Tumour markers are standard tools for the differential diagnosis of cancer. However, the occurrence of nonspecific symptoms and different malignancies involving the same cancer site may lead to a high proportion of misclassifications.

Pleural mesothelioma (PM) is an aggressive tumor with few therapeutic options. Although patients with epithelioid PM (ePM) survive longer than non-epithelioid PM (non-ePM), heterogeneity of tumor response in ePM is observed. The role of the tumor immune microenvironment (TIME) in the development and progression of PM is currently considered a promising biomarker. A few studies have used high-throughput technologies correlated with TIME evaluation and morphologic and clinical data. This study aimed to identify different morphological, immunohistochemical, and transcriptional profiles that could potentially predict the outcome. A retrospective multicenter cohort of 129 chemonaive PM patients was recruited. Tissue slides were reviewed by dedicated pathologists for histotype classification and immunophenotype of tumor-infiltrating lymphocytes (TILs) and lymphoid aggregates or tertiary lymphoid structures (TLS). ePM (n = 99) survivors were further classified into long (>36 months) or short (<12 months) survivors. RNAseq was performed on a subset of 69 samples. Distinct transcriptional profiling in long and short ePM survivors was found. An inflammatory background with a higher number of B lymphocytes and a prevalence of TLS formations were detected in long compared to short ePM survivors. These results suggest that B cell infiltration could be important in modulating disease aggressiveness, opening a pathway for novel immunotherapeutic approaches.

Background: Malignant pleural mesothelioma (MPM) is a tumor known to be resistant to conventional therapies. Thus, an in vivo model can represent an important tool for assessing the efficacy of novel approaches in the treatment of MPM. Presently, human MPM cells have been grown orthotopically in mice upon transplantation of tumor masses or tumor cell suspensions following surgery. In these models however, surgery can interfere with the tumor growth and the early stages of tumor development cannot be easily explored. Finally, results may not be so accurate due to implantation of potentially different tumor samples in different experimental groups. Our work aimed at establishing a nude mouse model xenotransplanted with human MPM cell lines in which tumor progression exhibits some features of the human disease. Methods: Three distinct human MPM cell lines previously established from MPM patients displaying two different phenotypes, biphasic (MM-B1 and IST-Mes3) and epithelioid (IST-Mes2), were directly injected into the pleural cavity of nude mice. At different times, mice were sacrificed for autopsy, tumor nodules were counted and then removed for histology. Presence of metastases in visceral organs was also monitored. Results: IST-Mes2 cells were unable to grow in nude mice. MM-B1 and IST-Mes3 cells were capable of growing in nude mice and formed tumor nodules in the pleura. Post-mortem examination showed that MPM cells progressively colonized the parietal and visceral pleura, the diaphragm, the mediastinum and, lastly the lung parenchyma. No pneumo-thorax was evidenced in the mice. Pleural effusions as well as lymph node metastases were observed only at later times. Conclusion: This model mimics the progression of human malignant mesothelioma and it is easy to perform and reproducible; therefore it can be useful to study human MPM biology and evaluate the efficacy of novel therapies.

Malignant pleural mesothelioma (MPM) is a rare and aggressive neoplasm. Patients are usually diagnosed when current treatments have limited benefits, highlighting the need for noninvasive tests aimed at an MPM risk assessment tool that might improve life expectancy. Three hundred asbestos-exposed subjects (163 MPM cases and 137 cancer-free controls), from the same geographical region in Italy, were recruited. The evaluation of asbestos exposure was conducted considering the frequency, the duration and the intensity of occupational, environmental and domestic exposure. A genome-wide methylation array was performed to identify novel blood DNA methylation (DNAm) markers of MPM. Multiple regression analyses adjusting for potential confounding factors and interaction between asbestos exposure and DNAm on the MPM odds ratio were applied. Epigenome-wide analysis (EWAS) revealed 12 single-CpGs associated with the disease. Two of these showed high statistical power (99%) and effect size (>0.05) after false discovery rate (FDR) multiple comparison corrections: (i) cg03546163 in FKBP5, significantly hypomethylated in cases (Mean Difference in beta values (MD) = −0.09, 95% CI = −0.12|−0.06, p = 1.2 × 10⁻⁷), and (ii) cg06633438 in MLLT1, statistically hypermethylated in cases (MD = 0.07, 95% CI = 0.04|0.10, p = 1.0 × 10⁻⁶). Based on the interaction analysis, asbestos exposure and epigenetic profile together may improve MPM risk assessment. Above-median asbestos exposure and hypomethylation of cg03546163 in FKBP5 (OR = 20.84, 95% CI = 8.71|53.96, p = 5.5 × 10⁻¹¹) and hypermethylation of cg06633438 in MLLT1 (OR = 11.71, 95% CI = 4.97|29.64, p = 5.9 × 10⁻⁸) genes compared to below-median asbestos exposure and hyper/hypomethylation of single-CpG DNAm, respectively. Receiver Operation Characteristics (ROC) for Case-Control Discrimination showed a significant increase in MPM discrimination when DNAm information was added in the model (baseline model, BM: asbestos exposure, age, gender and white blood cells); area under the curve, AUC = 0.75; BM + cg03546163 at FKBP5. AUC = 0.89, 2.1 × 10⁻⁷; BM + cg06633438 at MLLT1. AUC = 0.89, 6.3 × 10⁻⁸. Validation and replication procedures, considering independent sample size and a different DNAm analysis technique, confirmed the observed associations. Our results suggest the potential application of DNAm profiles in blood to develop noninvasive tests for MPM risk assessment in asbestos-exposed subjects.