Growth inhibition of MCF-7 human breast cancer cells by progesterone is associated with cell differentiation and phosphorylation of Akt protein

Biomarker Alteration after Neoadjuvant Endocrine Therapy or Chemotherapy in Estrogen Receptor-Positive Breast Cancer

In estrogen receptor (ER)-positive breast cancer, changes in biomarker expression after neoadjuvant therapy indicate the therapeutic response and are prognostic. However, there is limited information about the biomarker alteration caused by neoadjuvant endocrine therapy in ER-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer. We recruited ER-positive/HER2-negative breast cancer patients who received neoadjuvant chemotherapy (NCT), neoadjuvant endocrine therapy (NET), or sequential neoadjuvant endocrine-chemotherapy (NECT) at Peking University Cancer Hospital from 2015 to 2021. A total of 579 patients had paired immunohistochemistry information in both diagnostic biopsy samples and post-neoadjuvant therapy surgical samples. Through a paired comparison of the immunohistochemical information in pre-treatment and post-treatment samples, we found that progesterone receptor (PR) expression reductions were more frequent than ER expression reductions (70.8% vs. 35.2%) after neoadjuvant therapy. The percentage of patients who had a decreased Ki-67 index in the post-operative samples was similar in the three groups (79.8% vs. 79.7% vs. 78.4%). Moreover, PR losses caused by NET were related to low baseline PR expression (p = 0.001), while we did not find a significant association between PR losses and Ki-67 reductions (p = 0.428) or ER losses (p = 0.274). All three types of neoadjuvant therapies caused a reduction in ER, PR, and Ki-67 expression. In conclusion, we found that PR loss after NET was only significantly related to low baseline PR expression, and there is no significant difference in the extent of prognostic factor change including Ki-67 and ER between the PR loss and non-loss groups.

Active FOXO1 Is a Key Determinant of Isoform-Specific Progesterone Receptor Transactivation and Senescence Programming

Progesterone promotes differentiation coupled to proliferation and prosurvival in the breast, but inhibits estrogen-driven growth in the reproductive tract and ovaries. Herein, it is demonstrated, using progesterone receptor (PR) isoform-specific ovarian cancer model systems, that PR-A and PR-B promote distinct gene expression profiles that differ from PR-driven genes in breast cancer cells. In ovarian cancer models, PR-A primarily regulates genes independently of progestin, while PR-B is the dominant ligand-dependent isoform. Notably, FOXO1 and the PR/FOXO1 target gene p21 (CDKN1A) are repressed by PR-A, but induced by PR-B. In the presence of progestin, PR-B, but not PR-A, robustly induced cellular senescence via FOXO1-dependent induction of p21 and p15 (CDKN2B). Chromatin immunoprecipitation (ChIP) assays performed on PR isoform-specific cells demonstrated that while each isoform is recruited to the same PRE-containing region of the p21 promoter in response to progestin, only PR-B elicits active chromatin marks. Overexpression of constitutively active FOXO1 in PR-A-expressing cells conferred robust ligand-dependent upregulation of the PR-B target genes GZMA, IGFBP1, and p21, and induced cellular senescence. In the presence of endogenous active FOXO1, PR-A was phosphorylated on Ser294 and transactivated PR-B at PR-B target genes; these events were blocked by the FOXO1 inhibitor (AS1842856). PR isoform-specific regulation of the FOXO1/p21 axis recapitulated in human primary ovarian tumor explants treated with progestin; loss of progestin sensitivity correlated with high AKT activity.

IMPLICATIONS

This study indicates FOXO1 as a critical component for progesterone signaling to promote cellular senescence and reveals a novel mechanism for transcription factor control of hormone sensitivity.

