17beta-Estradiol responsiveness of MCF-7 laboratory strains is dependent on an autocrine signal activating the IGF type I receptor

Comparison of in vitro Toxicities of 8-Prenylnaringenin, Tartrazine and 17β-Estradiol, Representatives of Natural and Synthetic Estrogens, in Rat and Human Hepatoma Cell Lines

BACKGROUND

Phytoestrogens have been praised for their beneficial health effects, whereas synthetic xenoestrogens have been connected to ailments.

AIMS

To ascertain whether the toxicities of natural and synthetic estrogens differ, we examined the potent phytoestrogen 8-prenylnaringenin (8-PN), the common synthetic xenoestrogen tartrazine, and the physiological estrogen 17β-estradiol (E2).

METHODS

These three compounds were tested for cytotoxicity, cell proliferation and genotoxicity in human HepG2 and rat H4IIE hepatoma cells.

RESULTS

All three estrogens elicited cytotoxicity at high concentrations in both cell lines. They also inhibited cell proliferation, with E2 being the most effective. They all tended to increase micronuclei formation.

CONCLUSION

Natural estrogens were no less toxic than a synthetic one.

Generation of 3D Spheroids Using a Thiol-Acrylate Hydrogel Scaffold to Study Endocrine Response in ER+ Breast Cancer

Culturing cancer cells in a three-dimensional (3D) environment better recapitulates in vivo conditions by mimicking cell-to-cell interactions and mass transfer limitations of metabolites, oxygen, and drugs. Recent drug studies have suggested that a high rate of preclinical and clinical failures results from mass transfer limitations associated with drug entry into solid tumors that 2D model systems cannot predict. Droplet microfluidic devices offer a promising alternative to grow 3D spheroids from a small number of cells to reduce intratumor heterogeneity, which is lacking in other approaches. Spheroids were generated by encapsulating cells in novel thiol–acrylate (TA) hydrogel scaffold droplets followed by on-chip isolation of single droplets in a 990- or 450-member trapping array. The TA hydrogel rapidly (∼35 min) polymerized on-chip to provide an initial scaffold to support spheroid development followed by a time-dependent degradation. Two trapping arrays were fabricated with 150 or 300 μm diameter traps to investigate the effect of droplet size and cell seeding density on spheroid formation and growth. Both trapping arrays were capable of ∼99% droplet trapping efficiency with ∼90% and 55% cellular encapsulation in trapping arrays containing 300 and 150 μm traps, respectively. The oil phase was replaced with media ∼1 h after droplet trapping to initiate long-term spheroid culturing. The growth and viability of MCF-7 3D spheroids were confirmed for 7 days under continuous media flow using a customized gravity-driven system to eliminate the need for syringe pumps. It was found that a minimum of 10 or more encapsulated cells are needed to generate a growing spheroid while fewer than 10 parent cells produced stagnant 3D spheroids. As a proof of concept, a drug susceptibility study was performed treating the spheroids with fulvestrant followed by interrogating the spheroids for proliferation in the presence of estrogen. Following fulvestrant exposure, the spheroids showed significantly less proliferation in the presence of estrogen, confirming drug efficacy.

Coumarins and Coumarin-Related Compounds in Pharmacotherapy of Cancer

Cancer is one of the most common causes of disease-related deaths worldwide. Despite the discovery of many chemotherapeutic drugs that inhibit uncontrolled cell division processes for the treatment of various cancers, serious side effects of these drugs are a crucial disadvantage. In addition, multi-drug resistance is another important problem in anticancer treatment. Due to problems such as cytotoxicity and drug resistance, many investigations are being conducted to discover and develop effective anticancer drugs. In recent years, researchers have focused on the anticancer activity coumarins, due to their high biological activity and low toxicity. Coumarins are commonly used in the treatment of prostate cancer, renal cell carcinoma and leukemia, and they also have the ability to counteract the side effects caused by radiotherapy. Both natural and synthetic coumarin derivatives draw attention due to their photochemotherapy and therapeutic applications in cancer. In this review, a compilation of various research reports on coumarins with anticancer activity and investigation and a review of structure-activity relationship studies on coumarin core are presented. Determination of important structural features around the coumarin core may help researchers to design and develop new analogues with a strong anticancer effect and reduce the potential side effects of existing therapeutics.

