The expression of aromatase (estrogen synthetase) is tissue specifically regulated through the alternative use of multiple exons 1 and promoters. We have determined the amounts of aromatase messenger ribonucleic acid (mRNA) and which type of multiple exons 1 of the human aromatase gene is used in breast tissues of 49 patients with breast cancer by reverse transcription- PCR analysis. The aromatase mRNA levels in these breast cancer tissues (4.53 ± 0.66 x 10-3 attomoles/μg RNA) were significantly (P < 0.01) higher than those in 16 nonmalignant breast tissues (1.73 ± 0.40 x 10-3 amol/μg RNA). Aromatase mRNA in all nonmalignant breast tissues was transcribed from skin fibroblast/fetal liver-specific exon 1 (exon 1b) of the gene. In 23 breast cancer tissues, the utilization of multiple exons 1 in the aromatase mRNa was the same as that in nonmalignant breast tissues, whereas in the other 26 cases, it changed from exon 1b to ovary-specific exon 1 (exon 1c). Such switching of tissue-specific exons 1 may affect strict regulation of the tissue-specific expression of aromatase, leading to abnormal expression of the aromatase. The consequent overproduction of local estrogen might promote carcinogenesis or the proliferation of breast cancers.
All Science Journal Classification (ASJC) codes