Figure 5

BM cells increase drug resistance of tumor cells and protect them via upregulation of PD-L1. (A) B16F10 cells were treated with gemcitabine during co-culture with BM cells for 48 hours and then stained with annexin V and PI to determine proportions of necrotic and apoptotic cells by flow cytometry. (B) B16F10 cells were pre-incubated with PD-L1–blocking antibody for 3 hours and then treated with gemcitabine during co-culture with BM cells. Proportions of necrotic and apoptotic cells were determined as in (A). (C) B16F10 cells were treated with 5 μM PH797804 and 100 μM gemcitabine during co-culture with BM cells for 48 hours. Proportions of necrotic and apoptotic cells were determined as in (A). Data are presented as mean ± standard error (n = 3). BM = Bone Marrow, GEM = Gemcitabine.