Osteonectin/SPARC is overexpressed in human hepatocellular carcinoma

GP60 and SPARC as albumin receptors: key targeted sites for the delivery of antitumor drugs

Albumin is derived from human or animal blood, and its ability to bind to a large number of endogenous or exogenous biomolecules makes it an ideal drug carrier. As a result, albumin-based drug delivery systems are increasingly being studied. With these in mind, detailed studies of the transport mechanism of albumin-based drug carriers are particularly important. As albumin receptors, glycoprotein 60 (GP60) and secreted protein acidic and rich in cysteine (SPARC) play a crucial role in the delivery of albumin-based drug carriers. GP60 is expressed on vascular endothelial cells and enables albumin to cross the vascular endothelial cell layer, and SPARC is overexpressed in many types of tumor cells, while it is minimally expressed in normal tissue cells. Thus, this review supplements existing articles by detailing the research history and specific biological functions of GP60 or SPARC and research advances in the delivery of antitumor drugs using albumin as a carrier. Meanwhile, the deficiencies and future perspectives in the study of the interaction of albumin with GP60 and SPARC are also pointed out.

Prognostic Significance of SPARC Expression in Breast Cancer: A Meta-Analysis and Bioinformatics Analysis

Secreted protein, acidic and rich in cysteine (SPARC, also known as osteonectin), is a small molecule glycoprotein associated with cell secretions. The purpose of our research is to clarify the clinicopathological and prognostic significance of SPARC expression in breast cancer. In this study, we performed a meta-analysis and bioinformatics analysis using the PubMed, Web of Science, Wanfang Data, and CNKI databases. The meta-analysis showed that SPARC expression was elevated in breast cancer tissue, compared with normal tissue, while SPARC expression in tumor stromal cells was higher than that of tumor cells. The expression of SPARC was positively correlated with histological grade and TNM staging. The Kaplan-Meier plotter showed that low SPARC expression was negatively correlated with the overall, postprogression, and distant metastasis survival rates of patients. According to Oncomine database, SPARC expression was upregulated in breast cancer than normal tissues. In TCGA database, univariate analysis showed that lymph node metastasis, distant metastasis, and TNM staging were negatively correlated with patient prognosis in breast cancers. Cox multivariate analysis showed that age, lymph node metastasis, distant metastasis, and TNM staging were important factors affecting the survival time of breast cancer patients. SPARC expression can be employed as a good indicator of prognosis of breast cancer patients, which will provide new methods and ideas of preventive treatment.

Perspective: Why and How Ubiquitously Distributed, Vascular-Associated, Pluripotent Stem Cells in the Adult Body (vaPS Cells) Are the Next Generation of Medicine

A certain cell type can be isolated from different organs in the adult body that can differentiate into ectoderm, mesoderm, and endoderm, providing significant support for the existence of a certain type of small, vascular-associated, pluripotent stem cell ubiquitously distributed in all organs in the adult body (vaPS cells). These vaPS cells fundamentally differ from embryonic stem cells and induced pluripotent stem cells in that the latter possess the necessary genetic guidance that makes them intrinsically pluripotent. In contrast, vaPS cells do not have this intrinsic genetic guidance, but are able to differentiate into somatic cells of all three lineages under guidance of the microenvironment they are located in, independent from the original tissue or organ where they had resided. These vaPS cells are of high relevance for clinical application because they are contained in unmodified, autologous, adipose-derived regenerative cells (UA-ADRCs). The latter can be obtained from and re-applied to the same patient at the point of care, without the need for further processing, manipulation, and culturing. These findings as well as various clinical examples presented in this paper demonstrate the potential of UA-ADRCs for enabling an entirely new generation of medicine for the benefit of patients and healthcare systems.

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

Secreted protein acidic and rich in cysteine gene variants: Impact on susceptibility and survival of hepatocellular carcinoma patients

BACKGROUND AND AIM

Secreted protein acidic and rich in cysteine (SPARC) is a glycoprotein involved in extracellular matrix remodeling, which regulates cell growth. It could be involved in hepatic fibrogenesis related to chronic inflammations, hepatocellular carcinoma (HCC) angiogenesis, and tumor progression. We aimed to study the expressions of single nucleotide polymorphisms in the SPARC gene and their impact on susceptibility and survival of HCC patients.

METHODS

We conducted a case-control study on 200 HCC patients and 50 matched healthy controls. All patients were subjected to laboratory investigations, ultrasound, and real-time polymerase chain reaction to detect the genetic polymorphisms (rs3210714, rs11950384, and rs7719521) in the SPARC gene in the blood.

RESULTS

One hundred sixty (80%) patients were men with a mean age of 43 years. The SPARC gene showed a significant higher prevalence of rs3210714 mutation (i.e. AA or AG) and a significant lower prevalence of rs11950384 mutation (i.e. AA or AC) among HCC patients in comparison with controls (83% vs 22%, P ≤ 0.001) and (65.5 vs 86%, P = 0.005), respectively, while rs7719521 mutation did not reach significance. On univariate and multivariate analyses, elder age and having at least one copy of the mutant rs3210714 were associated with a significantly increased risk of HCC (P < 0.001 for both), whereas the presence of at least one copy of the mutant rs11950384 carried a significantly reduced risk of having HCC (P < 0.01). Overall survival did not differ significantly between any of the SPARC gene mutation groups.

CONCLUSIONS

The SPARC gene polymorphisms had a diverse impact on the susceptibility of HCC due to its ability to inhibit or promote tumor progression. SPARC gene polymorphisms were not related to survival of our HCC patients, and probably, this needs further analysis of other SPARC gene nucleotides.

New cancer cases in France in 2015 attributable to infectious agents: a systematic review and meta-analysis

To provide an assessment of the burden of cancer in France in 2015 attributable to infectious agents. A systematic literature review in French representative cancer cases series was undertaken of the prevalence of infectious agents with the major associated cancer types. PubMed was searched for original studies published up to September 2016; random-effects meta-analyses were performed. Cancer incidence data were obtained from the French Cancer Registries Network, thereby allowing the calculation of national incidence estimates. The number of new cancer cases attributable to infectious agents was calculated using population-attributable fractions according to published methods. Of the 352,000 new cancer cases in France in 2015, 14,336 (4.1% of all new cancer cases) were attributable to infectious agents. The largest contributors were human papillomavirus (HPV) and Helicobacter pylori, responsible for 6333 and 4406 new cancer cases (1.8 and 1.3% of all new cancer cases) respectively. Infectious agents caused a non-negligible number of new cancer cases in France in 2015. Most of these cancers were preventable. The expansion of vaccination (i.e., for hepatitis B virus and HPV) and screen-and-treat programs (for HPV and hepatitis C virus, and possibly for H. pylori) could greatly reduce this cancer burden.

Expression and significance of secreted protein acidic and rich in cysteine in human osteosarcoma

Osteosarcoma is the most common primary malignancy of bone, and is a high-grade malignant mesenchymal tumor with high recurrence and metastatic rates. Increased expression of secreted protein, acidic and rich in cysteine (SPARC) indicates poor prognosis in a number of malignances. However, the expression level of SPARC in human osteosarcoma and its associated mechanism remains unclear. To analyze the expression of SPARC in human osteosarcoma and its potential application in the diagnosis and treatment of osteosarcoma, the clinical records and samples of 20 cases of osteosarcoma were collected. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis applied to detect SPARC expression levels in osteosarcoma tissues, with normal bone tissue as control. Immunofluorescence detection was used to examine the distribution of SPARC. The association between SPARC level and clinical factors was analyzed. RT-qPCR (P=0.002) indicated that the SPARC level in osteosarcoma tissues was significantly increased compared with that in normal tissues. Immunofluorescence detection indicated that SPARC was widely distributed in tumor tissues. SPARC protein expression level was positively associated with lung metastasis (P=0.016). The results indicated that SPARC tends to be highly expressed in human osteosarcoma tissues. The expression level of SPARC is associated with lung metastasis, which may be an indicator of prognosis. Thus, SPARC may be a potential tumor marker and therapeutic target in osteosarcoma.

