MICRORNAS IN EXHALED BREATH CONDENSATE AND BLOOD AS BIOMARKER OF PLEURAL MALIGNANT MESOTHELIOMA AND ASBESTOS EXPOSURE

Malignant Pleural Mesothelioma (MPM) is an aggressive cancer refractory to current therapies, the incidence of which is expected to rise in the next decades. Exposure to asbestos is a well-known MPM risk factor. To date, diagnosis is hard to determine, due to a lack of proper markers to specifically identify malignant pleural mesothelioma, since it might be confused with lung-originated metastatic neoplasm. MiRNAs are single stranded noncoding RNAs of 20-22 nucleotides that post-transcriptionally regulate gene expression by triggering mRNA cleavage or repressing translation. One single miRNA can regulate hundreds of mRNAs and a single mRNA can be targeted by several different miRNAs. Changes in the expression of miRNAs have been implicated in several diseases, including MPM. miRNAs are stable molecules that can be easily investigated in different specimens (e.g. blood), and used as a disease biomarker. Exhaled breath condensate (EBC) collection is a standardized, non-invasive technique and collected EBC is representative of lung environment. miRNAs measured in EBC/blood could help evaluating asbestos exposed subjects and MPM development. Specific aims of the project are: Aim 1: Determine whether a specific miRNA signature (in plasma or EBC) may help to discriminate between malignant pleural mesothelioma patients and patients affected by other pulmonary diseases, among patients presenting at the Thoracic Surgery Unit with a diagnosis of pleural effusion. Aim 2: Determine whether a specific miRNA signature (in plasma or EBC) may help to discriminate between Malignant Pleural Mesothelioma (MPM) patients and healthy subjects with a Past Exposure to Asbestos (PEA). Aim 3: Evaluate a possible correlation between miRNAs in EBC and plasma. Aim 4: Estimate sensitivity and specificity of altered miRNAs using ROC curves. To address this hypothesis we investigated a population including 23 MPM patients, 19 healthy subjects with a Past Asbestos Exposure (PEA), and 9 subjects with pleural effusions and affected by other diseases. In this study population we screened 733 miRNAs in blood and EBC by high-throughput Open Array. To investigate the possible miRNAs expression deregulation between the cases and controls, we used a multiple linear regression model adjusted for four principal variables (age, sex, BMI and smoking habits) and identified 6 candidate miRNAs in EBC and 13 in plasma. After Real Time validation, we identified one miRNA in EBC (hsa-miR-30a-5p) and three miRNAs in plasma (hsa-miR-151-5p, hsa-miR-107, and hsa-let-7e-5p), able to discriminate between MPM and PEA subjects. The combination of the 4 miRNAs gives even a better score, with a ROC curve which shows an AUC = 0.85. To our knowledge, this is the first study in MPM which investigate miRNA expression in EBC and identify a 4-miRNA signature which might be useful for MPM diagnosis. This signature might help identifying subjects with an increased risk of developing MPM after exposure to asbestos.