Abstracts Referenced in tamoxifen article:

Bioelectromagnetics. 1997;18(8):555-62

Environmental magnetic fields inhibit the antiproliferative action of tamoxifen and melatonin in a human breast cancer cell line.

Harland JD, Liburdy RP.

Life Science Division, Lawrence Berkeley National Laboratory, University of California at Berkeley 94720 , USA .

We have previously reported that environmental-level magnetic fields (1.2 microT [12 milligauss], 60 Hz) block the growth inhibition of the hormone melatonin (10(-9) M) on MCF-7 human breast cancer cells in vitro. We now report that the same 1.2 microT, 60 Hz magnetic fields significantly block the growth inhibitory action of pharmacological levels of tamoxifen (10(-7) M). In biophysical studies we have taken advantage of Faraday's Law of Current Induction and tested whether the 1.2 microT magnetic field or the associated induced electric field is responsible for this field effect on melatonin and tamoxifen. We observe that the magnetic field component is associated with the field blocking effect on melatonin and tamoxifen function. To our knowledge the tamoxifen studies represent the first experimental evidence for an environmental-level magnetic field modification of drug interaction with human breast cancer cells. Together, these findings provide support to the theory that environmental-level magnetic fields can act to modify the action of a drug or hormone on regulation of cell proliferation . Melatonin and tamoxifen may act through different biological pathways to down-regulate cell growth, and further studies are required to identify a specific biological site of interaction for the 1.2 microT magnetic field.

PMID: 9383244 [PubMed - indexed for MEDLINE]

Bioelectromagnetics. 2001 Feb;22(2):122-8

The influence of 1.2 microT, 60 Hz magnetic fields on melatonin- and tamoxifen-induced inhibition of MCF-7 cell growth.

Blackman CF, Benane SG, House DE.

US Environmental Protection Agency, NHEERL, Research Triangle Park , North Carolina 27711 , USA . Blackman.carl@epamail.epa.gov

We independently examined the findings of Harland and Liburdy, who reported that 1.2 microT(rms), 60 Hz magnetic fields could significantly reduce the inhibitory action of physiological levels of melatonin (10(-9) M) and of pharmacological levels of tamoxifen (10(-7) M) on the growth of MCF-7 human breast cancer cells in vitro. We used two testing protocols. In the melatonin study, the cell numbers per dish on day 7 of treatment were determined using a hemocytometer assay. In the tamoxifen study we used an expanded protocol, employing an alternative cell counting assay to characterize the cell numbers per dish on days 4, 5, 6, and 7. In both the melatonin and tamoxifen studies, cells were plated on 35 mm dishes and placed in each of two exposure chambers inside 5% CO(2) incubators. One exposure chamber was energized to produce 1.2 microT(rms), 60 Hz magnetic fields and the other chamber was not energized. Treatment was continuous until assays were performed. Cells were harvested at selected times, and enumerated without knowledge of treatment. In the melatonin study, the experiment was repeated three times, whereas in the tamoxifen study, each experiment was repeated nine times. In the melatonin study, cell numbers per dish were significantly reduced (by 16.7%) in the melatonin treated cultures after 7 days of incubation compared to control cultures, whereas in the presence of 1.2 microT(rms), 60 Hz magnetic fields, the melatonin treated cultures had the same cell populations as the control cultures. In the tamoxifen study, tamoxifen reduced the cell growth by 18.6 and 25% on days 6 and 7, respectively, in the chamber not energized, while in 1.2 microT(rms), 60 Hz fields, tamoxifen reduced the cell growth only by 8.7 and 13.1%, respectively. These results are consistent with those reported by Harland and Liburdy. A critical element of this successful replication effort was the constructive communication established and maintained with the original investigators. Bioelectromagnetics 22:122-128, 2001. Published 2001 Wiley-Liss, Inc.

PMID: 11180258 [PubMed - indexed for MEDLINE]

Eur J Obstet Gynecol Reprod Biol. 2002 May 10;102(2):188-94.

Synergistic inhibitory effects of genistein and tamoxifen on human dysplastic and malignant epithelial breast cells in vitro.

Tanos V, Brzezinski A, Drize O, Strauss N, Peretz T.

