We used Southern blot analysis and polymerase chain reaction-based techniques to examine deletions of tumour suppressor gene loci in 91 primary colorectal tumours. The tumour suppressor genes studied were MCC and APC on chromosome 5q, p53 on chromosome 17p, DCC on chromosome 18q, and the putative suppressor gene nm23-H1 on chromosome 17q. The most frequent allelic loss observed was in chromosome 17p with 76% ( 68 89 ) of informative tumours showing loss of heterozygosity at this locus, followed by 34% ( 19 55 ) for DCC, 31% ( 12 39 ) for MCC, 17% ( 9 53 ) for APC and 16% ( 3 19 ) for nm23. No significant differences in the frequency of these suppressor gene allelic losses were observed between Dukes B and C stage adenocarcinomas.
