Interleukin-2 Gene Transduction into Freshly Isolated Lung Adenocarcinoma Cells with Adenoviral Vectors

Abstract

We evaluated the efficiency of gene transduction and of gene expression by adenoviral vectors in human lung adenocarcinoma cells. Freshly isolated cancer cells were collected from pleural effusions in adenocarcinoma patients by centrifugation with a Percoll gradient. Adenoviral vectors resulted in effective gene transduction into human lung cancer cell lines and into freshly isolated lung adenocarcinoma cells. In an experiment using the β-galactosidase (LacZ) gene, the Adex1CA vector with a regulatory sequence of chicken β-actin as promoter and an enhancer derived from cytomegalovirus produced a higher transduction ratio and greater expression levels than adenoviral vectors with other promoter systems. Transduction with Adex1CA vectors containing the human interleukin-2 (IL-2) gene (Adex1CAhIL-2) resulted in enhanced secretion of IL-2 from gene-modified lung cancer cells. Treatment with normal human serum inhibited gene transduction by Adex1CAhIL-2 but did not inhibit gene expression after transduction by Adex1CAhIL-2. The secretion of IL-2 from the gene-modified cells, which were irradiated at 100 Gy before transduction, continued for 8 days. In a mouse model, the intrapleural injection of IL-2 gene-modified 3LL cells transduced by Adex1CAhIL-2 could cure the pre-existing lung tumors with malignant pleural effusions to induce tumor-specific immunity. But these therapies did not show any therapeutic benefit on the pre-existing tumor in subcutaneous region. These data suggest a potentially useful but limited clinical role of Adex1CAhIL-2 in gene therapy for lung cancer patients.

Overview summary

Heike et al. showed that the transduction could efficiently be done by the recombinant adenovirus containing the human interleukin-2 (IL-2) gene (Adex1CAhIL-2) and high IL-2 expression was observed in freshly isolated human lung adenocarcinoma cells. The secretion of IL-2 from the gene-modified cells, which were irradiated at 100 Gy before transduction, continued for 8 days. Treatment with normal human serum inhibited gene transduction by Adex1CAhlL-2. On the other hand, normal human serum had no effect on the expression of the transduced gene. Treatment with the human serum after gene transduction is reasonable strategy for gene therapy using ex vivo gene transduction by recombinant adenoviruses for inhibiting undesired gene transduction by free vectors in tumor vaccine suspension. In a mouse model, intrapleural injection of IL-2 gene-modified 3LL cells transduced by Adex1CAhIL-2 could cure pre-existing lung tumors with malignant pleural effusions to induce tumor-specific immunity but did not cure the pre-existing subcutaneous tumors nor extend the survival of the mice. Subcutaneous injection of IL-2 gene-modified 3LL cells did not cure the pre-existing lung 3LL tumors nor subcutaneous tumors and could not extend the survival of the mice, even though this treatment could induce tumor specific immunity to protect following 3LL challenge.