Regulation of MMP activity - Matrix Metalloproteinases (MMPs) and tissue inhibitors of MMPs (TI

Chapter 2: Literature review

2.2. Matrix Metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs)

2.2.3. Regulation of MMP activity

2.2.3. Regulation of MMP activity

The expression of MMPs is usually low in normal tissue under normal conditions and is induced when ECM remodeling is needed (LOFFEK et al., 2011). The biological activity of MMPs is regulated tightly at three levels: (1) gene transcription and synthesis of inactive zymogens, (2) posttranslational activation of zymogens, and (3) interactions of secreted MMPs with TIMPs (BREW et al., 2000).

MMP gene expression is mainly regulated at the transcriptional level (FANJUL-FERNANDEZ et al., 2010). In addition, many of the MMP promoters are similar, in that they share common Cis-elements for the regulation of MMP gene expression, as a result to this, most MMPs are co-expressed in response to multiple stimuli, such as growth factors or inflammatory cytokines (YAN and BOYD, 2007). Several hours after exposure to stimuli, early response genes are induced and encode signaling proteins that phosphorylate different transcription factors, which are later bind to MMP genes promoters (FANJUL-FERNANDEZ et al., 2010). These signaling intermediates involved in activation of transcription factors include nuclear factor kappa B (NF-κB), the mitogen activated protein kinases (MAPK), the signal transducers and activators of transcription (STAT) and the Smad family of proteins (FANJUL-FERNANDEZ et al., 2010).

The second level of MMP regulation is activation from the latent, inactive form (VAN WART and BIRKEDAL-HANSEN, 1990). At this level, the inactive MMP proenzymes or zymogens are activated extracellularly after their secretion by the so-called cysteine switch mechanism of activation, where the interaction between the cysteine residue and the Zn²⁺ ion is disrupted and this switches the role of zinc from a noncatalytic to a catalytic one (SPRINGMAN et al., 1990; VAN WART and BIRKEDAL-HANSEN, 1990).

Despite the fact that MMPs are initially secreted as zymogens and activated extracellularly following their secretion, some MMPs like MMP-11, MMP-28 and transmembrane MMPs contain an RXK/RR furin-like enzyme recognition motif between their propeptide and the catalytic domain, which allows them to be activated intracellularly before they are secreted (PEI and WEISS, 1995). In addition, most MMPs can be activated by other activated MMPs or by other serine proteases which can cleave peptide bonds within MMP pro-domains (STERNLICHT and WERB, 2001). ProMMP-1 was found to be activated directly by MMP-3

(NAGASE et al., 1992). MMP-13 can be activated by MT1-MMP and activated MMP-13 can also activate MMP-9 (COWELL et al., 1998; KNAUPER et al., 2002). MMP-3 may also be responsible for the activation of MMP-9 (SOBRIN et al., 2000). MMP-2 can be activated by the membrane-type MMPs through a unique multistep pathway involving MT1-MMP and TIMP-2 (DERYUGINA et al., 2001; FILLMORE et al., 2001).

The third level in the regulation of MMP activity is inhibition of the active enzyme by physiological inhibitors (GOMEZ et al., 1997). Almost all MMPs are inhibited by endogenous tissue inhibitors (TIMPs) which block MMP activity by binding non-covalently to the target, inhibiting functioning of the active site by interacting with the Zn²⁺ (NAGASE et al., 2006). Differences in the ability to inhibit MMPs are found among TIMPs. TIMP-1 has the ability to inhibit MMP-3, MMP-9 and MMP-1 more effectively than TIMP-2 (O'CONNELL et al., 1994). On the other hand, TIMP-2 can inhibit MMP-2 more effective than TIMP-1 (STETLER-STEVENSON et al., 1989; HOWARD et al., 1991). However, TIMP-2 can mediate pro-MMP-2 activation when the concentration of TIMP-2 is low, whereas a greater concentration of TIMP-2 inhibits MMP-2 (BUTLER et al., 1998). TIMP-3 was found to inhibit both MMP-2 and MMP-9 (BUTLER et al., 1999), whereas TIMP-4 has the ability to inhibit all classes of MMPs (STRATMANN et al., 2001). In addition to TIMPs, other physiological MMP inhibitors have been recognized, such as procollagen C-terminal proteinase enhancer (PCPE), reversion-inducing cysteine-rich protein with Kazal motifs (RECK) which inhibits MMP-9, MMP-2 and MT1-MMP, beta-amyloid precursor protein (APP) and thrombospondin-2 (TSP-2), both proteins can inhibit MMP-2 (MOTT et al., 2000;

OH et al., 2001b; YANG et al., 2001b; HIGASHI and MIYAZAKI, 2003).

