RESUMEN
The epidermal growth factor receptor (EGFR) is a promising target for anticancer therapy because of its role in tumor growth, metastasis and angiogenesis, and tumor resistance to chemotherapy and radiotherapy. We have developed a low-molecular-weight EGFR tyrosine kinase inhibitor (EGFR-TKI), ZD1839 (Iressa(2) ). ZD1839, a substituted anilinoquinazoline, is a potent EGFR-TKI (IC(50) = 0.033 micro M) that selectively inhibits EGF-stimulated tumor cell growth (IC(50) = 0.054 micro M) and that blocks EGF-stimulated EGFR autophosphorylation in tumor cells. In studies with mice bearing a range of human tumor-derived xenografts, ZD1839 given p.o. once a day inhibited tumor growth in a dose-dependent manner. The level of expression of EGFR did not determine xenograft tumor sensitivity to ZD1839. Long-term ZD1839 (>3 months) treatment of mice bearing A431 xenografts was well tolerated, and ZD1839 completely inhibited tumor growth and induced regression of established tumors. No drug-resistant tumors appeared during ZD1839 treatment, but some tumors regrew after drug withdrawal. These studies indicate the potential utility of ZD1839 in the treatment of many human tumors and indicate that continuous once-a-day p.o. dosing might be a suitable therapeutic regimen.
Asunto(s)
Antineoplásicos/farmacología , Receptores ErbB/antagonistas & inhibidores , Quinazolinas/farmacología , Administración Oral , Animales , División Celular/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Receptores ErbB/metabolismo , Receptores ErbB/fisiología , Femenino , Gefitinib , Inhibidores de Crecimiento/farmacología , Humanos , Ratones , Ratones Desnudos , Fosforilación/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Clinical trials of selective small-molecule inhibitors of epidermal growth factor receptor tyrosine kinase activity have shown that these targeted inhibitors of proliferative signal transduction provide well-tolerated antitumour activity in patients. Preclinical pharmacology studies illustrate the potential use of these new cancer therapeutics in combination with chemotherapy, radiotherapy and hormone therapy, and in chemoprevention, in a spectrum of solid human tumours.
Asunto(s)
Inhibidores Enzimáticos/uso terapéutico , Receptores ErbB/antagonistas & inhibidores , Animales , Quimioterapia Combinada , Inhibidores Enzimáticos/química , Receptores ErbB/metabolismo , Gefitinib , Humanos , Neoplasias/tratamiento farmacológico , Neoplasias/enzimología , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Tirosina Quinasas/metabolismo , Quinazolinas/química , Quinazolinas/uso terapéuticoRESUMEN
The development of acquired resistance to antihormonal agents in breast cancer is a major therapeutic problem. We have developed a tamoxifen-resistant (TAM-R) MCF-7 breast cancer cell line to investigate the mechanisms behind this condition. Both epidermal growth factor receptor (EGFR) and c-erbB2 mRNA and protein expression were increased in TAM-R compared with wild-type MCF-7 cells, whereas comparable levels of c-erbB3 mRNA and protein were expressed in both cell lines. Under basal conditions, phosphorylated EGFR/c-erbB2, EGFR/c-erbB3 but not c-erbB2/c-erbB3 receptor heterodimers were detected in TAM-R cells in association with increased levels of phosphorylated extracellular-signal regulated kinase 1/2 (ERK1/2). Both cell lines were capable of generating a range of EGFR-specific ligands and increased expression of transforming growth factor alpha was observed in TAM-R cells. Treatment of TAM-R cells with ZD1839 (Iressa) or trastuzumab (Herceptin) blocked c-erbB receptor heterodimer formation and phosphorylation, reduced ERK1/2 activity, and strongly inhibited cell growth. The MAPK kinase inhibitor PD098059 specifically reduced phosphorylated ERK1/2 levels and inhibited TAM-R growth. All three agents abolished ERK1/2 activity in wild-type cells but caused only small reductions in cell proliferation. These results demonstrate that TAM-R MCF-7 cell growth is mediated by the autocrine release and action of an EGFR-specific ligand inducing preferential EGFR/c-erbB2 dimerization and downstream activation of the ERK pathway.
