Vitronectin secretion by hepatic and non-hepatic human cancer cells

Key therapeutic targets implicated at the early stage of hepatocellular carcinoma identified through machine-learning approaches

Hepatocellular carcinoma (HCC) is the most frequent type of primary liver cancer. Early-stage detection plays an essential role in making treatment decisions and identifying dominant molecular mechanisms. We utilized machine learning algorithms to find significant mRNAs and microRNAs (miRNAs) at the early and late stages of HCC. First, pre-processing approaches, including organization, nested cross-validation, cleaning, and normalization were applied. Next, the t-test/ANOVA methods and binary particle swarm optimization were used as a filter and wrapper method in the feature selection step, respectively. Then, classifiers, based on machine learning and deep learning algorithms were utilized to evaluate the discrimination power of selected features (mRNAs and miRNAs) in the classification step. Finally, the association rule mining algorithm was applied to selected features for identifying key mRNAs and miRNAs that can help decode dominant molecular mechanisms in HCC stages. The applied methods could identify key genes associated with the early (e.g., Vitronectin, thrombin-activatable fibrinolysis inhibitor, lactate dehydrogenase D (LDHD), miR-590) and late-stage (e.g., SPRY domain containing 4, regucalcin, miR-3199-1, miR-194-2, miR-4999) of HCC. This research could establish a clear picture of putative candidate genes, which could be the main actors at the early and late stages of HCC.

Differentially expressed glycoproteins in pre- and post-digital rectal examination urine samples for detecting aggressive prostate cancer

Urinary glycoproteins associated with aggressive prostate cancer (AG-PCa) were previously reported using post-digital rectal examination (DRE) urine specimens. To explore the potential of using pre-DRE urine specimens for detecting AG-PCa, we compared glycoproteins between pre- and post-DRE urine specimens, verified the previously identified post-DRE AG-PCa-associated urinary glycoproteins in pre-DRE urine specimens, and explored potential new glycoproteins for AG-PCa detection in pre-DRE urine specimens. Quantitative glycoproteomic data were acquired for 154 pre-DRE urine specimens from 41 patients with no cancer at biopsy, 48 patients with non-AG-PCa (Gleason score = 6), and 65 patients with AG-PCa (Gleason score 7 or above). Compared to glycopeptides from the post-DRE urine data, humoral immunity-related proteins were enriched in pre-DRE urine samples, whereas cell mediated immune response proteins were enriched in post-DRE urine samples. Analyses of AG-PCa-associated glycoproteins from pre-DRE urine revealed that the three urinary glycoproteins, prostate-specific antigen (PSA), prostatic acid phosphatase (ACPP), and CD97 antigen (CD97) that were previously identified in post-DRE urine samples, were also observed as AG-PCa associated glycoproteins in pre-DRE urine. In addition, we identified three new glycoproteins, fibrillin 1 (FBN1), vitronectin (VTN), and hemicentin 2 (HMCN2), to be potentially associated with AG-PCa in pre-DRE urine specimens. In summary, glycoprotein profiles differ between pre- and post-DRE urine specimens. The identified AG-PCa-associated glycoproteins may be further evaluated in large cohort of pre-DRE urine specimens for detecting clinically significant PCa.

Vitronectin as a molecular player of the tumor microenvironment in neuroblastoma

Background

Vitronectin is a multifunctional glycoprotein known in several human tumors for its adhesive role in processes such as cell growth, angiogenesis and metastasis. In this study, we examined vitronectin expression in neuroblastoma to investigate whether this molecule takes part in cell-cell or cell-extracellular matrix interactions that may confer mechanical properties to promote tumor aggressiveness.

Methods

We used immunohistochemistry and image analysis tools to characterize vitronectin expression and to test its prognostic value in 91 neuroblastoma patients. To better understand the effect of vitronectin, we studied its in vitro expression using commercial neuroblastoma cell lines and in vivo using intra-adrenal gland xenograft models by immunohistochemistry.

Results

Digital image analysis allowed us to associate vitronectin staining intensity and location discriminating between territorial vitronectin and interterritorial vitronectin expression patterns. High territorial vitronectin expression (strong staining associated with pericellular and intracellular location) was present in tumors from patients with metastatic undifferentiating neuroblastoma, that were MYCN amplified, 11q deleted or with segmental chromosomal profiles, in the high-risk stratification group and with high genetic instability. In vitro studies confirmed that vitronectin is expressed in tumor cells as small cytoplasmic dot drops. In vivo experiments revealed tumor cells with high and dense cytoplasmic vitronectin expression.