12 Fig. 1: Domain structure of the MMPs

(Modified from EGEBLAD and WERB, 2002; POLIMENI and PRATO, 2014)

MMP, matrix metalloproteinase; Pre, signal sequence; Pro, propeptide with a free zinc-ligating thiol (SH) group; Zn, zinc-binding site; Fi, collagen-binding fibronectin type II inserts H, hinge region; Cy, very short cytoplasmic tail; GPI, glycophosphatidyl inositol-anchoring domain; Fu, furin-susceptible site; Vn, vitronectin-like domain; TM, carboxy-terminal single transmembrane domain; Ig, immunoglobulin-like domain.

13 Tab. 2: Members of the MMP family

(modified from SNOEK-VAN BEURDEN and VON DEN HOFF, 2005) Subtype of MMPs MMP no. Substrates

Collagenases

Interstitial collagenase MMP-1 Col I, II, III, VII, VIII, X, gelatin

Neutrophil collagenase MMP-8 Col I, II, III, VII, VIII, X, aggrecan, gelatin Collagenase 3 MMP-13 Col I, II, III, IV, IX, X, XIV, gelatin Gelatinases

Gelatinase A MMP-2 Gelatin, Col I, II, III, IV, VII, X Gelatinase B MMP-9 Gelatin, Col IV, V

Stromelysins

Stromelysin-1 MMP-3 Col II, IV, IX, X, XI, gelatin Stromelysin-2 MMP-10 Col IV, laminin, fibronectin, elastin Stromelysin-3 MMP-11 Col IV, fibronectin, laminin, aggrecan Matrilysins

Matrilysin-1 MMP-7 Fibronectin, laminin, Col IV, gelatin Matrilysin-2 MMP-26 Fibrinogen, fibronectin, gelatin MT-MMP

MT1-MMP MMP-14 Gelatin, fibronectin, laminin MT2-MMP MMP-15 Gelatin, fibronectin, laminin MT3-MMP MMP-16 Gelatin, fibronectin, laminin

MT4-MMP MMP-17 Fibrinogen, fibrin

MT5-MMP MMP-24 Gelatin, fibronectin, laminin

MT6-MMP MMP-25 Gelatin

Others

Macrophage metalloelastase MMP-12 Elastin, fibronectin, Col IV

MMP-19 Aggrecan, elastin, fibrillin, Col IV, gelatin Enamelysin MMP-20 Aggrecan, cartilage oligomeric matrix protein

MMP-21 Aggrecan

MMP-23 Gelatin, casein, fibronectin

CMMP MMP-27 Unknown

Epilysin MMP-28 Unknown

MMP, matrix metalloproteinase; MT-MMP, membrane-type matrix metalloproteinase; Col, collagen; CMMP, chicken MMP

14 2.2.4. TIMPs

Tissue inhibitors of metalloproteinases (TIMPs) are specific endogenous inhibitors of matrix metalloproteinases (BREW and NAGASE, 2010). Therefore, they regulate ECM turnover, and tissue remodeling (BREW and NAGASE, 2010). Four mammalian TIMPs have been characterized (TIMP-1, -2, -3 and -4; BREW and NAGASE, 2010). In 1975 the inhibitory activity of TIMP-1 was first reported in a media of cultured human skin fibroblasts (BAUER et al., 1975).

TIMPs are consisting of 184–194 amino acids and contain two domains (one N-terminal domain of about 125 amino acid residues and a C-terminal domain with about 65 residues) (XU et al., 2011). The conformation of each domain is stabilized by three disulfide bonds (NAGASE et al., 2006). Although the mammalian TIMPs share many basic similarities, they exhibit distinctive structural features, biochemical properties and expression patterns and this may contribute to the different roles of TIMPs in vivo (BAKER et al., 2002).

