Regulation of fas ligand expression in breast cancer cells by estrogen: functional differences between estradiol and tamoxifen

Estrogen receptor regulation of the immune microenvironment in breast cancer

Breast cancer (BCa) is the most common cancer in women and the estrogen receptor (ER)+ subtype is increasing in incidence. There are numerous therapy options available for patients that target the ER, however issues such as innate and acquired treatment resistance, and treatment related side effects justify research into alternative therapeutic options for these patients. Patients of many solid tumour types have benefitted from immunotherapy, however response rates have been generally low in ER+ BCa. We summarise the recent work assessing CDK4/6 inhibitors for ER+ BCa and how they have been shown to prime anti-tumour immune cells and achieve impressive results in preclinical models. A great example of how the immune system might be activated against ER+ BCa. We review the role of estrogen signalling in immune cells, and explore recent data highlighting the hormonal regulation of the immune microenvironment of normal breast, BCa and immune disorders. As recent data has indicated that macrophages are particularly susceptible to estrogen signalling, we highlight macrophage phagocytosis as a key potential target for priming the tumour immune microenvironment. We challenge the generally accepted paradigm that ER+ BCa are "immune-cold" - advocating instead for research into therapies that could be used in combination with targeted therapies and/or immune checkpoint blockade to achieve durable antitumour responses in ER+ BCa.

Hormone Receptor Signaling and Breast Cancer Resistance to Anti-Tumor Immunity

Breast cancers regroup many heterogeneous diseases unevenly responding to currently available therapies. Approximately 70-80% of breast cancers express hormone (estrogen or progesterone) receptors. Patients with these hormone-dependent breast malignancies benefit from therapies targeting endocrine pathways. Nevertheless, metastatic disease remains a major challenge despite available treatments, and relapses frequently ensue. By improving patient survival and quality of life, cancer immunotherapies have sparked considerable enthusiasm and hope in the last decade but have led to only limited success in breast cancers. In addition, only patients with hormone-independent breast cancers seem to benefit from these immune-based approaches. The present review examines and discusses the current literature related to the role of hormone receptor signaling (specifically, an estrogen receptor) and the impact of its modulation on the sensitivity of breast cancer cells to the effector mechanisms of anti-tumor immune responses and on the capability of breast cancers to escape from protective anti-cancer immunity. Future research prospects related to the possibility of promoting the efficacy of immune-based interventions using hormone therapy agents are considered.

Selective estrogen receptor modulators contribute to prostate cancer treatment by regulating the tumor immune microenvironment

Prostate cancer (PC) has previously been established as a cold tumor and develops in an inert immunosuppressive environment. Current research focuses on altering the immune microenvironment of PC from cold to hot; thus, in the present review, the diverse roles of estrogen and estrogen receptor (ER) signaling was examined in the tumor cell and tumor immune microenvironment (TIM). We hypothesized that ERα promotes PC progression and ERβ impedes epithelial-mesenchymal transition in PC cells, while in the TIM, ERβ mediates the immunosuppressive environment, and low levels of ERα is associated with disease development. Selective estrogen receptor modulators (SERMs) or selective ER degraders play diverse roles in the regulation of ER isoforms. Patients with PC may benefit from the use of SERMs, including raloxifene, in combination with anti-PD1/PD-L1 checkpoint immunotherapy, or TGF-β or Wnt antagonists. The present review demonstrated that immunotherapy-based strategies combined with SERMs may be an option for the future of PC-targeting therapy.

The immunomodulatory effects of endocrine therapy in breast cancer

Endocrine therapies with SERMs (selective estrogen receptor modulators) or SERDs (selective estrogen receptor downregulators) are standard therapies for patients with estrogen receptor (ER)-positive breast cancer. Multiple small molecule inhibitors targeting the PI3K-AKT-mTOR pathway or CDK4/6 have been developed to be used in combination with anti-estrogen drugs to overcome endocrine resistance. In addition to their direct antitumor effects, accumulating evidence has revealed the tumor immune microenvironment (TIM)-modulating effects of these therapeutic strategies, which have not been properly acknowledged previously. The immune microenvironment of breast tumors plays a crucial role in tumor development, metastasis and treatment response to endocrine therapy and immunotherapy. Therefore, in our current work, we comprehensively review the immunomodulatory effect of endocrine therapy and discuss its potential applications in combination with immune checkpoint inhibitors in breast cancer treatment.

A Computational Statistics Approach to Evaluate Blood Biomarkers for Breast Cancer Risk Stratification

Breast cancer is the second leading cause of cancer mortality among women. Mammography and tumor biopsy followed by histopathological analysis are the current methods to diagnose breast cancer. Mammography does not detect all breast tumor subtypes, especially those that arise in younger women or women with dense breast tissue, and are more aggressive. There is an urgent need to find circulating prognostic molecules and liquid biopsy methods for breast cancer diagnosis and reducing the mortality rate. In this study, we systematically evaluated metabolites and proteins in blood to develop a pipeline to identify potential circulating biomarkers for breast cancer risk. Our aim is to identify a group of molecules to be used in the design of portable and low-cost biomarker detection devices. We obtained plasma samples from women who are cancer free (healthy) and women who were cancer free at the time of blood collection but developed breast cancer later (susceptible). We extracted potential prognostic biomarkers for breast cancer risk from plasma metabolomics and proteomics data using statistical and discriminative power analyses. We pre-processed the data to ensure the quality of subsequent analyses, and used two main feature selection methods to determine the importance of each molecule. After further feature elimination based on pairwise dependencies, we measured the performance of logistic regression classifier on the remaining molecules and compared their biological relevance. We identified six signatures that predicted breast cancer risk with different specificity and selectivity. The best performing signature had 13 factors. We validated the difference in level of one of the biomarkers, SCF/KITLG, in plasma from healthy and susceptible individuals. These biomarkers will be used to develop low-cost liquid biopsy methods toward early identification of breast cancer risk and hence decreased mortality. Our findings provide the knowledge basis needed to proceed in this direction.

Regulatory B lymphocytes: development and modulation of the host immune response during disease

The role of B lymphocytes (B cells) in immunogenic responses has become increasingly important over the past decade, focusing on a new B-cell subtype: regulatory B-cells (Bregs). These Bregs have been shown to possess potent immunosuppressive activities and have identified as key players in disease control and immune tolerance. In this review, the occurrence of Breg type in various conditions, along with evidence supporting discovered functions and proposed purposes will be explored. An example of such regulatory functions includes the induction or suppression of various T lymphocyte phenotypes in response to a particular stimulus. Should Bregs prove effective in mediating immune responses, and correlate with favorable disease outcome, they may serve as a novel therapeutic to combat disease and prevent infection. However, the induction, function and stability of these cells remain unclear and further investigation is needed to better understand their role and therapeutic efficacy.

Regulatory effects of miRNA‑181a on FasL expression in bone marrow mesenchymal stem cells and its effect on CD4+T lymphocyte apoptosis in estrogen deficiency‑induced osteoporosis

Post-menopausal osteoporosis is a bone formation disorder induced by estrogen deficiency. Estrogen deficiency facilitates the differentiation and maturation of osteoclasts by activating T lymphocytes. In our previous study, it was demonstrated that estrogen promotes bone marrow mesenchymal stem cell (BMMSC)‑induced osteoclast apoptosis through downregulation of microRNA (miR)‑181a and subsequent Fas ligand (FasL) protein accumulation. In the present study, the regulatory effects of miR‑181a on FasL expression in BMMSCs and the apoptotic effects of BMMSCs on cluster of differentiation (CD)4+T lymphocytes were investigated. An ovariectomized mouse model of osteoporosis (OVX) was established and CD4+T lymphocytes were isolated from the bones of these mice. The results demonstrated that the number of CD4+T lymphocytes was increased in the OVX group compared within the control group, thus suggesting that estrogen deficiency may increase CD4+T lymphocyte number. CD4+T lymphocytes were subsequently co‑cultured with estrogen‑treated BMMSCs, after which it was demonstrated that estrogen significantly promoted the apoptosis of CD4+T lymphocytes. Western blot analysis indicated that estrogen promoted the apoptosis of CD4+T lymphocytes through regulation of FasL expression in BMMSCs in a concentration‑dependent manner. Finally, miR‑181a was transfected into BMMSCs, which were co‑cultured with CD4+T lymphocytes in vitro and in vivo. The results revealed that miR‑181a exerted a negative regulatory effect on BMMSC‑induced CD4+T lymphocyte apoptosis by regulating FasL protein expression in BMMSCs; this maybe a key mechanism underlying the development of estrogen deficiency‑induced osteoporosis.