In-depth proteomic analysis of tissue interstitial fluid for hepatocellular carcinoma serum biomarker discovery

Background:

Hepatocellular carcinoma (HCC) is a primary malignancy of the liver. New serum biomarkers for HCC screening are needed, especially for alpha-fetoprotein (AFP) negative patients. As a proximal fluid between body fluids and intracellular fluid, tissue interstitial fluid (TIF) is a suitable source for serum biomarker discovery.

Methods:

Sixteen paired TIF samples from HCC tumour and adjacent non-tumour tissues were analysed by isobaric tags for relative and absolute quantitation (iTRAQ) method. Two proteins were selected for ELISA validation in serum samples.

Results:

Totally, 3629 proteins were identified and 3357 proteins were quantified in TIF samples. Among them, 232 proteins were significantly upregulated in HCC-TIF and 257 proteins down-regulated. Two overexpressed extracellular matrix proteins, SPARC and thrombospondin-2 (THBS2) were selected for further validation. ELISA result showed that the serum levels of SPARC and THBS2 in HCC patients were both significantly higher than those in healthy controls. The combination of serum SPARC and THBS2 could distinguish HCC (AUC=0.97, sensitivity=86%, specificity=100%) or AFP-negative HCC (AUC=0.95, sensitivity=91%, specificity=93%) from healthy controls. And the combination of serum SPARC and THBS2 could also distinguish HCC patients from benign liver disease patients (AUC=0.93, sensitivity=80%, specificity=94%). In addition, serum THBS2 was found to be a novel independent indicator for poor prognosis of HCC.

Conclusions:

Novel HCC candidate serum markers were found through in-depth proteomic analysis of TIF, which demonstrated the successful utility of TIF in cancer serum biomarker discovery.

MiRNA-211 suppresses cell proliferation, migration and invasion by targeting SPARC in human hepatocellular carcinoma

Previous studies have shown that the expression of miR-211 was downregulated in hepatocellular carcinoma (HCC). However, the molecular function and mechanism of miR-211 in HCC growth and invasion are largely unclear. We found that miR-211 is downregulated in HCC tissues and cell lines, respectively. Further results showed that low miR-211 associated with TNM stage, vein invasion status, and poor prognosis. Ectopic expression of miR-211 effectively suppressed HCC cell proliferation, migration and invasion both in vitro and in vivo. We identified SPARC as a bona fide target of miR-211, and overexpression of miR-211 decreased the mRNA and protein expression of SPARC. Finally, we confirmed that the overexpression of SPARC in miR-211-expressing HCC cells can partially restore the inhibitory effect of miR-211. Taken together, our results demonstrated that loss of miR-211 expression and thus uncontrolled SPARC overexpression might drive progression of HCC, which may provide a novel therapeutic strategy for the treatment of HCC.

Hepatic stellate cells: central modulators of hepatic carcinogenesis

Hepatocellular carcinoma (HCC) represents the second most common cause of cancer-related death worldwide, and is increasing in incidence. Currently, our therapeutic repertoire for the treatment of HCC is severely limited, and therefore effective new therapies are urgently required. Recently, there has been increasing interest focusing on the cellular and molecular interactions between cancer cells and their microenvironment. HCC represents a unique opportunity to study the relationship between a diseased stroma and promotion of carcinogenesis, as 90 % of HCCs arise in a cirrhotic liver. Hepatic stellate cells (HSC) are the major source of extracellular proteins during fibrogenesis, and may directly, or via secreted products, contribute to tumour initiation and progression. In this review we explore the complex cellular and molecular interplay between HSC biology and hepatocarcinogenesis. We focus on the molecular mechanisms by which HSC modulate HCC growth, immune cell evasion and angiogenesis. This is followed by a discussion of recent progress in the field in understanding the mechanistic crosstalk between HSC and HCC, and the pathways that are potentially amenable to therapeutic intervention. Furthermore, we summarise the exciting recent developments in strategies to target HSC specifically, and novel techniques to deliver pharmaceutical agents directly to HSC, potentially allowing tailored, cell-specific therapy for HCC.

Re-sensitization of 5-FU resistance by SPARC through negative regulation of glucose metabolism in hepatocellular carcinoma

Secreted protein, acidic and rich in cysteine (SPARC), a calcium-binding matricellular glycoprotein, is implicated in the progression of many cancers. Currently, there is growing evidence for important functions of SPARC in a variety of cancers and its role in cancer depends on tumor types. In this study, we reported SPARC negatively regulated glucose metabolism in hepatocellular carcinoma (HCC). Overexpression of SPARC inhibited glucose uptake and lactate product through downregulation of key enzymes of glucose metabolism. On the other hand, knock down of SPARC reversed the phenotypes. Meanwhile, exogenous expression of SPARC in HepG2 cells resulted in tolerance to low glucose and was correlated with AMPK pathway. Interestingly, the 5-fluorouracil (5-FU)-resistant HepG2 cells showed increased glucose metabolism and downregulated SPARC levels. Finally, we reported the overexpression of SPARC re-sensitize 5-FU-resistant cells to 5-FU through inhibition of glycolysis both in vitro and in vivo. Our study proposed a novel function of SPARC in the regulation of glucose metabolism in hepatocellular carcinoma and will facilitate the development of therapeutic strategies for the treatments of liver tumor patients.

Multipotent mesenchymal stromal cells in liver cancer: implications for tumor biology and therapy

Remodeling of tumor microenvironment is a hallmark in the pathogenesis of liver cancer. Being a pivotal part of tumor stroma, multipotent mesenchymal stromal cells (MSCs), also known as mesenchymal stem cells (MSCs), are recruited and enriched in liver tumors. Owing to their tumor tropism, MSCs are now emerging as vehicles for anticancer drug/gene delivery against liver cancer. However, the exact impact of MSCs on liver cancer remains elusive, as a variety of effects of these cells that have been reported included a plethora of tumor-promoting effects and anti-oncogenic properties. This review aims to dissect the mechanistic insight regarding this observed discrepancy in different experimental settings of liver cancer. Furthermore, we call for caution using MSCs to treat liver cancer or even premalignant liver diseases, before conclusive evidence for safety and efficacy having been obtained.

Insidious changes in stromal matrix fuel cancer progression

Reciprocal interactions between tumor and stromal cells propel cancer progression and metastasis. A complete understanding of the complex contributions of the tumor stroma to cancer progression necessitates a careful examination of the extracellular matrix (ECM), which is largely synthesized and modulated by cancer-associated fibroblasts. This structurally supportive meshwork serves as a signaling scaffold for a myriad of biologic processes and responses favoring tumor progression. The ECM is a repository for growth factors and cytokines that promote tumor growth, proliferation, and metastasis through diverse interactions with soluble and insoluble ECM components. Growth factors activated by proteases are involved in the initiation of cell signaling pathways essential to invasion and survival. Various transmembrane proteins produced by the cancer stroma bind the collagen and fibronectin-rich matrix to induce proliferation, adhesion, and migration of cancer cells, as well as protease activation. Integrins are critical liaisons between tumor cells and the surrounding stroma, and with their mechano-sensing ability, induce cell signaling pathways associated with contractility and migration. Proteoglycans also bind and interact with various matrix proteins in the tumor microenvironment to promote cancer progression. Together, these components function to mediate cross-talk between tumor cells and fibroblasts ultimately to promote tumor survival and metastasis. These stromal factors, which may be expressed differentially according to cancer stage, have prognostic utility and potential. This review examines changes in the ECM of cancer-associated fibroblasts induced through carcinogenesis, and the impact of these changes on cancer progression. The implication is that cancer progression, even in epithelial cancers, may be based in large part on changes in signaling from cancer-associated stromal cells. These changes may provide early prognostic indicators to further stratify patients during treatment or alter the timing of their follow-up visits and observations.

The expression of SPARC in human intracranial aneurysms and its relationship with MMP-2/-9

Objective

SPARC is a key determinant of invasion and metastasis in some tumors, such as gliomas, melanomas and prostate tumors. SPARC can change the composition and structure of the matrix and promote angiogenesis; these effects are closely related to clinical stage and the prognosis of tumors such as meningiomas. However, little is known about the expression of SPARC in intracranial aneurysms. The goal of this study was to establish the role of SPARC in human intracranial aneurysms.

