Han Xiaolu, Bryson Paul D, Zhao Yifan, Cinay Gunce E, Li Si, Guo Yunfei, Siriwon Natnaree, Wang Pin
Genetic, Molecular & Cellular Biology Program, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA.
Mork Family Department of Chemical Engineering and Materials Science, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA.
Mol Ther. 2017 Jan 4;25(1):274-284. doi: 10.1016/j.ymthe.2016.10.011.
Adoptive cellular therapy based on chimeric antigen receptor (CAR)-engineered T (CAR-T) cells is a powerful form of cancer immunotherapy. CAR-T cells can be redirected to specifically recognize tumor-associated antigens (TAAs) and induce high levels of antitumor activity. However, they may also display "on-target off-tumor" toxicities, resulting from low-level expression of TAAs in healthy tissues. These adverse effects have raised considerable safety concerns and limited the clinical application of this otherwise promising therapeutic modality. To minimize such side effects, we have designed an epidermal growth factor receptor (EGFR)-specific masked CAR (mCAR), which consists of a masking peptide that blocks the antigen-binding site and a protease-sensitive linker. Proteases commonly active in the tumor microenvironment can cleave the linker and disengage the masking peptide, thereby enabling CAR-T cells to recognize target antigens only at the tumor site. In vitro mCAR showed dramatically reduced antigen binding and antigen-specific activation in the absence of proteases, but normal levels of binding and activity upon treatment with certain proteases. Masked CAR-T cells also showed antitumor efficacy in vivo comparable to that of unmasked CAR. Our study demonstrates the feasibility of improving the safety profile of conventional CARs and may also inspire future design of CAR molecules targeting broadly expressed TAAs.
基于嵌合抗原受体（CAR）工程化T细胞（CAR-T）的过继性细胞疗法是一种强大的癌症免疫疗法。CAR-T细胞可被重定向以特异性识别肿瘤相关抗原（TAA）并诱导高水平的抗肿瘤活性。然而，由于健康组织中TAA的低水平表达，它们也可能表现出“靶向非肿瘤”毒性。这些不良反应引发了相当大的安全担忧，并限制了这种原本很有前景的治疗方式的临床应用。为了尽量减少此类副作用，我们设计了一种表皮生长因子受体（EGFR）特异性的掩蔽CAR（mCAR），它由一个阻断抗原结合位点的掩蔽肽和一个蛋白酶敏感连接子组成。通常在肿瘤微环境中活跃的蛋白酶可切割连接子并使掩蔽肽脱离，从而使CAR-T细胞仅在肿瘤部位识别靶抗原。在体外，mCAR在没有蛋白酶的情况下显示出显著降低的抗原结合和抗原特异性激活，但在用某些蛋白酶处理后，其结合和活性水平正常。掩蔽CAR-T细胞在体内也显示出与未掩蔽CAR相当的抗肿瘤功效。我们的研究证明了改善传统CAR安全性的可行性，也可能为未来靶向广泛表达的TAA的CAR分子设计提供灵感。
