U.S. researchers are testing exercise\'s impact on breast cancer survivors at the molecular level. Drs. Rong Li, Sagar Ghosh and Nicolas Musi at the Institute for Health Promotion Research in the School of Medicine at the University of Texas Health Science Center at San Antonio say they will test how different types of exercise impact participants\' levels of adipose stromal cells. Adipose stromal cells in blood have been increasingly recognized as an important source for a variety of cancer-promoting factors, including estrogens and cytokines. However, other biomarkers scheduled to be studied include tumor necrosis factor, Interleukin 6 (IL-6), adiponectin, C-reactive protein and salivary cortisol -- a known biomarker of stress, the researchers say. During the one-year study, 90 breast cancer survivors, on a random basis, will participate in exercise at least three times a week. There will be three exercise categories: a comprehensive exercise \"prescription\" featuring individualized aerobics, strength-training and flexibility; a yoga exercise program; or general exercise chosen at will. \"We expect comprehensive and yoga-focused participants to have better fitness outcomes, less stress and improved biological indicators of future risk of secondary cancers,\" Dr. Daniel Hughes, a study co-principal investigator, says in a statement. Participants in all three groups will take a fitness test and undergo measurements at the start and end of the study.