Obesity and Breast Cancer: Current Insights on the Role of Fatty Acids and Lipid Metabolism in Promoting Breast Cancer Growth and Progression

Obesity and excess accumulation of adipose tissue are known risk factors for several types of cancer, including breast cancer. With the incidence of obesity constantly rising worldwide, understanding the molecular details of the interaction between adipose tissue and breast tumors, the most common tumors in women, becomes an urgent task. In terms of lipid metabolism, most of the studies conducted so far focused on upregulated de novo lipid synthesis in cancer cells. More recently, the use of extracellular lipids as source of energy came into focus. Especially in obesity, associated dysfunctional adipose tissue releases increased amounts of fatty acids, but also dietary lipids can be involved in promoting tumor growth and progression. In addition, it was shown that breast cancer cells and adipocytes, which are a major component of the stroma of breast tumors, are able to directly interact with each other. Breast cancer cells and adjacent adipocytes exchange molecules such as growth factors, chemokines, and interleukins in a reciprocal manner. Moreover, it was shown that breast cancer cells can access and utilize fatty acids produced by neighboring adipocytes. Thus adipocytes, and especially hypertrophic adipocytes, can act as providers of lipids, which can be used as a source of energy for fatty acid oxidation and as building blocks for tumor cell growth

Quantification of diacylglycerol and triacylglycerol species in human fecal samples by flow injection Fourier transform mass spectrometry

The intestinal microbiome plays an important role in human health and disease and fecal materials reflect the microbial activity. Thus, analysis of fecal metabolites provides insight in metabolic interactions between gut microbiota and host organism. In this work, we applied flow injection analysis coupled to Fourier transform mass spectrometry (FIA-FTMS) to identify and quantify lipid species in human fecal samples. Fecal homogenates were subjected to lipid extraction and analyzed by FIA-FTMS. The analysis of different subjects revealed a vast heterogeneity of lipid species abundance. The majority of samples displayed prominent signals of triacylglycerol (TG) and diacylglycerol (DG) species that could be verified by MS2 spectra. Therefore, we focused on the quantification of TG and DG. Method validation included limit of quantification, linearity, evaluation of matrix effects, recovery, and reproducibility. The validation experiments demonstrated the suitability of the method, with exception for approximately 10% of samples, where we observed coefficients of variation higher than 15%. Impaired reproducibility was related to sample inhomogeneity and could not be improved by additional sample preparation steps. Additionally, these experiments demonstrated that compared with aqueous samples, samples containing isopropanol showed higher amounts of DG, presumably due to lysis of bacteria and increased TG lipolysis. These effects were sample-specific and substantiate the high heterogeneity of fecal materials as well as the need for further evaluation of pre-analytic conditions. In summary, FIA-FTMS offers a fast and accurate tool to quantify DG and TG species and is suitable to provide insight into the fecal lipidome and its role in health and disease

Single cell study of adipose tissue mediated lipid droplet formation and biochemical alterations in breast cancer cells

Obesity is a known risk factor for breast cancer and a negative prognostic factor for cancer recurrence and survival. Several studies demonstrated that aggressive breast tumor cells contain higher numbers of intracellular lipid droplets (LDs). Here we applied simultaneous visualization, identification and quantification of the lipid accumulation in lipid droplets (LDs) of aggressive, human triple-negative MDA-MB-231 breast cancer cells treated with adipose tissue-conditioned medium (ACM) derived from overweight and obese patients. In addition to Oil Red O and AdipoRed fluorescent staining, label-free confocal Raman microspectroscopy (CRM) has been applied. CRM enables imaging of cell compartments as well as quantification and monitoring of specific biomolecules and metabolic processes on a single cell level. Interestingly, breast cancer cells incubated with ACM showed a significantly higher number of intracellular LDs. Cultivation of breast tumor cells with ACM of obese patients induced the formation of LDs with a 20-fold higher lipid concentration than cultivation with basal medium. This is in line with the significantly higher levels of NEFAs (non-esterified fatty acids) detected in the ACM obtained from obese patient compared to ACM obtained from overweight patients or basal medium. Further, by principal component analysis, we identified a significant increase in unsaturation, esterification and lipid to protein ratio in LDs in breast cancer cells incubated with ACM. CRM analyses might function as a valuable diagnostic tool to identify metabolic alterations in biological samples which in turn could provide more detailed insights in the pathogenesis of breast cancer in association with obesity

Secreted Factors from Adipose Tissue Reprogram Tumor Lipid Metabolism and Induce Motility by Modulating PPARα/ANGPTL4 and FAK

Recent studies indicate that adipose tissue in obesity promotes breast cancer progression by secreting protumorigenic chemokines, growth factors, and fatty acids. However, the detailed mechanisms by which hypertrophic adipose tissue influences breast cancer cells are still not well understood. Here we show that co-culture with adipose tissue from high-fat diet induced obese C57BL/6 mice alters transcriptome profiles in triple-negative breast cancer (TNBC) cells, leading to upregulation of genes involved in inflammation and lipid metabolism, such as IL1B, PLIN2, and ANGPTL4. Similar results were obtained by treating TNBC cells with adipose tissue conditioned media (ACM) generated from fat tissue of obese female patients. Many of the upregulated genes were activated by PPAR nuclear receptors, as shown by pathway analyses and gene expression experiments using PPAR agonists and antagonists. Metabolic analysis revealed that TNBC cells cultivated with ACM had significantly higher levels of beta-oxidation. Furthermore, ACM-treated TNBC cells displayed a pronounced aggressive cell phenotype, with enhanced wound healing, proliferation, and invasion capabilities. ACM-induced invasion was dependent on the PPAR-target ANGPTL4 and activated FAK signaling, as shown by ANGPTL4 depletion and FAK inhibition. Together, our data suggest that factors released by adipose tissue change PPAR-regulated gene expression and lipid metabolism and induce a more aggressive TNBC cell phenotype. These effects are, at least in parts, mediated by fatty acids provided by the adipose tissue