Department of Obstetrics, Hadassah Medical Center, Ein-Kerem, The Hebrew University Hospital, P.O. Box 12000, Jerusalem il-91120, Israel. tanosv@spidernet.com.cy

OBJECTIVE: Genistein is a phytoestrogen with in vitro anticancerogenic activity. We examined in vitro the effects of genistein alone, or in combination with estradiol and tamoxifen, on the growth of human dysplastic and malignant epithelial breast cell lines. METHODS: Dysplastic breast cell lines (MCF-10A(1), MCF-ANeoT, MCF-T(6)3B) and cell lines of breast cancer (MCF-7, MDA-231, MDA-435) were cultured as monolayers in RPMI 1640 medium supplemented with 10% fetal bovine serum, and L-glutamine. After preincubation of 20 h, genistein (1, 2.5, 5, 7.5 and 10 microg/ml) alone or in combination with estrogen or tamoxifen was added to the cultured cells. The cells were treated continuously for 72 h and then the growth rate was assessed colorimetrically. Stepwise multiple linear regression analysis was used to evaluate the effect of genistein, tamoxifen, and estradiol on cell proliferation. RESULTS: Genistein had a significant (dose-dependent) inhibitory effect on the proliferation of both dysplastic (P<0.0001) and malignant (P<0.0001) cells. The growth inhibition was significantly higher P<0.0001 in dysplastic cells compared to the cancer cells. Addition of tamoxifen to genistein further inhibited the proliferation of both cell types, reflecting a synergistic antiproliferative effect on dysplastic cells P<0.0001 and an additive growth inhibition effect P<0.0003 on malignant cells. Estradiol significantly (P=0.005) stimulated the growth of dysplastic cell lines while a significant (P=0.003) antiproliferative effect on growth of the malignant cells was observed. The concentration of estrogen receptor (ER) had no significant effect on growth rates and did not modulate the effects of genistein or tamoxifen. CONCLUSIONS: Genistein (1-10 microg/ml) inhibits the growth of dysplastic and malignant epithelial breast cancer cells in vitro and the addition of tamoxifen (10(-6), 10(-7)M) has a synergistic/additive inhibitory effect. These effects are not modulated by the presence of ER.

PMID: 11950489 [PubMed - indexed for MEDLINE]

Zhongguo Zhong Yao Za Zhi. 2002 Dec;27(12):936-9

[ The inhibiting effect of genistein on the growth of human breast cancer cells in vitro]

[Article in Chinese]

He FJ, Wang J, Niu JZ, Wang JF.

Lab. of Cell and Biochemystry, Beijing University of Chinese Meducine, Beijing 100029, China .

OBJECTIVE: To study the inhibiting effects of genistein on the growth of human breast cancer cell lines in vitro and its mechanisms. METHORD: Human breast cancer cell lines both MCF-7(positive estrogen receptor, ER+) and MDA-MB-231 (negative estrogen receptor, ER-) were cultured in vitro. The proliferation of cells was measured with MTT methord and the growth curve was drawn with cell count. The estrogen receptor in cells was show with immunohistochemistry. RESULT: Genistein inhibited proliferation of MCF-7 and MDA-MB-231 cell lines and inhibition was dependent on dose within some concentration range, IC50 being 32.5 mumol.L-1 and 46.8 mumol.L-1 respectively. Genisteins antiproliferation of MCF-7 was stimulated by ectogenesis estrogen but proliferation of MDA-MB-231 inhibited by geinstein was not related to estrogen. The positive signs of ER in cellular nuclei of MCF-7 cell line fed with genistein at concentration of 30 mumol.L-1 were significantly weaker than these not fed with genistein. CONCLUSION: Genistein obviously inhibits proliferation of both cell lines of MCF-7 and MDA-MB-231 in vitro and is dependent on dose. Genisteins antiproliferous effect on MCF-7 cell lines is stimulated by estrogen and this effect is related with ER, but genisteins inhibiting proliferation of MDA-MB-231 cell line is not through ER .

PMID: 12776537 [PubMed - indexed for MEDLINE]

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Am Surg. 2002 Jun;68(6):575-7; discussion 577-8.

Genistein inhibits tamoxifen effects on cell proliferation and cell cycle arrest in T47D breast cancer cells.

Jones JL, Daley BJ, Enderson BL, Zhou JR, Karlstad MD.

Department of Surgery, University of Tennessee Medical Center , Knoxville 37920-6999 , USA .

