Growth inhibitory efficacy of natural products in a model for triple negative molecular subtype of clinical breast cancer

Global gene expression profiling identifies predictive and prognostic biomarkers and rationalizes breast cancer subtype-targeted treatment. The Anthracyclin/Taxol and survival pathway specific small molecular inhibitors, constitute current treatment options. These options are associated with acquired tumor resistance and emergence of drug-resistant cancer stem cells. Dietary supplements and constitutive bioactive phytochemicals with relatively low systemic toxicity may provide testable alternatives for current therapy. Human breast epithelial cell lines 184-B5 (non-tumorigenic triple negative cell type) and MDA-MB-231 (breast carcinoma derived triple negative cell type) were used as the experimental models. Putative cancer chemo-preventive natural products and their constitutive bioactive agents represented the test agents. Anchorage independent growth, cell cycle progression and cell apoptosis quantified the treatment efficacy. Compared to the 184-B5 cells, the MDA-MB-231 cells exhibited anchorage-independent growth indicative of persistent cancer risk. Additionally, the MDA-MB-231 cells exhibited hyper-proliferation, accelerated cell cycle progression and inhibited apoptosis indicative of loss of homeostatic growth control. The test agents inhibited anchorage-independent growth via cytostatic and pro-apoptotic effects. The triple negative carcinoma-derived Doxorubicin-resistant phenotype exhibited cancer stem cell markers, including tumor spheroid formation and expression of CD44, NANOG and c-Myc. These data identify clinically relevant mechanistic leads for the efficacy of natural products in the aggressive therapy-resistant breast cancer subtype and suggests a testable approach for cancer stem cell-targeted therapy.