Conclusions

These findings highlight the relevance of vitronectin in neuroblastoma tumor biology and suggest its potential as a future therapeutic target in neuroblastoma.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5693-2) contains supplementary material, which is available to authorized users.

Diagnostic and prognostic roles of serum vitronectin in hepatitis B-related hepatocellular carcinoma

BACKGROUND

Vitronectin (VN) might be involved in the progression of hepatocellular carcinoma (HCC).

OBJECTIVE

This study was designed to evaluate the diagnostic and prognostic value of serum vitronectin among HCC patients.

METHODS

A total of 105 patients with HCC, 91 with liver cirrhosis, 102 with chronic hepatitis, and 100 healthy subjects were recruited. Serum VN and alpha-fetoprotein (AFP) levels were measured.

RESULTS

Serum VN levels were significantly higher in HCC patients than in the other groups. Based on area under receiver operating characteristic curve, serum VN had similar diagnostic value, compared with serum AFP, in distinguishing HCC from the groups, and also improved the diagnostic value of AFP alone. Serum VN levels were associated with the degree of histological differentiation, multiple foci, vascular tumor thrombosis and tumor node metastasis stage. Serum VN was an independent predictor for early recurrence and disease-free survival. Moreover, serum VN possessed similar prognostic predictive performance as compared to serum AFP and also significantly enhanced the prognostic value of AFP alone.

CONCLUSIONS

Elevated serum VN levels represented high diagnostic value and had close relation to clinicopathological factors and early recurrence, suggesting that serum VN might be a useful diagnostic and prognostic marker for HCC.

Inhibition of the Membrane Attack Complex by Dengue Virus NS1 through Interaction with Vitronectin and Terminal Complement Proteins

Dengue virus (DENV) infects millions of people worldwide and is a major public health problem. DENV nonstructural protein 1 (NS1) is a conserved glycoprotein that associates with membranes and is also secreted into the plasma in DENV-infected patients. The present study describes a novel mechanism by which NS1 inhibits the terminal complement pathway. We first identified the terminal complement regulator vitronectin (VN) as a novel DENV2 NS1 binding partner by using a yeast two-hybrid system. This interaction was further assessed by enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) assay. The NS1-VN complex was also detected in plasmas from DENV-infected patients, suggesting that this interaction occurs during DENV infection. We also demonstrated that the DENV2 NS1 protein, either by itself or by interacting with VN, hinders the formation of the membrane attack complex (MAC) and C9 polymerization. Finally, we showed that DENV2, West Nile virus (WNV), and Zika virus (ZIKV) NS1 proteins produced in mammalian cells inhibited C9 polymerization. Taken together, our results points to a role for NS1 as a terminal pathway inhibitor of the complement system.

IMPORTANCE

Dengue is the most important arthropod-borne viral disease nowadays and is caused by dengue virus (DENV). The flavivirus NS1 glycoprotein has been characterized functionally as a complement evasion protein that can attenuate the activation of the classical, lectin, and alternative pathways. The present study describes a novel mechanism by which DENV NS1 inhibits the terminal complement pathway. We identified the terminal complement regulator vitronectin (VN) as a novel DENV NS1 binding partner, and the NS1-VN complex was detected in plasmas from DENV-infected patients, suggesting that this interaction occurs during DENV infection. We also demonstrated that the NS1-VN complex inhibited membrane attack complex (MAC) formation, thus interfering with the complement terminal pathway. Interestingly, NS1 itself also inhibited MAC activity, suggesting a direct role of this protein in the inhibition process. Our findings imply a role for NS1 as a terminal pathway inhibitor of the complement system.

Regulation of complement and modulation of its activity in monoclonal antibody therapy of cancer

The complement system is a powerful tool of the innate immune system to eradicate pathogens. Both in vitro and in vivo evidence indicates that therapeutic anti-tumor monoclonal antibodies (mAbs) can activate the complement system by the classical pathway. However, the contribution of complement to the efficacy of mAbs is still debated, mainly due to the lack of convincing data in patients. A beneficial role for complement during mAb therapy is supported by the fact that cancer cells often upregulate complement-regulatory proteins (CRPs). Polymorphisms in various CRPs were previously associated with complement-mediated disorders.

In this review the role of complement in anti-tumor mAb therapy will be discussed with special emphasis on strategies aiming at modifying complement activity. In the future, clinical efficacy of mAbs with enhanced effector functions together with comprehensive analysis of polymorphisms in CRPs in mAb-treated patients will further clarify the role of complement in mAb therapy.

