P09 Therapeutic potential of NOSH-aspirin, a dual nitric oxide- and hydrogen sulfide-donating hybrid in colon cancer

Abstract

Colorectal cancer is one of the major causes of cancer deaths worldwide. In patients with advanced disease, the efficacy of currently available treatments is limited. Nonsteroidal anti-inflammatory drugs (NSAIDs) in general and aspirin (ASA) in particular are prototypical chemopreventive agents. However, the use of NSAIDs is limited by their significant toxicity (gastrointestinal, renal, and cardiovascular). In our search for a “better NSAID”, we have developed NOSH-aspirin for the treatment of colon cancer. The notion that a modified NSAID maybe used to treat cancer is radical. NOSH-aspirin (NBS-1120) is a hybrid molecule that releases nitric oxide (NO) and hydrogen sulfide (H 2 S), two gasotransmitters of physiological relevance. NOSH-aspirin is the first NSAID-based agent that is active against colon cancer in the nano-molar range, is devoid of gastrointestinal and cellular toxicity, preferentially affects cancer cells compared to normal cells, and has a pleotropic mechanism of action. In vitro, NOSH-aspirin inhibited the growth of HT-29, HCT 15, and SW480 human colon cancer cell lines with IC 50 values of 48 ± 3, 50 ± 5, and 60 ± 4 nM at 24 h, respectively. The corresponding IC 50 for aspirin in all 3 cell lines was > 5,000,000 nM. This represents an enhanced potency of > 80,000-fold in the 3 cell lines at 24 h. Using HT-29 colon cancer cells, NOSH-aspirin had IC 50 s for cell growth inhibition of 20 nM at 48 h and 8 nM at 72 h. The corresponding values for aspirin were, 2,500,000 nM and 2,000,000 nM, respectively. This represents potency enhancements of ∼125–000-fold and ∼250,000-fold. Although highly potent, NOSH-aspirin was without any cytotoxicity as determined by lactate dehydrogenase release. Inhibiting NO and H 2 S release from NOSH-aspirin, increased the IC 50 for cell growth inhibition to ∼800,000 nM at 24 h. NOSH-aspirin had a synergistic effect with 5-flurouracil (5-FU), in HT-29 cells its IC 50 for cell growth inhibition at 24 h went down from 50 nM to 4 nM in presence of sub-toxic levels of 5-FU. Mechanistically, NOSH-aspirin dose-dependently induced apoptosis; inhibited proliferation; caused a G 0 /G 1 cell cycle block; increased reactive oxygen species (ROS); inhibited NF-#kappa B, regulating it by reciprocal S-nitrosylation and S-sulfhydration; and inhibited cytokine-induced NOS2 expression. In vivo, using a xenograft model of colon cancer, NOSH-aspirin dose-dependently reduced the growth of established tumors, reduced proliferation, induced apoptosis, reduced NF-#kappa B, and induced ROS. NOSH-aspirin also exhibited potent anti-inflammatory properties, inhibiting both cyclo-oxygense (COX)-1 and COX-2, thus reducing prostaglandin (PG) E 2 levels in a carrageenan-induced rat paw edema model. In conclusion, NOSH-aspirin is a promising candidate against cancer modulating key parameters that regulate cellular mass.