每年皆有數百萬人因癌症而死亡，固癌症對於人類之健康為一大挑戰。免疫治療為癌症新穎之治療方法，其主要透過刺激我們自身免系統以攻擊腫瘤細胞。此免疫檢查點療法目前已徹底改變傳統癌症治療方式，且改變我們如何看待癌症。PD-1為一位於T細胞表面上表達之蛋白質，其配體 PD-L1則表達於癌細胞表面。它們類似CTLA-4與CD80/CD86之作用，可活化T細胞之抑制系統，但詳細機制不同。當PD-1 / PD-L1之間相互作用遭受阻斷之時，可導致耗盡之T細胞表型逆轉以及引發抗腫瘤之免疫反應。奈米微盤為直徑為8-16 nm自組雙層磷脂質之盤狀片段，其由兩條支架蛋白穩定於溶液中。可作為穩定且高度可溶之膜模擬物，其具有固定比例之磷脂質組成並可將親和標籤添加至支架蛋白上，因此奈米微盤於膜蛋白之生物物理學以及生物化學研究上為一具有吸引力之模型系統。適體為一可形成特異性三維結構以及具高特異性和親和性結合之標靶分子寡核苷酸。近期，適體已成為一類新型強大之配體，其具有診斷和治療應用之優越潛力。故開發標靶PD-L1之特異性適體為癌症患者提供新的癌症治療之選擇。於本研究中，我們使用過表達PD-L1之細胞株進行萃取膜蛋白，並將其膜蛋白包裹成奈米微盤，並使用適體庫與其奈米微盤進行篩選，並建立納米微盤指數富集系統平台（Nano-disc-SELEX），針對PD-L1篩選出具有高度專一性且具高親和力之適體。透過PCR以及即時聚合酶連鎖反應分析其專一性及親和能力。其結果顯示與控制組奈米微盤相比，我們發現PD-L1適體會優先與PD-L1奈米微盤結合證實其具有專一性，此外也對PD-L1奈米微盤具有高親合能力。將來，我們將測試其PD-L1適體於體內及體外之作用能力。期望本研究成果可作為新癌症免疫治療之藥物，提供患者治療新選擇以及希望此平台技術可供其餘類似膜蛋白適體篩選之參考，以增進生物醫學對於膜蛋白相關之適體研究。

In this study, we extracted the membrane proteins from PD-L1-Flag overexpression cells and assembled it in Nano-discs. PD-L1-Flag-assembed Nano-disc-based systematic evolution of ligands by exponential enrichment (Nano-disc-SELEX) was performed to screen DNA aptamers targeted PD-L1-Flag and then amplified products by PCR. We obtained four Aptamer and we determine their binding specificity. PD-L1-aptamers preferentially bound PD-L1-Flag-nanodisc compared with control Nano-disc. Furthermore, we analyzed the binding affinity by quantitative real time polymerase chain reaction detection and showed that PD-L1 aptamers candidates had high binding affinity to PD-L1-Flag-nanodiscs. With the present experimental results provide not only a powerful Nano-disc-SELEX system but also a reference for screening membrane protein-targeted aptamers which will apply in further cancer immunotherapy development.

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