Asunto(s)
Neoplasias de la Mama/patología , Dimerización , Resistencia a Antineoplásicos , Receptores ErbB/análisis , Receptor ErbB-2/análisis , Tamoxifeno/uso terapéutico , Anticuerpos Monoclonales/farmacología , Anticuerpos Monoclonales Humanizados , Antineoplásicos/farmacología , Neoplasias de la Mama/química , Neoplasias de la Mama/tratamiento farmacológico , División Celular/efectos de los fármacos , Receptores ErbB/genética , Receptores ErbB/metabolismo , Flavonoides/farmacología , Gefitinib , Humanos , Proteína Quinasa 1 Activada por Mitógenos/análisis , Proteína Quinasa 1 Activada por Mitógenos/antagonistas & inhibidores , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos , Proteínas Quinasas Activadas por Mitógenos/análisis , Proteínas Quinasas Activadas por Mitógenos/antagonistas & inhibidores , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Fosforilación , Quinazolinas/farmacología , ARN Mensajero/análisis , Receptor ErbB-2/genética , Receptor ErbB-2/metabolismo , Factor de Crecimiento Transformador alfa/genética , Trastuzumab , Células Tumorales CultivadasRESUMEN
Despite an initial response to antihormonal therapies, the development of resistance will occur in a significant number of breast cancer patients. The mechanisms that underlie acquired resistance are not yet clear. Using a previously established in vitro cell model of tamoxifen resistance in MCF7 cells, shown to display autocrine epidermal growth factor receptor (EGFR) signalling, we assessed how resistance might modulate their metastatic phenotype in vitro, as metastatic disease is the single most important factor affecting the mortality of cancer patients. Furthermore, we investigated the effect of the EGFR tyrosine kinase inhibitor (EGFR-TKI), gefitinib ('Iressa', ZD1839; AstraZeneca), on this behaviour. The acquisition of tamoxifen resistance in MCF7 cells was accompanied by a dramatic and significant increase in their invasive and motile nature. The affinity of these cells for matrix components was also enhanced. Inhibition of EGFR signalling with gefitinib reduced both basal and TGF-alpha-stimulated invasion and motility and reduced cell-matrix adhesion. In conclusion, we demonstrate here that resistance to tamoxifen in breast cancer cells is accompanied by a significant increase in their basal motile and invasive activity, properties associated with increased metastatic potential. Inhibition of EGFR signalling by gefitinib significantly inhibited cell motility and invasion thus suggesting a role for the EGF receptor in the aggressive phenotype of tamoxifen-resistant breast cancer cells.
Asunto(s)
Antineoplásicos Hormonales/farmacología , Neoplasias de la Mama/patología , Resistencia a Antineoplásicos , Quinazolinas/farmacología , Tamoxifeno/farmacología , Adhesión Celular , Línea Celular Tumoral , Gefitinib , Humanos , Microscopía Fluorescente , Invasividad Neoplásica , FenotipoRESUMEN
From immunohistochemical and ligand-binding studies, it is known that the epidermal growth factor receptor (EGFR), a member of the erbB family of receptors, is expressed in tissues of epithelial, mesenchymal and neuronal origin and plays a major role in normal cellular processes such as proliferation, differentiation and development. EGFR is highly expressed in a number of solid tumours and its expression correlates with tumour progression, resistance to chemotherapy and a poor prognosis; it is consequently an attractive target for the rational design of novel anticancer agents. Knowledge of the role of EGFR in normal tissues will help the understanding of the adverse events associated with such agents. Studies in knockout mice and preclinical toxicology studies have shown that the major effects of inhibiting the EGFR are skin and gastrointestinal toxicities. Clinical studies with inhibitors of EGFR, such as gefitinib, cetuximab and erlotinib, have shown a favourable adverse-event profile, primarily consisting of skin and gastrointestinal toxicities, as predicted from the mechanism-based effects observed in preclinical studies.
