Abstract
Background
Although current immunotherapeutic strategies including adenovirus (AdV)‐mediated gene therapy and dendritic cell (DC) vaccine can all stimulate antitumor cytotoxic T lymphocyte (CLT) responses, their therapeutic efficiency has still been limited to generation of prophylactic antitumor immunity against re‐challenge with the parental tumor cells or growth inhibition of small tumors in vivo. However, it is the well‐established tumors in animal models that mimic clinical patients with existing tumor burdens. Alpha tumor necrosis factor (TNF‐α) is a multifunctional and immunoregulatory cytokine that induces antitumor activity and activates immune cells such as DCs and T cells. We hypothesized that a combined immunotherapy including gene therapy and DC vaccine would have some advantages over each modality administered as a monotherapy.
Methods
We investigated the antitumor immunotherapeutic efficiency of gene therapy by intratumoral injection of AdVTNF‐α and DC vaccine using subcutaneous injection of TNF‐α‐gene‐engineered DC~TNF‐α~ cells, and further developed a combined AdV‐mediated TNF‐α‐gene therapy and TNF‐α‐gene‐engineered DC~TNF‐α~ vaccine in combating well‐established MO4 tumors expressing the ovalbumin (OVA) gene in an animal model.
Results
Our data show that vaccination of DC~TNF‐α~ cells pulsed with the OVA I peptide can (i) stimulate type 1 immune response with enhanced antitumor CTL activities, (ii) induce protective immunity against challenge of 5 × 10^5^ MO4 tumor cells, and (iii) reduce growth of the small (3–4 mm in diameter), but not large, established MO4 tumors (6–8 mm in diameter). Our data also show that AdVTNF‐α‐mediated gene therapy can completely eradicate small tumors in 6 out of 8 (75%) mice due to the extensive tumor necrosis formation, but not the large tumors (0%). Interestingly, a combined AdVTNF‐α‐mediated gene therapy and TNF‐α‐gene‐engineered DC~TNF‐α~ vaccine is able to cure 3 out of 8 (38%) mice bearing large MO4 tumors, indicating that the combined immunotherapy strategy is much more efficient in combating well‐established tumors than monotherapy of either gene therapy or DC vaccine alone.
Conclusions
This novel combined immunotherapy may become a tool of considerable conceptual interest in the implementation of future clinical objectives. Copyright © 2004 John Wiley & Sons, Ltd.