Tamoxifen is an antiestrogen used in the treatment of estrogen receptor-positive breast cancer in postmenopausal women. It functions by competitively inhibiting the estrogen receptor and inducing apoptosis and G1 cell cycle arrest. Genistein is a soy phytoestrogen that inhibits breast cancer cell growth in vitro at doses of 10 microM or above. At lower doses genistein may stimulate cell growth and entry into the cell cycle . We hypothesized that treatment with low-dose genistein would reverse the inhibitory effects of tamoxifen in estrogen-receptor-positive breast cancer cells. Cell cycle kinetics and cell proliferation in T47-D human breast cancer cells were examined after exposure to genistein and tamoxifen in a low-estrogen environment designed to mimic a post-menopausal state. Cell proliferation was assessed by a colorimetric assay. Cell cycle kinetics were determined by flow cytometry. Tamoxifen caused G1 arrest and a decrease in proliferation. Genistein reversed the inhibitory effects of tamoxifen on both proliferation and G1 arrest. Thus low-dose genistein was able to inhibit the therapeutic effects of tamoxifen in this postmenopausal model of breast cancer.

PMID: 12079141 [PubMed - indexed for MEDLINE]

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Anticancer Res. 1999 May-Jun;19(3A):1657-62

Tamoxifen and genistein synergistically down-regulate signal transduction and proliferation in estrogen receptor-negative human breast carcinoma MDA-MB-435 cells.

Shen F, Xue X, Weber G.

Laboratory for Experimental Oncology, Indiana University School of Medicine, Indianapolis 46202-5119 , USA .

PURPOSE: Tamoxifen and genistein were tested for synergism in estrogen receptor- negative human breast carcinoma MDA-MB-435 cells because the two compounds decrease signal transduction activity through different biochemical mechanisms and arrest the cell cycle at different phases. MATERIALS AND METHODS: The combination effect of tamoxifen and genistein on signal transduction was determined by measuring IP3 concentrations and on cell proliferation and colony formation by growth inhibition assay and clonogenic assay. RESULTS: In growth inhibition assays, for tamoxifen and genistein in the carcinoma cells the IC50s were (mean +/- SE) 17 +/- 0.9 and 27 +/- 1.6 microM; in clonogenic assays the LC50s were 0.9 +/- 0.4 and 12.5 +/- 1.1 microM, respectively. When tamoxifen and genistein were simultaneously added to the cells, synergism was observed in growth inhibition, in cytotoxicity and in the reduction of inositol 1,4,5-trisphosphate concentration. CONCLUSION: The synergistic down-regulation of signal transduction by tamoxifen and genistein may explain, in part at least, the synergistic antiproliferative and cytotoxic actions of the two compounds. The synergism of tamoxifen and genistein may be of interest in the clinical treatment of breast carcinoma.

PMID: 10470097 [PubMed - indexed for MEDLINE]

Cancer Res. 2002 May 1;62(9):2474-7

Dietary genistein negates the inhibitory effect of tamoxifen on growth of estrogen-dependent human breast cancer (MCF-7) cells implanted in athymic mice.

Ju YH, Doerge DR, Allred KF, Allred CD, Helferich WG.

Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana , Illinois 61801 , USA .

The use of dietary isoflavone supplements by postmenopausal women with breast cancer is increasing. We investigated interactions between the soy isoflavone, genistein, and an antiestrogen, tamoxifen (TAM), on the growth of estrogen (E)-dependent breast cancer (MCF-7) cells implanted in ovariectomized athymic mice. We hypothesized that weakly estrogenic genistein negate/overwhelm the inhibitory effect of TAM on the growth of E-dependent breast tumors. Six treatment groups were used: control (C); 0.25 mg estradiol (E2) implant (E); E2 implant + 2.5 mg TAM implant (2.5 TE); E2 implant + 2.5 mg TAM implant + 1000 ppm genistein (2.5 TEG); E2 implant + 5 mg TAM implant (5 TE), and E2 implant +5 mg TAM implant +1000 ppm genistein (5 TEG). Treatment with TAM (2.5 TE and 5 TE) suppressed E2-stimulated MCF-7 tumor growth in ovariectomized athymic mice. Dietary genistein negated/overwhelmed the inhibitory effect of TAM on MCF-7 tumor growth, lowered E2 level in plasma, and increased expression of E-responsive genes (e.g., pS2, PR, and cyclin D1). Therefore, caution is warranted for postmenopausal women consuming dietary genistein while on TAM therapy for E-responsive breast cancer.

PMID: 11980635 [PubMed - indexed for MEDLINE]

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Cancer Res. 1999 Jan 1;59(1):44-7.

Synergistic effects of (--)-epigallocatechin gallate with (--)-epicatechin, sulindac, or tamoxifen on cancer-preventive activity in the human lung cancer cell line PC-9.

