title: Homeostatic responses of colonic LGR5+ stem cells following acute in vivo exposure to a genotoxic carcinogen.
abstract: Perturbations in DNA damage, DNA repair, apoptosis and cell proliferation in the base of the crypt where stem cells reside are associated with colorectal cancer (CRC) initiation and progression. Although the transformation of leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5)(+) cells is an extremely efficient route towards initiating small intestinal adenomas, the role of Lgr5(+) cells in CRC pathogenesis has not been well investigated. Therefore, we further characterized the properties of colonic Lgr5(+) cells compared to differentiated cells in Lgr5-EGFP-IRES-creER(T2) knock-in mice at the initiation stage of carcinogen azoxymethane (AOM)-induced tumorigenesis using a quantitative immunofluorescence microscopy approach. At 12 and 24h post-AOM treatment, colonic Lgr5(+) stem cells (GFP(high)) were preferentially damaged by carcinogen, exhibiting a 4.7-fold induction of apoptosis compared to differentiated (GFP(neg)) cells. Furthermore, with respect to DNA repair, O(6)-methylguanine DNA methyltransferase (MGMT) expression was preferentially induced (by 18.5-fold) in GFP(high) cells at 24h post-AOM treatment compared to GFP(neg) differentiated cells. This corresponded with a 4.3-fold increase in cell proliferation in GFP(high) cells. These data suggest that Lgr5(+) stem cells uniquely respond to alkylation-induced DNA damage by upregulating DNA damage repair, apoptosis and cell proliferation compared to differentiated cells in order to maintain genomic integrity. These findings highlight the mechanisms by which colonic Lgr5(+) stem cells respond to cancer-causing environmental factors.
authors.affiliation: Program in Integrative Nutrition and Complex Diseases, Cellular and Molecular Medicine, Texas A&M Health Science Center.
authors.forename: Eunjoo
authors.initials: E
authors.lastname: Kim
authors.affiliation: Program in Integrative Nutrition and Complex Diseases, Department of Nutrition and Food Science.
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Davidson
authors.affiliation: Program in Integrative Nutrition and Complex Diseases, Department of Statistics.
authors.forename: Roger S
authors.initials: RS
authors.lastname: Zoh
authors.affiliation: Department of Veterinary Pathobiology and.
authors.forename: Martha E
authors.initials: ME
authors.lastname: Hensel
authors.affiliation: Vegetable Crop Improvement Center, Texas A&M University, College Station, TX, USA.
authors.forename: Bhimanagouda S
authors.initials: BS
authors.lastname: Patil
authors.affiliation: Vegetable Crop Improvement Center, Texas A&M University, College Station, TX, USA.
authors.forename: Guddadarangavvanahally K
authors.initials: GK
authors.lastname: Jayaprakasha
authors.affiliation: Program in Integrative Nutrition and Complex Diseases, Department of Nutrition and Food Science.
authors.forename: Evelyn S
authors.initials: ES
authors.lastname: Callaway
authors.affiliation: Department of Nutrition and Food Science.
authors.forename: Clinton D
authors.initials: CD
authors.lastname: Allred
authors.affiliation: Department of Nutrition and Food Science, Vegetable Crop Improvement Center, Texas A&M University, College Station, TX, USA.
authors.forename: Nancy D
authors.initials: ND
authors.lastname: Turner
authors.affiliation: Department of Veterinary Pathobiology and.
authors.forename: Brad R
authors.initials: BR
authors.lastname: Weeks
authors.affiliation: Program in Integrative Nutrition and Complex Diseases, Department of Nutrition and Food Science, Vegetable Crop Improvement Center, Texas A&M University, College Station, TX, USA r-chapkin@tamu.edu.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Chapkin
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002273:Carcinogens / Q000633:toxicity; D049109:Cell Proliferation / Q000187:drug effects / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D015179:Colorectal Neoplasms / Q000473:pathology / Q000503:physiopathology; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology; D004260:DNA Repair / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D055879:Gene Knock-In Techniques; D006706:Homeostasis / Q000187:drug effects* / Q000502:physiology; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects / Q000473:pathology; D051379:Mice; D009153:Mutagens / Q000633:toxicity; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D013234:Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology
chemical_list: D002273:Carcinogens; C493597:Lgr5 protein, mouse; D009153:Mutagens; D043562:Receptors, G-Protein-Coupled