Flow cytometric detection of MDSC populations in unfractionated blood.

56Background: MDSCs are a phenotypically diverse population of bone-marrow-derived cells that play an important role in tumor progression based on their immunosuppressive and pro-angiogenic properties. Mobilization of MDSCs from the bone marrow into the blood stream is dependent on tumor derived factors. Therefore, it is likely that levels of circulating MDSCs in cancer patients are reflective of tumor activity. However, the clinical applicability of MDSCs as a predictive biomarker in cancer has been hindered by a lack of consensus on the surface markers that defines them. Although there have been several attempts at harmonizing the nomenclature and characterization standards of MDSCs, there is still a lot of confusion particularly in the detection of MDSCs in unfractionated peripheral blood. To address this issue we have devised a simple flow cytometric test that reliably detects in whole blood the MDSCs subtypes that have been consistently reported to have clinical relevance in cancer. Methods: Whole bl...