Kim Eunjoo, Davidson Laurie A, Zoh Roger S, Hensel Martha E, Salinas Michael L, Patil Bhimanagouda S, Jayaprakasha Guddadarangavvanahally K, Callaway Evelyn S, Allred Clinton D, Turner Nancy D, Weeks Brad R, Chapkin Robert S
Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, USA.
Department of Cellular and Molecular Medicine, Texas A&M Health Science Center, College Station, TX, USA.
Cell Death Dis. 2016 Nov 10;7(11):e2460. doi: 10.1038/cddis.2016.269.
The majority of colon tumors are driven by aberrant Wnt signaling in intestinal stem cells, which mediates an efficient route toward initiating intestinal cancer. Natural lipophilic polyphenols and long-chain polyunsaturated fatty acids (PUFAs) generally suppress Wnt- and NF-κB- (nuclear factor-κ light-chain enhancer of activated B-cell) related pathways. However, the effects of these extrinsic agents on colonic leucine-rich repeat-containing G-protein-coupled receptor 5-positive (Lgr5) stem cells, the cells of origin of colon cancer, have not been documented to date. Therefore, we examined the effect of n-3 PUFA and polyphenol (curcumin) combination on Lgr5 stem cells during tumor initiation and progression in the colon compared with an n-6 PUFA-enriched control diet. Lgr5-EGFP-IRES- knock-in mice were fed diets containing n-6 PUFA (control), n-3 PUFA, n-6 PUFA+curcumin or n-3 PUFA+curcumin for 3 weeks, followed by 6 azoxymethane (AOM) injections, and terminated 17 weeks after the last injection. To further elucidate the effects of the dietary bioactives at the tumor initiation stage, Lgr5 stem cells were also assessed at 12 and 24 h post AOM injection. Only n-3 PUFA+curcumin feeding reduced nuclear β-catenin in aberrant crypt foci (by threefold) compared with control at the progression time point. n-3 PUFA+curcumin synergistically increased targeted apoptosis in DNA-damaged Lgr5 stem cells by 4.5-fold compared with control at 12 h and maximally reduced damaged Lgr5 stem cells at 24 h, down to the level observed in saline-treated mice. Finally, RNAseq analysis indicated that p53 signaling in Lgr5 stem cells from mice exposed to AOM was uniquely upregulated only following n-3 PUFA+curcumin cotreatment. These novel findings demonstrate that Lgr5 stem cells are uniquely responsive to external dietary cues following the induction of DNA damage, providing a therapeutic strategy for eliminating damaged Lgr5 stem cells to reduce colon cancer initiation.
大多数结肠肿瘤是由肠道干细胞中异常的Wnt信号驱动的，该信号介导了引发结肠癌的有效途径。天然亲脂性多酚和长链多不饱和脂肪酸（PUFAs）通常会抑制与Wnt和NF-κB（活化B细胞的核因子κ轻链增强子）相关的信号通路。然而，这些外在因素对富含亮氨酸重复序列的G蛋白偶联受体5阳性（Lgr5）的结肠干细胞（即结肠癌的起源细胞）的影响，迄今为止尚未见报道。因此，我们研究了与富含n-6多不饱和脂肪酸的对照饮食相比，n-3多不饱和脂肪酸与多酚（姜黄素）组合在结肠癌起始和进展过程中对Lgr5干细胞的影响。给Lgr5-EGFP-IRES基因敲入小鼠喂食含n-6多不饱和脂肪酸（对照）、n-3多不饱和脂肪酸、n-6多不饱和脂肪酸+姜黄素或n-3多不饱和脂肪酸+姜黄素的饮食3周，随后进行6次氧化偶氮甲烷（AOM）注射，并在最后一次注射后17周处死。为了进一步阐明饮食生物活性物质在肿瘤起始阶段的作用，在AOM注射后12小时和24小时也对Lgr5干细胞进行了评估。与进展时间点的对照组相比，仅喂食n-3多不饱和脂肪酸+姜黄素可使异常隐窝病灶中的核β-连环蛋白减少（减少三倍）。与对照组相比，n-3多不饱和脂肪酸+姜黄素在12小时时协同使DNA损伤的Lgr5干细胞中的靶向凋亡增加4.5倍，并在24小时时最大程度地减少受损的Lgr5干细胞，降至盐水处理小鼠中观察到的水平。最后，RNA测序分析表明，仅在n-3多不饱和脂肪酸+姜黄素联合处理后，暴露于AOM的小鼠的Lgr5干细胞中的p53信号通路才独特地上调。这些新发现表明，Lgr5干细胞在DNA损伤诱导后对外部饮食线索具有独特的反应，为消除受损的Lgr5干细胞以减少结肠癌起始提供了一种治疗策略。
