SPARC Is a Novel Positive Immunohistochemical Marker of Epithelioid Mesothelioma to Differentiate It From Lung Adenocarcinoma and/or Squamous Cell Carcinoma.

Epithelioid mesothelioma with a solid histologic pattern (solid epithelioid mesothelioma) is difficult to distinguish from a poorly differentiated squamous cell lung carcinoma and/or solid lung adenocarcinoma. Thus, immunohistochemical markers are essential for diagnosis; however, the sensitivity and specificity of pre-existing mesothelial markers are suboptimal, particularly for differentiation from squamous cell carcinoma. Using a cancer-dependency map, we analyzed gene expression data of pleural mesothelioma and non-small cell lung cancer cell lines (squamous cell carcinoma and adenocarcinoma) and identified secreted protein acidic and cysteine-rich (SPARC) as a promising candidate for the differential diagnosis of epithelioid mesothelioma from lung squamous cell carcinoma and/or lung adenocarcinoma. SPARC expression in mesothelioma and lung cancer cell lines was validated using reverse-transcription polymerase chain reaction, western blotting, and immunohistochemistry. Immunohistochemical staining was performed using anti-SPARC antibodies against solid epithelioid mesothelioma, solid lung adenocarcinoma, and poorly differentiated lung squamous cell carcinoma. SPARC positivity was seen in 42/45 (93.3%) of solid epithelioid mesothelioma, 2/40 (5%) solid lung adenocarcinoma, and 2/45 (4.5%) of lung squamous cell carcinomas. The sensitivity, specificity, and diagnostic accuracy for differentiating solid epithelioid mesothelioma from lung cancer (solid lung adenocarcinoma and poorly differentiated lung squamous cell carcinoma) were 93.3, 95.2, and 94.6%, respectively. In conclusion, SPARC is a novel mesothelial marker that can be used to differentiate epithelioid mesothelioma from squamous cell carcinoma and lung adenocarcinoma.

Long Non-coding RNA LINC00152 Requires EZH2 to Promote Mesothelioma Cell Proliferation, Migration, and Invasion.

BACKGROUND/AIM: Long non-coding RNAs (lncRNAs) establish gene regulatory networks in different human cancers and are involved in tumorigenesis. lncRNA LINC00152 is over-expressed in several malignant tumors and involved in tumorigenesis; however, its underlying regulatory mechanisms remain unclear. Mesothelioma, a cancer originating from mesothelial cells, is highly aggressive with a poor prognosis. Therefore, identification of new therapeutic targets is necessary for mesothelioma treatment. MATERIALS AND METHODS: Here, we conducted bioinformatics analyses of LINC00152 and enhancer of zeste homolog 2 (EZH2) expression levels and their correlation with the prognosis of patients with mesothelioma. Small interfering RNAs targeting LINC00152 and EZH2 were transfected into mesothelioma cell lines to analyze their biological functions and regulatory mechanisms. RESULTS: High LINC00152 expression was associated with a poor prognosis of patients with mesothelioma. LINC00152 knockdown inhibited the proliferation, migration, and invasion of mesothelioma cell lines. These results suggest that LINC00152 is a tumor-promoting factor in mesothelioma. EZH2 is highly expressed in mesothelioma and other malignancies. Direct interaction between LINC00152 and EZH2 is associated with cancer development and progression. When EZH2 expression was suppressed, LINC00152 knockdown did not suppress the proliferation, migration, and invasion of mesothelioma cells. Therefore, the tumor-promoting effect of LINC00152 in mesothelioma was dependent on EZH2 expression. CONCLUSION: LINC00152 promotes mesothelioma cell proliferation, migration, and invasion in cooperation with EZH2, highlighting its potential as an effective therapeutic target for mesothelioma.

FOXM1 Promotes Mesothelioma Cell Migration and Invasion via Activation of SMAD Signaling.