2.2.5. Role of MMPs and TIMPs in tumor progression

In several studies MMPs are strongly implicated in cancer progression and MMP-mediated degradation of ECM is one of the principal alterations observed in the cancer microenvironment (GIALELI et al., 2014). The strong association of MMP expression with neoplastic progression is well documented in both in vitro and in vivo systems (JACOB and PREKERIS, 2015). In many animal transplantation assays, tumor cells increase their invasive behavior and metastatic rate when MMP expression is up-regulated. In contrast, down-regulation of MMPs reduces the aggressive behavior of tumor cells (COUSSENS and WERB, 1996; EGEBLAD and WERB, 2002). Moreover, it has been found that the expression of MMPs is increased in many types of cancers and their expression correlates with advanced tumor stage and increased invasion and metastasis (COUSSENS and WERB, 1996;

EGEBLAD and WERB, 2002). A negative association between MMP expression and tumor prognosis has been found in most studies (EGEBLAD and WERB, 2002). However, there are a few reports in which increased expression of specific MMPs reflects a favorable prognosis;

for example, MMP-12, also referred as human macrophage metalloelastase (HME), has been shown to play an important role in the inhibition of tumor progression and its overexpression is associated with a better prognosis in patients with colorectal carcinoma (YANG et al., 2001a). This can be attributed to the ability of MMP-12 to convert plasminogen into angiostatin, an inhibitor of tumor angiogenesis (SHI et al., 2006).

MMPs are not only involved in the invasion and metastasis of neoplastic cells, but are also implicated in several steps of cancer development, for example regulating growth and survival of tumor cells, promoting or inhibiting angiogenesis, promoting the epithelial-to-mesenchymal transition and regulating the immune response against neoplastic cells (EGEBLAD and WERB, 2002).

MMP-9 knockout mice exhibited a reduced tumor cell proliferation and invasion compared to wild-type animals (COUSSENS et al., 2000). There are three main mechanisms through which MMPs can promote tumor cell proliferation. First through releasing precursors of growth factors, for example, TGF-α (PESCHON et al., 1998), second, through liberating peptide growth factors like insulin-like growth factor which is released under the influence of MMP-9 (MANES et al., 1999) and third, through ECM remodeling which may cause the expression of cell receptors like alpha v beta integrin 6 (αvß6), which enhances the proliferation of a human colon carcinoma cell line (AGREZ et al., 1994; Fig 2 a).

MMPs like MMP-3, -7, -9 and -11 have the ability to regulate apoptosis (EGEBLAD and WERB, 2002). MMP-11, expressed by fibroblastic cells surrounding tumor cells, was found to increase tumorigenesis by decreasing tumor cell death through regulating both necrotic and apoptotic processes (BOULAY et al., 2001). Moreover, MMP-7 can promote tumor cell survival by cleaving Fas (apoptosis stimulating fragment) ligand and reducing its effectiveness in triggering Fas-mediated apoptosis (MITSIADES et al., 2001). On the other hand, an increase in the number of apoptotic cells was detected in MMP-3 transgenic mice with mammary tumors compared to control animals (WITTY et al., 1995).

The functions of TIMPs are not restricted to MMP inhibition. Numerous studies report a wide variety of other functions. Moreover, conflicting data of the role of TIMPs in tumor progression have been shown (HENRIET et al., 1999). Some studies demonstrate an increase of TIMP-1, -2 and -3 expression in malignant tumor tissue compared to the non-malignant counterpart and a low expression of TIMP-1 was associated with an increased tumor grade (YOSHIJI et al., 1996; HEWITT et al., 2000; SOGAWA et al., 2003; AABERG-JESSEN et al., 2009; KORNFELD et al., 2011). However, other studies showed that downregulation of TIMP-1 and TIMP-2 leads to increase tumor invasiveness compared to overexpression which leads to reduce tumor growth and metastasis (KHOKHA et al., 1989; ALBINI et al., 1991;

DECLERCK et al., 1992). The negative association between TIMP expression and tumor progression can be attributed to the known inhibiting effect of TIMPs on MMPs, on the other hand, the positive association between TIMP expression and tumor progression can be attributed to (1) the growth factor like activity of specific TIMPs, such as TIMP-1 on a variety

of normal and neoplastic cell types (HAYAKAWA et al., 1992), (2) its positive role in angiogenesis through the up-regulation of vascular endothelial growth factor (VEGF) expression (YOSHIJI et al., 1998) and (3) the role of TIMP-2 in the activation of MMP-2 (KINOSHITA et al., 1998).

