Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.
Cancer Immunol Res. 2018 Aug;6(8):921-929. doi: 10.1158/2326-6066.CIR-17-0316. Epub 2018 Jun 5.
Programmed death ligand 1 (PD-L1)-mediated immunosuppression regulates peripheral tolerance and is often co-opted by tumors to evade immune attack. PD-L1 binds to PD-1 but also binds to B7-1 (CD80) to regulate T-cell function. The binding interaction of PD-L1 with B7-1 and its functional role need further investigation to understand differences between PD-1 and PD-L1 tumor immunotherapy. We examined the molecular orientation of PD-L1 binding to B7-1 using cell-to-cell binding assays, ELISA, and flow cytometry. As expected, PD-L1-transfected cells bound to PD-1-transfected cells, and B7-1 cells bound to CD28 or CTLA-4-transfected cells; however, PD-L1 cells did not bind to B7-1 cells. By ELISA and flow cytometry with purified proteins, we found PD-L1 and B7-1 had a strong binding interaction only when PD-L1 was flexible. Soluble PD-1 and B7-1 competed for binding to PD-L1. Binding of native PD-L1 and B7-1 on the same cell surface was demonstrated with NanoBiT proximity assays. Thus, PD-L1-B7-1 interaction can occur on the same cell but not between two cells, which suggests a model in which PD-L1 can bend via its 11-amino acid, flexible stalk to bind to B7-1 , in a manner that can competitively block the binding of PD-L1 to PD-1 or of B7-1 to CD28. This binding orientation emphasizes the functional importance of coexpression of PD-L1 and B7-1 on the same cell. We found such coexpression on tumor-infiltrating myeloid cells. Our findings may help better utilize these pathways in cancer immunotherapy. .
程序性死亡配体 1（PD-L1）介导的免疫抑制调节外周耐受，并且经常被肿瘤细胞利用来逃避免疫攻击。PD-L1 与 PD-1 结合，但也与 B7-1（CD80）结合以调节 T 细胞功能。PD-L1 与 B7-1 的结合相互作用及其功能作用需要进一步研究，以了解 PD-1 和 PD-L1 肿瘤免疫疗法之间的差异。我们使用细胞间结合测定法、ELISA 和流式细胞术检查了 PD-L1 与 B7-1 的分子取向。正如预期的那样，PD-L1 转染的细胞与 PD-1 转染的细胞结合，B7-1 细胞与 CD28 或 CTLA-4 转染的细胞结合；然而，PD-L1 细胞不与 B7-1 细胞结合。通过使用纯化蛋白的 ELISA 和流式细胞术，我们发现只有当 PD-L1 具有柔韧性时，PD-L1 和 B7-1 才有很强的结合相互作用。可溶性 PD-1 和 B7-1 竞争与 PD-L1 结合。通过 NanoBiT 接近测定法证明了天然 PD-L1 和 B7-1 在同一细胞表面上的结合。因此，PD-L1-B7-1 相互作用可以在同一细胞上发生，但不能在两个细胞之间发生，这表明 PD-L1 可以通过其 11 个氨基酸的柔性茎部弯曲以与 B7-1 结合的模型，以竞争性方式阻断 PD-L1 与 PD-1 或 B7-1 与 CD28 的结合。这种结合取向强调了 PD-L1 和 B7-1 在同一细胞上共表达的功能重要性。我们在肿瘤浸润性髓样细胞上发现了这种共表达。我们的发现可能有助于更好地利用这些途径进行癌症免疫治疗。