Synthesis and Biological Evaluation of Novel Osthol Derivatives as Potent Cytotoxic Agents

BACKGROUND

Natural product, osthol has been found to have important biological and pharmacological roles particularly having inhibitory effect on multiple types of cancer.

OBJECTIVE

The unmet needs in cancer therapeutics make its derivatization an important and exciting field of research. Keeping this in view, a whole new series of diverse analogues of osthol (1) were synthesized.

METHOD

All the newly synthesized compounds were made through modification in the lactone ring as well as in the side chain of the osthol molecule and were subjected to anti-proliferative screening through 3-(4,5-Dimethylthiazol-yl)-diphenyl tetrazoliumbromide (MTT) against four different human cancers of diverse origins viz. Colon (Colo-205), lung (A549), Leukemia (THP- 1) and breast (MCF-7) including SV40 transformed normal breast epithelial cell (fR-2).

RESULTS

Interestingly, among the tested molecules, most of the analogs displayed better antiproliferative activity than the parent Osthol 1. However, among all the tested analogs, compound 28 exhibited the best results against leukemia (THP1) cell line with IC50 of 5µM.Compound 28 induced potent apoptotic effects and G1 phase arrest in leukemia cancer cells (THP1). The population of apoptotic cells increased from 13.8% in negative control to 26.9% at 8μM concentration of 28. Compound 28 also induced a remarkable decrease in mitochondrial membrane potential (ΛΨm) leading to apoptosis of the cancer cells.

CONCLUSION

A novel series of molecules derived from natural product osthol were synthesized, wherein compound 28 was found to be most effective against leukemia and with 10 fold less toxicity against normal cells. The compound induced cancer inhibition mainly through apoptosis and thus has a potential in cancer therapeutics.

Essential oil from Cymbopogon flexuosus as the potential inhibitor for HSP90

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The essential oil of Cymbopogon flexuosus or lemongrass oil (LO) is reported.

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Essential oil of C. flexuosus significantly suppresses the HSP90 gene expression.

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Increased expression of HSP90 gene by citral and geraniol in HEK-293 cells.

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Inhibition of HSP90-ATPase acitivity by the essential oil of C. flexuosus.

The essential oil of Cymbopogon flexuosus or lemongrass oil (LO) is reported to have antibacterial, antifungal and anticancerous effects. HSP90 is one of the major chaperones responsible for the proper folding of cancer proteins. In this paper we show that the essential oil of C. flexuosus significantly suppresses the HSP90 gene expression. The cytotoxicity of the compounds was tested by MTT assay and the gene expression studies were carried out using HEK-293 and MCF-7 cells. Also we tested the efficacy of the major component of this essential oil viz. citral and geraniol in inhibiting the HSP90 expression. The oil was found to be more cytotoxic to MCF-7 cells with different IC₅₀ values for the oil (69.33 μg/mL), citral (140.7 μg/mL) and geraniol (117 μg/mL). The fold change of expression was calculated by RT-qPCR using ΔΔCt (2^{^−ΔΔCt}) method and it was 0.1 and 0.03 in MCF-7 cells at 80 μg/mL and 160 μg/mL of LO. Western blot results showed suppression of HSP90 protein expression and HSP90 – ATPase activity inhibition was also observed using LO. This study shows the anticancer mechanism exhibited by the essential oil of C. flexuosus is by the inhibition of the important chaperone protein HSP90.

