Can the increase in breast cancer observed in the estrogen plus progestin arm of the Women's Health Initiative trial be explained by progesterone receptor membrane component 1?

The WHO claims estrogens are 'carcinogenic': is this true?

Estrogens are in the list of carcinogenic chemicals from the World Health Organization (WHO). However, estrogens require additional factors such as stromal factors or progestogens to increase the ratio of proliferation/apoptosis for initiation of replication errors and consequent mutations to occur. These mutations require at least 5-10 years to develop into clinically detectable cancer, whereby this review is focused on breast cancer. The US National Cancer Institute highlighted a second mechanism of carcinogenicity: certain estrogen metabolites are capable of inducing DNA damage, even in low concentration. They can be assessed in the tissue and circulation. However, those deleterious reactions require excessive unrestricted oxidative cell stress, for example in industrial areas with heavy pollution. We have shown that this can be avoided using transdermal instead of oral estradiol treatment, especially important in smokers. The spectrum of metabolites is also influenced by other exogenous factors such as nutrition, physical activity and certain diseases. Reduction of breast cancer risk as demonstrated in the Women's Health Initiative (WHI) was explained by pro-apoptotic estrogen effects working after a certain 'time gap'. In addition, certain estrogen metabolites are carcinoprotective, if no genetic polymorphisms would impair their beneficial activities. Thus, since additional factors are required for both main pathways of carcinogenicity and because estrogens can even have carcinoprotective effects, we cannot agree with the statement from the WHO.

Primary choice of estrogen and progestogen as components for HRT: a clinical pharmacological view

Prescribing hormone replacement therapy (HRT) requires consideration of the selection of its two components, the estrogen and the progestogen. In terms of the estrogen, the decision is mainly whether to use estradiol (E2) or conjugated equine estrogens (CEE). These are the components needed to efficiently treat climacteric symptoms or/and prevent osteoporosis, currently the only labeled indications. There is still controversy regarding the adequate dosages comparing E2 and CEE; however, the consensus is that the differences in the efficacy of E2 and CEE are not a real issue. Therefore, other criteria have to be used. The first reason to add the progestogen is to avoid the development of endometrial cancer (i.e. to achieve 'endometrial safety'). Any available 'fixed-combined' HRT preparation has to be tested for sufficient endometrial efficacy, because the first question the health authorities ask before product registration relates to endometrial safety. We can generally rely on the endometrial safety of these fixed-combined products. However, it could be that we want to use 'free' combinations, which are necessary if we use transdermal E2 (patches, gel, spray), but also to individualize schedules, for example when treating bleeding problems. The question here is how to attain knowledge about the endometrial efficacy of the different progestogens and how to monitor therapy. We will try to answer these two questions from a 'clinical pharmacology' point of view, as a discipline which preferably considers pharmacological properties, but also relating to clinical practice, to achieve individualized therapy with optimal efficacy, best tolerability and minimal risks.

E2 + norethisterone promotes the PI3K-AKT pathway via PGRMC1 to induce breast cancer cell proliferation

OBJECTIVE

This study aimed to find evidence that progesterone receptor membrane component 1 (PGRMC1) promotes estradiol (E2) + norethisterone (NET)-induced breast cancer proliferation through activation of the phosphatidylinositol-3-kinase (PI3K)-AKT pathway.

METHODS

PGRMC1-mediated breast cancer cellular proliferation and phosphorylation of PGRMC1 were studied using wild-type (hemagglutinin [HA]-tagged) MCF-7 cells, which were stably transfected with expression vector containing HA (MCF-7-HA cells), PGRMC1 (MCF-7-PGRMC1 cells) and Ser181 point mutated PGRMC1 (MCF-7-PGRMC1-S181A cells). Bioinformatics, cell proliferation, western blot, isobaric tags for relative and absolute quantitation (iTRAQ)-based RNA sequencing, real-time quantitative polymerase chain reaction (RT-qPCR) and cell cycle in vitro assays were performed to indicate the function of PGRMC1 and its possible mechanisms in breast cancer.

