Extracellular superoxide dismutase inhibits hepatocyte growth factor-mediated breast cancer-fibroblast interactions.

Briana Ormsbee Golden,Charlotte Kuperwasser,Shakeel Mir,Frederick Domann,Matthew Fitzgerald,Brandon Griess,Melissa Teoh-Fitzgerald

doi:10.18632/oncotarget.22379

Abstract

We have previously shown tumor suppressive effects of extracellular superoxide dismutase, EcSOD in breast cancer cells. In this study, an RTK signaling array revealed an inhibitory effect of EcSOD on c-Met phosphorylation and its downstream kinase c-Abl in MDA-MB231 cells. Moreover, an extracellular protein array showed that thrombospondin 1 (TSP-1), a scavenger of the c-Met ligand, hepatocyte growth factor (HGF) is significantly up-regulated in EcSOD overexpressing cells (Ec.20). We further determined the effects of EcSOD on HGF/c-Met-mediated cancer-fibroblast interactions by co-culturing normal fibroblasts (RMF) or RMF which overexpresses HGF (RMF-HGF) with MDA-MB231 cells. We observed that while RMF-HGF significantly promoted Matrigel growth of MDA-MB231, overexpression of EcSOD inhibited the HGF-stimulated growth. Similarly, a SOD mimetic, MnTE-2-PyP, inhibited HGF-induced growth and invasion of MDA-MB231. In addition, a long-term heterotypic co-culture study not only showed that Ec.20 cells are resistant to RMF-HGF-induced invasive stimulation but RMF-HGF that were co-cultured with Ec.20 cells showed an attenuated phenotype, suggesting an oxidative-mediated reciprocal interaction between the two cell types. In addition, we demonstrated that RMF-HGF showed an up-regulation of an ROS-generating enzyme, NADPH oxidase 4 (Nox4). Targeting this pro-oxidant significantly suppressed the activated phenotype of RMF-HGF in a collagen contraction assay, suggesting that RMF-HGF contributes to the oxidative tumor microenvironment. We have further shown that scavenging ROS with EcSOD significantly inhibited RMF-HGF-stimulated orthotopic tumor growth of MDA-MB231. This study suggests the loss of EcSOD in breast cancer plays a pivotal role in promoting the HGF/c-Met-mediated cancer-fibroblast interactions.

Highlights

One of the main features of cancer cells is a persistent oxidative stress or a higher steady state levels of reactive oxygen species (ROS), when compared to their normal counterparts
To determine whether the superoxide scavenging activity of extracellular superoxide dismutase (EcSOD) is required for this inhibition, we overexpressed an inactive form of EcSOD where two critical residues were mutated as previously described [19]
These data suggest that hepatocyte growth factor (HGF)/c-Met signaling is sensitive to ROS modulation

Summary

Introduction

One of the main features of cancer cells is a persistent oxidative stress or a higher steady state levels of reactive oxygen species (ROS), when compared to their normal counterparts. ROS such as superoxide anion (O2−), hydroxyl (OH), and hydrogen peroxide (H2O2) exert a multifaceted role at the cellular level. Redox homeostasis is tightly regulated by balancing ROS generation with their scavenging systems. In malignant cells aberrant regulation of redox homeostasis is often observed. Activation of oncogenes, aberrant metabolism, and defective tumor suppressor genes are intrinsic factors known to promote ROS production in cancer cells, partly through activation of ROS-generating enzymes such as NADPH oxidases [2]. The enhanced oxidative stress observed in cancer cells can result from ROS overproduction, and from decreased levels or inactivation of antioxidants such as superoxide dismutases (SODs)

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