Liquid Biopsies from Pleural Effusions and Plasma from Patients with Malignant Pleural Mesothelioma: A Feasibility Study

Abstract

Background: Malignant pleural mesothelioma (MPM) is a fatal tumor with a poor prognosis. The recent developments of liquid biopsies could provide novel diagnostic and prognostic tools in oncology. However, there is limited information about the feasibility of this technique for MPMs. Here, we investigate whether cancer-specific DNA sequences can be detected in pleural fluids and plasma of MPM patients as free circulating tumor DNA (ctDNA). Methods: We performed whole-exome sequencing on 14 tumor biopsies from 14 patients, and we analyzed 20 patient-specific somatic mutations with digital droplet PCR (ddPCR) in pleural fluids and plasma, using them as cancer-specific tumor biomarkers. Results: Most of the selected mutations could be detected in pleural fluids (94%) and, noteworthy, in plasma (83%) with the use of ddPCR. Pleural fluids showed similar levels of somatically mutated ctDNA (median = 12.75%, average = 16.3%, standard deviation = 12.3) as those detected in solid biopsies (median = 21.95%; average = 22.21%; standard deviation = 9.57), and their paired difference was weakly statistically significant (p = 0.048). On the other hand, the paired difference between solid biopsies and ctDNA from plasma (median = 0.29%, average = 0.89%, standard deviation = 1.40) was highly statistically significant (p = 2.5 × 10−7), corresponding to the important drop of circulating somatically mutated DNA in the bloodstream. However, despite the tiny amount of ctDNA in plasma, varying from 5.57% down to 0.14%, the mutations were detectable at rates similar to those possible for other tumors. Conclusions: We found robust evidence that mutated DNA is spilled from MPMs, mostly into pleural fluids, proving the concept that liquid biopsies are feasible for MPM patients.

Comparative analysis of genetic variants in pleural fluids and solid tissue biopsies of pleural mesothelioma patients: Implications for molecular heterogeneity assessment

“…This work reinforces previous observations [ 7 ] and adds additional pieces of evidence showing that PM releases tumour-derived DNA and malignant cells into the PFs [ 4 , 8 , 9 ]. The analysis of PFs for molecular characterization of this cancer has been poorly investigated.…”

Pleural mesothelioma (PMe): The evolving molecular knowledge of a rare and aggressive cancer

“…The deregulation of several miRNAs is a characteristic of PMe, regardless of histologic subtypes [ 122 ], and an assay validated on 68 samples based on the detection of three miRNAs reached a sensitivity of 100% and a specificity of 94% against adenocarcinoma [ 123 ]. In addition, it has been shown that miRNA and DNA molecules can be released from the cells into the body fluids [ 124 , 125 ], in which they are remarkably stable, being protected from endogenous RNAse activity [ 126 ]. In keeping with this, the circulating upregulated microRNAs miR‐197‐3p, miR‐1281, and miR‐32‐3p have been proposed as potential new biomarkers [ 127 ] in PMe, but further studies will be needed to prove the efficacy of such a screening methodology for the detection of both epithelioid and sarcomatoid cell types.…”

Malignant Mesothelioma

“…The diagnosis of MM could now benefit from the developments of ancillary tests, as reviewed by Dipper et al [ 5 ]. Moretti et al also analyzed tumor biopsy and liquid biopsies from a set of patients and demonstrated that most mutated DNA can be detected into pleural fluids [ 6 ].…”