Methods

Thirty-one intracranial aneurysms were immunohistochemically stained for SPARC, MMP-2 and MMP-9. As controls, normal Circle of Willis arteries were similarly immunostained. All specimens were retrieved during autopsies and were embedded in paraffin. To evaluate the expression levels of SPARC, MMP-2 and MMP-9, western blotting was also performed in three available intracranial aneurysm specimens. The limited availability of fresh intracranial aneurysm tissue was the result of the majority of patients choosing endovascular embolization.

Results

The results showed that SPARC, MMP-2 and MMP-9 were strongly expressed in intracranial aneurysm tissues; however, these proteins were expressed minimally or not at all in normal Circle of Willis arteries. The western blot results showed that the expression levels of SPARC, MMP-2 and MMP-9 were significantly up-regulated in intracranial aneurysms relative to the expression levels in the normal Circle of Willis arteries. Data analysis showed that SPARC was significantly correlated with MMP-2 and MMP-9, also with age and risk factors but not with the Hunt-Hess grade or with sex.

Conclusion

The results indicate that SPARC is widely expressed in human intracranial aneurysms, and its expression correlates with MMP-2 and MMP-9 expression, age and risk factors but not with the Hunt-Hess grade. The results of this study suggest that SPARC has a pathogenic role in the alteration of the extracellular matrix of intracranial arteries during aneurysm formation.

Lack of the matricellular protein SPARC (secreted protein, acidic and rich in cysteine) attenuates liver fibrogenesis in mice

Introduction

Secreted Protein, Acidic and Rich in Cysteine (SPARC) is a matricellular protein involved in many biological processes and found over-expressed in cirrhotic livers. By mean of a genetic approach we herein provide evidence from different in vivo liver disease models suggesting a profibrogenic role for SPARC.

Methods

Two in vivo models of liver fibrosis, based on TAA administration and bile duct ligation, were developed on SPARC wild-type (SPARC^+/+) and knock-out (SPARC^−/−) mice. Hepatic SPARC expression was analyzed by qPCR. Fibrosis was assessed by Sirius Red staining, and the maturation state of collagen fibers was analyzed using polarized light. Necroinflammatory activity was evaluated by applying the Knodell score and liver inflammatory infiltration was characterized by immunohistochemistry. Hepatic stellate cell activation was assessed by α-SMA immunohistochemistry. In addition, pro-fibrogenic genes and inflammatory cytokines were measured by qPCR and/or ELISA. Liver gene expression profile was analyzed in SPARC^−/− and SPARC^+/+ mice using Affymetrix Mouse Gene ST 1.0 array.

Results

SPARC expression was found induced in fibrotic livers of mouse and human. SPARC^−/− mice showed a reduction in the degree of inflammation, mainly CD4+ cells, and fibrosis. Consistently, collagen deposits and mRNA expression levels were decreased in SPARC^−/− mice when compared to SPARC^+/+ mice; in addition, MMP-2 expression was increased in SPARC^−/− mice. A reduction in the number of activated myofibroblasts was observed. Moreover, TGF-β1 expression levels were down-regulated in the liver as well as in the serum of TAA-treated knock-out animals. Ingenuity Pathway Analysis (IPA) analysis suggested several gene networks which might involve protective mechanisms of SPARC deficiency against liver fibrogenesis and a better established machinery to repair DNA and detoxify from external chemical stimuli.

Conclusions

Overall our data suggest that SPARC plays a significant role in liver fibrogenesis. Interventions to inhibit SPARC expression are suggested as promising approaches for liver fibrosis treatment.

Targeting SPARC by lentivirus-mediated RNA interference inhibits cervical cancer cell growth and metastasis

Background

Secreted protein acidic and rich in cysteine (SPARC), a calcium-binding matricellular glycoprotein, is implicated in the progressions of some cancers. However, no information has been available to date regarding the function of SPARC in cervical cancer cell growth and metastasis.

Methods

In this study, we isolated and established high invasive subclones and low invasive subclones from human cervical cancer cell lines HeLa and SiHa by the limited dilution method. Real-time q-RT-PCR, Western Blot and ICC were performed to investigate SPARC mRNA and protein expressions in high invasive subclones and low invasive subclones. Then lentivirus vector with SPARC shRNA was constructed and infected the highly invasive subclones. Real-time q-RT-PCR, Western Blot and ICC were also performed to investigate the changes of SPARC expression after viral infection. In functional assays, effects of SPARC knockdown on the biological behaviors of cervical cancer cells were investigated. The mechanisms of SPARC in cervical cancer proliferation, apoptosis and invasion were also researched.

Results

SPARC was over-expressed in the highly invasive subclones compared with the low invasive subclones. Knockdown of SPARC significantly suppressed cervical cancer cell proliferation, and induced cell cycle arrest at the G1/G0 phase through the p53/p21 pathway, also caused cell apoptosis accompanied by the decreased ratio of Bcl-2/Bax, and inhibited cell invasion and metastasis accompanied by down-regulated MMP2 and MMP9 expressions and up-regulated E-cadherin expression.

Conclusion

SPARC is related to the invasive phenotype of cervical cancer cells. Knockdown of SPARC significantly suppresses cervical cancer cell proliferation, induces cell apoptosis and inhibits cell invasion and metastasis. SPARC as a promoter improves cervical cancer cell growth and metastasis.

SPARC is a key regulator of proliferation, apoptosis and invasion in human ovarian cancer

Background

Secreted protein acidic and rich in cysteine (SPARC), a calcium-binding matricellular glycoprotein, is implicated in the progression of many cancers. In this study, we investigated the expression and function of SPARC in ovarian cancer.

Methods

cDNA microarray analysis was performed to compare gene expression profiles of the highly invasive and the low invasive subclones derived from the SKOV3 human ovarian cancer cell line. Immunohistochemistry (IHC) staining was performed to investigate SPARC expression in a total of 140 ovarian tissue specimens. In functional assays, effects of SPARC knockdown on the biological behavior of ovarian cancer cells were investigated. The mechanisms of SPARC in ovarian cancer proliferation, apoptosis and invasion were also researched.

Results

SPARC was overexpressed in the highly invasive subclone compared with the low invasive subclone. High SPARC expression was associated with high stage, low differentiation, lymph node metastasis and poor prognosis of ovarian cancer. Knockdown of SPARC expression significantly suppressed ovarian cancer cell proliferation, induced cell apoptosis and inhibited cell invasion and metastasis.

Conclusion

SPARC is overexpressed in highly invasive subclone and ovarian cancer tissues and plays an important role in ovarian cancer growth, apoptosis and metastasis.

Aberrant methylation of SPARC in human hepatocellular carcinoma and its clinical implication

AIM: To investigate the methylation status of secreted protein acidic and rich in cysteine (SPARC) in human hepatocellular carcinoma (HCC) and evaluate its clinical implication.

METHODS: The methylation status of SPARC was analyzed in one HCC cell line (SMMC-7721) and 60 pairs of HCC and corresponding nontumorous tissues by methylation-specific polymerase chain reaction and bisulfite sequencing. The expression of SPARC mRNA and protein were examined by reverse transcription polymerase chain reaction and immunohistochemistry, respectively. The correlations between the methylation status and the gene expression, the clinicopathological parameters, as well as the prognosis after surgery were analyzed.

RESULTS: In the SMMC-7721 cell line, the loss of SPARC expression was correlated with the aberrant methylation and could be reactivated by the demethylating agent 5-aza-2’-deoxycytidine. Methylation frequency of SPARC in HCC was significantly higher than that in the corresponding nontumorous tissues (45/60 vs 7/60, P < 0.001), and it was correlated with the pathological classification (P = 0.019). The downregulation of the SPARC mRNA expression in HCC was correlated with the SPARC methylation (P = 0.040). The patients with methylated SPARC had a poorer overall survival than those without methylated SPARC (28.0 mo vs 41.0 mo, P = 0.043).

CONCLUSION: Aberrant methylation is an important mechanism for SPARC inactivation in HCC and SPARC methylation may be a promising biomarker for the diagnosis and prognosis of HCC.