BACKGROUND/AIM: Forkhead box M1 (FOXM1) is a transcription factor closely associated with various human malignancies and is considered an attractive target for cancer therapy. Mesothelioma is a malignancy primarily due to asbestos exposure and certain genetic factors, requiring a better understanding of tumorigenesis for improved treatment. Asbestos-exposed human mesothelial cells have been reported to up-regulate FOXM1 expression in a dose-dependent manner. MATERIALS AND METHODS: FOXM1 expression was evaluated in mesothelioma tissues and cell lines. FOXM1 small interfering RNA was transfected into mesothelioma cell lines to analyze its biological functions and regulatory mechanisms. RESULTS: FOXM1 was over-expressed in mesothelioma tissues and cell lines. Knock-down of FOXM1 in mesothelioma cell lines inhibited cell proliferation, migration, and invasion. These results suggest that up-regulation of FOXM1 expression promotes mesothelioma tumorigenesis and progression. We previously reported that insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) promotes the proliferation, migration, and invasion of mesothelioma cell lines. In this study, IGF2BP3 knock-down suppressed FOXM1 expression in mesothelioma cell lines. Our results suggest that IGF2BP3, an upstream regulator, contributes to increased FOXM1 expression. Furthermore, IGF2BP3 and FOXM1 knock-down suppressed SMAD signaling by inhibiting SMAD2/3 phosphorylation in mesothelioma cell lines. CONCLUSION: IGF2BP3/FOXM1 promotes mesothelioma cell migration and invasion via SMAD signaling, highlighting IGF2BP3/FOXM1 as a potential target for mesothelioma treatment.

miR-142-3p Suppresses Invasion and Adhesion of Mesothelioma Cells by Downregulating ITGAV.

INTRODUCTION: Malignant mesothelioma is an aggressive cancer associated with asbestos exposure. Currently, the efficacy of therapeutics is limited in malignant mesothelioma, and developing more effective therapies is the need of the hour. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs), have attracted attention as therapeutic targets. To explore potential therapeutic targets, we focused on miR-142-3p expression, which was found to be significantly downregulated in mesothelioma cell lines in our previous study. METHODS: Mesothelioma cell lines and tissues were validated for expression of miR-142-3p or integrin subunit alpha-V (ITGAV). We transfected mesothelioma cell lines with miR-142-3p mimic and ITGAV siRNA and analyzed their biological functions. RESULTS: We found that miR-142-3p was significantly downregulated in mesothelioma tissues. Transfection with miR-142-3p mimic significantly suppressed cell proliferation, migration, and invasion. Bioinformatics analysis of potential targets of miR-142-3p identified ITGAV. Membrane ITGAV expression in mesothelioma cell lines was confirmed using immunocytochemistry. ITGAV was significantly upregulated in mesothelioma tissues. Moreover, transfection of miR-142-3p mimics into mesothelioma cell lines significantly suppressed ITGAV expression, indicating that miR-142-3p targets ITGAV. Next, ITGAV siRNA transfection into mesothelioma cell lines inhibited cell proliferation, migration, and invasion. Further investigation of cell adhesion mechanisms showed that the miR-142-3p/ITGAV axis specifically affects mesothelioma cell adhesion via vitronectin in the extracellular matrix. CONCLUSION: This study proposed that the miR-142-3p/ITGAV axis is involved in tumor progression in malignant mesothelioma.

Insulin-Like Growth Factor 2 mRNA Binding Protein 3 Promotes Cell Proliferation of Malignant Mesothelioma Cells by Downregulating p27Kip1.

Malignant mesothelioma is a tumor with a poor prognosis, mainly caused by asbestos exposure and with no adequate treatment yet. To develop future therapeutic targets, we analyzed the microarray dataset GSE 29370 of malignant mesothelioma and reactive mesothelial hyperplasia, downloaded from the Gene Expression Omnibus (GEO) database. We identified insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) as one of the significantly upregulated genes in malignant mesothelioma. IGF2BP3 functions as an oncoprotein in many human cancers; however, to our knowledge, this is the first study on the biological function of IGF2BP3 in malignant mesothelioma cells. The knockdown of IGF2BP3 in malignant mesothelioma cells resulted in the suppression of cell proliferation with an increase in the proportion of cells in the G1 phase of the cell cycle. Furthermore, knockdown of IGF2BP3 inhibited cell migration and invasion. We focused on the cell cycle assay to investigate the role of IGF2BP3 in cell proliferation in malignant mesothelioma. Among the various proteins involved in cell cycle regulation, the expression of p27 Kip1 (p27) increased significantly upon IGF2BP3 knockdown. Next, p27 siRNA was added to suppress the increased expression of p27. The results showed that p27 knockdown attenuated the effects of IGF2BP3 knockdown on cell proliferation and G1 phase arrest. In conclusion, we found that IGF2BP3 promotes cell proliferation, a critical step in tumorigenesis, by suppressing the expression of p27 in malignant mesothelioma.