Up-Regulation by Progesterone of Proliferating Cell Nuclear Antigen and Epidermal Growth Factor Expression in Human Uterine Leiomyoma1

Abstract

Uterine leiomyoma is the most common smooth muscle cell tumor of the myometrium. Estrogen and progesterone (P4) are believed to be physiological regulators of leiomyoma growth. We recently showed that Bcl-2 protein, an apoptosis-inhibiting gene product, was abundantly expressed in leiomyoma relative to its expression in the normal myometrium and that Bcl-2 protein expression in cultured leiomyoma cells was up-regulated by P4, but down-regulated by 17 beta-estradiol (E2). To further characterize the molecular mechanism of sex steroidal regulation of leiomyoma growth, we examined the effect of menstrual phase on proliferating cell nuclear antigen (PCNA) expression in leiomyoma and investigated whether sex steroids could influence PCNA expression in leiomyoma cells cultured under serum-free conditions by immunoblot and immunohistochemical analyses. As epidermal growth factor (EGF) has been shown to mediate estrogen action and to play a crucial role in regulating leiomyoma growth, we also investigated the effects of sex steroids on the expression of EGF and EGF receptor (EGF-R) in cultured leiomyoma cells. The PCNA labeling index in leiomyomas was much greater in the secretory, P4-dominated, phase than in the proliferative phase of the menstrual cycle and was significantly higher than that in the adjacent normal myometrium throughout the menstrual cycle. In monolayer cultures of leiomyoma cells, the addition of either E2 (10 ng/mL) or P4 (100 ng/mL) resulted in an increase in PCNA expression in the cells compared to that in control cultures, whereas in monolayer cultures of myometrial cells, the addition of E2 augmented PCNA expression in the cells, but P4 did not. Immunoblot analysis of proteins extracted from cultured leiomyoma cells revealed that leiomyoma cells contained immunoreactive EGF with a molecular mass of 133 kDa and that the addition of P4 resulted in a remarkable increase in the expression of 133- and 71-kDa immunoreactive EGF in the cells compared to that in control cultures, whereas the addition of E2 resulted in a somewhat lower expression of immunoreactive EGF in the cells. Furthermore, immunocytochemical analysis with a monoclonal antibody to human EGF-R demonstrated that the treatment with E2 augmented EGF-R expression in the cells compared to that in untreated cells, but P4 did not. The concentrations of sex steroids used were within the physiological tissue concentrations found in leiomyomas and myometria. These results indicate that P4 up-regulates the expression of PCNA and immunoreactive EGF in leiomyoma cells, whereas E2 up-regulates the expression of PCNA and EGF-R in those cells. As it is evident that EGF plays a crucial role as a local factor in regulating leiomyoma growth, the P4-induced increase in PCNA expression in leiomyoma cells may be mediated by P4-induced enhanced expression of EGF-like proteins in the cells, whereas the E2-induced increase in PCNA expression in leiomyoma cells may be mediated by E2-induced enhanced expression of EGF-R in those cells. It is, therefore, conceivab...

Molecular Bases for the Actions of Ovarian Sex Steroids in the Regulation of Proliferation and Apoptosis of Human Uterine Leiomyoma

“…As it is evident that EGF plays a crucial role as a local factor in regulating leiomyoma growth, the P 4 -induced increase in PCNA expression in leiomyoma cells may be mediated by P 4 -induced enhanced expression of EGF-like proteins in the cells, while the E 2 -induced increase in PCNA expression in leiomyoma cells may be mediated by E 2 -induced enhanced expression of EGF-R in those cells. It is, therefore, conceivable that P 4 and E 2 act in combination to stimulate the proliferative potential of leiomyoma cells through the induction of EGF-like proteins and EGF-R expression in uterine leiomyoma [27]. …”

Lessons learned from the preclinical drug discovery of asoprisnil and ulipristal for non-surgical treatment of uterine leiomyomas

“…EGF is shown to increase the uptake of 3 H-thymidine and the PCNA-positive rate in cultured leiomyoma cells, suggesting that EGF stimulates the proliferative activity of those cells [20]. Furthermore, the authors have demonstrated that treatment with P4 increases the expression of PCNA [20], EGF and Bcl-2 proteins [16] in cultured leiomyoma cells, whereas treatment with E2 increases EGF receptor (EGFR) expression in those cells [16]. It is, therefore, conceivable that P4 acts in combination with E2 to stimulate the proliferative potential of cultured leiomyoma cells through the induction of EGF and EGFR in those cells.…”

“…In vitro studies with cultured leiomyoma cells and normal myometrial cells have revealed that P4, in addition to estradiol (E2), plays a vital role in the promotion of leiomyoma cell growth [14][15][16][17][18]. To our great interest, treatment with P4 augmented the proliferative activity in cultured leiomyoma cells, but not in cultured normal myometrial cells.…”

Progestin Regulation in Tumor Growth of Female Genital Tract Cancers

“…Uterine leiomyoma, recognized as an estrogen-dependent tumor, is partially progestin dependent in growth [8, 12]. Equal expression of PR-A and PR-B was found in 18 of 29 cases of uterine leiomyoma, while PR-B transcripts were dominantly expressed in the other 11 cases.…”

“…However, tumor growth in some other cases becomes irregularly progestin dependent or progestin refractory during tumor progression [4, 5, 6, 7, 8, 9, 10, 11, 12]. To understand the direct molecular mechanisms related to cancer cell proliferation via steroid receptor cascades, the status of wild-type progesterone receptor (PR) and its mutants has been studied.…”