Collagen type I: a substrate and a signal for invasion

Key participants of the tumor microenvironment of the prostate: an approach of the structural dynamic of cellular elements and extracellular matrix components during epithelial-stromal transition

Cancer is a multistep process that begins with the transformation of normal epithelial cells and continues with tumor growth, stromal invasion and metastasis. The remodeling of the peritumoral environment is decisive for the onset of tumor invasiveness. This event is dependent on epithelial-stromal interactions, degradation of extracellular matrix components and reorganization of fibrillar components. Our research group has studied in a new proposed rodent model the participation of cellular and molecular components in the prostate microenvironment that contributes to cancer progression. Our group adopted the gerbil Meriones unguiculatus as an alternative experimental model for prostate cancer study. This model has presented significant responses to hormonal treatments and to development of spontaneous and induced neoplasias. The data obtained indicate reorganization of type I collagen fibers and reticular fibers, synthesis of new components such as tenascin and proteoglycans, degradation of basement membrane components and elastic fibers and increased expression of metalloproteinases. Fibroblasts that border the region, apparently participate in the stromal reaction. The roles of each of these events, as well as some signaling molecules, participants of neoplastic progression and factors that promote genetic reprogramming during epithelial-stromal transition are also discussed.

EMMPRIN and ADAM12 in prostate cancer: preliminary results of a prospective study

Extracellular metalloproteinase inducer (EMMPRIN) and a disintegrin and metalloproteinase (ADAM12) play a major role in cancer invasion and metastasis owing to the fact that they are directly related to the cell microenvironment and extracellular matrix (ECM) degradation. The aim of this study was to search for an answer to the question "whether the determination of EMMPRIN and ADAM12 values especially in urine may be helpful for the early diagnosis of prostate cancer without employing invasive methods" and also to check whether they may be useful for the determination of the patients with high metastasis risk. Peripheral blood and urine from 66 prostate cancer patients (40 local, 20 locally advanced, 6 metastatic) and 14 healthy controls were evaluated by enzyme-linked immunosorbent assay (ELISA) method. Serum EMMPRIN and ADAM12 values of the patients were seen to be statistically higher than the serum EMMPRIN and ADAM12 values of the healthy controls (p=0.01 and p=0.001, respectively). The urine ADAM12 levels were significantly higher in patients (p=0.013). No significant relationships were found between urine EMMPRIN values of the patients and the healthy controls (p>0.05). Positive correlation between urine EMMPRIN-urine ADAM12 tests was found in total patients group (r=0.683, p=0.001). Our preliminary results revealed that serum EMMPRIN and ADAM12 values and urine ADAM12 values may be useful markers in prostate cancer therapy. Due to the high correlation between these two tests, we are of the opinion that the use of urine ADAM12 in clinic may be sufficient and favorable together with prostate-specific antigen (PSA) for treatment.

Involvement of host stroma cells and tissue fibrosis in pancreatic tumor development in transgenic mice

Introduction

Stroma cells and extracellular matrix (ECM) components provide the pivotal microenvironment for tumor development. The study aimed to evaluate the importance of the pancreatic stroma for tumor development.

Methods

Pancreatic tumor cells were implanted subcutaneously into green fluorescent protein transgenic mice, and stroma cells invading the tumors were identified through immunohistochemistry. Inhibition of tumor invasion by stroma cells was achieved with halofuginone, an inhibitor of TGFβ/Smad3 signaling, alone or in combination with chemotherapy. The origin of tumor ECM was evaluated with species-specific collagen I antibodies and in situ hybridization of collagen α1(I) gene. Pancreatic fibrosis was induced by cerulean injection and tumors by spleen injection of pancreatic tumor cells.

Results

Inhibition of stroma cell infiltration and reduction of tumor ECM levels by halofuginone inhibited development of tumors derived from mouse and human pancreatic cancer cells. Halofuginone reduced the number only of stroma myofibroblasts expressing both contractile and collagen biosynthesis markers. Both stroma myofibroblasts and tumor cells generated ECM that contributes to tumor growth. Combination of treatments that inhibit stroma cell infiltration, cause apoptosis of myofibroblasts and inhibit Smad3 phosphorylation, with chemotherapy that increases tumor-cell apoptosis without affecting Smad3 phosphorylation was more efficacious than either treatment alone. More tumors developed in fibrotic than in normal pancreas, and prevention of tissue fibrosis greatly reduced tumor development.

Conclusions

The utmost importance of tissue fibrosis and of stroma cells for tumor development presents potential new therapy targets, suggesting combination therapy against stroma and neoplastic cells as a treatment of choice.

