Exposures to environmental agents can affect breast development and alter breast cancer risk. New tests are needed to provide a better, non-invasive assessment of exposure of girls and women to these chemicals. We plan to use mouse mammary tissue to develop improved models that respond to critical doses of these environmental agents and then figure out molecules that change as a result of the exposure of this breast tissue. One category of molecules that might change is the sugars that modify proteins made by the breast tissue. Such sugar modifications are seen in breast cancer, and therefore their appearance in response to these chemicals could be the first harbinger of changes leading to breast cancer. To do so we will use a state-of-the-art technology, called mass spectrometry, to measure these modified sugars. To address this challenge, we have assembled a multidisciplinary team of creative leaders in mouse and human breast biology and cancer and systems biology and regulatory toxicologists at California Environmental Protection Agency. The investigators are experts in the technologies involved. This team will focus on the perturbation of breast development by environmental chemical stressors in both mouse and human tissues in culture and in vivo.

Research question(s) or central hypotheses:
We hypothesize that environmental agents that increase the risk of breast cancer risk alter the sugar modifications of proteins made by mammary cells. We will use mouse and human breast tissues in threedimensional (3D) culture systems that model the development of the normal mammary gland. To assess the risk from these environmental chemicals we will treat these tissues and look for abnormal development, and then look for the production of proteins that have altered their sugar modification. Identification of such molecules could lead to specific tests in the future.

General methodology:
We will use the mouse mammary organoid assay, which undergoes branching like real breast in a tissue culture model, to analyze potential various environmental agents. These agents may perturb whether breast cells divide, branch or make milk proteins differentiation and may start the breast cells on the way to cancer. Our approach looks at the exposure-related changes in sugars that modify breast proteins by a special separation procedure called mass spectrometry. In looking for changed molecules that could tell us about exposure, called biomarkers, we hope to develop an assay for assessing exposure in girls and women. Many biomarkers with clinical utility in cancer already rely on modified sugars, making us confident that we will be able to find such new biomarkers.

Innovative elements:
The innovation in this proposal comes first from the idea from exposing mouse and human breast tissue that is undergoing normal development in culture to environmental chemicals, and then looking for changes molecules that may be the harbinger of increased susceptibility to cancer. Secondly, based on the fact that cancers have markedly changes sugars modifying the breast proteins, we propose to look for new biomarkers that have altered sugars as a way of detecting early changes induced by environmental agents.

Advocacy involvement and relevance to the human issues associated with breast cancer:
Breast cancer is the second leading cause of cancer deaths in women and is the most common cancer among women. This study addresses an important aspect of women's health that of how the breast develops and changes with increasing age and how environmental stressors change the breast tissue and make the breast vulnerable to breast cancer. If we could prevent these changes induced by environmental agents, we would greatly improve breast cancer outcome and save the lives of millions of women. Developing biomarkers of exposure, may lead to new regulations on safe levels of such chemicals on one hand and promote the discovery of therapies to reverse these effects, on the other hand. Overall this should lead to a reduction in the rates of breast cancer.

We have involved advocates in all aspects of the research from discussing the importance of determining whether girls and women are exposed to environmental toxins, to which toxins to study first, to disseminating our work. To disseminate our findings to the community on a regular basis and receive feedback, we will partner with the Zero Breast Cancer advocacy group for the development of the project and provide outreach and publicize the results. These investigators will work synergistically to push forward on the strategic goals.