Comparative proteomic analysis of malignant pleural mesothelioma: Focusing on the biphasic subtype

Role of Prosaposin and Extracellular Sulfatase Sulf-1 Detection in Pleural Effusions as Diagnostic Biomarkers of Malignant Mesothelioma

Malignant pleural mesothelioma is an aggressive malignancy with poor prognosis. Unilateral pleural effusion is frequently the initial clinical sign requiring therapeutic thoracentesis, which also offers a diagnostic opportunity. Detection of soluble biomarkers can support diagnosis, but few show good diagnostic accuracy. Here, we studied the expression levels and discriminative power of two putative biomarkers, prosaposin and extracellular sulfatase SULF-1, identified by proteomic and transcriptomic analysis, respectively. Pleural effusions from a total of 44 patients (23 with mesothelioma, 8 with lung cancer, and 13 with non-malignant disease) were analyzed for prosaposin and SULF-1 by enzyme-linked immunosorbent assay. Pleural effusions from mesothelioma patients had significantly higher levels of prosaposin and SULF-1 than those from non-malignant disease patients. Receiver-operating characteristic (ROC) analysis showed that both biomarkers have good discriminating power as pointed out by an AUC value of 0.853 (p = 0.0005) and 0.898 (p < 0.0001) for prosaposin and SULF-1, respectively. Combining data ensued a model predicting improvement of the diagnostic performance (AUC = 0.916, p < 0.0001). In contrast, prosaposin couldn’t discriminate mesothelioma patients from lung cancer patients while ROC analysis of SULF-1 data produced an AUC value of 0.821 (p = 0.0077) but with low sensitivity. In conclusion, prosaposin and SULF-1 levels determined in pleural effusion may be promising biomarkers for differential diagnosis between mesothelioma and non-malignant pleural disease. Instead, more patients need to be enrolled before granting the possible usefulness of these soluble proteins in differentiating mesothelioma pleural effusions from those linked to lung cancer.

Identification of Redox-Sensitive Transcription Factors as Markers of Malignant Pleural Mesothelioma

Simple Summary

Malignant pleural mesothelioma is a lung tumor associated with asbestos exposure, with a poor prognosis, and a difficult pharmacological approach. Asbestos exposure is very toxic for the lungs, which counteract this toxic effect by activating some antioxidant defense proteins. When these proteins are more active that in normal conditions, as in several cancers, these tumors become able to survive and resist to stress or chemotherapy. In our laboratory, we collected cellular samples of mesothelioma and non-transformed mesothelium from Hospital’s Biobank and we evaluated these proteins. Our results demonstrated these proteins are upregulated in mesothelioma cells and not in non-transformed mesothelium. This event could be associated to toxic effects evoked by asbestos exposure, highlighting the need in the future to monitor asbestos-exposed people by measuring biomarkers identified, in the attempt to identify them as possible predictive markers and potential pharmacological targets addressed to improve mesothelioma prognosis.

Abstract

Although asbestos has been banned in most countries around the world, malignant pleural mesothelioma (MPM) is a current problem. MPM is an aggressive tumor with a poor prognosis, so it is crucial to identify new markers in the preventive field. Asbestos exposure induces oxidative stress and its carcinogenesis has been linked to a strong oxidative damage, event counteracted by antioxidant systems at the pulmonary level. The present study has been focused on some redox-sensitive transcription factors that regulate cellular antioxidant defense and are overexpressed in many tumors, such as Nrf2 (Nuclear factor erythroid 2-related factor 2), Ref-1 (Redox effector factor 1), and FOXM1 (Forkhead box protein M1). The research was performed in human mesothelial and MPM cells. Our results have clearly demonstrated an overexpression of Nrf2, Ref-1, and FOXM1 in mesothelioma towards mesothelium, and a consequent activation of downstream genes controlled by these factors, which in turn regulates antioxidant defense. This event is mediated by oxidative free radicals produced when mesothelial cells are exposed to asbestos fibers. We observed an increased expression of Nrf2, Ref-1, and FOXM1 towards untreated cells, confirming asbestos as the mediator of oxidative stress evoked at the mesothelium level. These factors can therefore be considered predictive biomarkers of MPM and potential pharmacological targets in the treatment of this aggressive cancer.

New vistas in malignant mesothelioma: MicroRNA architecture and NRF2/MAPK signal transduction

Malignant mesothelioma (MM) is a cancer of the mesothelial lining of the pleura, peritoneum, pericardium and testes. The most common form is asbestos-linked MM that is etiologically linked to repeated asbestos exposure with a long latency period, although non-asbestos MM has also been reported. Late diagnosis, poor survival rates, lack of diagnostic and prognostic markers act as major impediments in the clinical management of MM. Despite advances in immune checkpoint inhibition and CAR T-cell-based therapies, MM which is of different histologic subtypes remains challenging to treat. We review microRNAs (miRNAs) and the miRNA interactome implicated in MM which can be useful as circulating miRNA biomarkers for early diagnosis of MM and as biomarkers for prognostication in MM. Further, we underscore the relevance of the NRF2/MAPK signal transduction pathway that has been implicated in MM which may be useful as druggable targets or as biomarkers of predictive response. In addition, since MM is driven partly by inflammation, we elucidate chemopreventive phytochemicals that are beneficial in MM, either via crosstalk with the NRF2/MAPK pathway or via concerted anticancer mechanisms, and may be of benefit as adjuvants in chemotherapy. Taken together, a multifactorial approach comprising identification of miRNA target hubs and NRF2/MAPK biomarkers along with appropriately designed clinical trials may enable early detection and faster intervention in MM translating into better patient outcomes for this aggressive cancer.