The role of the myofibroblast in tumor stroma remodeling

Since its first description in wound granulation tissue, the myofibroblast has been recognized to be a key actor in the epithelial-mesenchymal cross-talk that plays a crucial role in many physiological and pathological situations, such as regulation of prostate development, ventilation-perfusion in lung alveoli or organ fibrosis. The presence of myofibroblasts in the stroma reaction to epithelial tumors is well established and many data are accumulating which suggest that the stroma compartment is an active participant in tumor onset and/or evolution. In this review we summarize the evidence in favor of this concept, the main mechanisms that regulate myofibroblast differentiation and function, as well as the biophysical and biochemical factors possibly involved in epithelial-stroma interactions, using liver carcinoma as main model, in view of achieving a better understanding of tumor progression mechanisms and of tools directed toward stroma as eventual therapeutic target.

Secreted protein acidic and rich in cysteine (SPARC) is associated with nasopharyngeal carcinoma metastasis and poor prognosis

Background

The aim of the present study was to analyse the expression of Secreted protein acidic and rich in cysteine (SPARC) in nasopharyngeal carcinoma (NPC) specimens, and to evaluate its correlation with clinicopathologic features, including survival of patients with NPC

Methods

NPC tissue microarrays (TMAs) were constructed from Sun Yat-sen University Cancer Center (SYSUCC), another three centers on mainland China, Singapore and Hong Kong. Using quantitative RT-PCR and Western-blotting techniques, we detected mRNA and protein expression of SPARC in NPC cell lines and immortalized nasopharyngeal epithelial cells (NPECs) induced by Bmi-1 (NPEC2 Bmi-1). The difference of SPARC expression in the cell lines was tested using a t-test method. The relationship between the SPARC expression and clinicopathological data was assessed by chi-square. Survival analysis was estimated using the Kaplan-Meier approach with log-rank test. Univariate and multivariate analyses of clinical variables were performed using Cox proportional hazards regression models.

Results

The expression levels of SPARC mRNA and protein were markedly higher in NPC cell lines than in NPEC2 Bmi-1. Especially, the expression levels of SPARC mRNA and protein were much lower in the 6-10B than in the 5-8 F (P = 0.002, P = 0.001). SPARC immunostaining revealed cytoplasmic localization in NPC cells and no staining in the stroma and epithelium.

In addition, high level of SPARC positively correlated with the status of distant metastasis (P = 0.001) and WHO histological classification (P = 0.023). NPC patients with high SPARC expression also had a significantly poorer prognosis than patients with low SPARC expression (log-rank test, P < 0.001), especially patients with advanced stage disease (log-rank, P < 0.001). Multivariate analysis suggested that the level of SPARC expression was an independent prognostic indicator for the overall survival of patients with NPC (P < 0.001).

Conclusions

SPARC expression is common in NPC patients. Our data shows that elevated SPARC expression is a potential unfavorable prognostic factor for patients with NPC.

Differential Expression of SPARC in Intestinal-type Gastric Cancer Correlates with Tumor Progression and Nodal Spread

AIMS

Nodal spread is the single most important prognostic factor of survival in gastric cancer patients. In this study, genes that were upregulated in the lymph node metastases of gastric cancer were identified and may serve as putative novel therapeutic target.

METHODS

Complementary DNA (cDNA) microarray analysis and quantitative real-time polymerase chain reaction of primary gastric carcinomas and matched lymph node metastasis were carried out. Immunohistochemistry with anti-SPARC antibodies was performed on large tissue sections of 40 cases with primary gastric carcinoma (20 diffuse, 20 intestinal) and the corresponding lymph node metastases, as well as on tissue microarrays of 152 gastric cancer cases.

RESULTS

A cDNA microarray identified SPARC as being upregulated in primary gastric carcinoma tissue and the corresponding lymph node metastasis compared with the nonneoplastic mucosa. SPARC was expressed in fibroblasts and, occasionally, in tumor cells. However, the level of immunoreactivity was particularly strong in stromal cells surrounding the tumor. The level of expression of SPARC, determined by immunohistochemistry, correlated in intestinal-type gastric cancer with the local tumor growth, nodal spread, and tumor stage according to the International Union Against Cancer.

CONCLUSIONS

Our study provides transcriptional and translational evidence for the differential expression of SPARC in gastric cancer tissue. On the basis of our observations and those made by others, we hypothesize that SPARC is a promising novel target for the treatment of gastric cancer.

Differential Expression of SPARC in Intestinal-type Gastric Cancer Correlates with Tumor Progression and Nodal Spread

AIMS

Nodal spread is the single most important prognostic factor of survival in gastric cancer patients. In this study, genes that were upregulated in the lymph node metastases of gastric cancer were identified and may serve as putative novel therapeutic target.

METHODS

Complementary DNA (cDNA) microarray analysis and quantitative real-time polymerase chain reaction of primary gastric carcinomas and matched lymph node metastasis were carried out. Immunohistochemistry with anti-SPARC antibodies was performed on large tissue sections of 40 cases with primary gastric carcinoma (20 diffuse, 20 intestinal) and the corresponding lymph node metastases, as well as on tissue microarrays of 152 gastric cancer cases.

RESULTS

A cDNA microarray identified SPARC as being upregulated in primary gastric carcinoma tissue and the corresponding lymph node metastasis compared with the nonneoplastic mucosa. SPARC was expressed in fibroblasts and, occasionally, in tumor cells. However, the level of immunoreactivity was particularly strong in stromal cells surrounding the tumor. The level of expression of SPARC, determined by immunohistochemistry, correlated in intestinal-type gastric cancer with the local tumor growth, nodal spread, and tumor stage according to the International Union Against Cancer.

CONCLUSIONS

Our study provides transcriptional and translational evidence for the differential expression of SPARC in gastric cancer tissue. On the basis of our observations and those made by others, we hypothesize that SPARC is a promising novel target for the treatment of gastric cancer.

Global gene profiling of spontaneous hepatocellular carcinoma in B6C3F1 mice: similarities in the molecular landscape with human liver cancer

Hepatocellular carcinoma (HCC) is an important cause of morbidity and mortality worldwide. Although the risk factors of human HCC are well known, the molecular pathogenesis of this disease is complex, and in general, treatment options remain poor. The use of rodent models to study human cancer has been extensively pursued, both through genetically engineered rodents and rodent models used in carcinogenicity and toxicology studies. In particular, the B6C3F1 mouse used in the National Toxicology Program (NTP) two-year bioassay has been used to evaluate the carcinogenic effects of environmental and occupational chemicals, and other compounds. The high incidence of spontaneous HCC in the B6C3F1 mouse has challenged its use as a model for chemically induced HCC in terms of relevance to the human disease. Using global gene expression profiling, we identify the dysregulation of several mediators similarly altered in human HCC, including re-expression of fetal oncogenes, upregulation of protooncogenes, downregulation of tumor suppressor genes, and abnormal expression of cell cycle mediators, growth factors, apoptosis regulators, and angiogenesis and extracellular matrix remodeling factors. Although major differences in etiology and pathogenesis remain between human and mouse HCC, there are important similarities in global gene expression and molecular pathways dysregulated in mouse and human HCC. These data provide further support for the use of this model in hazard identification of compounds with potential human carcinogenicity risk, and may help in better understanding the mechanisms of tumorigenesis resulting from chemical exposure in the NTP two-year carcinogenicity bioassay.

A combined strategy of SAGE and quantitative PCR Provides a 13-gene signature that predicts preoperative chemoradiotherapy response and outcome in rectal cancer

PURPOSE

Preoperative chemoradiotherapy (CRT) is the treatment of choice for rectal cancer (RC), but half of the patients do not respond, suffer unnecessary toxicities, and surgery delays. We aimed to develop a model that could predict a clinically meaningful response to CRT by using formalin-fixed paraffin-embedded (FFPE) biopsies.

EXPERIMENTAL DESIGN

We first carried out an exploratory screening of candidate genes by using SAGE technology to evaluate dynamic changes in the RC transcriptome in selected refractory patients before and after CRT. Next, 53 genes (24 from SAGE and 29 from the literature) were analyzed by qPCR arrays in FFPE initial biopsies from 94 stage II/III RC patients who were preoperatively treated with CRT. Tumor response was defined by using Dworak's tumor regression grade (2-3-4 vs. 0-1). Multivariate Cox methods and stepwise algorithms were applied to generate an optimized predictor of response and outcome.

