Familial adenomatous polyposis (FAP) is a rare autosomal-inherited disease that highly predisposes to colorectal cancer, characterized by a diffuse duodenal and colorectal polyposis associated with various extradigestive tumors and linked to germline mutations within the APC gene.
However, the remaining 13 (37%) hypermutated CRCs lacked MLH1 silencing, contained tumours with the highest mutation rates ('ultramutated' CRCs), and exhibited higher incidences of APC and KRAS mutations, but infrequent BRAF mutations.
In addition, we have partially transformed the HCEC 1CT line by introducing stable knockdown of wild type APC and TP53, and ectopically introducing a mutant Krasv12 and a mutant version of APC (A1309), all commonly found mutations in colorectal cancer (CRC).
We found that BCL9 is required for efficient beta-catenin-mediated transcription in Wnt-stimulated HEK 293 cells, and in the SW480 colorectal cancer cell line whose Wnt pathway is active due to APC mutation.
A low-penetrance susceptibility allele that is common in Jews from Eastern Europe, APC 11307K, confers a two-fold increased risk of colorectal cancer without the full expression of familial adenomatous polyposis.
AXIN2 and MUTYH genes were screened for germline mutations by PCR and direct sequencing in 39 unrelated patients with multiple adenomas or colorectal cancer without evidence of APC mutation nor mismatch repair defect.
There is increasing evidence that there exist germ-line variants of the APC gene that predispose to the development of multiple colorectal adenomas and carcinoma, but without the florid phenotype of classical FAP, and possibly with importance for colorectal cancer risk in the general population.
Hereditary predisposition to colorectal cancer most often manifests itself as familial adenomatous polyposis from mutations of APC, or hereditary nonpolyposis colorectal cancer, resulting from mutations of MSH2, MLH1, MSH6, or other genes.