Abstract PO-092: Immune profiling of the tumor microenvironment using multiplexed ion beam imaging (MIBI)

Abstract The growing application of immunotherapy and its ability, or inability, to modulate the tumor microenvironment (TME) has exposed a need for techniques capable of simultaneously tracking large numbers of biomarkers in complex tissue at sub-cellular resolution. To address this, MIBI uses tissue processed similar to standard immunohistochemistry (IHC) methods but with the advantage of being able to stain the tissue simultaneously with a panel of up to 40 metal labeled antibodies. The expression of proteins is imaged by MIBI in a single scan at subcellular spatial resolution by combining the high resolution of an ion beam and the sensitivity of time-of-flight secondary ion mass spectrometry (ToF-SIMS). To characterize the immune infiltrates present in a set of 10 non-small-cell lung carcinoma (NSCLC) samples, a panel of 22 metal labeled antibodies was used to stain the tissue. The stained tissue was then analyzed by MIBI and the masses of detected species were assigned to target biomolecules given the unique label of each antibody. Multi-step processing and segmentation utilizing highly expressed nuclear, membrane, and cytoplasmic markers were performed to accurately determine cell boundaries and enable quantitative analyses of marker expression, cell classification, and the spatial relationships between cell types. Results comparing the abundance of tumor cells, vascular cells, and immune cell subsets between samples identified “cold” tumors with few immune cells and inflamed samples that varied in the type of immune populations present. Immune checkpoint markers (LAG3, PD-1, PD-L1, TIM-3) were also quantified at single cell resolution. In conclusion, this study shows that MIBI offers high-parameter capability necessary to (1) identify the wide range of cell types present within the complex tumor immune landscape, (2) the spatial relationships between these different cell populations, and (3) the expression status of key immunoregulatory proteins. Citation Format: Jason Ptacek, Srimoyee Ghosh, Lourdes Pablo, Bin Feng, Hailei Zhang, Yari Sigal, Jay G. Tarolli, Murat Aksoy, Yi Zhang, Rachel Finck, Jessica Finn. Immune profiling of the tumor microenvironment using multiplexed ion beam imaging (MIBI) [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-092.