背景:免疫逃逸是乳腺癌(BC)预后不良的原因之一。谷氨酰胺-果糖-6-磷酸转氨酶1(GFPT1)是己糖胺生物合成途径(HBP)的第一种限速酶,对于BC的进展至关重要。然而,GFPT1在BC免疫逃逸中的感化机制尚不清晰。
方法:首先,通过starbase分析BC中GFPT1的水平,并通过qRT-PCR检测BC组织中GFPT1的表达,蛋白质印迹和IHC。然后,通过蛋白质印迹检测O-GlcNAc水平。此后,应用Co-IP检测GFPT1和PD-L1之间的关系。最后,构建小鼠模型进行体内验证.
结果:首先,我们发现GFPT1在BC中明显增强。敲低或引入GFPT1相应地降解和升高细胞中的O-GlcNAc水平。进一步的研究表明,GFPT1和PD-L1之间存在着相互关系。机械上,我们公开了GFPT1通过O-糖基化增强PD-L1蛋白的稳定性。更有趣的是,GFPT1通过上调O-糖基化修饰的PD-L1加速BC细胞免疫逃逸。在体内,GFPT1的沉默通过降低PD-L1水平来减弱BC细胞的免疫逃逸。
结论:GFPT1通过O-糖基化修饰的PD-L1促进BC进展和免疫逃逸。GFPT1可能是BC治疗的潜在靶点。
BACKGROUND: Immune escape is one of the causes of poor prognosis in breast cancer (BC). Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) is the first speed-limiting enzyme of the hexosamine biosynthesis pathway (HBP) and is essential for the progression of BC. Nevertheless, the mechanism of the influence of GFPT1 in BC immune escape is not clear.
METHODS: First, the level of GFPT1 in BC was analyzed by starbase, and GFPT1 expression in BC tissues was measured by qRT-PCR, western blot and IHC. Then, the O-GlcNAc levels were detected by western blot. Thereafter, Co-IP was applied to examine the relationship between GFPT1 and PD-L1. At last, a mouse model was constructed for validation in vivo.
RESULTS: Firstly, we discovered that GFPT1 was obviously strengthened in BC. Knockdown or introduction of GFPT1 correspondingly degraded and elevated O-GlcNAc levels in cells. Further researches revealed that there was a reciprocal relationship between GFPT1 and PD-L1. Mechanistically, we disclosed that GFPT1 enhanced PD-L1 protein stability through O-glycosylation. More interestingly, GFPT1 accelerated BC cell immune escape via upregulation of O-glycosylation-modified PD-L1. In vivo, silencing of GFPT1 attenuated immune escape of BC cells by reducing PD-L1 levels.
CONCLUSIONS: GFPT1 promoted BC progression and immune escape via O-glycosylation-modified PD-L1. GFPT1 may be a potential target for BC therapy.