RESUMO
BACKGROUND: The role of estrogen and estrogen receptors in oncogenesis has been investigated in various malignancies. Recently our group identified estrogen receptor beta (ERß) expression as an independent prognostic factor in the progression of human Malignant Pleural Mesothelioma (MMe), but the underlying mechanism by which ERß expression in tumors determines clinical outcome remains largely unknown. This study is aimed at investigating the molecular mechanisms of ERß action in MMe cells and disclosing the potential translational implications of these results. METHODS: We modulated ERß expression in REN and MSTO-211H MMe cell lines and evaluated cell proliferation and EGF receptor (EGFR) activation. RESULTS: Our data indicate that ERß knockdown in ER positive cells confers a more invasive phenotype, increases anchorage independent proliferation and elevates the constitutive activation of EGFR-coupled signal transduction pathways. Conversely, re-expression of ERß in ER negative cells confers a more epithelioid phenotype, decreases their capacity for anchorage independent growth and down-modulates proliferative signal transduction pathways. We identify a physical interaction between ERß, EGFR and caveolin 1 that results in an altered internalization and in a selective reduced activation of EGFR-coupled signaling, when ERß is over-expressed. We also demonstrate that differential expression of ERß influences MMe tumor cell responsiveness to the therapeutic agent: Gefitinib. CONCLUSIONS: This study describes a role for ERß in the modulation of cell proliferation and EGFR activation and provides a rationale to facilitate the targeting of a subgroup of MMe patients who would benefit most from therapy with Gefitinib alone or in combination with Akt inhibitors.
Assuntos
Receptores ErbB/antagonistas & inibidores , Receptor beta de Estrogênio/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Quinazolinas/farmacologia , Western Blotting , Caveolina 1/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Fator de Crescimento Epidérmico/farmacologia , Receptores ErbB/metabolismo , Receptor beta de Estrogênio/genética , Gefitinibe , Humanos , Imunoprecipitação , Mesotelioma/genética , Mesotelioma/metabolismo , Mesotelioma/patologia , Microscopia Confocal , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Fosforilação/efeitos dos fármacos , Neoplasias Pleurais/genética , Neoplasias Pleurais/metabolismo , Neoplasias Pleurais/patologia , Ligação Proteica , Proteínas Proto-Oncogênicas c-akt/metabolismo , Interferência de RNARESUMO
The activity of 8-prenylapigenin (8-PA) and its 3'-methoxylated analogue isocannflavin B (IsoB) was investigated in estrogen-dependent T47-D and estrogen-independent MDA-MB-231 human breast cancer cell lines. 8-PA showed a biphasic effect on T47-D cell proliferation, while no significant effect was observed on MDA-MB-231 cells. Conversely, IsoB exhibited only an inhibitory effect on T47-D cell proliferation, accompanied by the appearance of an intense intracytoplasmic vacuolization of autophagic origin. Moreover, biochemical analysis showed that IsoB reduced Akt phosphorylation and p21(Cip1) expression in T47-D cells. These data show that the prenylflavone moiety is a versatile platform for the induction and modulation of bioactivity.