Integrin αvβ3 promotes vitronectin gene expression in human ovarian cancer cells by implicating rel transcription factors

We previously showed that integrin αvβ3 expression upon engagement by its major ligand vitronectin (VN) correlated with enhanced human ovarian cancer cell adhesion, motility, and proliferation, by triggering intracellular signaling events, ultimately leading to altered gene expression. In the present study, we characterized cellular VN expression as a function of αvβ3 and noticed significant upregulation of VN protein which was reflected by elevated VN gene transcription. In order to identify specific transcription factors involved in the αvβ3-regulatory effect on VN, we generated different VN promoter mutants. We noticed that disruption of the DNA consensus motif for Rel proteins did not only prominently reduce VN promoter activity but, moreover, led to a loss of responsiveness to αvβ3, suggesting a crucial role of Rel proteins in αvβ3-provoked VN induction. In cell migration studies, we confirmed increased cell motility as a function of αvβ3/VN which was further enhanced by raising cellular Rel transcription factor levels. Thus, the data of the present study elucidated a positive feedback regulatory loop on VN expression by αvβ3 implicating transcription factors of the Rel family. Hence by altering the composition of the extracellular matrix upon additional VN synthesis and deposition, tumor cells might be enabled to modulate their surrounding reactive microenvironment towards enhanced αvβ3/VN-interactions and, consequently, intrinsic intracellular signaling events affecting cancer progression.

alphavbeta3 and vitronectin expression by normal ovarian surface epithelial cells: role in cell adhesion and cell proliferation

The alphavbeta3 integrin and its ligand vitronectin are expressed by differentiated epithelial ovarian carcinomas and carcinoma cell lines in culture. Moreover, alphavbeta3/vitronectin interaction influences adhesion and migration of ovarian carcinoma cells in culture. For a better understanding of the behavior of these carcinomas, it appeared necessary to study the characteristics of their normal counterpart, the ovarian surface epithelium (OSE). The present study showed that normal cultured human OSE cells, like the carcinoma cells, have the ability to synthesize vitronectin. The vitronectin receptor, alphavbeta3 integrin, is also expressed by OSE cells and is localized in focal contacts close to paxillin, a focal contact-specific protein, and p125(FAK), a cytoskeletal and signaling molecule. This localization suggested an active participation of the integrin in the adhesion and/or proliferation of OSE cells. Indeed, the use of a blocking antibody demonstrated that alphav integrins promote OSE cell adhesion on vitronectin but not on fibronectin and that these integrins are required for maximal proliferative activity. The results suggest a role of the alphavbeta3/vitronectin system in normal OSE physiology and demonstrate that the expression of this system by well-differentiated ovarian carcinomas reflects the retention of normal cell properties.

The human retina and retinal pigment epithelium are abundant sources of vitronectin mRNA

Vitronectin (Vn), a multifunctional plasma protein synthesized primarily in the liver, is often present as a component of the extracellular plaques and deposits that accompany various age-related human diseases. Recently, we reported that Vn is also a prominent molecular constituent of drusen, the extracellular deposits associated with age-related macular degeneration (AMD) (1). The cellular source(s) of the Vn in drusen, as well as in these other plaques and deposits, remains uncertain. In this study, we used real-time quantitative RT-PCR to measure the relative levels of Vn mRNA in the cells and tissues that lie in close proximity to drusen. The results confirm that the human liver is an abundant source of Vn mRNA. Levels of Vn mRNA in kidney, lung, and fetal or adult brain are <3% of those in liver. Remarkably, mean Vn mRNA levels in the neural retina significantly exceed those in brain and represent close to 40% of the Vn mRNA value measured in human liver. Substantial levels of Vn mRNA are also present in the adjacent retinal pigment epithelium (RPE). These results identify the neural retina, for the first time, as an abundant source of Vn mRNA. They also suggest that both the neural retina and RPE are potent biosynthetic sources of Vn in humans, and potentially significant local contributors to the Vn that accumulates in drusen.

