Aberrant p53 protein expression and function in a panel of hematopoietic cell lines with different p53 mutations.

The p53 gene is one of the most important genes involved in carcinogenesis and its role in part has been clarified by research using cell lines. To know the comprehensive characteristics of 22 hematopoietic cell lines (T, 13 and non-T, nine lines), the relationship between p53 mutational status, its altered functioning, and its mRNA and protein levels were examined. p53 mutations were less frequent in T-cell lines (38% vs. 78%) with mainly single nucleotide substitutions generating missense codons. Of 22 different p53 mutations, 12 (54.5%) resulted in mutated proteins, with the mutations clustering mainly in the sequence-specific DNA-binding site region located from amino acid residues 102 to 292. p53 mRNA and protein assays determined that wild-type cell lines expressed constant levels of both mRNA and protein, but mutated cell lines demonstrated two expression patterns: protein over-expression with reduced mRNA levels, because of missense mutations; and protein under-expression with little mRNA expression, because of other mutations. The resistance to Nutlin (MDM2 inhibitor)-induced apoptosis was associated with p53 mutations independently of MDM2 expression levels. This clarification of the unique associations in cell lines useful for bio-medical studies will contribute to a better understanding of p53-associated carcinogenesis.