Abstract 793: NOSH-aspirin and 5-fluorouracil demonstrate synergistic efficacy in a xenograft model of colon cancer

Abstract Introduction: Work in cancer biology, epidemiology and preclinical models has made it clear that non-steroidal anti-inflammatory drugs (NSAIDs) in general and aspirin in particular can significantly affect the development of several types of cancer, with colon cancer representing the best-studied case. However, NSAIDs have significant side effects that precludes there wide spread use. Notably, there are no chemotherapeutic applications for NSAIDs in humans or animals. In our search for a better NSAID, we developed NOSH-aspirin, a hybrid molecule that releases nitric oxide (NO) and hydrogen sulfide (H2S), two gasotransmitters of physiological relevance. Previously, we reported on the anti-inflammatory properties of NOSH-aspirin and showed that it was in the order of 100,000 to 250,000-fold more potent than aspirin in inhibiting colon cancer cell growth over a 24-72h-time period with negligible cyto-toxicity. Here we report on the effects of NOSH-aspirin alone and in combination with 5-fluorouracil (5-FU) on treatment of established tumors in a xenograft model of human colon cancer. Methods: NOSH-aspirin was synthesized and purified by us. Cell line: HT-29 human adenocarcimoma. Xenografts: Female nude mice (N=20) were implanted s.c. in the right flank with HT-29 (2 x 106) cells; when the tumor volumes reached 60-80 mm3, the animals were randomly divided into 4 groups (N=5/gp) and treated with NOSH-aspirin (po,100 mg/kg body wt/day), 5-FU (ip, 10 mg/kg x 2/week), NOSH-aspirin+5-FU as above, or vehicle (po). Tumor volume and animal weight were recorded every 3 days. After 3 weeks of treatment, mice were sacrificed, tumors excised, weighed, and fixed in 10% buffered formalin for IHC studies. We also weighed the livers and the kidneys. Results: In vitro, NOSH-aspirin and 5-FU inhibited the growth of HT-29 cells with IC50s of 48±3 and 20,000±2000 nM at 24 hr, respectively. In presence of 5-FU at 0.25x, 0.5x, and 1x it's IC50, the IC50s for NOSH-aspirin was reduced to 31±3, 15.5±2, and 0.75±0.2 nM, respectively. In vivo: NOSH-aspirin reduced tumor volume more than 5-FU as a function of time; however, the biggest reduction in tumor volume was in the combination group. Tumor mass at sacrifice in each group was, vehicle (3.2±0.62g), NOSH-aspirin (0.54±0.18g, 83% reduction, P<0.005), 5-FU (1.17±0.37g, 63% reduction, P<0.01), NOSH-aspirin+5-FU (0.17±0.056g reduction 87% reduction P<0.001). NOSH-aspirin had no effect on the weight of the mice whether alone or in combination with 5-FU, there were no overt signs of toxicity. There was a 10% reduction in the weight of animals in the 5-FU group, however, this difference was not statistically significant. There were no differences in liver or kidney masses amongst the groups. Conclusions: NOSH-aspirin has potent anti-cancer properties and demonstrates synergistic properties with 5-FU. It merits further evaluation as a chemotherapeutic agent. Citation Format: Clarissa J. Martinez, Mitali Chattopadhyay, Khosrow Kashfi. NOSH-aspirin and 5-fluorouracil demonstrate synergistic efficacy in a xenograft model of colon cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 793. doi:10.1158/1538-7445.AM2014-793