Introduction: Colorectal cancer (CRC) represents one of the most common malignancies in the United States. The pathological progression from adenoma to carcinoma is accompanied by distinct and reproducible genetic alterations. Here we present a novel mouse model system for the sequential steps of tumorigenesis. This system will be helpful for functional validation of novel therapeutic targets in CRC.

Purpose: The aim of this study is to delineate the stage-specific genomic alterations and transcriptional deregulation that are associated with the spontaneous progression of normal murine colon epithelial cells to immortalized, transformed, and eventually tumorigenic cell lines.

Methods: Normal epithelial colon cells were selectively isolated from the large intestine from eight different isogenic five-six week old C57BL/6 mice. Primary colon cells were grown with reduced serum concentration while a fraction of these normal cells were cryopreserved for further analysis. The cells were sequentially recovered from culture based on distinct morphological changes: first, when the cells were in the pre-immortal stage as cells were actively growing; second, as the cells bypassed crisis, formed colonies and became immortal; third, at early transformation, as the cells first formed foci; fourth, mid-transformed (higher proliferation rates, later passages); and finally, as cells became less adherent, and exhibiting multiple foci. The cells were then analyzed using molecular cytogenetic methods (SKY and arrayCGH), and using global gene expression profiling.

Results: Using Spectral Karyotyping (SKY) we identified clonal chromosomal aberrations and recurrent chromosome imbalances, specifically reported here for late transformed cells and in tumor cells. Array CGH (aCGH) demonstrated a specific pattern of whole chromosome copy number gains (i.e. MMU10 and MMU15 which contain Mdm2 and Myc, respectively) and losses (ex. MMU4 which contains tumor suppressor gene p16/Ink4a/Cdkn2a) at the various stages of cellular transformation. Gene expression microarray identified the deregulation of specific genes that defined genomic signatures at each stage of transformation. Two of the eight late transformed cell lines gave rise to tumors in a nude mouse assay.

Conclusion: We present a novel mouse model of CRC that recapitulates the sequential steps of human colorectal tumorigenesis which affords us the possibility to experimentally test potential rational intervention strategies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 321.