Curative (R0) resection is only one step in curing cancer, and radiotherapy may play a beneficial role in controlling locoregional residual tumour. MVI could be a useful indicator of when systemic adjuvant therapy should be implemented to prevent liver metastasis after R0 resection, although no effective systemic treatment has yet been developed.

We demonstrated previously that dendritic cell (DC)-based vaccines could mediate a specific and long-lasting antitumor immune response during early lymphoid reconstitution after lethal irradiation and bone marrow transplant. The purpose of this current study was to examine the potential therapeutic efficacy of DC-based vaccines in combination with sublethal lymphodepletion and T-cell transfer. In an aggressive model of melanoma, treatment with the combination of 200 mg/kg cyclophosphamide (Cy) and 100 mg/kg fludarabine (Flu) led to a lymphopenic state lasting approximately 14 days, but had no effect on the growth of an established M05 melanoma. Addition of ovalbumin (OVA) peptide-pulsed DC-based immunization resulted in a delay in tumor growth but did not enhance overall survival in this model. To improve treatment, adoptively transferred naive T cells were added. After induction of lymphopenia with Cy and Flu, transferred T cells demonstrated an activated memory phenotype including high expression of CD44 and low expression of CD62L. Induction of lymphopenia with Cy and Flu in combination with adoptive transfer of naive T cells and OVA peptide-pulsed DCs immunization led to an enhancement in the number of OVA specific, CD8 T cells that demonstrated specific cytotoxic activity, proliferation, and interferon-gamma production in response to the OVA expressing M05 melanoma. This combination therapy also led to tumor regression and enhanced survival in mice bearing M05 melanoma.