二甲双胍通过下调乳腺癌细胞分泌的PlGF抑制TAM诱导血管生成的机制研究

Anti-VEGF therapy improves prognosis of cancer patients via suppressing angiogenesis, but is ineffective in treating breast cancer. Our previously published article demonstrated the effectiveness of metformin in anti-angiogenesis of breast cancer, indicating that metformin has potential clinical value in avoiding the anti-VEGF resistance of breast cancer, but the exact mechanism remains an enigma. There is evidence indicating that placental growth factor (PlGF) induces VEGF-independent angiogenesis by regulating the polarization of tumor-associated macrophage (TAM) via an autocrine mechanism. In fact, breast cancer cells are capable of excessively secreting PlGF. So, can the PlGF secreted outside cells also have the potential to regulate TAM polarization? Our previous study has shown that metformin significantly reduced the secretion level of breast cancer cell-derived PlGF and affected TAM polarization occurred in cancer tissue. On the basis of the background and evidences mentioned above, we therefore hypothesis that the mechanism of paracrine PlGF-mediated regulation of TAM polarization plays a critical role in metformin-induced anti-angiogenic effects on breast cancer. Molecular biology techniques and transplanted tumor models will be utilized to elucidate the mechanisms underlying metformin-induced anti-angiogenesis by inhibiting paracrine PlGF-medaited regulation of TAM polarization, and to provide evidences for supporting the clinical application of metformin as a novel anti-angiogenesis drug for breast cancer.

抗VEGF治疗通过抑制血管生成改善癌症患者预后，但对乳腺癌却疗效不佳。课题组已发表文章证实了二甲双胍的有效抗乳腺癌血管生成作用，提示二甲双胍能规避乳腺癌产生的抗VEGF抵抗，但具体机制不详。研究表明胎盘生长因子(PlGF)可通过自分泌机制调节肿瘤相关巨噬细胞(TAM)极化，从而诱导非VEGF依赖的血管生成。事实上，乳腺癌细胞可分泌过量的PlGF，那么，这些被分泌到癌细胞外的PlGF是否也能调节TAM极化？课题组前期研究发现二甲双胍能显著降低乳腺癌PlGF的分泌水平并影响癌组织内TAM的极化。基于上述背景和结果，我们推测：二甲双胍可能通过抑制旁分泌PlGF对TAM极化的调节作用介导抗乳腺癌血管生成。我们将利用分子生物学技术及移植瘤动物模型，探索二甲双胍通过靶向乳腺癌PlGF旁分泌信号对TAM极化诱导的肿瘤血管生成的影响，为二甲双胍以新型抗乳腺癌血管生成药物应用于临床提供理论依据。

血管生成是包括乳腺癌在内的多种肿瘤的重要特征，通过诱导血管生成肿瘤细胞促进自身的生长及进展。研究表明肿瘤微环境中TAMs向M2极化是促进血管生成的一种潜在机制，并介导抗血管生成抵抗。据报道，二甲双胍具有显著的抑制肿瘤血管生成的作用，但其潜在的分子调控机制仍不十分清楚。本研究发现：1）二甲双胍带来的乳腺癌生长抑制与其介导的抗血管生成作用密切相关；2）化学性敲除小鼠TAMs抵消了二甲双胍介导的抗血管生成作用；3）二甲双胍通过转录调节机制抑制乳腺癌4T1细胞的分泌水平；4）在敲低4T1乳腺癌细胞PlGF后，乳腺癌内M2型TAMs的百分比减少，同时M1型TAMs的百分比增加。上述研究结果说明：二甲双胍通过下调乳腺癌细胞源性 PlGF 的旁分泌抑制了TAM向促血管生成的M2型极化，最终发挥有效抗乳腺癌血管生成作用，并为二甲双胍以新型抗乳腺癌血管生成药物应用于临床提供理论依据。相关研究成果以论文的形式发表SCI论文5篇及核心论文2篇，研究期间指导、博士1名和硕士生1名。