In vivo and in vitro estrogenic and progestagenic actions of Tibolone.

Estrogen and progestin combination in hormone replacement therapy (HRT) increases the incidence of breast cancer, but decreases the endometrial cancer risk of unopposed estrogen. Therefore, a SERM such as Tibolone, that delivers the beneficial, but not the adverse side effects, of steroid hormones would be clinically advantageous. However, data from the Million Women Study suggests that Tibolone increases the risk of both breast and endometrial cancer. Herein, we assessed the estrogenic and progestagenic actions of Tibolone using transvaginal sonography studies and an in vitro model of breast (ZR-75, MCF7) and endometrial cancer (Ishikawa). The known cancer associated proteins (ER, EGFR, STATS, tissue factor and Bcl-xL) were selected for study. Transvaginal sonography demonstrated that postmenopausal women treated with Tibolone displayed a thinner endometrium than in the late proliferative phase, but had a phenotype characteristic of the secretory phase, thus demonstrating the estrogenic and progestagenic actions of this SERM. In vitro, Tibolone acted as an estrogen in downregulating ER and upregulating Bcl-xL, yet as progesterone, increasing STAT5 and tissue factor in breast cancer cells. The increase in tissue factor by Tibolone correlated with its coagulative potential. Interestingly, EGFR was up-regulated by progesterone in the breast and by estrogen in endometrial cells, while Tibolone increased protein levels in both cell types. In conclusion, this study further demonstrates the estrogenic and progestagenic nature of Tibolone. The pattern of regulation of known oncogenes in cells of breast and endometrial origin dictates caution and vigilance in the prescription of Tibolone and subsequent patient monitoring.

Tissue factor is regulated by epidermal growth factor in normal and malignant human endometrial epithelial cells.

Tissue Factor (TF), the initiator of the extrinsic coagulation cascade, is overexpressed in a variety of cancers. TF is also expressed in normal human endometrium but little is known about its expression or regulation in endometrial cancer. We demonstrate herein that TF is expressed in the endometrial adenocarcinoma cell line Ishikawa. Furthermore, epidermal growth factor (EGF) induces a rapid and sustained increase in TF expression. Estradiol and progesterone had no effect on basal or EGF-induced TF expression in Ishikawa cells. In contrast to the pronounced and sustained upregulation at the protein level, EGF treatment elicited only a modest and transient increase in TF mRNA levels. This activity corresponded to the response observed from an exogenous TF promoter construct. However, the induction of TF was abrogated by cycloheximide as well as actinomycin-D, inhibitors or protein- and mRNA-synthesis, respectively, demonstrating that EGF mediates its effect through activation of the TF gene. Fractionation experiments showed that EGF increases TF presence in caveolin-I containing membrane fractions. Coagulation and invasion assays were used to explore the physiological implications of TF regulation. The results demonstrate that EGF-mediated induction of TF increases the procoagulant activity and invasive potential of Ishikawa cells. Furthermore, immunocytochemistry confirmed that TF is regulated by EGF in primary cultures of normal endometrial epithelial cells and malignant tumor cells. In conclusion, EGF-mediated upregulation of TF results in accumulation of this glycoprotein in caveolae-like membrane fractions and increased coagulative and invasive potential. Our results suggest that TF may play an integral role in endometrial carcinogenesis.

Progesterone increases tissue factor gene expression, procoagulant activity, and invasion in the breast cancer cell line ZR-75-1.

Progesterone in hormonal preparations increases the incidence of breast cancer. Tissue factor (TF), the initiator of the extrinsic coagulation pathway, is associated with metastasis in a wide variety of cancers. We demonstrate herein that TF mRNA and protein are up-regulated by progesterone in the breast cancer cell line ZR-75. Epidermal growth factor, also associated with increased breast cancer risk, did not regulate TF. The increase in TF is both rapid and transient; increasing after 6 h, reaching a maximum at 24 h, before decreasing to basal levels at 72 h. Sucrose gradient experiments demonstrated that TF is located in the heavy fraction of the plasma membrane, although caveolin-1 is not expressed in ZR-75. To understand the physiological implications of an increase in TF, we performed coagulation and invasion assays. An increase in TF corresponded to an increase in procoagulant activity. Furthermore, progesterone increased the invasion of ZR-75 cells through a matrigel, an effect that was blocked by an antibody against TF. Because TF expression is associated with an enhanced risk of metastasis, we postulate that the progesterone-dependent up-regulation of TF provides a survival advantage to burgeoning breast cancer cells and may contribute to the increased risk of cancer associated with combined hormone replacement therapy.

In vivo and in vitro estrogenic and progestagenic actions of Tibolone

Estrogen and progestin combination in hormone replacement therapy (HRT) increases the incidence of breast cancer, but decreases the endometrial cancer risk of unopposed estrogen. Therefore, a SERM such as Tibolone, that delivers the beneficial, but not the adverse side effects, of steroid hormones would be clinically advantageous. However, data from the Million Women Study suggests that Tibolone increases the risk of both breast and endometrial cancer. Herein, we assessed the estrogenic and progestagenic actions of Tibolone using transvaginal sonography studies and an in vitro model of breast (ZR-75, MCF7) and endometrial cancer (Ishikawa). The known cancer associated proteins (ER, EGFR, STAT5, tissue factor and Bcl-xL) were selected for study. Transvaginal sonography demonstrated that postmenopausal women treated with Tibolone displayed a thinner endometrium than in the late proliferative phase, but had a phenotype characteristic of the secretory phase, thus demonstrating the estrogenic and progestagenic actions of this SERM. In vitro, Tibolone acted as an estrogen in downregulating ER and upregulating Bcl-xL, yet as progesterone, increasing STAT5 and tissue factor in breast cancer cells. The increase in tissue factor by Tibolone correlated with its coagulative potential. Interestingly, EGFR was up-regulated by progesterone in the breast and by estrogen in endometrial cells, while Tibolone increased protein levels in both cell types. In conclusion, this study further demonstrates the estrogenic and progestagenic nature of Tibolone. The pattern of regulation of known oncogenes in cells of breast and endometrial origin dictates caution and vigilance in the prescription of Tibolone and subsequent patient monitoring.

Differential regulation of glucose transporter expression by estrogen and progesterone in Ishikawa endometrial cancer cells.

Estrogen replacement therapy and other unopposed estrogen treatments increase the incidence of endometrial abnormalities, including cancer. However, this effect is counteracted by the co-administration of progesterone. In the endometrium, glucose transporter (GLUT) expression and glucose transport are known to fluctuate throughout the menstrual cycle. Here, we determined the effect of estrogen and progesterone on the expression of GLUT1-4 and on the transport of deoxyglucose in Ishikawa endometrial cancer cells. Cells were incubated with estrogen, progesterone or combined estrogen and progesterone for 24 h and the effect on the expression of GLUT1-4 and on deoxyglucose transport was determined. We show that GLUT1 expression is upregulated by estrogen and progesterone individually, but that combined estrogen and progesterone treatment reverses this increase. Hormonal treatments do not affect GLUT2, GLUT3 or GLUT4 expression. Transport studies demonstrate that estrogen increases deoxyglucose transport at Michaelis-Menten constants (Kms) corresponding to GLUT1/4, an effect which disappears when progesterone is added concomitantly. These data demonstrate that different hormonal treatments differentially regulate GLUT expression and glucose transport in this endometrial cancer cell line. This regulation mirrors the role played by estrogen and progesterone on the incidence of cancer in this tissue and suggests that GLUT1 may be utilized by endometrial cancer cells to fuel their demand for increased energy requirement.