Effects of PBMC-OCs on growth and survival of primary MM cells and MM cell lines. Scanning microscopic images of primary MM cells cultured alone (A) or cocultured with OCs generated from PBMCs from the same patient with MM (B) for 14 days in alpha-MEM containing 10% FBS. Primary MM cells (2 × 10⁵/mL) isolated from a patient with MM (C), an IL-6–dependent MM cell line, OPC (D), or a factor-independent MM cell line, U266 (E), were cultured in quadruplicate in the presence or absence of OCs (1 × 10⁴/mL) derived from healthy individuals. At the indicated time points, viable cell number was determined by trypan blue staining under microscopy. Data were expressed as means ± SD.