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Abstract 1941: Fluorescence lifetime imaging of treatment response in neuroendocrine tumor organoids

Gastroenteropancreatic neuroendocrine tumors (GEP-NET) are now the second most common form of gastrointestinal cancer, and account for roughly 60% of all neuroendocrine tumors. Unfortunately, no animal models or cell lines exist that reflect the in vivo characteristics of human GEP-NET’s for use as predictive models. Therefore, pre-clinical work is often not representative of the clinical outcome, so clinical trials begin in patients without rigorous pre-clinical validation of the treatment regimen. There is an established need to predict the most effective treatments prior to clinical trials for GEP-NET patients, to increase treatment efficacy and reduce toxicities. Here we show that a three-dimensional organoid model of primary patient tumors is representative of the original patient tumors. Furthermore, this study aims to use the organoid model to test a novel pre-clinical combination of ABT263, an experimental cancer drug that has been shown to enhance the effects of other chemotherapeutic agents, and the standard drug everolimus, on GEP-NET organoids. Previous studies have shown that ABT263, which targets Bcl-2, Bcl-XL and Bcl-w, induces apoptosis when used in combination with everolimus, making this a promising drug combination for GEP-NET patients. Treatment response to ABT263, everolimus, and the combination, was tested in three-dimensional organoids derived from six primary GEP-NET patients, using two-photon fluorescence lifetime imaging microscopy (FLIM). FLIM captures the fluorescence lifetime of metabolic cofactors NAD(P)H and FAD. Further, the fluorescence intensity of NAD(P)H divided by that of FAD (the redox ratio) was measured in all samples. Altogether, two-photon imaging of NAD(P)H and FAD fluorescence intensities and lifetimes (optical metabolic imaging, or OMI) in primary patient GEP-NET organoids provides a novel tool to measure metabolic changes with drug treatment. OMI measured metabolic differences induced by treatment in primary patient GEP-NETs when compared to control, at 72 hours post-treatment. All patients except one showed a decrease in redox ratio, which corresponds with a response, to the combination treatment. As metabolic imaging is performed to collect treatment response from more patients, this OMI data will be integrated into a multivariate analysis of variance to predict treatment response. Independent measures of organoid response, including changes in organoid diameter and immunohistochemistry, have been used to validate OMI predictions. We have shown that ABT263 plus everolimus is a promising combination treatment for GEP-NET’s. Overall, this work establishes the feasibility of personalized drug screens for GEP-NET’s using OMI in primary tumor organoids. Additionally, this platform can be used to identify new treatment regimens for improved GEP-NET patient outcomes, such as the ABT263 plus everolimus combination tested here. Citation Format: Amani A. Gillette, Christopher P. Babiarz, Cheri A. Pasch, Dustin A. Deming, Melissa C. Skala. Fluorescence lifetime imaging of treatment response in neuroendocrine tumor organoids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1941.