The global incidence of melanoma is increasing. Mortality from melanoma is influenced primarily by metastasis in advanced stages of the disease. Current treatments are largely ineffective; thus, novel gene delivery approaches that target tumor-specific markers may be useful for the treatment of melanoma. Systemic administration of encapsulated RNA-interference plasmids targeted against tumor cells is a potential alternative therapy for cancer. Formulations of transferrin (Tf)-conjugated polyethylene glycol (PEG) liposomes loaded with short hairpin RNA (shRNA) against WT1 (Lip + RNAi + Tf), PEG liposomes loaded with shRNA against WT1 (Lip + RNAi), Tf-conjugated PEG liposomes loaded with pEGFP-N3 (Lip + GFP + Tf) and saline solution as negative control (untreated) were administered systemically to C57BL/6 mice implanted subcutaneously with a melanoma cell line. Tumor volume, body weight, tumor weight, survival and relative expression of WT1 were evaluated. No significant differences in net body weight were identified between groups. The tumor volume decreased from 7,871 mm3 (SD±2,087) in the untreated group to 5,981 mm3 (SD±2,099) in the Lip + RNAi + Tf group. The tumor weight was reduced, from 8.8 g (SD±0.30) in the untreated group to 5.5 g (SD±0.87) in the Lip + RNAi + Tf group. An increase of 37% in survival was also observed in the group treated with Lip + RNAi + Tf in comparison to the untreated group. Tumors treated with Lip + RNAi + Tf also showed a decrease in the mean relative expression of WT1 of 0.21 (SD±0.28) folds compared with 1.8 (SD±2.49) folds in untreated group, 1.34 (SD±0.43) folds in Lip + RNAi group and of 1.89 (SD±0.69) folds in Lip + GFP + Tf group. Systemic administration of transferrin-conjugated PEG liposomes loaded with shRNA against WT1 reduced WT1 expression and tumor size and increased survival.
Keywords: RNA interference; WT1; melanoma; transferrin-targeted liposome.