Inhibition of PAK2 in endothelial cells suppresses tumor angiogenesis and promotes immune sensitization through CXCL10

Tumor angiogenesis is driven by pro-angiogenic factors and results in a disorganized tumor vasculature that limits effective perfusion and immune infiltration. The p21-activated kinase 2 (PAK2) regulates endothelial cell (EC) migration, an essential step of angiogenesis, yet its role in tumor angiogenesis remains ill-defined. Here, we show that endothelial-specific deletion of PAK2 in orthotopic tumor mouse models markedly reduces tumor size and angiogenesis. Loss of endothelial PAK2 also normalizes the remaining tumor vasculature and promotes infiltration of dendritic and NK cells. Mechanistically, PAK2 regulates chemokine expression, notably CXCL10. PAK2 depletion enhances CXCL10 secretion from ECs, and CXCL10 expression is required for the inhibitory effects of PAK2 silencing on EC spouting. Moreover, CXCL10 neutralization in mice reverses the vascular and immune changes induced by endothelial PAK2 deletion. Together, these findings identify endothelial PAK2 as a potential target to limit tumor angiogenesis and reprogram ECs to promote immune infiltration through CXCL10 signaling. Overall design: RNA-seq of CT-PAK2EC and KO-PAK2EC LLC tumors in mice at day 18 of tumor growth. RNA-seq of siCT and siPAK2-transfected HUVEC, and RNA-seq of siCT, siPAK2, siCXCL10 and siPAK2-siCXCL10 transfected HUVEC

肿瘤血管生成由促血管生成因子驱动，可形成紊乱的肿瘤脉管系统，进而损害有效灌注并抑制免疫浸润。p21激活激酶2（p21-activated kinase 2, PAK2）可调控内皮细胞（endothelial cell, EC）的迁移——这是血管生成的关键环节，但其在肿瘤血管生成中的作用仍未明确。本研究发现，在原位肿瘤小鼠模型中特异性敲除内皮细胞中的PAK2，可显著缩小肿瘤体积并抑制肿瘤血管生成。内皮细胞PAK2缺失还可使残留的肿瘤脉管系统趋于正常化，并促进树突状细胞与NK细胞的浸润。从机制层面来看，PAK2可调控趋化因子的表达，尤其是CXCL10。敲低PAK2可增强内皮细胞的CXCL10分泌，而CXCL10的表达是PAK2沉默抑制内皮细胞出芽所必需的。此外，在小鼠体内中和CXCL10可逆转内皮细胞PAK2缺失诱导的脉管系统与免疫细胞浸润变化。综上，本研究证实内皮细胞PAK2可作为潜在靶点，通过调控CXCL10信号通路限制肿瘤血管生成，并重塑内皮细胞以促进免疫浸润。实验设计概述：对肿瘤生长至第18天的小鼠体内的CT-PAK2EC与KO-PAK2EC Lewis肺癌（Lewis lung carcinoma, LLC）肿瘤进行RNA测序；对转染阴性对照小干扰RNA（siCT）与靶向PAK2的小干扰RNA（siPAK2）的人脐静脉内皮细胞（human umbilical vein endothelial cell, HUVEC）进行RNA测序；同时对转染siCT、siPAK2、siCXCL10以及共转染siPAK2与siCXCL10的HUVEC进行RNA测序。