Abstract 4008: MiRNA expression profiling reveals a prognostic signature in malignant pleural mesothelioma
Authors: Truini Anna , Coco Simona , Nadal Ernest , Genova Carlo , Dal Bello Maria Giovanna , Vanni Irene , Alama Angela , Beer David G. , Grossi Francesco 
Published: August 2015

Abstract
Introduction: Malignant pleural mesothelioma (MPM) is an aggressive tumor predominantly associated with asbestos exposure. Patients diagnosed with MPM have a poor outcome (median survival 10 months) and novel diagnostic and therapeutic approaches are needed. MicroRNAs (miRNAs) play a role in tumorigenesis and progression in MPM. The aim of this study was to identify miRNAs associated with poor prognosis in MPM which may be potentially actionable targets in the future.
Materials and methods: We identified 11 MPM long survivors (LS,&gt;36 months) and 15 MPM short survivors (SS,&lt;12 months) diagnosed at the IRCCS AOU San Martino-IST (Genova) from 1998-2008 that did not undergo tumor resection. Sections from FFPE biopsy blocks were macrodissected and total RNA was extracted. Twenty-six MPM and 3 additional normal pleura samples were miRNA profiled using the Agilent Human miRNA Microarray 8×60K including 2006 miRNAs. Expression data were normalized using GeneSpring software (v.12.6). Class-comparison analysis between MPM/pleura and SS/LS was performed using a t-test adjusted for multiple comparisons using Benjamini-Hochberg. Overall survival (OS) curves were estimated using the Kaplan-Meier method and compared with the log-rank test. In silico validation was performed using miRNAseq data from TCGA portal based upon 16 cases with survival data (LS: 8 patients; SS: 8 patients). Candidate miRNAs were assessed by univariate analysis using Kaplan-Meier method and median as cutoff.
Results: Patients’ characteristics: median age, 67 years (53-77); males (81%), females (19%). The most frequent histotype was epithelioid (69%), followed by sarcomatoid (12%), biphasic (4%) and unknown (15%). No differences in age, gender and histotype were observed among LS and SS. By class-comparison analysis, 30 miRNAs were significantly up-regulated and 11 down-regulated in MPM vs normal pleura (adjusted p-value &lt;0.05). Fourteen miRNAs were significantly associated with outcome, in the univariate survival analysis and differentially expressed in MPM. A miRNA signature was calculated based on the top 6 prognostic miRNAs (unfavorable, miR-1224; favorable, miR-99a, miR-125b, let-7b, let-7c and let-7i) and patients were classified into low or high-risk. High-risk MPM patients had a significantly shorter median OS (4.1 months, 95% CI 2.2-5.9) as compared with low-risk patients (median not reached, Log-rank p&lt;0.001). In silico validation analysis using TCGA miRNAseq data, confirmed that low expression of mir-99a, miR-125b and let-7c was associated with shorter OS. Relevant pathways, such as PI3K/AKT, WNT were associated with these top miRNAs by pathway analysis.
Conclusion: A prognostic miRNA signature was identified by profiling a cohort of unresected MPM, underlying the clinical potential of miRNAs in prediction of survival. An additional validation in a larger independent cohort of MPM is ongoing.
Citation Format: Anna Truini, Simona Coco, Ernest Nadal, Carlo Genova, Maria Giovanna Dal Bello, Irene Vanni, Angela Alama, David G. Beer, Francesco Grossi. MiRNA expression profiling reveals a prognostic signature in malignant pleural mesothelioma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4008. doi:10.1158/1538-7445.AM2015-4008