113 Label-free dynamic optical coherence microscopy assesses cytotoxicity in response to immune checkpoint inhibitors in ex vivo live tumor tissue
Year: 2024
Type: conference-abstract
Abstract: Background Current cancer imaging assays typically use dyes to assess treatment induced cytotoxicity and, due to their lack of specificity and poor permeability, are often limited to studies performed on cell monolayers and spheroids as opposed to in primary tissues, where the native tumor microenvironment and architecture are maintained.1 2 The emerging label free imaging modality dynamic optical coherence microscopy (dOCM) analyzes temporal signals for fluctuations due to metabolic processes and cellular motions. dOCM allows for longitudinal and nondestructive assessment deep in intact tissues removing the need for exogenous reporters which can cause potential bias in interpretation, increase experimental complexity and often require invasive tissue preparation. Using dOCM, we previously assessed chemically induced cytotoxicity which was validated using known exogenous viability markers in tissues.3 In the current study, we used the Elephas platform for the first time to explore whether dOCM can detect cytotoxic changes in tumor tissue in response to immune checkpoint inhibitor (ICI) treatment. Methods For in vivo studies, mice harboring CT26 syngeneic tumors were treated with a combination of ICIs or an IgG control. ICI-mediated tumor growth inhibition was quantified relative to the IgG treated cohort. In ex vivo studies, untreated CT26 tumors were processed using a proprietary cutting instrument to create live tumor fragments (LTFs) which were cultured and treated with a combination of ICIs or IgG control. LTFs were imaged using dOCM to quantify live/dead cells and secretory factors were measured in the culture supernatant across several time points. Multiphoton microscopy was used to image commercially available viability dyes to validate dOCM live contrast. LTFs were formalin fixed and paraffin embedded for histology and multiplex immunofluorescence (mIF). Results We characterized the time course of ICI-induced cytokine secretion and cytotoxicity ex vivo and were able to demonstrate correlation of these results to ICI-mediated tumor growth inhibition in vivo. We showed differences in the infiltration and spatial distribution of T cells within the LTFs following ICI treatment using mIF. Our cytotoxicity results using dOCM were validated using viability dyes as a ground truth measure of cytotoxicity. Conclusions Here, we show that ICI-mediated cytotoxicity can be measured in tumor tissue using dOCM, a non-destructive, label-free imaging technique. The Elephas platform combining dOCM, mIF and cytokine secretion shows the potential to predict response to ICIs ex vivo. These data support the ability to use dOCM for the rapid assessment of drug treatment efficacy in primary tumor tissues with immunotherapies. References Riccardi C, Nicoletti I. Analysis of apoptosis by propidium iodide staining and flow cytometry. Nat Protoc 2006;3:1458-1461. Rosenberg M, Azevedo NF, Ivask A. Propidium iodide staining underestimates viability of adherent bacterial cells. Sci Rep 2019;1:6483. Liu CJ, Smith JT, Wang Y, et al. Assessing cell viability with dynamic optical coherence microscopy. Biomed Opt Express 2024;3:1408-1417.
Institution: University of Wisconsin–Madison
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4404052765