Rapidly cycling Lgr5 + stem cells are exquisitely sensitive to extrinsic dietary factors that modulate colon cancer risk

Cell Death Dis. 2016 Nov 10;7(11):e2460. doi: 10.1038/cddis.2016.269.

Abstract

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-creERT2 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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aberrant Crypt Foci / metabolism
  • Animals
  • Apoptosis / drug effects
  • Azoxymethane
  • Carcinogenesis / drug effects
  • Carcinogenesis / metabolism
  • Carcinogenesis / pathology
  • Carcinogens
  • Cell Cycle* / drug effects
  • Cell Differentiation / drug effects
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Chemoprevention
  • Colon / drug effects
  • Colon / metabolism
  • Colon / pathology
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology*
  • Curcumin / pharmacology
  • DNA Breaks, Double-Stranded / drug effects
  • DNA Modification Methylases / metabolism
  • DNA Repair Enzymes / metabolism
  • Diet*
  • Fatty Acids, Omega-3
  • Fish Oils / pharmacology
  • Green Fluorescent Proteins / metabolism
  • Mice
  • Receptors, G-Protein-Coupled / metabolism*
  • Regeneration / drug effects
  • Risk Factors
  • Signal Transduction / drug effects
  • Stem Cells / cytology*
  • Stem Cells / drug effects
  • Stem Cells / metabolism
  • Subcellular Fractions / drug effects
  • Subcellular Fractions / metabolism
  • Tumor Suppressor Protein p53 / metabolism
  • Tumor Suppressor Proteins / metabolism
  • beta Catenin / metabolism

Substances

  • Carcinogens
  • Fatty Acids, Omega-3
  • Fish Oils
  • Lgr5 protein, mouse
  • Receptors, G-Protein-Coupled
  • Tumor Suppressor Protein p53
  • Tumor Suppressor Proteins
  • beta Catenin
  • Green Fluorescent Proteins
  • DNA Modification Methylases
  • MGMT protein, mouse
  • DNA Repair Enzymes
  • Curcumin
  • Azoxymethane