New Concerns about Radiation and Breast Cancer
Mary Helen Barcellos-Hoff, Ph.D. and Paul Yaswen, Ph.D.
Lawrence Berkeley National Laboratory
U01ES012801
New research findings suggest that ionizing radiation exposure not only produces mutations that lead to cancer, but changes the microenvironment of cells so that future cells are more likely to become cancerous. This work was performed using cultures of human breast cells and was supported in-part by NIEHS.
Researchers used non-lethal but substantial doses of radiation much higher than what a woman would be exposed to during a mammogram. However, the radiation levels used in CT scans or radiotherapy approach the doses used in these experiments.
Human mammary epithelial cells were used in the experiments. These cells line breast ducts where most breast tumors originate. They typically divide 5-20 times in culture; however, a variant phenotype of cells capable of dividing for many weeks spontaneously arises. Typically the variant phenotype lacks a tumor-suppressor protein called p16 and is much more susceptible to malignancy.
The experiments consisted of growing cell cultures from normal breast tissue for about one week. Then some of the cells were irradiated with a single low-to-moderate dose. Four to six weeks later, most of cells in both the irradiated and non-irradiated culture dishes had stopped dividing. However, the daughters of the irradiated cells formed larger and more numerous patches of cells with the variant phenotype.
The researchers conclude that the radiation exposure promoted the growth of pre-cancerous cells by making the environment that surrounds the cells more hospitable to their continued growth.
Citation: Mukhopadhyay R, Costes SV, Bazarov AV, Hines WC, Barcellos-Hoff MH, Yaswen P. Promotion of variant human mammary epithelial cell outgrowth by ionizing radiation: an agent-based model supported by in vitro studies. Breast Cancer Res. 2010, 12(1):R11. Epub 2010 Feb 10.
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