The absence of reliable, robust, and non-invasive biomarkers for anti- Programmed cell death protein 1 (PD-1) immunotherapy is an urgent unmet medical need for the treatment of cancer patients. No predictive biomarkers have been established based on the direct assessment of T cell functions, the primary mechanism of action of anti-PD-1 therapy. In this study, we established a model system to test T cell functions modulated by Nivolumab using anti-CD3 monoclonal antibody (mAb)-stimulated peripheral blood mononuclear cells (PBMCs), and characterized T cell functions primarily based on the knowledge gained from retrospective observations of patients treated with anti-PD-1 immunotherapy. During a comprehensive cytokine profile assessment to identify potential biomarkers, we found that Nivolumab increases expression of T helper type 1 (Th1) associated cytokines such as interferon-γ (IFN-γ) and interleukin-2 (IL-2) in a subset of donors. Furthermore, Nivolumab increases production of Th2, Th9, and Th17 associated cytokines, as well as many proinflammatory cytokines such as IL-6 in a subset of donors. Conversely, Nivolumab treatment has no impact on T cell proliferation, expression of CD25, CD69, or Granzyme B, and only modestly increases in the expansion of regulatory T cells. Our results suggest that assessment of cytokine production using a simple PBMC-based T cell functional assay could be used as a potential predictive marker for anti-PD-1 immunotherapy.

Immune checkpoint inhibitors (ICIs) such as the anti-PD-1 antibody Nivolumab, achieve remarkable clinical efficacy in patients with late stage cancers. However, only a small subset of patients benefit from this therapy. Numerous clinical trials are underway testing whether combining ICIs with other anti-cancer therapies can increase this response rate. For example, anti-PD-1/PD-L1 therapy combined with MAP kinase inhibition using BRAF inhibitors (BRAFi) and/or MEK inhibitors (MEKi) are in development for treatment of late stage melanomas. However, the benefits and underlying mechanisms of these combinatorial therapies remain unclear. In the current study, we assess the effects of MAPK inhibition on Nivolumab-induced T cell responses. Using an in vitro mixed lymphocyte reaction assay, we demonstrate that Nivolumab-induced T cell activation is highly heterogeneous. While BRAFi inhibits Nivolumab-induced cytokine production, T cell proliferation, activation markers (CD69, CD25), and Granzyme B in a substantial proportion of donor pairs, a small subset of donor pairs shows an additive effect. MEKi alone significantly inhibits Nivolumab-induced T cell activation; the addition of BRAFi significantly enhances this inhibitory effect. Mechanistically, the effects of BRAFi and/or MEKi on Nivolumab-induced T cell activation may be due to alteration of the activation of the AKT and T cell receptor (TCR) signaling pathways. Our results suggest that MAPK inhibition may not provide a clinical benefit for most melanoma patients being treated with anti-PD-1 therapy.

Immune checkpoint inhibitor (ICI) therapy has revolutionized anti-cancer treatment for many late-stage cancer patients. However, ICI therapy has thus far demonstrated limited efficacy for most patients, and it remains unclear why this is so. Interleukin 10 (IL-10) is a cytokine that has been recognized as a central player in cancer biology with its ability to inhibit anti-tumor T cell responses. Recent studies suggest that IL-10 might also exert some intrinsic anti-tumor T cell responses, and clinical studies using recombinant IL-10 alone or in combination with ICI are underway. This paradoxical effect of IL-10 and its underlying mechanisms impacting ICI-modulated T cell responses remain poorly understood. In this study, using an in vitro mixed lymphocyte reaction assay, we found that treatment with ICIs such as the anti-programmed cell death receptor-1 (PD-1) mAb nivolumab elicits a strong expression of IL-10. While neutralization of IL-10 signaling with an anti-IL-10 specific mAb significantly decreases the production of IFN-γ by T cells in a cohort of donor cells, the opposite effect was observed in other donor cells. Similarly, neutralization of IL-10 signaling significantly decreases the expression of T cell activation markers Ki67 and CD25, as well as the production of Granzyme B in a cohort of donor cells, whereas the opposite effect was observed in others. Furthermore, we found that nivolumab and IL-10 differentially modulate the signal transducer and activator of transcription 3 (STAT3) and AKT serine–threonine kinase pathways. Finally, we found that nivolumab activates the mitogen-activated protein kinase (MAPK) pathway, which in turn is responsible for the observed induction of IL-10 production by nivolumab. These findings provide new insights into the mechanisms underlying anti-PD-1-modulated T cell responses by IL-10, which could lead to the discovery of novel combination treatments that target IL-10 and immune checkpoint molecules.

Sample multiplexing in flow cytometry is a powerful technique which allows for reduction of error, inclusion of control samples for batch effect correction, and reduction in both time and consumable usage. Current industry standard for barcoding in mass cytometry is an intracellular reagent, which requires fixation and permeabilization of sample prior to barcoding. We developed a barcode using the ubiquitous and well-tolerated membrane labeling lectin, wheat germ agglutinin. This barcode effectively labels all tested cell types, both live and fixed. We determine that barcode yields, or the ratio of debarcoded cells to total input cells, is stable in live pooled sample for at least an hour. This barcode does not show differential performance across major PBMC lineages. Thus, this universal wheat germ agglutinin-based barcode represents an advance in gentle, non-reactive cell surface barcoding for live cells.