RESULTS

In the training cohort (57 patients), a 13-gene signature predicted tumor response with 86% accuracy, 87% sensitivity, and 82% specificity. In a testing cohort (37 patients), the model correctly classified 6 of 7 nonresponders, with an overall accuracy of 76%. A signature-based score identified patients with a higher risk of relapse in univariate (3-year disease-free survival 64% vs. 90%, P = 0.001) and multivariate analysis (HR = 4.35 95% CI: 1.2-15.75, P = 0.02), in which it remained the only statistically significant prognostic factor.

CONCLUSIONS

A basal 13-gene signature efficiently predicted CRT response and outcome. Multicentric validation by the GEMCAD collaborative group is currently ongoing. If confirmed, the predictor could be used to improve patient selection in RC studies.

Identification of SPARC as a candidate target antigen for immunotherapy of various cancers

To establish efficient anticancer immunotherary, it is important to identify tumor-associated antigens (TAAs) directing the immune system to attack cancer. A genome-wide cDNA microarray analysis identified that secreted protein acidic and rich in cysteine (SPARC) gene is overexpressed in the gastric, pancreatic and colorectal cancer tissues but not in their noncancerous counterparts. This study attempted to identify HLA-A24 (A*2402)-restricted and SPARC-derived CTL epitopes. We previously identified H-2K(d)-restricted and SPARC-derived CTL epitope peptides in BALB/c mice, of which H-2K(d)-binding peptide motif is comparable with that of HLA-A24 binding peptides. By using these peptides, we tried to induce HLA-A24 (A*2402)-restricted and SPARC-reactive human CTLs and demonstrated an antitumor immune response. The SPARC-A24-1(143-151) (DYIGPCKYI) and SPARC-A24-4(225-234) (MYIFPVHWQF) peptides-reactive CTLs were successfully induced from peripheral blood mononuclear cells by in vitro stimulation with these two peptides in HLA-A24 (A*2402) positive healthy donors and cancer patients, and these CTLs exhibited cytotoxicity specific to cancer cells expressing both SPARC and HLA-A24 (A*2402). Furthermore, the adoptive transfer of the SPARC-specific CTLs could inhibit the tumor growth in nonobese diabetic/severe combined immunodeficient mice bearing human cancer cells expressing both HLA-A24 (A*2402) and SPARC. These findings suggest that SPARC is a potentially useful target candidate for cancer immunotherapy.

KLF4 inhibition of lung cancer cell invasion by suppression of SPARC expression

Krüppel-Like Factor 4 (KLF4) functions as a tumor suppressor in some cancers, but its molecular mechanism is not clear. Our recent study also showed that the expression of KLF4 is dramatically reduced in primary lung cancer tissues. To investigate the possible role of KLF4 in lung cancer, we stably transfected KLF4 into cells from lung cancer cell lines H322 and A549 to determine the cells' invasion ability. Our results showed that ectopic expression of KLF4 extensively suppressed lung cancer cell invasion in Matrigel. This effect was independent of KLF4-mediated p21 up-regulation because ectopic expression of p21 had minimal effect on cell invasion. Our analysis of the expression of 12 genes associated with cell invasion in parental, vector-transfected, and KLF4-transfected cells showed that ectopic expression of KLF4 resulted in extensively repressed expression of secreted protein acidic and rich in cysteine (SPARC), an extracellular matrix protein that plays a role in tumor development and metastasis. Knockdown of SPARC expression in H322 and A549 cells led to suppression of cell invasion, comparable to that observed in KLF4-transfected cells. Moreover, retrovirus-mediated restoration of SPARC expression in KLF4-transfected cells abrogated KLF4-induced anti-invasion activity. Together, our results indicate that KLF4 inhibits lung cancer cell invasion by suppressing SPARC gene expression.

Liver myofibroblasts activate protein C and respond to activated protein C

AIM: To study the protein C activation system in human liver myofibroblasts, and the effects of activated protein C (APC) on these cells.

METHODS: Human liver myofibroblasts were obtained by outgrowth. Expression of protease activated receptor 1 (PAR-1), endothelial protein C receptor (EPCR) and thrombomodulin (TM) was analyzed by flow cytometry. Extracellular signal-regulated kinase (ERK)1/2 activation was assessed by Western blotting using anti-phospho-ERK antibodies. Collagen synthesis was studied with real-time reverse transcription-polymerase chain reaction (RT-PCR). Activation of protein C was studied by incubating liver myofibroblasts with zymogen protein C in the presence of thrombin and detecting the generation of APC with a colorimetric assay using a peptide substrate.

RESULTS: Primary cultures of human liver myofibroblasts expressed EPCR on their surface, together with PAR-1 and TM. This receptor system was functional since exposure of myofibroblasts to APC induced ERK1/2 phosphorylation in a dose- and time-dependent manner. Furthermore, APC significantly upregulated the expression of collagen mRNA, as shown by real-time RT-PCR. Collagen upregulation was controlled through the ERK pathway as it was inhibited when using the mitogen-activated protein/extracellular signal-regulated kinase kinase inhibitor PD98059. Finally, using a cell-based colorimetric assay, we showed that intact myofibroblasts converted protein C into APC in the presence of thrombin.

CONCLUSION: These data suggest that APC is a new modulator of liver myofibroblast activity and contributes to the pathophysiology of chronic liver diseases.

SPARC: a matricellular regulator of tumorigenesis

Although many clinical studies have found a correlation of SPARC expression with malignant progression and patient survival, the mechanisms for SPARC function in tumorigenesis and metastasis remain elusive. The activity of SPARC is context- and cell-type-dependent, which is highlighted by the fact that SPARC has shown seemingly contradictory effects on tumor progression in both clinical correlative studies and in animal models. The capacity of SPARC to dictate tumorigenic phenotype has been attributed to its effects on the bioavailability and signaling of integrins and growth factors/chemokines. These molecular pathways contribute to many physiological events affecting malignant progression, including extracellular matrix remodeling, angiogenesis, immune modulation and metastasis. Given that SPARC is credited with such varied activities, this review presents a comprehensive account of the divergent effects of SPARC in human cancers and mouse models, as well as a description of the potential mechanisms by which SPARC mediates these effects. We aim to provide insight into how a matricellular protein such as SPARC might generate paradoxical, yet relevant, tumor outcomes in order to unify an apparently incongruent collection of scientific literature.

Immunohistochemical expression of SPARC is correlated with recurrence, survival and malignant potential in meningiomas

Meningioma is a common neoplasm that constitutes almost 30% of all primary central nervous system tumors and is associated with inconsistent clinical outcomes. The extracellular matrix proteins play a crucial role in meningioma cell biology and are important in tumor cell invasion and in progression to malignancy. SPARC (secreted protein, acidic and rich in cysteine) (osteonectin) is a matricellular glycoprotein that regulates cell function by interacting with different extracellular matrix proteins. The aim of this study was to evaluate the expression of SPARC with proliferation index, p53 reactivity in WHO grade 1 (benign), grade 2 (atypical) and grade 3 (anaplastic) meningiomas and correlate with clinical features of the patients, including location of the tumor, recurrence of the tumor and survival of patients. We studied 111 meningiomas, 69 being benign, 34 being atypical and eight being anaplastic meningiomas of various histological types. Using immunohistochemical analysis, we evaluated the expression of SPARC, Ki-67 (MIB-1) and p53 in meningiomas. Immunohistochemical scores of SPARC were determined as the sum of frequency (0-3) and intensity (0-3) of immunolabeling of the tumor cells. A high immunohistochemical score (4-6) for SPARC was more frequent in atypical and in anaplastic meningiomas than in benign meningiomas (p < 0.01). MIB-1 proliferation index showed significant association between tumor grades in meningiomas (p < 0.01). At the end of a follow-up period of 47.53 +/- 25.04 months, 30 tumors recurred. A high SPARC expression was significantly associated with tumor recurrence (p = 0.02). The immunoreactivity of p53 protein and MIB-1 score were significantly higher in recurrent meningiomas than in non-recurrent meningiomas. The cumulative survival of patients with high SPARC expression was significantly lower than patients with low SPARC expression. The high SPARC expression scores were predominantly identified in meningothelial, fibrous and chordoid meningiomas; low SPARC expression scores were mostly spotted in secretory and psammomatous meningiomas. Evaluating SPARC expression might help assessing recurrence risk and survival estimation in meningiomas.

