LOSS OF HETEROZYGOSITY ON CHROMOSOME 18Q IS ASSOCIATED WITH MUSCLE-INVASIVE TRANSITIONAL-CELL CARCINOMA OF THE BLADDER

Somatic allelic loss is regarded as a hallmark of tumour-suppressor ge ne (TSG) inactivation. Thirty-one human bladder transitional cell carc inomas (TCCs) were examined for allelic loss at five chromosome 18q lo ci, including the DCC gene (deleted in colorectal carcinoma) and at ch romosome 11p15 in a restriction fragment length polymorphism analysis. Allelic loss was observed at one or more 18q loci in 9/26 (35%) sampl es, associated with muscle-invasive disease (P<0.02). Allelic loss was observed at DCC in 8/24 (33%) samples, associated with muscle-invasiv e disease (P=0.05). Three out of the five evaluable recurrent TCCs exh ibited allelic loss at DCC, two of which were superficial. No allelic losses were detected at other 18q loci in tumours which retained both DCC alleles. Allelic loss was observed at 11p15 in 5/20 (25%) tumours. These data suggest the presence of a late-acting TSG located on 18q i n TCC bladder cancer. DCC is a candidate gene since it lies within the region of most common deletion (18q21.3-qter).