Background: Increasing evidence suggests the unique susceptibility of estrogen receptor and progesterone receptor negative (ERPR-) breast cancer to dietary fat amount and type. Dietary n-3 polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), may modulate breast adipose fatty acid profiles and downstream bioactive metabolites to counteract pro-inflammatory, pro-carcinogenic signaling in the mammary microenvironment. Objective: To determine effects of ~1 to 5 g/d EPA+DHA over 12 months on breast adipose fatty acid and oxylipin profiles in women with ERPR(-) breast cancer, a high-risk molecular subtype. Methods: We conducted a 12-month randomized controlled, double-blind clinical trial of ~5g/d vs ~1g/d DHA+EPA supplementation in women within 5 years of completing standard therapy for ERPR(-) breast cancer Stages 0-III. Blood and breast adipose tissue specimens were collected every 3 months for biomarker analyses including fatty acids by gas chromatography, oxylipins by LC-MS/MS, and DNA methylation by reduced-representation bisulfite sequencing (RRBS). Results: A total of 51 participants completed the 12-month intervention. Study treatments were generally well-tolerated. While both doses increased n-3 PUFAs from baseline in breast adipose, erythrocytes, and plasma, the 5g/d supplement was more potent (n =51, p <0.001). The 5g/d dose also reduced plasma triglycerides from baseline (p =0.008). Breast adipose oxylipins at 0, 6, and 12 months showed dose-dependent increases in unesterified and esterified DHA and EPA metabolites (n =28). Distinct DNA methylation patterns in adipose tissue after 12 months were identified, with effects unique to the 5g/d dose group (n =17). Conclusions: Over the course of 1 year, EPA+DHA dose-dependently increased concentrations of these fatty acids and their derivative oxylipin metabolites, producing differential DNA methylation profiles of gene promoters involved in metabolism-related pathways critical to ERPR(-) breast cancer development and progression. These data provide evidence of both metabolic and epigenetic effects of n-3 PUFAs in breast adipose tissue, elucidating novel mechanisms of action for high-dose EPA+DHA-mediated prevention of ERPR(-) breast cancer. Clinicaltrials.gov identifier NCT02295059  

The authors have declared no competing interest.

NCT02295059

This study was funded by: R01 CA164019 USDA Project 2032-51530-025-00D

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Institutional Review Boards of The Ohio State University (OSU) and City of Hope (COH) gave ethical approval for this work

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes