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Schultze E, Collares T, Lucas CG, Seixas FK. Synergistic and additive effects of ATRA in combination with different anti-tumor compounds. Chem Biol Interact 2018; 285:69-75. [DOI: 10.1016/j.cbi.2018.02.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 01/26/2018] [Accepted: 02/15/2018] [Indexed: 12/12/2022]
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2
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Xi J, He S, Wei C, Shen W, Liu J, Li K, Zhang Y, Yue J, Yang Z. Negative effects of retinoic acid on stem cell niche of mouse incisor. Stem Cell Res 2016; 17:489-497. [PMID: 27771497 DOI: 10.1016/j.scr.2016.09.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 09/27/2016] [Accepted: 09/27/2016] [Indexed: 01/01/2023] Open
Abstract
The continuous growth of mouse incisors depends on epithelial stem cells (SCs) residing in the SC niche, called labial cervical loop (LaCL). The homeostasis of the SCs is subtly regulated by complex signaling networks. In this study, we focus on retinoic acid (RA), a derivative of Vitamin A and a known pivotal signaling molecule in controlling the functions of stem cells (SCs). We analyzed the expression profiles of several key molecules of the RA signaling pathway in cultured incisor explants upon exogenous RA treatment. The expression patterns of these molecules suggested a negative feedback regulation of RA signaling in the developing incisor. We demonstrated that exogenous RA had negative effects on incisor SCs and that this was accompanied by downregulation of Fgf10, a mesenchymally expressed SC survival factor in the mouse incisor. Supplement of Fgf10 in incisor cultures completely blocked RA effects by antagonizing apoptosis and increasing proliferation in LaCL epithelial SCs. In addition, Fgf10 obviously antagonized RA-induced downregulation of the SC marker Sox2 in incisor epithelial SCs. Our findings suggest that the negative effects of RA on incisor SCs result from inhibition of mesenchymal Fgf10.
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Affiliation(s)
- Jinlei Xi
- Department of Pharmacy, Wuhan University of Science and Technology School of Medicine, 2 West Huangjiahu Road, Wuhan, Hubei 430065, China
| | - Shijing He
- Department of Pharmacology, Wuhan University School of Basic Medical Science, 185 Donghu Road, Wuhan, Hubei 430071, China
| | - Cizhao Wei
- Department of Pharmacology, Wuhan University School of Basic Medical Science, 185 Donghu Road, Wuhan, Hubei 430071, China
| | - Wanyao Shen
- Department of Pharmacology, Wuhan University School of Basic Medical Science, 185 Donghu Road, Wuhan, Hubei 430071, China
| | - Juan Liu
- Department of Pharmacy, Wuhan University of Science and Technology School of Medicine, 2 West Huangjiahu Road, Wuhan, Hubei 430065, China
| | - Ke Li
- Department of Pharmacology, Wuhan University School of Basic Medical Science, 185 Donghu Road, Wuhan, Hubei 430071, China
| | - Yufeng Zhang
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) & Key Laboratory of Oral Biomedicine Ministry of Education, School & Hospital of Stomatology, Wuhan University, Wuhan 430079, China
| | - Jiang Yue
- Department of Pharmacology, Wuhan University School of Basic Medical Science, 185 Donghu Road, Wuhan, Hubei 430071, China
| | - Zheqiong Yang
- Department of Pharmacology, Wuhan University School of Basic Medical Science, 185 Donghu Road, Wuhan, Hubei 430071, China.
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Ribeiro MPC, Santos AE, Custódio JBA. Mitochondria: the gateway for tamoxifen-induced liver injury. Toxicology 2014; 323:10-8. [PMID: 24881593 DOI: 10.1016/j.tox.2014.05.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 05/14/2014] [Accepted: 05/28/2014] [Indexed: 12/13/2022]
Abstract
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.
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Affiliation(s)
- Mariana P C Ribeiro
- Center for Neuroscience and Cell Biology, University of Coimbra, 3000-354 Coimbra, Portugal; Laboratory of Biochemistry, Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Armanda E Santos
- Center for Neuroscience and Cell Biology, University of Coimbra, 3000-354 Coimbra, Portugal; Laboratory of Biochemistry, Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - José B A Custódio
- Center for Neuroscience and Cell Biology, University of Coimbra, 3000-354 Coimbra, Portugal; Laboratory of Biochemistry, Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal.
