Abstract
It is generally accepted that both dysfunction of the Wnt signaling pathway, including mutations in the adenomatous polyposis coli (APC) and Ξ²βcatenin genes, and genetic instability play important roles in colorectal carcinogenesis. However, alteration of the components in the Wnt signaling pathway in colorectal cancer (CRC) with microsatellite instability (MSI) has not been elucidated. In order to assess the status of the Wnt signaling components in CRC with MSI, mutational analyses of the Ξ²βcatenin, APC, Axin 1, and T cell factor 4 (TCF4) genes were performed. Three of 33 samples had mutations in exon 3 of the Ξ²βcatenin gene and two in the APC gene. Eight mutations in seven samples were detected by singleβstrand conformation polymorphism and subsequent direct sequence analysis of the entire coding region of the Axin 1 gene. Furthermore, TCF4, which is one of the transcriptional factors in the Wnt signaling pathway and has a mononucleotide repeat sequence (a nineβ adenine repeat, (A)9) in its Cβterminal region, was mutated in 13 of the 33 samples. Thus, alteration in the Wnt signaling pathway is frequently observed in CRC with MSI, including hereditary nonpolyposis colorectal cancer, as well as in familial adenomatous polyposis and sporadic CRC without MSI. Β© 2002 WileyβLiss, Inc.