Vitronectin is a constituent of ocular drusen and the vitronectin gene is expressed in human retinal pigmented epithelial cells

Age-related macular degeneration (AMD) leads to dysfunction and degeneration of retinal photoreceptor cells. This disease is characterized, in part, by the development of extracellular deposits called drusen. The presence of drusen is correlated with the development of AMD, although little is known about drusen composition or biogenesis. Drusen form within Bruch's membrane, a stratified extracellular matrix situated between the retinal pigmented epithelium and choriocapillaris. Because of this association, we sought to determine whether drusen contain known extracellular matrix constituents. Antibodies directed against a battery of extracellular matrix molecules were screened on drusen-containing sections from human donor eyes, including donors with clinically documented AMD. Antibodies directed against vitronectin, a plasma protein and extracellular matrix component, exhibit intense and consistent reactivity with drusen; antibodies to the conformationally distinct, heparin binding form of human vitronectin are similarly immunoreactive. No differences in vitronectin immunoreactivity between hard and soft drusen, or between macular and extramacular regions, have been observed. RT-PCR analyses revealed that vitronectin mRNA is expressed in the retinal pigmented epithelium (RPE)-choroidal complex and cultured RPE cells. These data document that vitronectin is a major constituent of human ocular drusen and that vitronectin mRNA is synthesized locally. Based on these data, we propose that vitronectin may participate in the pathogenesis of AMD.

Human ovarian adenocarcinoma cells synthesize vitronectin and use It to organize their adhesion

Extracellular matrix components and integrin receptors are frequently altered in cancer, including ovarian adenocarcinoma. Vitronectin (Vn) is a matrix protein mainly synthesized by liver cells; it is present in normal ovarian surface epithelium and differentiated ovarian adenocarcinoma, but is frequently undetectable in undifferentiated carcinoma (F. Carreiras et al., 1996, Gynecol Oncol 62:260-267). Wondering about the cellular origin of Vn in ovarian carcinoma, we searched for evidence of Vn synthesis by these tumors. We demonstrated that three human ovarian adenocarcinoma cell lines were able to synthesize Vn, as revealed by the presence of Vn mRNA and the protein. The Vn matrix promotes adhesion of ovarian tumor cells through alphav integrins. Moreover, during in vitro growth, Vn is progressively organized into a particular pattern in combination with the recruitment of alphav into focal contacts. Our results suggest that Vn synthesis may participate in ovarian adenocarcinoma cell biology and raise the possibility that altered expression of Vn in some ovarian carcinomas could result from a defect in Vn synthesis.

Cloning and characterization of a novel zinc finger protein that associates with nuclear matrix

We have recently reported that the nuclei of B16 melanoma cells are intensely stained with anti-rat vitronectin (Vn) antibody, which reacts with both mouse and rat Vn. In the present study, we characterized the protein immunoreactive with the antibody using NIH3T3 cells, whose nuclei were also stained with the antibody. Western blot analysis showed that a protein with an approximate molecular weight of 75 kDa (p75), which was distinct from Vn, existed in the nuclear fraction, and, more specifically, in the nuclear matrix fraction, of NIH3T3 cells. Screening of an NIH3T3 cDNA library resulted in the isolation of a nearly full-length cDNA clone encoding p75. A database search revealed that the cDNA represents a novel gene. The deduced amino acid sequence showed that the protein is 580 amino acids long and contains two C2H2-type zinc finger motifs and glutamic acid-rich domains in the C-terminal region. When a fusion protein of green fluorescence protein and p75 was expressed in NIH3T3 cells, fluorescence was preferentially observed in the nuclei, demonstrating that the protein has a nuclear localization signal. The p75 protein, termed ZAN75, exhibited DNA-binding activity in a zinc-dependent manner. Southern blot analysis demonstrated that the ZAN75 gene exists in a single copy in the mouse genome and that a closely related gene is also present in chicken, rat, and human. Northern blot analysis showed that the ZAN75 gene is ubiquitously expressed in adult mouse tissues. In the cell cycle of NIH3T3 cells, expression was low in the G0/G1 phase, increased during the G1 phase, and persisted during the S and G2/M phases, suggesting that ZAN75 plays a role in regulating cell growth.

Serum clusterin and vitronectin in alcoholic cirrhosis

Clusterin and vitronectin are multifunctional regulatory proteins which both serve as complement lysis inhibitors. Previous data have strongly suggested that serum vitronectin is mainly produced in the liver, whereas the biosynthetic origin for serum clusterin has not been determined. In the present study we aimed to determine the role of the liver in producing these proteins and to evaluate the proteins as possible markers of liver failure. We therefore quantified clusterin and vitronectin in serum from patients suffering from alcoholic liver cirrhosis (n = 83), and in serum-free culture supernatants from the hepatoma cell line HepG2. The median clusterin concentration was 0.20 g/l in cirrhosis and 0.37 g/l in the controls, whereas corresponding vitronectin values were 0.19 and 0.26 g/l, respectively. The concentration of both proteins showed significant correlation (p < 0.0001) with disease severity and with established plasma markers of hepatic synthetic function, such as albumin and prothrombin complex. The clusterin level, but not the vitronectin level, correlated with survival (p = 0.005). The rates of synthesis of clusterin, vitronectin and C3 from HepG2 cells were 0.02, 0.21 and 1.9 micrograms/10(6) cells/24 h, respectively. From the present data we conclude that clusterin (as vitronectin and C3) is mainly produced in the liver and may be a useful marker in the evaluation of severity of liver disease and prognosis of patients with alcoholic cirrhosis.

