Genetic modification of dendritic cells and its application for cancer immunotherapy

Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs). DCs pulsed with peptides of tumor-associated antigens (TAA) and tumor lysate have been used in cancer immunotherapy. An early clinical study demonstrated the safety of the use of DCs, but the clinical response was not sufficient. The gene-modification of DCs with TAA and soluble factor genes such as cytokine and chemokine genes has been examined to enhance the antigen-presenting capacity of DCs. Viral vectors including retroviruses and adenoviruses have been reportred to be useful to obtain a sufficient transduction efficiency into DCs. TAA gene-transduced DCs could have several advantages compared with TAA peptide-pulsed DCs as follows : 1) The use of TAA gene-modified DCs are not restricted by MHC haplotypes. 2) The gene transduction with TAA genes is likely to present the unknown TAA peptides on DCs. 3) The gene-modified DCs show the prolonged presentation of TAA peptides. The transduction of DCs with cytokine genes including IL-12 and GM-CSF have also been reported to augument the antitumor effects of DCs. Although the results in the experimental systems were promising, the clinical application of gene-modified DCs includes several problems such as the standardization of methods of manipulation and gene-transduction of DCs. Approaches to solve them require further studies.