Xingmin Wang1, Mark M Huycke. 1. The Muchmore Laboratories for Infectious Disease Research, Department of Veterans Affairs Medical Center, University of Oklahoma Health Sciences Center, Oklahoma City, USA.
Abstract
BACKGROUND & AIMS: We investigated whether Enterococcus faecalis, a Gram-positive intestinal commensal that produces extracellular superoxide, could promote chromosomal instability (CIN) in mammalian cells. METHODS: We measured the ability of E faecalis to promote CIN using hybrid hamster cells (A(L)N) containing human chromosome 11. RESULTS: E faecalis promoted CIN in A(L)N cells with average mutant fractions per 10(5) survivors (+/-SD) of 72.3 +/- 6.7 at 1 x 10(9) cfu mL(-1) compared with 22.2 degrees +/- 4.5 for the no bacteria control. Gamma-irradiation at 2 Gray similarly resulted in 74.7 +/- 5.7 mutant clones per 10(5) survivors. Deletions in chromosome 11 consistent with CIN were verified in 80% of mutant clones. E faecalis-treated A(L)N cells were protected from CIN by superoxide dismutase, gamma-tocopherol, and cyclooxygenase-2 (COX-2) inhibitors. In a dual-chamber tissue culture model designed to mimic stromal-epithelial cell interactions, macrophages pretreated with E faecalis grown on permeable supports increased mutant fractions 2.5-fold for A(L)N cells. COX-2 was up-regulated by superoxide from E faecalis and mutant fractions decreased when COX-2 was silenced using short interfering RNA. Escherichia coli, a Gram-negative commensal that produces negligible extracellular superoxide, only modestly promoted CIN in this model. CONCLUSIONS: These findings indicate that macrophage COX-2 is induced by superoxide from E faecalis and promotes CIN in mammalian cells through diffusible factors. This mechanism links the oxidative physiology of E faecalis to propagation of genomic instability through a bystander effect, and offers a novel theory for the role of commensal bacteria in the etiology of sporadic colorectal cancer.
BACKGROUND & AIMS: We investigated whether Enterococcus faecalis, a Gram-positive intestinal commensal that produces extracellular superoxide, could promote chromosomal instability (CIN) in mammalian cells. METHODS: We measured the ability of E faecalis to promote CIN using hybrid hamster cells (A(L)N) containing human chromosome 11. RESULTS: E faecalis promoted CIN in A(L)N cells with average mutant fractions per 10(5) survivors (+/-SD) of 72.3 +/- 6.7 at 1 x 10(9) cfu mL(-1) compared with 22.2 degrees +/- 4.5 for the no bacteria control. Gamma-irradiation at 2 Gray similarly resulted in 74.7 +/- 5.7 mutant clones per 10(5) survivors. Deletions in chromosome 11 consistent with CIN were verified in 80% of mutant clones. E faecalis-treated A(L)N cells were protected from CIN by superoxide dismutase, gamma-tocopherol, and cyclooxygenase-2 (COX-2) inhibitors. In a dual-chamber tissue culture model designed to mimic stromal-epithelial cell interactions, macrophages pretreated with E faecalis grown on permeable supports increased mutant fractions 2.5-fold for A(L)N cells. COX-2 was up-regulated by superoxide from E faecalis and mutant fractions decreased when COX-2 was silenced using short interfering RNA. Escherichia coli, a Gram-negative commensal that produces negligible extracellular superoxide, only modestly promoted CIN in this model. CONCLUSIONS: These findings indicate that macrophage COX-2 is induced by superoxide from E faecalis and promotes CIN in mammalian cells through diffusible factors. This mechanism links the oxidative physiology of E faecalis to propagation of genomic instability through a bystander effect, and offers a novel theory for the role of commensal bacteria in the etiology of sporadic colorectal cancer.
Authors: Gabriel Cuevas-Ramos; Claude R Petit; Ingrid Marcq; Michèle Boury; Eric Oswald; Jean-Philippe Nougayrède Journal: Proc Natl Acad Sci U S A Date: 2010-06-07 Impact factor: 11.205
Authors: Xingmin Wang; Toby D Allen; Randal J May; Stanley Lightfoot; Courtney W Houchen; Mark M Huycke Journal: Cancer Res Date: 2008-12-01 Impact factor: 12.701