Abstract PS19-13: Palmitate exacerbates breast tumorigenesis in vitro via induction of a senescent-like phenotype in fibroblasts

Background: Obesity is associated with a worse breast cancer prognosis, conferring an increased risk of recurrence and mortality. At the same time, recent evidence suggests that obesity is also correlated with development of cellular senescence, an inflammatory state associated with exacerbation of breast tumorigenesis in preclinical models. As obese individuals present greater levels of inflammation at baseline, research efforts are warranted to examine the means by which obesity promotes the development of a senescent phenotype, which may further exacerbate inflammation. Additionally, studies have yet to determine whether obesity-induced senescence modulates the tumorigenic process in the context of breast cancer specifically. Methods: To this end, we exposed fibroblasts to the obesity-associated circulating factor palmitate and used qPCR and western immunoblotting to assess the expression of genes and proteins involved in the senescent state, including interleukin (IL)-1a, IL-6, IL-8, senescence-associated beta-galactosidase (SA-beta-gal), and matrixmetalloproteinase (MMP)-9. As a mechanistic investigation, we next assessed the impact of palmitate on activation of NF-kB signaling using western immunoblotting, immunofluorescence, and NF-kB luciferase reporter assays. Finally, we utilized cell counting, MTT, wound healing, and colony formation assays to examine the impact of these palmitate-exposed fibroblasts on breast cancer cell proliferation, viability, motility, and survival, respectively. Results: We found that palmitate induced fibroblast gene expression of IL-1a, IL-6, and IL-8, major components of the senescent secretome, as well as expression of the senescent markers SA-beta-gal and MMP-9. The mechanism at least partially involved activation of NF-kB, responsible for production of about 75% of senescent secretome components. More importantly, these palmitate-exposed fibroblasts were of pathological impact, exacerbating in vitro measures of breast cancer cell aggressiveness. Conclusions: These findings contribute to our understanding of the impact of obesity-associated factors on breast tumorigenesis, demonstrating a mechanistic link between palmitate and the pro-tumorigenic effects of senescent cells. Our studies will ultimately aid in the identification of a therapeutic target that can be used to improve the comparably worse outcomes of the obese breast cancer patient. Citation Format: Brittany Susanne Harlow, Albert Davalos, Andrew Brenner, Christopher Jolly, Stefano Tiziani, Steve Hursting, Linda deGraffenried. Palmitate exacerbates breast tumorigenesis in vitro via induction of a senescent-like phenotype in fibroblasts [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS19-13.