The Pattern of Mesenchymal Stem Cell Expression Is an Independent Marker of Outcome in Multiple Myeloma

Purpose: Mesenchymal stem cells (MSC) are an essential component of the bone marrow microenvironment and have shown to support cancer evolution in multiple myeloma. Despite the increasing evidence that multiple myeloma MSCs differ from their healthy counterparts, little knowledge exists as to whether MSCs independently influence disease outcome. The aim of this study was to determine the importance of MSCs in disease progression and outcome in multiple myeloma.Experimental Design: To determine the impact of MSCs on multiple myeloma outcome in an in vivo system, we first identified genes from cultured MSCs that were specific to MSC expression and were not or minimally expressed in plasma cells (PC) or other cells present in bone marrow aspirates. We then applied this MSC gene signature to whole bone marrow biopsies of multiple myeloma patients compared with healthy controls and determined MSC expression scores specific to multiple myeloma and predictive of outcome.Results: We show that multiple myeloma MSC gene expression signatures can differentiate multiple myeloma from monoclonal gammopathy and smoldering multiple myeloma (SMM) as well as from healthy controls and treated multiple myeloma patients who have achieved a complete remission. We identified a prognostic gene score based on three MSC specific genes, COL4A1, NPR3 and ITGBL1, that was able to predict progression-free survival in multiple myeloma patients and progression into multiple myeloma from SMM.Conclusions: Our findings show that progression of multiple myeloma and of SMM into multiple myeloma does not rely solely on intrinsic PC factors, but is independently affected by the biology of the surrounding microenvironment. Clin Cancer Res; 24(12); 2913-9. ©2018 AACR.