Anti-estrogenic mechanism of unliganded progesterone receptor isoform B in breast cancer cells

Over half of breast cancer cases are estrogen-dependent and strategies to combat estrogen-dependent breast cancer have been to either block the activation of estrogen receptor (ER) or diminish the supply of estrogens. Our previous work documented that estrogen-independent expression of progesterone receptor (PR) in MCF-7 cells markedly disrupted the effects of estrogen. In this study, we have developed an adenovirus-mediated gene delivery system to study the specific involvement of PR isoform A (PR-A) and PR-B in the anti-estrogenic effect and its mechanism of action. The results revealed that PR-B, but not PR-A, exhibited distinct anti-estrogenic effect on E2-induced cell growth, gene expression, and ER-ERE interaction in a ligand-independent manner. The anti-estrogenic effect of PR-B was also associated with heightened metabolism and increased cellular uptake of estradiol-17 beta (E2). We have also found that the B-upstream segment of PR-B alone was able to inhibit E2-induced ER-ERE interaction and cellular uptake of E2. Although PR-A alone did not affect E2-induced ER activity, it antagonized the anti-estrogenic effect of PR-B in a concentration-dependent manner. The findings suggest an important mechanism of maintaining a favorable level of ER activity by PR-A and PR-B in estrogen target cells for optimal growth and differentiation. The potential anti-estrogenic mechanism of PR-B may be exploited for breast cancer therapy.

Elucidating progesterone effects in breast cancer: Cross talk with PDGF signaling pathway in smooth muscle cell

Several studies indicate that progesterone exerts relevant effects in breast tissue. However, the exact role of this steroid in breast cancer development and progression has not been elucidated. Here, we show that platelet-derived growth factor (PDGF)-A is one of the progesterone target genes on breast cancer MCF7 and T47D cells. A paracrine role for PDGF-A was investigated, since its receptor expression was down-regulated from breast cancer cells. Progesterone increased PDGF-A protein release as evaluated by Western blotting and ELISA. Medium from Progesterone-treated MCF7 cells resulted in phosphorylation of smooth muscle cells PDGF receptor alpha. This effect was not observed after treatment with PDGF inhibitor. MCF7 cells-secreted PDGF-A was able to increase smooth muscle cell viability and proliferation and decrease apoptosis, effects that were prevented by the use of a PDGF-A neutralizing antibody. Notably, cell invasion was not influenced by PDGF-A secreted by MCF7 cells. Our results elucidated for the first time the cross talk between progesterone and PDGF signaling pathway. The fact that MCF7-secreted PDGF elicited crucial roles in vascular wall smooth muscle cells, suggested a paracrine pathway for progesterone. Targeting these progesterone-induced processes may provide novel therapeutic strategies for hormone-dependent human breast cancer.

The activities of progesterone receptor isoform A and B are differentially modulated by their ligands in a gene-selective manner

It is known that progesterone receptor (PR) isoform A (PR-A) and isoform B (PR-B) may mediate different effects of progesterone. The objective of this study was to determine if the functions of PR isoforms also vary in response to different PR modulators (PRM). The effects of 7 synthetic PRM were tested in MDA-MB-231 cells engineered to express PR-A, PR-B, or both PR isoforms. The effects of progesterone were similar in cells expressing PR-A or PR-B in which it inhibited growth and induced focal adhesion. On the other hand, synthetic PRM modulated the activity of the PR isoforms differently. RU486, CDB4124, 17alpha-hydroxy CDB4124 and VA2914 exerted agonist activities on cell growth and adhesion via PR-B. Via PR-A, however, these compounds displayed agonist effect on cell growth but induced stellate morphology which was distinct from the agonist's effect. Their dual properties via PR-A were also displayed at the gene expression level: the compounds acted as agonists on cell cycle genes but exhibited antagonistic effect on cell adhesion genes. Introduction of ERalpha by adenoviral vector to these cells did not change PR-A or PR-B mediated effect of PRM radically, but it causes significant cell rounding and modified the magnitudes of the responses to PRM. The findings suggest that the activities of PR isoforms may be modulated by different PRM through gene-specific regulatory mechanisms. This raises an interesting possibility that PRM may be designed to be PR isoform and cellular pathway selective to achieve targeted therapy in breast cancer.

