Abstract P2-06-03: Obesity is associated with DNA damage in the breast epithelium of BRCA1 and BRCA2 mutation carriers: A role for estrogens & strategies for prevention
Bibliographic record
Abstract
Abstract Background: Elevated bodyweight is a risk factor for breast cancer development in women who carry a mutation in the DNA repair enzymes BRCA1 and BRCA2. However, the mechanistic basis for this association is unknown. Breast adipose tissue undergoes significant changes in the setting of weight gain and obesity, including elevation in aromatase expression which leads to the increased biosynthesis of estrogens. Given that estrogens and estrogen metabolites have known pro-proliferative and genotoxic effects, we hypothesized that in BRCA1/2 mutation carriers, obesity may be positively associated with breast epithelial cell DNA damage, thereby increasing the risk of tumorigenesis. Furthermore, we examined the impact of inhibiting estrogen signaling or production on breast epithelium DNA damage in BRCA1/2 mutation carriers. Methods: Tissue microarrays were generated from non-cancerous breast tissue derived from 72 women carrying a mutation in BRCA1 or BRCA2 with known body mass index (BMI, kg/m2). Breast epithelium DNA damage was quantified by immunofluorescence (IF) staining of the DNA damage marker γH2AX. RNA-Seq was performed on breast organoids to assess differences in gene expression in relation to BMI. Associations between DNA damage and biomarkers of estrogen biosynthesis and bioavailability, including aromatase expression in the breast and circulating steroid hormone binding globulin (SHBG), were also evaluated. To explore the effect of blocking estrogen signaling or production on DNA damage, non-tumorous breast tissue explants from BRCA1/2 mutation carriers were cultured with fulvestrant, an estrogen receptor degrader, or metformin, an anti-diabetic drug that also reduces aromatase expression in the breast. Breast epithelial cell DNA damage was measured in control vs treated explants by γH2AX IF staining after 24 hours of treatment. Results: BMI was positively correlated with DNA damage in the breast epithelium of BRCA1/2 mutation carriers. Upstream analysis of gene expression in organoids derived from women with a BMI ≥ 30 compared to <25, revealed activation of estrogen signaling. Further supporting a contribution of locally-derived and circulating estrogens to obesity-related DNA damage, breast aromatase expression was found to be positively correlated with DNA damage while circulating SHBG levels showed a negative correlation. Targeting estrogen signaling with fulvestrant significantly reduced breast epithelium DNA damage in breast explants from women carrying a mutation in either BRCA1 or BRCA2. Interestingly, metformin, also caused a significant reduction in DNA damage in breast explants. Conclusion: These data provide mechanistic evidence for the link between obesity and breast cancer in BRCA1 and BRCA2 mutation carriers through identification of a positive association between BMI and breast epithelial cell DNA damage. Importantly, these studies demonstrate that fulvestrant and metformin, drugs already approved for clinical use, decrease breast epithelial cell DNA damage. Further studies are warranted to determine whether targeting estrogens or use of metformin may be effective risk reduction strategies in BRCA1/2 mutation carriers with excess bodyweight who are at high risk for breast cancer development and currently have limited options for prevention beyond surgical intervention. Support: NIH R01CA215797, NIH F31CA236306, Anne Moore Breast Cancer Research Fund Citation Format: Priya Bhardwaj, Neil M. Iyengar, Sofya Oshchepkova, Phoebe Piloco, Rohan Bareja, Olivier Elemento, Dilip D. Giri, Michael Pollak, Monica Morrow, Jason A. Spector, Kristy A. Brown. Obesity is associated with DNA damage in the breast epithelium of BRCA1 and BRCA2 mutation carriers: A role for estrogens & strategies for prevention [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-06-03.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".