Comparison between p53 protein measurements using the luminometric immunoassay and immunohistochemistry with detection of p53 gene mutations using cDNA sequencing in human breast tumors.

• The p53 mutational status of 226 representative primary breast cancer samples, derived from a population-based cohort, was analyzed using cDNA-based sequencing. The results were comparedwith those obtained with immunohistochemistry (IHC) on microwave-treated paraffin sections and the p53specific luminometric immunoassay (LIA) on cytosols, all from the same individuals. Thirty-sevenmutations were found using cDNA sequencing and were categorized into A) missense mutations in theevolutionarily conserved regions; B) missense mutations outside the evolutionarily regions; and C) deletions, insertions and nonsense mutations. Using optimal cut-off values, LIA detected 15 of 16 missense mutations in category A, in which IHC defected all 16. In category B, 10 of 13 and 7 of 13mutations were detected, respectively. Some of the samples in category A had a very high p53 proteincontent when measured with the LIA, the reason for this being discussed. IHC detected 0 of 5 stop codon and 0 of 3 deletions/insertions mutations, while the LIA method detected 2 of 5 stop codon mutations and Iof 3 deletion/insertion mutations. Compared with cDNA sequencing, protein analyses using optimal cut-off values resulted in an overall sensitivity and specificity of 64.9% and 89.9%, respectively, for the LIA method. Corresponding values were 72.2% and 92% for IHC. In addition, patients from whom p53mutations could be detected by cDNA sequencing had a statistically significant (p = 0.0137) shorter survival, which was not readily apparent using the alternative LIA or IHC approaches at optimal cut-off values. 

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