Regulation of plasminogen activator inhibitor activity by plasmin in endothelial cells

The fibrinolytic activity in endothelial cells was regulated by balance of plasminogen activators and plasminogen activator inhibitors. Plasmin can specifically inhibit the biosynthesis of tissue-type plasminogen activator (t-PA), but not plasminogen activator inhibitor, type 1 (PAI-1) in endothelial cells. The PAI activity in the conditioned medium of endothelial cells was low and remained constant in 24 hours. However, the PAI activity in the conditioned medium of the plasmin-pretreated cells increased linearly in 24 hours. Pretreatment with protein kinase C inhibitors, H-7 or staurosporine, partially suppressed the PAI activity induced by plasmin. Pretreatment of endothelial cells with a G-protein inhibitor pertussis toxin resulted in an inhibition of the plasmin-induced PAI activity. The phospholipase A2 inhibitor mepacrine specifically eliminated the effect of plasmin stimulation on PAI activity. Cyclooxygenase and lipoxygenase inhibitors also partially inhibited the plasmin-stimulated PAI activity in endothelial cells. All these inhibitors did not affect the biosynthesis of the PAI-1 antigen in the presence or absence of plasmin. The results indicate that plasmin increased the PAI activity of endothelial cells via pathways in which protein kinase C, G protein, and phospholipase A2 may be involved.

Characterization of matrix-degrading proteinases and their inhibitors secreted by human gynecological carcinoma cells

Matrix-degrading proteinases secreted by tumor cells play crucial roles in tumor cell invasion and metastasis. Serum-free conditioned media of 7 human gynecological carcinoma cell lines were examined for proteinases and their inhibitors by using gelatin zymography, reverse zymography and immunoblotting. All of three ovarian adenocarcinoma cell lines secreted urokinase-type plasminogen activator. Among them, a mucinous cystadenocarcinoma cell line also secreted tissue-type plasminogen activator, plasmin-like enzyme and trypsinogen. On the other hand, two ovarian undifferentiated carcinoma cell lines mainly secreted glatinase A or B. A choriocarcinoma cell line secreted multiple metalloproteinases in the highest amount, whereas an endometrial adenocarcinoma cell line (HEC-1) derived from an early clinical stage hardly secreted any gelatinolytic enzyme. The five high proteinases producers hardly secreted the corresponding inhibitors, such as tissue inhibitor of metalloproteinases (TIMP)-1, -2 or plasminogen activator inhibitor-1. In contrast to these highly malignant cell lines, a poor proteinase producer, HEC-1, secreted a large amount of TIMPs. Therefore, an enhanced proteolytic tendency appears to be associated with gynecological cancer cells established from highly malignant tumors.

Cerebral microenvironment influences expression of the vitronectin gene in astrocytic tumors

Expression of the vitronectin gene was detected in advanced human astrocytoma by in situ hybridization, whereas vitronectin mRNA was undetectable in low grade tumors or in normal adult brain, indicating that vitronectin is a marker of malignant astrocytoma. We established a model of human astrocytoma by transplanting U-251MG human astrocytoma cells intracerebrally into acid mice (C.B.17 severe combined immunodeficient mice). In this model, tumors progressed rapidly and vitronectin mRNA was preferentially detected at the invading tumor margins, i.e. where tumor cells were adjacent to the normal brain tissue. Surprisingly, when U-251MG cells were injected subcutaneously into scid mice, vitronectin mRNA was undetectable throughout the tumor. Moreover, vitronectin mRNA or protein could not be detected among these cells in culture under a wide variety of growth conditions. These findings demonstrate that the cerebral microenvironment influences the expression of the vitronectin gene in malignant astrocytoma. Importantly, the vitronectin binding integrins alpha v beta 3 and alpha v beta 5 localized to distinct sites within these tumors, with beta 3 mRNA synthesized among invading cells, and alpha v and beta 5 mRNAs detected throughout the tumor. In vitro, both of these receptors were capable of promoting adhesion and invasion of astrocytoma cells on a vitronectin substratum. These findings implicate the expression of the vitronectin gene as a contributing factor to the biological behavior of astrocytomas within the cerebral microenvironment.