Induction of apoptosis in breast cancer cells in vitro by Fas ligand reverse signaling

PURPOSE

The Fas-antigen is a cell surface receptor that transduces apoptotic signals into cells. The purpose of this study was to evaluate FasL expression in breast cancer and to elucidate the role of its signaling in different breast cancer cell lines.

METHODS

T47D and MCF7 cells were used and cultured in Dulbecco's modified Eagle's medium. FasL translocation to the membrane was achieved by culturing the cells in the presence of human interferon-γ (IFNγ). Translocation was detected by immunofluorescence. The ability of a Fas:Fc fusion protein to trigger apoptosis in these cells was investigated by cell death detection ELISA. After incubation with IFNγ for 4 h and 18 h, apoptosis was assessed in response to treatment with Fas:Fc.

RESULTS

Immunofluorescence revealed that the used cell lines were positive for FasL which was increased and changed to more membrane-bound FasL expression after IFNγ stimulation. After stimulation with 50 IU/ml IFNγ, Fas:Fc significantly increased MCF7 apoptosis (1.39 ± 0.06-fold, p = 0.0004) after 18 h. After stimulation with 100 IU/ml, Fas:Fc significantly increased apoptosis both after 4 h (1.49 ± 0.15-fold, p = 0.018) and 18 h (1.30 ± 0.06-fold, p = 0.013). In T47D cells this effect was seen after 4 h of stimulation with 50 IU/ml and addition of Fas:Fc (1.6 ± 0.08-fold, p = 0.03).

CONCLUSION

Membrane-bound FasL expression could be induced by IFNγ in a breast cancer cell model. More importantly, in the presence of IFNγ the Fas:Fc fusion protein was able to transmit pro-apoptotic signals to T47D and MCF7 cells, significantly inducing apoptosis. The current findings support further in vivo studies regarding FasL activation as a potential target for therapeutic intervention in breast cancer.

Anti-cancer effect of Annona Muricata Linn Leaves Crude Extract (AMCE) on breast cancer cell line

Background

Annona muricata Linn which comes from Annonaceae family possesses many therapeutic benefits as reported in previous studies and to no surprise, it has been used in many cultures to treat various ailments including headaches, insomnia, and rheumatism to even treating cancer. However, Annona muricata Linn obtained from different cultivation area does not necessarily offer the same therapeutic effects towards breast cancer (in regards to its bioactive compound production). In this study, anti-proliferative and anti-cancer effects of Annona muricata crude extract (AMCE) on breast cancer cell lines were evaluated.

Methods

A screening of nineteen samples of Annona muricata from different location was determined by MTT assay on breast cancer cell lines (MCF-7, MDA-MB-231, and 4 T1) which revealed a varied potency (IC₅₀) amongst them. Then, based on the IC₅₀ profile from the anti-proliferative assay, further downward assays such as cell cycle analysis, Annexin V/FITC, AO/PI, migration, invasion, and wound healing assay were performed only with the most potent leaf aqueous extract (B1 AMCE) on 4 T1 breast cancer cell line to investigate its anti-cancer effect. Then, the in vivo anti-cancer study was conducted where mice were fed with extract after inducing the tumor. At the end of the experiment, histopathology of tumor section, tumor nitric oxide level, tumor malondialdehyde level, clonogenic assay, T cell immunophenotyping, and proteome profiler analysis were performed.

Results

Annona muricata crude extract samples exhibited different level of cytotoxicity toward breast cancer cell lines. The selected B1 AMCE reduced the tumor’s size and weight, showed anti-metastatic features, and induced apoptosis in vitro and in vivo of the 4 T1 cells. Furthermore, it decreased the level of nitric oxide and malondialdehyde in tumor while also increased the level of white blood cell, T-cell, and natural killer cell population.

Conclusion

The results suggest that, B1 AMCE is a promising candidate for cancer treatment especially in breast cancer and deserves further research as an alternative to conventional drugs while also stressed out the selection of soursop sample which plays a significant role in determining its potential therapeutic effect on cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1290-y) contains supplementary material, which is available to authorized users.

The association between the SNP rs763110 and the risk of gynecological cancer: a meta-analysis

FAS and FAS ligand (FASL) are the principal genes of the apoptosis pathway, which play a vital role in the etiology of various gynecological cancers. Studies have revealed that polymorphism of FASL promoter -844C>T (rs763110) influences FASL transcription process, which involving in cancer risk. Moreover, estrogen has been proved to trigger T-cell apoptosis by up-regulating FAS/FASL system in cancer cells. However, results from the published studies on the association between FASL -844C>T polymorphism and risk of gynecological cancer are conflicting. We performed a meta-analysis based on 13 case-control studies, including a total of 6256 cancer cases and 5573 controls. We used odd ratios (ORs) with 95% confidence intervals (CIs) to assess the association strength. Overall, the FASL -844CT and TT genotypes were associated with a significantly reduced risk of gynecological cancer types in homozygote comparison (OR=0.80, 95% CI=0.64-0.99), heterozygote comparison (OR=0.81, 95% CI=0.67-0.98), and dominant model (OR=0.81, 95% CI=0.67-0.98). In the stratified analyses, we observed a similar association among Asian population (heterozygote comparison: OR=0.73, 95% CI=0.56-0.95; dominant model: OR=0.75, 95% CI=0.57-0.98) and hospital-based studies (homozygote comparison: OR=0.61, 95% CI=0.43-0.86). When stratified by cancer type, there was also a significantly lower risk of the ovarian cancer in different genetic models except the recessive one. The results suggested that the FASL -844C>T polymorphism may reduce the risk of gynecological cancer.

Tamoxifen integromics and personalized medicine: dynamic modular transformations underpinning response to tamoxifen in breast cancer treatment

Recent advances in pharmacogenomics technologies allow bold steps to be taken towards personalized medicine, more accurate health planning, and personalized drug development. In this framework, systems pharmacology network-based approaches offer an appealing way for integrating multi-omics data and set the basis for defining systems-level drug response biomarkers. On the road to individualized tamoxifen treatment in estrogen receptor-positive breast cancer patients, we examine the dynamics of the attendant pharmacological response mechanisms. By means of an "integromics" network approach, we assessed the tamoxifen effect through the way the high-order organization of interactome (i.e., the modules) is perturbed. To accomplish that, first we integrated the time series transcriptome data with the human protein interaction data, and second, an efficient module-detecting algorithm was applied onto the composite graphs. Our findings show that tamoxifen induces severe modular transformations on specific areas of the interactome. Our modular biomarkers in response to tamoxifen attest to the immunomodulatory role of tamoxifen, and further reveal that it deregulates cell cycle and apoptosis pathways, while coordinating the proteasome and basal transcription factors. To the best of our knowledge, this is the first report that informs the fields of personalized medicine and clinical pharmacology about the actual dynamic interactome response to tamoxifen administration.

Oestradiol enhances apoptosis in bovine mammary epithelial cells in vitro

Ovarian steroids, oestradiol and progesterone, are required for normal mammary growth at puberty and during pregnancy. They contribute to mammary parenchyma development by stimulating mammary epithelial cell (MEC) proliferation. However several studies demonstrate that oestradiol negatively affects milk production during the declining phase of lactation, but the oestradiol effect on MEC in lactating mammary gland remains unclear. The objective of this study was to investigate the differential effect of oestradiol on bovine MECs mimicking two physiological statuses: active and early apoptotic MECs. We demonstrated that oestradiol has a major effect on early apoptotic MECs and might accelerate MEC apoptosis by activation of caspases rather than by inducing apoptosis in active MECs. Early apoptotic MECs could be compared with senescent cells in the late-lactation mammary gland. These results suggest that the negative effect of oestradiol on milk production during the declining phase of lactation would be due to an enhancement of apoptotic processes in MECs.

