Absence of mutations in the highest mutability region of the p-53 gene in tumour-derived CHEF18 Chinese hamster cells

A series of independent tumour–derived Chinese hamsterCHEF18 cell lines was analyzed for the presence of mutationsin the cDNA region (exons 5–9) of the p53 gene, wherethe great majority of p53 mutations of human tumours accumulate.Since the gene is highly conserved among species, we used twoprimers designed on the basis of the human cDNA sequence toisolate the cDNA region from total RNA of Chinese hamster cells.The amplified fragments of 614 bp were digested with cleavaseI endonuclease and fragment length polymorphism analysis showedthat the restriction pattern of the p53 exons 5–9 regionof tumour–derived cell lines was identical to that ofdiploid Chinese hamster CHL fibroblasts. Sequencing of the amplifiedfragments showed 100% homology between sequences, which demonstratedthe absence of p53 mutations in the exons 5–9 cDNA regionexpected to have the highest mutability. Neverthless, the antibodyDO–7 recognized the presence of a stabilized p53 proteinonly in tumour–derived cell lines, which indicated thatp53 expression correlated with transformed status. ³To whom correspondence should be addressed. Tel: +00 39 50 577834; Fax: +00 39 50 576661; Email: g.rainaldi{at}imd.pi.cnr.it