Microsatellite analysis of the DCC gene in nephroblastomas: pathologic correlations and prognostic implications

Microsatellite instability has been reported in a wide variety of cancer types. Inactivation or loss of tumour suppressor genes has been shown to result in cell cycle deregulation and neoplastic growth. We conducted a microsatellite study using fluorescent-based DNA technology to determine whether mutations in the microsatellite sequences of the deleted in colorectal cancer (DCC) gene, a tumour suppressor at 18q21.1, have any pathologic correlation or prognostic significance in nephroblastomas. Normal and tumour DNA was isolated from 106 cases of nephroblastoma using the standard proteinase K digestion and phenol-chloroform extraction method from paraffin wax-embedded tissue. Polymerase chain reaction using three microsatellite markers; D18S21, D18S34 and D18S58, for the DCC gene were performed. The polymerase chain reaction products were analysed on the ALF Express Automated DNA sequencer. The results were correlated with age at diagnosis, preoperative chemotherapy, clinicopathological stage, histological classification and patient outcome using chi(2) test. Allelic imbalance/loss of heterozygosity appeared to be a more frequent genetic aberration than microsatellite instability with 20% of cases showing allelic imbalance/loss of heterozygosity and only 9% of cases showing microsatellite instability. Genetic aberrations were more frequent in unfavourable histology tumours compared to favourable histology tumours (P=0.012). All patients with genetic aberrations for more than one DCC marker died independent of histological classification and stage (P=0.016). There was no statistically significant difference when DCC aberrations were compared with age at diagnosis, preoperative chemotherapy and clinicopathological stage. In conclusion, this study has found that multiple aberrations involving the DCC locus may play a role in the progression of nephroblastomas, and hence confer a poorer prognosis.