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Ribeiro MPC, Santos AE, Custódio JBA. Interplay between estrogen and retinoid signaling in breast cancer--current and future perspectives. Cancer Lett 2014; 353:17-24. [PMID: 25042865 DOI: 10.1016/j.canlet.2014.07.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 06/17/2014] [Accepted: 07/08/2014] [Indexed: 01/11/2023]
Abstract
All-trans-retinoic acid (RA) is a promising agent for breast cancer treatment, but it induces several adverse effects and the few clinical trials performed up to now in breast cancer patients have provided disappointing results. The combination of RA and antiestrogenic compounds, such as tamoxifen, synergistically decreases the proliferation of breast cancer cells and an interplay between retinoid and estrogen signaling has begun to be unraveled, turning these combinations into an appealing strategy for breast cancer treatment. This review focus on the current knowledge regarding the interplay between retinoid and estrogen signaling in breast cancer and the combinations of RA with antiestrogens, aiming their future utilization in cancer therapy.
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Affiliation(s)
- Mariana P C Ribeiro
- Center for Neuroscience and Cell Biology, University of Coimbra, 3000-354 Coimbra, Portugal; Laboratory of Biochemistry, Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal.
| | - Armanda E Santos
- Center for Neuroscience and Cell Biology, University of Coimbra, 3000-354 Coimbra, Portugal; Laboratory of Biochemistry, Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - José B A Custódio
- Center for Neuroscience and Cell Biology, University of Coimbra, 3000-354 Coimbra, Portugal; Laboratory of Biochemistry, Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
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5
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Kamal AHM, Han BS, Choi JS, Cho K, Kim SY, Kim WK, Lee SC, Bae KH. Proteomic analysis of the effect of retinoic acids on the human breast cancer cell line MCF-7. Mol Biol Rep 2014; 41:3499-507. [DOI: 10.1007/s11033-014-3212-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 01/27/2014] [Indexed: 02/02/2023]
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Ribeiro MP, Santos AE, Santos MS, Custódio JB. Effects of all-trans-retinoic acid on the permeability transition and bioenergetic functions of rat liver mitochondria in combination with endoxifen. Life Sci 2013; 93:96-107. [DOI: 10.1016/j.lfs.2013.05.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 05/09/2013] [Accepted: 05/29/2013] [Indexed: 11/26/2022]
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Ribeiro MPC, Silva FSG, Paixão J, Santos AE, Custódio JBA. The combination of the antiestrogen endoxifen with all-trans-retinoic acid has anti-proliferative and anti-migration effects on melanoma cells without inducing significant toxicity in non-neoplasic cells. Eur J Pharmacol 2013; 715:354-62. [PMID: 23712006 DOI: 10.1016/j.ejphar.2013.04.038] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Revised: 04/24/2013] [Accepted: 04/26/2013] [Indexed: 10/26/2022]
Abstract
Melanoma incidence is dramatically increasing and the available treatments beyond partial efficacy have severe side effects. Retinoids are promising anticancer agents, but their clinical use has been limited by their toxicity, although a combination with other agents can possibly generate a therapeutic action at lower dosage. Thus, we investigated the effects of all-trans-retinoic acid combined with the antiestrogen endoxifen on melanoma cell proliferation and the effects were compared with its pro-drug tamoxifen. Moreover, we evaluated the effects of these combinations on non-neoplasic cells and assessed mitochondrial bioenergetic functions, to predict their potential toxicity. Individually, all-trans-retinoic acid and the antiestrogens endoxifen and tamoxifen decreased melanoma cell biomass, cell viability and DNA synthesis, without increased cell death, suggesting that the compounds inhibited cell proliferation. Noteworthy, endoxifen decreased cell proliferation more efficiently than tamoxifen. The combination of endoxifen with all-trans-retinoic acid enhanced the antiproliferative effects of the compounds individually more potently than tamoxifen, which did not enhance the effects induced by all-trans-retinoic acid alone, and blocked cell cycle progression in G1. Moreover, the combination of all-trans-retinoic acid with endoxifen significantly decreased melanoma cells migration, whereas the combination with tamoxifen did not present significant effects. At the concentrations used the compounds did not induce cytotoxicity in non-neoplasic cells and liver mitochondrial bioenergetic function was not affected. Altogether, our results show for the first time that a combined treatment of all-trans-retinoic acid with endoxifen may provide an anti-proliferative and anti-migration effect upon melanoma cells without major toxicity, offering a powerful therapeutic strategy for malignant melanoma.
