Abstract LB557: Multiphoton phosphorescence quenching microscopy reveals kinetics of tumor oxygenation during anti-angiogenesis and angiotensin signaling inhibition

Abstract

Abstract Purpose: The abnormal function of tumor blood vessels causes hypoxia fueling disease progression and conferring treatment resistance. The local level of oxygen experienced by a cell will determine its response, making it critical to understand tissue oxygen levels with a spatial resolution on the order of the size of a cell. While microenvironment normalization strategies alleviate global hypoxia, how local oxygen levels change are not known because there are no in vivo techniques to longitudinally assess tumor vessels and interstitial oxygen in tumors with sufficient resolution. Understanding the heterogeneity of oxygen levels after microenvironmental normalization will help improve the efficacy of various normalization strategies. Experimental Design: We developed a multiphoton phosphorescence quenching microscopy system using a low-molecular weight palladium porphyrin probe to measure perfused vessels, oxygen tension and their spatial correlations in vivo in mouse skin, bone marrow, and tumors. Further, we measured the temporal and spatial changes in oxygen and vessel perfusion in tumors in response to microenvironmental normalization. Results: We found that vessel function was highly dependent on tumor type. Although some tumors had vessels with greater oxygen carrying ability than normal skin, most tumors had inefficient vessels. Further, inter-vessel heterogeneity in tumors coincided with heterogeneous response to microenvironmental normalizing agents. Using both vascular and stromal normalizing agents, we show that spatial heterogeneity in oxygen levels persist, even with global reductions in hypoxia. Conclusions: We present the first study to examine the high-resolution spatial and temporal response of tumor vessels to two agents known to improve vascular perfusion globally. Our measurements demonstrate that the heterogeneities in the local imbalance of pro- and anti-angiogenic signaling lead to spatially heterogeneous changes in vessel structure and function. Microscale dynamic vascular changes should be considered in optimizing the dose and schedule of microenvironment normalizing therapies to improve function. Citation Format: John Martin, Ryan Lanning, Dai Fukumura, Timothy Padera, Rakesh Jain. Multiphoton phosphorescence quenching microscopy reveals kinetics of tumor oxygenation during anti-angiogenesis and angiotensin signaling inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB557.