RESUMEN
PURPOSE: Aberrant DNA methylation, now recognized as a contributing factor to neoplasia, often shows definitive gene/sequence preferences unique to specific cancer types. Correspondingly, distinct combinations of methylated loci can function as biomarkers for numerous clinical correlates of ovarian and other cancers. EXPERIMENTAL DESIGN: We used a microarray approach to identify methylated loci prognostic for reduced progression-free survival (PFS) in advanced ovarian cancer patients. Two data set classification algorithms, Significance Analysis of Microarray and Prediction Analysis of Microarray, successfully identified 220 candidate PFS-discriminatory methylated loci. Of those, 112 were found capable of predicting PFS with 95% accuracy, by Prediction Analysis of Microarray, using an independent set of 40 advanced ovarian tumors (from 20 short-PFS and 20 long-PFS patients, respectively). Additionally, we showed the use of these predictive loci using two bioinformatics machine-learning algorithms, Support Vector Machine and Multilayer Perceptron. CONCLUSION: In this report, we show that highly prognostic DNA methylation biomarkers can be successfully identified and characterized, using previously unused, rigorous classifying algorithms. Such ovarian cancer biomarkers represent a promising approach for the assessment and management of this devastating disease.
Asunto(s)
Metilación de ADN , Neoplasias Ováricas/genética , Neoplasias Ováricas/patología , Adenocarcinoma/genética , Adenocarcinoma/patología , Biomarcadores de Tumor/análisis , Mapeo Cromosómico , Femenino , Humanos , Estadificación de Neoplasias , Análisis de Secuencia por Matrices de Oligonucleótidos , Pronóstico , Reproducibilidad de los ResultadosRESUMEN
Aberrant epigenetic regulation, such as CpG island methylation and associated transcriptional silencing of genes, has been implicated in a variety of human diseases, including cancer. Methylation of genes involved in apoptosis, including the DNA mismatch repair (MMR) gene hMLH1, can occur in tumor models of resistance to chemotherapeutic drugs. However, the relevance for acquired resistance to chemotherapy of patients' tumors remains unsubstantiated. Plasma DNA from cancer patients, including those with ovarian cancer, often contains identical DNA changes as the tumor and provides a means to monitor CpG island methylation changes. We have examined plasma DNA of patients with epithelial ovarian cancer enrolled in the SCOTROC1 Phase III clinical trial for methylation of the hMLH1 CpG island before carboplatin/taxoid chemotherapy and at relapse. Methylation of hMLH1 is increased at relapse, and 25% (34 of 138) of relapse samples have hMLH1 methylation that is not detected in matched prechemotherapy plasma samples. Furthermore, hMLH1 methylation is significantly associated with increased microsatellite instability in plasma DNA at relapse, providing an independent measure of function of the MMR pathway. Acquisition of hMLH1 methylation in plasma DNA at relapse predicts poor overall survival of patients, independent from time to progression and age (hazard ratio, 1.99; 95% confidence interval, 1.20-3.30; P = 0.007). These data support the clinical relevance of acquired hMLH1 methylation and concomitant loss of DNA MMR after chemotherapy of ovarian cancer patients. DNA methylation changes in plasma provide the potential to define patterns of methylation during therapy and identify those patient populations who would be suitable for novel epigenetic therapies.
Asunto(s)
ADN/sangre , Proteínas de Neoplasias/biosíntesis , Neoplasias Ováricas/genética , Proteínas Adaptadoras Transductoras de Señales , Alelos , Carboplatino/uso terapéutico , Proteínas Portadoras , Islas de CpG , ADN/metabolismo , Metilación de ADN , Progresión de la Enfermedad , Femenino , Silenciador del Gen , Humanos , Repeticiones de Microsatélite , Homólogo 1 de la Proteína MutL , Proteínas Nucleares , Neoplasias Ováricas/metabolismo , Paclitaxel/uso terapéutico , Reacción en Cadena de la Polimerasa , Modelos de Riesgos Proporcionales , Distribución Aleatoria , Recurrencia , Factores de Tiempo , Resultado del TratamientoAsunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/genética , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Biomarcadores de Tumor/genética , Neoplasias Ováricas/tratamiento farmacológico , Neoplasias Ováricas/genética , Paclitaxel/administración & dosificación , Subfamilia B de Transportador de Casetes de Unión a ATP , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/efectos de los fármacos , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Carboplatino/administración & dosificación , Carboplatino/efectos adversos , Ensayos Clínicos Fase III como Asunto , Supervivencia sin Enfermedad , Docetaxel , Femenino , Frecuencia de los Genes , Variación Genética , Genotipo , Humanos , Paclitaxel/efectos adversos , Paclitaxel/farmacocinética , Valor Predictivo de las Pruebas , Taxoides/administración & dosificación , Taxoides/efectos adversos , Resultado del TratamientoRESUMEN
PURPOSE: Standard therapy for advanced ovarian cancer consists of a platinum agent in combination with a taxane, which has a 5-year survival rate of approximately 45%. The large individual variability for ovarian cancer patients in both outcome and toxicity risk from chemotherapy makes the identification of pharmacogenetic markers that can be used to screen patients before therapy selection an attractive prospect. PATIENTS AND METHODS: We assessed 27 selected polymorphisms based on previously described associations or putative functional effects in 16 key genes from pathways that may influence cellular sensitivity to taxanes (ABCB1, ABCC1, ABCC2, ABCG2, CDKN1A, CYP1B1, CYP2C8, CYP3A4, CYP3A5, MAPT, and TP53) and platinum (ABCC2, ABCG2, ERCC1, ERCC2, GSTP1, MPO, and XRCC1) using polymerase chain reaction and Pyrosequencing in 914 ovarian cancer patients from the Scottish Randomised Trial in Ovarian Cancer phase III trial who were treated at presentation with carboplatin and taxane regimens after cytoreductive surgery. RESULTS: No reproducible significant associations between genotype and outcome or toxicity were found for any of the genes analyzed. Previously reported genotype associations could not be replicated in this large study of a well-defined patient population within one specific clinical trial. CONCLUSION: There are no clear candidates for taxane/platinum pharmacogenetic markers. This study highlights the need for validation of putative genetic markers in large, well-defined clinical sample sets.