Su Yu-Ting, Butler Madison, Zhang Meili, Zhang Wei, Song Hua, Hwang Lee, Tran Andy D, Bash Ryan E, Schorzman Allison N, Pang Ying, Yu Guangyang, Zamboni William C, Wang Xiaodong, Frye Stephen V, Miller Christopher Ryan, Maric Dragan, Terabe Masaki, Gilbert Mark R, Earp Iii Henry Shelton, Wu Jing
Neuro-Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA.
Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA.
Neurooncol Adv. 2020 Jun 3;2(1):vdaa065. doi: 10.1093/noajnl/vdaa065. eCollection 2020 Jan-Dec.
Glioblastoma-associated macrophages and microglia (GAMs) are the predominant immune cells in the tumor microenvironment. Activation of MerTK, a receptor tyrosine kinase, polarizes GAMs to an immunosuppressive phenotype, promoting tumor growth. Here, the role of MerTK inhibition in the glioblastoma microenvironment is investigated in vitro and in vivo.
Effects of MRX-2843 in glioblastoma microenvironment regulation were determined in vitro by cell viability, cytokine array, in vitro tube formation, Western blotting, and wound healing assays. A syngeneic GL261 orthotopic glioblastoma mouse model was used to evaluate the survival benefit of MRX-2843 treatment. Multiplex fluorescent immunohistochemistry was used to evaluate the expression of CD206, an anti-inflammatory marker on GAMs, and angiogenesis in murine brain tumor tissues.
MRX-2843 inhibited cell growth and induced apoptosis in human glioblastoma cells and decreased protein expression of phosphorylated MerTK, AKT, and ERK, which are essential for cell survival signaling. Interleukin-8 and C-C motif chemokine ligand 2, the pro-glioma and pro-angiogenic cytokines, were decreased by MRX-2843. Decreased vascular formation and numbers of immunosuppressive (CD206+) GAMs were observed following MRX-2843 treatment in vivo, suggesting that in addition to alleviating immunosuppression, MRX-2843 also inhibits neoangiogenesis in the glioma microenvironment. These results were supported by a prolonged survival in the syngeneic mouse orthotopic GL261 glioblastoma model following MRX-2843 treatment.
Our findings suggest that MRX-2843 has a therapeutic benefit via promoting GAM polarization away from immunosuppressive condition, inhibiting neoangiogenesis in the glioblastoma microenvironment and inducing tumor cell death.
胶质母细胞瘤相关巨噬细胞和小胶质细胞（GAMs）是肿瘤微环境中的主要免疫细胞。受体酪氨酸激酶MerTK的激活使GAMs极化至免疫抑制表型，促进肿瘤生长。在此，研究了MerTK抑制在胶质母细胞瘤微环境中的体内外作用。
通过细胞活力、细胞因子阵列、体外成管、蛋白质印迹和伤口愈合试验，在体外确定MRX-2843对胶质母细胞瘤微环境调节的作用。使用同基因GL261原位胶质母细胞瘤小鼠模型评估MRX-2843治疗的生存获益。采用多重荧光免疫组织化学法评估GAMs上抗炎标志物CD206的表达以及小鼠脑肿瘤组织中的血管生成。
MRX-2843抑制人胶质母细胞瘤细胞的生长并诱导其凋亡，降低磷酸化MerTK、AKT和ERK的蛋白表达，这些蛋白对细胞存活信号传导至关重要。MRX-2843降低了促胶质瘤和促血管生成细胞因子白细胞介素-8和C-C基序趋化因子配体2的水平。在体内，MRX-2843治疗后观察到血管形成减少以及免疫抑制性（CD206+）GAMs数量减少，这表明MRX-2843除了减轻免疫抑制外，还抑制胶质瘤微环境中的新生血管生成。MRX-2843治疗后同基因小鼠原位GL261胶质母细胞瘤模型的生存期延长，支持了这些结果。
我们的研究结果表明，MRX-2843通过促进GAMs从免疫抑制状态极化、抑制胶质母细胞瘤微环境中的新生血管生成以及诱导肿瘤细胞死亡而具有治疗益处。