Estrogen receptor agonists/antagonists in breast cancer therapy: A critical review

Estrogens display intriguing tissue selective action that is of great biomedical importance in the development of optimal therapeutics for the prevention and treatment of breast cancer. There are also strong evidences to show that both endogenous and exogenous estrogens are involved in the pathogenesis of breast cancer. Tamoxifen has been the only drug of choice for more than 30years to treat patients with estrogen related (ER) positive breast tumors. There is a need therefore, for identifying newer, potential and novel candidates for breast cancer. Keeping this in view, the present review focuses on selective estrogen receptor modulators and estrogen antagonists such as sulfatase and aromatase inhibitors involved in breast cancer therapy. A succinct and critical overview of the structure of estrogen receptors, their signaling and involvement in breast carcinogenesis are herein described.

Steroidogenic effect of Erxian decoction for relieving menopause via the p-Akt/PKB pathway in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Erxian decoction (EXD), an empirical Chinese medicine formula, is effectively used in the clinical treatment of menopause-related symptoms in China. Previous data from our group show that EXD has steroidogenic effect on natural menopausal Sprague-Dawley-rats (SD-rats) as an animal model of menopause. However, the mechanistic studies on steroidogenic effects of EXD are still inadequate. Hence, the mechanisms of steroidogenic effects of EXD were studied in vitro and in vivo in this study.

MATERIALS AND METHODS

Menopause causes a decline of endocrine function and a series of symptoms. In this study, 16-20-month-old female SD rats with a low serum estradiol level were employed. Their endocrine functions after treatment with EXD (4.1g/kg) were assessed by determination of their serum estradiol level. Proteins involved in the steroidogenic pathway including StAR, 17βHSD, 3βHSD, aromatase, and activation of phosphorylated Protein Kinase B (p-Akt/PKB), as well as estradiol receptor proteins (ERα & ERβ) after EXD treatment were analyzed. Kinase inhibition assay was conducted to confirm the mechanism of steroidogenic effects of EXD in vitro. MCF-7 and BT-483 cells were used to investigate whether EXD stimulated breast cancer cell proliferation.

RESULTS

Results revealed a significantly ameliorated serum estradiol level, and a significantly increased expression of ovarian aromatase and PKB in the EXD-treated rats. EXD attenuated 17β-estradiol stimulated proliferation of breast cancer cells.

CONCLUSIONS

The results obtained from immunoblotting and measurements of serum estradiol level of the present investigation revealed that EXD may relieve the menopausal syndrome through an upregulation of ovarian aromatase and p-PKB expression without stimulating the growth of breast cancer cells.

Effects of rapamycin on cell apoptosis in MCF-7 human breast cancer cells

BACKGROUND

Rapamycin is an effective anti-angiogenic drug. However, the mode of its action remains unclear. Therefore, in this study, we aimed to elucidate the antitumor mechanism of rapamycin, hypothetically via apoptotic promotion, using MCF-7 breast cancer cells.

MATERIALS AND METHODS

MCF-7 cells were plated at a density of 15105 cells/well in 6-well plates. After 24h, cells were treated with a series of concentrations of rapamycin while only adding DMEM medium with PEG for the control regiment and grown at 37oC, 5% CO2 and 95% air for 72h. Trypan blue was used to determine the cell viability and proliferation. Untreated and rapamycin-treated MCF-7 cells were also examined for morphological changes with an inverted-phase contrast microscope. Alteration in cell morphology was ascertained, along with a stage in the cell cycle and proliferation. In addition, cytotoxicity testing was performed using normal mouse breast mammary pads.

RESULTS

Our results clearly showed that rapamycin exhibited inhibitory activity on MCF-7 cell lines. The IC50 value of rapamycin on the MCF-7 cells was determined as 0.4μg/ml (p<0.05). Direct observation by inverted microscopy demonstrated that the MCF-7 cells treated with rapamycin showed characteristic features of apoptosis including cell shrinkage, vascularization and autophagy. Cells underwent early apoptosis up to 24% after 72h. Analysis of the cell cycle showed an increase in the G0G1 phase cell population and a corresponding decrease in the S and G2M phase populations, from 81.5% to 91.3% and 17.3% to 7.9%, respectively.

