Tamoxifen For Breast Cancer Therapy Research Articles

Preparation and Characterization of PLGA-PEG-PLGA Nanoparticles Containing Salidroside and Tamoxifen for Breast Cancer Therapy.

Nanoparticles (NPs) containing the hydrophilic drug salidroside (Sal) and the hydrophobic drug tamoxifen (Tam) were prepared using a triblock copolymer poly(lactic-co-glycolic acid) (PLGA)-poly(ethylene glycol) (PEG)-PLGA to achieve synergism in the treatment of breast cancer. The double emulsion (w/o/w) method was used to prepare Sal-Tam NPs with an average particle size of 275.3 ± 44.0nm, a polydispersity index of 0.302 ± 0.102, and a zeta potential of - 6.98 ± 2.99. The entrapment efficiency of the hydrophilic and hydrophobic components was 32.63% ± 0.73% and 49.18% ± 3.04%, respectively. On differential scanning calorimetry, the NPs showed the amorphous nature of both Sal and Tam. The sustained release of Sal and Tam from the NPs was significantly prolonged under physiological conditions (pH7.4). The CCK-8 assay using the 4T1 cell line revealed a 1.7-fold decrease in the IC50 value for Sal-Tam NPs when compared with free Tam. The in vivo anti-tumor effect was assessed in BALB/c mice, and the results demonstrated that these NPs decreased the tumor volume compared with saline and showed high anti-tumor activity. A pharmacokinetic study showed significant enhancement of the bioavailability of Tam in Sal-Tam NPs compared with free Tam in suspension. The intracellular and mitochondrial anti-oxidative effect of Sal was thought to be attributed to the promising anti-tumor effect of drug co-delivery. This study confirmed that the use of Sal-Tam NPs may be a promising approach in breast cancer therapy.

17β-estradiol at low concentrations attenuates the efficacy of tamoxifen in breast cancer therapy

Tamoxifen has been applied widely in the treatment of estrogen receptor (ER)-positive breast cancer. The impact of low concentrations of 17β-estradiol (E2) (a pervasive environmental pollutant) on its effectiveness was studied in vitro using an MCF-7 cell line. Cell proliferation, migration, invasion, and apoptosis were studied along with cell cycle progression, reactive oxygen species generation and mitochondrial membrane potentials repression. The signaling pathways involved were identified. Typical concentrations of E2 in the environment (10−10 to 10−8 M) were observed to promote cell growth and protect MCF-7 cells from tamoxifen's cytotoxicity. Cell migration, invasion, cell cycle progression and apoptosis all involved in reducing tamoxifen's cytotoxicity. E2 at environmental concentrations induced PI3K/Akt and MAPK/ERK signal transduction through the estrogen receptor pathways to affect cell proliferation. Taken together, the results explain how E2 in the environment may attenuate the efficacy of tamoxifen in ER-positive breast cancer therapy. They provide considerable support for E2's adverse effects on human health and cancer management.

491: Interaction of Hedgehog-Gli and estrogen receptor signaling pathways in breast cancer cells

