult," says Spike. "But we previously found we could turn to early development, when the stem cells are present in higher proportions."
When the researchers used fetal breast tissue rather than adult tissue from mice, they were able to pinpoint which cells were stem cells but the cells would rapidly change when grown in a dish. A defining property of all stem cells is that when they divide into two new cells, they can form both stem cells and differentiated cells (cells on their way to becoming a specific type of tissue).
Spike and Gray grew the mammary stem cells in culture dishes a
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