TReP-132 is a novel progesterone receptor coactivator required for the inhibition of breast cancer cell growth and enhancement of differentiation by progesterone

The sex steroid progesterone is essential for the proliferation and differentiation of the mammary gland epithelium during pregnancy. In relation to this, in vitro studies using breast carcinoma T47D cells have demonstrated a biphasic progesterone response, consisting of an initial proliferative burst followed by a sustained growth arrest. However, the transcriptional factors acting with the progesterone receptor (PR) to mediate the progesterone effects on mammary cell growth and differentiation remain to be determined. Recently, it has been demonstrated that the transcriptional regulating protein of 132 kDa (TReP-132), initially identified as a regulator of steroidogenesis, is also a cell growth suppressor. Similar to progesterone-bound PR, TReP-132 acts by inducing the gene expression of the G1 cyclin-dependent kinase inhibitors p21WAF1/Cip1 (p21) and p27Kip1 (p27). The putative interaction between TReP-132 and progesterone pathways in mammary cells was therefore analyzed in the present study. Our results show that TReP-132 interacts in vitro and in T47D cells with progesterone-activated PR. TReP-132 synergizes with progesterone-bound PR to trans activate the p21 and p27 gene promoters at proximal Sp1-binding sites. Moreover, TReP-132 overexpression and knockdown, respectively, increased or prevented the induction of p21 and p27 gene expression by progesterone. As a consequence, TReP-132 knockdown also resulted in the loss of the inhibitory effects of progesterone on pRB phosphorylation, G1/S cell cycle progression, and cell proliferation. Furthermore, the knockdown of TReP-132 expression also prevented the induction of both early and terminal markers of breast cell differentiation which had been previously identified as progesterone target genes. As well, the progesterone-induced accumulation of lipid vacuoles was inhibited in the TReP-132-depleted cells. Finally, TReP-132 gene expression levels increased following progesterone treatment, indicating the existence of a positive auto-regulatory loop between PR and TReP-132. Taken together, these data identify TReP-132 as a coactivator of PR mediating the growth-inhibitory and differentiation effects of progesterone on breast cancer cells.

New progestagens for contraceptive use

The progestins have different pharmacologic properties depending upon the parent molecule, usually testosterone or progesterone (P), from which they are derived. Very small structural changes in the parent molecule may induce considerable differences in the activity of the derivative. In hormonal contraceptives, progestins represent the major agent designed for suppressing ovulation and are used in combination with estrogen (E) usually ethinyl-estradiol (EE). The development of new generations of progestins with improved selectivity profiles has been a great challenge. Steroidal and nonsteroidal progesterone receptor (PR) agonists have been synthesized as well, although the latter are still in a very early stage of development. Several new progestins, have been synthesized in the last two decades. These include dienogest (DNG), drospirenone (DRSP), Nestorone (NES), nomegestrol acetate (NOMAc) and trimegestone (TMG). These new progestins have been designed to have no androgenic or estrogenic actions and to be closer in activity to the physiological hormone P. DRSP differs from the classic progestins as it is derived from spirolactone. It is essentially an antimineralocorticoid steroid with no androgenic effect but a partial antiandrogenic effect. The antiovulatory potency of the different progestins varies. TMG and NES are the most potent progestins synthesized to date, followed by two of the older progestins, keto-desogestrel (keto-DSG) and levonorgestrel (LNG). The new molecules TMG, DRSP and DNG also have antiandrogenic activity. Striking differences exist regarding the side effects among the progestins and the combination with EE leads to other reactions related to the E itself and whether the associated progestin counterbalances, more or less, the estrogenic action. The 19-norprogesterone molecules and the new molecules DRSP and DNG are not androgenic and, therefore, have no negative effect on the lipid profile. Given their pharmacological properties, it is likely that the new progestins may have neutral effects on metabolic or vascular risks. However, this hypothesis must be confirmed in large clinical trials.