Introduction Hedgehog-Gli (Hh-Gli) signaling pathway is one of the new molecular targets found upregulated in breast tumors. Estrogen receptor alpha (ERα) signaling has a key role in the development of hormone-dependent breast cancer. The aim of this study is to determine the possible combined effects of Hh-Gli pathway inhibitor cyclopamine with ER inhibitor tamoxifen in breast cancer therapy, and to establish a potential interactions between Hh-Gli and ER signaling in breast cancer. Materials and Methods ER-positive MCF-7 and ER-negative SkBr-3 breast cancer cell lines were used. Drug treatments and Competition experiments were with: cyclopamine 0.5-7.5 μM (Toronto Research Chemicals) and tamoxifen 1-10 μM (Toronto Research Chemicals). MTT and cell migration assays were used. Gene expression studies with : cyclopamine (2.5 μM), Shh protein (3 ng/ml), tamoxifen (1 μM for MCF-7 or 5 µM for SkBr-3), β-estradiol (5 nM, Sigma) or cyclopamine + tamoxifen and Transfection with GLI1 and PTCH1 silencing (Life Technologies) in MCF cells were performed, and QRT-PCR with primers for ERα, c-MYC, RPLP0, PTCH1, SMO, GLI1, SHH, andSUFU.Immunofluorescent staining, Immunoprecipitation and Western blot were performed with primary antibodies: anti-Hh (Santa Cruz, sc-9024), anti-ERα (Santa Cruz, sc-8002), anti-Ptch1 (Santa Cruz, sc-6147), anti-Gli1 (Santa Cruz, sc-20687) and Actin (Santa Cruz, sc-1616). Confocal images were examined using the Manders coefficient plugin of the ImageJ software (v 1.45e). Dynabeads Protein G (Life Technologies) were coated with anti-ERα antibody and cell lysates were immunoprecipitated as per manufacturer’s instructions. Results and Discussion ER-positive cells show decreased viability after treatment with cyclopamine, a Hh-Gli pathway inhibitor, as well as after tamoxifen (an ERα inhibitor) treatment. Simultaneous treatment with cyclopamine and tamoxifen on the other hand, causes short-term survival of cells, and only longer treatment decreases cell proliferation. The survival effect is strongest 48 hours after simultaneous treatment with both inhibitors, and we found upregulated Hh-Gli signaling under these conditions. In addition to promoting survival, the combination of these two drugs promotes cell migration and longer treatment decreases Hh-Gli signaling as well as ERα levels. We also show a direct interaction between Shh and ERα. Shh protein is able to bind and activate ERα independently of the canonical Hh-Gli signaling pathway. Conclusion The mechanism which is responsible for the increased viability of ER-positive cell line after combined treatment with cyclopamine and tamoxifen is not clear. Although Hh-Gli signaling seems to be a good potential target for breast cancer therapy, combined treatment of cyclopamine and tamoxifen may induce an opposite effect, providing cells with short-term survival.

Mitochondria: the gateway for tamoxifen-induced liver injury.

Tamoxifen (TAM) is routinely used in the treatment of breast carcinoma. TAM-induced liver injury remains a major concern, as TAM causes hepatic steatosis in a significant number of patients, which can progress toward steatohepatitis. Liver toxicity is generally believed to involve mitochondrial dysfunction and TAM exerts multiple deleterious effects on mitochondria, which may account for the hepatotoxicity observed in patients treated with TAM. Endoxifen (EDX), a key active metabolite of TAM that is being investigated as an alternative to TAM in breast cancer therapy, slightly affects mitochondria in comparison with TAM and this demonstration well correlates with the absence of alterations in the clinical parameters of individuals taking EDX. The steady-state plasma concentrations of TAM and its active metabolites EDX and 4-hydroxytamoxifen (OHTAM) in patients taking TAM are highly variable, reflecting genetic variants of CYP2D6 involved in TAM metabolism. Besides de genetic polymorphisms, the intake of drugs that influence the enzymatic activity of CYP2D6 compromises the therapeutic efficiency of TAM. The knowledge of the impact of the variability of TAM metabolism in the breast cancer treatment explains the discrepant outcomes observed in patients taking TAM, as well as the individual variability of idiosyncratic liver injury and other sides effects observed. Therefore, and contrarily to the clinical use of EDX, the need of therapeutic drug monitoring and a regular assessment of liver function biomarkers should be considered in patients under therapies with TAM. In this review we focus on the mitochondrial effects of TAM and its metabolites and on the role played by mitochondria in the initiating events leading to TAM-induced hepatotoxicity, as well as the clinical implications.

A synthetic PPARγ ligand sensitizes breast cancer cells to tamoxifen-induced apoptosis.

Abstract Abstract #1149 Blockade of estrogen receptor (ERa) by tamoxifen has been considered as a promising therapeutic approach to breast cancer. However, since not all the tumor cells are sensitive to tamoxifen, there is a need for the development of strategies to overcome the tamoxifen-resistance. Recently it has been known that ERa binds to peroxisome proliferator-activated receptor (PPAR) response element and negatively interferes with PPARg signaling in breast cancer cells, whose activation inhibits the growth of various cancer cells. Here we firstly wished to determine whether ERa inhibits PPARg-mediated cell death of human breast cancer cells. Troglitazone, a synthetic PPARg ligand, caused cell death and G1 arrest in both ERa-positive MCF-7 and ERa-negative MDA-MB-231 in a dose-dependent manner, but their degree shows differences between two cells. Troglitazone induced less cell death and G1 cell arrest in ERa-positive MCF-7 than ER-negative MDA-MB-231. The differences were abolished by PPARg knockdown using PPARg specific siRNA, indicating that ER inhibits PPARg-dependent anti-tumor action of PPARg agonist on breast cancer cells. Moreover, troglitazone sensitized breast cancer cells to tamoxifen-induced apoptosis, suggesting that the dose of tamoxifen for breast cancer therapy could be lowered by combination with troglitazone. Our results suggest that ERa-mediated inhibition of PPARg signaling pathways contribute to the growth of breast cancer cell and inhibition of ERa with PPARg activation could be a better approach for ERa-dependent breast cancer. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1149.

