Messenger RNA determination of estrogen receptor, progesterone receptor, pS2, and plasminogen activator inhibitor-1 by competitive reverse transcription-polymerase chain reaction in human breast cancer

Estrogen receptor (ER), progesterone receptor (PR), the estrogen-inducible protein pS2, and plasminogen activator inhibitor-1 (PAI-1) are important pr ognostic factors in primary breast cancer. The protein concentrations of th ese factors in breast tumors have been well documented, However, few data a bout the mRNA expression of ER, PR, pS2, and PAI-1 in breast cancer are ava ilable, which is mostly due to the limitations of conventional techniques f or mRNA analysis. We have described a competitive reverse transcription-PCR system for the simultaneous quantification of ER, PR, pS2, and PAI-1 mRNA in tumor samples. Here, we evaluated 100 tumor biopsies from breast cancer patients for the mRNA expression of ER, PR, pS2, and PAI-1. The results wer e analyzed for correlations with protein status and with clinical data. Sig nificant correlations between mRNA expression levels and protein concentrat ions of all tested markers were found. In only a few eases was there an obv ious discordance between the measurable amounts of mRNA and protein, especi ally for ER and PR. In addition, ER, PR, and pS2 mRNA levels correlated sig nificantly with each other. No correlation between PAI-1 mRNA amount and th e expression of the other markers was found. With respect to clinical data, ER and PR mRNA levels were found to be inversely correlated to tumor size and histological grade but not to the lymph node status. pS2 and PAI-1 mRNA expression were not correlated with tumor size, grade, or lymph node invol vement. In conclusion, competitive reverse transcription-PCR may be used as an alternative for the study of prognostic factors in human breast cancer and other malignancies. However, before mRNA expression is measured for dia gnostics, a presumed concordance of mRNA and protein expression must be eva luated very carefully for every gene.