Adipocyte-differentiated MSCs protect PML-RARα–expressing PR9 cells from apoptosis. PR9 cells in the absence or presence of ZnSO4 pretreatment were cultured on adipocyte-differentiated MSC monolayers in the presence of 1 μM ATRA. After 96 hours of coculture, PR9 cells growing at the periphery or on top of the MSCs were harvested by extensive washing, and apoptosis was assessed by DNA flow cytometry (PI staining, sub-G1 region). ATRA-treated PR9 cells with or without ZnSO4 (200 μM) were cultured alone (□), cocultured in direct contact with adipocyte-differentiated MSCs (▦), cocultured in the presence of the chimeric OB-R protein (▤; OB-R competitive inhibitor), or separated from MSCs by a porous transwell inserts (▪). Graph represents mean ± SD of the results obtained in coculture experiments of PR9 cells without ZnSO4 (n = 2) and with ZnSO4 (n = 4). Statistically significant difference (*P < .05) was determined by paired Student t test; for all others, P ≥ .05.