CONCLUSIONS

This study demonstrated that rapamycin may potentially act as an anti-cancer agent via the inhibition of growth with some morphological changes of the MCF-7 cancer cells, arrest cell cycle progression at G0/G1 phase and induction of apoptosis in late stage of apoptosis. Further studies are needed to further characterize the mode of action of rapamycin as an anti-cancer agent.

Estrogenic endocrine disruptors: Molecular mechanisms of action

A comprehensive summary of more than 450 estrogenic chemicals including estrogenic endocrine disruptors is provided here to understand the complex and profound impact of estrogen action. First, estrogenic chemicals are categorized by structure as well as their applications, usage and effects. Second, estrogenic signaling is examined by the molecular mechanism based on the receptors, signaling pathways, crosstalk/bypassing and autocrine/paracrine/homeostatic networks involved in the signaling. Third, evaluation of estrogen action is discussed by focusing on the technologies and protocols of the assays for assessing estrogenicity. Understanding the molecular mechanisms of estrogen action is important to assess the action of endocrine disruptors and will be used for risk management based on pathway-based toxicity testing.

17β-estradiol induces stearoyl-CoA desaturase-1 expression in estrogen receptor-positive breast cancer cells

Background

To sustain cell growth, cancer cells exhibit an altered metabolism characterized by increased lipogenesis. Stearoyl-CoA desaturase-1 (SCD-1) catalyzes the production of monounsaturated fatty acids that are essential for membrane biogenesis, and is required for cell proliferation in many cancer cell types. Although estrogen is required for the proliferation of many estrogen-sensitive breast carcinoma cells, it is also a repressor of SCD-1 expression in liver and adipose. The current study addresses this apparent paradox by investigating the impact of estrogen on SCD-1 expression in estrogen receptor-α-positive breast carcinoma cell lines.

Methods

MCF-7 and T47D mammary carcinomas cells and immortalized MCF-10A mammary epithelial cells were hormone-starved then treated or not with 17β-estradiol. SCD-1 activity was assessed by measuring cellular monounsaturated/saturated fatty acid (MUFA/SFA) ratios, and SCD-1 expression was measured by qPCR, immunoblot, and immunofluorescence analyses. The role of SCD-1 in cell proliferation was measured following treatment with the SCD-1 inhibitor A959372 and following SCD-1 silencing using siRNA. The involvement of IGF-1R on SCD-1 expression was measured using the IGF-1R antagonist AG1024. The expression of SREBP-1c, a transcription factor that regulates SCD-1, was measured by qPCR, and by immunoblot analyses.

Results

17β-estradiol significantly induced cell proliferation and SCD-1 activity in MCF-7 and T47D cells but not MCF-10A cells. Accordingly, 17β-estradiol significantly increased SCD-1 mRNA and protein expression in MCF-7 and T47D cells compared to untreated cells. Treatment of MCF-7 cells with 4-OH tamoxifen or siRNA silencing of estrogen receptor-α largely prevented 17β-estradiol-induced SCD-1 expression. 17β-estradiol increased SREBP-1c expression and induced the mature active 60 kDa form of SREBP-1. The selective SCD-1 inhibitor or siRNA silencing of SCD-1 blocked the 17β-estradiol-induced cell proliferation and increase in cellular MUFA/SFA ratios. IGF-1 also induced SCD-1 expression, but to a lesser extent than 17β-estradiol. The IGF-1R antagonist partially blocked 17β-estradiol-induced cell proliferation and SCD-1 expression, suggesting the impact of 17β-estradiol on SCD-1 expression is partially mediated though IGF-1R signaling.

Conclusions

This study illustrates for the first time that, in contrast to hepatic and adipose tissue, estrogen induces SCD-1 expression and activity in breast carcinoma cells. These results support SCD-1 as a therapeutic target in estrogen-sensitive breast cancer.

