"The work we did was performed with non-lethal but fairly substantial doses of radiation, unlike what a woman would be exposed to during a routine mammogram," says Yaswen, who is also a member of the Bay Area Breast Cancer and the Environment Research Center. "However, the levels of radiation involved in other procedures, such as CT scans or radiotherapy, do start to approach the levels used in our experiments and could represent sources of concern."
For their study, Yaswen and his collaborators worked with human mammary epithelial cells (HMECs), the cells that line breast ducts, where most breast cancers begin. In a culture dish, the vast majority of breast cells display a phenotype that allows them to divide between five and 20 times before becoming senescent. However, also present are rare variant HMECs, which display a phenotype that allows them to continue dividing for many weeks in culture. This vHMEC phenotype arises spontaneously and is much more susceptible to malignancy because it lacks a tumor-suppressing protein called p16.
To test the effects of radiation on cellular environment and subsequent cell behavior, the research team grew sets of HMECs from normal breast tissue in culture dishes for about a week, then exposed each set to a single treatment of a low-to-moderate dose of radiation. They then compared the irradiated sets to sets of breast cells that were not irradiated. Four to six weeks after the radiation treatments, most of the cells in both the irradiated and unirradiated sets had permanently stopped dividing.
"However, the daughters of breast cells exposed to radiation formed larger, more numerous patches of cells w
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory