Characterization of Immunosuppressive Cells Using MultiOmyx in Hematological Malignancies

Abstract

Abstract Background Tumor associated macrophages (TAM) and myeloid-derived suppressor cells (MDSC) can assist tumors to escape immune surveillance within the tumor microenvironment (TME). Based on phenotypical characteristics, MDSC can be further subdivided into granulocytic MDSC (G-MDSC) and monocytic MDSC (M-MDSC). These myeloid cell populations are well characterized and extensively studied in the solid tumors and their immunosuppressive function can be exerted via direct recruitment of Regulatory T cells (Treg). However, the role of these cells has been less studied in hematological malignancies (HM). Methods We report an analysis of MDSC, M2 macrophages and Treg using MultiOmyx multiplexed IF assay in clinical samples diagnosed with AML, HL and DLBCL. MultiOmyx technology enables detection and visualization of up to 60 protein biomarkers on a single FFPE slide. The FFPE sections were stained with a 13-marker panel including Arg1, CD11b, CD14, CD15, CD16, CD33, CD68, CD163, HLA-DR, CD3, CD4, CD8 and FOXP3. Results Both M-MDSC and G-MDSC were found to accumulate within the TME in different HM, with higher frequency of G-MDSC over M-MDSC. The data also revealed an abundant M2 macrophages present in the TME, especially in AML patient samples. Using the MultiOmyx proprietary algorithm, we quantified the counts and density of MDSC, TAM and Treg cells and studied the spatial correlations between different subsets of immunosuppressive cells. The results in the patient samples indicated that Treg was in closer proximity to M2 TAM than MDSC. Conclusions Targeting tumor-infiltrating myeloid cells has emerged as a new immunotherapeutic strategy. MultiOmyx 13-plexed panel has the potential to monitor the changes of immunosuppressive myeloid cells in response to immune modulating drugs such as MDSC-targeting drugs (e.g. PDE-5 inhibitors, COX-2 inhibitors), TAM-targeting agents (e.g. anti-CSF1R) and combination therapy in treatment of HM.