Evaluation of FAS and caspase-3 in the endometrial tissue of patients with idiopathic infertility and recurrent pregnancy loss

OBJECTIVE

To investigate expression of BcL-2, FAS, FAS ligand (FASL) and cleaved caspase-3 in the endometrial tissue of women with idiopathic infertility (with two consecutive failed cycles of in vitro fertilization) and women with idiopathic recurrent pregnancy loss. The control group consisted of fertile women.

STUDY DESIGN

Endometrial tissue samples from fertile women (n=25), women with idiopathic infertility (n=25) and women with idiopathic recurrent pregnancy loss (n=25) were collected on the seventh or eighth postovulatory day of their menstrual cycles for evaluation. Expression of BcL-2, FAS, FASL and cleaved caspase-3 was assessed using immunohistochemical methods.

RESULTS

Expression of BcL-2 and FAS was significantly higher and lower, respectively, in the women with idiopathic infertility than in the other groups (p<0.01). Expression of cleaved caspase-3 was significantly lower in the women with idiopathic infertility than in the other groups (p<0.01). Expression of FASL was similar in all three groups.

CONCLUSION

Disturbances in endometrial apoptosis may be a contributing factor in patients with idiopathic infertility and recurrent pregnancy loss.

FASL-844 T/C polymorphism: a biomarker of good prognosis of breast cancer in the Tunisian population

The single nucleotide polymorphism, rs763110 (-844 T/C) of the FASL gene, is located within a putative binding motif of CAAT/enhancer-binding protein β transcription factor. Higher basal expression of FASL is significantly associated with the FASL-844 C allele compared with the FASL-844 T allele suggesting that the FASL-844 T/C polymorphism may influence FASL expression and FASL-mediated signalling, and ultimately, the susceptibility to cancer. Therefore, we carried out a population-based study to estimate the FASL-844 C allele frequency in our population and to investigate, in a case-control study, the potential association of the FASL-844 T/C polymorphism with the risk and prognosis of breast cancer in Tunisia. FASL-844 T/C polymorphism was examined in a Tunisian population-based case-control of 438 patients with breast cancer and 332 control subjects using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. By using TT genotype as reference, no significant association was found between any genotype and the risk of developing breast cancer. The frequency of the FASL-844 C allele was 46.3% among the cases and 43.7% among the controls. Similarly, by using T allele as reference, this difference was also not statistically significant. We observed FASL-844 CC genotype and FASL-844 C allele were significantly associated with SBR 1-2 tumour grade (OR=0.42, P=0.007; OR=0.65, P=0.005, respectively). In patients with diagnosis age ≤ 50 years, FASL-844 CC genotype and C allele showed significant associations with T(1)-T(2) clinical tumour size (OR=0.34, P=0.01; OR=0.65, P=0.02, respectively) and SBR grade 1-2 (OR=0.41, P=0.02; OR=0.62, P=0.01, respectively). A marginally significant association was also found with negative nodal status (OR=0.53, P=0.06; OR=0.73, P=0.07, respectively). Thus, the FASL-844 CC genotype and C allele seem to be associated with a good prognosis in patients with diagnosis age ≤ 50 years.

Estrogens and prostate cancer: etiology, mediators, prevention, and management

The mainstay targets for hormonal prostate cancer (PCa) therapies are based on negating androgen action. Recent epidemiologic and experimental data have pinpointed the key roles of estrogens in PCa development and progression. Racial and geographic differences, as well as age-associated changes, in estrogen synthesis and metabolism contribute significantly to the etiology. This article summarizes how different estrogens/antiestrogens/estrogen mimics contribute to prostate carcinogenesis, the roles of the different mediators of estrogen in the process, and the potentials of new estrogenic/antiestrogenic compounds for prevention and treatment of PCa.

Clinical review: Effect of endocrine therapies on bone in breast cancer patients

CONTEXT

Two common strategies are used to treat estrogen receptor-positive breast cancer in women: tamoxifen to inhibit estrogen action, and aromatase inhibitors (AIs) to block estrogen biosynthesis. Recent data suggest that AIs are more effective than tamoxifen in the adjuvant and advanced disease settings and are now being more commonly used. Tamoxifen, as a selective estrogen receptor modulator, exerts estrogenic effects to preserve bone, whereas the AIs profoundly lower estrogen levels and cause bone loss. Recent comparative studies of these agents provide extensive data on fracture rates, bone mineral density, and markers of bone formation and resorption.

OBJECTIVE

The aim of the study was to review the mechanistic effects of estrogen on bone and clinical data regarding bone density, bone turnover markers, and fracture rates in women with breast cancer taking tamoxifen or AIs.

EVIDENCE ACQUISITION AND SYNTHESIS

Data presented reflect a review of the literature and data integration from the perspective of the author's knowledge of the field.

RESULTS

Tamoxifen increases bone density and reduces fractures in postmenopausal women with breast cancer, whereas AIs increase rate of fracture, accelerate loss of bone mineral density, and enhance levels of markers of bone formation and resorption. Bisphosphonates and denosumab counteract the effects of the AIs on bone. Guidelines for management of AI-induced bone loss are available from several sources, but a simple algorithm guides decision making most effectively.

CONCLUSIONS

Endocrine therapy for postmenopausal women with breast cancer exerts substantial effects on bone, and guidelines are available to assist in the management of bone-related problems.

Oestrogen treatment enhances the sensitivity of hormone-resistant breast cancer cells to doxorubicin

Recently, it was shown that the resistance of breast cancer cells to growth-stimulating oestrogen action may be accompanied with the paradoxical tumour sensitization to oestrogen apoptotic action. In the present paper, we studied the influence of oestrogens on the sensitivity of resistant breast tumours to cytostatic drugs, and to evaluate the role of NF-κB (nuclear factor κB) signalling in the regulation of the apoptotic response of the resistant cells. The experiments were carried out on the oestrogen-dependent MCF-7 breast cancer cells and resistant MCF-7/LS subline generated through long-term cultivation of the parental cells in the absence of oestrogen. The cell treatment with the combination of oestradiol and Dox (doxorubicin) was found to enhance the apoptotic action of Dox in MCF-7/LS cells but not in the parent cells. MCF-7/LS cells were characterized by the increased level of ROS (reactive oxygen species) and decreased NF-κB activity. Oestradiol in combination with Dox leads to significant NF-κB stimulation and its accumulation in the nucleus of MCF-7/LS cells. The knockdown of NF-κB with siRNA (small interfering RNA) increased the apoptotic response of the MCF-7/LS cells to both Dox and oestradiol demonstrating the important role of NF-κB in the protection of the MCF-7/LS cells against apoptosis. In general, the results obtained show that: (i) oestradiol enhances the apoptotic action of Dox in the resistant breast cancer cells; and (ii) suppression of NF-κB signalling amplifies the apoptotic response of the resistant cells to both oestrogen and Dox, demonstrating that NF-κB may serve as a potential target in the therapy of the resistant breast cancer.

Estrogen regulation of apoptosis: how can one hormone stimulate and inhibit?

The link between estrogen and the development and proliferation of breast cancer is well documented. Estrogen stimulates growth and inhibits apoptosis through estrogen receptor-mediated mechanisms in many cell types. Interestingly, there is strong evidence that estrogen induces apoptosis in breast cancer and other cell types. Forty years ago, before the development of tamoxifen, high-dose estrogen was used to induce tumor regression of hormone-dependent breast cancer in post-menopausal women. While the mechanisms by which estrogen induces apoptosis were not completely known, recent evidence from our laboratory and others demonstrates the involvement of the extrinsic (Fas/FasL) and the intrinsic (mitochondria) pathways in this process. We discuss the different apoptotic signaling pathways involved in E2 (17beta-estradiol)-induced apoptosis, including the intrinsic and extrinsic apoptosis pathways, the NF-kappaB (nuclear factor-kappa-B)-mediated survival pathway as well as the PI3K (phosphoinositide 3-kinase)/Akt signaling pathway. Breast cancer cells can also be sensitized to estrogen-induced apoptosis through suppression of glutathione by BSO (L-buthionine sulfoximine). This finding has implications for the control of breast cancer with low-dose estrogen and other targeted therapeutic drugs.