Suganuma M, Okabe S, Kai Y, Sueoka N, Sueoka E, Fujiki H.

Saitama Cancer Center Research Institute, Japan .

The study on incorporation of [3H](-)-epigallocatechin gallate (EGCG) into human lung cancer cell line PC-9 indicated that the [3H]EGCG incorporation was significantly enhanced by (-)-epicatechin, an inert tea polyphenol without a galloyl moiety. (-)-Epicatechin enhanced apoptosis, growth inhibition of PC-9 cells, and inhibition of tumor necrosis factor-alpha release from BALB/c-3T3 cells by EGCG and other tea polyphenols with a galloyl moiety in a dose-dependent manner. Moreover, the effects of EGCG on induction of apoptosis were also synergistically enhanced by other cancer-preventive agents, such as sulindac and tamoxifen. This paper reports significant evidence that whole green tea is a more reasonable mixture of tea polyphenols for cancer prevention in humans than EGCG alone and that it is even more effective when it is used in combination with other cancer preventives.

PMID: 9892181 [PubMed - indexed for MEDLINE]

Int J Oncol. 2004 May;24(5):1297-304.

Reduction of CWR22 prostate tumor xenograft growth by combined tamoxifen-quercetin treatment is associated with inhibition of angiogenesis and cellular proliferation.

Ma ZS, Huynh TH, Ng CP, Do PT, Nguyen TH, Huynh H.

Laboratory of Molecular Endocrinology, Division of Cellular and Molecular Research, National Cancer Center of Singapore , Singapore 169610.

Combination chemotherapy is increasingly practiced for the treatment of malignant prostate cancers. The aim of this study was to evaluate the in vivo efficacy of combined tamoxifen and quercetin in prostate tumor xenografts . Severe combined immune deficient (SCID) mice inoculated with CWR22 prostate tumor cells were treated with either tamoxifen (10 mg/kg/week), quercetin (200 mg/kg/day) or combined tamoxifen-quercetin for 28 days. Tamoxifen or quercetin alone exhibited a moderate antitumor activity. Tamoxifen decreased the Ki-67 index by 52.4%, reduced the vascular endothelial growth factor (VEGF) 121 and VEGF165 mRNA by 18.6 and 21.8%, respectively, and suppressed the blood vessel formation, while quercetin modulated the expression and phosphorylation of cdc-2 and cyclin B1, and inhibited the Ki-67 index by 66.0%. Combined tamoxifen-quercetin effectively delayed the appearance of tumors, inhibited the final tumor volume by 73.3% and reduced the endpoint tumor weight by 67.1% (p<0.05). The Ki-67 index, VEGF121, VEGF165 mRNA and microvessel density (MVD) were decreased by 66.9, 22.1, 40.1 and 59.0%, respectively, by the combined treatment. These findings indicate that tamoxifen inhibits CWR22 prostate tumor by modulating the angiogenesis and its antineoplastic effects can be potentiated by combined use with quercetin.

PMID: 15067354 [PubMed - in process]

Melanoma Res. 2001 Oct;11(5):469-76.

Quercetin and tamoxifen sensitize human melanoma cells to hyperthermia.

Piantelli M, Tatone D, Castrilli G, Savini F, Maggiano N, Larocca LM, Ranelletti FO, Natali PG.

Department of Oncology and Neurosciences, 'G. D'Annunzio' University, Chieti , Italy .

Hyperthermia produces regression of human cancer. Because hyperthermia has produced only limited results, attention has focused on searching for substances able to sensitize tumour cells to the effects of hyperthermia. The flavonoid quercetin has been reported to be a hyperthermic sensitizer in ovarian and uterine cervical tumours and in leukaemia . Quercetin and tamoxifen inhibit melanoma cell growth. We therefore investigated whether quercetin and tamoxifen can sensitize M10, M14 and MNT1 human melanoma cells to hyperthermia. We observed that both quercetin and tamoxifen synergize with hyperthermia (42.5 degrees C) in reducing the clonogenic activity of M14 and MNT1 and in inducing apoptotic cell death in all three cell lines. As revealed by flow cytometric and Northern blot analyses, quercetin and tamoxifen reduced heat shock protein-70 expression at both protein and mRNA levels. Our results suggest that quercetin and tamoxifen can be usefully combined with hyperthermia in the therapy of recurrent and/or metastatic melanoma.

PMID: 11595883 [PubMed - indexed for MEDLINE]

Melanoma Res. 1998 Aug;8(4):313-22

Erratum in:

Melanoma Res 1999 Oct;9(5):530.