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Affiliation(s)
- Mariana P C Ribeiro
- Center for Neuroscience and Cell Biology, University of Coimbra, 3000-354 Coimbra, Portugal
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Synergistic antitumor activity of lapatinib and retinoids on a novel subtype of breast cancer with coamplification of ERBB2 and RARA. Oncogene 2011; 31:3431-43. [DOI: 10.1038/onc.2011.506] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Salazar MD, Ratnam M, Patki M, Kisovic I, Trumbly R, Iman M, Ratnam M. During hormone depletion or tamoxifen treatment of breast cancer cells the estrogen receptor apoprotein supports cell cycling through the retinoic acid receptor α1 apoprotein. Breast Cancer Res 2011; 13:R18. [PMID: 21299862 PMCID: PMC3109587 DOI: 10.1186/bcr2827] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Revised: 01/07/2011] [Accepted: 02/07/2011] [Indexed: 12/15/2022] Open
Abstract
Introduction Current hormonal adjuvant therapies for breast cancer including tamoxifen treatment and estrogen depletion are overall tumoristatic and are severely limited by the frequent recurrence of the tumors. Regardless of the resistance mechanism, development and progression of the resistant tumors requires the persistence of a basal level of cycling cells during the treatment for which the underlying causes are unclear. Methods In estrogen-sensitive breast cancer cells the effects of hormone depletion and treatment with estrogen, tamoxifen, all-trans retinoic acid (ATRA), fulvestrant, estrogen receptor α (ER) siRNA or retinoic acid receptor α (RARα) siRNA were studied by examining cell growth and cycling, apoptosis, various mRNA and protein expression levels, mRNA profiles and known chromatin associations of RAR. RARα subtype expression was also examined in breast cancer cell lines and tumors by competitive PCR. Results Basal proliferation persisted in estrogen-sensitive breast cancer cells grown in hormone depleted conditioned media without or with 4-hydroxytamoxifen (OH-Tam). Downregulating ER using either siRNA or fulvestrant inhibited basal proliferation by promoting cell cycle arrest, without enrichment for ErbB2/3+ overexpressing cells. The basal expression of RARα1, the only RARα isoform that was expressed in breast cancer cell lines and in most breast tumors, was supported by apo-ER but was unaffected by OH-Tam; RAR-β and -γ were not regulated by apo-ER. Depleting basal RARα1 reproduced the antiproliferative effect of depleting ER whereas its restoration in the ER depleted cells partially rescued the basal cycling. The overlapping tamoxifen-insensitive gene regulation by apo-ER and apo-RARα1 comprised activation of mainly genes promoting cell cycle and mitosis and suppression of genes involved in growth inhibition; these target genes were generally insensitive to ATRA but were enriched in RAR binding sites in associated chromatin regions. Conclusions In hormone-sensitive breast cancer, ER can support a basal fraction of S-phase cells (i) without obvious association with ErbB2/3 expression, (ii) by mechanisms unaffected by hormone depletion or OH-Tam and (iii) through maintenance of the basal expression of apo-RARα1 to regulate a set of ATRA-insensitive genes. Since isoform 1 of RARα is genetically redundant, its targeted inactivation or downregulation should be further investigated as a potential means of enhancing hormonal adjuvant therapy.