Progesterone inhibits human breast cancer cell growth through transcriptional upregulation of the cyclin-dependent kinase inhibitor p27Kip1 gene

The effects of progesterone derivatives on breast cancer development are still controversial, probably accounting for their biphasic, opposed effects on mammary cell-cycle regulation. Here, we demonstrate in vitro that the growth-inhibitory effects of progesterone on breast cancer T-47D cells require the transcriptional upregulation of the cyclin-dependent kinase inhibitor p27(Kip1) (p27) gene. A statistical analysis of human tumor biopsies further indicates that p27 mRNA levels correlate to progesterone receptor (PR) levels. Moreover, p27 gene expression is inversely associated with tumor aggressiveness, and is a prognostic factor of favorable disease outcome. Thus, progesterone derivatives selectively activating the p27 gene promoter could be promising drugs against breast cancer progression.

Precipitation casting of drug-loaded microporous PCL matrices: Incorporation of progesterone by co-dissolution

Microporous, poly(epsilon-caprolactone) (PCL) matrices were loaded with progesterone by precipitation casting using co-solutions of PCL and progesterone in acetone. Progesterone loadings up to 32% w/w were readily achieved by increasing the drug content of the starting PCL solution. The kinetics of steroid release in PBS at 37 degrees C over 10 days could be described effectively by a diffusional release model although the Korsmeyer-Peppas model indicated the involvement of multiple release phenomena. The diffusion rate constant (D) increased from 8 to 24 microg/mg matrix/day0.5 as the drug loading increased from 3.6 to 12.4% w/w. A total cumulative release of 75%-95% indicates the high efficiency of steroid delivery. Increasing the matrix density from 0.22 to 0.39 g/cm3, by increasing the starting PCL solution concentration, was less effective in changing drug release kinetics. Retention of anti-proliferative activity of released steroid was confirmed using cultures of breast cancer epithelial (MCF-7) cells. Progesterone released from PCL matrices into PBS at 37 degrees C over 14 days retarded the growth of MCF-7 cells by a factor of at least 3.5 compared with progesterone-free controls. These findings recommend further investigation of precipitation-cast PCL matrices for delivery of bioactive molecules such as anti-proliferative agents from implanted, inserted or topical devices.

Estradiol and medroxyprogesterone acetate regulated genes in T47D breast cancer cells

Many mammary tumors express estrogen receptors (ER) and progesterone receptors (PR), and there is increasing evidence that progestins influence gene expression of breast tumor cells. To analyse the impact of progestins on breast cancer cells, we compared (a) the expression of two cytokines, involved in tumor progression, and searched (b) for differentially regulated genes by a microarray, containing 2400 genes, on T47D breast cancer cells cultured for 6 days with 17beta-estradiol (E2) or E2+medroxyprogesterone acetate (E2+MPA). Lower amounts of PDGF and TNFalpha were found in culture supernatants of E2+MPA treated T47D cells. MPA addition induced a 2.8-3.5-fold increase of the mRNA expression of (a) tristetraprolin, which is involved in the posttranscriptional regulation of cytokine biosynthesis, and (b) zinc-alpha2-glycoprotein and Na, K-ATPase alpha1-subunit, which both resemble differentiation markers of breast epithelium. In contrast, the mRNA expression of lipocalin 2, which promotes matrixmetalloproteinase-9 activity, was decreased five-fold in E2+MPA treated cells. Our data show that the expression of genes from various functional gene families is regulated differentially by E2 and E2+MPA treatment in T47D cells. This suggests that exogenous progestins applied for therapy and endogenous changes of the progesterone levels during the menstrual cycle both influence breast cancer pathophysiology.