The Tumor Macroenvironment: Cancer-Promoting Networks Beyond Tumor Beds

During tumor progression, alterations within the systemic tumor environment, or macroenvironment, result in the promotion of tumor growth, tumor invasion to distal organs, and eventual metastatic disease. Distally produced hormones, commensal microbiota residing within mucosal surfaces, myeloid cells and even the bone marrow impact the systemic immune system, tumor growth, and metastatic spread. Understanding the reciprocal interactions between the cells and soluble factors within the macroenvironment and the primary tumor will enable the design of specific therapies that have the potential to prevent dissemination and metastatic spread. This chapter will summarize recent findings detailing how the primary tumor and systemic tumor macroenvironment coordinate malignant progression.

Click chemistry inspired synthesis and bioevaluation of novel triazolyl derivatives of osthol as potent cytotoxic agents

A new series of diverse triazoles linked through the hydroxyl group of lactone ring opened osthol (1) were synthesized using click chemistry approach. All the derivatives were subjected to 3-(4,5-Dimethylthiazol-yl)-diphenyl tetrazoliumbromide (MTT) cytotoxicity screening against a panel of seven different human cancer cell lines viz. colon (colo-205), colon (HCT-116), breast (T47D), lung (NCI-H322), lung (A549), prostate (PC-3) and Skin (A-431) to check their cytotoxic potential. Interestingly, among the tested molecules, most of the analogs displayed better cytotoxic activity than the parent osthol (1). Of the synthesized triazoles, compounds 8 showed the best activity with IC50 of 1.3, 4.9, 3.6, 41.0, 35.2, 26.4 and 7.2 μM against colon (Colo-205 and HCT-116), breast (T47D), lung (NCI-H322 and A549), prostate (PC-3) and Skin (A-431) cancer lines respectively. Compound 8 induced potent apoptotic effects in Colo-205 cells. The population of apoptotic cells increased from 11.4% in case of negative control to 24.1% at 25 μM of 8. Compound 8 also induced a remarkable decrease in mitochondrial membrane potential (ΛΨm) leading to apoptosis of cancer cells used. The present study resulted in identification of broad spectrum cytotoxic activity of analogs bearing electron withdrawing substituents, besides the enhanced selective activity of analogs with electron donating moieties.

Systematic nucleo-cytoplasmic trafficking of proteins following exposure of MCF7 breast cancer cells to estradiol

We have used a proteomics subcellular spatial razor approach to look at changes in total protein abundance and in protein distribution between the nucleus and cytoplasm following exposure of MCF7 breast cancer cells to estradiol. The dominant response of MCF7 cells to estrogen stimulation involves dynamic changes in protein subcellular spatial distribution rather than changes in total protein abundance. Of the 3604 quantitatively monitored proteins, only about 2% show substantial changes in total abundance (>2-fold), whereas about 20% of the proteins show substantial changes in local abundance and/or redistribution of their subcellular location, with up to 16-fold changes in their local concentration in the nucleus or the cytoplasm. We propose that dynamic redistribution of the subcellular location of multiple proteins in response to stimuli is a fundamental characteristic of cells and suggest that perturbation of cellular spatial control may be an important feature of cancer.

Plasma amino acid profiles are associated with biomarkers of breast cancer risk in premenopausal Japanese women

OBJECTIVE

Recently, profiles of plasma amino acids have been utilized to detect diseases including breast cancer. However, there is a possibility that the amino acid status may be associated with the risk of breast cancer. We investigated the relationship of plasma levels of amino acids with levels of sex hormones and insulin-like growth factor (IGF)-1, which are relevant to the etiology of premenopausal breast cancer, in normal premenopausal women.

METHODS

Participants were 350 Japanese women who had regular menstrual cycles less than 40-day long. Fasting plasma samples were assayed for estradiol, testosterone, dehydroepiandrosterone sulfate, sex-hormone-binding globulin (SHBG), and IGF-1. A total of 20 amino acids in plasma were quantified by liquid chromatography-mass spectrometry. Information on lifestyle and reproductive factors was obtained using a self-administered questionnaire.