Biochemical role of the collagen-rich tumour microenvironment in pancreatic cancer progression

PDAC (pancreatic ductal adenocarcinoma) is among the most deadly of human malignances. A hallmark of the disease is a pronounced collagen-rich fibrotic extracellular matrix known as the desmoplastic reaction. Intriguingly, it is precisely these areas of fibrosis in which human PDAC tumours demonstrate increased expression of a key collagenase, MT1-MMP [membrane-type 1 MMP (matrix metalloproteinase); also known as MMP-14]. Furthermore, a cytokine known to mediate fibrosis in vivo, TGF-β1 (transforming growth factor-β1), is up-regulated in human PDAC tumours and can promote MT1-MMP expression. In the present review, we examine the regulation of PDAC progression through the interplay between type I collagen (the most common extracellular matrix present in human PDAC tumours), MT1-MMP and TGF-β1. Specifically, we examine the way in which signalling events through these pathways mediates invasion, regulates microRNAs and contributes to chemoresistance.

Post-translational modifications of the extracellular matrix are key events in cancer progression: opportunities for biochemical marker development

The aim of this review is to discuss the potential usefulness of a novel class of biochemical markers, designated neoepitopes. Neoepitopes are post-translational modifications (PTMs) of proteins and are derived by processes, such as protease cleavage, citrullination, nitrosylation, glycosylation and isomerization. Each PTM results from a specific local physiological or pathobiological process. Identification of each modification to a tissue-specific protein may reveal a unique disease-specific biochemical marker. During cancer metastasis, the host tissue is extensively degraded and replaced by cancer-associated extracellular matrix (ECM) proteins. Furthermore, severe cellular stress and inflammation, caused by cancer, results in generation of PTMs, which will be distributed throughout the ECM. This gives rise to release of protein-specific fragments to the circulation. Here we highlight the importance of remodeling of the ECM in cancer and the generation of PTMs, which may be cancer specific and reflect disease progression; thus having potential for biochemical marker development.

Inhibition of pancreatic stellate cell activation by halofuginone prevents pancreatic xenograft tumor development

OBJECTIVES

Most solid tumors consist of neoplastic and nonneoplastic cells and extracellular matrix components. In the pancreas, activated stellate cells (PSCs) are the source of the extracellular matrix proteins. We evaluated the significance of PSC activation in tumor establishment and development in mouse xenografts.

METHODS

Xenografts were established by implanting human pancreatic cancer cells (MiaPaca-2) subcutaneously or orthotopically by injecting them into the spleen. Fibrosis was induced by cerulein. Collagen level was evaluated by Sirius red staining. Prolyl 4-hydroxylase β and stellate cell activation-associated protein (Cygb/STAP) were determined by immunohistochemistry.

RESULTS

Halofuginone inhibited subcutaneous tumor development implanted with Matrigel and reduced collagen and prolyl 4-hydroxylase β levels. Few tumors, which developed slowly, were observed after MiaPaca-2 implantation without Matrigel. Increase in tumor number and rate of development were observed with addition of PSCs from control pancreas, and further increase was observed when the PSCs were from cerulein-treated mice. Preincubation of the PSCs with halofuginone elicited Cygb/STAP level reduction and tumor growth inhibition. More tumors developed orthotopically in cerulein-treated mice than in controls; this was prevented by halofuginone.

CONCLUSIONS

Extracellular matrix production by activated PSCs is essential for tumor establishment and growth. Thus, inhibition of PSC activation is a viable means of reducing pancreatic tumor development.

Proliferation of myofibroblasts in the stroma of renal oncocytoma

OBJECTIVES

Myofibroblasts are a vital component of stroma of many malignant neoplasms, but it is not yet established whether stromal myofibroblasts also exist in benign tumours such as oncocytoma of the kidney.

MATERIALS AND METHODS

Histomorphological and immunohistochemical analysis of 16 renal oncocytomas diagnosed at Chang Gung Memorial Hospital, Taiwan, has been performed.

RESULTS

Renal oncocytomas were composed of oncocytes, large cells with granular eosinophilic cytoplasm, arranged mostly in sheets, in tubulocystic or combined pattern. Few oncocytes appeared to be undergoing proliferation or apoptosis. MIB-1 and active caspase 3 indices were low, but higher in tumour than in surrounding non-tumour parenchyma (MIB-1: 0.93 +/- 0.09 versus 0.46 +/- 0.07, P < 0.001 and active caspase 3: 0.76 +/- 0.08 versus 0.41 +/- 0.09, P < 0.001). Wnt/beta-catenin signalling was not implicated in this neoplasm, as there was no loss of E-cadherin membranous localization or expression of intranuclear beta-catenin in the cells. Clumps of oncocytes were stained with periodic acid Schiff and had collagen I-, collagen III- and fibronectin-positive, but desmin- and human caldesmon-negative stromas. Importantly, alpha-smooth muscle actin (SMA)-immunostaining established the myofibroblastic nature of many of the stromal cells. Some of the myofibroblasts were also positive for MIB-1, indicating a proliferative role for them in the stroma.

