Advanced age and obesity separately and interactively potentiate triple negative breast cancer progression

Advanced age and obesity are major risk factors for breast cancer (BC) mortality that are independently associated with aggressive disease and therapeutic resistance. Despite this, preclinical models of BC mainly utilize young lean mice. The mechanisms underlying age- and obesity-related BC progression are currently unknown, highlighting a critical gap in our understanding of BC biology. To address this gap, we generated aged (16 mos) and young (6 mos) cohorts of lean and obese mice by placement on either low-fat control (10% kcal from fat) or diet-induced obesity (DIO; 60% kcal from fat) diet, respectively, beginning at 8-weeks of age. This resulted in four experimental groups: aged lean, aged DIO, young lean, young DIO. Mice were orthotopically injected with one of two triple negative BC cell lines (E0771 or Met-MWNTLung), which represent aggressive BC subtypes associated with poor prognosis in humans. Outcomes included primary tumor weight and lung metastasis quantification. Biochemical and molecular analyses included serum cytokines and gene expression within tumor and adjacent normal mammary tissue. Our TNBC models indicate tumor growth is similarly increased in young DIO and aged lean mice, with both significantly higher than young lean mice. Moreover, the combination of advanced age and obesity in aged DIO mice significantly increased tumor growth relative to all other experimental groups. Preliminary pathology analyses in Met-MWNTLung-bearing mice reveal that advanced age enhances lung metastasis beyond that of young mice regardless of diet. Increased tumor burden in both the aged lean and young DIO mice is accompanied by increased serum proinflammatory cytokines (IL-1b, CXCL13, CCL11, among others). Consistent with these findings, Gene Set Enrichment Analysis (GSEA) of Met-MWNTLungtumor and adjacent normal mammary microarray data demonstrated enrichment of inflammatory pathways, including IFNγ response, IFNα response, IL-2/STAT5 signaling, and IL-6/JAK/STAT3 signaling in aged lean and young DIO mice relative to young lean mice. Interestingly, tumor-adjacent mammary from aged lean and young DIO mice was also enriched for markers of EMT, consistent with age- and DIO-associated phenotypic switching of cells within the tumor-adjacent microenvironment. Taken together, our findings reveal that obesity and advanced age augment BC progression and promote inflammation within the local (mammary & tumor) and systemic (serum) microenvironments. Ongoing analyses are investigating the role of cellular senescence, a stress-induced cell cycle arrest in which cells acquire a proinflammatory secretome. Knowledge gained from this study will help to elucidate the mechanisms underlying advanced age- and obesity-related BC progression, which is urgently needed to develop new strategies for reducing adverse TNBC outcomes associated with advanced age and obesity in human populations. Citation Format: Laura A. Smith, Magdalena A. Rainey, Nishita T. Sheth, Stephanie A. Montgomery, Stephen D. Hursting. Advanced age and obesity separately and interactively potentiate triple negative breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2843.