Functional Intravital Imaging Using Hyperspectral Fluorescence Microscopy to Characterize Tumor Physiology and Therapeutic Response

Optical methods enable non-destructive, quantitative, longitudinal functional monitoring of tissue. Intravital imaging using window chamber models allows the wide range of available optical microscopy techniques to be applied to living tissues in otherwise inaccessible sites. The acquisition and analysis of three types of functional information will be discussed: 1) hemodynamic parameters, including oxygen saturation and blood flow, 2) oxygen sensing nanoparticles for assessment of tissue hypoxia, and 3) fluorescent reporters for cell tracking and gene expression. These enable quantitative assessment of oxygen supply and consumption, including fluctuating hypoxia in tumors. The combination of these tools facilitates a more complete characterization of tumor physiology and molecular responses, and how these interplay to influence tumor response to therapy. I will describe two different therapeutic strategies where optical sensing techniques can play an important role in assessing functional response. First, a novel therapeutic approach developed through partnership with Vindico Pharmaceticals involves administration of polymersome encapsulated myoglobin nanoparticles. This was originally hypothesized to have utility as an oxygen carrier to improve tumor oxygenation, but in fact has profound vascular effects and results in severe tumor necrosis and vascular shutdown. Secondly, radiation therapy combined with inhibition of the PD-1 immune checkpoint pathway therapy has shown tremendous promise in a number of preclinical settings. Here we develop multiscale imaging approaches to assess the functional effects of this combined therapy.

Greg Palmer, PhD, completed his PhD at the University of Wisconsin, Madison in 2005 under Dr. Nimmi Ramanujam. His project was to develop quantitative Monte Carlo based algorithms to extract tissue optical properties from fluorescence and diffuse reflectance spectra, particularly applied to the diagnosis of breast cancer. He then studied as a postdoc under Dr. Mark Dewhirst at Duke University, where he worked to apply optical techniques to evaluate therapeutic response in preclinical and clinical settings. He has been an Assistant Professor at Duke since 2009, Associate Professor since 2014, where he has worked to continue developing optical techniques, and in particular window chamber and intravital imaging techniques.