CONCLUSIONS

Renal oncocytomas were composed of two independent compartments: benign oncocytes and pronounced fibrotic stroma, which consisted of proliferating myofibroblasts (SMA- and MIB-1-positive) which were associated with excessive deposition of extracellular matrix (periodic acid Schiff-component, collagen I-, collagen III- and fibronectin-positive, and desmin- and human caldesmon-negative).

Myofibroblasts in pulmonary and brain metastases of alveolar soft-part sarcoma: a novel target for treatment?

Alveolar soft-part sarcoma (ASPS) is a rare neoplasm with chromosomal translocation that results in ASPL-TFE3 fusion. It is a slow-growing lesion associated with a high incidence of pulmonary and brain metastases indicating poor survival. We demonstrated that the ASPS metastases include also stromal myofibroblasts. These cells proliferate, express smooth-muscle genes, and synthesize extracellular matrix proteins, all of which are characteristics of activated myofibroblasts. The tumor cells also exhibited stromal components such as transforming growth factor beta (TGFbeta)-dependent, hypoxia-regulated cytoglobin (stellate cell activation association protein, cytg/STAP) and prolyl 4-hydroxylase, a collagen cross-linking enzyme. The pulmonary ASPS myofibroblasts synthesize serum response factor (SRF), a repressor of Smad3-mediated TGFbeta signaling essential for myofibroblast differentiation and Smad3. The phosphorylated active Smad3 was found mostly in the tumor cells. The brain tumor cells express cytg/STAP, but in contrast to the lung metastases, they also express SRF, Smad3, and phospho-Smad3. Halofuginone, an inhibitor of myofibroblasts' activation and Smad3 phosphorylation, inhibited tumor development in xenografts derived from renal carcinoma cells harboring a reciprocal ASPL-TFE3 fusion transcript. This inhibition was associated with the inhibition of TGFbeta/SRF signaling, with the inhibition of myofibroblasts' activation, and with the complete loss in TFE3 synthesis by the tumor cells. These results suggest that the myofibroblasts may serve as a novel target for treatment of ASPS metastases.

The tandem PDZ domains of syntenin promote cell invasion

Syntenin is a tandem PDZ protein that has recently been shown to be overexpressed in several cancer cells and tissues, and that might play an active role in tumor cell invasion and metastasis. Here we show that overexpression of the tandem PDZ domains of syntenin in non-invasive cells is necessary and sufficient to stimulate these cells to invade a collagen I matrix, and this effect can be regulated by ligand binding to the PDZ domains. Furthermore, we show that syntenin-induced invasion requires signaling through ras, rho and PI3K/MAPK signaling pathways and involves changes in cell-cell adhesion. Inversely, when we used RNA interference to inhibit syntenin expression in different invasive cancer cell lines, we observed a drastically decreased ability of these cells to migrate and invade into collagen type I or Matrigel. RNAi-treated cells also show increased cell aggregation, indicating that syntenin is important for cell-cell adhesion in epithelial cells. Together, these results suggest that downregulation of syntenin by RNA interference could provide a means of inhibiting tumor invasion and possibly metastasis in different cancers, and point to syntenin as a potential cancer biomarker and drug target.

Inhibition of fibroblast to myofibroblast transition by halofuginone contributes to the chemotherapy-mediated antitumoral effect

Stromal myofibroblasts play an important role in tumor progression. The transition of fibroblasts to myofibroblasts is characterized by expression of smooth muscle genes and profuse synthesis of extracellular matrix proteins. We evaluated the efficacy of targeting fibroblast-to-myofibroblast transition with halofuginone on tumor progression in prostate cancer and Wilms' tumor xenografts. In both xenografts, low doses of halofuginone treatment, independent of the route of administration, resulted in a trend toward inhibition in tumor development. Moreover, halofuginone synergizes with low dose of docetaxel in prostate cancer and vincristine and dactinomycin in Wilms' tumor xenografts, resulting in significant reduction in tumor volume and weight comparable to the effect observed by high doses of the respective chemotherapies. In prostate cancer and Wilms' tumor xenografts, halofuginone, but not the respective chemotherapies, inhibited the synthesis of collagen type I, alpha-smooth muscle actin, transgelin, and cytoglobin, all of which are characteristics of activated myofibroblasts. Halofuginone, as the respective chemotherapies, increased the synthesis of Wilms' tumor suppressor gene product (WT-1) and prostate apoptosis response gene-4 (Par-4), resulting in apoptosis/necrosis. These results suggest that targeting the fibroblast-to-myofibroblast transition with halofuginone may synergize with low doses of chemotherapy in achieving a significant antitumoral effect, avoiding the need of high-dose chemotherapy and its toxicity without impairing treatment efficacy.

