PM2.5引起的肿瘤新生血管形成和转移研究进展

 PM_2.5指直径≤2.5 μm 的颗粒物质，它很容易穿过呼吸道屏障，进入血液循环，可诱发肺癌等多种恶性肿瘤，已成为恶性肿瘤新的诱因。近年研究揭示，PM_2.5可刺激肿瘤细胞合成和分泌血管内皮生长因子（VEGF），促进血管内皮细胞介导的肿瘤血管新生；并可激活肿瘤细胞，使其通过血管生成拟态直接形成肿瘤血管；还能使肿瘤干细胞向肿瘤内皮细胞转化，促进肿瘤新生血管形成。此外，PM_2.5可促进肿瘤细胞及其他多种细胞分泌趋化因子和白细胞介素，招募骨髓和血液中白细胞进入肿瘤组织，诱发局部慢性炎症反应，诱导上皮细胞-间充质细胞转化（EMT）的发生，增加肿瘤细胞干性、迁移和转移能力；还可破坏血管稳态，增加血管通透性，为肿瘤细胞的转移打开方便之门。PM_2.5在肿瘤的新生血管形成和转移中起了重要作用，然而，至今对其作用机制知之甚少。因此，进一步深入研究PM_2.5诱导的肿瘤新生血管形成及转移机制，能为PM_2.5引起的恶性肿瘤防治提供可靠的理论依据和新的应对策略。

Progress in PM2.5-caused Tumor Neovascularization and Metastasis

PM_2.5 refers to the particles with 2.5 μm or less in diameter, which can easily go through the barrier of respiratory track and enter the blood circulation. PM_2.5 can induce various malignant tumors including lung cancer, and it has become a new cause of cancers. Recent studies have revealed that PM_2.5 may stimulate synthesis and secretion of vascular endothelial growth factor (VEGF) and various vascular growth factors, promote vascular endothelial cell-mediated tumor angiogenesis, activate tumor cells and allow cancer cells to directly firm tumor vasculature through vasculogenic mimicry, and induce the trans-differentiation of cancer stem cells into tumor endothelial cells, enhancing tumor neovascularization. In addition, PM_2.5 can escalate tumor cells and many other cells to secrete chemokines and cytokines which recruit bone marrow and blood while cells into tumor tissue, and bring about local chronic inflammation. PM_2.5 may also induce epithelial-mesenchymal transition (EMT), resulting in an increment of cancer cell stemness, migration, and metastasis. Furthermore, PM_2.5 may damage vascular homeostasis system, increase vascular permeation, opening a door for tumor cell metastasis. Taken together, PM_2.5 plays important roles in tumor neovascularization and metastasis; whereas, its mechanisms are enigmatic. Thus, more extensive study of the mechanisms of PM_2.5-induced tumor neovascularization and metastasis will provide a reliable theory, strategy, and new approach for prevention and treatment of PM_2.5-caused malignant tumors in the future.