Sensitivity of human melanoma cells to oestrogens, tamoxifen and quercetin: is there any relationship with type I and II oestrogen binding site expression?

Lama G, Angelucci C, Bruzzese N, Iacopino F, Nori SL, D'Atri S, Turriziani M, Bonmassar E, Sica G.

Istituto di Istologia ed Embriologia, Universita Cattolica del Sacro Cuore, Rome , Italy .

We investigated the effect of oestrogens, anti-oestrogens and flavonoids on the growth of a human melanoma cell line (SK-Mel-28) and, at the same time, the presence of both type I oestrogen receptors (ERs) and type II oestrogen binding sites (type II EBS) to gain a fuller picture of the relationship between melanoma cell proliferation and receptor status. 17beta-Oestradiol (E2) and the flavonoid quercetin (Q) produced a marked inhibition of proliferation, but only at the highest dose used (10(-5) M) and only when added daily to the medium. Diethylstilboestrol (DES) (10(-5) M) was effective in inhibiting cell growth when the medium was renewed every 3 days and produced a more pronounced reduction when added daily to the medium. Tamoxifen (TAM) inhibited cell proliferation at a dose starting from 10(-7) M when the medium was renewed every 3 days. When added daily to the medium, it did not induce a greater inhibitory effect and it was cytotoxic at 5 x 10(-6) M and 10(-5) M. The antiproliferative effect of E2, DES and Q did not seem to be dependent on their interaction with ERs, which were minimally detected in SK-Mel-28 in both immunocytochemical and biochemical assays. Our model revealed, through a biochemical assay, a large number of type II EBSs which could be involved in the anti-oestrogen action, but this does not exclude the involvement of other mechanisms. Finally, TAM (10(-5) M) appeared to reduce the activity of the DNA repair enzyme O6-alkylguanine-DNA alkyltransferase, an effect that could be interesting from the point of view of the therapeutic efficacy of alkylating agents.

PMID: 9764806 [PubMed - indexed for MEDLINE]

Breast Cancer Res Treat. 2003 Jun;79(3):301-12.

Inositol hexaphosphate (IP6) enhances the anti-proliferative effects of adriamycin and tamoxifen in breast cancer.

Tantivejkul K, Vucenik I, Eiseman J, Shamsuddin AM.

Department of Pathology, University of Maryland School of Medicine , Baltimore , MD 21201 , USA .

The current treatment of breast carcinomas recognizes the importance of combination therapy in order to increase efficacy and decrease side effects of conventional chemotherapy. Inositol hexaphosphate (IP6), a naturally occurring polyphosphorylated carbohydrate, has shown a significant anti-cancer effect in various in vivo and in vitro models, including breast cancer. In this study, we investigated the in vitro growth inhibitory activity of IP6 in combination with adriamycin or tamoxifen, against three human breast cancer cell lines: estrogen receptor (ER) alpha-positive MCF-7, ER alpha-negative MDA-MB 231 and adriamycin-resistant MCF-7 (MCF-7/Adr) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Much lower concentrations of IP6 were required after 96 h of treatment to inhibit the growth of MCF-7/Adr cells than MCF-7 cells; the IC50 for MCF-7/Adr cells was 1.26 mM compared to 4.18 mM for MCF-7 cells. The ER-negative MDA-MB 231 cells were also highly sensitive to IP6 with IC50 being 1.32 mM. To determine the effects of IP6 in combination with either adriamycin or tamoxifen, the median effect principle and Webb's fraction method were used to determine the combination index (CI) and the statistical differences. Growth suppression was markedly increased when IP6 was administered prior to the addition of adriamycin, especially against MCF-7 cells (CI = 0.175 and p < 0.0001). Synergism was also observed when IP6 was administered after tamoxifen in all three cell lines studied (CI = 0.343, 0.701 and 0.819; p < 0.0001, p = 0.0003 and 0.0241 for MCF-7/Adr, MCF-7 and MDA-MB 231, respectively). The growth of primary culture of breast cancer cells from patients was inhibited by IP6 with LC50 values ranging from 0.91 to 5.75 mM (n = 10). Our data not only confirm that IP6 alone inhibits the growth of breast cancer cells; but it also acts synergistically with adriamycin or tamoxifen, being particularly effective against ER alpha-negative cells and adriamycin-resistant cell lines.

PMID: 12846414 [PubMed - indexed for MEDLINE]

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Carcinogenesis. 2003 May;24(5):869-73.