The FAS ligand promoter polymorphism, rs763110 (-844C>T), contributes to cancer susceptibility: evidence from 19 case-control studies

The potentially functional polymorphism, rs763110 (-844C>T), in the promoter region of the FAS ligand (FASL) gene, has been implicated in cancer risk, but individually published studies show inconclusive results. To derive a more precise estimation of the association between the FASL rs763110 and risk of cancer, we performed a meta-analysis of 19 published studies that included 11,105 cancer cases and 11,372 controls. We used odds ratios (ORs) and 95% confidence intervals (CIs) to assess the strength of the associations. Overall, the rs763110 CT and TT variant genotypes were associated with a significantly reduced cancer risk of all cancer types in different genetic models (homozygote comparison: OR=0.80, 95% CI: 0.68-0.95, P(heterogeneity)=0.001; heterozygote comparison: OR=0.82, 95% CI: 0.72-0.95, P(heterogeneity)<0.001; dominant model comparison: OR=0.82, 95% CI: 0.71-0.94, P(heterogeneity)<0.001; and recessive model comparison: OR=0.88, 95% CI: 0.81-0.96, P(heterogeneity)=0.074). In the stratified analyses, the risk remained for studies of the smoking-related cancers and Asian populations, or population-based studies in all the genetic models. Although some modest bias could not be eliminated, this meta-analysis suggests that the FASL rs763110 T allele has a possible protective effect on cancer risk.

Steroid hormones and carcinogenesis of the prostate: the role of estrogens

Androgens have long been known to be the major sex hormones that target the prostate during development, maturation, and carcinogenesis. It is now apparent that estrogens, both those synthesized by the body as well as those from our environment, also target the prostate during all stages of development. Little is known about the mechanisms involved in estrogen stimulation of carcinogenesis and less is known about how to prevent or treat prostate cancer through estrogenic pathways. To better understand how estrogens mediate their carcinogenic effects, the respective roles of estrogen receptor (ER)-alpha and ER-beta must be elucidated in the epithelial and stromal cells that constitute the prostate. Lastly, the significance of ER signaling during various ontogenic periods must be determined. Answers to these questions will further our understanding of the mechanisms of estrogen/ER signaling and will serve as a basis for chemopreventive and/or chemotherapeutic strategies for prostate cancer.

Mechanism of estrogen-induced apoptosis in breast cancer cells: role of the NF-kappaB signaling pathway

The ability of sex steroid hormones to up-regulate the apoptotic signaling proteins is well documented; however, the apoptotic potential of sex hormones is not remarkable and fully compensated by their growth stimulatory action to target cells. In the present study using the long-term cultivation of estrogen-dependent MCF-7 breast cancer cells in steroid-free medium, we have established a cell subline, designed as MCF-7/LS, which was characterized by the resistance to growth stimulatory estradiol action and hypersensitivity to estrogen-induced apoptosis. We have demonstrated that estrogen treatment of the cells does not influence on the level of TNF-R1 or Fas, but dramatically decreases the transcriptional activity of NF-kappaB. Importantly, the MCF-7/LS cells, which are insensitive to growth stimulatory estrogen action, retain the ability to decrease in the NF-kappaB activity in response to estrogen stimulus. Furthermore, the significant increase in the basal (in the absence of ligand) estrogen receptor (ER)-dependent transcriptional activity in the MCF-7/LS cells was revealed and reciprocal transcriptional antagonism between ER and NF-kappaB was demonstrated. Finally, we proved the possible involvement of phosphatidylinositol-3 kinase (PI3K) in the ligand-independent ER activation. In general, the results presented suggest that long-term growth of MCF-7 breast cancer cells in steroid-free medium is accompanied with the increase in the basal ER-dependent transcriptional activity as well as the maintenance of the negative regulatory loop ER-NF-kappaB. The latter may be considered as one of the factors resulting in a disbalance between pro- and anti-apoptotic pathways and enhancement in estrogen apoptotic action in the cells.

Intratumoral CRH modulates immuno-escape of ovarian cancer cells through FasL regulation

Although corticotropin-releasing hormone (CRH) and Fas ligand (FasL) have been documented in ovarian carcinoma, a clear association with tumour progression and immuno-escape has not been established. FasL plays an important role in promoting tumour cells' ability to counterattack immune cells. Here, we examined immunohistochemically the expression of CRH, CRHR1, CRHR2 and FasL in 47 human ovarian cancer cases. The ovarian cancer cell lines OvCa3 and A2780 were further used to test the hypothesis that CRH might contribute to the immune privilege of ovarian tumours, by modulating FasL expression on the cancer cells. We found that CRH, CRHR1, CRHR2 and FasL were expressed in 68.1, 70.2, 63.8 and 63.8% of the cases respectively. Positivity for CRH or FasL expression was associated with higher tumour stage. Finally, CRH increased the expression of FasL in OvCa3 and A2780 cells through CRHR1 thereby potentiated their ability to induce apoptosis of activated peripheral blood lymphocytes. Corticotropin-releasing hormone produced by human ovarian cancer might favour survival and progression of the tumour by promoting its immune privilege. These findings support the hypothesis that CRHR1 antagonists could potentially be used against ovarian cancer.

Estrogens and Antiestrogens as Etiological Factors and Therapeutics for Prostate Cancer

Mounting evidence supports a key role played by estrogen or estrogen in synergy with an androgen, in the pathogenesis of prostate cancer (PCa). New experimental data suggest that this process could begin as early as prenatal life. During adulthood, estrogen carcinogenicity is believed to be mediated by the combined effects of hormone-induced, unscheduled cell proliferation and bioactivation of estrogens to genotoxic carcinogens. Increased bioavailability of estrogen through age-dependent increases in conversion from androgen could also be a contributing factor. Individual variations and race-/ethnic-based differences in circulating or locally formed estrogens or in tissue estrogen responsiveness may explain differential PCa risk among individuals or different populations. Estrogen receptor (ER)-alpha and ER-beta are the main mediators of estrogen action in the prostate. However, ER-beta is the first ER subtype expressed in the fetal prostate. During cancer development, ER-beta expression is first lost as tumors progress into high grade in the primary site. Yet, its reexpression occurs in all metastatic cases of PCa. A change in cytosine methylation in a regulatory CpG island located in the proximal promoter of ER-beta may constitute an "on/off" switch for reversible regulation of ER-beta expression. A variety of estrogenic/antiestrogenic/selective estrogen receptor modulator (SERM)-like compounds have been shown to use non-ERE pathways, such as tethering of ER-beta to NF-kappaB binding proteins, Sp2, or Ap1 for gene transactivation. These findings open new avenues for drug design that now focuses on developing a new generation of estrogen-based PCa therapies with maximal proapoptotic action but few or no side effects.

Induction of apoptosis in murine fetal thymocytes following perinatal exposure to diethylstilbestrol

Perinatal exposure to diethylstilbestrol (DES) is known to cause thymic atrophy in mice, although the precise mechanism remains unclear. In the current study the authors investigated whether perinatal exposure to DES would trigger apoptosis in thymocytes. To this end, C57BL/6 pregnant mice were injected intraperitoneally (i.p.) on gestational day (gd)-15 and -16 with 5 microg/kg DES. Analysis of thymi harvested from mice on gd-17, gd-19 and postnatal day (PD)-1, showed a significant reduction in thymic cellularity on gd-17 only. Additionally, DES treatment significantly altered the proportion and absolute number of T-cell subsets, particularly on gd-17. Apoptosis was increased in DES-treated thymocytes when compared to the controls and was seen only on gd-17. Moreover, DES-treated gd-17 thymocytes had increased Asp-Glu-Val-Asp (DEVDase) activity. Microarray analysis of 96 apoptotic genes in gd-17 thymocytes revealed that exposure to DES increased the expression of several apoptotic genes primarily belonging to tumor necrosis factor (TNF) and TNF receptor (TNFR) family. Taken together, these results suggest that DES-induced thymic atrophy following perinatal exposure may result, at least in part, from increased apoptosis mediated by death receptor pathway involving TNF family members.

