Nitric oxide (NO) has been reported to have a cytotoxic effect on various types of cancer. However, the efficient delivery of NO donors to tumors remains challenging. The present study used ibuprofen, which has a high binding affinity to human serum albumin (HSA). A total of two types of nitrated forms of ibuprofen, 4-[(nitrooxy)methyl]benzyl 2-(4-isobutylphenyl)propanoate [nitrated ibuprofen benzyl linker (NIB)] and 2-(nitrooxy)ethyl 2-(4-isobutylphenyl) propanoate [nitrated ibuprofen ethyl linker (NIE)], were synthesized. It was demonstrated that both NIB and NIE bound to the ibuprofen-binding site of HSA. Although NOx release was observed from NIB, but not NIE, intracellular NO release was detected from both NIB and NIE, which indicated that the mechanisms of NO release may be different for NIB and NIE. Both NIB and NIE induced concentration- and time-dependent cell death in human pancreatic cancer cells, whereas this cell death was not observed with ibuprofen, which could suggest that these cell death-inducing effects may be mediated by NO. The non-specific caspase inhibitor, z-VAD-FMK, inhibited cell death induced by NIB and NIE, but activation of caspase 3/7 was not observed. These results suggested that both NIB and NIE induced cell death through a non-caspase 3/7 pathway. The findings of the present study demonstrated that both NIB and NIE, as NO donors that could be retained in blood, may potentially be useful anti-cancer agent candidates in the future.
Keywords: caspase; cell death; human serum albumin; ibuprofen; nitric oxide; pancreatic cancer.
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