RESULTS

The plasma arginine level was significantly inversely correlated with plasma levels of total and free estradiol and IGF-1 after adjusting for age, body mass index, and phase of the menstrual cycle. Plasma leucine and tyrosine levels were significantly positively correlated with the free testosterone level. The ratio of plasma asparagine to the total amino acids was significantly positively correlated with SHBG level.

CONCLUSIONS

Plasma levels of some specific amino acids, such as arginine, leucine, tyrosine, and asparagine, were associated with the levels of sex hormones, SHBG, or IGF-1 in premenopausal women. However, the present cross-sectional study cannot provide a cause-effect relation. The implication of amino acids in the etiology of breast cancer needs to be addressed in future studies.

Identification and quantification of concentration-dependent biomarkers in MCF-7/BOS cells exposed to 17β-estradiol by 2-D DIGE and label-free proteomics

This paper reports the identification of biomarkers resulting from the exposure of MCF-7/BOS cells to 17β-estradiol (E(2)). The biomarkers were identified using 2 independent and complementary techniques, 2-D DIGE/MALDI-TOF peptide mass fingerprint, and 2-D UPLC-ESI MS/MS. They were identified from the cytosolic fractions of cells treated for 24h with mitogenic concentrations of 1, 30 and 500 pM of 17β-estradiol. Five biomarkers were up-regulated proteins, namely HSP 74, EF2, FKBP4, EF1 and GDIB and one was a down-regulated protein, namely K2C8. Three of these proteins, EF2, FKBP4 and K2C8 are implicated in a network centered on the estrogen receptors ESR1 and ESR2 as well as on AKT1. After the discovery phase, three biomarkers were selected to test the presence of estrogens using selected reaction monitoring (SRM). They were monitored using SRM after incubation of MCF-7/BOS in the presence of E(2) for confirmation or selected xenoestrogens. Daidzein, coumestrol and enterolactone induced an up-regulation of EF2 and FKPB4 proteins, while tamoxifen and resveratrol induced a down-regulation. The exposure of all phytoestrogens induced the down-regulation of K2C8. These markers form a preliminary molecular signature that can be used when testing the estrogenic activity of xenobiotics, either pure or in mixtures.

Detailed molecular fingerprinting of four new anaplastic thyroid carcinoma cell lines and their use for verification of RhoB as a molecular therapeutic target

CONTEXT

Anaplastic thyroid carcinoma (ATC) is a highly aggressive carcinoma in need of therapeutic options. One critical component of drug discovery is the availability of well-characterized cell lines for identification of molecular mechanisms related to tumor biology and drug responsiveness. Up to 42% of human thyroid cancer cell lines are redundant or not of correct tissue origin, and a comprehensive analysis is currently nonexistent. Mechanistically, RhoB has been identified as a novel molecular target for ATC therapy.

OBJECTIVE

The aim was to develop four ATC cell lines detailing genetic, molecular, and phenotypic characteristics and to test five classes of drugs on the cell lines to determine whether they inhibited cell proliferation in a RhoB-dependent fashion.

DESIGN

Four cell lines were derived from ATC tumors. Short tandem DNA repeat and mutational status of the originating tumors and cell lines were performed along with molecular and phenotypic characterizations. Compounds were tested for growth inhibition and ability to up-regulate RhoB.

RESULTS

Cell line authenticity was confirmed by DNA short tandem repeat analysis. Each proved unique regarding expression of thyroid markers, oncogene status, amplified and deleted genes, and proliferative growth rates. FTI-277, GGTI-286, lovastatin, romidepsin, and UCN-01 up-regulated RhoB and inhibited cell proliferation in a dose-responsive fashion with only romidepsin and FTI-277 being RhoB dependent.

CONCLUSIONS

Molecular descriptions of thyroid lines were matched to the originating tumors, setting a new standard for cell line characterization. Furthermore, suppressed RhoB is implicated as a molecular target for therapy against ATC because five classes of drugs up-regulate RhoB and inhibit growth dose-responsively.