RESULTS

NET + E2 elicited a significant proliferation in MCF-7-Vec at 10^-6 M and 10^-10 M, respectively. MCF-7-PGRMC1 did increase the phosphorylation of AKT or ERK, which can be blocked by treatment with casein kinase 2 (CK2) inhibitor quinalizarin or in MCF-7-PGRMC1-S181A cells. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the PI3K-AKT pathway is upregulated in MCF-7-PGRMC1 cells. Importantly, upregulation of the PI3K-AKT pathway mainly through promotion of cell cycle regulation strongly promoted cell proliferation in MCF-7-PGRMC1 cells.

CONCLUSIONS

CK2 is involved in phosphorylation of PGRMC1 at S181. The mechanism for the action of PGRMC1 for mediating proliferative progestogen effects obviously starts with promotion cell cycle regulation, and then activation of the PI3K-AKT pathway.

PGRMC Proteins Are Coming of Age: A Special Issue on the Role of PGRMC1 and PGRMC2 in Metabolism and Cancer Biology

This is a preface by the guest editors of the special issue of Cancers featuring the biology of progesterone (P4) receptor membrane component (PGRMC) proteins as it relates to metabolism and cancer [...].

Association of circulating Progesterone Receptor Membrane Component-1 (PGRMC1) with breast tumor characteristics and comparison with known tumor markers

OBJECTIVES

Progesterone receptor membrane component-1 (PGRMC1) expressed in breast cancer tissue has been suggested to predict a worse prognosis. The aim of this study was to assess for the first time if blood concentrations of PGRMC1 are also associated with receptor status, tumor diameter, grading, and lymphatic status. The second aim was comparison with known tumor markers.

METHODS

A total of 372 women, including 278 patients with invasive breast cancer, 65 with benign breast disease, and 29 healthy women (control), were recruited. PGRMC1 blood concentrations were measured by a recently developed enzyme-linked immunosorbant assay, and were correlated to predictive tumor characteristics and compared with serum carcinoembryonic antigen (CEA), CA125, and CA153.

RESULTS

PGRMC1 levels in the cancer group were significantly higher than in the control and benign group and increased with higher cancer stages (P < 0.05). PGRMC1 concentrations in the estrogen receptor (ER)+/progesterone receptor (PR)+ group were higher than in the ER-/PR- group, related to larger tumor diameter and the presence of lymph node metastasis (P < 0.05). Multivariable linear regression analysis was used to control the confounding factors. Tumor diameter, lymphatic metastasis, and ER (but not PR) were positively associated with PGRMC1 (P < 0.05). The receiver-operating characteristic curve (ROC) analysis was used to assess area under the curve (AUC). AUC was 87.9% for stages III+IV and 80.8% for stages I+II (P < 0.01). ROC did not find significant effects on AUC for CA125, only significant for CEA and CA153 for stages III+IV.

CONCLUSION

As PGRMC1 levels are positively associated with breast tumor characteristics known to predict a worse diagnosis, PGRMC1 may be valuable as a new tumor marker, and superior to CEA, C125, and CA153. Because of the positive association with ER-expression, PGRMC1 may interact with this receptor.

PGRMC1 in animal breast cancer tissue and blood is associated with increased tumor growth with norethisterone in contrast to progesterone and dydrogesterone: four-arm randomized placebo-controlled xenograft study

