A transposon-based genetic screen in mice identifies genes altered in colorectal cancer

Abstract

Human colorectal cancers (CRCs) display a large number of genetic and epigenetic alterations, some of which are causally involved in tumorigenesis (drivers) and others that have little functional impact (passengers). To help distinguish between these two classes of alterations, we used a transposon-based genetic screen in mice to identify candidate genes for CRC. Mice harboring mutagenic Sleeping Beauty (SB) transposons were crossed with mice expressing SB transposase in gastrointestinal tract epithelium. Most of the offspring developed intestinal lesions, including intraepithelial neoplasia, adenomas, and adenocarcinomas. Analysis of over 16,000 transposon insertions identified 77 candidate CRC genes, 60 of which are mutated and/or dysregulated in human CRC and thus are most likely to drive tumorigenesis. These genes include APC, PTEN, and SMAD4. The screen also identified 17 candidate genes that had not previously been implicated in CRC, including POLI, PTPRK, and RSPO2.

Fig. 1

Triple transgenic mice develop intestinal tumors and become moribund faster than double transgenic controls. (A) Breeding scheme for generating triple transgenics. (B) Kaplan-Meier Survival curve comparing triple transgenics to double transgenic controls. Photomicrographs of hematoxylin and eosin stained representative tissue showing an adenoma (C), an adenocarcinoma (D) with arrow pointing to a cluster of glands that has invaded through the serosa, and gastrointestinal intraepithelial neoplasia (E) with arrow indicating a cluster of dysplastic glands accompanied by fusion of villi. Vil = Villin promoter, RLS = Rosa26-Lox-stop-Lox-Sleeping Beauty 11, Tg = Transgenic, bars = 250 µm (C), 500 µm (D), and 100 µm (E).