Figure S1 - An Inverse Switch in DNA Base Excision and Strand Break Repair Contributes to Melphalan Resistance in Multiple Myeloma Cells

Intracellular level of ROS was detected by flow cytometry using 5-(and-6)-carboxy-2′,7′-dichlorodihydrofluorescein diacetate (carboxy-H2DCFDA, Molecular Probes) according to the manufacturer’s protocol. Briefly, cells (1×106 cells/mL) were washed with PBS and incubated in PBS buffer containing 10 uM dye for 30 min at 37°C. H2DCFDA-stained cells were returned to growth medium and treated with 50 uM Melphalan. Flow cytometry analysis was performed after 6 hours of incubation, at 488 nm excitation and 530 nm emission. Parallel treatment of cells with the oxidizing agent tert-butyl hydroperoxide (TBHP, Sigma) was included as a positive control for oxidative stress in the assay. (EPS)