Abstract P2-05-22: Pre-clinical findings on obesity reversal and breast cancer progression: Targeting persistent inflammation
Authors: Rossi EL , Bowers LW , Khatib SA , Doerstling SS , Hursting SD 
Published: May 2016

Background

Obesity is an established risk and progression factor for several intrinsic subtypes of breast cancer, including basal-like breast cancer (BLBC). Increased local and systemic levels of pro-inflammatory mediators, which typically accompany obesity, can independently influence tumor growth. Currently, it is unclear whether weight loss can reverse the enhancing effects of obesity on breast tumorigenesis. We hypothesize that chronic obesity results in epigenetic reprogramming, which may mediate residual inflammation, and lead to persistent mammary tumor growth despite moderate weight loss.

Methods

Female C57BL/6 mice (n=51) were administered a control (10% kcal from fat) or diet-induced obesity (DIO; 60% kcal from fat) regimen. After 17 weeks, DIO mice either continued on DIO diet or were switched to control diet to stimulate gradual weight loss, subsequently designated as Formerly Obese (FOb). Mice were orthotopically injected with Wnt-1 mammary tumor cells (a model of BLBC) at week 25, and monitored for an additional 9 weeks, then killed and their tumors excised, measured and stored for subsequent analysis. In an ongoing tumor study, we will randomize mice to the control or DIO regimen, switching half the DIO mice to the control diet after 15 weeks, resulting in normal weight, obese, and FOb mice. Within each of these groups, the mice will be further randomized to +/- supplementation with Sulindac, a non-steroidal anti-inflammatory drug (NSAID), starting at the time of the diet switch. After 10 weeks of +/- Sulindac supplementation, mice will receive orthotopic injections of a mesenchymal derivative of an MMTV-Wnt-1 transgenic tumor, the M-Wnt cell line, and will continue on diet and treatment until euthanization.

Results

In our initial study, body weight, adiposity, and serum levels of leptin and insulin were similar in FOb and control mice, but serum levels of IL-6 were similar in FOb and DIO mice, and significantly higher than controls. Moreover, tumor burden, the mammary gland expression of key inflammatory genes, and the prevalence of hypermethylated inflammation-related genes in DNA from mammary tissue were comparable in DIO and FOb mice and significantly higher than in control mice, and there was high concordance with DNA methylation profiles in breast DNA from obese versus normoweight women participating in the UNC Normal Breast Study.

Conclusions

Our preclinical findings suggest that modest weight loss may not be sufficient to reverse the effects of chronic obesity on epigenetic reprogramming and inflammatory signals that are associated with obesity-related mammary tumor progression. Moreover, we have identified several genes with concordant obesity-related hypermethylation in humans and mice; which were unchanged in FOb mice. Thus combining weight loss regimens with epigenetic or inflammatory modulators may be an effective strategy for breaking the obesity-breast cancer link. We are currently assessing whether combining moderate weight loss with anti-inflammatory interventions (Sulindac or omega-3 fatty acids), or reprograming metabolism with a bariatric surgical intervention, is more effective than moderate weight loss alone at offsetting the persistent enhancing effects of chronic obesity on BLBC.

Citation Format: Rossi EL, Bowers LW, Khatib SA, Doerstling SS, Hursting SD. Pre-clinical findings on obesity reversal and breast cancer progression: Targeting persistent inflammation. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-05-22.