NO-donating nonsteroidal antiinflammatory drugs (NSAIDs) inhibit colon cancer cell growth more potently than traditional NSAIDs: A general pharmacological property?

The novel nitric oxide-donating nonsteroidal antiinflammatory drugs (NO-NSAIDs), consisting of a traditional NSAID to which a NO releasing moiety is covalently attached, may have an important role in colon cancer prevention and/or treatment. Preclinical studies have shown that NO-aspirin (NO-ASA) is more potent than traditional ASA in preventing colon cancer. Preclinical and clinical studies have also documented its superior safety, compared to traditional ASA. To evaluate the role of this structural modification on the cancer cell growth inhibitory effect of NSAIDs, we studied seven pairs of traditional NSAIDs (ASA, salicylic acid, indomethacin, sulindac, ibuprofen, flurbiprofen, piroxicam) and their corresponding NO-NSAIDs. All NO-NSAIDs (except NO-piroxicam which is a salt and not a true NO-NSAID) have greater potency in inhibiting HT-29 and HCT-15 colon cancer cell growth compared to their NSAID counterparts: the IC₅₀s of the NO-NSAIDs were enhanced between 7- and 689-fold in HT-29 cells and 1.7- to 1083-fold in HCT-15 cells over those of the corresponding NSAIDs. Their growth inhibitory effect is due to a profound cell kinetic effect consisting of reduced cell proliferation and enhanced cell death. Since HT-29 cells express cyclooxygenases but HCT-15 do not, this effect appears independent of cyclooxygenase in the colon cancer cells. Thus the structural modification of these traditional NSAIDs leading to NO-NSAIDs enhances their potency in inhibiting colon cancer cell growth. Our findings suggest that the enhanced potency imparted on NSAIDs by this structural modification represents a pharmacological property that may be a general one for this class of compounds.