Systemic disposition and induction of antitumor immunity with murine gene-modified dendritic cells

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Administration of therapeutic gene-modified dendritic cells (DCs) is a promising approach for cancer immunotherapy. For its practical application, comprehensive examinations of safety are necessary, but not enough work has been done on the in vivo behavior of DC after administration. Thus, as a pre-clinical study, we developed a system to evaluate characteristics of gene-modified DCs including the disposition after administration in a mouse model.Mouse Interleukin-12 (mIL-12) that induced anti-tumor immunoreactions was selected as a therapeutic gene and recombinant adenoviral vector expressing mIL- l2 (Ad-mIL-12) was constructed. On the other hand, mouse bone marrow-derived immature dendritic cells (m-iDCs) ware generated in culture containing GM-CSF. This m-iDCs were infected with Ad-mIL-12 with centrifugation method, and mIL-12 gene-transduced dendritic cells (mIL-12-iDCs) are used for analysis of surface antigen and measurements of IL-12 concentrations in the supernatants. As a result, the surface expressions of CD80 and CD86 as well as the expression of mIL-12 protein were confirmed, suggesting that these mIL-12-iDCs had immunostimulating properties.Next, this mIL-12-iDC was administered to mice with direct intrahepatic injection. Serum mIL-12 concentration, values of hematological-biochemical tests, weight of the spleen, and nuclear cell count were measured. There were no significant difference among mIL-12-iDC group, non-treatment group and sham-operated group. In addition, a real-time PCR method was developed to quantify viral DNA as adenovirus E4 copy number. In some samples, viral DNA was detected in lung and spleen derived from mIL-12-iDC injected mice, suggesting the possibility that mIL-12-iDC administered to the liver has reached another organs through the blood stream.This system is regarded as an effective method to examine the safety in gene therapy using therapeutic gene-modified cells.