Colorectal tumourigenesis in carriers of the APC I1307K variant: lone gunman or conspiracy?
Sieber O., Lipton L., Heinimann K., Tomlinson I.
The APC I1307K allele is believed to predispose to multiple colorectal tumours because the change at the nucleotide level-A(3)TA(4) to A(8)-creates a hypermutable site. Slippage of the A(8) tract undoubtedly occurs more often than expected in the tumours of I1307K carriers, but many of these tumours do not harbour changes at this site. Outside the A(8) tract, the tumours of I1307K carriers appear to harbour fewer somatic frameshift mutations than expected. There is inconsistent evidence as to whether or not I1307K confers an increased risk of colorectal cancer. Most I1307K patients and families who have undergone analysis of somatic APC mutations have been highly selected. It is therefore possible that many APC I1307K carriers with multiple adenomas have a susceptibility to tumours additional to that resulting from the A(8) tract.