Pharmacokinetics of combined gene therapy expressing constitutive human GM-CSF and hyperthermia-regulated human IL-12

Fang Wei,Xiafang Chen,Chuanyuan Li,Qian Huang,Jufeng Zhang,Huiping Wang

doi:10.1186/1756-9966-32-5

Abstract

BackgroundAn adenovirus that expresses both interleukin (IL)-12 and granulocyte-macrophage colony-stimulating-factor (GM-CSF) has been proven to be very effective in treating several tumors, but causes serious normal tissue toxicities.MethodsIn this study, a novel adenoviral vector was constructed by placing the human GM-CSF gene under the control of the CMV-IE promoter and human IL-12 gene under the control of heat shock protein 70B gene promoter. Both hGM-CSF and hIL-12 expressions in virus-infected tumor cells were analyzed in vitro and in vivo when underlying single or multiple rounds of hyperthermia.ResultsWe observed constitutive high expression of human GM-CSF and heat-induced expression of human IL-12 after a single round of hyperthermia post viral infection. The heat-induced hIL-12 expression exhibited a pulse-like pattern with a peak at 24 hrs followed by a decline 48 hrs post heat stress. Repeated heat treatment was more effective in inducing hIL-12 expression than a one-time heat treatment. Interestedly, we also observed that constitutive expression of hGM-CSF could be stimulated by heat stress in tested tumor cells.ConclusionOur study provided a novel strategy for combined gene therapy that allows constitutive expression of a non-toxic gene such as GM-CSF and heat-induced expression of a toxic gene such as IL-12. In addition, our study also showed that hyperthermia can be used to trigger gene expression in temporal and special manner.

Highlights

The unique ability of cancer to exploit the immune system in order to promote tumor growth and suppress immune response makes cancer therapy difficult
The combined use of granulocyte-macrophage colony-stimulating-factor (GM-CSF) and IL-12 can counteract the counter-regulatory role of GM-CSF on T cells (Tc) and increase the immune benefits of GM-CSF
Adenovirus preparation The adenovirus used to establish constitutively high expression of human GM-CSF and heat-inducible expression of human IL-12 was constructed according to established protocols [12] using commercially available plasmids (Microbix, Toronto, Canada)

Summary

Introduction

The unique ability of cancer to exploit the immune system in order to promote tumor growth and suppress immune response makes cancer therapy difficult. Cytokine therapy has been reported to be an effective strategy at inducing strong antitumor immune response [1]. Compared to GM-CSF is a growth factor capable of enhancing antitumor activity by activating dendritic cells (DCs) to improve antigen presentation. GM-CSF can activate macrophages and induce the release of tumor necrosis factor (TNF) [7] to achieve an antitumor effect. GM-CSF can indirectly stimulate T-cell activation via interleukin-1 release [8]. Increased cellular GMCSF expression leads to counter-regulatory immune responses to decrease the expansion of cytotoxic T cells (Tc), thereby limiting its antitumor activity [7]. An adenovirus that expresses both interleukin (IL)-12 and granulocyte-macrophage colony-stimulating-factor (GM-CSF) has been proven to be very effective in treating several tumors, but causes serious normal tissue toxicities

Methods

Results

Conclusion