Why do some breast cancer cells remain dormant?

Dormant breast cancer cells are a reality that cannot be overlooked. They may stay dormant either after a spread of cancer cells caused by surgery or after being generated by spontaneous or induced mutations in the course of breast gland growth. Some cases are presented in support of both possibilities, followed by a critical appraisal of the factors that may either keep them dormant or later stimulate their growth into a breast cancer.

Comparison of possible carcinogenic estradiol metabolites: Effects on proliferation, apoptosis and metastasis of human breast cancer cells

OBJECTIVES

Certain estradiol metabolites may play a pivotal role in breast carcinogenesis. Of special interest are the metabolites 2-hydroxyestradiol (2-OHE2), which can react anti-carcinogenically, and 4-hydroxyestradiol (4-OHE1) and 16a-hydroxyestrone (16-OHE1), which may have procarcinogenic potential. In the present study, we have compared for the first time the effect of these metabolites and their parent substance 17beta-estradiol (E2) on proliferation, apoptosis, apoptosis markers and markers of metastatic property of human breast cancer cells.

METHODS

MCF-7 cells (human estrogen-receptor positive metastatic breast cancer cell line) were incubated with the estrogens at concentrations of 0.1-100 nM. Cell proliferation rate was measured by the ATP-assay. Apoptosis was measured by cell death assay and the apoptosis markers cytochrome C, Bcl-2, Fasl and p53 were determined in cell lysates by ELISAs. The markers of metastatic property of the cell line, VEGF and MCP-1 were measured in the cell supernatant by ELISAs.

RESULTS

The estrogens E2, 4-OHE2 and 16-OHE1 display a proliferative effect on MCF-7 cells which is accompanied by a down-regulation of apoptosis. Various markers of apoptosis such as Bcl-2, cytochrome C and p53 appear to be involved. No significant effect was found for the metabolite 2-OHE2. VEGF and MCP-1 were up-regulated by E2 and 16-OHE1, whereas 2-OHE2 and 4-OHE2 did not show any effect.

CONCLUSIONS

The most potent estrogen regarding proliferation, apoptosis and metastasis of breast cancer cells seems to be estradiol. However, the estradiol metabolites 4-OHE2 and 16-OHE1 elicit similar properties on cell proliferation, apoptosis and metastasis as compared to estradiol but only at higher concentrations. In contrast 2-OHE2 did not show any significant effect on these parameters. Thus, intracellular estradiol metabolism may determine an individual's risk for breast carcinogenesis.

Sexual dimorphism in immune response genes as a function of puberty

BACKGROUND

Autoimmune diseases are more prevalent in females than in males, whereas males have higher mortality associated with infectious diseases. To increase our understanding of this sexual dimorphism in the immune system, we sought to identify and characterize inherent differences in immune response programs in the spleens of male and female mice before, during and after puberty.

RESULTS

After the onset of puberty, female mice showed a higher expression of adaptive immune response genes, while males had a higher expression of innate immune genes. This result suggested a requirement for sex hormones. Using in vivo and in vitro assays in normal and mutant mouse strains, we found that reverse signaling through FasL was directly influenced by estrogen, with downstream consequences of increased CD8+ T cell-derived B cell help (via cytokines) and enhanced immunoglobulin production.

CONCLUSION

These results demonstrate that sexual dimorphism in innate and adaptive immune genes is dependent on puberty. This study also revealed that estrogen influences immunoglobulin levels in post-pubertal female mice via the Fas-FasL pathway.

Spotlight on the role of hormonal factors in the emergence of autoreactive B-lymphocytes

Pathogenic autoimmunity requires a combination of inherited and acquired factors. In as much as hormones influence the sexual dimorphism of the immune system, it is possible that they can initiate or accelerate an autoimmune process, and contribute to gender-biased autoimmune disorders. Not only natural hormones, but also endocrine disruptors, such as environmental estrogens, may act in conjunction with other factors to override immune tolerance to self-antigens. In lupus, murine and human studies demonstrate that female sex hormones are implicated in disease pathogenesis. In the B cell compartment, both prolactin and estrogen are immunomodulators that affect maturation, selection and antibody secretion. Their impact may be based on their capacity to allow autoreactive B cells to escape the normal mechanisms of tolerance and to accumulate in sufficient numbers to cause clinically apparent disease. Both hormones lead to the survival and activation of autoreactive B cells, but they skew B cell maturation towards different directions, with prolactin inducing T cell-dependent autoreactive follicular B cells and estrogen eliciting T cell-independent autoreactive marginal zone B cells. Differential modulation of the cytokine milieu by hormones may also affect the development and activation of specific mature B cell subsets. This novel insight suggests that targeted manipulation of these pathways may represent a promising avenue in the treatment of lupus and other gender-biased autoimmune diseases.

Fas ligand in the uterus of the non-pregnant mouse induces apoptosis of CD4+ T cells

The role of FasL in the reproductive tissues of the non-pregnant mouse may be the induction of apoptosis of activated T cells for the prevention of unwanted inflammatory responses secondary to infection. This study was undertaken to identify cell and tissue types that typically express FasL in the uterus and oviduct of the mouse and to establish whether FasL on the surface of these cells was able to induce T cell apoptosis. FasL in the mouse uterus and oviduct was demonstrated using three independent methods: RT-PCR, Western blot and immunocytochemistry. The protein was present in the epithelial and mesenchymal cells of the uterus and showed a granular pattern in the apical epithelial portion. Although this suggests the presence of vesicles, surface expression was also detected by flow cytometry of isolated uterine cells. Exogenous administration of estradiol and progesterone had no significant effect on the expression and localization of FasL. The ability of uterine cells to induce FasL-dependent apoptosis of activated CD4+T cells was examined by incubation of phytohemagglutinin-treated T cells with cultured uterine cells. TUNEL and flow cytometric analyses showed that CD4+T cells experienced apoptosis after 5h of co-incubation. Neutralizing antibodies inhibited apoptosis demonstrating that a biologically active FasL is present in the reproductive tissues of the mouse. Results indicate that FasL is a biologically active molecule present in epithelial and mesenchymal cells of the uterus and the oviduct of the non-pregnant mouse that might restrain local immune response by induction of apoptosis of CD4+T lymphocytes.

Antiestrogens, aromatase inhibitors, and apoptosis in breast cancer

Antiestrogens have been the therapeutic agents of choice for breast cancer patients whose tumors express estrogen receptors, regardless of menopausal status. Unfortunately, many patients will eventually develop resistance to these drugs. Antiestrogens primarily act by preventing endogenous estrogen from activating estrogen receptors and promoting cell growth, which can ultimately lead to tumor cell death. Understanding the mechanisms by which antiestrogens cause cell death or apoptosis is critical to our efforts to develop ways to circumvent resistance. This article focuses on antiestrogen-induced apoptosis both in vitro and in vivo. We review the clinical utility of both antiestrogens and aromatase inhibitors and their apoptogenic mechanisms in cell culture models. Among the key signaling components discussed are the roles of Bcl-2 family members, several cytokines, and their receptors, p53, nuclear factor kappa B (NFkappaB), IRF-1, phosphatidylinositol 3-kinase (PI3K)/Akt, and specific caspases. Finally, we discuss the evidence supporting a role for apoptotic defects in acquired and de novo antiestrogen resistance.

