The gene expression profiles of hypoxia-resistant (HR) human multiple myeloma cell lines

In multiple myeloma (MM), abnormal plasma cells interact with bone marrow (BM) stromal cells and vascular cells among others. A part of the BM milieu is considered highly hypoxic, and myeloma cells in situ may be influenced by circumstances other than normoxia in vitro. Hence, we attempted to confirm the role of hypoxic MM-derived exosomes in the BM milieu. We established a novel hypoxia-resistant cell line, RPMI8226-HR derived from RPMI8226 cells, KMS-11-HR derived from KMS-11, U266-HR derived from U266, and IM-9-HR derived from IM-9 cultured for >4 months under hypoxia (1% O2), as a model of MM cells localizing in an extensively hypoxic milieu. We used RPMI8226 cells and RPMI8226-HR cells, as donor cells, and HUVECs as recipient cells. Exosomes derived from RPMI8226 cells (normoxia or hypoxia) and exosomes derived from RPMI8226-HR cells (hypoxia-resistant, HR sub-line) were used for validation of angiogeneic activity, such as tube formation assay. Exosomes derived from the RPMI8226-HR cells significantly increased tube formation of HUVECs than those from RPMI8226 cells. Parental cells (RPMI8226, KMS-11, U266, IM-9) were cultured for 24 hours under normoxic conditions (20% O2). Hypoxia-resistant (HR) cells (RPMI8226-HR, KMS-11-HR, U266-HR, IM-9-HR) were cultured for 24 hours under hypoxic conditions (1% O2). Total RNA from each sample (Normal-BMSCs, MM-BMSCs and MGUS-BMSCs) was processed for hybridization onto GeneChip® human Gene 2.0 ST Array (Affymetrix) according to the manufacturer's protocol and scanned.