Asunto(s)
Receptores ErbB/antagonistas & inhibidores , Receptores ErbB/fisiología , Animales , Antineoplásicos/farmacología , Inhibidores Enzimáticos/farmacología , Receptores ErbB/metabolismo , Gefitinib , Humanos , Ratones , Ratones Noqueados , Quinazolinas/farmacologíaRESUMEN
HER-2/neu in breast cancer is associated with tamoxifen resistance, but little data exist on its interaction with estrogen deprivation or fulvestrant. Here, we used an in vivo xenograft model of estrogen receptor (ER)-positive breast cancer with HER-2/neu overexpression (MCF7/HER-2/neu-18) to investigate mechanisms of growth inhibition and treatment resistance. MCF7/HER-2/neu-18 tumors were growth inhibited by estrogen deprivation and with fulvestrant, but resistance developed in 2 to 3 months. Inhibited tumors had reductions in ER, insulin-like growth factor-I receptor (IGF-IR), phosphorylated HER-2/neu (p-HER-2/neu), and phosphorylated p42/44 mitogen-activated protein kinase (p-MAPK). p27 was increased especially in tumors sensitive to estrogen deprivation. Tumors with acquired resistance to these therapies had complete loss of ER, increased p-HER-2/neu, increased p-MAPK, and reduced p27. In contrast, IGF-IR and phosphorylated AKT (p-AKT) levels were markedly reduced in these resistant tumors. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib, which can block EGFR/HER-2/neu signaling, significantly delayed the emergence of resistance to both estrogen deprivation and fulvestrant. Levels of p-MAPK and p-AKT decreased with gefitinib, whereas high ER levels were restored. Eventually, however, tumors progressed in mice treated with gefitinib combined with estrogen deprivation or fulvestrant accompanied again by loss of ER and IGF-IR, increased p-HER-2/neu, high p-MAPK, and now increased p-AKT. Thus, estrogen deprivation and fulvestrant can effectively inhibit HER-2/neu-overexpressing tumors but resistance develops quickly. EGFR/HER-2/neu inhibitors can delay resistance, but reactivation of HER-2/neu and signaling through AKT leads to tumor regrowth. Combining endocrine therapy with EGFR/HER-2/neu inhibitors should be tested in clinical breast cancer, but a more complete blockade of EGFR/HER-2/neu may be optimal.
Asunto(s)
Neoplasias de la Mama/patología , Estrógenos/fisiología , Receptor ErbB-2/antagonistas & inhibidores , Receptores de Estrógenos/análisis , Animales , Línea Celular Tumoral , Receptores ErbB/antagonistas & inhibidores , Estrógenos/deficiencia , Femenino , Humanos , Inmunohistoquímica , Ratones , Ratones Desnudos , Trasplante HeterólogoRESUMEN
Despite recent advances in the treatment of breast cancer, survival rates for patients with metastatic breast cancer remain poor, and new treatments are still required for both hormone-dependent and hormone-independent disease. The epidermal growth factor receptor (EGFR) is a promising new target for anticancer therapy because it is commonly highly expressed in breast cancer and is implicated in the control of many aspects of tumor biology. Because expression of EGFR is inversely related to expression of the estrogen receptor (ER) and is associated with resistance to currently available breast cancer therapies, EGFR-targeted therapies may be valuable in the treatment of ER-negative tumors and endocrine-resistant, ER-positive tumors. Furthermore, the novel mechanism of action of EGFR-targeted therapies may complement the antitumor activity of existing treatment with cytotoxic agents, radiotherapy, or hormones. In this article, the small-molecule inhibitors of the tyrosine kinase activity of EGFR are discussed, with particular emphasis on the potential use of such agents at each stage of breast cancer, including a potential role in chemoprevention.
Asunto(s)
Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/fisiopatología , Inhibidores Enzimáticos/farmacología , Receptores ErbB/efectos de los fármacos , Receptores ErbB/fisiología , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Tirosina Quinasas/farmacología , Antineoplásicos Hormonales/farmacología , Quimioprevención , Resistencia a Antineoplásicos , Femenino , Humanos , PronósticoRESUMEN
The tamoxifen-resistant (TAM-R) MCF-7 breast cancer cell line has been used as a model to identify the signalling pathways that enable resistant cancer cells to grow independently of steroid hormones. In TAM-R cells, peptide growth factor signalling pathways appear to be important in modified cell behaviour, growth and survival. The PI3 kinase signalling components Akt1 and Akt2 are expressed at similar levels by both parental wild-type MCF-7 and TAM-R cells, but Akt1 phosphorylation is significantly increased in TAM-R cells grown under basal conditions. High levels of basal Akt, GSK3 alpha / beta and p70S6 kinase phosphorylation are all inhibited by the PI3 kinase inhibitor, LY 294002. The ligands for the EGFR/erbB1 receptor, EGF (epidermal growth factor) and TGF alpha (transforming growth factor- alpha ) demonstrate an increased ability to activate Akt in TAM-R compared with parental MCF-7 cells and it is proposed that the preferred autocrine or paracrine activation of Akt occurs via the erbB heterodimer EGFR/erbB2 in TAM-R cells. Akt phosphorylation is reduced by gefitinib ("Iressa"/ZD1839). The results suggest that the PI3 kinase pathway plays a role in proliferation of TAM-R cells and is important in the increased EGF induced membrane ruffling detected in the resistant cells. Increased Akt1 activation may contribute to the aggressive phenotype of tamoxifen resistant ER (oestrogen receptor) positive breast cancers.
