Endothelin-1 protects ovarian carcinoma cells against paclitaxel-induced apoptosis: requirement for Akt activation.
Endothelin-1 (ET-1) is a powerful mitogenic peptide produced by different tumors. In ovarian carcinoma cells, ET-1 acts as an autocrine growth factor, selectively through ET(A) receptor (ET(A)R), which is predominantly expressed in tumor cells. The aim of this study was to examine whether ET-1 plays a role in the sensitivity of three ovarian carcinoma cell lines (OVCA 433, HEY, and SK-OV-3) to apoptosis induced by two different stimuli. Our results demonstrated that the addition of ET-1 markedly inhibited serum withdrawal and paclitaxel-induced apoptosis in a concentration-dependent manner, as demonstrated by Annexin-V assay, sub-G(1) peak in DNA content histograms, internucleosomal DNA fragmentation, and terminal deoxynucleotidyl transferase-mediated dUTP biotin nick-end labeling method. Pretreatment of the cells with an ET(A)R antagonist, BQ 123, reversed the ET-1-induced protective effect. Paclitaxel-induced apoptosis resulted in the phosphorylation of Bcl-2 that was suppressed by the addition of ET-1. Further analysis of the signaling pathway demonstrated that ET-1 stimulated Akt activation. The phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin blocked ET-1-induced Akt phosphorylation. Inhibition of ET-1-stimulated mitogen-activated protein kinase activity did not affect ET-1 protection from paclitaxel-mediated apoptosis. Moreover, BQ 123 blocked the Akt-mediated pathway activated by ET-1, sensitizing ovarian carcinoma cells to paclitaxel treatment. These results establish a novel role for ET-1 in determining protection of ovarian carcinoma cells against paclitaxel-induced apoptosis through Bcl-2-dependent and PI3-K-mediated Akt pathways and suggest that ET-1 and ET(A)R could represent important targets for anticancer therapy.
Del Bufalo
Donatella
D
Experimental Chemotherapy Laboratories, Regina Elena Cancer Institute, Rome, Italy.
Di Castro
Valeriana
V
Biroccio
Annamaria
A
Varmi
Marco
M
Salani
Debora
D
Rosanò
Laura
L
Trisciuoglio
Daniela
D
Spinella
Francesca
F
Bagnato
Anna
A
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis; D016895:Culture Media, Serum-Free; D004347:Drug Interactions; D019332:Endothelin-1 / Q000494:pharmacology*; D005260:Female; D006801:Humans; D010051:Ovarian Neoplasms; D017239:Paclitaxel / Q000494:pharmacology*; D010766:Phosphorylation; D020011:Protective Agents / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000502:physiology; D014407:Tumor Cells, Cultured
D000972:Antineoplastic Agents, Phytogenic; D016895:Culture Media, Serum-Free; D019332:Endothelin-1; D020011:Protective Agents; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017239:Paclitaxel