It is my pleasure to present our study investigating the diagnostic potential of novel mesothelioma-specific microRNA. One of the major challenges when dealing with malignant pleuromesothelioma is that of being able to obtain an accurate and ideally also early diagnosis. In particular, the differential diagnosis between MPM and cancers that have metastasized to the pleura can be rather challenging. Tissue-specific biomarkers could actually help to overcome these difficulties, and in this context in particular microRNAs have been suggested to be very useful. And indeed, a recent study by Martinez and colleagues has shown that previously undetected microRNAs are able to distinguish MPM from NSCLC. In our present study, we aim to validate these findings in an independent cohort using an alternative detection approach. Just a few more words on the study by Martinez and colleagues. They analyzed the small RNA-seq data of the 87-patient MPM-TCGA cohort compared to approximately 1,000 lung and breast cancer cases respectively. A number of microRNA sequences were identified, with 424 of those being not annotated. Out of those, 154 novel candidates previously undetected in MPM were shown to be able to distinguish with high confidence MPM, shown here in the purple circles, from lung cancer and breast cancer. The top 10 of these 154 candidates are now subject to our study. In our preliminary study, we are evaluating the diagnostic tissue specimens of 20 MPM patients and 8 non-MPM patients. We are also using two cell lines as controls. And we are applying a novel, recently published, two-tailed RT-qPCR method for detection of the 10 novel MPM mirrors, a reference gene, and some positive controls. In the table on this slide here, you can see the baseline characteristics of our MPM and non-MPM groups. In terms of result, as a first step, we had to evaluate if this two-tailed RT-qPCR is actually able to detect microRNAs in our samples. We started with our cell line samples, and we could indeed see that our positive controls as well as our endogenous reference were detectable in these samples. And the amplification levels were comparable to those of Tuckman-based RT-qPCR. Eight of the 10 novel MPM microRNAs were in addition also detectable in our two cell lines. In the next step, in the preliminary analysis, we assess the expression levels of three candidates in our 20 MPM patients and eight non-malignant controls. What we could see was that these three MPM microRNAs are actually not only detectable in MPM, they were also detectable in the non-MPM samples, but they were actually also significantly increased in the case of mu136, actually 23-fold, in the MPM compared to the non-MPM tissue. In addition, we assessed the genomic location of these microRNAs, and we could show that miR-18 is located in the gene TRAF4, while miR-58 is located in the pseudogene CA5PP1. Analysis of the TCGA mesodata then revealed that the expression of the host gene of miR-18, TRAF4, might be associated with survival, although the survival difference did not reach statistical significance, as you can see in this Kaplan-Meier curve here. And together, we have so far been able to show that these novel MPM microRNAs are detectable by alternative detection approaches, and we were able to validate the expression of some of the novel MPM microRNAs in an independent patient sample set. We could furthermore show that expression is not limited to the malignant mesothelium tissue, but they are also expressed in non-malignant tissue, but they are significantly increased in the tumor samples compared to the non-malignant controls, suggesting that these novel MPM microRNAs might indeed hold diagnostic potential. In the next steps, we are now further optimizing our PCR conditions and are analyzing the remaining MPM microRNAs in the so far evaluated tissue specimens. In addition, we will include additional tissue samples, also NSCLC samples, and will in the next step then validate the molecular classifier consisting of 10 microRNAs to discriminate MPM from NSCLC. Thank you very much for your attention.

mesothelioma-specific microRNAs

malignant pleuromesothelioma

novel MPM microRNAs

diagnostic potential

MPM vs. non-MPM cancers