Simonetta Guarrera1, Clara Viberti1, Giovanni Cugliari1, Alessandra Allione1, Elisabetta Casalone1, Marta Betti2, Daniela Ferrante3, Anna Aspesi2, Caterina Casadio4, Federica Grosso5, Roberta Libener6, Ezio Piccolini7, Dario Mirabelli8, Irma Dianzani9, Corrado Magnani10, Giuseppe Matullo11. 1. Italian Institute for Genomic Medicine, IIGM, Turin, Italy; Department of Medical Sciences, University of Turin, Turin, Italy. 2. Department of Health Sciences, University of Piemonte Orientale, Novara, Italy. 3. Medical Statistics and Cancer Epidemiology Unit, Department of Translational Medicine, University of Piemonte Orientale, Novara, Italy; Cancer Epidemiology Unit, CPO-Piemonte, Novara, Italy. 4. Thoracic Surgery Unit, AOU Maggiore Della Carità, Novara, Italy. 5. Division of Medical Oncology, SS. Antonio e Biagio General Hospital, Alessandria, Italy. 6. Pathology Unit, SS. Antonio e Biagio General Hospital, Alessandria, Italy. 7. Pneumology Unit, Santo Spirito Hospital, Casale Monferrato (AL), Italy. 8. Cancer Epidemiology Unit, Department of Medical Sciences, University of Turin, Turin, Italy; Cancer Epidemiology Unit, CPO Piemonte, Turin, Italy; Interdepartmental Center for Studies on Asbestos and Other Toxic Particulates "G. Scansetti," University of Turin, Turin, Italy. 9. Department of Health Sciences, University of Piemonte Orientale, Novara, Italy; Interdepartmental Center for Studies on Asbestos and Other Toxic Particulates "G. Scansetti," University of Turin, Turin, Italy. 10. Medical Statistics and Cancer Epidemiology Unit, Department of Translational Medicine, University of Piemonte Orientale, Novara, Italy; Cancer Epidemiology Unit, CPO-Piemonte, Novara, Italy; Interdepartmental Center for Studies on Asbestos and Other Toxic Particulates "G. Scansetti," University of Turin, Turin, Italy. 11. Italian Institute for Genomic Medicine, IIGM, Turin, Italy; Department of Medical Sciences, University of Turin, Turin, Italy; Interdepartmental Center for Studies on Asbestos and Other Toxic Particulates "G. Scansetti," University of Turin, Turin, Italy; Medical Genetics Unit, AOU Città della Salute e della Scienza, Turin, Italy. Electronic address: giuseppe.matullo@unito.it.
Abstract
INTRODUCTION: Malignant pleural mesothelioma (MPM) is an aggressive tumor strongly associated with asbestos exposure. Patients are usually diagnosed when current treatments have limited benefits, highlighting the need for noninvasive early diagnostic tests to monitor asbestos-exposed people. METHODS: We used a genome-wide methylation array to identify, in asbestos-exposed subjects, novel blood DNA methylation markers of MPM in 163 MPM cases and 137 cancer-free controls (82 MPM cases and 68 controls, training set; replication in 81 MPM cases and 69 controls, test set) sampled from the same areas. RESULTS: Evidence of differential methylation between MPM cases and controls was found (more than 800 cytosine-guanine dinucleotide sites, false discovery rate p value (pfdr) < 0.05), mainly in immune system-related genes. Considering the top differentially methylated signals, seven single- cytosine-guanine dinucleotides and five genomic regions of coordinated methylation replicated with similar effect size in the test set (pfdr < 0.05). The top hypomethylated single-CpG (cases versus controls effect size less than -0.15, pfdr < 0.05 in both the training and test sets) was detected in FOXK1 (Forkhead-box K1) gene, an interactor of BAP1 which was found mutated in MPM tissue and as germline mutation in familial MPM. In the test set, comparison of receiver operating characteristic curves and the area under the curve (AUC) of two models, including or excluding methylation, showed a significant increase in case/control discrimination when considering DNA methylation together with asbestos exposure (AUC = 0.81 versus AUC = 0.89, DeLong's test p = 0.0013). CONCLUSIONS: We identified signatures of differential methylation in DNA from whole blood between asbestos exposed MPM cases and controls. Our results provide the rationale to further investigate, in prospective studies, the potential use of blood DNA methylation profiles for the identification of early changes related to the MPM carcinogenic process.
INTRODUCTION:Malignant pleural mesothelioma (MPM) is an aggressive tumor strongly associated with asbestos exposure. Patients are usually diagnosed when current treatments have limited benefits, highlighting the need for noninvasive early diagnostic tests to monitor asbestos-exposed people. METHODS: We used a genome-wide methylation array to identify, in asbestos-exposed subjects, novel blood DNA methylation markers of MPM in 163 MPM cases and 137 cancer-free controls (82 MPM cases and 68 controls, training set; replication in 81 MPM cases and 69 controls, test set) sampled from the same areas. RESULTS: Evidence of differential methylation between MPM cases and controls was found (more than 800 cytosine-guanine dinucleotide sites, false discovery rate p value (pfdr) < 0.05), mainly in immune system-related genes. Considering the top differentially methylated signals, seven single- cytosine-guanine dinucleotides and five genomic regions of coordinated methylation replicated with similar effect size in the test set (pfdr < 0.05). The top hypomethylated single-CpG (cases versus controls effect size less than -0.15, pfdr < 0.05 in both the training and test sets) was detected in FOXK1 (Forkhead-box K1) gene, an interactor of BAP1 which was found mutated in MPM tissue and as germline mutation in familial MPM. In the test set, comparison of receiver operating characteristic curves and the area under the curve (AUC) of two models, including or excluding methylation, showed a significant increase in case/control discrimination when considering DNA methylation together with asbestos exposure (AUC = 0.81 versus AUC = 0.89, DeLong's test p = 0.0013). CONCLUSIONS: We identified signatures of differential methylation in DNA from whole blood between asbestos exposed MPM cases and controls. Our results provide the rationale to further investigate, in prospective studies, the potential use of blood DNA methylation profiles for the identification of early changes related to the MPM carcinogenic process.