Obesity is an established risk factor for hormone receptor (HR)-positive breast cancer in post-menopausal women. This increased risk is thought to be partly attributable to increased estrogen production from adipose tissue, since adipose tissue is the primary site of action of the estrogen-synthesizing enzyme aromatase post climacteric. Given the current epidemic of obesity, there is a pressing need to develop mechanism-based strategies to reduce the cancer risk among this sector of the population. Estrogen deprivation is a commonly used approach for breast cancer prevention and treatment, but both SERMs and aromatase inhibitors have significant side effects that restrict their widespread use for prophylaxis. We hypothesize that by targeting the pathways that drive increased aromatase expression it will be possible to suppress estrogen overproduction in adipose tissues, including the breast, and hence reduce the risk of HR-positive breast cancer in the overweight and obese. Importantly in this respect, a key role has been established for cyclooxygenase (COX)-derived prostaglandin E2 (PGE2) in stimulating transcription of the CYP19 gene which encodes the aromatase enzyme. We have reported that COX-2 overexpression in the mammary gland (MG) leads to increased PGE2 production and elevated aromatase expression. Strikingly, we have now found that significant inflammation, elevated COX-2 expression and increased aromatase levels occur in both the MG and visceral fat (VF) in mouse models of obesity. These exciting findings raise the very real possibility that obesity-related inflammatory changes in both the MG and VF contribute to elevated aromatase activity and thereby an increased risk of HR- positive breast cancer. Therefore, the goal of this proposal is to evaluate strategies for disrupting arachidonic acid metabolism and thereby suppressing the PGE2->aromatase axis, with the ultimate goal of normalizing the increased levels of aromatase associated with obesity. In SA1, we will define the interrelationships between PGE2, BRCA1, histone acetylation and aromatase induction, based on our novel data implicating BRCA1, Sirt-1 and CBP/p300 in PGE2-mediated aromatase induction. In SA2, we will evaluate whether COX- 1, mPGES-1 or 15-PGDH, enzymes involved in the synthesis or catabolism of PGE2, are determinants of aromatase expression and activity in the MG and VF using knockout mouse strains. In SA3, we will explore the mechanism(s) by which n-3 fatty acids modulate the PGE2->aromatase pathway, since n-3 fatty acids have been shown to suppress PGE2 synthesis and protect against experimental breast cancer. Finally, in SA4 we will test whether n-3 fatty acids, alone or combined with a COX-2 inhibitor, suppress inflammation and reduce aromatase levels in vivo in the MG and VF of obese mice. If either a pharmacological or dietary approach disrupts the obesity->inflammation->COX->aromatase pathway, this would represent a significant advance and strengthen the rationale for addressing similar questions in women. Collectively, the results of the proposed studies will offer new insights into strategies to reduce the risk of HR-positive breast cancer.
We have shown that obesity drives an inflammatory process in adipose tissue leading to increased expression of the estrogen synthesizing enzyme aromatase. Here we propose to test if either a pharmacological or dietary approach, or the combination thereof, disrupts the obesity->inflammation-> cyclooxygenase->aromatase pathway. Positive findings in this study would provide a platform for evaluating new strategies for reducing hormone receptor-positive breast cancer.
| Iyengar, Neil M; Zhou, Xi Kathy; Gucalp, Ayca et al. (2016) Systemic Correlates of White Adipose Tissue Inflammation in Early-Stage Breast Cancer. Clin Cancer Res 22:2283-9 |
| Haka, Abigail S; Barbosa-Lorenzi, Valéria C; Lee, Hyuek Jong et al. (2016) Exocytosis of macrophage lysosomes leads to digestion of apoptotic adipocytes and foam cell formation. J Lipid Res 57:980-92 |
| Gucalp, Ayca; Iyengar, Neil M; Hudis, Clifford A et al. (2016) Targeting obesity-related adipose tissue dysfunction to prevent cancer development and progression. Semin Oncol 43:154-160 |
| O'Sullivan, Timothy E; Rapp, Moritz; Fan, Xiying et al. (2016) Adipose-Resident Group 1 Innate Lymphoid Cells Promote Obesity-Associated Insulin Resistance. Immunity 45:428-41 |
| Seo, Bo Ri; Bhardwaj, Priya; Choi, Siyoung et al. (2015) Obesity-dependent changes in interstitial ECM mechanics promote breast tumorigenesis. Sci Transl Med 7:301ra130 |
| Iyengar, Neil M; Hudis, Clifford A; Dannenberg, Andrew J (2015) Obesity and cancer: local and systemic mechanisms. Annu Rev Med 66:297-309 |
| Esper, Raymond M; Dame, Michael; McClintock, Shannon et al. (2015) Leptin and Adiponectin Modulate the Self-renewal of Normal Human Breast Epithelial Stem Cells. Cancer Prev Res (Phila) 8:1174-83 |
| Bhardwaj, Priya; Du, Baoheng; Zhou, Xi Kathy et al. (2015) Estrogen Protects against Obesity-Induced Mammary Gland Inflammation in Mice. Cancer Prev Res (Phila) 8:751-9 |
| Iyengar, Neil M; Morris, Patrick G; Zhou, Xi Kathy et al. (2015) Menopause is a determinant of breast adipose inflammation. Cancer Prev Res (Phila) 8:349-58 |
| Bhardwaj, Priya; Du, Baoheng; Zhou, Xi Kathy et al. (2013) Caloric restriction reverses obesity-induced mammary gland inflammation in mice. Cancer Prev Res (Phila) 6:282-9 |
Showing the most recent 10 out of 20 publications
