Chimeric Antigen Receptor-Engineered Exosome As a Drug Delivery System in Mantle Cell Lymphoma

Background: Mantle cell lymphoma (MCL) is an aggressive B cell lymphoma with short median survival, ranging from 3 to 5 years. Immunochemotherapy is currently the standard approach for treating MCL patients. For optimization of the treatment, an ideal drug delivery system would improve the biological effectiveness and reduce the treatment-related toxicity. Exosome are small vesicles with 30-150 nm in diameter, released from various types of cells. It serves as a messenger transmitter between cells and exhibits a large potential for drug delivery. In current study, we developed a chimeric antigen receptor engineered exosome (CAR-Exo) consisting of membrane fused anti-CD19 scFv. We sought to use this exosome as a drug delivery system for targeting MCL cell in vitro and in vivo .

Methods and Results: The displayed vector (pIRSE-II) was constructed by fusing anti-CD 19 scFv with CD63. HEK 293-T cell was transfected with empty vector (Control) or pIRSE-II by lipo2000. Real time-PCR was employed to confirm the expression of anti-CD19 scFv in pIRSE-II transfected cell. Comparing with the control group, anti-CD19 scFv mRNA was overexpressed (> 10⁵ times) in the pIRSE-II transfected cell line. CAR-Exo was isolated by using exosome extraction reagent. After CAR-Exo was incubated with Mino and Jeko-1 cell lines, targeting efficiency was tested by flow cytometry. Significant peak shift was observed in both Mino (about 95%) and Jeko-1 (about 90%) cell lines, indicating that CAR-Exo exhibited high targeting ability (5 times for Mino and 6 times for Jeko-1, compared to controls). Next, we used CAR-Exo to package doxorubicin and treated MCL cells. CCK8 assay demonstrated increased cytotoxicity in MCL cells, compared to those cells treated with free doxorubicin alone.

Conclusion: In this study, we engineered CD19 targeting CAR-exosome which showed high affinity to B-cells and doxorubicin-loaded CAR-Exo exhibited increased toxicity to the MCL cells.