Regulación del receptor ErbB2 y su relación con la diferenciación neuroendocrina en el cáncer de próstata
- Autores: María A. Cortés
- Directores de la Tesis: Begoña Colás Escudero (dir. tes.), Pilar López Ruíz (codir. tes.)
- Lectura: En la Universidad de Alcalá ( España ) en 2010
- Idioma: español
- Tribunal Calificador de la Tesis: María José Carmena Sierra (presid.), Lilian Puebla Jiménez (secret.), José Mario Mellado García (voc.), Francisco Javier Rodríguez Ubreva (voc.), Marina Lasa Benito (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: e_Buah
- Resumen
- español
Nuestro grupo previamente había demostrado que el EGF impide la diferenciación NE de las células de cáncer de próstata LNCaP, provocada por la eliminación de andrógenos. Este efecto del EGF estaría modulado por la actividad de la vía PI3K/Akt. La activación constitutiva de esta vía de señalización, por falta de PTEN, permite que el EGF estimule la proliferación de las células LNCaP, bloqueando el proceso de diferenciación NE. Por el contrario, en presencia de inhibidores de esta vía como LY294002, el EGF induce supervivencia celular, permitiendo la diferenciación NE. Por lo tanto, era necesario comprender los mecanismos moleculares responsables de este cambio en los efectos del EGF, al inhibir la vía de la PI3K/Akt, ya que en estas condiciones, las células tumorales sobreviven y adquieren el fenotipo NE, dos procesos de enorme trascendencia para la progresión tumoral prostática.Nuestros resultados demuestran, por primera vez, que el tratamiento conjunto de las células LNCaP con EGF y LY29 provoca un aumento de los niveles de ErbB2. Este receptor es responsable de la adquisición del fenotipo NE pero no de la supervivencia celular en estas condiciones. Este aumento de ErbB2 sería el resultado no solo de un aumento en su síntesis sino también de su permanencia en la membrana celular. Sorprendentemente, este aumento de ErbB2 es independiente de la vía PI3K/Akt y es el resultado de los efectos del LY29 en presencia de EGF sobre: Hsp90, Erk1/2 y/o probablemente NFkB.
- English
Prostate cancer is one of the most common malignancies among men in Europe. Because the tumor is initially androgen-dependent in the majority of cases, endocrine manipulation is the first-line therapy for metastatic and locally advanced cancers and often leads to remission or stabilization of the disease. This period of remission, however, is invariably followed by tumor relapse, and available treatment options are only palliative. Patients with metastatic prostate cancer develop an androgenrefractory phenotype that leads to disease progression and eventual death. Therefore, an understanding of what drives progression to androgen independence is critical. In fact, the prostate is known to be dependent not exclusively on androgens but also on growth factors and neuropeptides secreted by neuroendocrine (NE) cells that maintain normal prostate function and play a role in the development of pathological conditions. Long-term androgen ablation therapy tends to select prostate tumor populations that are enriched in NE cells. Those tumors with an increased NE cell population are often more aggressive and have a poorer prognosis. Therefore, it has been hypothesized that NE cells can lead to the development and growth of androgen-refractory prostate tumors through the secretion of neuropeptides that induce the proliferation of adjacent carcinoma cells in an androgen-depleted condition. Hence, our objective was to study the molecular mechanisms of NE differentiation in LNCaP cells. We present evidence that EGF prevents NE differentiation in LNCaP cells induced by androgen depletion. In these cells, the constitutive activation of Akt supports this effect of EGF because abrogation of PI3K/Akt signalling with LY294002 (LY29) alters the EGF-induced NE differentiation-inhibitory response toward cell survival and NE cell differentiation. The primary focus of this investigation was to study the molecular mechanisms involved in the treatment of LNCaP cells with EGF and LY29 as well as the relationship to NE cell differentiation and cell survival since both have been implicated in the progression of prostate cancer. Our group has shown, by western blotting, that treatment with EGF+LY29 increases ErbB2 levels. We have also shown an increase of ErbB2/EGFR heterodimer formation, receptor phosphorylation, ErbB2 plasma membrane localization and active signalling of the MAPK-Erk1/2 pathway. We found that EGF+LY29 did not modify EGFR levels, suggesting the existence of ErbB2/EGFR heterodimers that maintain EGFR levels. Furthermore, we found the levels of ErbB2 to be dependent on EGFR phosphorylation. In fact, incubation of cells LNCaP with ZD1839 prior to EGF+LY29 treatment markedly inhibited EGFR phosphorylation and reduced ErbB2 levels. ErbB2 is responsible for NE differentiation but not cell survival under our experimental conditions. This is consistent with results showing that the down-regulation of the ErbB2 gene by small interfering RNA suppressed EGF+LY29-induced NE differentiation in LNCaP cells. Furthermore, we found that the treatment of these cells with IL-6 and forskoline increased ErbB2 protein levels.
ErbB2 over-expression is due to increased protein synthesis and cell surface localization. Quantitative real-time (qPCR) and semi-quantitative RT-PCR showed increased levels of ErbB2 mRNA in LNCaP cells induced by EGF+LY29 treatment. Immunofluorescence and flow cytometric analysis showed increased localization of ErbB2 on the cell surface. Surprisingly, the above-mentioned increase of ErbB2 is PI3Kindependent. Our results indicate that the treatment with EGF and LY29 upregulates ErbB2 via mechanisms involving Hsp90, ErK1/2 and probably NFkB.
- español
