Mouse model of proximal colon-specific tumorigenesis driven by microsatellite instability-induced Cre-mediated inactivation of Apc and activation of Kras
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KRAS gene mutations are found in 40–50 % of colorectal cancer cases, but their functional contribution is not fully understood. To address this issue, we generated genetically engineered mice with colon tumors expressing an oncogenic Kras G12D allele in the context of the Adenomatous polyposis coli (Apc) deficiency to compare them to tumors harboring Apc deficiency alone.
CDX2P9.5-G22Cre (referred to as G22Cre) mice showing inducible Cre recombinase transgene expression in the proximal colon controlled under the CDX2 gene promoter were intercrossed with Apc flox/flox mice and LSL-Kras G12D mice carrying loxP-flanked Apc and Lox–Stop–Lox oncogenic Kras G12D alleles, respectively, to generate G22Cre;Apc flox/flox ;Kras G12D and G22Cre;Apc flox/flox ;KrasWT mice. Gene expression profiles of the tumors were analyzed using high-density oligonucleotide arrays.
Morphologically, minimal difference in proximal colon tumor was observed between the two mouse models. Consistent with previous findings in vitro, Glut1 transcript and protein expression was up-regulated in the tumors of G22Cre;Apc flox/flox ;Kras G12D mice. Immunohistochemical staining analysis revealed that GLUT1 protein expression correlated with KRAS mutations in human colorectal cancer. Microarray analysis identified 11 candidate genes upregulated more than fivefold and quantitative PCR analysis confirmed that Aqp8, Ttr, Qpct, and Slc26a3 genes were upregulated 3.7- to 30.2-fold in tumors with mutant Kras.
These results demonstrated the validity of the G22Cre;Apc flox/flox ;Kras G12D mice as a new mouse model with oncogenic Kras activation. We believe that this model can facilitate efforts to define novel factors that contribute to the pathogenesis of human colorectal cancer with KRAS mutations.
KeywordsKras Glut1 Colorectal cancer
The author thanks Yuko Ishida and Midori Kiyokawa for their expert technical assistance. The author wishes to thank the Analysis Center of Life Science, Hiroshima University, for the use of their facilities. This work was supported by JSPS KAKENHI Grant-in-Aid for Scientific Research (B) Grant Number 22390257 (2010–2012) and 25293284 (2013–2016), The Japanese Society of Gastroenterology Grant-in-Aid 2010, and the Nakayama Cancer Research Institute Grant-in-Aid 2009 for Gastrointestinal disease.
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Conflict of interest
The authors declare that they have no conflict of interest.
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