Figure 1. Effects of nitrosylcobalamin (NO-Cbl) and chemotherapeutic agents on the proliferation of A375 (melanoma), A549 (lung), ACHN (renal), HeLa (cervical) HEY (ovarian), HT29 (colon), MCF-7 (breast), OC-2 and OC-3 (platinum and paclitaxel refractory ovarian), OVCAR-3 (ovarian), WM9 and WM3211 (melanoma), and P388 (murine leukemia).

Cells were pre-treated with NO-Cbl for 16 h followed by addition of chemotherapeutic agents for five days, and growth was measured by the colorimetric sulforhodamine B assay(37, 75). Data points represent the combination index comparing low, medium, and high combinations of NO-Cbl and each chemotherapeutic agent (mean of eight replicates) to assess synergy. Synergy between NO-Cbl and various chemotherapeutic agents was determined by median effect analysis(38), (combination index >1 indicates antagonism,  = 1 indicates additivity, and <1 indicates synergy). The sequential treatment of NO-Cbl and chemotherapeutic drugs induced synergistic antiproliferative activity in 77.7% of the combinations examined.