|Program and Abstracts
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Mammary Adipose Derived Stem Cells In BRCA-Related Breast Cancers
Irene J. Pien, BS1, Jared A. Blau, BS, MEd1, Michelle L. Bowie, MS2, Siya Lem, BS2, Victoria L. Seewaldt, MD2, Scott T. Hollenbeck, MD3.
1Duke University School of Medicine, Durham, NC, USA, 2Duke University Department of Medicine, Division of Medical Oncology, Durham, NC, USA, 3Duke University Department of Surgery, Division of Plastic, Maxillofacial, and Oral Surgery, Durham, NC, USA.
Purpose: Breast cancer-associated adipocytes undergo delipidation and loss of terminal differentiation to revert to more stem-cell phenotype and function, giving evidence that adipogenesis differentiation pathways are important in cancer biology. These adipose stem cells (ASCs) are further implicated in their secretion of harmful, pro-inflammatory cytokines to contribute negatively to the local tumor microenvironment. Biologically aggressive breast cancers are dependent on the local stromal milieu to create a favorable field for tumor growth and invasion, particularly in inherited breast cancer syndromes (BRCA1/BRCA2).
Methods: Mammary ASCs (mASCs) isolated from the breast(s) of high-risk breast cancer patients undergoing therapeutic or prophylactic mastectomy procedures were matched for age, body mass index, and BRCA status (total n=24). Stem cell status was confirmed using flow cytometric evaluation of surface marker expression and trilineage differentiation potential. Adipogenic potential was evaluated by quantifying final triglyceride content after two weeks of induction. Screening of the mASC secretome was performed using a cytokine ELISA-based array.
Results: Flow cytometric assessment of surface marker expression of mASCs demonstrated the following mean (SEM) percentage positive cells for the indicated surface antigens: CD44, 80.6 (5.3); CD90, 79.7 (4.6); and CD105, 26.7 (6.3). mASCs expressed the following mean (SEM) percentage negative cells for the indicated surface antigens: CD14, 96.4 (0.5); CD31, 97.6 (0.1); and CD45, 98.2 (0.1). There were no statistically significant differences in marker expression between mASC groups that underwent successful trilineage induction (n=8) and those that failed one differentiation pathway (n=6). mASCs from BRCA negative vs. BRCA mutation patients produced lesser quantities of triglycerides after two weeks of induction; average fold-change of lipid production in non-inherited cancer mASCs was 3.45±1.96 vs. 0.79±0.89 (p=0.03) (FIGURE 1). The mASC secretome of non-BRCA carriers vs. BRCA mutations differed in production of interleukin (IL) 1b (0.09 vs. 4.45-fold, p=0.03), IL10 (1.00 vs. 4.24-fold, p=0.04), and tumor necrosis factor (TNF) alpha (0.24 vs. 0.88-fold, p=0.02).
Conclusions: This is the first study to demonstrate an intrinsic, abnormal adipogenic differentiation block in mASCs from high-risk breast cancer patients (BRCA1/BRCA2), a process that has been implicated in breast tumor progression and invasiveness. Aggressive epithelial breast cancers are dependent on the local stromal environment that creates a favorable field for tumor growth and invasion, including a chronic pro-inflammatory cytokine profile, making the understanding of the stromal factors critically important for future risk stratification and/or prevention targets and strategies.
FIGURE 1. Triglyceride production of mASCs. Data are expressed as fold-change in triglyceride production, day 14 vs. day 0 of adipogenic induction. *Student’s t-test (vs. no inherited cancer),
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