Doxorubicin-Loaded Platelets Conjugated with Anti-CD22 Mabs: A Novel Targeted Delivery System for B-Cell Lymphoma Treatment with Cardiac Avoidance

Objective: B-cell lymphoma accounts for approximately 85% of all adult non-Hodgkin's lymphoma cases. Chemotherapy remains the first-line treatment for B-cell lymphoma. However, cytotoxic drugs cause various adverse reactions in normal tissues and cells, thus limiting the applied dosage of chemotherapeutic agents and hampering their effects on tumor cells. Therefore, crucial requirements for effective cancer treatment include tumor-specific drug accumulation and the protection of normal tissues from cytotoxic effects.

Methods: In this study, we developed a novel drug delivery system for lymphoma treatment: doxorubicin-loaded platelets that were conjugated with anti-CD22 monoclonal antibodies (mAbs) (DOX-platelet-CD22). Platelets are bio- and immune-compatible drug carriers that can prolong the circulation time of drugs. Anti-CD22 mAb-labeled platelets can precisely deliver doxorubicin to tumor cells. The conjugation of anti-CD22 mAbs and encapsulation of doxorubicin in platelets were confirmed using fluorescence microscopy. Scanning electron microscopy and platelet aggregation assay were used to analyze the potential changes in platelet morphology and function. The cytotoxicity of DOX-platelet-CD22 on myocardial cell was evaluated by CCK-8 assay and its anti-tumour effects were determined by CCK-8 assay, flow cytometry and DAPI staining. The possible mechanism was further investigated by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting.

Results: Anti-CD22 mAbs were successfully coupled to platelets loaded with doxorubicin with high drug loading and encapsulation efficiency. No significant changes in morphology and function were observed between native platelets and DOX-platelet-CD22. Further, doxorubicin in DOX-platelet-CD22 was released most rapidly in an acidic condition. In Raji cells treated with DOX-platelet-CD22, the intracellular DOX concentration significantly increased, the cell viability remarkably decreased and apoptosis was obviously induced. These results indicate that platelets conjugated anti-CD22 mAbs can improve the therapeutic effects of doxorubicin. Moreover, the viability of myocardial cells treated with DOX-platelet-CD22 were significantly increased compared with those treated with free doxorubicin, demonstrating that DOX-platelet-CD22 can reduce cardiotoxicity caused by doxorubicin. Compared with other groups, the expression levels of Bax, caspase-3, and caspase-9 were notably upregulated while the Bcl-2 expression was downregulated in Raji cells treated with DOX-platelet-CD22. These findings indicate that DOX-platelet-CD22 can improve the antitumor activity of doxorubicin through bcl-2/caspase-mediated apoptosis pathway.

Conclusion: DOX-platelet-CD22 drug delivery system enhances the anti-tumor effects and reduces the adverse effects of doxorubicin, thus proposing a promising option for B-cell lymphoma treatment.