Activated hepatic stellate cells promote tumorigenicity of hepatocellular carcinoma

Liver cirrhosis is the main risk factor for the development of hepatocellular carcinoma (HCC). Activated hepatic stellate cells (HSC) are the effector cells of hepatic fibrosis and also infiltrate the HCC stroma where they might play a critical role in HCC progression. Here we aimed to analyze the effects of activated HSC on the proliferation and growth of HCC cell lines in vitro and in vivo. Conditioned media (CM) collected from HSC significantly induced proliferation and migration of HCC cells cultured in monolayers. In a 3-dimensional spheroid coculture system, HSC promoted HCC growth and diminished the extent of central necrosis. In accordance, in vivo simultaneous implantation of HSC and HCC cells into nude mice promoted tumor growth and invasiveness, and inhibited necrosis formation. As potential mechanism of the tumorigenic effects of HSC we identified activation of NFkappaB and extracellular-regulated kinase (ERK) in HCC cells, two signaling cascades that play a crucial role in HCC progression. In summary, our data indicate that stromal HSC promotes HCC progression and suggest the HSC-HCC interaction as an interesting tumor differentiation-independent target for therapy of this highly aggressive cancer.

Characteristic gene expression in stromal cells of gastric cancers among atomic-bomb survivors

To elucidate the mechanism of radiation-induced cancers, molecular analysis of cancers in atomic-bomb survivors is important. In our study, we developed a custom oligonucleotide array of 208 genes. We analyzed gene expression profiles of gastric cancers (GCs) from atomic-bomb survivors and identified 9 genes with significantly lower expression in GCs from exposed patients than in GCs from nonexposed patients. Among these 9 genes, expression of versican and osteonectin was investigated in greater detail using immunohistochemistry in 116 GCs from 64 exposed and 52 nonexposed patients who developed GC after the bombing. In the Stage I/II GCs, the clinicopathologic, phenotypic and proliferative characteristics of GCs from exposed and nonexposed patients did not differ significantly; however, versican and osteonectin were expressed at much lower levels in the area of tumor-associated stroma of exposed patients than in nonexposed patients (p = 0.026 and p = 0.024, respectively). These results suggest that the characteristics of tumor-associated stromal cells differ between GCs from exposed and nonexposed patients.

Adenovirus-mediated inhibition of SPARC attenuates liver fibrosis in rats

BACKGROUND

The interaction between fibrogenic cells and extracellular matrix plays a role in liver fibrosis, yet the mechanisms are largely unknown. Secreted protein, acidic and rich in cysteine (SPARC) is a matricellular glycoprotein that is expressed by hepatic stellate cells and is overexpressed in fibrotic livers. We investigated the in vivo role of SPARC in experimentally induced liver fibrosis in rats.

METHODS

A recombinant adenovirus carrying antisense SPARC was constructed (AdasSPARC). Advanced liver fibrosis was induced in Sprague-Dawley rats by prolonged intraperitoneal administration of thioacetamide. Animals received injections of AdasSPARC or Ad beta gal (control adenovirus) via the tail vein and directly into the liver 1 week after the first dose. The pathological changes in liver tissues and indices of fibrosis were assessed at eight weeks. Expression of SPARC, transforming growth factor (TGF)-beta and alpha-smooth muscle actin were evaluated by quantitative real-time polymerase chain reaction, western blotting, enzyme-linked immunosorbent assay and immunohistochemistry.

RESULTS

Hepatic SPARC expression significantly increased during the development of liver fibrosis. AdasSPARC markedly attenuated the development of hepatic fibrosis in rats treated with thiocetamide, as assessed by decreased collagen deposition, lower hepatic content of hydroxyproline and less advanced morphometric stage of fibrosis. AdasSPARC treatment reduced inflammatory activity (Knodell score) and suppressed transdifferentiation of hepatic stellate cell to the myofibroblasts like phenotype in vivo. Furthermore, in vitro inhibition of SPARC on hepatic stellate cells decreases the production of TGF-beta.

CONCLUSIONS

This is the first study to demonstrate that knockdown of hepatic SPARC expression ameliorates thioacetamide-induced liver fibrosis in rats with chronic liver injury. SPARC is a potential target for gene therapy in liver fibrosis.

The role of the matricellular protein SPARC in the dynamic interaction between the tumor and the host

Tumor growth is essentially the result of an evolving cross-talk between malignant and surrounding stromal cells (fibroblasts, endothelial cells and inflammatory cells). This heterogeneous mass of extracellular matrix and intermingled cells interact through cell-cell and cell-matrix contacts. Malignant cells also secrete soluble proteins that reach neighbor stromal cells, forcing them to provide the soil on which they will grow and metastasize. Different studies including expression array analysis identified the matricellular protein SPARC as a marker of poor prognosis in different cancer types. Further evidence demonstrated that high SPARC levels are often associated with the most aggressive and highly metastatic tumors. Here we describe the most recent evidence that links SPARC with human cancer progression, the controversy regarding its role in certain human cancers and the physiological processes in which SPARC is involved: epithelial-mesenchymal transition, immune surveillance and angiogenesis. Its relevance as a potential target in cancer therapy is also discussed.

The role of the matricellular protein SPARC in the dynamic interaction between the tumor and the host

Tumor growth is essentially the result of an evolving cross-talk between malignant and surrounding stromal cells (fibroblasts, endothelial cells and inflammatory cells). This heterogeneous mass of extracellular matrix and intermingled cells interact through cell-cell and cell-matrix contacts. Malignant cells also secrete soluble proteins that reach neighbor stromal cells, forcing them to provide the soil on which they will grow and metastasize. Different studies including expression array analysis identified the matricellular protein SPARC as a marker of poor prognosis in different cancer types. Further evidence demonstrated that high SPARC levels are often associated with the most aggressive and highly metastatic tumors. Here we describe the most recent evidence that links SPARC with human cancer progression, the controversy regarding its role in certain human cancers and the physiological processes in which SPARC is involved: epithelial-mesenchymal transition, immune surveillance and angiogenesis. Its relevance as a potential target in cancer therapy is also discussed.

A prototypic matricellular protein in the tumor microenvironment--where there's SPARC, there's fire

Within the tumor microenvironment is a dynamic exchange between cancer cells and their surrounding stroma. This complex biologic system requires carefully designed models to understand the role of its stromal components in carcinogenesis, tumor progression, invasion, and metastasis. Secreted protein acidic and rich in cysteine (SPARC) is a prototypic matricellular protein at the center of this exchange. Two decades of basic science research combined with recent whole genome analyses indicate that SPARC is an important player in vertebrate evolution, normal development, and maintenance of normal tissue homeostasis. Therefore, SPARC might also play an important role in the tumor microenvironment. Clinical evidence indicates that SPARC expression correlates with tumor progression, but tightly controlled animal models have shown that the role of SPARC in tumor progression is dependent on tissue and tumor cell type. In this Prospectus, we review the current understanding of SPARC in the tumor microenvironment and discuss current and future investigations of SPARC and tumor-stromal interactions that require careful consideration of growth factors, cytokines, proteinases, and angiotropic factors that might influence SPARC activity and tumor progression.

The nonsteroidal anti-inflammatory drug NS398 reactivates SPARC expression via promoter demethylation to attenuate invasiveness of lung cancer cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to exhibit potent anticancer effects in vitro and in vivo. One of the mechanisms by which NSAIDs suppress tumorigenesis is inhibition of angiogenesis and metastasis. In this study, we used a microarray system to study the change of expression profile of metastasis-related genes regulated by NS398, a NSAID and a cyclooxygenase-2 (COX-2) inhibitor. We found that several negative regulators of cell invasion, including secreted protein acidic and rich in cysteine (SPARC), thrombospondin 1 (TSP-1), thrombospondin 3 (TSP-3), and tissue inhibitors of matrix metalloproteinase-2 (TIMP-2) are upregulated by NS398. In addition, we demonstrated that upregulation of SPARC expression by NS398 in human lung cancer cells is mediated by promoter demethylation and associated with a decrease in DNA methyltransferase (DNMT) expression. This is the first report to show that NS398 can inhibit the expression of DNMT1 and 3b. Functional assay indicated that SPARC is a critical mediator for NS398 to inhibit cell invasion. Our results provide new insights for the understanding of the anticancer actions of NSAIDs.

