Dendritic cell (DC)-based vaccines are being intensively investigated for the treatment of a variety of human neoplasms. However, little attention has until now been paid to the use of DC-based vaccines for immunotherapy of tumour residua after surgery. In this communication, an animal model mimicking human HPV16-associated neoplasms was employed to examine the effect of DC-based vaccines for the treatment of surgical minimal residual tumour disease. Mice were subcutaneously inoculated with syngeneic TC-1 tumour cells of HPV16 origin. When the tumours reached approximately 1 cm in diameter, they were surgically removed and the operated mice were injected into the site of the operation with bone marrow-derived DC, which were either pulsed with TC-1 cell lysates or co-cultured with irradiated TC-1 cells. It has been found that the growth of TC-1 tumour recurrences in the mice treated with these vaccines was substantially suppressed, as compared to the operated-only controls. The phenotypic analysis of the spleen cells has shown that the percentage of CD3+ cells was diminished in the operated-only and vaccinated mice carrying recurrent tumours, in comparison with healthy control mice and with operated tumour-free mice. Moreover, accumulation of immature myeloid cells (CD11b+/Gr-1+) was observed in spleens of the tumour-bearing mice. These findings indicate that the immune system of the tumour-bearing individuals was compromised, as compared to that of normal individuals or tumour regressors. To our knowledge, this is the first report that has demonstrated the positive effect of local administration of the DC-based, HPV16 E6/E7 oncoprotein-containing, tumour lysate-loaded vaccines in the treatment of surgical minimal residual tumour disease.

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