Effect of RRMs alone or in combination and of known apoptotic agents on the levels of intracellular calcium. Following preloading with the calcium fluorescent indicator FURA-2, NB4 cells (1 × 106/mL) were resuspended in calcium-containing phosphate-buffered saline (PBS) with calcium chloride at a concentration of 1.26 mM. Cells were placed in a cuvette under stirring at 37°C and changes in fluorescence were measured continuously with the use of a spectrophotofluorometer. The arrows indicate the addition of the various compounds at the concentrations shown (A, B). In panel C, ST1926 was used at a concentration of 1 μM, whereas ST2065 was added at a concentration of 100 μM. The left arrow indicates the addition of ST2065, whereas the right arrow indicates the addition of ST1926. In panel D, the concentrations considered are: ST1926, 1 μM; staurosporine, 1 μM; doxorubicin, 1 μM; etoposide, 1 μM; and fenretinide, 10 μM. Each tracing is representative of at least 3 independent experiments run in triplicate.
