Carcinogenesis Advance Access published online on January 16, 2004
Carcinogenesis, doi:10.1093/carcin/bgh062
© 2004 by Oxford University Press
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CARCINOGENESIS
1 Department of Surgery, Cancer Centre, Queen's University Belfast, Belfast BT12 6BJ, Northern Ireland
* Corresponding author. E-mail: F.C.Campbell{at}qub.ac.uk.
Received 5 October 2003
; revised 9 December 2003
; accepted 12 December 2003
Red meat consumption is associated with endogenous metabolic generation of mutagenic N-nitroso compounds (NOC) and may be implicated in causation of colorectal cancer (CRC). Assessment of a biologically relevant dose of NOCs is hampered by imperfect understanding of NOC interactions with other dietary components. This study tests the hypothesis that NOC effects upon mutational biomarkers in mouse colon may be modulated by a non-genotoxic diet related compound. N-methyl-N-nitrosourea (MNU) and undegraded lambda carrageenan (
Modulation of N-methyl-N-nitrosourea (MNU) induced crypt restricted metallothionein (MT) immunopositivity in mouse colon by a non-genotoxic diet related chemical
2 Strangeways Research Laboratories, Worts Causeway, Cambridge, CB1 8RN, UK
3 Department of Pathology, Cancer Centre, Queen's University Belfast, Belfast BT12 6BJ, Northern Ireland
4 Department of Epidemiology, Cancer Centre, Queen's University Belfast, Belfast BT12 6BJ, Northern Ireland
5 Section of Molecular Carcinogenesis, Institute of Cancer Research, Brookes Lawley Building, Cotswold Rd, Sutton, Surrey, SM2 5NG, UK
CgN) were selected as test chemicals, representing a NOC and a nongenotoxic agent respectively. Study endpoints included (i) DNA adduct formation and (ii) MT crypt restricted immunopositivity indices (MTCRII) which are considered representative of crypt stem cell mutations. Frequency and size of metallothionein (MT) immunopositive foci as well as total number of MT immunopositive crypts were assessed. Biologically effective doses of MNU and
CgN were determined in model validation studies and the agents were then tested alone and in combination. Continuous
CgN treatment for 10 weeks induced significantly greater colonic mucosal injury than drinking water control. In combined treatment regimens,
CgN treatment did not significantly affect MNU-induced DNA adduct formation. However, combinations of
CgN with MNU significantly increased MTCRII in excess of those induced by MNU alone. Recurrent or continuous
CgN regimens had greater interactive effects with MNU upon MTCRII, than short-term
CgN treatment. This study has shown that exposure to a non-genotoxic diet-related compound (
CgN) modulates the effective NOC dosimetry for induction of MT crypt restricted immunopositivity.![]()
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