Resveratrol activates adenylyl-cyclase in human breast cancer cells: a novel, estrogen receptor-independent cytostatic mechanism.

El-Mowafy AM, Alkhalaf M.

Department of Applied Therapeutics, Faculty of Pharmacy, Health Sciences Center, Kuwait University, PO Box 24923, Safat 13110, Kuwait. aelmowafy@hsc.kuniv.edu.kw

Resveratrol (RSVL) is a well-established chemopreventive agent in human breast cancer models. The molecular basis of its action is far less characterized. We investigated the effects of RSVL on activity of adenylate- and guanylate-cyclase (AC, GC) enzymes; two known cytostatic cascades in MCF-7 breast cancer cells. RSVL increased cAMP levels in both time- and concentration-dependent manners (t(1/2), 6.2 min; EC(50) 0.8 micro M). In contrast, it had no effect on cGMP levels . The stimulatory effects for RSVL on AC were not altered either by the protein synthesis inhibitor (actinomycin-D, 5 micro M) or the estrogen-receptor (ER) blockers (tamoxifen and ICI182,780, 1 micro M each). Likewise, cAMP formation by RSVL was insensitive to either the broad-spectrum phosphodiesterase (PDE) inhibitor (IBMX, 0.5 mM) or the cAMP-specific PDE inhibitor (rolipram, 10 micro M). Instead, these PDE inhibitors significantly augmented maximal cAMP formation by RSVL. Parallel experiments showed that either RSVL or rolipram inhibited the proliferation of these cells in a concentration-responsive manner. Further, concurrent treatment with RSVL and rolipram significantly enhanced their individual cytotoxic responses. The antiproliferative effects were appreciably reversed by the kinase-A inhibitors, Rp-cAMPS (100-300 micro M) or KT-5720 (10 micro M). Pretreatment with the cPLA(2) inhibitor arachidonyl trifluoromethyl ketone (10 micro M) markedly antagonized the cytotoxic effects of RSVL, but had no effect on that of rolipram. Altogether, the present study demonstrates, for the first time, that the chemotherapeutic agent RSVL is an agonist for the cAMP/kinase-A system, a documented pro-apoptic and cell-cycle suppressor in breast cancer cells.

PMID: 12771030 [PubMed - indexed for MEDLINE]

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Melatonin:

J Pineal Res. 2002 Aug;33(1):8-13.

Potentiation of antiproliferative effects of tamoxifen and ethanol on mouse hepatoma cells by melatonin: possible involvement of mitogen-activated protein kinase and induction of apoptosis.

Hermann R, Podhajsky S, Jungnickel S, Lerchl A.

Institute of Zoology II, University of Karlsruhe, Karlsruhe, Germany, School of Engineering and Science, International University Bremen, Bremen, Germany.

Melatonin, the major secretory product of the pineal gland, is in focus of many research areas because of its ability to scavenge free oxygen radicals and thereby protect cells and tissues from radical damage. Some studies suggest melatonin may be a possible therapeutic agent with potential clinical applications against pathological states due to reactive oxygen species. Here, we investigated the effects of melatonin on the mouse hepatoma cell line HEPA 1-6, coincubated with ethanol, and tamoxifen, respectively. Cell proliferation rates were detected by the 3-[4,5 dimethylthiazol-2-y1]-2,5-diphenyltetrazolium bromide (MTT) proliferation assay. A dose-dependent inhibition of the proliferative activity by melatonin was observed from 640 microM to 3 mM, which was significantly higher (P < 0.01) than with the solvent (ethanol) alone. Concentrations of 320 microM and less had no effect on cell proliferation. This antiproliferative effect might be because of the prolonged activation of mitogen-activated protein kinase which was activated by phosphorylation 15 min after the induction with melatonin. Furthermore, apoptosis was found to be enhanced by melatonin (75% more than with the solvent alone, P < 0.001). Finally, we show that the inhibitory effect of tamoxifen (25 microM) is markedly enhanced by the coincubation with melatonin (1.3 mM) up to 75% (P < 0.001). These data show that the antiproliferative effects of tamoxifen and ethanol, respectively, on mouse hepatoma cell line HEPA 1-6 are enhanced by melatonin. Although at the conditions described here the antiproliferative effects of melatonin occur at supraphysiological concentrations, these data may help to support clinical studies where melatonin is given simultaneously with tamoxifen or other standard chemotherapeutica.

