Abstract
Purpose: The survival and progression of multiple myeloma (MM) cells rely heavily on supportive factors and cells within the MM microenvironment, notably macrophages. The PI3K signaling pathway plays a crucial role in both myeloma cells survival and macrophage polarity, making it a potential target for altering the MM microenvironment dynamics. Methods: In this study, the impact of LY294002, a PI3K signaling pathway inhibitor, on the viability of U266 myeloma cells in mono-culture and MM patient-derived bone marrow mononuclear cells (BM-MNCs) in co-culture was investigated. Additionally, the effect of treatments on the M1/M2 macrophage ratio was assessed. Cultures were conducted in both two-dimensional (2D) matrix-free and fibrin gel-based three-dimensional (3D) environments. Results: The treatment significantly increased U266 cell death in 2D cultures, dose-dependently compared to control. However, this effect was not replicated in 3D cultures. In both 2D and 3D cultures, the percentages of cells in G0/G1 phase were dose-dependently increased, compared to the untreated control. However, the percentages of cells in S and G2/M phases in both 2D and 3D cultures were dose-dependently decreased, compared to control. Treatment of BM-MNCs with LY294002 showed patient- and culture-dependent patterns of CD138+ myeloma cell death and M1/M2 macrophage ratio, contrasting the observed consistent responses in U266 mono-culture.Conclusion: LY294002 affected U266 cell viability and cell cycle in a dose-dependent manner in 2D mono-cultures. However, its impact varied in 3D cultures. Treatment of MNCs showed varied responses based on individuals and culture conditions, underscoring the need for more similar tumor microenvironment recapitulation for drug screening.