Real-time reverse transcription PCR assay of CYP19 expression: application to a well-defined series of post-menopausal breast carcinomas.

Aromatase, the product of the CYP19 gene, plays a key role in androgenic steroids transformation into estrogens from various hormonal sensitive tissues. Thus, in situ expression of CYP19 has been suggested to be involved in breast tumor growth especially in post-menopausal patients.We developed a real-time quantitative RT-PCR assay based on fluorescent TaqMan methodology to quantify total CYP19 gene expression at the mRNA level in breast tumors. This method, based on nucleic acid quantification in homogeneous solutions, has the potential to become a standard in terms of its sensitivity, wide dynamic range and high-throughput capacity. In a well-defined series of 107 post-menopausal breast tumor samples, relative CYP19 mRNA levels ranged from 1 to 131. Among the four major CYP19 exon I-spliced transcripts, designated I.a, I.b, I.c and I.d, mRNA levels of the latter three correlated positively with total CYP19 mRNA levels. In ER alpha-positive breast tumors, CYP19 and ER alpha mRNA levels correlated negatively with each other (P=0.0078, r=-0.266), while CYP19 and ER beta mRNA levels correlated positively (P=0.00012, r=+0.388). Patients with high CYP19 mRNA levels did not relapse more frequently or have shorter relapse-free survival than other patients. Finally, mRNA levels of IL6, a major CYP19 regulatory factor, were significantly higher in tumors strongly expressing CYP19 than in tumors weakly expressing CYP19 (P=0.018). In conclusion, CYP19 expression did not influence the outcome of post-menopausal patients with breast cancer.