2.2.6. Role of MMPs and TIMPs in invasion and metastasis

Metastases are the major cause of death from cancer whereas local lesions due to the primary tumor are a minor issue (YOON et al., 2003). In addition, studies performed over the last decades reveal the pivotal role of MMPs in tumor metastasis (WESTERMARCK and KAHARI, 1999).

The first evidence for a role of MMPs in metastasis came from the antimetastatic effect of TIMPs on murine melanoma cells (SCHULTZ et al., 1988). Among the previously reported human MMPs, MMP-2 and MMP-9 are the key proteins involved in tumor invasion and metastasis and they are abundantly expressed in various malignant tumors (JOHNSEN et al., 1998). Metastasis is an extremely complex process and involves detachment of the cell from the neoplastic tissue, invasion of the surrounding stroma and spread through blood vessels or lymphatics (EGEBLAD and WERB, 2002). Cleavage of laminin-5 (ln-5), an extracellular matrix substrate for cell adhesion found in epithelial basement membranes, by MMP-14 and MMP-2 can trigger cell migration and thus may play a role in the early phases of tumor invasion (KOSHIKAWA et al., 2000). MMP-14 promotes cell migration through the cleavage of CD44, a major receptor for hyaluronan (KAJITA et al., 2001). Moreover, CD44 also binds MMP-9 on the surface of mouse mammary carcinoma and human melanoma cells. This localization promotes collagen IV degradation and mediates tumor cell invasion (YU and STAMENKOVIC, 1999). MMPs have also important roles in the late events of metastasis which involve the intravasation into blood vessels or lymphatics, extravasation and establishment of a secondary growth site (CHAMBERS and MATRISIAN, 1997). MMP-9 is required for the intravasation of tumor cells and MMP-14 enhances the survival rate of tumor cells in an experimental pulmonary metastasis assay (TSUNEZUKA et al., 1996; KIM et al., 1998) (Fig.2 b).

2.2.7. Angiogenesis and MMPs / TIMPs

Pathological angiogenesis is a hallmark of cancer and it is necessary for persistent tumor growth, because it provides the tumor cells with the necessary gas exchange and nutrients (CHANG and WERB, 2001). Many studies demonstrate the significant role of MMPs in the

induction of angiogenesis by targeting these MMPs using endogenous or synthetic MMP inhibitors (MARTIN et al., 1999; LI et al., 2001; OH et al., 2001a; RODRIGUEZ-MANZANEQUE et al., 2001; YOSHIDA et al., 2002). In addition, MMP-14- and MMP-9-deficient mice have severe defects in angiogenesis, demonstrating that MMP-14 and MMP-9 are implicated directly in the regulation of angiogenesis (VU et al., 1998; ZHOU et al., 2000).

MMPs may contribute in the angiogenesis process through the cleavage of individual matrix components, such as type I collagen (SEANDEL et al., 2001). In a rat corneal micropocket angiogenesis assay, cleavage of collagen type IV results in the exposure of an important cryptic site within its triple helical structure and blockage of this site disrupts integrin-dependent endothelial cell interaction and inhibits angiogenesis (XU et al., 2001). Another possibility is that MMPs, specifically MMP-9, are important for angiogenesis by releasing pro-angiogenic growth factors, such as VEGF during carcinogenesis of pancreatic islets in mice (BERGERS et al., 2000). Using an in vitro wound healing migration model, MMP-14 has been shown to play an important role in angiogenesis through regulating endothelial migration, invasion and formation of capillary tubes during angiogenic response and blocking the catalytic domain of MMP-14 inhibits these processes (GALVEZ et al., 2001). Moreover, MMP-14 can regulate neovascularization by acting as a pericellular fibrinolysin, thereby potentially allowing endothelial cells to invade further into the tumor tissue (HIRAOKA et al., 1998) (Fig. 2 c).