The Fas/Fas ligand system and cancer: immune privilege and apoptosis

The Fas/FasL system has been suggested to play an important role in the establishment of immune privilege status for tumors by inducing Fas-mediated apoptosis in tumor-specific lymphocytes. However, the role of cell-surface expressed FasL in tumor cell protection has recently become controversial. Our laboratory has focused on the study of the role of the Fas/FasL system in the normal tissue remodeling of the female reproductive tract and in immune-privileged organs. Our studies have demonstrated a connection between sex hormones and the regulation of the Fas/FasL pathway in immune and reproductive cells. More recently, we have investigated the resistance of tumor cells to Fas-mediated apoptosis. We have also characterized a new form of FasL, different from the classical membranal form, which is secreted by ovarian cancer cells. In this review we describe the main techniques used in these studies.

The novel estrogen 17α-20Z-21-[(4-amino)phenyl]-19-norpregna-1,3,5(10),20-tetraene-3,17β-diol induces apoptosis in prostate cancer cell lines at nanomolar concentrations in vitro

Prostate cancer remains the number one cause of noncutaneous cancer, with 220,900 new cases predicted for the year 2003 alone. Of the more promising classes of compounds studied thus far for the treatment of prostate cancer, estrogens of various types have consistently exhibited antitumor activities both in vitro and in vivo. For this reason, we have synthesized and screened a library of unique 17α/11β modified 17β-estradiol (E2) analogues designed for estrogen receptor β (ER-β) specificity and a potential for cytotoxic activity directed toward prostate cancer cells. From this library, the novel compound 17α-20Z-21-[(4-amino)phenyl]-19-norpregna-1,3,5(10),20-tetraene-3,17β-diol (APVE2) was identified as the primary lead, found to induce a high level (&gt;90%) of cell death through an apoptotic mechanism, with an EC50 of 1.4, 2.7, and 16 nm in the LNCaP, PC3, and DU145 cell lines, respectively. APVE2 was found to bind to ER-β, albeit weakly, with an EC50 of 250 nm and a binding activity of 6.2% relative to E2, nearly two orders of magnitude less than the concentration required to induce apoptosis. APVE2 bound preferentially to ER-β by 7-fold over ER-α, and did not induce growth in the MCF-7 cell line, thus indicating that it is not a classical ER agonist. Furthermore, the cytotoxic actions of APVE2 were not reversed by co-treatment with a 50-fold excess E2. In summary, a novel 17 modified estrogen APVE2 was identified as a lead compound, capable of inducing apoptosis in three prostate cancer cell lines at low nanomolar concentrations, through a mechanism inconsistent with an ER-mediated mechanism.

Activated platelets rapidly up-regulate CD40L expression and can effectively mature and activate autologous ex vivo differentiated DC

Background DC are a promising immunotherapeutic for treatment of infectious/malignant disease. For clinical trials, immature DC generated from precursor cells such as monocytes, using serum-free media containing GM-CSF and IL-4, can be matured with specific cytokines/factors. CD40 ligand (CD40L) plays an important role in DC activation/maturation but is not available for clinical applications. These studies evaluated the feasibility of using activated platelets with elevated CD40L surface expression to stimulate autologous DC maturation. Methods Pilot and clinical scale studies were executed using magnetic/centrifugal separation. Monocyte precursors were differentiated to immature DC with GM-CSF and IL-4 and the ability of activated autologous platelets to mature these cells was evaluated on the basis of phenotype and function. Results In small-scale studies, DC cultures stimulated with activated autologous platelets (CD40L-AP), tumor necrosis factor-alpha (TNF-alpha) or soluble CD40L (sCD40L) up-regulated expression of phenotype markers indicative of activation and maturation. CD86 expression was significantly enhanced (P<0.05) by stimulation with either CD40L-AP (75.5+/-14.5%) or sCD40L (80.5%+/-5.3%) compared with immature DC (55.2+/-14.8%), as were CD80 and CD83. Similarly, in large-scale studies using Isolex 300I to enrich for monocytes and platelets for DC generation/maturation on a clinical scale, stimulation with CD40L-AP increased CD86 and CD80 expression as well as the ability to stimulate allogeneic lymphocytes compared with control cultures. Discussion These results demonstrate that thrombin-activated platelets express CD40L and are effective at inducing matured DC with potent immunogenic activity. Furthermore, these studies demonstrate the feasibility of this approach for clinical immunotherapeutic interventions.

Chromosome 17p13.2 transfer reverts transformation phenotypes and fas-mediated apoptosis in breast epithelial cells

Transformation of the human breast epithelial cells (HBEC) MCF-10F with the carcinogen benz(a)pyrene (BP) into BP1-E cells resulted in the loss of the chromosome 17 p13.2 locus (D17S796 marker) and formation of colonies in agar-methocel (colony efficiency (CE)), loss of ductulogenic capacity in collagen matrix, and resistance to anti-Fas monoclonal antibody (Mab)-induced apoptosis. For testing the role of that specific region of chromosome 17 in the expression of transformation phenotypes, we transferred chromosome 17 from mouse fibroblast donors to BP1-E cells. Chromosome 11 was used as negative control. After G418 selection, nine clones each were randomly selected from BP1-E-11neo and BP1-E-17neo hybrids, respectively, and tested for the presence of the donor chromosomes by fluorescent in situ hybridization and polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) analyses. Sensitivity to Fas Mab-induced apoptosis and evaluation of transformation phenotype expression were tested in MCF-10F, BP1-E, and nine BP1-E-11neo and BP1-E-17neo clones each. Six BP1-E-17neo clones exhibited a reversion of transformation phenotypes and a dose dependent sensitivity to Fas Mab-induced apoptosis, behaving similarly to MCF-10F cells. All BP1-E-11neo, and three BP1-E-17neo cell clones, like BP1-E cells, retained a high CE, loss of ductulogenic capacity, and were resistant to all Fas Mab doses tested. Genomic analysis revealed that those six BP1-E-17neo clones that were Fas-sensitive and reverted their transformed phenotypes had retained the 17p13.2 (D17S796 marker) region, whereas it was absent in all resistant clones, indicating that the expression of transformation phenotypes and the sensitivity of the cells to Fas-mediated apoptosis were under the control of genes located in this region.

Estrogens and anti-estrogens: Key mediators of prostate carcinogenesis and new therapeutic candidates

Despite the historical use of estrogens in the treatment of prostate cancer (PCa) little is known about their direct biological effects on the prostate, their role in carcinogenesis, and what mechanisms mediate their therapeutic effects on PCa. It is now known that estrogens alone, or in synergism with an androgen, are potent inducers of aberrant growth and neoplastic transformation in the prostate. The mechanisms of estrogen carcinogenicity could be mediated via induction of unscheduled cell proliferation or through metabolic activation of estrogens to genotoxic metabolites. Age-related changes and race-/ethnic-based differences in circulating or locally formed estrogens may explain differential PCa risk among different populations. Loss of expression of estrogen receptor (ER)-beta expression during prostate carcinogenesis and prevention of estrogen-mediated oxidative damage could be exploited in future PCa prevention strategies. Re-expression of ER-beta in metastatic PCa cells raises the possibility of using ER-beta-specific ligands in triggering cell death in these malignant cells. A variety of new estrogenic/anti-estrogenic/selective estrogen receptor modulator (SERM)-like compounds, including 2-methoxyestradiol, genistein, resveratrol, licochalcone, Raloxifene, ICI 182,780, and estramustine are being evaluated for their potential in the next generation of PCa therapies. Increasing numbers of patients self-medicate with herbal formulations such as PC-SPES. Some of these compounds are selective ER-beta ligands, while most of them have minimal interaction with ER-alpha. Although many may inhibit testosterone production by blockade of the hypothalamal-pituitary-testis axis, the most effective agents also exhibit direct cytostatic, cytotoxic, or apoptotic action on PCa cells. Some of them are potent in interfering with tubulin polymerization, blocking angiogenesis and cell motility, suppressing DNA synthesis, and inhibiting specific kinase activities. Further discovery of other compounds with potent apoptotic activities but minimal estrogen action should promote development of a new generation of effective PCa preventive or treatment regimens with few or no side-effects due to estrogenicity. Further advancement of our knowledge of the role of estrogens in prostate carcinogenesis through metabolic activation of estrogens and/or ER-mediated pathways will certainly result in better preventive or therapeutic modalities for PCa.

