Sustained Growth of Primary Myeloma Cells in Coculture with Whole Donor Bone Marrow Is Associated with Induced Secretion of the Microenvironmental Mediator of Cytokinesis, Hemicentin-1

Primary human myeloma (MM) cells do not survive in culture while current systems for growing these cells are limited to coculture with specific bone marrow (BM) cell type or growth in immunodeficient animals. The aim of the study was to establish a coculture system for studying long-term growth of primary MM and their interaction with whole BM microenvironment, namely normal bone marrow (NBM) system . Whole BM cells from healthy donors (n=20) were cultured in medium supplemented with serum (10% v/v) pooled from MM patients for 7 days followed by coculture with CD138-selected primary MM cells (4:1 NBM:MM ratio) or MM cell lines (10:1 NBM:MM ratio) for ≥7 days. This NBM system is composed of adherent and non-adherent compartments. Adherent cells were mainly macrophages and mesenchymal stem cells (MSCs) whereas non-adherent cells contained typical hematopoietic cells including CD19+, CD3+, CD11b+ and CD33+ cells. Growth of MM cells was determined by CD45/CD38 flow cytometry and by bioluminescence of luciferase-expressing MM cells. MM cells or subset of MM cells from all patients (n=60) survived and grew in this system regardless of molecular risk or subtype, and MM growth was comparable to coculture with the supportive osteoclasts or MSCs. Adherent and non-adherent compartments supported MM cells which required patient’s serum for optimal growth. In 14 of 20 experiments, number of MM plasma cells, quantified by flow cytometry or bioluminescence analysis was increased by 58±12% (p Xu and Vogel, Curr Biol 2011 ) but has yet not been implicated in MM. Hemicentin-1 gene expression was detected in cultured NBM and MSCs but not in primary MM cells, MM lines or CD11b+ NBM cells. Induction of hemicentin-1 expression in MSCs after coculture with MM cells was validated by immunohistochemistry. Hemicentin-1 expression is higher in random bone biopsies from newly diagnosed MM patients (n=406) compared to donor biopsies (n=25, p Disclosures No relevant conflicts of interest to declare.