On the other hand, MMPs, specifically MMP-2, MMP-9 and MMP-12, may act anti-angiogenetically through cleavage of plasminogen to generate angiostatin which inhibits endothelial cell proliferation and thus diminishes metastatic tumor cell growth (DONG et al., 1997; CORNELIUS et al., 1998). In murine hemangioendothelioma cell cultures, MMP-3, MMP-9, MMP-13 and MMP-20 were found to have important roles in the generation of endostatin, a C-terminal fragment of the basement membrane collagen type XVIII, which is able to inhibit endothelial cell proliferation, migration in addition to angiogenesis and tumor growth (FERRERAS et al., 2000) (Fig. 2 c).

The TIMP family plays an important role in angiogenesis (SANG, 1998). TIMPs can prevent angiogenesis by the inhibition of MMPs (HANDSLEY and EDWARDS, 2005). Another possibility is the activation of MMP inhibitors, such as RECK, which in turn, inhibits angiogenesis (OH et al., 2004). In addition, TIMPs exhibit anti-angiogenic activity that is independent of their MMP inhibitory activities. Using in vitro cell culture and a syngeneic murine tumor model of colon cancer, the over-expression of TIMP-2 can inhibit tumor growth and angiogenesis by up-regulating mitogen-activated protein kinase phosphatase 1 which

dephosphorylates p38 mitogen-activated protein kinase, a molecule involved in endothelial cell proliferation and migration (FELDMAN et al., 2004). Moreover, TIMP-1 inhibits endothelial cell invasion of human amniotic membranes (MIGNATTI et al., 1986). A TIMP-related protein isolated from bovine articular cartilage blocks endothelial cell proliferation and angiogenesis (MOSES et al., 1990). In addition, TIMP-1 and TIMP-2 inhibit chick yolk sac vessel morphogenesis in response to polyamines (TAKIGAWA et al., 1990).

TIMPs may also enhance tumor angiogenesis by inhibiting MMPs which play a critical role in the generation of potent inhibitors of angiogenesis. For example MMP-12 can generate angiostatin by cancer-mediated proteolysis of plasminogen (CORNELIUS et al., 1998). In addition, other members of the MMP family, such as MMP-3, -7, -9, -13, -20 can release endostatin, another well-known anti-angiogenic factor from collagen XVIII (HELJASVAARA et al., 2005). Therefore, by inhibiting these MMPs, TIMPs may enhance tumor angiogenesis (CORNELIUS et al., 1998; WEN et al., 1999). Supporting this idea, mammary carcinoma over-expressing TIMP-1, showed enhanced VEGF expression and enhanced growth rate (YOSHIJI et al., 1998).

19 Fig. 2: Role of MMPs in tumor progression (modified from EGEBLAD and WERB, 2002)

a. Matrix metalloproteinases (MMPs) promote tumor growth by cleaving insulin-growth-factor-binding protein (IGF-BP), thereby liberating IGF, by shedding precursors of growth factors including transforming growth factor-α (TGF-α) and by regulating extracellular matrix (ECM), which promotes growth indirectly through interactions between ECM molecules and integrins.

b. MMPs promote invasion and migration by degrading structural ECM components, such as laminin 5 (Lam-5). In addition, MMPs promote cell migration through cleavage of CD44.

c. MMPs promote angiogenesis by increasing the bioavailability of pro-angiogenic growth factors, such as vascular endothelial growth factor (VEGF). In addition, MMPs promote invasion of endothelial cells by cleaving structural components of the ECM, such as collagen types I (Col-I) and IV (Col-IV) and fibrin. Cleaved Col-IV acts pro-angiogenetically by binding to αvβ3 integrin. MMPs may act anti-pro-angiogenetically through cleavage of plasminogen and Col-XVIII resulting in the generation of anti-angiogenic factors such as angiostatin and endostatin.

