An Msh2 Conditional Knockout Mouse for Studying Intestinal Cancer and Testing Anticancer Agents
Received 21 August 2009; accepted 10 November 2009. published online 19 November 2009. Uncorrected Proof
Background & Aims
Mutations in the DNA mismatch repair (MMR) gene MSH2 cause Lynch syndromes I and II and sporadic colorectal cancers. Msh2null mice predominantly develop lymphoma and do not accurately recapitulate the colorectal cancer phenotype.
Methods
We generated and examined mice with a conditional Msh2 disruption (Msh2LoxP), permitting tissue-specific gene inactivation. ECMsh2LoxP/LoxP mice carried an EIIa-Cre transgene, and VCMsh2LoxP/LoxP mice carried a Villin-Cre transgene. We combined the VCMsh2LoxP allele with either Msh2Δ7null (VCMsh2LoxP/null) or Msh2G674D mutations (VCMsh2LoxP/G674D) to create allelic phase mutants. These mice were given cisplatin or 5-fluorouracil/leucovorin and oxaliplatin (FOLFOX), and their tumors were measured by magnetic resonance imaging.
Results
Embryonic fibroblasts from ECMsh2LoxP/LoxP mice do not express MSH2 and are MMR deficient. Reverse transcription, polymerase chain reaction, and immunohistochemistry from VCMsh2LoxP/LoxP mice demonstrated specific loss of Msh2 messenger RNA and protein from epithelial cells of the intestinal tract. Microsatellite instability was observed in all VCMsh2 strains and limited to the intestinal mucosa. Resulting adenomas and adenocarcinomas had somatic Apc truncation mutations. VCMsh2LoxP/LoxP mice did not develop lymphoma. Comparison of allelic phase tumors revealed significant differences in multiplicity and size. When treated with cisplatin or FOLFOX, tumor size was reduced in VCMsh2LoxP/G674D but not VCMsh2LoxP/null tumors. The apoptotic response to FOLFOX was partially sustained in the intestinal mucosa of VCMsh2LoxP/G674D animals.
Conclusions
Msh2LoxP/LoxP mice in combination with appropriate Cre recombinase transgenes have excellent potential for preclinical modeling of Lynch syndrome, MMR-deficient tumors of other tissue types, and use in drug development.
⁎Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
‡Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York
§Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, North Carolina
∥Laboratory of Structural Biology, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, North Carolina
¶Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx
#Strang Cancer Research Laboratory, Department of Medicine (Gastroenterology), Weill Medical Center of Cornell University, New York, New York
⁎⁎Rodent Histopathology Core, Harvard Medical School, Boston
‡‡Department of Pathology, Tufts University Schools of Medicine and Veterinary Medicine, Boston, Massachusetts
Reprint requests Address requests for reprints to: Melanie Kucherlapati, PhD, Department of Medicine/Division of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115. or Winfried Edelmann, PhD, Department of Cell Biology, Albert Einstein College of Medicine, 1301 Morris Park Ave, Bronx, New York 10461
Conflicts of interest The authors disclose no conflicts.
ABSTRACT