Abstract 5383: Dexter࣪ microfluidic platform spatially resolves antigen presentation and T cell functions in microdroplets and deciphers dynamic tumor-immune interaction network
Authors: Lal Ashwin , Singh Ranjeet , Sane Abhay , Manglik Rushil , Keshari Ravi R. , Mohanasundaram SM , Majumder Pradip K. , Majumder Biswanath 
Published: June 2022

Abstract
Background: Immune checkpoint inhibitors are being used in clinics for a diverse set of cancers. However, the outcome is highly contextual and personalized with consistently low response rates. Understanding the mechanistic barriers at single cell levels is key for novel candidate selection. Here we describe Dexter࣪ microfluidic platform that can create highly parallel nanobioreactors on a chip to study cellular functions and interactions at the single cell level. Using microliter volumes of live tumor and human PBMC, we showed modulation of dynamic tumor-immune crosstalk at single cell level.
Methods: The Dexter࣪ microfluidic platform was used for functional characterization at single cell resolution. The platform integrates an array of nanoliter sized droplets with cell encapsulation, multicolor fluorescence imaging and selective cell retrieval. PBMC, RBC and cancer cells were fluorescently (CFSE, PKH) labelled and used to interrogate effector cell functions following exposure to immune modulating milieu in nanoliter droplets. CD8+T cells were activated and labelled. Individual and clustered tumor cells were challenged with stimulated PBMC. Finally, using bioinformatic tools, we construct a Tumor immune Interactive Network (TiIN) and simulate perturbation.
Results: Our data confirmed preservation of surface markers, T cells and tumor-immune specific intracellular and surface events including cell-cell contacts at the level observed before their encapsulation in microfluidic droplets. Both size and intensity of the signals were maintained without significant loss. Platform displayed critical events like antigen presentation, tumor-probiotic interface, T cell engagement with microbeads similar to APC dimensionalities and function. Both spiked tumor and immune cells showed high degree of recovery. Spatially resolved dynamic profiling in this platform further revealed immune phenotypic plasticity and vulnerabilities of tumor cells upon exposure to immune checkpoint agents. Finally, we, measured the killing of tumor cells by using different effector : target ratio that complement hot and cold niche. We observed differential killing of target when T cells were primed using immunomodulators.
Conclusion: Our data highlights the versatility of Dexter࣪ platform in deciphering mechanistically critical tumor-immune interactions while parallelly resolving single cell events. This offers suitable means of profiling response to novel immunooncology candidates.
Citation Format: Ashwin Lal, Ranjeet Singh, Abhay Sane, Rushil Manglik, Ravi R. Keshari, SM Mohanasundaram, Pradip K. Majumder, Biswanath Majumder. Dexter࣪ microfluidic platform spatially resolves antigen presentation and T cell functions in microdroplets and deciphers dynamic tumor-immune interaction network [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 5383.