Endometrial carcinoma in a breast cancer patient treated with tamoxifen

The use of tamoxifen for breast cancer therapy is linked to an increased danger of developing endometrial neoplasias in postmenopausal patients receiving the drug. Understanding the molecular mechanisms of the tumorigenic activity of tamoxifen may be of great prognostic and therapeutic significance. Our study suggests that tamoxifen treatment and alterations of the K-ras proto-oncogene may occur as parallel events in carcinogenesis of the endometrium.

Third annual William L. McGuire Memorial Lecture. "Studies on the estrogen receptor in breast cancer"--20 years as a target for the treatment and prevention of cancer.

In 1973, McGuire and Chamness (In: O'Malley BW and Means AR (ed) Receptors for Reproductive Hormones, Plenum Press) summarized their work on the estrogen receptor in animal and human breast tumors, and in so doing described a target for therapeutic intervention. At that time there were no clinically useful antiestrogens, but the subsequent development of tamoxifen for breast cancer therapy has revolutionized the approach to treatment. Long-term adjuvant tamoxifen adjuvant therapy (i.e., greater than one year) has proven efficacy to enhance the survival of breast cancer patients. In addition, because there is an associated 40% decrease in contralateral breast cancer during adjuvant tamoxifen therapy and tamoxifen maintains bone density and reduces fatal myocardial infarction, clinical trials to test the worth of tamoxifen as a preventive for breast cancer in high risk women have started in the United States, United Kingdom, and Italy. Initial concerns that long-term tamoxifen causes endometrial cancer have been placed in perspective and analyzed by a review of the literature. Tamoxifen only doubles the normal risk of detecting endometrial cancer (i.e., to 2 per 1,000 tamoxifen-treated women per year), and 80% of these cases are early stage, good prognosis disease. Annual gynecological examinations and education are essential to provide reassurance for patients. The success of tamoxifen has encouraged the development of new antiestrogens to exploit the estrogen receptor as a therapeutic target. Droloxifene and TAT-59 mimic the metabolite 4-hydroxytamoxifen in having a high affinity for the estrogen receptor (Jordan et al, J Endocrinol 75:305, 1977). These drugs appear to have a pharmacological profile similar to tamoxifen. In contrast, the new pure antiestrogens have a distinct mechanism of action and will be valuable either as a first line therapy for advanced breast cancer or as a second line endocrine therapy after the failure of long-term adjuvant tamoxifen therapy. Finally, a new strategy is being developed to exploit the target site specific action of antiestrogens. Raloxifene, an antiestrogen with high affinity for the estrogen receptor but only weak estrogenicity for the uterus, prevents rat mammary tumorigenesis and maintains bone density. The drug is to be evaluated as a treatment for osteoporosis, but may also prevent the development of breast and endometrial cancer in a broad group of treated subjects. The identification of the estrogen receptor as a target for therapeutic opportunities has proved to be extremely beneficial for the control of breast cancer and has the added potential to control osteoporosis and coronary heart disease in women.

The development of tamoxifen for breast cancer therapy: a tribute to the late Arthur L. Walpole.

Tamoxifen, a nonsteroidal antiestrogen, is now the endocrine treatment most widely used in breast cancer, both in the adjuvant and advanced disease settings. Here we will trace the development of tamoxifen for advanced breast cancer in postmenopausal patients, consider the biological basis for the recent successful use of tamoxifen for long-term adjuvant therapy, and discuss the use of tamoxifen in premenopausal patients with advanced disease. In part, this will be a historical review offered as a tribute to the late Dr. Arthur L. Walpole, who must receive the chief credit for the discovery of tamoxifen and its subsequent application as an anticancer agent.