Targeted delivery of siRNA using transferrin-coupled lipoplexes specifically sensitizes CD71 high expressing malignant cells to antibody-mediated complement attack

摘要

The overexpression of membrane-bound complement regulatory proteins (mCRP; CD46, CD55, CD59) preventing opsonization and complement-dependent cytotox-icity (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.