Effect of EI24 expression on the tumorigenesis of ApcMin/+ colorectal cancer mouse model

Etoposide-induced 2.4 kb transcript (EI24, also known as PIG8) is a p53 target gene involved in cell growth suppression and apoptosis and known to be frequently altered in human cancers. Although EI24 expression is decreased in various cancers and is associated with colorectal cancer progression and metastasis, the physiological function of EI24 in colorectal cancer is yet unclear. We generated an Ei24 conditional transgenic (Tg) mouse to study the therapeutic effects of Ei24 in vivo and evaluated whether Ei24 plays a role of a tumor suppressor using Ei24 Tg mouse crossed with Apc^Min/+ mouse, which develops multiple intestinal adenomas. The overexpression of Ei24 failed to cause any notable difference in the number of polyps, lengths of the intestine and spleen, and survival rate between Apc^Min/+ and Apc^Min/+Ei24 Tg mice. Ei24 plays no significant role in colon cancer caused by the substitutional mutation of Apc in mice. Therefore, our result dismisses the hypothesized direct link between Apc^Min/+ mutation and Ei24 expression in colorectal cancer model.

Dual gene deficient models of ApcMin/+ mouse in assessing molecular mechanisms of intestinal carcinogenesis

The Apc^Min/+ mouse, carrying an inactivated allele of the adenomatous polyposis coli (Apc) gene, is a widely used animal model of human colorectal tumorigenesis. While crossed with other gene knockout or knock-in mice, these mice possess advantages in investigation of human intestinal tumorigenesis. Intestinal tumor pathogenesis involves multiple gene alterations; thus, various double gene deficiency models could provide novel insights into molecular mechanisms of tumor biology, as well as gene-gene interactions involved in intestinal tumor development and assessment of novel strategies for preventing and treating intestinal cancer. This review discusses approximately 100 double gene deficient mice and their associated intestinal tumor development and progression phenotypes. The dual gene knockouts based on the Apc mutation background consist of inflammation and immune-related, cell cycle-related, Wnt/β-catenin signaling-related, tumor growth factor (TGF)-signaling-related, drug metabolism-related, and transcription factor genes, as well as some oncogenes and tumor suppressors. Future studies should focus on conditional or inducible dual or multiple mouse gene knockout models to investigate the molecular mechanisms underlying intestinal tumor development, as well as potential drug targets.