MUTATION FREQUENCIES AT CODON-248 OF THE P53 TUMOR-SUPPRESSOR GENE ARE NOT INCREASED IN COLON-CANCER CELL-LINES WITH THE RER+ PHENOTYPE

The replication-error positive (RER+) phenotype characterizes tumour c ells with microsatellite instability. This 'mutator phenotype' is thou ght to induce spread mutations throughout the genome, thus increasing the risk of tumour development, Here we analyse spontaneously arising mutations at the tetranucleotide CCGG (Mspl recognition site), at posi tions 14 067-14 070 of the p53 gene sequence, in three colon cancer ce ll lines, two with microsatellite instability and one without this cha racteristic. This restriction site covers hot-spot codon 248, which is often mutated in colon carcinomas, Using the Mspl RFLP-PCR assay we f ound that the mean mutation frequency at this site was not different a mong the cell lines considered, Taking the substitutions separately, n one of the mutations involving codon 248 arose with significantly high er frequency in each of the RER+ cell lines (HCT11G and DLD1) compared with the RER- one (SW480), Only the CG transversion at nt 14 067 (cod on 247) occurred with a slightly higher, but biologically insignifican t, frequency in one of the RER+ cell lines (HCT116), Our in vitro data support the previously reported lack of correlation between microsate llite instability and p53 mutations in RER+ tumour specimens.