Abstract P6-01-01: Validation of an Optical Imaging Platform to Identify Metabolic Vulnerabilities in Chemo-Resistant and Sensitive Tumors
Authors: Sunassee Enakshi D. , Maydew Elizabeth , Crouch Brian , Madonna Megan , Palmer Gregory M , Ramanujam Nimmi 
Published: March 2023

Abstract
Less than 20% of Triple Negative Breast Cancer (TNBC) patients experience long-term responses to mainstay chemotherapy, as tumors develop chemo-resistance. While combinations of chemotherapies and targeted therapies show potential improvements in TNBC clinical outcomes, patient stratification and prediction of treatment response is critical. Spatio-temporal metabolic reprogramming holds promise as a biomarker of therapy response as resistant tumor subpopulations utilize alternate metabolic pathways to escape therapy, enter minimum residual disease (MRD) and recur. Currently, there are limited tools to temporally evaluate heterogeneous changes along distinct metabolic axes in vivo at a spatial resolution capable of resolving vulnerabilities of residual tumor subpopulations. Here, we utilized an optical imaging-based platform to identify in vivo, longitudinal differences in metabolic reprogramming between a resistant and sensitive tumor model at high resolutions along three metabolic axes of TNBC chemoresistance (oxidative phosphorylation, glycolysis, and fatty acid oxidation). Xenografts were established by orthotopic cell injection and mice were treated with Paclitaxel (PTX), a commonly used chemotherapeutic drug in TNBC treatment, under a conventional maximum dose density regimen once the tumor reached a volume ~150mm3. MDA-MB-231 xenografts were resistant to PTX, defined as an initial response to PTX, a period of minimal residual disease, and a resurgence in tumor volume at ~60 days post drug withdrawal (n=3). HCC-1806 xenografts were sensitive to PTX, defined as an initial response to PTX in all mice and a complete cure in 7/10 mice. A separate cohort of mice for each tumor line was implanted with window chambers and imaged longitudinally at distinct stages of the tumor’s lifecycle with previously validated fluorophores 2-NBDG, TMRE, and Bodipy to directly report on glucose uptake, mitochondrial membrane potential, or fatty acid uptake, respectively. Wide field fluorescence imaging of MDA-MB-231 mice showed a significant increase in TMRE as early as two days after the 3rd PTX dose (n=5, p&lt; 0.05), a significant decrease in 2-NBDG as early as two days after the 5th PTX dose (n=5, p&lt; 0.05) and no significant changes in bodipy uptake. This increase in non-glucose-driven mitochondrial respiration was sustained during MRD. An increase in heterogeneity of TMRE uptake was seen during disease regression, MRD, and recurrence (n=5, p&lt; 0.05). HCC-1806 tumors showed increased glucose uptake, decreased fatty acid uptake, and no significant changes in mitochondrial membrane potential during acute treatment. Metabolic changes were transient, with no significant changes in probe uptakes after drug withdrawal and during MRD. Unlike the MDA-MB-231 tumors, no significant changes in the heterogeneity of TMRE uptake were seen following paclitaxel withdrawal in HCC-1806 tumors (n=5, p&gt;0.05). Our results point towards a metabolic switch from glycolysis to non-glucose, non-fat-driven mitochondrial respiration in MDA-MB-231 mice, possibly suggesting amino acid catabolism as a fuel during MRD. In the sensitive HCC-1806 line, we observed changes in glucose and fatty acid uptake during acute treatment, but no significant changes in metabolism during MRD. Consistent with the literature, our results point toward an increase in metabolic plasticity and heterogeneity in a chemo-resistant model compared to a chemo-sensitive one. Together, our results show the potential of using metabolic changes following therapy as a biomarker of therapy response, while highlighting the importance of tracking the change (or lack of change) in metabolism longitudinally. We aim to use this system to visualize and exploit early, in vivo metabolic vulnerabilities of disease regression that accompany local and distal recurrences.
Citation Format: Enakshi D. Sunassee, Elizabeth Maydew, Brian Crouch, Megan Madonna, Gregory M Palmer, Nimmi Ramanujam. Validation of an Optical Imaging Platform to Identify Metabolic Vulnerabilities in Chemo-Resistant and Sensitive Tumors [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-01-01.