Background: Only 14% of African American women with triple-negative breast cancers will be alive at one year. Early detection is greatly needed. Here we aimed to investigate whether activation of biologic pathways that predict aggressive triple-negative breast cancers are also activated in atypia in high-risk African American women. Aggressive cancers are known to consume glucose avidly and produce lactic acid (rather than fully metabolize glucose via the Tricarboxylic Acid (TCA) cycle). This shift toward lactate production, even in the presence of adequate oxygen, is termed the Warburg effect. The Warburg effect is thought to be a late event in breast cancer, however, our studies in high-risk African American women provide evidence that the Warburg effect occurs during cancer initiation. This is an important observation as glucose-signaling can be readily targeted for breast cancer prevention with minimal toxicity. Here we investigated the role of the Warburg effect in breast cancer initiation in young high-risk African American women.
Methods and Results: Similar to fluorodeoxyglucose, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) is a fluorescent glucose analog that can be used to track glucose uptake and glycolysis. 2-NBDG spectroscopy provides a means to track glucose metabolism in live mammary epithelial cells from high-risk women. We used 2-NBDG spectroscopy to measure glucose uptake in ER-breast cancer and live atypical mammary epithelial cells from high-risk premenopausal women. We observe that both triple-negative breast cancer and a subset of atypia exhibits accumulation of 2-NBDG.
There is growing recognition that phosphoprotein signaling networks (rather than single genes) play a key role in breast cancer initiation and progression. Our team used Reverse Phase Proteomic Microarray (RPPM) profiling to test for activation of phosphoprotein signaling networks in atypical RPFNA cytology from high-risk premenopausal women in our cohort. RPFNA were obtained from two independent sets of 39 and 38 high-risk premenopausal women; 45% of these women were African American. The signaling network most highly expressed in precancerous cells contained activated signaling proteins associated with the Warburg effect (AKT/mTOR/PI3K), insulin signaling (pACC, IRS1) and epithelial to mesenchymal transition (EMT) IL6/Stat3/vimentin.
Conclusions: This is the first evidence that abnormal glucose uptake and the Warburg effect occurs during breast cancer initiation in high-risk African American premenopausal women. These studies demonstrate our ability to identify abnormal glucose and activated signaling networks associated with the Warburg effect in atypical mammary cells from high-risk African American women and provide an important target for breast cancer early detection and prevention.
Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):PR2.