Institute of Immunology, University of Heidelberg, Germany, Im Neuenheimer Feld 305, 69120, Heidelberg, Germany.
Target Oncol. 2015 Sep;10(3):405-13. doi: 10.1007/s11523-014-0345-6. Epub 2014 Nov 15.
The overexpression of membrane-bound complement regulatory proteins (mCRP; CD46, CD55, CD59) preventing opsonization and complement-dependent cytotoxicity (CDC) is considered a major barrier for successful antibody-based cancer immunotherapy. To avoid a potential deleterious effect of mCRP neutralization on normal tissue cells, complement regulation has to be selectively targeted to the malignant cells. In this study, anti-mCRP small interfering RNAs (siRNAs) were encapsulated in transferrin-coupled lipoplexes for the specific delivery to transferrin receptor CD71(high) expressing BT474, DU145, and SW480 as well as corresponding CD71-knockdown (CD71(low)) tumor cells. Targeted delivery with transferrin-siRNA-lipoplexes became possible by charge neutralization and resulted in efficient silencing of all three mCRPs up to 90%, which is dependent on their CD71 expression. The mCRP knockdown led to a significant increase of CDC on CD71(high) tumor cells by 68% in BT474, 58% in DU145, and 40% in SW480 cells but only slightly increased on CD71(low) cells. Downregulation of CD46 and CD55 significantly increased C3 opsonization only on CD71(high) tumor cells. Our results demonstrate for the first time that by specific delivery of anti-mCRP siRNA through transferrin receptor, complement regulation can be selectively neutralized, allowing specific antibody-mediated killing of tumor cells without affecting healthy bystander cells, which appears to be a suited strategy to improve antibody-based cancer immunotherapy.
膜结合补体调控蛋白（mCRP；CD46、CD55、CD59）的过度表达可防止调理作用和补体依赖的细胞毒性（CDC），被认为是抗体癌症免疫治疗成功的主要障碍。为避免 mCRP 中和对正常组织细胞的潜在有害影响，补体调控必须靶向恶性细胞。在这项研究中，抗 mCRP 小干扰 RNA（siRNA）被包裹在转铁蛋白偶联的脂质体中，用于特异性递送至转铁蛋白受体 CD71（高）表达的 BT474、DU145 和 SW480 以及相应的 CD71 敲低（CD71（低））肿瘤细胞。通过电荷中和实现了转铁蛋白-siRNA-脂质体的靶向递送，并导致所有三种 mCRP 的有效沉默，高达 90%，这依赖于它们的 CD71 表达。mCRP 敲低导致 CD71（高）肿瘤细胞上的 CDC 显著增加，BT474 增加 68%，DU145 增加 58%，SW480 增加 40%，而 CD71（低）细胞仅略有增加。CD46 和 CD55 的下调仅显著增加 CD71（高）肿瘤细胞上的 C3 调理作用。我们的研究结果首次表明，通过转铁蛋白受体特异性递送抗 mCRP siRNA，可以选择性地中和补体调控，从而允许特异性抗体介导的杀伤肿瘤细胞，而不影响健康的旁观者细胞，这似乎是一种改善抗体癌症免疫治疗的合适策略。
