title: Toward harmonized phenotyping of human myeloid-derived suppressor cells by flow cytometry: results from an interim study.
abstract: There is an increasing interest for monitoring circulating myeloid-derived suppressor cells (MDSCs) in cancer patients, but there are also divergences in their phenotypic definition. To overcome this obstacle, the Cancer Immunoguiding Program under the umbrella of the Association of Cancer Immunotherapy is coordinating a proficiency panel program that aims at harmonizing MDSC phenotyping. After a consultation period, a two-stage approach was designed to harmonize MDSC phenotype. In the first step, an international consortium of 23 laboratories immunophenotyped 10 putative MDSC subsets on pretested, peripheral blood mononuclear cells of healthy donors to assess the level of concordance and define robust marker combinations for the identification of circulating MDSCs. At this stage, no mandatory requirements to standardize reagents or protocols were introduced. Data analysis revealed a small intra-laboratory, but very high inter-laboratory variance for all MDSC subsets, especially for the granulocytic subsets. In particular, the use of a dead-cell marker altered significantly the reported percentage of granulocytic MDSCs, confirming that these cells are especially sensitive to cryopreservation and/or thawing. Importantly, the gating strategy was heterogeneous and associated with high inter-center variance. Overall, our results document the high variability in MDSC phenotyping in the multicenter setting if no harmonization/standardization measures are applied. Although the observed variability depended on a number of identified parameters, the main parameter associated with variation was the gating strategy. Based on these findings, we propose further efforts to harmonize marker combinations and gating parameters to identify strategies for a robust enumeration of MDSC subsets.
authors.affiliation: Section of Oncology and Immunology, Department of Surgery, Oncology and Gastroenterology, University of Padova, Via Gattamelata, 64, 35128, Padua, Italy. susanna.mandruzzato@unipd.it.|Veneto Institute of Oncology IOV - IRCCS, Padua, Italy. susanna.mandruzzato@unipd.it.
authors.forename: Susanna
authors.identifier: http://orcid.org/0000-0002-0707-995X
authors.initials: S
authors.lastname: Mandruzzato
authors.affiliation: Department of Otorhinolaryngology, University Hospital Essen, Essen, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Brandau
authors.affiliation: TRON Translationale Onkologie an der Universitätsmedizin der Johannes Gutenberg-Universität Mainz GmbH, Mainz, Germany.|Cell Therapy Group, Immuno-Oncology and Combinations, GlaxoSmithKline, Stevenage, UK.
authors.forename: Cedrik M
authors.initials: CM
authors.lastname: Britten
authors.affiliation: Section of Immunology, Department of Pathology and Diagnostics, Verona University Hospital, Verona, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Bronte
authors.affiliation: Section of Oncology and Immunology, Department of Surgery, Oncology and Gastroenterology, University of Padova, Via Gattamelata, 64, 35128, Padua, Italy.|Veneto Institute of Oncology IOV - IRCCS, Padua, Italy.
authors.forename: Vera
authors.initials: V
authors.lastname: Damuzzo
authors.affiliation: Department of Immunology, Institute for Cell Biology, University of Tübingen, Tübingen, Germany.
authors.forename: Cécile
authors.initials: C
authors.lastname: Gouttefangeas
authors.affiliation: Immatics Biotechnologies GmbH, Tübingen, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Maurer
authors.affiliation: Cancer Sciences Unit, Faculty of Medicine, Experimental Cancer Medicine Centre, Southampton General Hospital, University of Southampton, Tremona Road, Southampton, UK.
authors.forename: Christian
authors.initials: C
authors.lastname: Ottensmeier
authors.affiliation: Department of Clinical Oncology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Sjoerd H
authors.initials: SH
authors.lastname: van der Burg
authors.affiliation: Department of Clinical Oncology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Marij J P
authors.initials: MJ
authors.lastname: Welters
authors.affiliation: Immatics Biotechnologies GmbH, Tübingen, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Walter
mesh_terms: D000954:Antigens, Surface / Q000378:metabolism; D015415:Biomarkers; D002452:Cell Count; D005434:Flow Cytometry; D064368:Healthy Volunteers; D006801:Humans; D016130:Immunophenotyping; D022423:Myeloid Cells / Q000276:immunology / Q000378:metabolism*
chemical_list: D000954:Antigens, Surface; D015415:Biomarkers
keywords: Flow cytometry; Myeloid-derived suppressor cells; Phenotyping; Proficiency panel