Hormonal regulation of immune modulators in human breast tissue

Breast cancer is the most common form of cancer and the second leading cause of malignancy-associated death in women worldwide. Estrogens are the main sex hormones in women. They are essential for the development and function of normal breast mammary glands; however, prolonged exposure to estrogens increases the risk of breast cancer development and progression. Approximately two-thirds of all breast cancer patients are positive for estrogen receptor (ER), but only 50% of those cases can benefit from antiestrogen therapy. In this thesis we investigated the effects of estrogen, diet modification, and anti-estrogen drugs on several immune modulators in normal human breast tissue. We used the microdialysis technique to sample the immune modulators in situ in normal human breast tissue, in malignant breast tissue, and in tumor tissue from both the immune competent mice with murine breast cancer and immune deficient mice bearing human breast tumors. Furthermore, we also used ex vivo culture of normal breast tissue and in vitro cell culture of breast cancer cell lines. A combined cell culture (co-culture) of breast cancer cell lines, together with the primary mature adipocytes, was also used in this thesis. In Paper I and Paper II, our results suggested that estrogen exerted both proinflammatory and pro-tumorigenic effects in normal human breast tissue. Estradiol increased extracellular interleukin-1β (IL-1β) and leptin levels and decreased IL-1Ra and adiponectin levels in normal human breast tissue. In contrast, tamoxifen decreased IL-1β and leptin levels and increased IL-1Ra and adiponectin levels, shifting the environment towards an antiinflammatory and antitumorigenic state. Diet modification with flaxseed for 30 days also increased IL-1Ra levels, creating an anti-inflammatory environment in normal breast tissue. In the breast cancer tissue, we found that extracellular IL-1β levels and leptin levels were significantly higher, whereas adiponectin levels were significantly lower, compared with normal adjacent breast tissue, which suggested a more proinflammatory state. In the third paper, our in vivo investigation of normal breast tissue revealed significant correlations between vascular endothelial growth factor (VEGF) and leptin, IL-1β and leptin, and between VEGF and IL-1β. No correlations were found in the abdominal subcutaneous (s.c.) fat tissue. Our in vitro inhibition experiments suggested that VEGF was a potent regulator of leptin, but that leptin was not a potent regulator of VEGF. Co-culture per se altered the release of VEGF and leptin and enhanced the effects of estradiol, compared with monocultures of the included cell types. In conclusion, the results presented in this thesis will increase the overall understanding of the role of estrogens in breast cancer, which may be useful in future treatment studies