RESUMEN
The Id family of helix-loop-helix (HLH) proteins are thought to affect the balance between cell growth and differentiation by negatively regulating the function of basic-helix-loop-helix (bHLH) transcription factors. Although it has been suggested for some time that Id is involved in cell cycle regulation, little is known about the molecular mechanism of this control. Recent studies, however, have revealed that Id binds to important cell cycle regulatory proteins other than bHLH proteins. Two such proteins, pRB (retinoblastoma tumour suppressor protein) family proteins and Ets-family transcription factors are known to play key roles in cell cycle regulation, transformation and tumour suppression. Through the characterization of these pathways we will begin to understand the mechanisms by which Id controls normal and abnormal cell cycle progression.
Asunto(s)
Ciclo Celular/fisiología , Senescencia Celular/fisiología , Proteínas de Unión al ADN/fisiología , Familia de Multigenes , Proteínas de Neoplasias , Proteínas Represoras , Factores de Transcripción/fisiología , Animales , Ciclo Celular/genética , Proteínas de Ciclo Celular/fisiología , División Celular , Transformación Celular Neoplásica/genética , Senescencia Celular/genética , Inhibidor p16 de la Quinasa Dependiente de Ciclina/fisiología , Replicación del ADN , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Dimerización , Fibroblastos/citología , Regulación del Desarrollo de la Expresión Génica , Genes Supresores de Tumor , Genes p16 , Genes ras , Secuencias Hélice-Asa-Hélice , Humanos , Proteína 1 Inhibidora de la Diferenciación , Proteína 2 Inhibidora de la Diferenciación , Proteínas Inhibidoras de la Diferenciación , Sistema de Señalización de MAP Quinasas , Mamíferos/genética , Mamíferos/fisiología , Ratones , Modelos Biológicos , Proteína de Retinoblastoma/fisiología , Factores de Transcripción/química , Factores de Transcripción/genética , Transcripción GenéticaRESUMEN
AIM: It has long been suggested that malignant cells may be shed into the blood stream during any given surgical procedure for cancer. A number of studies have now reported the detection of occult melanoma cells in peripheral blood using a reverse transcriptase polymerase chain reaction (RT-PCR) based assay. The principal aim of these studies has been to determine a prognostic value for the test and not to evaluate the influence of intervention upon results. METHODS: In this pilot study we aimed to determine whether the assay could be used as a model to detect cells that are seeded during surgery. Peripheral blood samples were obtained pre- and post-operatively on twenty patients undergoing surgery for malignant melanoma - ten with primary disease and ten undergoing regional lymphadenectomy. A further ten patients undergoing surgery for non-melanoma conditions provided controls. RESULTS: Using RT-PCR, it was possible to identify tyrosinase transcripts in the peripheral blood of one of ten patients undergoing excision of local disease and four of ten undergoing surgery for regional metastatic disease. CONCLUSION: It was concluded that this technique does enable detection of a greater percentage of RT-PCR findings post-operatively. This in turn may provide a means for optimizing or comparing surgical techniques and provides a potential guide in the use of adjuvant therapies.
Asunto(s)
Melanoma/sangre , Melanoma/cirugía , Siembra Neoplásica , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Neoplasias Cutáneas/sangre , Neoplasias Cutáneas/cirugía , Secuencia de Bases , Estudios de Casos y Controles , Femenino , Humanos , Masculino , Melanoma/patología , Melanoma/secundario , Datos de Secuencia Molecular , Invasividad Neoplásica , Células Neoplásicas Circulantes/patología , Proyectos Piloto , Periodo Posoperatorio , Pronóstico , Valores de Referencia , Medición de Riesgo , Sensibilidad y Especificidad , Neoplasias Cutáneas/patología , Procedimientos Quirúrgicos Operativos/efectos adversos , Procedimientos Quirúrgicos Operativos/métodosRESUMEN
A number of authors have reported the detection of tyrosinase mRNA in the peripheral blood of patients with malignant melanoma using the reverse transcription polymerase chain reaction (RT-PCR). The precise value of this assay as a prognostic tool, however, remains in doubt. This is particularly so with relation to localised disease, where relatively little data has been accumulated. In this study we analysed the peripheral blood of 50 consecutive patients with primary malignant melanoma referred to a plastic surgical centre with the facility of a pigmented lesion clinic. Samples were analysed from an additional 35 patients with advanced melanoma disease and 35 patients with benign pigmented cutaneous lesions. We were able to identify tyrosinase transcripts in the peripheral blood of only two of 50 patients with localised disease. Of those with more advanced disease, a positive finding was found in three with regional disease and four patients with metastatic spread. Stage of disease was found to correlate significantly with PCR status. No correlation was identified with other prognostic markers or with outcome over a three-year period. This data would support the conclusion that the detection of tyrosinase mRNA in peripheral blood is likely to be of little value as an aid in the management of patients with early malignant melanoma.
Asunto(s)
Biomarcadores de Tumor/sangre , Melanoma/enzimología , Monofenol Monooxigenasa/sangre , Neoplasias Cutáneas/enzimología , Humanos , Melanoma/patología , Monofenol Monooxigenasa/genética , Estadificación de Neoplasias , Pronóstico , ARN Mensajero/sangre , ARN Neoplásico/sangre , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Neoplasias Cutáneas/patología , Estadística como AsuntoRESUMEN
The p16INK4a cyclin-dependent kinase inhibitor is implicated in replicative senescence, the state of permanent growth arrest provoked by cumulative cell divisions or as a response to constitutive Ras-Raf-MEK signalling in somatic cells. Some contribution to senescence presumably underlies the importance of p16INK4a as a tumour suppressor but the mechanisms regulating its expression in these different contexts remain unknown. Here we demonstrate a role for the Ets1 and Ets2 transcription factors based on their ability to activate the p16INK4a promoter through an ETS-binding site and their patterns of expression during the lifespan of human diploid fibroblasts. The induction of p16INK4a by Ets2, which is abundant in young human diploid fibroblasts, is potentiated by signalling through the Ras-Raf-MEK kinase cascade and inhibited by a direct interaction with the helix-loop-helix protein Id1 (ref. 11). In senescent cells, where the Ets2 levels and MEK signalling decline, the marked increase in p16INK4a expression is consistent with the reciprocal reduction of Id1 and accumulation of Ets1.