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The role of IL‐10 in malignant pleural effusion (MPE) remains unknown. By using murine MPE models, we observed that an increase in pleural IL‐10 was a significant predictor of increased risk of death. We noted that TH1‐ and TH17‐cell content in MPE was higher in IL‐10–/– mice than in WT mice, and IL‐10 deficiency promoted differentiation into TH1 but not into TH17 cells. A higher fraction of TH1 and TH17 cells in the MPE of IL‐10–/– mice expressed CXCR3 compared with WT mice. We also demonstrated that Lewis lung cancer and colon adenocarcinoma cells secreted large amounts of CXCL10, a ligand of CXCR3, which induced the migration of TH1 and TH17 cells into the MPE, and IFN‐γ could promote this signaling cascade. Furthermore, intrapleural injection of mice with CXCL10‐deficient tumor cells led to decreased TH1‐ and TH17‐cell content in MPE, increased MPE volume, and reduced survival of MPE‐bearing mice. Taken together, we demonstrated that IL‐10 deficiency promoted T‐cell differentiation into TH1 cells and upregulated the CXCR3‐CXCL10 signaling pathway that recruits TH1 and TH17 cells into MPE, ultimately resulting in decreased MPE formation and longer survival time of mice‐bearing MPE. IL‐10 promoted the development of malignant pleural effusion by suppressing the differentiation of naïve CD4+ T cells into TH1 cells and by suppressing the CXCR3‐CXCL10 signal that traffics TH1 and TH17 cells into the pleural space. [ABSTRACT FROM AUTHOR]

Emerging evidence indicates that Myo9b is a cancer metastasis-related protein and functions in a variety of immune-related diseases. However, it is not clear whether and how Myo9b functions in malignant pleural effusion (MPE). In this study, our data showed that Myo9b expression levels correlated with lung cancer pleural metastasis, and nucleated cells in MPE from either patients or mice expressed a lower level of Myo9b than those in the corresponding blood. Myo9b deficiency in cancer cells suppressed MPE development via inhibition of migration. Myo9b deficiency in mice suppressed MPE development by decreasing T H 1 cells and increasing T H 17 cells. CD4 + naive T cells isolated from Myo9b -/- mouse spleens exhibited less T H 1 cell differentiation and more T H 17 cell differentiation in vitro. mRNA sequencing of nucleated cells showed that T cell-specific adaptor protein (TSAd) was downregulated in Myo9b -/- mouse MPE, and enrichment of the H3K27me3 mark in the TSAd promoter region was found in the Myo9b -/- group. Naive T cells purified from wild type mouse spleens transfected with TSAd-specific small interfering RNAs (siRNAs) also showed less T H 1 cell differentiation and more T H 17 cell differentiation than those from the siRNA control group. Furthermore, downregulation of TSAd in mice using cholesterol-conjugated TSAd-specific siRNA suppressed MPE development, decreased T H 1 cells, and increased T H 17 cells in MPE in vivo. Taken together, Myo9b deficiency suppresses MPE development not only by suppressing pleural cancer metastasis but also by regulating T H 1/T H 17 cell response via a TSAd-dependent pathway. This work suggests Myo9b and TSAd as novel candidates for future basic and clinical investigations of cancer., (Copyright © 2020 by The American Association of Immunologists, Inc.)

Background: Pleural effusions are common complications of various diseases. Patients with malignant pleural effusion (MPE) usually face poor prognosis and short life expectancy. Discriminating between MPE and benign pleural effusion remains to be difficult. The aim of our current study was to evaluate whether CD206 + CD14 + macrophages could be a diagnostic biomarker for MPE., Methods: The percentages of CD14 + , CD86 + CD14 + and CD206 + CD14 + macrophages in pleural effusions were determined by flow cytometry in 34 patients with MPE and 26 with benign pleural effusion, and their diagnostic performances were evaluated by receiver operating characteristic (ROC) curves., Results: The percentages of CD14 + , CD86 + CD14 + and CD206 + CD14 + macrophages were remarkably higher in MPE than in benign pleural effusion (all P<0.05). With a cutoff value of 39.8%, a high sensitivity of 88.2% and high specificity of 100.0% were found in CD206 + CD14 + macrophages to diagnose MPE. The area under the curve, positive predictive value and negative predictive value of CD206 + CD14 + macrophages were 0.980 (95% CI, 0.905 to 0.999), 100.0 (88.4 to 100.0) and 86.7 (69.3 to 96.2), respectively. The diagnostic performance of CD206 + CD14 + macrophages was more accurate than those of CD14 + and CD86 + CD14 + macrophages., Conclusions: CD206 + CD14 + macrophages could be used to discriminate MPE from benign pleural effusion., Competing Interests: Conflicts of Interest: The authors have no conflicts of interest to declare.

Inflammatory signaling networks between tumor cells and immune cells contribute to the development of malignant pleural effusion (MPE). B cells have been found in MPE; however, little is known about their roles there. In the present study, by using mouse MPE models, we noted that although the total B cells in MPE were decreased as compared with the corresponding blood and spleen, the percentage of activated naïve B cells expressing higher levels of CD80, CD86, myosin heavy chain-II, CD44, CD69, and programmed cell death-ligand 1 (PD-L1) molecules were increased in wild-type mouse MPE. Compared with wild-type mice, decreased T helper (T H )1 cells and increased T H 17 cells were present in B cell-deficient mouse MPE, which paralleled to the reduced MPE volume and longer survival time. Adoptive transfer of activated naïve B cells into B cell-deficient mice was able to increase T H 1 cells and decrease T H 17 cells in MPE and shorten the survival of mice bearing MPE. Furthermore, we demonstrated that activated naïve B cells inhibited T H 17-cell expansion via the PD-1/PD-L1 pathway and promoted naïve CD4 + T-cell differentiation into T H 1/T H 17 cells through secreting IL-27/IL-6 independent of the PD-1/PD-L1 pathway. Collectively, our data uncovered a mechanism by which naïve B cells promote MPE formation by regulating T H 1/T H 17 cell responses, making these B cells an attractive target for therapeutic intervention in the fight against cancer.