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Letters to the Editor
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Figure 3. Cytotoxic effects of reveromycin A (RM-A) on multiple myeloma (MM) cells in combination with bortezomib. (A) Rabbit bone marrow cells were cul- tured on bone slices in the presence of soluble receptor activator of NF-κB ligand (RANKL) to generate osteoclasts (OC). INA-6 cells labeled with the fluorescein dye PKH26 at 1x106/mL were co-cultured with the OC generated on bone slices or cultured alone on bone slices. RM-A (1 mM), zoledronic acid (Zol) (5 μM), or CM-A (100 nM) were added as indicated. After culturing for 12 hours (h), 7-AAD was added to stain dead cells. (B) RM-A at 1 mM and/or bortezomib (Bor) at 5 nM were added as indicated. After culturing for 24 h, 7-AAD was added to stain dead cells. The distribution of 7-AAD-negative alive cells was counted within PKH-labeled MM cells in flow cytometry. Results were expressed as % changes from the baselines. (C) INA6 cell-bearing SCID-rab models as described in Figure 1A were prepared. RM-A (4 mg/kg, twice a day) and/or bortezomib (Bor) (0.5 mg/kg, twice a week) were intraperitoneally injected for 18 days (n=5 for each treatment). Saline was injected as a vehicle. Soft X-ray and micro-computed tomography (mCT) images ware taken before and after the treatment. Representative images of soft X-ray (upper panels) and mCT (lower panels) are shown. Soft tissue area is shown in red in cross sections of the rabbit bones in mCT images. (D) INA-6 cell-derived sIL-6R levels in mouse sera were measured after the treatment. (E) Hematoxylin and eosin (H&E) (upper) and tartrate-resis- tant acid phosphatase (TRAP) (lower) staining was performed in the rabbit bones resected from SCID-rab mice. White arrows indicate TRAP-positive OC. The rab- bit bones were further analyzed to count the numbers of OC over bone surface (OC/bone surface). Data are expressed as the mean ± standard error..
haematologica | 2021; 106(4)
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