Single-Cell Multiplexed Proteomics on the IsoLight Resolves Cellular Functional Heterogeneity to Reveal Clinical Responses of Cancer Patients to Immunotherapies

Cancer immunotherapies, in particular adoptive T cell therapy and immune-checkpoint blockade therapy have demonstrated a remarkable success in the treatment of cancer. However, due to heterogeneous functionality and complex immune response of immune cells, it remains challenging to identify predictive biomarkers which have the potential to correlate with efficacy and adverse effects of immunotherapies and help selecting patients who might benefit from the therapy, developing more personalized therapeutics as well as reducing clinical trial cost. The single-cell IsoCode chip in conjunction with fluorescent ELISA-based assay enables a simultaneous detection up to 40+ proteins secreted from live single immune cells, providing a large portion of the assayable functions for each immune cell type, and thus precise assessment of multifunctional, or polyfunctional, heterogeneity of each immune cell type. This unique functional detection capability provides a powerful solution to unmet needs in immunotherapy patient profiling today. Recently, the single-cell metric termed polyfunctional strength index (PSI™) by IsoCode chip computed from preinfusion anti-CD19 chimeric antigen receptor (CAR)-T cell products has demonstrated a significant association with clinical response and cytokine release syndrome (CRS) of cancer patient to the therapy after cell product infusion. This chapter elucidates IsoPlexis single-cell highly multiplexed proteomic platform and provides technical details for characterizing cell products and various cell subsets from peripheral blood, bone marrow, or tumor tissues using this assay.