Increase of therapeutic effects by treating melanoma with targeted combinations of c-myc antisense and doxorubicin

Patients with advanced or metastatic melanoma have a very poor prognosis, due to the resistance of melanoma cells to conventional chemotherapy. We previously reported that coated cationic liposomes targeted with a monoclonal antibody against the disialoganglioside GD2 and containing c-myc antisense oligodeoxynucleotides (αGD2-CCL[c-myc-as]) induced partial tumor growth arrest in melanoma xenografts. Here we addressed the role of c-myc-asODN treatment in the susceptibility to doxorubicin (DXR) in human melanoma cells. Cytotoxicity studies revealed that growth of melanoma cells was inhibited to a greater extent by αGD2-CCL[c-myc-as] than by the corresponding non-targeted formulations or by free c-myc-as. Targeted c-myc-as sensitized cells to DXR, reducing the IC50 by approximately 10-fold. Scrambled ODNs had no effect on the IC50 of DXR. Compared to either treatment alone, combination of targeted c-myc-as and DXR resulted in earlier apoptosis and in cell death after 2 days of treatment. In vivo experiments revealed that liposomal formulations of c-myc-as and DXR, both targeted via GD2, led to the most pronounced delay in tumor growth when administered in a sequential manner. As a result, their combination translates into a statistically significant suppression of blood vessel density and an enhanced apoptosis, compared to all treatments given separately. Our data indicate the increasing cell sensitivity to DXR by c-myc-asODNs as a promising basis for developing novel anti-tumor strategy against advanced melanoma.