Interferon γ-Induced Human Guanylate Binding Protein 1 Inhibits Mammary Tumor Growth in Mice

Karoline Lipnik,Stefanie Rungaldier,Helga Petznek,Michael Stürzl,Christine Hohenadl,Simonetta Astigiano,Elisabeth Naschberger,Silvano Ferrini,Nathalie Gonin-Laurent,Petra Kodajova

doi:10.2119/molmed.2009.00172

Abstract

Interferon gamma (IFN-gamma) has recently been implicated in cancer immunosurveillance. Among the most abundant proteins induced by IFN-gamma are guanylate binding proteins (GBPs), which belong to the superfamily of large GTPases and are widely expressed in various species. Here, we investigated whether the well-known human GBP-1 (hGBP-1), which has been shown to exert antiangiogenic activities and was described as a prognostic marker in colorectal carcinomas, may contribute to an IFN-gamma-mediated tumor defense. To this end, an IFN-independent, inducible hGBP-1 expression system was established in murine mammary carcinoma (TS/A) cells, which were then transplanted into syngeneic immune-competent Balb/c mice. Animals carrying TS/A cells that had been given doxycycline for induction of hGBP-1 expression revealed a significantly reduced tumor growth compared with mock-treated mice. Immunohistochemical analysis of the respective tumors demonstrated a tightly regulated, high-level expression of hGBP-1. No signs of an enhanced immunosurveillance were observed by investigating the number of infiltrating B and T cells. However, hemoglobin levels as well as the number of proliferating tumor cells were shown to be significantly reduced in hGBP-1-expressing tumors. This finding corresponded to reduced amounts of vascular endothelial growth factor A (VEGF-A) released by hGBP-1-expressing TS/A cells in vitro and reduced VEGF-A protein levels in the corresponding mammary tumors in vivo. The results suggest that hGBP-1 may contribute to IFN-gamma-mediated antitumorigenic activities by inhibiting paracrine effects of tumor cells on angiogenesis. Consequently, owing to these activities GBPs might be considered as potent members in an innate, IFN-gamma-induced antitumoral defense system.

Highlights

The type II interferon, interferon γ (IFN-γ), has recently been implicated in cancer immunosurveillance in addition to its well-known function in promoting host responses to microorganisms
To generate an inducible human guanylate binding protein (GBP)-1 (hGBP-1)– expressing tumor cell line, the mouse mammary adenocarcinoma cell line TS/A was first transduced with an MLVderived retroviral vector encoding a tetracycline (Tet) on/off regulator system [23,24]
The resulting cell population was subsequently transfected with the corresponding Tet-responsive expression vector pUHD10.3-GBP-Hyg, giving rise to single cell clones which were tested for inducible hGBP-1 expression upon treatment with doxycycline, a commonly used tetracycline derivative

Summary

Introduction

The type II interferon, interferon γ (IFN-γ), has recently been implicated in cancer immunosurveillance in addition to its well-known function in promoting host responses to microorganisms (reviewed in [1]). Natural killer (NK) cells, NK T cells and apoptosis-mediating ligands such as TRAIL (tumor necrosis factor–related apoptosis-inducing ligand) have been shown to be involved in this process [2], the detailed cellular and molecular levels of the cancereliminating phase still remain to be elucidated. In this respect, Kundu and colleagues [5,6] previously reported interleukin (IL)-10–induced antitumoral activity in a mammary cancer mouse model. The role of the IFN-γ–induced guanylate binding protein (GBP), remained unclear

Methods

Results

Conclusion