Analyses of the role of endogenous SPARC in mouse models of prostate and breast cancer

Secreted protein, acidic and rich in cysteine (SPARC, also known as osteonectin or BM-40) is a glycoprotein component of the extracellular matrix that has been reported to be involved with a variety of cellular processes. Although SPARC expression levels are frequently altered in a variety of tumor types, the exact implications of deregulated SPARC expression--whether it promotes, inhibits or has no effect on tumor progression--have remained unclear. Our recent gene expression analyses have shown that SPARC is significantly downregulated in highly metastatic human prostate cancer cells. To test the role of endogenous SPARC in tumorigenesis directly, we examined cancer progression and metastasis in SPARC(+/-) and SPARC(-/-) mice using two separate transgenic mouse tumor models: transgenic adenocarcinoma of the mouse prostate (TRAMP) and murine mammary tumor virus-polyoma middle T (MMTV-PyMT). Surprisingly, in both instances, we found that loss of SPARC had no significant effects on tumor initiation, progression or metastasis. Tumor angiogenesis and collagen deposition were also largely unaffected. Our results indicate that, although differential SPARC expression may be a useful marker of aggressive, metastasis-prone tumors, loss of SPARC is not sufficient either to promote or to inhibit cancer progression in two spontaneous mouse tumor models.

Characterization of Smoc-1 uncovers two transcript variants showing differential tissue and age specific expression in Bubalus bubalis

Background

Secreted modular calcium binding protein-1 (Smoc-1) belongs to the BM-40 family which has been implicated with tissue remodeling, angiogenesis and bone mineralization. Besides its anticipated role in embryogenesis, Smoc-1 has been characterized only in a few mammalian species. We made use of the consensus sequence (5' CACCTCTCCACCTGCC 3') of 33.15 repeat loci to explore the buffalo transcriptome and uncovered the Smoc-1 transcript tagged with this repeat. The main objective of this study was to gain an insight into its structural and functional organization, and expressional status of Smoc-1 in water buffalo, Bubalus bubalis.

Results

We cloned and characterized the buffalo Smoc-1, including its copy number status, in-vitro protein expression, tissue & age specific transcription/translation, chromosomal mapping and localization to the basement membrane zone. Buffalo Smoc-1 was found to encode a secreted matricellular glycoprotein containing two EF-hand calcium binding motifs homologous to that of BM-40/SPARC family. In buffalo, this single copy gene consisted of 12 exons and was mapped onto the acrocentric chromosome 11. Though this gene was found to be evolutionarily conserved, the buffalo Smoc-1 showed conspicuous nucleotide/amino acid changes altering its secondary structure compared to that in other mammals. In silico analysis of the Smoc-1 proposed its glycoprotein nature with a calcium dependent conformation. Further, we unveiled two transcript variants of this gene, varying in their 3'UTR lengths but both coding for identical protein(s). Smoc-1 evinced highest expression of both the variants in liver and modest to negligible in other tissues. The relative expression of variant-02 was markedly higher compared to that of variant-01 in all the tissues examined. Moreover, expression of Smoc-1, though modest during the early ages, was conspicuously enhanced after 1 year and remained consistently higher during the entire life span of buffalo with gradual increment in expression of variant-02. Immunohistochemically, Smoc-1 was localized in the basement membrane zones and extracellular matrices of various tissues.

Conclusion

These data added to our understandings about the tissue, age and species specific functions of the Smoc-1. It also enabled us to demonstrate varying expression of the two transcript variants of Smoc-1 amongst different somatic tissues/gonads and ages, in spite of their identical coding frames. Pursuance of these variants for their roles in various disease phenotypes such as hepatocellular carcinoma and angiogenesis is envisaged to establish broader biological significance of this gene.

Frequent inactivation of SPARC by promoter hypermethylation in colon cancers

Epigenetic modification of gene expression plays an important role in the development of human cancers. The inactivation of SPARC through CpG island methylation was studied in colon cancers using oligonucleotide microarray analysis and methylation specific PCR (MSP). Gene expression of 7 colon cancer cell lines was evaluated before and after treatment with the demethylating agent 5-aza-2'-deoxycytidine (5Aza-dC) by oligonucleotide microarray analysis. Expression of SPARC was further examined in colon cancer cell lines and primary colorectal cancers, and the methylation status of the SPARC promoter was determined by MSP. SPARC expression was undetectable in 5 of 7 (71%) colorectal cancer cell lines. Induction of SPARC was demonstrated after treatment with the demethylating agent 5Aza-dC in 5 of the 7 cell lines. We examined the methylation status of the CpG island of SPARC in 7 colon cancer cell lines and in 20 test set of colon cancer tissues. MSP demonstrated hypermethylation of the CpG island of SPARC in 6 of 7 cell lines and in all 20 primary colon cancers, when compared with only 3 of 20 normal colon mucosa. Immunohistochemical analysis showed that SPARC expression was downregulated or absent in 17 of 20 colon cancers. A survival analysis of 292 validation set of colorectal carcinoma patients revealed a poorer prognosis for patients lacking SPARC expression than for patients with normal SPARC expression (56.79% vs. 75.83% 5-year survival rate, p = 0.0014). The results indicate that epigenetic gene silencing of SPARC is frequent in colon cancers, and that inactivation of SPARC is related to rapid progression of colon cancers.

Tumor-suppressor function of SPARC-like protein 1/Hevin in pancreatic cancer

SPARC-like protein 1 (SPARCL1), a member of the SPARC family, is downregulated in various tumors. In the present study, the expression and localization of SPARCL1 were analyzed in a wide range of nontumorous and neoplastic pancreatic tissues by quantitative reverse transcription-polymerase chain reaction, laser capture microdissection, microarray analysis, and immunohistochemistry. For functional analysis, proliferation and invasion assays were used in cultured pancreatic cancer cells. Pancreatic ductal adenocarcinoma (PDAC) and other pancreatic neoplasms exhibited increased SPARCL1 mRNA levels compared to those of the normal pancreas. SPARCL1 mRNA levels were low to absent in microdissected and cultured pancreatic cancer cells, and promoter demethylation increased SPARCL1 levels only slightly in three of eight cell lines. SPARCL1 was observed in small capillaries in areas of inflammation/tumor growth and in some islet cells. In PDAC, 15.4% of vessels were SPARCL1-positive. In contrast, the percentage of SPARCL1-positive vessels was higher in chronic pancreatitis and benign and borderline pancreatic tumors. Recombinant SPARCL1 inhibited pancreatic cancer cell invasion and exerted moderate growth-inhibitory effects. In conclusion, SPARCL1 expression in pancreatic tissues is highly correlated with level of vascularity. Its anti-invasive effects and reduced expression in metastasis indicate tumor-suppressor function.

In situ identification of genes regulated specifically in fibroblasts of human basal cell carcinoma

Basal cell carcinoma (BCC) is characterized by slow growth, virtual absence of metastases, and strong stroma-dependency. Cancer-associated fibroblasts (CAFs) in the tumor stroma influence tumor growth, invasion, and metastasis. To comprehensively characterize CAFs of BCC in their in situ cancer environment, laser capture microdissection, linear gene amplification, microarray analysis, and quantitative real-time PCR (qRT-PCR) were combined. Pair-wise comparison of gene expression of microdissected CAFs and corresponding normal perifollicular fibroblasts identified 65 genes that were significantly upregulated in at least two of three different patients. Among the annotated genes, as many as 13 genes encoded secreted proteins, of which six were previously implicated as CAF-associated proteins in various tumor types. Four of the seven novel CAF genes--matrix Gla-protein, secreted frizzled-related protein 2, angiopoietin-related protein-2, and platelet-derived growth factor receptor-like protein--were selected for further analyses by qRT-PCR and were found to be frequently upregulated in CAFs of three independent BCC tissues. Analyses of CAFs from squamous cell cancer, prostate cancer, and colon cancer did not indicate that these genes were upregulated in these cancers. This study thus validates a novel approach for comprehensive characterization CAFs in their in situ environment of BCC. The results suggest a specific expression profile of CAFs in BCC possibly accounting for disease-specific pathological roles.

