Regulation of cell death (apoptosis and autophagy) is critical for proper development and homeostasis of multicellular organisms. One of the hallmarks of cancer is the evasion of programmed cell death that would normally suppress tumor growth and invasiveness. Apoptosis is generally triggered by DNA damage or signaling though death receptors and is the mechanism of action of almost all non-targeted chemotherapeutics and radiation therapy. Autophagy is triggered in response to metabolic stress and is thought to play a role in tumor dormancy and survival. While our understanding of cell death at the molecular level has dramatically increased over the past 50 years, our ability to clinically visualize this process during treatment has lagged behind. The ability to rapidly and non-invasively measure both forms of cell death during treatment can be used to rationally optimize the choice of chemotherapy and to maximize therapeutic response, effectively stratifying patients for personalized medicine. Cell death imaging can also reveal non-tumor effects, allowing the prediction and avoidance of side-effects prior to clinical presentation. Finally, identifying the ratio of apoptosis to autophagy provides the means to assess the efficacy of emerging pro-autophagy therapies and identify dormant tumors that may respond to targeted therapies. Here we propose to design a suite of molecular probes to image two forms of cell death in mouse models of ovarian cancer. We will employ an activity-based strategy to generate a PET/CT probe for caspase activity (apoptosis) and both PET/CT and MRI probes for Atg4 activity (autophagy). We will rigorously validate our probes in cell-based fluorescent assays across multiple lines and characterize their cell permeability, specificity, and metabolic stabilit prior to PET probe development. We will employ our PET/CT probes to measure the onset, duration, and extent of the tumor cell apoptosis in response to chemotherapeutics in mouse models of ovarian cancer. The information that we obtain in these experiments will be correlated to standard imaging protocols (MRI, FDG-PET) to determine the relationships between cell death, disease site, and tumor volume. In conjunction with our studies of apoptotic cell death, we will design and validate a PET/CT and prototype MRI imaging agent for autophagic cell death. We will validate our initial fluorescent probe in a cell-based model system using controlled induction of ARHI, a tumor suppressor known to strongly promote autophagy in ovarian tumors. We will translate this into PET/CT probe to visualize autophagy in mouse models of ovarian cancer where autophagy is modulated pharmacologically or through induction of ARHI. In addition to characterizing in vivo probe sensitivity and selectivity, we will obtain a pharmacodynamic readout of pro-autophagy drugs currently in clinical trials for the modulation of autophagy.
The ability to choose the best treatment for cancer relies upon our ability to monitor the effect of treatment in real-time and change treatments if no tumor death is observed or when healthy tissue begins to die. This proposal aims to develop imaging tools to quickly and non-invasively visualize cell death in tumor and normal tissue. These tools will help clinicians identify the best treatment for each individual patient and guide the development of new targeted therapies.
| Pisaneschi, Federica; Kelderhouse, Lindsay E; Hardy, Amanda et al. (2017) Automated, Resin-Based Method to Enhance the Specific Activity of Fluorine-18 Clicked PET Radiotracers. Bioconjug Chem 28:583-589 |
| Ornelas, Argentina; McCullough, Christopher R; Lu, Zhen et al. (2016) Induction of autophagy by ARHI (DIRAS3) alters fundamental metabolic pathways in ovarian cancer models. BMC Cancer 16:824 |
