Microsatellite analysis of the adenomatous polyposis coli (APC) gene and immunoexpression of β catenin in nephroblastoma:: a study including 83 cases treated with preoperative chemotherapy

Aims: To determine whether microsatellite mutations of the adenomatous polyposis coli (APC) gene have pathological or prognostic significance in nephroblastomas and to correlate APC alterations with beta catenin immunoexpression. Methods: One hundred nephroblastomas were analysed, 83 of which received preoperative chemotherapy. Normal and tumour DNA was isolated using standard proteinase K digestion and phenol/chloroform extraction from paraffin wax embedded tissue. Polymerase chain reaction using four APC microsatellite markers - D5S210, D5S299, D5S82, and D5S346 - was performed and the products analysed. Immunohistochemistry was performed using the LSAB kit with diaminobenzidine as chromogen. Results were correlated with clinicopathological data using the chi(2) test. Results: Allelic imbalance/loss of heterozygosity was more frequent than microsatellite instability, with 30% of cases showing allelic imbalance/loss of heterozygosity and 16% showing microsatellite instability. Although there was a significant correlation between the results for individual markers and the clinicopathological data, the overall results do not support a prognostic role for APC in nephroblastoma. Expression of beta catenin was seen in 93% of cases. Staining was predominantly membranous, with epithelium, blastema, and stroma being immunoreactive. Cytoplasmic redistribution was seen in 58% of cases, but no nuclear staining was detected. No significant associations between beta catenin expression and the clinicopathological parameters were found. Kaplan - Meier survival plots showed that patients with loss of membranous staining and pronounced cytoplasmic staining ( score, 3) had a significantly shorter survival ( p = 0.04; median survival, 5.87 months). Conclusion: Microsatellite analysis of APC and immunoexpression of beta catenin did not provide significant pathological or prognostic information in this cohort of nephroblastomas.