Abstract 3332: Obesity drives epithelial/mesenchymal transition and tumor progression in a novel Wnt-1 mammary cancer model

Abstract

Abstract Epidemiological evidence suggests a potential role of obesity in regulating clinical subtype, differentiation status, and prognosis of breast cancer. Specifically, an elevated waist-hip ratio is associated with increased risk and progression of basal-like breast cancer, an aggressive form characterized by heterogeneous tumors typically enriched in a putative breast cancer stem cell (BCSC) population. Therefore, we hypothesized that obesity regulates a plastic population of multipotent malignant cells. To test this hypothesis, we generated and characterized two distinct murine mammary tumor cell lines derived from MMTV-Wnt-1 transgenic mice. M-Wnt cells displayed a mesenchymal morphology while E-Wnt cells had an epithelial morphology. M-Wnt cells harbored a large CD44+/CD24- putative cancer stem cell population (62% +7.8), had significant mammosphere forming capacity (>30% of cells form mammospheres, p<0.0001), and increased ALDH activity (7% are ALDH+, p=0.0004). M-Wnt cells have increased migration (scratch assay) and invasion in vitro (226-fold higher after 30h, p<0.0001). As few as 50 unsorted M-Wnt cells, injected into C57BL/6 mice were capable of forming a tumor. Microarray analysis revealed that M-Wnt cells display gene expression profiles virtually identical to human Claudin-low breast tumors, while E-Wnt cells clustered with basal-like tumors. EMT and stem cell gene expression patterns of M-Wnt cells were maintained in vivo, including decreased E-cadherin and increased N-cadherin, fibronectin, vimentin, SNAIL, TWIST, SLUG, FOXC2, and TGF-β (p<0.05 for all). Using these cell lines in vivo, we tested the hypothesis that energy balance modulation, through diet-induced obesity (DIO) and calorie restriction (CR), regulates the BCSC population. We found that M-Wnt tumors, transplanted into ovariecomized syngeneic female C57BL/6 mice, grew at significantly different growth rates depending on the diet treatment (DIO > Control, p=0.011; CR < Control, p=0.012), while E-Wnt tumors were only affected by CR (CR < Control p=0.001; no difference between DIO and Control tumors). DIO enhanced M-Wnt tumor progression, adipocyte infiltration, and central necrosis and drove EMT (decreased E-Cadherin and increased fibronectin and N-Cadherin expression) through modulation of key BCSC associated genes, including increased TGF-β, SNAIL, FOXC2, and Oct4 (p<0.05 for all). In conclusion, we found that the mesenchymal M-Wnt cell line is highly responsive to changes in dietary energy balance status relative to the E-Wnt differentiated epithelial cell line, suggesting that energy balance modulation (ie, CR and obesity) regulates tumor growth through direct regulation of a BCSC population, possibly in response to alterations in TGF-β signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3332. doi:10.1158/1538-7445.AM2011-3332