Tamoxifen induces apoptosis in Fas+ tumor cells by upregulating the expression of Fas ligand

PURPOSE

Tamoxifen (TAM), a nonsteroidal anticancer agent, is used in the treatment of breast cancer. In the current study, we investigated whether TAM induces apoptosis in tumor cells by altering the expression of Fas and Fas ligand (FasL).

METHODS

Several tumor cell lines were used to test the ability of TAM to induce apoptosis, which was studied using the TUNEL assay. The effect of TAM on the expression of Fas and FasL was analyzed using a flow cytometer.

RESULTS

TAM was found to suppress the growth of an estrogen receptor-positive human mammary tumor cell line (T-47D) by inducing apoptosis. Interestingly, TAM also induced apoptosis in an estrogen receptor-negative murine T cell lymphoma cell line, EL-4. The ability of TAM to induce apoptosis in T-47D and EL-4 tumor cells correlated with the increased expression of FasL but not Fas on the tumor cells. Similar to TAM, a metalloproteinase (MP) inhibitor, which is known to increase the expression of membrane-bound FasL, was found to induce apoptosis in both T-47D and EL-4 tumor cells by increasing the expression of FasL but not Fas. Furthermore, both TAM and the MP inhibitor failed to induce apoptosis in L1210 tumor cell lines that failed to express FasL.

CONCLUSIONS

The current study demonstrates that TAM can induce apoptosis in Fas(+) tumor cells by upregulating FasL.

Mechanisms involved in the evolution of progestin resistance in human endometrial hyperplasia--precursor of endometrial cancer

BACKGROUND

Successful treatment of endometrial hyperplasia with progestins is commonly accompanied by the finding of an inactive or suppressed endometrium after therapy. However, approximately 30% of the endometrial hyperplasia cases do not respond to progestins and hyperplastic glands persist. The Fas/FasL system is known to play a role in tissue remodeling as a result of changes in menstrual hormone levels. The aims of this study are to examine Fas/FasL expression in endometrial hyperplasia of pre- and postprogestin treatment samples and to study the Fas/FasL regulation in vitro with Ishikawa cells after progestin stimulation.

DESIGN

Pre- and posttreatment paraffin-embedded endometrial hyperplasia tissue samples from 26 women were examined by immunohistochemistry for changes in Fas/FasL expression related to the administration of progestins. Among 26 patients, 18 were successfully treated with progestins and 8 failed treatment. Fas/ FasL positivity was defined by the presence of 10% or more immunoreactive epithelial cells in each specimen. In positive cases, a percentage or an immunoscore of immunoreactive cells was given by counting 500 cells. Cell viability was evaluated by the MTT assay. The in vitro effects of progesterone on Fas/FasL expression and apoptosis in Ishikawa cells were examined by using Western blot and TUNEL assays, respectively.

RESULTS

Fas immunoreactivity was present in 4/26 (15%) preprogestin cases with an average of 16% of the epithelial cells expressing Fas. FasL was expressed in 21/26 (80%) pretreatment cases with an average of 42% of the hyperplastic glandular cells being positive. In postprogestin cases, an increase of Fas expression (14/18, 77%) with an average of 47% stained cells was seen in responders (P < 0.001), while FasL was found in 16/18 (89%) responders with an average of 65% of cells positive (P = 0.587). In nonresponders, no significant changes in Fas/FasL expression were detected compared to pretreatment samples. With in vitro Ishikawa cells, a slight increase (10-20%) of Fas and FasL protein expression was detected after 24 h of progesterone treatment, but a more significant increase (220-343%) of both Fas and FasL expression was found after 48 h of withdrawing progesterone, which parallels apoptotic activity.

CONCLUSIONS

The Fas/FasL system may be involved in the development of endometrial hyperplasia. Part of the molecular mechanisms of progestin therapy for endometrial hyperplasia is through upregulation of Fas/FasL expression. Dysregulation of Fas/FasL expression in hyperplastic endometrium may be part of the molecular mechanisms for nonresponders to progestin treatment. Intermittent, rather than continuous, progestin treatment may be more effective clinically for the treatment of endometrial hyperplasia.

Interaction of the estrogen receptors with the Fas ligand promoter in human monocytes

The predominance of autoimmune diseases among women suggests that estrogen may modulate immune function. Monocytes and macrophages are important in initiating, maintaining, and resolving inflammatory responses through cell-signaling molecules, which control immune cell survival. One important mechanism of cell survival is mediated by the Fas/Fas ligand (FasL) system. In this study, the link between estrogen, monocytes/macrophages, and the Fas/FasL system was investigated. Estrogen treatment increased FasL expression in monocytes through the binding of the estrogen receptors (ER) to the estrogen recognizing elements and AP-1 motifs present at the FasL promoter. Furthermore, estrogen induced apoptosis in monocytes expressing ERbeta, but not in monocyte-differentiated macrophages expressing ERalpha. The expression of either ERalpha or ERbeta and their response to estrogen in monocytes was found to be dependent on the their stage of cell differentiation. Previously, we have shown that estrogen replacement therapy in postmenopausal women decreased the number of circulating monocytes. In this study, we have characterized the molecular mechanism by which estrogen regulates monocytes homeostasis. These findings indicate that estrogen may regulate immune cell survival through the Fas/FasL system. There is biological relevance to these findings in view of studies showing that accumulation of activated monocytes is involved in the pathogenesis of conditions such as vasculititis, arteriosclerosis, and rheumatoid arthritis.

Role of the Fas/Fas ligand system in female reproductive organs: survival and apoptosis

For centuries, the question of "whether there is life after death" has intrigued the mind of philosophers and the same question fascinates researchers in the field of apoptosis today. The death of a cell is by no means the end of the story. On the contrary, growing evidence suggests that the clearance of apoptotic bodies by macrophages is an important regulatory component in tissue renewal. Without death by apoptosis, the life of reproductive tissues and their function would not be possible. The survival signals that counteract cell death also prepare the cells for apoptosis, and dead cells are important stimuli for tissue survival. The Fas/Fas ligand system is an important mediator of apoptosis and is an excellent example of this apparently contradictory phenomenon.

Developing a laboratory animal model for perinatal endocrine disruption: the hamster chronicles

At the biomedical, regulatory, and public level, considerable concern surrounds the concept that inappropriate exposure to endocrine-disrupting chemicals, especially during the prenatal and/or neonatal period, may disrupt normal reproductive tract development and adult function. The intent of this review was to 1. Describe some unique advantages of the hamster for perinatal endocrine disruptor (ED) studies, 2. Summarize the morphological and molecular consequences of exposure to the established perinatal ED, diethylstilbestrol, in the female and male hamster, 3. Present some new, histomorphological insight into the process of neonatal diethylstilbestrol-induced disruption in the hamster uterus, and 4. Introduce recent efforts and future plans to evaluate the potency and mechanism of action of other putative EDs in the hamster experimental system. Taken together, the findings indicate that the hamster represents a unique and sensitive in vivo system to probe the phenomenon of endocrine disruption. The spectrum of candidate endpoints includes developmental toxicity, neoplasia, and more subtle endpoints of reproductive dysfunction.