Breast cancer with different prognostic characteristics developing in Danish women using hormone replacement therapy

The aim of this study is to investigate the risk of developing prognostic different types of breast cancer in women using hormone replacement therapy (HRT). A total of 10 874 postmenopausal Danish Nurses were followed since 1993. Incident breast cancer cases and histopathological information were retrieved through the National Danish registries. The follow-up ended on 31 December 1999. Breast cancer developed in 244 women, of whom 172 were invasive ductal carcinomas. Compared to never users, current users of HRT had an increased risk of a hormone receptor-positive breast cancer, but a neutral risk of receptor-negative breast cancer, relative risk (RR) 3.29 (95% confidence interval (CI): 2.27–4.77) and RR 0.99 (95% CI: 0.42–2.36), respectively (P for difference=0.013). The risk of being diagnosed with low histological malignancy grade was higher than high malignancy grade with RR 4.13 (95% CI: 2.43–7.01) and RR 2.17 (95% CI: 1.42–3.30), respectively (P=0.063). For breast cancers with other prognostic characteristics, the risk was increased equally for the favourable and nonfavourable types. Current users of HRT experience a two- to four-fold increased risk of breast cancer with various prognostic characteristics, both the favourable and nonfavourable types. For receptor status, the risk with HRT was statistically significantly higher for hormone receptor-positive breast cancer compared to receptor-negative breast cancer.

Exogenous progestagens and the human breast

The role of progestins (or progestagens) on the breast tissue remains controversial. However, according to the molecule and the duration of application, cell differentiation and apoptosis may predominate over proliferation. Progestins are also used as second-line agents for the treatment of metastatic breast cancer. In young women with benign breast disease, long-term treatment with 19-nortestosterone progestins had a trend to decrease breast cancer risk contrarily to what was observed in postmenopausal women receiving estrogens. Several compounds with progestational activity have been used for HRT. Small differences in the structure of the molecules may lead to pronounced differences in activities, some progestins exerting androgenic effects and some exerting estrogenic or glucocorticoid like activities. While most progestins do not bind to the estrogen receptors, it has been shown that some androgenic progestins stimulate MCF7 cells proliferation while progestins derived from progesterone did not induce cell multiplication in the same cell lines. Therefore, different progestins may induce different effects on the breast cells. Whether the progestins available to date are able to bind specifically to the progesterone receptors PR-A or PR-B and whether this is of clinical relevance to breast cell proliferation is still unclear. Although the relationship between progestin use and breast cancer risk is still the subject of debate and controversy, the data reported to date suggest that 5 years of treatment carry a low risk but further duration of use increases the risk. Further studies are still needed, randomised long-term prospective studies as well as from the laboratory, especially to determine whether a sequential or continuous regimen would be preferable as far as breast-cell response and apoptosis are concerned, and what are the effects of the various molecules used for HRT.

Progesterone prevents radiation-induced apoptosis in breast cancer cells

Sex steroid hormones play an essential role in the control of homeostasis in the mammary gland. Although the involvement of progesterone in cellular proliferation and differentiation is well established, its exact role in the control of cell death still remains unclear. As dysregulation of the apoptotic process plays an important role in the pathogenesis of breast cancer, we investigated the regulation of apoptosis by progesterone in various breast cancer cell lines. Our results show that progesterone treatment protects against radiation-induced apoptosis. This prevention appears to be mediated by the progesterone receptor and is unrelated to p53 status. There is also no correlation with the intrinsic hormonal effect on cell proliferation, as the presence of cells in a particular phase of the cell cycle. Surprisingly, progesterone partly allows bypassing of the irradiation-induced growth arrest in G(2)/M in PgR+ cells, leading to an increase in cell proliferation after irradiation. One consequence of this effect is a higher rate of chromosome damage in these proliferating progesterone-treated cells compared to what is observed in untreated irradiated cells. We propose that progesterone, by inhibiting apoptosis and promoting the proliferation of cells with DNA damage, potentially facilitates the emergence of genetic mutations that may play a role in malignant transformation.