Progesterone receptor membrane component 1 (PGRMC1) is mediating strong breast cancer cell proliferation induced by certain synthetic progestogens which we have shown within already published in vitro studies. Aim was now to use an animal model, to compare tumor growth using progesterone and its isomer dydrogesterone with norethisterone, which elicited in our in vitro studies the strongest proliferating effect. For the first time, we wanted to investigate if growth can be correlated both with blood concentrations and tissue expression of PGRMC1 to identify if PGRMC1 could be a new tumor marker. Prospective, randomized, blinded, placebo-controlled four-arm study (45-50 days); PGRMC1-transfected or empty-vector T47D- and MCF7-xenotransplants were each treated with estradiol (E2) +placebo; E2 + progesterone; E2 + norethisterone; E2 + dydrogesterone; blood PGRMC1 assessed by a novel ELISA, tissue expression by immunohistochemistry. PGRMC1-transfected tumors further increased with E2 + norethisterone but not with E2-dydrogesterone or E2-progesterone. In both PGRMC1-xenograft groups (T47D, MCF7) with E2/norethisterone, the blood concentrations and tissue expression of PGRMC1 were higher than in all other 14 groups (p < .05), with positive significant correlation between blood PGRMCI concentrations and tissue PGRMC1 expression. In the presence of PGRMC1, certain progestogens could increase the growth of breast tumor, which now also should be tested in clinical studies.

Association of circulating Progesterone Receptor Membrane Component-1 (PGRMC1) with PGRMC1 expression in breast tumour tissue and with clinical breast tumour characteristics

OBJECTIVES

Progesterone receptor membrane component-1 (PGRMC1) in breast cancer tissue has been suggested to predict a worse prognosis. The aim of this study was to assess for the first time whether PGRMC1 expressed in cancer tissue is associated with PGRMC1 blood concentrations and whether both are correlated with clinical tumour characteristics known to predict a worse outcome.

METHODS

In total, 201 patients with invasive breast cancer and 65 with benign breast disease (control group) were recruited. PGRMC1 blood concentrations were measured by a recently developed ELISA, PGRMC1 in breast cancer tissue was assessed by immunohistochemistry, and the correlation between the two was calculated. Receiver-operating characteristic (ROC) curve analysis was used to assess area under the curve (AUC). Furthermore, PGRMC1 was correlated with tumour characteristics such as tumour diameter, tumour grade and metastatic status, and with known blood tumour markers.

RESULTS

AUC for the breast cancer group was 0.713, which was significantly higher than in the control group (p < 0.01). Blood PGRMC1 concentrations had a strong (positive) correlation with tissue PGRMC1 expression (p < 0.01) but were not associated with serum tumour markers CEA, CA125, CA153 and TPS. Tissue PGRMC1, ER and cancer stage were positively associated with blood PGRMC1 (p < 0.05).

CONCLUSIONS

As PGRMC1 expression levels in cancer tissue were significantly correlated with PGRMC1 in blood, and because concentrations in blood were also positively associated with breast tumour characteristics known to predict a worse prognosis, PGRMC1 may be valuable as a new tumour marker and may be superior to known tumour markers such as CEA, CA125, CA153 and TPS.

Progesterone and Breast Cancer

Synthetic progestogens (progestins) have been linked to increased breast cancer risk; however, the role of endogenous progesterone in breast physiology and carcinogenesis is less clearly defined. Mechanistic studies using cell culture, tissue culture, and preclinical models implicate progesterone in breast carcinogenesis. In contrast, limited epidemiologic data generally do not show an association of circulating progesterone levels with risk, and it is unclear whether this reflects methodologic limitations or a truly null relationship. Challenges related to defining the role of progesterone in breast physiology and neoplasia include: complex interactions with estrogens and other hormones (eg, androgens, prolactin, etc.), accounting for timing of blood collections for hormone measurements among cycling women, and limitations of assays to measure progesterone metabolites in blood and progesterone receptor isotypes (PRs) in tissues. Separating the individual effects of estrogens and progesterone is further complicated by the partial dependence of PR transcription on estrogen receptor (ER)α-mediated transcriptional events; indeed, interpreting the integrated interaction of the hormones may be more essential than isolating independent effects. Further, many of the actions of both estrogens and progesterone, particularly in "normal" breast tissues, are driven by paracrine mechanisms in which ligand binding to receptor-positive cells evokes secretion of factors that influence cell division of neighboring receptor-negative cells. Accordingly, blood and tissue levels may differ, and the latter are challenging to measure. Given conflicting data related to the potential role of progesterone in breast cancer etiology and interest in blocking progesterone action to prevent or treat breast cancer, we provide a review of the evidence that links progesterone to breast cancer risk and suggest future directions for filling current gaps in our knowledge.