PMID: 12121480 [PubMed - indexed for MEDLINE]

J Clin Endocrinol Metab. 1992 Aug;75(2):669-70

Melatonin augments the sensitivity of MCF-7 human breast cancer cells to tamoxifen in vitro.

Wilson ST , Blask DE , Lemus-Wilson AM.

Mary Imogene Bassett Hospital, Research Institute, Cooperstown , New York 13326-1394 .

Cultured MCF-7 human breast cancer cells were pre-exposed to either melatonin (232 ng/mL) or vehicle for 24 hrs prior to being washed and then re-exposed to either ethanol-vehicle or varying concentrations of tamoxifen (37.1 ng/mL, 3.71 micrograms/mL, 371 micrograms/mL) or melatonin (2.32 pg/mL, 232 ng/mL, 23.2 ng/mL) for 5 additional days. Only 371 ng/mL tamoxifen caused a 38% growth inhibition of cells pre-exposed to vehicle whereas all concentrations of tamoxifen inhibited the growth of melatonin pre-exposed cells by 28% to 61% in a dose-dependent manner. Melatonin pre-exposure, potentiated the inhibitory effect of only 232 ng/mL melatonin. Comparison of IC50 values indicate that tamoxifen is approximately a 100 times more potent inhibitor of breast cancer cell growth following the pretreatment of cells with a physiological concentration of melatonin. These results indicate that melatonin has the capability to augment the inhibitory actions of tamoxifen, and to a lesser extent itself, on human breast cancer cell growth.

PMID: 1639964 [PubMed - indexed for MEDLINE]

Pol J Pathol. 2002;53(2):59-65.

Effect of melatonin and all-trans retinoic acid on the proliferation and induction of the apoptotic pathway in the culture of human breast cancer cell line MCF-7.

Czeczuga-Semeniuk E, Wolczynski S, Anchim T, Dzieciol J, Dabrowska M, Pietruczuk M.

Department of Gynaecological Endocrinology, Medical Academy , Bialystok .

Melatonin in the in vitro conditions inhibits cell growth and proliferation of estrogen sensitive (ER+) cell line MCF-7 in culture. In the present study, during a 48-hour incubation melatonin at a concentration of 10(-5) M inhibited [3H]thymidine incorporation into cancer cells at the level of 69.52% +/- 10.99. Melatonin had no inhibitory effect on the physiological stimulatory action of estradiol. Tamoxifen added to the medium modulated the melatonin action only when the latter was added 24 hours after tamoxifen (46.45% +/- 4.40, p < 0.05). Tretinoin added to the culture caused a statistically significant reduction in [3H]thymidine incorporation into the cancer cells, compared to the melatonin and tretinoin groups, when treatment with retinoid was synergistic (39.05% +/- 5.44, p < 0.05) or sequential (tretinoin and after 24 h melatonin) (39.96% +/- 1.55, p < 0.05). This was confirmed by immunocytochemical investigations, which showed a statistically significant reduction in the percentage of PCNA- and Ki67-positive cells. Apart from the inhibitory effect on MCF-7 cell proliferation retinoids induce the apoptotic pathway in a dose-dependent manner. Melatonin added to the culture enhances this effect, which may indicate the potential for the use of both substances in the treatment of breast cancer in women.

PMID: 12140868 [PubMed - indexed for MEDLINE]

Retenoic Acid

Int J Oncol. 2002 Jan;20(1):89-96.

Combined in vitro anti-tumoral action of tamoxifen and retinoic acid derivatives in hepatoma cells.

Herold C, Ganslmayer M, Ocker M, Hermann M, Hahn EG, Schuppan D.

Department of Medicine I, D-91054 Erlangen , Germany . christoph.herold@med1.imed.uni-erlangen.de

Chemotherapy does not have a prominent role in the treatment of hepatoma. However, an acyclic retinoid prevented tumor recurrence post-hepatectomy, and tamoxifen (TAM) induced apoptosis in tumor cells. Combination therapy of these agents on proliferation and apoptosis of hepatoma cells has not been explored. HepG2, Hep1B, Hepa1-6 and MH1C1 hepatoma cells were incubated with TAM, 9-cis- and all-trans retinoic acid (CRA, ATRA, respectively) alone or in combination. Proliferation rate was assessed and apoptosis was analyzed by flow cytometry, immunostaining, caspase activity assays and the expression of apoptosis- and/or cell cycle-related molecules. CRA and TAM, but not ATRA monotherapy were moderately effective. Apoptosis was accompanied by upregulation of caspase 3 and 8 activity, and increased p27, bax, caspase 3 expression, while the levels of p21cip/waf and bcl-2 were unchanged or decreased. Combination therapy enhanced apoptosis from a maximum of 60% after monotherapy to more than 90% after 96 h in all cell types. Pro-apoptotic effects were paralleled by inhibition of proliferation. Combination of TAM and CRA, but not ATRA, have an additive to synergistic anti-proliferative and pro-apoptotic effect on HCC cells. This justifies trials for HCC using combinations of these biological response modifiers.

