Abstract 3891: NOSH-aspirin, a novel nitric oxide- and hydrogen sulfide-releasing hybrid, is a potent inhibitor of colon cancer cell growth

Abstract

Abstract Introduction: Non-steroidal anti-inflammatory drugs (NSAIDs) are recognized as the prototypical chemopreventive agents. However, their wide use is precluded due to significant toxicity. The search for better NSAIDs has led to generation of nitric oxide-releasing NSAIDs (NO-NSAIDs) and more recently, to a new class of hydrogen sulfide-releasing agents (HS-NSAIDs). Both of these have shown to be more potent and less toxic than their parent NSAID. However, the draw back to these compounds is their IC50 for cell growth inhibition. It is too high to make them attractive for development as pharmaceuticals. Therefore, we postulated that a new hybrid that incorporated the active parts of each compound may be more potent and effective than either one. Our hypothesis has proved to be correct. Here we describe the effects of a nitric oxide- and hydrogen sulfide-releasing aspirin (NOSH-aspirin) on the growth properties of several human colon cancer cell lines, on induction of reactive oxygen species (ROS), and on NF-κB whose induction is strongly implicated in some cancers. Methods: NOSH-aspirin was synthesized and purified at our lab with 1H-NMR verification. Colon cancer cell lines: HT-29, HCT 15, and SW480; Cell growth: MTT; Cell cycle phase distribution: Flow cytometry; Apoptosis: subdiploid (sub-G0/G1) peak in DNA content histograms; Proliferation: PCNA; NF-kB: enzyme-linked immunosorbent assay (ELISA); Reactive oxygen species (ROS): 2′,7′-dichlorodihydrofluorescein (H2DCFDA, probe for peroxides) or dihydroethidium (DHE, probe for superoxide anion) measured fluorescence by flow cytometry. Results: NOSH-aspirin inhibited the growth of HT-29, HCT 15, and SW480 cells with IC50 values of 48 ± 3, 50 ± 5, and 60 ± 4 nM at 24 hr, respectively. The corresponding IC50 for aspirin in all 3 cell lines was >5000 µM. This represents and enhanced potency of >80,000-fold in the 3 cell lines at 24 h. NOSH-aspirin treatment of HT-29 cells at 0.5xIC50, 1xIC50, and 2xIC50 for 24 hrs induced apoptosis (20 ± 1%, 52 ± 3%, 75 ± 3%), inhibited proliferation (PCNA, 70 ± 3%, 45 ± 4%, 22 ± 3%), and caused a G0/G1 cell cycle block. Activation of NF-κB was inhibited as demonstrated by ELISA, at 0.5xIC50, 1xIC50, and 2xIC50 the reduction was 11 ± 1%, 33 ± 2%, and 46 ± 3% respectively. NOSH-aspirin caused induction of oxidative stress as evidenced by increases in both H2DCFDA and DHE-derived fluorescence representing increases in intracellular levels of H2O2 and superoxide anion respectively Conclusions: NOSH-aspirin by inducing ROS is a potent inhibitor of colon cancer cell growth and it inhibits NF-κB activation. These data suggest that NOSH-aspirin may be useful as a chemopreventive agent against colon cancer and merits further evaluation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3891. doi:1538-7445.AM2012-3891