PGRMC1 can trigger estrogen-dependent proliferation of breast cancer cells: estradiol vs. equilin vs. ethinylestradiol

Objective: Previous studies have shown that progesterone receptor membrane component 1 (PGRMC1) expressed in breast cancer tissue can predict a worse prognosis for breast cancer patients. Moreover, we demonstrated that PGRMC1 can increase the proliferation of progestogens. However, the role of PGRMC1 in terms of estrogen-induced proliferation and comparing different estrogens is still unclear. Methods: Non-transfected and PGRMC1-transfected T-47D cells were stimulated with estradiol (E2), with equilin (EQ), or with ethinylestradiol (EE) at 1, 10, and 100 nmol/l. Increase of proliferation was compared with a control (without estrogens) and with the estrogen-induced stimulation in empty vector cells vs. PGRMC1-transfected cells. Results: The empty vector cells showed significant proliferation (12-15%) with all three estrogens only at the highest concentration, with no relevant differences between the estrogens. PGRMC1-transfected cells showed about three-fold higher proliferation (29-66%), whereby E2 elicited the strongest and EE the lowest proliferating effects, significantly lower compared to E2 and also compared to EQ. No significant differences were seen between E2 and EQ. Conclusions: PGRMC1 increases strongly the estrogen-dependent breast cell proliferation. The proliferating effects of EE may be lower compared to E2 and EQ. This could have importance in comparing hormone therapy and contraception. Thus, PGRMC1 not only could predict the risk using progestogens but also of different estrogens.

Membrane-initiated effects of Serelys® on proliferation and apoptosis of human breast cancer cells

Herbal extracts used for the alleviation of postmenopausal symptoms might have a lower risk of breast cancer development than hormone therapy. Serelys^® is a product composed of purified pollen cytoplasm extracts. Recent experimental data revealed that estrogens might trigger a further proliferative effect on breast cancer cells via the progesterone receptor membrane component-1 (PGRMC1) in addition to the proliferative effect via intracellularly located receptors. MCF-7 and T47D cells were stably transfected with PGRMC1. Different concentrations of the extract alone and in combination with fixed concentrations of estradiol or a growth factor mixture were tested. Proliferation of treated cells was determined by the 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl-tetrazolium bromide (MTT)-test and apoptosis was determined using a Cell Death Detection ELISA kit (CDD). Serelys^® was neutral in the cell lines transfected or not transfected with PGRMC1. It was also neutral in combination with estradiol or growth factors in terms of cell proliferation and cell apoptosis. Thus in contrast to hormone therapy Serelys^® appears to trigger no further breast cancer risk when applied in the post menopause to women, who do or do not overexpress PGRMC1. Overall Serelys^® may be an effective alternative for alleviating postmenopausal symptoms without increasing breast cancer risk.

May progesterone receptor membrane component 1 (PGRMC1) predict the risk of breast cancer?

OBJECTIVE

Our and other studies have pointed on an important role of progesterone receptor membrane component 1 (PGRMC1) in development of breast cancer, especially in hormone therapy. To investigate if PGRMC1 could be used to predict the risk for getting breast cancer, we assessed in tissues of patients with primary invasive breast cancer, if the expression of PGRMC1 may be associated with the expression of estrogen receptor alpha (ERα), progesterone receptor (PR), and ki67.

