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Interleukin-10 (IL-10) promotes the formation and development of malignant pleural effusion (MPE). Previous studies have elucidated the pathogenesis from the view of the immune-regulation function of CD4 + T-cells. However, the underlying mechanism is still not fully understood. In this study, our results showed that IL-10 deficiency reduced the percentage of macrophages in mouse MPE and regulated M1/M2 polarization in vivo and in vitro . The migration capacity of tumor cells was suppressed, and apoptosis was promoted when tumor cells were cocultured with MPE macrophages in the absence of IL-10. Messenger RNA sequencing of MPE macrophages showed that S100A9 was downregulated in IL-10 -/- mice. Bone marrow-derived macrophages obtained from wild-type mice transfected with S100A9-specific small interfering RNAs (siRNAs) also showed less M2 and more M1 polarization than those from the siRNA control group. Furthermore, downregulation of S100A9 using S100A9-specific siRNA suppressed MPE development, decreased macrophages, and modulated macrophage polarization in MPE in vivo . In conclusion, S100A9 plays a vital role in the process of IL-10 deficiency-mediated MPE suppression by regulating M1/M2 polarization, thus influencing the tumor-migration capacity and apoptosis. This could result in clinically applicable strategies to inhibit the formation of MPE by regulating the polarization of MPE macrophages., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2023 Xue-Bin Pei et al.)

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.)

IL-10, produced by a wide variety of cells, is a highly pleiotropic cytokine that plays a critical role in the control of immune responses. However, its regulatory activity in tumor immunity remains poorly understood. In this study, we report that IL-10 deficiency robustly suppressed the formation of malignant pleural effusion (MPE) and significantly enhanced miR-7116-5p expression in pleural CD4 + T cells. We demonstrated that miR-7116-5p suppressed IL-10-mediated MPE formation by inhibiting pleural vascular permeability as well as tumor angiogenesis and tumor growth. IL-10 promoted MPE formation by suppressing miR-7116-5p that enhances T H 1 response. We identified G protein-coupled receptor 55 (GPR55) as a potential target of miR-7116-5p, and miR-7116-5p promoted T H 1 cell function by downregulating GPR55. Moreover, GPR55 promoted MPE formation by inhibiting T H 1 cell expansion through the ERK phosphorylation pathway. These results uncover an IL-10-mediated pathway controlling T H 1 cells and demonstrate a central role for miR-7116-5p/GPR55/ERK signaling in the physiological regulation of IL-10-driven pro-malignant responses., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)