Nonsteroidal anti-inflammatory drugs (NSAIDs) are prototypical anti-cancer agents. However, their long-term use is associated with adverse gastrointestinal effects. Recognition that endogenous gaseous mediators, nitric oxide (NO) and hydrogen sulfide (H2S) can increase mucosa] defense mechanisms has led to the development of NO- and H2S-releasing NSAIDs with increased safety profiles. Here we report on a new hybrid, NOSH-aspirin, which is an NO- and H2S-releasing agent. NOSH-aspirin inhibited HT-29 colon cancer growth with IC(50)s of 45.5 +/- 2.5, 19.7 +/- 3.3, and 7.7 +/- 2.2 nM at 24, 48, and 72 h, respectively. This is the first NSAID based agent with such high degree of potency. NOSH-aspirin inhibited cell proliferation, induced apoptosis, and caused G(0)/G(1) cell cycle block. Reconstitution and structure-activity studies representing a fairly close approximation to the intact molecule showed that NOSH-aspirin was 9000-fold more potent than the sum of its parts towards growth inhibition. NOSH-aspirin inhibited ovine COX-1 more than ovine COX-2. NOSH-ASA treatment of mice bearing a human colon cancer xenograft caused a reduction in volume of 85%. Taken together, these results demonstrate that NOSH-aspirin has strong anti-cancer potential and merits further evaluation. (C) 2012 Elsevier Inc. All rights reserved.