RESUMEN
BACKGROUND: The Arp2/3 complex is required for cell migration and invasion. The Arp2/3 complex and its activators, such as the WAVE complex, are deregulated in diverse cancers. Here we investigate the expression of Arpin, the Arp2/3 inhibitory protein that antagonises the WAVE complex. METHODS: We used qRT-PCR and reverse phase protein arrays in a patient cohort with known clinical parameters and outcome, immunofluorescence in breast biopsy cryosections and breast cancer cell lines. RESULTS: Arpin was downregulated at the mRNA and protein levels in mammary carcinoma cells. Arpin mRNA downregulation was associated with poor metastasis-free survival (MFS) on univariate analysis (P=0.022). High expression of the NCKAP1 gene that encodes a WAVE complex subunit was also associated with poor MFS on univariate analysis (P=0.0037) and was mutually exclusive with Arpin low. Arpin low or NCKAP1 high was an independent prognosis factor on multivariate analysis (P=0.0012) and was strongly associated with poor MFS (P=0.000064). CONCLUSIONS: Loss of the Arp2/3 inhibitory protein Arpin produces a similar poor outcome in breast cancer as high expression of the NCKAP1 subunit of the Arp2/3 activatory WAVE complex.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/genética , Neoplasias de la Mama/genética , Carcinoma/genética , Proteínas Portadoras/genética , Regulación hacia Abajo , ARN Mensajero/metabolismo , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Adenoma/genética , Adenoma/metabolismo , Western Blotting , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Carcinoma/metabolismo , Carcinoma/patología , Proteínas Portadoras/metabolismo , Línea Celular Tumoral , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/metabolismo , Supervivencia sin Enfermedad , Receptor alfa de Estrógeno/metabolismo , Femenino , Técnica del Anticuerpo Fluorescente , Humanos , Persona de Mediana Edad , Metástasis de la Neoplasia , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Pronóstico , Análisis por Matrices de Proteínas , Receptor ErbB-2/metabolismo , Receptores de Progesterona/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Carga TumoralRESUMEN
Cell migration requires the generation of branched actin networks that power the protrusion of the plasma membrane in lamellipodia. The actin-related proteins 2 and 3 (Arp2/3) complex is the molecular machine that nucleates these branched actin networks. This machine is activated at the leading edge of migrating cells by Wiskott-Aldrich syndrome protein (WASP)-family verprolin-homologous protein (WAVE, also known as SCAR). The WAVE complex is itself directly activated by the small GTPase Rac, which induces lamellipodia. However, how cells regulate the directionality of migration is poorly understood. Here we identify a new protein, Arpin, that inhibits the Arp2/3 complex in vitro, and show that Rac signalling recruits and activates Arpin at the lamellipodial tip, like WAVE. Consistently, after depletion of the inhibitory Arpin, lamellipodia protrude faster and cells migrate faster. A major role of this inhibitory circuit, however, is to control directional persistence of migration. Indeed, Arpin depletion in both mammalian cells and Dictyostelium discoideum amoeba resulted in straighter trajectories, whereas Arpin microinjection in fish keratocytes, one of the most persistent systems of cell migration, induced these cells to turn. The coexistence of the Rac-Arpin-Arp2/3 inhibitory circuit with the Rac-WAVE-Arp2/3 activatory circuit can account for this conserved role of Arpin in steering cell migration.