New Progestogens

The progestins have different pharmacological properties depending upon the parent molecule, usually testosterone or progesterone, from which they are derived. Very small structural changes in the parent molecule may induce considerable differences in the activity of the derivative. In postmenopausal women with an intact uterus, progestins are used in combination with estrogen as hormone-replacement therapy (HRT). The development of new generations of progestins with improved selectivity profiles has been a great challenge. Steroidal and nonsteroidal progesterone-receptor (PR) agonists have been synthesised as well, although the latter are still in a very early stage of development. Several new progestins, which have been synthesised in the last 2 decades, may be considered fourth-generation progestins. These include dienogest, drospirenone, Nestorone (Population Council, New York, NY, USA), nomegestrol acetate and trimegestone. The fourth-generation progestins have been designed to have no androgenic or estrogenic actions and to be closer in activity to the physiological hormone progesterone. Drospirenone differs from the classic progestins as it is derived from spirolactone. It is essentially an antimineralocorticoid steroid with no androgenic effect but a partial antiandrogenic effect. The antiovulatory potency of the different progestins varies. Trimegestone and Nestorone are the most potent progestins synthesised to date, followed by two of the older progestins, 3-keto-desogestrel and levonorgestrel. The new molecules trimegestone, drospirenone and dienogest also have antiandrogenic activity. Following the publication of the results of the Women's Health Initiative study, the role of progestins in HRT became controversial. Unfortunately, this concern has been directed towards progestins as a class, although striking differences exist among the progestins. Natural progesterone and some of its derivatives, such as the 19-norprogesterone molecules, and the new molecules drospirenone and dienogest are not androgenic and, therefore, have no negative effect on the lipid profile. The effects of progestins on breast tissue remain controversial as well. However, depending on the progestin and the duration of application, breast cell differentiation and apoptosis may predominate over proliferation. It is still unclear if the currently available progestins are able to bind specifically to the PR isoforms PR-A or PR-B and whether this is of clinical relevance to breast cell proliferation is also unclear. Although it is likely that the new progestins may have neutral effects on the risk of coronary heart disease or breast cancer in younger postmenopausal women, this hypothesis must be confirmed in large randomised, well controlled clinical trials.

Differential expression of Akt/protein kinase B, Bcl-2 and Bax proteins in human leiomyoma and myometrium

The expression and activation of serine/threonine protein kinase, Akt, in leiomyoma and in adjacent myometrium of human uteri was studied parallel with the changes of Bcl-2, Bax proteins, estrogen and progesterone receptors during menstrual cycle and early stage of the menopause. Abundant expression of Akt protein was detected in the studied tissues during menstrual cycle, the rate of increase was higher in leiomyoma than in corresponding myometrium. The expression of estrogen receptor alpha, progesterone receptor and of Bcl-2 protein changed parallel with that of Akt protein. The level of phosphorylated Akt (pAkt(473)) was seen only in leiomyoma samples from the growing period of tumors. At early stage of menopause levels of all studied proteins were lower than that in the menstrual cycle with the exception of Bax protein expression, which was high in leiomyoma. Our data suggest the involvement of phosphatidylinositol 3-kinase/Akt signaling in the pathomechanism of leiomyoma.

Apoptosis in the Endometrium of Postmenopausal Women Receiving Tibolone

BACKGROUND/AIM

Tibolone, a synthetic derivative of the 19-nortestosterone family, induces atrophy of the endometrium, especially via its progestogenic Delta(4) isomer. The aim of the study was to determine whether tibolone induces apoptosis in the endometrium of postmenopausal women.

METHODS

Twenty healthy postmenopausal women (mean age +/- SD 52.4 +/- 4.21 years) who had amenorrhea for at least 1 year and who had no history of any systemic illness and estrogen replacement therapy were enrolled in the study. All patients were offered office endometrial samplings, and then tibolone was prescribed (2.5 mg/day p.o., once daily) to all patients. Repeat endometrial samples were obtained after completion of the 6-month course of tibolone therapy. All samples were immunohistochemically analyzed for the presence of apoptotic cells.

RESULTS

There was no significant difference in the median proportion of apoptotic nuclei between the pre- and posttreatment samples (2 vs. 3%; p > 0.05).

CONCLUSIONS

The results showed that tibolone did not affect the rate of apoptosis in the postmenopausal endometrium. Further studies are needed to clarify the role of apoptosis in overall effects of hormonal compounds on the postmenopausal endometrium.