CD20 Antibody-Conjugated Immunoliposomes for Targeted Chemotherapy of Melanoma Cancer Initiating Cells

Cancer initiating cells (CIC) are tumorigenic cancer cells that have properties similar to normal stem cells. CD20 is a phenotype of melanoma CIC that is responsible for melanoma drug resistance. Vincristine (VCR) is commonly used in melanoma therapy; however, it has been found ineffective against CIC. To target CD20+ melanoma CIC, we prepared VCR-containing immunoliposomes that were conjugated to CD20 antibodies (VCR-Lip-CD20). The drug release profile and the antibody-mediated targeting of the immunoliposomes were optimized to target CD20+ melanoma CIC. The immunoliposomes had desirable particle size (163 nm), drug encapsulation efficiency (91.8%), and drug release profile. We demonstrated that these immunoliposomes could successfully target more than 55% of CD20+ Chinese Hamster Ovary cells (CHO-CD20) even when the CHO-CD20 cells accounted for only 0.1% of a mixed population of CHO-CD20 and CHO cells. After treating WM266-4 melanoma mammospheres for 96 h, the ICo values of the drug delivered in VCR-Lip-CD20, VCR-Lip (VCR liposomes), and VCR were found to be 53.42, 98.99, and 99.09 μg/mL, respectively, suggesting that VCR-Lip-CD20 was 1.85 times more effective than VCR-Lip and VCR. VCR-Lip-CD20 could almost completely remove the tumorigenic ability of WM266-4 mammospheres in vivo, and showed the best therapeutic effect in WM266-4 melanoma xenograft mice. Significantly, VCR-Lip-CD20 could selectively kill CD20+ melanoma CIC in populations of WM266-4 cells both in vitro and in vivo. We demonstrated that VCR-Lip-CD20 has the potential to efficiently target and kill CD20+ melanoma CIC.