Abstract 4026: Growth of monoclonal gammopathy of undetermined significance (MGUS) in a 3-dimensional co-culture in vitro model

Introduction: Multiple Myeloma (MM) is an incurable cancer with a pre-malignant clonal phase of disease called monoclonal gammopathy of undetermined significance (MGUS). Most patients with MGUS do not develop MM and the biology underlying this potential transformation is unclear. Investigations to prevent the development of MM from MGUS is limited by infrequent MGUS progression. MGUS cells have historically proven difficult to grow in vitro because of slow rates of proliferation and difficulty in sustaining cell cultures. An in vitro model of MGUS that circumvents these challenges by recreating a supportive bone marrow microenvironment will allow further investigation into the pathogenesis of disease progression. Herein, we examine a novel stroma-based in vitro model of MGUS and MM using bone marrow stromal cells to support and maintain a bi-directional relationship within the clonal plasma cell population. Aim: To grow MGUS derived plasma cells by recreating a supportive bone marrow microenvironment using a 3-dimensional in vitro model. Methods: We collected a CD38+ cell fraction and a bone marrow stromal fraction from patients with plasma cell dyscrasias using a Miltenyl Biotec column Separator. We seeded stromal cells from a female, kappa expressing MGUS patient or a healthy donor onto a polyglycolic acid/ poly L-lactic acid 90/10 (PLGA) copolymer scaffold. Then, a CD38+ cell fraction from a male patient with lambda secreting PCL or MM cell line U266 or MM1.s (both male, lambda expressing cell lines) were added to create 3D co-culture conditions. For comparison, a 2 dimensional co-culture condition was created by growing MM patient cells or cell lines over a bone marrow stromal cell layer without scaffold.. After one week, samples were formalin fixed and sectioned for immunohistochemistry (IHC) and stained with CD138, kappa, lambda, and ki-67. Fluorescent in situ hybridization (FISH) was used to label X and Y chromosomes. Results: IHC demonstrated proliferation of CD138+ cells evident by Ki-67 expression in in 3-D co-culture systems. There was no growth of the patient derived CD38+ cells in 2-D co-culture and the proliferation of of cell lines was diminished in 2-D versus 3-D. When seeded on healthy donor stroma in 3-D, the CD38+ cells from all sources were lambda restricted. When seeded on the MGUS stroma, the MM1.s cells were lambda restricted while PCL cells showed both kappa and lambda expression with a dominance of kappa expression, and U266 cells showed kappa restriction. FISH demonstrated a female chromosomal pattern with X,Y in the plasma cells from the 3D co-cultures in the case of U266 or PCL cell 3-D co-culture with MGUS stroma. Conclusion: This is the first demonstration of in vitro growth of plasma cells from a patient with MGUS. We speculate the aggressive plasma cells from the U266 cell line and the PCL sample induced the growth of a CD38- cell fraction and caused differentiation to plasma cells. Citation Format: Brea C. Lipe, Omar Aljitawi, Tara Lin, Joseph Fontes. Growth of monoclonal gammopathy of undetermined significance (MGUS) in a 3-dimensional co-culture in vitro model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4026. doi:10.1158/1538-7445.AM2015-4026