The cables gene on chromosome 18Q regulates colon cancer progression in vivo

Early events involved in the pathogenesis of colorectal cancer include mutations in the Adenomatous Polyposis Coli tumor-suppressor gene and oncogenic KRAS mutations. Later events include deletions on chromosome 18q, which are observed in a high proportion of colorectal cancers. However, the important tumor suppressor genes targeted by these deletions have not been fully defined. A previous study found Cables is located on human chromosome 18q11-12. Loss of Cables expression as determined by immunohistochemical staining (IHC) occurred in 60-70% of sporadic colorectal cancers that were usually correlated to loss of heterozygosity at 18q. To determine if Cables is an important target for the chromosome 18q deletions, the susceptibility of Cables(-/-) mice to develop colon tumors was studied. A well characterized colonic carcinogen, 1,2-dimethylhydrazine (DMH) was used as a tumor initiator. Cables(-/-) mice (n = 25) and the Cables(+/+) littermates (n = 25) were treated with subcutaneous DMH injections over 20 weeks to initiate tumorigenesis. The median survival after DMH injections was significantly shorter for the Cables(-/-) mice compared to Cables(+/+) littermates. The total number of colorectal tumors that developed in the Cables(-/-) mice was 46 tumors versus 21 tumors. The increased numbers of colorectal tumors, as well as shorter survival of the Cables(-/-) mice provides compelling evidence that Cables could play an important role in the pathogenesis and progression of colon cancer in mice. These data coupled with previous observations support the hypothesis that Cables is a relevant target of the chromosome 18q deletions frequently seen in human colorectal cancer.