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Affiliation(s)
- Marcela D Salazar
- Department of Biochemistry and Cancer Biology, Medical University of Ohio, 3000 Arlington Avenue, Toledo, OH 43614, USA
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Schultz DJ, Wickramasinghe NS, Ivanova MM, Isaacs SM, Dougherty SM, Imbert-Fernandez Y, Cunningham AR, Chen C, Klinge CM. Anacardic acid inhibits estrogen receptor alpha-DNA binding and reduces target gene transcription and breast cancer cell proliferation. Mol Cancer Ther 2010; 9:594-605. [PMID: 20197399 DOI: 10.1158/1535-7163.mct-09-0978] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Anacardic acid (AnAc; 2-hydroxy-6-alkylbenzoic acid) is a dietary and medicinal phytochemical with established anticancer activity in cell and animal models. The mechanisms by which AnAc inhibits cancer cell proliferation remain undefined. AnAc 24:1(omega5) was purified from geranium (Pelargonium x hortorum) and shown to inhibit the proliferation of estrogen receptor alpha (ERalpha)-positive MCF-7 and endocrine-resistant LCC9 and LY2 breast cancer cells with greater efficacy than ERalpha-negative primary human breast epithelial cells, MCF-10A normal breast epithelial cells, and MDA-MB-231 basal-like breast cancer cells. AnAc 24:1(omega5) inhibited cell cycle progression and induced apoptosis in a cell-specific manner. AnAc 24:1(omega5) inhibited estradiol (E(2))-induced estrogen response element (ERE) reporter activity and transcription of the endogenous E(2) target genes pS2, cyclin D1, and cathepsin D in MCF-7 cells. AnAc 24:1(omega5) did not compete with E(2) for ERalpha or ERbeta binding, nor did AnAc 24:1(omega5) reduce ERalpha or ERbeta steady-state protein levels in MCF-7 cells; rather, AnAc 24:1(omega5) inhibited ER-ERE binding in vitro. Virtual screening with the molecular docking software Surflex evaluated AnAc 24:1(omega5) interaction with ERalpha ligand binding (LBD) and DNA binding (DBD) domains in conjunction with experimental validation. Molecular modeling revealed AnAc 24:1(omega5) interaction with the ERalpha DBD but not the LBD. Chromatin immunoprecipitation experiments revealed that AnAc 24:1(omega5) inhibited E(2)-ERalpha interaction with the endogenous pS2 gene promoter region containing an ERE. These data indicate that AnAc 24:1(omega5) inhibits cell proliferation, cell cycle progression, and apoptosis in an ER-dependent manner by reducing ER-DNA interaction and inhibiting ER-mediated transcriptional responses.
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Affiliation(s)
- David J Schultz
- Department of Biology, University of Louisville School of Medicine, Louisville, Kentucky 40292, USA
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Soto-Cerrato V, Viñals F, Lambert JR, Pérez-Tomás R. The anticancer agent prodigiosin induces p21WAF1/CIP1 expression via transforming growth factor-beta receptor pathway. Biochem Pharmacol 2007; 74:1340-9. [PMID: 17765876 DOI: 10.1016/j.bcp.2007.07.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 07/04/2007] [Accepted: 07/05/2007] [Indexed: 01/22/2023]
Abstract
The anticancer agent prodigiosin has been shown to act as an efficient immunosuppressant, eliciting cell cycle arrest at non-cytotoxic concentrations, and potent proapoptotic and antimetastatic effects at higher concentrations. Gene expression profiling of MCF-7 cells after treatment with a non-cytotoxic concentration of prodigiosin showed that expression of the p21WAF1/CIP1 gene, a negative cell cycle regulator was induced. In this study, we show that prodigiosin induces p21 expression leading to cell cycle blockade. Subsequently, we attempted to elucidate the molecular mechanisms involved in prodigiosin-mediated p21 gene expression. We demonstrate that prodigiosin induces p21 in a p53-independent manner as prodigiosin induced p21 in cells with both mutated and dominant negative p53. Conversely, the transforming growth factor-beta (TGF-beta) pathway has been found to be necessary for p21 induction. Prodigiosin-mediated p21 expression was blocked by SB431542, a TGF-beta receptor inhibitor. Nevertheless, this pathway alone is not enough to induce p21 expression. The TGF-beta family member (nonsteroidal anti-inflammatory drug)-activated gene 1/growth differentiation factor 15 (NAG-1) may activate this pathway, as it has previously been suggested to signal through the TGF-beta pathway and is overexpressed in response to prodigiosin treatment. We show that NAG-1 colocalizes with TGF-beta receptor type I, suggesting a possible interaction between them. Taken together, these results suggest the TGF-beta pathway is required for induction of p21 expression after prodigiosin treatment of MCF-7 cells.
