TRAIL disrupts MM cell-OC interaction under TAK1 inhibition. (A) Murine bone marrow mononuclear cells were plated onto 24-well culture plates (1 × 106 cells per well). The cells were treated with M-CSF for 3 days, followed by sRANKL (25 ng/mL) for 2 days to generate adherent preosteoclastic cells. After washing, the adherent preosteoclastic cells were cocultured for 3 days with murine 5TGM1 MM cells at 1 × 104 cells per well. TRAIL at 100 ng/mL and LLZ at 300 nM were added as indicated. TRAP-positive MNCs (5 or more nuclei) were counted as OCs. Data were expressed as mean ± standard error. *P < .05. Microscopic images of TRAP staining in representative cultures are shown (lower panels). Original magnification ×100. Bar represents 100 μm. (B) Human OCs were generated in 24-well culture plates with M-CSF and sRANKL from PBMCs from a healthy donor. The OCs were tightly attached on the culture plates. MM cell lines, INA-6, RPMI 8226, and MM.1S, were cultured alone or cocultured with the OCs for 48 hours. TRAIL at 100 ng/mL and LLZ at 300 nM were added as indicated. MM cells were collected, and their viability was measured by WST-8 assay. Data were expressed as mean ± SD. *P < .05.
