Abstract P4-08-03: Mathematical modeling of the unfolded protein response pathway in breast cancer cells

Over 70% of all breast cancers are estrogen receptor positive (ER+) and are treated with endocrine therapies such as aromatase inhibitors or ER-disruptors as part of the standard of care. However, endocrine resistance remains a major clinical challenge for the successful treatment of this disease. ER+ breast cancer cells can escape endocrine therapy-mediated cell death through adaptations in the unfolded protein response (UPR), an evolutionarily conserved cellular stress response pathway that is linked to many other pathways (autophagy, metabolism, anti-oxidant response). To better understand how the UPR pathway promotes endocrine resistance, we built a mathematical model from quantitative measurements of key UPR signaling molecules following treatment of ER+ MCF7 cells (endocrine sensitive, estrogen dependent) with dithiothreitol (DTT). DTT disrupts or prevents protein disulfide bonding and is a potent inducer of the UPR. The same measurements were also made in two MCF7-derived resistant cell lines: LCC1 (sensitive to ER-disruptors, estrogen independent) and LCC9 (resistant to ER-disruptors, estrogen independent). Determining the (minimal) changes to the MCF7 mathematical model needed to adequately capture the data from the resistant cell lines allows us to create specific hypotheses for how the UPR adapts to help produce resistance to endocrine therapies. These hypotheses, in turn, can lead to drug targets for reversing resistance.

Citation Format: Shajahan-Haq AN, Demas DM, Clarke R, Baumann WT. Mathematical modeling of the unfolded protein response pathway in breast cancer cells [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-08-03.

Dynamic Modeling of the Interaction Between Autophagy and Apoptosis in Mammalian Cells

Autophagy is a conserved biological stress response in mammalian cells that is responsible for clearing damaged proteins and organelles from the cytoplasm and recycling their contents via the lysosomal pathway. In cases of mild stress, autophagy acts as a survival mechanism, while in cases of severe stress cells may switch to programmed cell death. Understanding the decision process that moves a cell from autophagy to apoptosis is important since abnormal regulation of autophagy occurs in many diseases, including cancer. To integrate existing knowledge about this decision process into a rigorous, analytical framework, we built a mathematical model of cell fate decisions mediated by autophagy. Our dynamical model is consistent with existing quantitative measurements of autophagy and apoptosis in rat kidney proximal tubular cells responding to cisplatin-induced stress.