20 2.3. Inflammation and cancer

In 1863, Rudolf Virchow was the first to describe the association of inflammation and cancer when he noted leukocytes in neoplastic tissue and suggested that the ‘‘lymphoreticular infiltrate’’ reflected the origin of cancer at sites of chronic inflammation (VIDAL-VANACLOCHA, 2009). In addition, previous epidemiological studies in humans have shown that chronic inflammation is a cofactor in many carcinogeneses, such as gastric cancer and gastric mucosal lymphoma which is linked to Helicobacter pylori, and other malignancies caused by chemical and physical agents and autoimmune reactions (EKBOM et al., 1990;

MANTOVANI et al., 2008).

2.3.1. Role of inflammation in cancer

Recent studies revealed that cancer and inflammation are connected by two pathways. The first pathway is called extrinsic, in which inflammatory or infectious diseases increase the risk for development of cancer (MANTOVANI et al., 2008). The second pathway is called the intrinsic one. This pathway has been addressed recently when evidence of inflammatory cells and mediators were noted within the tumor microenvironment without the presence of a usual cause of inflammation such as the presence of infectious agents (MANTOVANI et al., 2008).

During this pathway, the genetic alterations that cause neoplasia are responsible for generating the inflammatory changes (MANTOVANI et al., 2008). The two pathways then activate transcription factors, such as nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) which induce the production of inflammatory cytokines and chemokines which recruit inflammatory cell infiltration and augment the inflammation within the tumor microenvironment (MANTOVANI et al., 2008).

The inflammatory reaction and its components within the tumor microenvironment contribute to every aspect of carcinogenesis (GRIVENNIKOV et al., 2010). However, their detailed role in tumor development is still controversial (CHOW et al., 2012). Initial studies found that animals with impaired immune response are more susceptible to virally or chemically induced neoplasms (NOMOTO and TAKEYA, 1969; SANFORD et al., 1973; STUTMAN, 1974).

Furthermore, other investigations demonstrate the importance of cytokines such as interferon γ (IFN- γ) in protecting the host from tumor development (DIGHE et al., 1994). On the other hand, chronic inflammation significantly contributes to tumor development through several mechanisms such as enhancing angiogenesis and tissue invasion (GRIVENNIKOV et al., 2010). However, some surveys suggest that both tumor-suppressing and tumor-induced inflammation can co-exist within the same tumor (SWANN et al., 2008).

21 2.3.2. Inflammatory cell components of tumors

Often a wide range of immune cells, such as monocytes, macrophages, dendritic cells, neutrophils, eosinophils, mast cells and lymphocytes infiltrate a tumor and establish an inflammatory microenvironment (MACARTHUR et al., 2004). The infiltrating immune cells may repress neoplastic growth or may act as tumor promoters (LU et al., 2006). All of these immune cells are capable of producing an assorted array of cytokines, other mediators such as reactive oxygen species, serine and cysteine proteases, MMPs, tumor necrosis factor α (TNF-α), interleukins and interferons which elicit innate immune response, tissue remodeling and angiogenesis (COUSSENS and WERB, 2002). Macrophages represent up to 50% of the tumor mass and are considered as the major players in the connection between inflammation and neoplasms (SOLINAS et al., 2009). Macrophages most often originate from blood-derived monocytes and can be activated in response to cytokines and other signals and differentiate into two distinct types, M1 (classically activated) and M2 (alternatively activated; SCHMID and VARNER, 2012). M1 polarization occurs upon stimulation with IFN-γ and lipopolysaccharides (LPS). M1 macrophages are characterized by production of high levels of IL-12, IL-23, TNF-α and CXC chemokine ligand 10 (CXCL10) and elicit cytotoxicity against microorganisms and neoplastic cells by production of reactive oxygen intermediates (ROI) and antigen presenting cell activity (SOLINAS et al., 2009). On the other hand, when macrophages are stimulated with IL-4, IL-10, IL-13 or corticosteroids, they differentiate into the M2 phenotype which is characterized by the production of IL-10,

Im Dokument Comparative evaluation of the tumor microenvironment in spontaneous canine histiocytic sarcomas and a canine histiocytic sarcoma xenotransplantation model (Seite 20-0)