Asunto(s)
Antineoplásicos Hormonales/farmacología , Neoplasias de la Mama/patología , Factor de Crecimiento Epidérmico/biosíntesis , Proteínas Serina-Treonina Quinasas/farmacología , Proteínas Proto-Oncogénicas/farmacología , Tamoxifeno/farmacología , Resistencia a Antineoplásicos , Femenino , Humanos , Fenotipo , Fosforilación , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Tirosina Quinasas , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-akt , Receptores de Estrógenos/análisis , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal , Células Tumorales CultivadasRESUMEN
BACKGROUND: Patients receiving adjuvant tamoxifen whose tumors express high levels of both HER2/neu (HER2) and the estrogen receptor (ER) coactivator AIB1 often develop tamoxifen resistance. We used a breast cancer model system with high expression of AIB1 and HER2 to investigate the possible mechanisms underlying this resistance. METHODS: MCF-7 breast cancer cells, which express high levels of AIB1, and a tamoxifen-resistant derivative cell line engineered to overexpress HER2 (MCF-7/HER2-18) were treated with estrogen, tamoxifen, epidermal growth factor (EGF), or heregulin in the absence or presence of the EGF receptor (EGFR) tyrosine kinase inhibitor gefitinib. We analyzed phosphorylation of signaling intermediates by immunoblotting, ER transcriptional activity with reporter gene constructs and immunoblot analysis of endogenous gene products, promoter assembly by chromatin immunoprecipitation (ChIP) assay, and tumor cell growth in vitro by anchorage-independent colony formation and in vivo using xenografts in nude mice. RESULTS: MCF-7/HER2-18 tumors were completely growth inhibited by estrogen deprivation but were growth stimulated by tamoxifen. Molecular cross-talk between the ER and HER2 pathways was increased in the MCF-7/HER-2 cells compared with MCF-7 cells, with cross-phosphorylation and activation of both the ER and the EGFR/HER2 receptors, the signaling molecules AKT and ERK 1,2 mitogen-activated protein kinase (MAPK), and AIB1 itself with both estrogen and tamoxifen treatment. Tamoxifen recruited coactivator complexes (ER, AIB1, CBP, p300) to the ER-regulated pS2 gene promoter in MCF-7/HER2-18 cells and corepressor complexes (NCoR, histone deacetylase 3) in MCF-7 cells. Gefitinib pretreatment blocked receptor cross-talk, reestablished corepressor complexes with tamoxifen-bound ER on target gene promoters, eliminated tamoxifen's agonist effects, and restored its antitumor activity both in vitro and in vivo in MCF-7/HER2-18 cells. CONCLUSIONS: Tamoxifen behaves as an estrogen agonist in breast cancer cells that express high levels of AIB1 and HER2, resulting in de novo resistance. Gefitinib's ability to eliminate this cross-talk and to restore tamoxifen's antitumor effects should be tested in the clinic.