SPARC and Hevin expression correlate with tumour angiogenesis in hepatocellular carcinoma

Both Secreted Protein Acidic and Rich in Cysteine (SPARC) and Hevin are multifunctional matricellular glycoproteins. Recent experimental studies suggested that Hevin and SPARC together diminish angiogenesis, but their significance in hepatocellular carcinoma (HCC) remains unclear. This study aimed to correlate SPARC and Hevin expression with angiogenesis and clinicopathological features in HCC. SPARC and Hevin protein and mRNA expression in HCC specimens were assessed by immunostaining, immunoblotting, and quantitative reverse transcriptase-polymerase chain reaction. Tumour microvessel density (MVD) was assessed by CD34 immunostaining. The role of SPARC and Hevin in HCC was further assessed in an in vivo nude mice xenograft model. Both SPARC and Hevin mRNA levels were significantly higher in tumours than in non-tumourous livers. A significant correlation between tumour SPARC and Hevin mRNA levels was found. Moreover, SPARC protein localized in the tumour sinusoidal area correlated significantly with Hevin protein localized in HCC cells. Truncated forms of SPARC and Hevin proteins were detected in clinical samples. Truncated SPARC protein localized in the tumour sinusoidal area correlated significantly with tumour MVD. On the other hand, overexpression of full-length SPARC in tumour xenografts in athymic nude mice significantly delayed tumour growth, and this delay was related to a decrease in tumour angiogenesis. Expression of Hevin protein within HCC cells was related to the presence of tumour encapsulation and the absence of hepatitis B surface antigen in clinical samples. Overexpression of Hevin in tumour xenografts also significantly delayed tumour growth. In conclusion, this study has shown that SPARC and Hevin are upregulated in HCC compared with non-tumourous liver, and that they are inter-related at both mRNA and protein levels. Moreover, both SPARC and Hevin were related to HCC angiogenesis and tumour progression.

Tissue microarray analysis reveals a tight correlation between protein expression pattern and progression of esophageal squamous cell carcinoma

BACKGROUND

The development of esophageal squamous cell carcinoma (ESCC) progresses a multistage process, collectively known as precursor lesions, also called dysplasia (DYS) and carcinoma in situ (CIS), subsequent invasive lesions and final metastasis. In this study, we are interested in investigating the expression of a variety of functional classes of proteins in ESCC and its precursor lesions and characterizing the correlation of these proteins with ESCC malignant progression.

METHODS

Fas, FADD, caspase 8, CDC25B, fascin, CK14, CK4, annexin I, laminin-5gamma2 and SPARC were analyzed using immunohistochemistry on tissue microarray containing 205 ESCC and 173 adjacent precursor lesions as well as corresponding normal mucosa. To confirm the immunohistochemical results, three proteins, fascin, CK14 and laminin-5gamma2, which were overexpressed in ESCC on tissue microarray, were detected in 12 ESCC cell lines by Western blot assay.

RESULTS

In ESCC and its precursor lesions, FADD, CDC25B, fascin, CK14, laminin-5gamma2 and SPARC were overexpressed, while Fas, caspase 8, CK4 and annexin I were underexpressed. The abnormalities of these proteins could be classified into different groups in relation to the stages of ESCC development. They were "early" corresponding to mild and moderate DYS with overexpression of fascin, FADD and CDC25B and underexpression of Fas, caspase 8, CK4 and annexin I, "intermediate" to severe DYS and CIS with overexpression of FADD and CK14, and "late" to invasive lesions (ESCC) and to advanced pTNM stage ESCC lesions with overexpression of CK14, laminin-5gamma2 and SPARC.

CONCLUSION

Analyzing the protein expression patterns of Fas, FADD, caspase 8, CDC25B, fascin, CK14, CK4, annexin I, laminin-5gamma2 and SPARC would be valuable to develop rational strategies for early detection of lesions at risk in advance as well as for prevention and treatment of ESCC.

ST7-mediated suppression of tumorigenicity of prostate cancer cells is characterized by remodeling of the extracellular matrix

Multiple lines of evidence have provided compelling evidence for the existence of a tumor suppressor gene (TSG) on chromosome 7q31.1. ST7 may be the target of this genetic instability but its designation as a TSG is controversial. In this study, we show that, functionally, ST7 behaves as a tumor suppressor in human cancer. ST7 suppressed growth of PC-3 prostate cancer cells inoculated subcutaneously into severe combined immunodeficient mice, and increased the latency of tumor detection from 13 days in control tumors to 23 days. Re-expression of ST7 was also associated with suppression of colony formation under anchorage-independent conditions in MDA-MB-231 breast cancer cells and ST7 mRNA expression was downregulated in 44% of primary breast cancers. Expression profiling of PC-3 cells revealed that ST7 predominantly induces changes in genes involved in re-modeling the extracellular matrix such as SPARC, IGFBP5 and several matrix metalloproteinases. These data indicate that ST7 may mediate tumor suppression through modification of the tumor microenvironment.

Highly sensitive detection of melanoma at an early stage based on the increased serum secreted protein acidic and rich in cysteine and glypican-3 levels

PURPOSE

There are no available tumor markers detecting primary melanoma at an early stage. The identification of such serum markers would be of significant benefit for an early diagnosis of melanoma. We recently identified glypican-3 (GPC3) as a novel tumor marker but could diagnose only 40% of melanomas. Thereby, we focused out attention on secreted protein acidic and rich in cysteine (SPARC) overexpressed in melanoma as another candidate for tumor marker.

EXPERIMENTAL DESIGN

Secreted SPARC protein was quantified using ELISA in the sera from 109 melanoma patients, five patients with large congenital melanocytic nevus, 61 age-matched healthy donors, and 13 disease-free patients after undergoing a surgical removal. We also quantified GPC3 and 5-S-cysteinyldopa in the same serum samples and compared these markers for their diagnostic value.

RESULTS

The serum SPARC concentrations in melanoma patients were greater than those in healthy donors (P = 0.001). When we fixed a cutoff value at the mean concentration plus 2 SD of the healthy donors, the serum SPARC was found to have increased in the sera of 36 of the 109 (33%) melanoma patients, whereas there were three (4.9%) false-positive cases of 61 healthy donors. Surprisingly, 19 of 36 patients showing increased SPARC levels were in stages 0 to II. The serum SPARC level decreased under the cutoff level in 10 of 13 patients after surgical removal. Using SPARC and GPC3 in combination thus enabled us to diagnose 47 of 75 (66.2%) melanoma patients at an early stage (0-II).

CONCLUSIONS

SPARC or its combination with GPC3 is thus considered a potentially useful tumor marker, especially for melanoma at an early stage.

Osteonectin influences growth and invasion of pancreatic cancer cells

OBJECTIVE

We sought to examine the expression and functional role of osteonectin in primary and metastatic pancreatic ductal adenocarcinoma (PDAC).

BACKGROUND

The glycoprotein osteonectin plays a vital role in cell-matrix interactions and is involved in various biologic processes. Overexpression of osteonectin is present in malignant tumors and correlates with disease progression and poor prognosis.

METHODS

Expression of osteonectin was analyzed by quantitative polymerase chain reaction and immunohistochemistry in pancreatic tissues and by enzyme-linked immunosorbent assay in the serum of patients and donors. Recombinant osteonectin and specific antisense oligonucleotides were used to examine the effects of osteonectin on induction of target genes, and on proliferation and invasiveness of pancreatic cancer cells.

RESULTS

There was a 31-fold increase in osteonectin mRNA levels in PDAC and a 16-fold increase in chronic pancreatitis as compared with the normal pancreas (P < 0.01). By immunohistochemistry, faint immunoreactivity was detected in the normal pancreas. In contrast, strong staining of the cancer cells was observed in addition to extensive osteonectin immunoreactivity in surrounding fibroblasts and in the extracellular matrix. In metastatic tissues, strong immunoreactivity was observed in fibroblasts and in extracellular matrix surrounding metastatic cancer cells, whereas the signal was absent in most tumor cells. In vitro studies showed that osteonectin was able to inhibit cancer cell growth while promoting invasiveness of pancreatic tumor cells.

CONCLUSION

Osteonectin is markedly overexpressed in pancreatic cancer and has the potential to increase the invasiveness of pancreatic cancer cells.