Differential regulation and function of the Fas/Fas ligand system in human trophoblast cells

Trophoblast rejection, which is characterized by increased apoptosis, is mediated by T helper (Th)-1, or proinflammatory, cytokines, whereas Th-2, or anti-inflammatory, cytokines confer immune protection and facilitate implantation. We investigated the role of both types of cytokines on the expression and function of the Fas/Fas ligand (FasL) apoptotic pathway in trophoblast cells. First-trimester human trophoblast primary-culture cells as well as A3 and HTR/8 trophoblast cell lines were treated with proinflammatory cytokines such as interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNFalpha) and with the anti-inflammatory cytokines interleukin (IL)-6 and IL-10. Sensitivity to Fas-mediated apoptosis was measured using an activating anti-Fas monoclonal antibody. Cell viability was evaluated using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) and CellTiter 96 assay. Fas/FasL mRNA and protein expression levels were determined using reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. Trophoblast cells normally express FasL, but low levels of Fas, and they are resistant to Fas-mediated apoptosis. IFN-gamma and TNFalpha promote Fas expression and sensitivity, whereas IL-6 and IL-10 increase the resistance of trophoblast cells to Fas-mediated apoptosis. Furthermore, IL-10 treatment activates FLICE-like inhibitory protein (FLIP), a downstream inhibitor of Fas apoptotic signaling. Although trophoblast cells express Fas, susceptibility to Fas does not necessarily correlate with its expression. In this study, we demonstrate that Th-2 cytokines increase the resistance of trophoblast cells to Fas-mediated apoptosis either by inhibiting Fas expression or by inducing FLIP activation. This "trophoblast-cytokine-Fas/FasL triad" determines the ability of the Fas/FasL system to regulate trophoblast viability and, consequently, the success or failure of pregnancy.

Apoptosis and apoptosis-associated parameters in relation to tamoxifen exposure in postmenopausal endometrium

Tamoxifen increases endometrial cell proliferation and the incidence of endometrial cancer in postmenopausal women. The purpose of this study was to evaluate apoptosis and apoptosis-related factors in endometrium in relation to tamoxifen exposure. We analyzed benign postmenopausal endometrium from breast cancer patients receiving tamoxifen (n = 35) and from controls (n = 24), and endometrial cancer tissue from tamoxifen-treated breast cancer patients (n = 15) and endometrial cancer from women without tamoxifen exposure (n = 51). Apoptosis was examined morphologically, and the percentage of apoptotic epithelial cells was defined as the apoptotic index. In the benign samples, the presence of apoptotic cells was also evaluated immunohistochemically by the expression of caspase-3 and the monoclonal antibody M30. The expression of Fas, FasL, and Bcl-2 was analyzed in all tissue samples. No differences were observed in the mean apoptotic index in benign endometrium in tamoxifen users (0.17%) versus controls (0.08%), or in tamoxifen-exposed (2.46%) versus nonexposed endometrial cancer (2.28%). However, the ratio of the apoptotic index with the previously reported proliferation index was lower in benign endometrium from tamoxifen users than in controls (0.02 +/- 0.026 vs. 0.05 +/- 0.03, Mann-Whitney U <0.005). In benign endometrium FasL was more frequently expressed in tamoxifen-users than in controls (chi(2) <0.05). We conclude that the apoptosis/proliferation ratio in benign endometrium from tamoxifen users is lower than in controls, indicating that the tamoxifen-induced higher proliferation is not compensated for by increased apoptosis. An imbalance between cell proliferation and apoptosis, and possibly suppression of the antitumor immune response by FasL overexpression in tamoxifen-exposed endometrium might play a role in the development of endometrial cancer in tamoxifen users.

Tumour Fas ligand:Fas ratio greater than 1 is an independent marker of relative resistance to tamoxifen therapy in hormone receptor positive breast cancer

BACKGROUND

The objective of the present study was to examine the prognostic and predictive significance of the apoptosis-related marker Fas ligand (FasL):Fas ratio in breast cancer.

METHODS

Tumour biopsies from 215 primary invasive breast cancer patients were examined for the expression of FasL and Fas mRNA transcripts by quantitative real-time RT-PCR. Their prognostic and predictive impact on patient survival was determined in univariate and multivariate survival analyses.

RESULTS

Using a cutoff value of 1, a FasL:Fas ratio greater than 1 was found to have significant prognostic value for disease-free survival among the total population (median follow up 54 months). It was associated with a significantly decreased disease-free survival (P = 0.022) and with a tendency toward increased mortality (P = 0.14) in univariate analysis. Hormone receptor positive women exclusively treated with tamoxifen (n = 86) and with a FasL:Fas ratio greater than 1 had a significantly decreased disease-free survival (P = 0.008) and overall survival (P = 0.03) in univariate Kaplan-Meier analysis. Furthermore, tumour size and FasL:Fas ratio were of independent predictive significance in the multivariate model for disease-free and overall survival in that subgroup. Among postmenopausal patients (n = 148) both of those factors retained independent prognostic significance in the multivariate model for disease-free survival. In contrast, FasL:Fas ratio had no significant predictive value in patients exclusively treated with chemotherapy.

CONCLUSION

The data presented indicate that FasL:Fas ratio may be useful not only as a prognostic factor but also as a predictive factor for projecting response to the antioestrogen tamoxifen. The results strongly support a correlation between FasL:Fas ratio greater than 1 and lack of efficacy of tamoxifen in hormone receptor positive patients.

17alpha-methyl testosterone is a competitive inhibitor of aromatase activity in Jar choriocarcinoma cells and macrophage-like THP-1 cells in culture

17alpha-methyl testosterone is a synthetic androgen with affinity for the androgen receptor. 17alpha-methyl testosterone is used widely as a component of hormone replacement therapy. Previous reports have indicated that contrary to testosterone, 17alpha-methyl testosterone is not aromatized. However, 17alpha-methyl testosterone still could affect local estrogen formation by regulating aromatase expression or by inhibiting aromatase action. Both possibilities have important clinical implications. To evaluate the effect of 17alpha-methyl testosterone on the expression and activity of aromatase, we tested the choriocarcinoma Jar cell line, a cell line that express high levels of P450 aromatase, and the macrophage-like THP-1 cells, which express aromatase only after undergoing differentiation. We found that in both cell lines, 17alpha-methyl testosterone inhibits aromatase activity in a dose-related manner. The curve of inhibition parallels that of letrozole and gives complete inhibition at 10(-4) M 17alpha-methyl testosterone, determined by the tritium release assay. 17alpha-methyl testosterone does not have detectable effects on aromatase RNA and protein expression by Jar cells. Undifferentiated THP-1 cells had no aromatase activity and showed no effect of 17alpha-methyl testosterone, but differentiated THP-1 (macrophage-like) cells had a similar inhibition of aromatase activity by 17alpha-methyl testosterone to that seen in Jar cells. The Lineweaver-Burke plot shows 17alpha-methyl testosterone to be a competitive aromatase inhibitor. Our results show for the first time that 17alpha-methyl testosterone acts as an aromatase inhibitor. These findings are relevant for understanding the effects of 17alpha-methyl testosterone as a component of hormone replacement therapy. 17alpha-methyl testosterone may, as a functional androgen and orally active steroidal inhibitor of endogenous estrogen production, also offer special possibilities for the prevention/treatment of hormone-sensitive cancers.

Immune privilege or inflammation? Insights into the Fas ligand enigma

Fas ligand (FasL) has become an enigmatic molecule: some evidence indicates that it contributes to immune privilege in tissues and tumors, whereas other data demonstrates that FasL can elicit inflammation. New findings may begin to reconcile the paradoxical effects of FasL.

Roles of Fas and Fas ligand during mammary gland remodeling

Mammary involution is associated with degeneration of the alveolar structure and programmed cell death of mammary epithelial cells. In this study, we evaluated the expression of Fas and Fas ligand (FasL) in the mammary gland tissue and their possible role in the induction of apoptosis of mammary cells. FasL-positive cells were observed in normal mammary epithelium from pregnant and lactating mice, but not in nonpregnant/virgin mouse mammary tissue. Fas expression was observed in epithelial and stromal cells in nonpregnant mice but was absent during pregnancy. At day 1 after weaning, high levels of both Fas and FasL proteins and caspase 3 were observed and coincided with the appearance of apoptotic cells in ducts and glands. During the same period, no apoptotic cells were found in the Fas-deficient (MRL/lpr) and FasL-deficient (C3H/gld) mice. Increase in Fas and FasL protein was demonstrated in human (MCF10A) and mouse (HC-11) mammary epithelial cells after incubation in hormone-deprived media, before apoptosis was detected. These results suggest that the Fas-FasL interaction plays an important role in the normal remodeling of mammary tissue. Furthermore, this autocrine induction of apoptosis may prevent accumulation of cells with mutations and subsequent neoplastic development. Failure of the Fas/FasL signal could contribute to tumor development.