Asunto(s)
Antineoplásicos Hormonales/farmacología , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/metabolismo , Resistencia a Antineoplásicos , Moduladores de los Receptores de Estrógeno/farmacología , Receptor ErbB-2/metabolismo , Receptores de Estrógenos/metabolismo , Tamoxifeno/farmacología , Animales , Línea Celular Tumoral , Quimioterapia Adyuvante , Inhibidores Enzimáticos/farmacología , Factor de Crecimiento Epidérmico/antagonistas & inhibidores , Femenino , Gefitinib , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Fosforilación/efectos de los fármacos , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Quinazolinas/farmacología , Receptor Cross-Talk/efectos de los fármacos , Receptor ErbB-2/efectos de los fármacos , Receptores de Estrógenos/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Trasplante Heterólogo , Regulación hacia Arriba/efectos de los fármacosRESUMEN
Oestrogen receptor (ER) levels are usually maintained on acquisition of tamoxifen resistance in the clinic, however, tumour re-growth is associated with increased expression of epidermal growth factor receptor (EGFR) and activation of the mitogen activated protein kinase (MAPK) pathway. In the present study we have used the ER down-regulator fulvestrant ('Faslodex') to investigate the influence of the ER on growth of a tamoxifen-resistant (TAM-R) human breast cancer cell line. Expression levels of ER mRNA and protein were equivalent in parental wild-type MCF-7 (WT) and TAM-R cells. Fulvestrant eliminated ER protein expression and inhibited proliferation in both cell lines. The growth inhibitory effects of fulvestrant were associated with a decrease in basal EGFR, c-erbB2 and ERK1/2 activity in TAM-R but not WT cells. ER functionality as determined by oestrogen response element (ERE)-luciferase reporter activity and expression of PgR, pS2 and transforming growth factor alpha (TGFalpha) was significantly reduced in TAM-R compared to WT cells and was further decreased by fulvestrant treatment in both cell lines. Epidermal growth factor (EGF) and TGFalpha significantly increased EGFR/MAPK pathway activity in both cell lines. Ligand-induced EGFR/MAPK activation promoted TAM-R cell growth in both the absence and presence of fulvestrant, whereas no proliferative activity was observed under the same conditions in WT cells. These results suggest that the ER modulates EGFR/MAPK signalling efficiency in TAM-R cells possibly through the regulation of TGFalpha availability. This effect may be overcome by the action of exogenous EGFR ligands, which strengthen EGFR/MAPK signalling activity to generate endocrine-insensitive cell growth.
Asunto(s)
Neoplasias de la Mama/patología , Resistencia a Antineoplásicos , Receptores ErbB/metabolismo , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Receptor ErbB-2/metabolismo , Receptores de Estrógenos/metabolismo , Antineoplásicos Hormonales/farmacología , Neoplasias de la Mama/química , Neoplasias de la Mama/tratamiento farmacológico , División Celular/efectos de los fármacos , Línea Celular Tumoral , Receptores ErbB/análisis , Receptores ErbB/genética , Moduladores de los Receptores de Estrógeno/farmacología , Femenino , Humanos , Inmunohistoquímica , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteínas Quinasas Activadas por Mitógenos/análisis , Proteínas Quinasas Activadas por Mitógenos/antagonistas & inhibidores , ARN Mensajero/análisis , Receptor ErbB-2/análisis , Receptor ErbB-2/genética , Receptores de Estrógenos/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Tamoxifeno/farmacologíaRESUMEN
Novel cancer chemotherapeutics are required to induce apoptosis by activating pro-apoptotic proteins. Both epidermal growth factor (EGF) and insulin-like growth factor (IGF) provide potent survival stimuli in many epithelia, and activation of their receptors is commonly observed in solid human tumors. Here we demonstrate that blockade of the EGF receptor by a new drug in phase III clinical trails for cancer, ZD1839, potently induces apoptosis in mammary epithelial cell lines and primary cultures, as well as in a primary pleural effusion from a breast cancer patient. We identified the mechanism of apoptosis induction by ZD1839. We showed that it prevents cell survival by activating the pro-apoptotic protein BAD. Moreover, we demonstrate that IGF transactivates the EGF receptor and that ZD1839 blocks IGF-mediated phosphorylation of MAPK and BAD. Many cancer therapies kill tumor cells by inducing apoptosis as a consequence of targeting DNA; however, the threshold at which apoptosis can be triggered through DNA damage is often different from that in normal cells. Our results indicate that by targeting a growth factor-mediated survival signaling pathway, BAD phosphorylation can be manipulated therapeutically to induce apoptosis.
