The Combination of Curcumin and Salsalate is Superior to Either Agent Alone in Suppressing Pro-Cancerous Molecular Pathways and Colorectal Tumorigenesis in Obese Mice

Scope: High-fat diets (HFDs) and adiposity increase colorectal cancer risk, in part by elevating pro-inflammatory cytokines that activate pro-cancerous signaling pathways. Curcumin (CUR), a dietary polyphenol and salsalate (SAL), an non-steroidal anti-inflammatory drug (NSAID) lacking the gastrotoxicity of aspirin, each suppress inflammatory signaling, but via different cellular pathways. Methods and results: A/J mice (n = 110) are fed a low-fat diet (LFD, 10% kcal), a HFD (60% kcal), a HFD containing 0.4% CUR, a HFD containing 0.3% SAL, or a HFD containing both agents (CUR/SAL). All mice receive six injections of azoxymethane. Compared to LFD-fed mice, HFD-fed mice display elevated colonic cytokines, crypt cell proliferation, and increased tumorigenesis (p < 0.05). CUR/SAL significantly reduces colonic cytokines (p < 0.01), suppresses activation of the PI3K/Akt/mTOR/NF-κB/Wnt pathways (p < 0.01), activates AMPK (p < 0.01), attenuates abnormal proliferation of the colonic mucosa (p < 0.05), and reduces tumor multiplicity and burden (p < 0.05), in comparison to the HFD control. In contrast, CUR or SAL alone does not suppress abnormal crypt cell proliferation or tumor multiplicity, and is largely ineffective in modifying activation of these signaling pathways. Conclusion: These observations demonstrate the superiority of the CUR/SAL over the individual agents and provide a scientific basis for future translational studies in obese subjects and/or those habitually consuming HFDs.