PMID: 11743647 [PubMed - indexed for MEDLINE]

Anticancer Res. 2004 Mar-Apr;24(2C):1255-60.

Treatment with all-trans retinoic acid plus tamoxifen and vitamin E in advanced hepatocellular carcinoma.

Clerici C, Castellani D, Russo G, Fiorucci S, Sabatino G, Giuliano V, Gentili G, Morelli O, Raffo P, Baldoni M, Morelli A, Toma S.

Clinic of Gastroenterology and Hepatology, University of Perugia , Italy . clerici@unipg.it

BACKGROUND: Low serum retinol and hepatic tocopherol levels correlate with hepatocellular carcinoma (HCC) risk . Antiestrogen tamoxifen seems useful in HCC patients. A pilot study was performed to evaluate the effect of all-trans retinoic acid associated with tamoxifen and vitamin E on patients with advanced HCC. PATIENTS AND METHODS: Fifteen consecutive patients with advanced HCC were included in the study. Patients were evaluated for survival, quality of life, liver function, tumor mass, toxicity related to the treatment and retinoid receptors in liver biopsies. RESULTS: The median survival of our patients was 22 months. Pain and asthenia were improved in the majority of patients. Every patient with baseline elevated liver enzymes showed an improvement in liver function. RAR-alpha, RXR-alpha, RAR-beta and RAR-gamma receptors were demonstrated in 100%, 73%, 47% and 40%, respectively. CONCLUSION : A combination therapy of all-trans retinoic acid, tamoxifen and vitamin E increases the survival rate and ameliorates the clinical outcome in patients with inoperable HCC.

Publication Types:

Clinical Trial

PMID: 15154656 [PubMed - indexed for MEDLINE]

Vitamin E:

J Nutr. 1997 Mar;127(3):544S-548S.

Inhibition of proliferation of estrogen receptor-negative MDA-MB-435 and -positive MCF-7 human breast cancer cells by palm oil tocotrienols and tamoxifen, alone and in combination.

Guthrie N, Gapor A, Chambers AF, Carroll KK.

Department of Biochemistry, The University of Western Ontario , London , Canada .

Tocotrienols are a form of vitamin E, having an unsaturated isoprenoid side-chain rather than the saturated side-chain of tocopherols. The tocotrienol-rich fraction (TRF) from palm oil contains alpha-tocopherol and a mixture of alpha-, gamma- and delta-tocotrienols. Earlier studies have shown that tocotrienols display anticancer activity. We previously reported that TRF, alpha-, gamma- and delta-tocotrienols inhibited proliferation of estrogen receptor-negative MDA-MB-435 human breast cancer cells with 50% inhibitory concentrations (IC50) of 180, 90, 30 and 90 microg/mL, respectively, whereas alpha-tocopherol had no effect at concentrations up to 500 microg/mL. Further experiments with estrogen receptor-positive MCF-7 cells showed that tocotrienols also inhibited their proliferation, as measured by [3H] thymidine incorporation. The IC50s for TRF, alpha-tocopherol, alpha-, gamma- and delta-tocotrienols were 4, 125, 6, 2 and 2 microg/mL, respectively. Tamoxifen, a widely used synthetic antiestrogen inhibits the growth of MCF-7 cells with an IC50 of 0.04 microg/mL. We tested 1:1 combinations of TRF, alpha-tocopherol and the individual tocotrienols with tamoxifen in both cell lines. In the MDA-MB-435 cells, all of the combinations were found to be synergistic. In the MCF-7 cells, only 1:1 combinations of gamma- or delta-tocotrienol with tamoxifen showed a synergistic inhibitory effect on the proliferative rate and growth of the cells. The inhibition by tocotrienols was not overcome by addition of excess estradiol to the medium. These results suggest that tocotrienols are effective inhibitors of both estrogen receptor-negative and -positive cells and that combinations with tamoxifen should be considered as a possible improvement in breast cancer therapy.

PMID: 9082043 [PubMed - indexed for MEDLINE]

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