Asunto(s)
Apoptosis/efectos de los fármacos , Proteínas Portadoras/metabolismo , Receptores ErbB/antagonistas & inhibidores , Glándulas Mamarias Animales/fisiología , Quinazolinas/farmacología , Receptores de Somatomedina/metabolismo , Animales , Antineoplásicos/farmacología , Proteínas Portadoras/genética , Muerte Celular , Línea Celular , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Factor de Crecimiento Epidérmico/farmacología , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Células Epiteliales/fisiología , Femenino , Gefitinib , Factor I del Crecimiento Similar a la Insulina/metabolismo , Sistema de Señalización de MAP Quinasas/fisiología , Glándulas Mamarias Animales/citología , Glándulas Mamarias Animales/efectos de los fármacos , Ratones , Ratones Endogámicos ICR , Ratones Noqueados , Fosfatidilinositol 3-Quinasas/metabolismo , Embarazo , Transducción de Señal , Activación Transcripcional , Proteína Letal Asociada a bclRESUMEN
BACKGROUND: Epidermal growth factor receptor (EGF-R) autophosphorylation is essential for its intracellular mitogenic signaling via the MAPK pathway and for interaction in other cellular processes. Inhibition of this activity in tumor cells that predominantly utilise EGF-R therefore offers an alternative approach to therapy. METHODS: The ability of a specific inhibitor of EGF-R tyrosine kinase, ZM 252868, (TKI) to alter various parameters related to growth in DU145 and PC3 cell lines was investigated, by immunocytochemistry, Northern blotting, Western blotting and invasion assays. RESULTS: In DU145 cultures, the total cell population and number of cells in cell cycle decreased in the presence of TKI whilst the apoptotic rate was significantly increased. Reduction in autophosphorylation of the EGF-R, membrane expression of EGF-R, activation of the MAPK, p38, and JNK enzymes and the invasive capacity of DU145 cells was observed in the TKI treated cells. Under the same conditions, PC3 cell growth and EGF-R expression and MAPK activation were not affected. The use of inhibitors of intracellular signaling indicated that the DU145 cells, in contrast to PC3 cells, predominantly utilize EGF-R activation of the MAPK signaling pathway for growth. CONCLUSIONS: In prostatic cancer patients, in whom androgen resistance has developed and whose tumors have upregulated EGF-R for growth, specific TKI's may offer an important therapy option.
Asunto(s)
Adenocarcinoma/patología , Inhibidores Enzimáticos/farmacología , Receptores ErbB/fisiología , Neoplasias de la Próstata/patología , Apoptosis , Northern Blotting , Western Blotting , Recuento de Células , Ciclo Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Activación Enzimática , Factor de Crecimiento Epidérmico/farmacología , Receptores ErbB/antagonistas & inhibidores , Receptores ErbB/genética , Humanos , Inmunohistoquímica , Masculino , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Invasividad Neoplásica , Fosforilación , Quinazolinas/farmacología , ARN Mensajero/análisis , Transducción de Señal , Factor de Crecimiento Transformador alfa/farmacología , Células Tumorales CultivadasRESUMEN
BACKGROUND: Although antiestrogens have been effective in preventing estrogen receptor (ER)-positive breast cancer, chemopreventive agents are still needed to prevent ER-negative breast cancer. Tyrosine kinase inhibitors are promising agents for the treatment and prevention of human cancers. ZD1839 (gefitinib or Iressa) is an orally active epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that blocks signal transduction pathways in epithelial cells. We examined whether ZD1839 blocks signal transduction and prevents the development of ER-negative breast cancer. METHODS: The ability of ZD1839 to block signal transduction in normal, immortalized, and malignant breast cells was assessed by western blotting with specific antibodies to detect phosphorylation of cytoplasmic signaling molecules. The effect of ZD1839 on growth of these breast cells was assessed with anchorage-dependent and anchorage-independent growth assays. Its effect on ER-negative mammary tumorigenesis was assessed in MMTV-erbB2 transgenic mice. All statistical tests were two-sided. RESULTS: ZD1839 suppressed the phosphorylation of EGFR and mitogen-activated protein kinase in normal and malignant breast cells. ZD1839 treatment statistically significantly suppressed mammary tumorigenesis in MMTV-erbB2 transgenic mice; median time to tumor development was approximately 230 days in vehicle-treated mice and more than 310 days in mice treated with ZD1839 at 100 mg/kg (P<.001). ZD1839 reduced proliferation of normal breast cells by 20.3% (95% confidence interval [CI] = -13.7% to 44.2%) and of tumor cells by 42.0% (95% CI = 20.2% to 58.2%). ZD1839 also increased expression of the cell cycle regulator p27 in normal mammary tissue by 48.7% (95% CI = 27.0% to 74.2%) and in tumor tissue by 50.3% (95% CI = 35.8% to 66.7%). CONCLUSION: This study appears to provide the preclinical rationale for the development of these EGFR tyrosine kinase inhibitors for the prevention of human breast cancer.