METHODS

Samples from 109 patients with breast cancer between the years 2008 and 2014 were obtained with the patients' consent. Each sample was evaluated for the ERα, PR, Ki67, and PGRMC1 expression by immunohistochemistry using serial sections from the ame paraffin block comparing malignant tissue to benign tissue.

RESULTS

Expression of PGRMC1 is increased in tumor area compared with non-cancerous tissue and positively correlates with ERα expression (OR = 1.42 95%CI 1.06-1.91, p = 0.02). No association was obtained between expression of PGRMC1 and PR or Ki67.

CONCLUSION

It can be suggested that women with breast epithelium highly expressing PGRMC1 and in interaction with ERα may have an increased risk to develop breast cancer, especially when treated with hormone therapy.

Impact of smoking on estrogenic efficacy

Depending on the type, duration and intensity of cigarette smoking, the efficacy of endogenous and exogenous estrogen can be reduced or completely cancelled. Not only does smoking diminish the beneficial effects of estrogen on hot flushes and urogenital symptoms and its positive effects on lipid metabolism, but smoking also can reduce estrogen's ability to prevent osteoporosis and perhaps also cardiovascular diseases. This is mainly caused by dose-dependent elevated hepatic clearance, partially in conjunction with lower estrogen levels, and has been demonstrated so far only with oral estrogen applications. Compensation for the failure of therapeutic action should not be made by increasing the dose in smokers since this might result in the production of potentially mutagenic estrogen metabolites associated with a higher risk of breast cancer. Since the favorable effects of estrogens seem to be not lost in smokers when estrogens are applied transdermally, this route should be preferred in smokers. The most important conclusion from the data presented is that the effects of smoking are very complex and dependent on a multiplicity of factors, so that different types of clinically relevant negative effects must be expected. Women who continue to smoke despite all warnings should be informed that smoking, in addition to all its other negative effects, can also jeopardize the success of hormone replacement therapy.

Medroxyprogesterone acetate-driven increase in breast cancer risk might be mediated via cross-talk with growth factors in the presence of progesterone receptor membrane component-1

BACKGROUND

The WHI trial suggests an increase of breast cancer in postmenopausal women probably according to the progestogenic compound, i.e. medroxyprogesterone acetate (MPA). However, the mechanism for a possible carcinogenic effect of MPA remains unclear so far. Progesterone receptor membrane component-1 (PGRMC1) may be important in tumorigenesis and thus may increase breast cancer risk. We investigated the influence of MPA alone and in combination with growth factors on breast cancer cells overexpressing PGRMC1.

METHODS

MCF-7 cells were stably transfected with PGRMC1 expression plasmid (WT-12 cells). Cells transfected only with the vector were used as control cells (EVC-cells). Medroxyprogesterone acetate (MPA), norethisterone (NET) and progesterone (P) were tested alone and in combination with a mixture of growth factors. Cell proliferation was measured by MTT assay.

RESULTS

The growth factor mixture (GF) was able to induce cell proliferation in both cell types, however, the effect was much higher in the WT-12 cells. In WT-12 cells both MPA and NET alone significantly increased cell proliferation with values of 40% and 97%, respectively. Progesterone, however, had no effect. In combination with GF MPA significantly further enhanced cell proliferation as compared to the effect of MPA alone and GF alone in both cell lines. NET showed no further increase as compared to NET alone and P had no effect.

CONCLUSIONS

We could demonstrate a significant proliferative effect of MPA when combined with high concentrations of growth factors. This effect was more pronounced in breast cancer cells overexpressing PGRMC1. These results may be of clinical relevance since in the combined WHI trial an increased breast cancer risk was found during treatment with conjugated equine estrogens plus MPA.

