No abstract

present study, we investigate the molecular mechanisms involved in the H 2 O 2 -mediated induction of MMP-1. Mutational analysis of an MMP-1 promoter indicates that both the single nucleotide polymorphism creating an Ets binding site at ؊1607 and a proximal AP-1 site at ؊1602 are required for maximal H 2 O 2 -dependent transcription. The redox-sensitive MMP-1 protein expression requires activation of both ERK1/2 and JNK pathways. Importantly, JNK signaling is largely responsible for the H 2 O 2 sensitivity of the MMP-1 promoter, whereas ERK1/2 contributes to both its basal and H 2 O 2 dependence. H 2 O 2 control of Ets-1 expression was ERK1/2-dependent whereas that of c-Jun requires both ERK1/2 and JNK signaling. Chromatin immunoprecipitation assays indicate that binding of the histone acetyltransferase, p300, and the transcription factors Ets-1 and c-Jun to the MMP-1 promoter is redox sensitive. The redox sensitivity of MMP-1 expression is also associated with an increase in the abundance of oxidatively inactivated protein-tyrosine phosphatases. Targeted cytosolic or mitochondrial scavenging of H 2 O 2 prevented all of the aforementioned signals. These studies provide substantial insight into the mechanisms underlying the redox-dependent control of MMP-1 and may lead to the development of novel targeted antioxidant-based inhibitory therapies for controlling MMP-1 expression during degenerative disease processes. The matrix metalloproteinase (MMP)5 family consists of at least 25 zincdependent proteases that degrade multiple components of the extracellular matrix (ECM) (1). Under normal physiological conditions MMPs are important for development and wound healing; however, their augmented expression is associated with numerous disease pathologies (2). For example, MMPs are important at many stages of metastasis and the high level expression of the MMP family member, MMP-1, has been linked to poor prognosis in many types of cancers (3-9).Within the MMP-1 promoter, Brinckerhoff and co-workers (10) identified a single nucleotide polymorphism (SNP) guanine insertion at Ϫ1607 (1G 3 2G) base pairs that enhances the basal rate of transcription by creation of an Ets binding domain. Ets transcription factors include a large family of helix-turn-helix proteins (11) that normally do not bind DNA alone, but preferentially form coactivator complexes with transcription factors, like activator protein-1 (AP-1) (12). The proto-oncoproteins Fos and Jun, which comprise the AP-1 complex, can homo-or heterodimerize and bind its cognate consensus sequence (TGACTCA) in the regulatory domains of many genes including various MMP family members (13). Both Ets and AP-1 play a critical role in regulating the expression of various MMP family members, particularly that of MMP-1 (14). The MMP-1 SNP is associated with a higher risk of metastasis in patients with a variety of distinct cancers (15-19). More striking is the finding that both Ets-1 and MMP-1 immunoreactivity is high in stromal tissue adjacent to the leading edge of several tumor t...

Many degenerative disease processes associated with aging result from enhanced extracellular matrix (ECM) breakdown. Concomitant with aberrant matrix destruction are alterations in levels of reactive oxygen species (ROS) generating and detoxification systems. ROS function as second messengers due to their ability to react with wide range of biomolecules resulting in modification of an array of signaling networks. ROS can activate upstream kinases (MKK) responsible for MAPK activation and restrict the activity of their inhibitory phosphatases. Here we focus on the redox-sensitive signaling components that control the expression of MMP-1, which is largely responsible for maintaining ECM homeostasis. Numerous disease processes are associated with shifts in steady-state ROS levels that influence overall ECM degradation. This review highlights the redox-sensitive regulatory signals that control the expression of the primary initiating protease MMP-1 and provides strong rational for the use of antioxidant based therapies for treatment of degenerative disorders associated with aberrant matrix destruction.

INTRODUCTION Integrin receptors for cell adhesion to the extracellular matrix have important roles in all stages of cancer progression and metastasis. Since the integrin family was discovered in the early 1980’s, many studies have identified critical adhesion and signaling functions for integrins expressed on tumor cells, endothelial cells, and other cell types of the tumor microenvironment, in controlling proliferation, survival, migration, and angiogenesis. In recent years, the laminin-binding integrin α3β1 has emerged as a potentially promising anti-cancer target on breast cancer cells. AREAS COVERED This review covers studies from the past decade that implicate integrins as promising anti-cancer targets and discusses the development of integrin antagonists as anti-cancer therapeutics. In particular, this paper discusses recent preclinical studies that have identified the laminin-binding integrin α3β1 as an appealing anti-cancer target, and considers the knowledge gaps that must be closed to fully exploit this integrin as a therapeutic target for breast cancer. EXPERT OPINION Although the tumor-promoting functions of α3β1 implicate this integrin as a promising therapeutic target on breast cancer cells, successful exploitation of this integrin as an anti-cancer target will require a better understanding of the molecular mechanisms whereby it regulates specific tumor cell behaviors, and the identification of the most appropriate α3β1 functions to antagonize on breast cancer cells.

Manganese superoxide dismutase (SOD2) has been well established to be essential for protection from a variety of apoptotic stimuli. Here we demonstrate that the antiapoptotic effects of SOD2 are attributed to its ability to generate H(2)O(2) and that its efficient removal resensitizes cells to tumor necrosis factor (TNF)-alpha-induced apoptosis. SOD2 overexpression in HT-1080 cells leads to a decrease in the fluorescence of the superoxidesensitive fluorophore, dihydroethidium, and a concomitant increase in oxidation of the H2O2-sensitive dye, dichlorodihydrofluorescein diacetate (DCFDA). The rate of aminotriazole-inhibited catalase activity also was increased when SOD2 is overexpressed and reflects a 1.6-fold increase in the steady-state production of H(2)O(2). The increase in H(2)O(2) was associated with decreased sensitivity to TNF-alpha-mediated apoptosis, as measured by monitoring the loss of mitochondrial membrane potential (MMP), caspase activation, poly-ADP ribose polymerase (PARP) cleavage, and accumulation of hypodiploid DNA content. Both the increase in H2O2 and resistance to TNF-mediated apoptosis were reversed by coexpression of catalase. The lipid hydroperoxide scavengers, beta-hydroxytoluene and trolox, and the iron chelator, desferroxamine, showed partial recovery of TNF-induced apoptosis. These findings indicate that increases in the intracellular steady-state production of H(2)O(2) by SOD2 can block the activation of key processes fundamental to the process of programmed cell death.