Key Points Myo9b deficiency in tumor cells and host mice both suppress the development of MPE. TSAd expression mediated by Myo9b associates with TH1/TH17 cell differentiation. Myo9b mediates MPE suppression by TSAd-dependent TH1/TH17 cell response regulation. Visual Abstract 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 TH1 cells and increasing TH17 cells. CD4+ naive T cells isolated from Myo9b−/− mouse spleens exhibited less TH1 cell differentiation and more TH17 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 TH1 cell differentiation and more TH17 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 TH1 cells, and increased TH17 cells in MPE in vivo. Taken together, Myo9b deficiency suppresses MPE development not only by suppressing pleural cancer metastasis but also by regulating TH1/TH17 cell response via a TSAd-dependent pathway. This work suggests Myo9b and TSAd as novel candidates for future basic and clinical investigations of cancer.

中文翻译：

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TSAd 通过调节 TH1/TH17 细胞反应在 Myo9b 介导的恶性胸腔积液抑制中发挥重要作用

关键点 肿瘤细胞和宿主小鼠中的 Myo9b 缺陷均抑制 MPE 的发展。由 Myo9b 介导的 TSAd 表达与 TH1/TH17 细胞分化相关。Myo9b 通过 TSAd 依赖性 TH1/TH17 细胞反应调节介导 MPE 抑制。视觉摘要 新出现的证据表明，Myo9b 是一种癌症转移相关蛋白，在多种免疫相关疾病中发挥作用。然而，目前尚不清楚 Myo9b 是否以及如何在恶性胸腔积液 (MPE) 中起作用。在这项研究中，我们的数据显示 Myo9b 表达水平与肺癌胸膜转移相关，并且来自患者或小鼠的 MPE 中的有核细胞表达的 Myo9b 水平低于相应血液中的水平。癌细胞中的 Myo9b 缺陷通过抑制迁移来抑制 MPE 的发展。小鼠中的 Myo9b 缺陷通过减少 TH1 细胞和增加 TH17 细胞来抑制 MPE 的发展。从 Myo9b-/- 小鼠脾脏中分离的 CD4+ 幼稚 T 细胞在体外表现出较少的 TH1 细胞分化和较多的 TH17 细胞分化。有核细胞的 mRNA 测序显示，T 细胞特异性衔接蛋白 (TSAd) 在 Myo9b-/- 小鼠 MPE 中下调，并且在 Myo9b-/- 组中发现 TSAd 启动子区域中的 H3K27me3 标记富集。从用 TSAd 特异性小干扰 RNA (siRNA) 转染的野生型小鼠脾脏纯化的幼稚 T 细胞也显示出比 siRNA 对照组更少的 TH1 细胞分化和更多的 TH17 细胞分化。此外，使用胆固醇偶联的 TSAd 特异性 siRNA 在小鼠中下调 TSAd 抑制了 MPE 的发展，减少了 TH1 细胞，并在体内增加 MPE 中的 TH17 细胞。总之，Myo9b 缺陷不仅通过抑制胸膜癌转移，而且通过 TSAd 依赖性途径调节 TH1/TH17 细胞反应来抑制 MPE 的发展。这项工作表明 Myo9b 和 TSAd 是未来癌症基础和临床研究的新候选者。