Molecular basis for dissimilar nuclear trafficking of the actin-bundling protein isoforms T- and L-plastin

T- and L-plastin are highly similar actin-bundling proteins implicated in the regulation of cell morphology, lamellipodium protrusion, bacterial invasion and tumor progression. We show that T-plastin localizes predominantly to the cytoplasm, whereas L-plastin distributes between nucleus and cytoplasm in HeLa or Cos cells. T-plastin shows nuclear accumulation upon incubation of cells with the CRM1 antagonist leptomycin B (LMB). We identified a Rev-like nuclear export sequence (NES) in T-plastin that is able to export an otherwise nuclear protein in an LMB-dependent manner. Deletion of the NES promotes nuclear accumulation of T-plastin. Mutation of residues L17, F21 or L26 in the T-plastin NES inhibits nuclear efflux. L-plastin harbors a less conserved NES and lacks the F21 T-plastin residue. Insertion of a Phe residue in the L-plastin NES specifically enhances its export activity. These findings explain why both isoforms exhibit specific distribution patterns in eukaryotic cells.

Alpha-catenin is required for IGF-I-induced cellular migration but not invasion in human colonic cancer cells

The mechanisms by which growth factors cooperate with cell adhesion molecules to modulate epithelial cell motility remain poorly understood. Here, we investigated the role of the E-cadherin/catenin complex in insulin-like growth factor (IGF-I)-dependent cell migration and invasion. We used variants of the HCT-8 colon cancer family that differ in their expression of alphaE-catenin, an intracellular molecule that links the E-cadherin/catenin complex to the actin cytoskeleton. Migration was determined using a monolayer wound model and cell invasion by the penetration of the cells into type-I collagen gels. We showed that alpha-catenin-deficient cells were not able to migrate in cohort upon IGF-I stimulation. Transfection of these cells with alpha-catenin isoforms (alphaN- or alphaT-catenin) restored migratory response IGF-I. These results suggest that alpha-catenins are involved in the signal issued from the E-cadherin/catenin complex to regulate IGF-I-stimulated migration. In contrast, IGF-I promoted invasion of both alpha-catenin-deficient and alpha-catenin-expressing cells, indicating that alpha-catenin did not participate in the regulation of IGF-I-induced invasion. Inhibition of E-cadherin function by treatment with MB-2 monoclonal antibodies inhibited both IGF-I-dependent cell migration and invasion. Taken together, our results indicate that functional alpha-catenin is essential for migration but not for invasion, while E-cadherin is involved in both phenomena.

Clinical, cellular, and molecular aspects of cancer invasion

Invasion causes cancer malignancy. We review recent data about cellular and molecular mechanisms of invasion, focusing on cross-talk between the invaders and the host. Cancer disturbs these cellular activities that maintain multicellular organisms, namely, growth, differentiation, apoptosis, and tissue integrity. Multiple alterations in the genome of cancer cells underlie tumor development. These genetic alterations occur in varying orders; many of them concomitantly influence invasion as well as the other cancer-related cellular activities. Examples discussed are genes encoding elements of the cadherin/catenin complex, the nonreceptor tyrosine kinase Src, the receptor tyrosine kinases c-Met and FGFR, the small GTPase Ras, and the dual phosphatase PTEN. In microorganisms, invasion genes belong to the class of virulence genes. There are numerous clinical and experimental observations showing that invasion results from the cross-talk between cancer cells and host cells, comprising myofibroblasts, endothelial cells, and leukocytes, all of which are themselves invasive. In bone metastases, host osteoclasts serve as targets for therapy. The molecular analysis of invasion-associated cellular activities, namely, homotypic and heterotypic cell-cell adhesion, cell-matrix interactions and ectopic survival, migration, and proteolysis, reveal branching signal transduction pathways with extensive networks between individual pathways. Cellular responses to invasion-stimulatory molecules such as scatter factor, chemokines, leptin, trefoil factors, and bile acids or inhibitory factors such as platelet activating factor and thrombin depend on activation of trimeric G proteins, phosphoinositide 3-kinase, and the Rac and Rho family of small GTPases. The role of proteolysis in invasion is not limited to breakdown of extracellular matrix but also causes cleavage of proinvasive fragments from cell surface glycoproteins.