title: Low levels of GSTA1 expression are required for Caco-2 cell proliferation.
abstract: The colonic epithelium continuously regenerates with transitions through various cellular phases including proliferation, differentiation and cell death via apoptosis. Human colonic adenocarcinoma (Caco-2) cells in culture undergo spontaneous differentiation into mature enterocytes in association with progressive increases in expression of glutathione S-transferase alpha-1 (GSTA1). We hypothesize that GSTA1 plays a functional role in controlling proliferation, differentiation and apoptosis in Caco-2 cells. We demonstrate increased GSTA1 levels associated with decreased proliferation and increased expression of differentiation markers alkaline phosphatase, villin, dipeptidyl peptidase-4 and E-cadherin in postconfluent Caco-2 cells. Results of MTS assays, BrdU incorporation and flow cytometry indicate that forced expression of GSTA1 significantly reduces cellular proliferation and siRNA-mediated down-regulation of GSTA1 significantly increases cells in S-phase and associated cell proliferation. Sodium butyrate (NaB) at a concentration of 1 mM reduces Caco-2 cell proliferation, increases differentiation and increases GSTA1 activity 4-fold by 72 hours. In contrast, 10 mM NaB causes significant toxicity in preconfluent cells via apoptosis through caspase-3 activation with reduced GSTA1 activity. However, GSTA1 down-regulation by siRNA does not alter NaB-induced differentiation or apoptosis in Caco-2 cells. While 10 mM NaB causes GSTA1-JNK complex dissociation, phosphorylation of JNK is not altered. These findings suggest that GSTA1 levels may play a role in modulating enterocyte proliferation but do not influence differentiation or apoptosis.
authors.affiliation: Department of Biomedical Sciences, University of Guelph, Ontario, Canada.
authors.forename: Humaira
authors.initials: H
authors.lastname: Adnan
authors.forename: Holly
authors.initials: H
authors.lastname: Quach
authors.forename: Kimberley
authors.initials: K
authors.lastname: MacIntosh
authors.forename: Monica
authors.initials: M
authors.lastname: Antenos
authors.forename: Gordon M
authors.initials: GM
authors.lastname: Kirby
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D002087:Butyrates / Q000494:pharmacology; D018938:Caco-2 Cells; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005982:Glutathione Transferase / Q000494:pharmacology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D016196:S Phase / Q000187:drug effects; D014162:Transfection
chemical_list: D002087:Butyrates; C484555:GSTA1 protein, human; D005982:Glutathione Transferase; D048031:JNK Mitogen-Activated Protein Kinases; D000469:Alkaline Phosphatase