In preliminary experiments, we find remarkably different DNA damage signaling kinetics in breast cancer stem cell cultures relative to breast cancer cells. The most striking difference is in the relative timing of the initiation of the ubiquitylation cascade and the phosphorylation cascade, suggesting that these two events are differentially regulated in these two states of the same cell line. We wish to define the differences between mammosphere and 2D cultures that are responsible for the differences in the signaling cascade and then manipulate these pathways to determine their contribution to resistance towards DNA damaging agents. Since inhibitors of key signaling proteins are in clinical development or, in the case of ubiquitin signaling, have drugs currently available for clinical use, these results could identify opportunities to alter treatments to improve the success of DNA damage therapies by identifying targets for selectively sensitizing this resistant and invasive breast cancer cell subpopulation.