In-vitro antiproliferative activity of benzopyranone derivatives in comparison with standard chemotherapeutic drugs

The cytotoxic activities of five new benzopyranone derivatives containing basic amino side chain are described. Their cytotoxicities against ER(+) MCF-7 and ER(-) MDA-MB-231 human breast cancer cell lines, and Ishikawa human endometrial cell line were determined after 72 h drug exposure employing CellTiter-Glo assay at concentrations ranging from 0.01-1.0 × 10(5) nM. The antiproliferative activities of these compounds were compared to tamoxifen (TAM), 4-hydroxytamoxifen (4-OHT, active metabolite of tamoxifen), and raloxifene (RAL). In-vitro results indicated that compounds 9, 10, 12, and 13 were more potent than TAM against the human breast cancer cell lines with IC(50)  < 20 µM. The in-silico structure-activity relationships of these compounds and their binding mode within the estrogen receptor (ER) binding site using AutoDock vina are discussed.

Synthesis and antiproliferative activity of coumarin-estrogen conjugates against breast cancer cell lines

The syntheses and cytotoxic activity of coumarin-estrogen conjugates are described. In vitro results indicated that conjugates 10, 11 and 13 show growth inhibitory activities at 5-dose concentration (100, 10, 1, 0.1, 0.01 muM) against the following NCI-7- human breast cancer cell lines: BT-549, HS 578T, MCF 7, MDA-MB-231/ATCC, MDA-MB-435, NCI/ADR-RES, and thus serve as new leads for further development of antibreast cancer agent.

A review of coumarin derivatives in pharmacotherapy of breast cancer

The coumarin (benzopyran-2-one, or chromen-2-one) ring system, present in natural products (such as the anticoagulant warfarin) that display interesting pharmacological properties, has intrigued chemists and medicinal chemists for decades to explore the natural coumarins or synthetic analogs for their applicability as drugs. Many molecules based on the coumarin ring system have been synthesized utilizing innovative synthetic techniques. The diversity oriented synthetic routes have led to interesting derivatives including the furanocoumarins, pyranocoumarins, and coumarin sulfamates (COUMATES), which have been found to be useful in photochemotherapy, antitumor and anti-HIV therapy, and as stimulants for central nervous system, antibacterials, anti-inflammatory, anti-coagulants, and dyes. Of particular interest in breast cancer chemotherapy, some coumarins and their active metabolite 7-hydroxycoumarin analogs have shown sulfatase and aromatase inhibitory activities. Coumarin based selective estrogen receptor modulators (SERMs) and coumarin-estrogen conjugates have also been described as potential antibreast cancer agents. Since breast cancer is the second leading cause of death in American women behind lung cancer, there is a strong impetus to identify potential new drug treatments for breast cancer. Therefore, the objective of this review is to focus on important coumarin analogs with antibreast cancer activities, highlight their mechanisms of action and structure-activity relationships on selected receptors in breast tissues, and the different methods that have been applied in the construction of these pharmacologically important coumarin analogs.

Activity of xenoestrogens at nanomolar concentrations in the E-Screen assay

BACKGROUND

Certain effects induced by endocrine-disrupting chemicals (EDCs) may occur at dose levels lower than those normally tested in toxicology, but few systematic dose-response studies have been carried out in the low-dose range.

OBJECTIVES

The high statistical power afforded by a high-throughput in vitro assay such as the E-Screen assay was exploited with the aim of producing low-dose estimates for 24 estrogenic chemicals, including endogenous hormones and xenoestrogens.