Possible role of PGRMC1 in breast cancer development

Hormone therapy may increase the risk of breast cancer. Thus, especially the addition of synthetic progestins may play a decisive role according to the results of clinical studies. Overexpression of a special receptor, i.e. the progesterone receptor membrane component-1 (PGRMC1), may offer a potential new pathway to explain the observed increase in breast cancer risk in the combined arm of the Women's Health Initiative. PGRMC1 is expressed in breast cancer tissue and may be important in tumorigenesis. The expression of PGRMC1 in breast cancer tissue is significantly different from that in normal mammary glands. Certain synthetic progestins can increase the proliferation of PGRMC1-overexpressing breast cancer cells and may thus be involved in tumorigenesis, while progesterone and certain synthetic progestins such as nomegestrol or chlormadinone acetate react neutrally. Our investigations point towards an important role of estrogen receptor-α in the signaling cascade, resulting in the proliferative effect induced by progestins. Thus, activation of PGRMC1 may explain the increased breast cancer risk observed during treatment with certain progestins. Very recently, PGRMC1 was investigated in serum samples of lung cancer patients and matched healthy patients; significantly higher concentrations were shown in the cancer patients. Therefore, PGRMC1 might be a predictor for other cancers as well but, according to clinical trials, its importance for a possible screening tool, particularly for breast cancer risk during hormone therapy, seems of interest.

Membrane-receptor initiated proliferative effects of dienogest in human breast cancer cells

OBJECTIVES

Dienogest (DNG) is already used in hormone therapy, since recently being also the progestogenic component of the first estradiol based contraceptive pill. Data on breast cancer risk are currently not available. Progesterone receptor membrane component 1 (PGRMC1) is highly expressed in tissues of breast cancer patients and has already been proposed as a predictor for breast cancer risk.

METHODS

MCF-7 cells overexpressing PGRMC1 were stimulated with DNG, medroxyprogesterone acetate (MPA), norethisterone (NET) and progesterone (P) as well as sequentially and continuously combined with estradiol (E2).

RESULTS

DNG and MPA alone elicited a significant proliferation at 10⁻⁶ and 10⁻⁵ M. NET increased cell proliferation at all concentrations tested whereas P showed no effect. E2 alone elicited a significant increase at 10⁻¹⁰ M, no effect was seen at 10⁻¹² M. Addition of the progestins (10⁻⁶ M) to E2 at 10⁻¹⁰ M had, compared to E2 only, no additional proliferating effect. However, at the low E2 concentration, DNG, MPA and NET significantly increased the E2-stimulated cell proliferation.

CONCLUSION

DNG increased proliferation alone and in combination with low E2 concentrations. Thus a progestogen-derived breast cancer risk in the presence of low E2 concentrations cannot be excluded at least in women overexpressing PGRMC1.

Nomegestrol acetate sequentially or continuously combined to estradiol did not negatively affect membrane-receptor associated progestogenic effects in human breast cancer cells

OBJECTIVES

Recently the first monophasic contraceptive pill containing estradiol has been developed which is thought to be a milestone in contraception. Nomegestrol acetate (NOM) is the progestogenic component. Progesterone receptor membrane component 1 (PGRMC1) is highly expressed in the tissue of breast cancer patients, and can predict a progestogen dependent risk of breast cancer.

METHODS

MCF-7 cells were transfected with PGRMC1 expression plasmid, and were stimulated with estradiol (E2, 10(-12) and 10(-10) M). NOM, progesterone (P), medroxyprogesterone acetate (MPA) and norethisterone (NET) (each 10(-7) M) were added sequentially or continuously.

RESULTS

E2 at 10(-10) M elicited a significant increase of cell proliferation from 150 to 200%. No effect was seen at 10(-12) M. Addition of the progestogens to E2 at 10(-10) M had no significant effect. However, at an E2 10(-12) M, NET significantly stimulated cell proliferation more pronounced in the continuous combined model. No effect was seen for NOM, P and MPA. The E2/NET combined effect could be abrogated by the addition of an estrogen receptor (ER) antagonist.

CONCLUSION

Since NOM did not increase proliferation it may be concluded that it will be neutral in terms of breast cancer risk when combined with E2 at least in women overexpressing PGRMC1.