Identification of early p53 mutations in clam ileocystoplasties using restriction site mutation assay.

Objectives Because a risk of cancer arising in enterocystoplasties exists, it is necessary to identify which patients are most at risk of tumor formation. The aim of this study was to determine whether rare mutated p53 sequences were more common at the enterovesical anastomosisthan in the bladder remnant in patients with a clam ileocystoplasty using the restriction sitemutation (RSM) assay. Methods DNA was extracted from endoscopic biopsies obtained from the ileovesical anastomosisand native bladder remnant (control specimens) of 38 patients with a clam ileocystoplasty. The RSM assay was used to study five known hotspots for mutations of the p53 gene using the restriction enzymes Hha I (codon 175), Taq I (codon 213), Hae III (codon 249/250), and Msp I (codons 248 and 282). The mutational events of p53 were confirmed by sequencing the undigested mutated polymerase chain reaction products identified by RSM analysis. Results We found p53 mutations at the ileovesical anastomosisin 7 of the 38 patients. The mutations were observed at codon 213 (n = 1), codon 248 (n = 3), and codon 250 (n = 3). No p53 mutations were detected in any control specimen. Conclusions The ileovesical anastomosisis genetically unstable in patients with a clam ileocystoplasty. The p53 mutations identified by the RSM assay at the enterovesical anastomosiscould possibly be used as markers of genetic instability to identify patients at risk of developing a tumor. Prospective, randomized longitudinal studies are required to substantiate this hypothesis.