Molecular mechanisms of regulation of uterine leiomyoma growth

Background : to elucidate the molecular mechanisms, regulating growth and proliferation of leiomyoma cells, the estimation of the activity of PR-A and PR-B isoforms of progesterone receptor and PI3K/Akt and MAPК kinases, participating in signal transduction from sex steroids and growth factors, has the special interest. Aim of the work : to investigate the character of the expression of mRNAs of PR-A and PR-B isoforms of progesterone receptor in leiomyomas of different size and different intensity of cellular proliferation, and to elucidate the relationship between the PR-A and PR-B synthesis and activation of PI3K/Akt and MAPК signaling pathways in tumour tissue. Materials and Methods . The examination of the PR-A, PR-B, Akt, PTEN, ERK and Ki67 mRNAs expression in normal myometrium and leiomyoma tissues of 29 women with uterine leiomyoma was performed using RP-PCR. Results . It was found that in general the leiomyoma tissue was characterized by the high level of PR-A, PTEN and ERK mRNAs expression comparing to the miometrium. Distinctive characteristic of the small leiomyomas and leiomyomas with low proliferative activity was the highest synthesis of PR-A isoform of progesterone receptor. In large leiomyomas and in proliferating Ki67+ leiomymas the significant increase of ERK mRNA expression was seen. Conclusion . Activation of the PR-A isoform of progesterone receptor and MAPK/ERK signaling pathway associated with the inhibition of PI3K/Akt signaling due to high synthesis of PTEN plays the important role in mechanisms, regulating leiomyoma growth.