RESULTS

Unusual dose-response curves with inverted U-shapes were not observed in the low-dose range. Instead, many chemicals exhibited curves with very small gradients at low doses, and this complicated the reliable estimation of low effects. Systematic comparisons between the outcomes of hypothesis-testing procedures (lowest observed effect concentrations--LOECs, no observed effect concentrations--NOECs) and regression modeling approaches (EC(01)--effective concentration causing a 1% effect, EC(05)--effective concentration causing a 5% effect) produced estimates that agreed reasonably well. In many cases, NOECs were shown to be associated with proliferative responses of 1-2%. This is in contrast with the widespread perception of NOECs as values that signal complete absence of effects. For many of the tested xenoestrogens, the NOECs, EC(01), and EC(05) were in the nanomolar range, and comparisons with measured serum and adipose tissue levels in Europe revealed considerable overlaps in some cases.

CONCLUSIONS

Our studies illustrate the difficulties that may be encountered during the estimation of low doses in vivo. High statistical power is required when the underlying dose-response curves are shallow. Through the use of large sample sizes and numerous repeats, the experimental power of the E-Screen assay was sufficiently high to measure effect magnitudes of around 1-2% with reliability. However, such resources are usually not available for in vivo testing, with the consequence that the statistical detection limits are considerably higher. If this coincides with shallow dose-response curves in the low-effect range (which is normally not measurable in vivo), the limited resolving power of in vivo assays may seriously constrain low-dose testing.

Cannabinoids and cancer: pros and cons of an antitumour strategy

In the last two decades, research has dramatically increased the knowledge of cannabinoids biology and pharmacology. In mammals, compounds with properties similar to active components of Cannabis sativa, the so called 'endocannabinoids', have been shown to modulate key cell-signalling pathways involved in cancer cell growth, invasion and metastasis. To date, cannabinoids have been licensed for clinical use as palliative treatment of chemotherapy, but increased evidences showed direct antiproliferative actions of cannabinoid agonists on several tumour cells in vitro and in animal models. In this article, we will review the principal molecular pathways modulated by cannabinoids on cancer and summarize pros and cons evidence on the possible future use of endocannabinoid-based drugs in cancer therapy.

Endogenous aromatization of testosterone results in growth stimulation of the human MCF-7 breast cancer cell line

Estrogens produced within breast tumors may play a pivotal role in growth stimulation of the breast cancer cells. However, it is elusive whether the epithelial breast cancer cells themselves synthesize estrogens, or whether the surrounding tumor stromal cells synthesize and supply the cancer cells with estrogen. The aromatase enzyme catalyzes the estrogen production, aromatizing circulating androgens into estrogens. The aim of this study was to investigate aromatase expression and function in a model system of human breast cancer, using the estrogen responsive human MCF-7 breast cancer cell line. Cells were cultured in a low estrogen milieu and treated with estrogens, aromatizable androgens or non-aromatizable androgens. Cell proliferation, expression of estrogen-regulated proteins and aromatase activity were investigated. The MCF-7 cell line was observed to express sufficient aromatase enzyme activity in order to aromatize the androgen testosterone, resulting in a significant cell growth stimulation. The testosterone-mediated growth effect was completely inhibited by the aromatase inhibitors letrozole and 4-hydroxy-androstenedione. Expression studies of estrogen-regulated proteins confirmed that testosterone was aromatized to estrogen in the MCF-7 cells. Thus, the results indicate that epithelial breast cancer cells possess the ability to aromatize circulating androgens to estrogens.

Growth factor regulation of cell cycle progression in mammary epithelial cells

Growth factors are among the critical positive and negative regulators of cell proliferation for normal mammary/breast epithelial cells and for breast cancer cells. The mechanisms by which specific growth factors regulate the cell cycle in mammary/breast epithelial cells is beginning to be understood for several growth factor families, including the epidermal growth factor, insulin-like growth factor, and transforming growth factor-beta families. A critical issue for understanding how growth factors regulate the cell cycle in vivo is how individual factors interact with other growth factors or hormones to enhance or inhibit specific molecular targets in the cell cycle machinery. This review addresses what is currently known about how growth factors regulate the cell cycle in mammary/breast epithelial cells both individually and in coordination with other growth regulators.