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Affiliation(s)
- Vanessa Soto-Cerrato
- Department of Pathology and Experimental Therapeutics, Cancer Cell Biology Research Group, Universitat de Barcelona, and Laboratori de Recerca Translacional, ICO-IDIBELL, L'Hospitalet de Llobregat, Barcelona, Spain
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Wang Y, He QY, Chen H, Chiu JF. Synergistic effects of retinoic acid and tamoxifen on human breast cancer cells: Proteomic characterization. Exp Cell Res 2007; 313:357-68. [PMID: 17098229 DOI: 10.1016/j.yexcr.2006.10.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2006] [Revised: 10/12/2006] [Accepted: 10/19/2006] [Indexed: 11/29/2022]
Abstract
The anti-estrogen tamoxifen and vitamin A-related compound, all-trans retinoic acid (RA), in combination act synergistically to inhibit the growth of MCF-7 human breast cancer cells. In the present study, we applied two-dimensional gel electrophoresis based proteomic approach to globally analyze this synergistic effect of RA and tamoxifen. Proteomic study revealed that multiple clusters of proteins were involved in RA and tamoxifen-induced apoptosis in MCF-7 breast cancer cells, including post-transcriptional and splicing factors, proteins related to cellular proliferation or differentiation, and proteins related to energy production and internal degradation systems. The negative growth factor-transforming growth factor beta (TGFbeta) was secreted by RA and/or tamoxifen treatment and was studies as a potential mediator of the synergistic effects of RA and tamoxifen in apoptosis. By comparing protein alterations in treatments of RA and tamoxifen alone or in combination to those of TGFbeta treatment, or co-treatment with TGFbeta inhibitor SB 431542, proteomic results showed that a number of proteins were involved in TGFbeta signaling pathway. These results provide valuable insights into the mechanisms of RA and tamoxifen-induced TGFbeta signaling pathway in breast cancer cells.
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Affiliation(s)
- Ying Wang
- Department of Chemistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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Meyer E, Lamote I, Burvenich C. Retinoids and steroids in bovine mammary gland immunobiology. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.livprodsci.2005.10.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Danforth DN, Zhu Y. Conversion of Fas-resistant to Fas-sensitive MCF-7 Breast Cancer Cells by the Synergistic Interaction of Interferon-γ and all-TransRetinoic Acid. Breast Cancer Res Treat 2005; 94:81-91. [PMID: 16136269 DOI: 10.1007/s10549-005-7491-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The membrane receptor Fas (Apo-1/CD95) is an important initiator of programmed cell death induced by anti-Fas antibody or Fas ligand. MCF-7 human breast cancer cells have low levels of Fas receptor (FasR) and are resistant to anti-FasR antibody mediated apoptosis, however two naturally occurring substances, interferon and all-trans retinoic acid (AT), act synergistically to enhance antiproliferative processes in these cells, suggesting this combination may also be an effective means for enhancing FasR expression. When this was studied, it was found that IFN-gamma and AT in combination acted synergistically to induce expression of FasR mRNA and FasR protein in a time-dependent and dose-dependent manner. This induction required continuous protein synthesis, and STAT1 protein, but not PKR or TR1 protein, was induced in a manner quantitatively and temporally related to FasR protein induction, and consistent with STAT1 mediation of the synergistic effect of IFN-gamma and AT on FasR expression. FasR-induced cells were resistant to stimulation of apoptosis by anti-FasR antibody, however treatment with cycloheximide rendered these cells sensitive to antibody-induced apoptosis, suggesting endogenous blockade to signaling. These cells did not express caspase 3, or FLIP(L), but strongly expressed the endogenous inhibitor of apoptosis Bcl-2, indicating a type II Fas signaling pathway. Expression of these proteins was not modulated by IFN/AT, however treatment of Fas-induced cells with Bcl-2 specific small interfering RNA (SiRNA) downregulated Bcl-2 protein expression and rendered these cells sensitive to the cytotoxic effects of anti-Fas antibody. These findings indicate that IFN-gamma+AT in combination modulate Fas signaling and provide a novel mechanism for the promotion of cell death in breast cancer cells.
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Affiliation(s)
- David N Danforth
- Surgery Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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