Thrombospondin-1 expression in oral squamous cell carcinomas: correlations with tumor vascularity, clinicopathological features and survival

Functions of Matricellular Proteins in Dental Tissues and Their Emerging Roles in Orofacial Tissue Development, Maintenance, and Disease

Matricellular proteins (MCPs) are defined as extracellular matrix (ECM) associated proteins that are important regulators and integrators of microenvironmental signals, contributing to the dynamic nature of ECM signalling. There is a growing understanding of the role of matricellular proteins in cellular processes governing tissue development as well as in disease pathogenesis. In this review, the expression and functions of different MP family members (periostin, CCNs, TSPs, SIBLINGs and others) are presented, specifically in relation to craniofacial development and the maintenance of orofacial tissues, including bone, gingiva, oral mucosa, palate and the dental pulp. As will be discussed, each MP family member has been shown to have non-redundant roles in development, tissue homeostasis, wound healing, pathology and tumorigenesis of orofacial and dental tissues.

Role of TSP-1 as prognostic marker in various cancers: a systematic review and meta-analysis

Background

Published studies present conflicting data regarding the impact of Thrombospondin-1 (TSP-1) expression on prognosis of various cancers. We performed this meta-analysis to illustrate the preliminary predictive value of TSP-1.

Methods

Twenty-four studies with a total of 2379 patients were included. A comprehensive literature search was performed by using PubMed, Cochrane Library, Web of Science, Embase, and hand searches were also conducted of relevant bibliographies. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) for patient survival and disease recurrence were initially identified to explore relationships between TSP-1 expression and patient prognosis.

Results

A total of 24 eligible studies were included in this meta-analysis. Our results showed that high level of TSP-1 was correlated significantly with poor overall survival (OS) (HR = 1.40, 95% CI: 1.17 ~ 1.68; P<0.001). However, high TSP-1 expression predicted no significant impact on progression-free survival (PFS)/ metastasis-free survival (MFS) (HR = 1.35, 95%CI: 0.87–2.10; P = 0.176) and disease-free survival (DFS)/ recurrence-free survival (RFS) (HR = 1.40, 95%CI: 0.77–2.53; P = 0.271). In addition, we performed subgroup analyses which showed that high TSP-1 expression predicted poor prognosis in breast cancer and gynecological cancer. Additionally, the relatively small number of studies on PFS/MFS and DFS/RFS is a limitation. The data extracted through Kaplan-Meier curves may not be accurate. Moreover, only English articles were included in this article, which may lead to deviations in the results.

Conclusions

Our findings indicated high TSP-1 expression may act as a promising biomarker of poor prognosis in cancers, especially in breast cancer and gynecological cancer.

[Relationship between thrombospondin-1 and the occurrence and development of oral and maxillofacial malignancy]

Thrombospondin-1 (TSP-1) is widely distributed in human tissues and is important in inhibiting angiogenesis.It also occupies an indispensable position in the formation, growth, differentiation, and metastasis of tumors in different tissues.TSP-1 plays an important role in the occurrence and development of various types of tumors. The inhibitory effect of TSP-1 on the angiogenesis and tumor development of oral and maxillofacial malignant tumors has been demonstrated in recent years. This paper reviews the findings and progress of TSP-1 research involving all kinds of tumors as well as oral and maxillofacial malignancies.

An integrated method for the identification of novel genes related to oral cancer

Cancer is a significant public health problem worldwide. Complete identification of genes related to one type of cancer facilitates earlier diagnosis and effective treatments. In this study, two widely used algorithms, the random walk with restart algorithm and the shortest path algorithm, were adopted to construct two parameterized computational methods, namely, an RWR-based method and an SP-based method; based on these methods, an integrated method was constructed for identifying novel disease genes. To validate the utility of the integrated method, data for oral cancer were used, on which the RWR-based and SP-based methods were trained, thereby building two optimal methods. The integrated method combining these optimal methods was further adopted to identify the novel genes of oral cancer. As a result, 85 novel genes were inferred, among which eleven genes (e.g., MYD88, FGFR2, NF-κBIA) were identified by both the RWR-based and SP-based methods, 70 genes (e.g., BMP4, IFNG, KITLG) were discovered only by the RWR-based method and four genes (L1R1, MCM6, NOG and CXCR3) were predicted only by the SP-based method. Extensive analyses indicate that several novel genes have strong associations with cancers, indicating the effectiveness of the integrated method for identifying disease genes.

Histomorphometric Analysis of Angiogenesis using CD31 Immunomarker and Mast Cell Density in Oral Premalignant and Malignant Lesions: A Pilot Study

INTRODUCTION

Mast cells have been implicated in promoting angiogenesis in malignant tumors of lung, oesophagus and breast, but there are few studies on Oral Squamous Cell Carcinomas (OSCC). Most oral squamous cell carcinomas arise from pre-existing precancerous lesions exhibiting epithelial dysplasia.

AIM

The present pilot study attempts to compare Mast Cell Density (MCD), Microvessel Density (MVD), Microvessel Area (MVA) histomorphometrically between normal buccal mucosa, severe epithelial dysplasia and OSCC and to correlate the role of mast cells and angiogenesis in tumor progression.

MATERIAL AND METHODS

The retrospective study was conducted on eight cases of OSCC, eight cases of severe epithelial dysplasia and five cases of normal buccal mucosa. Immunohistochemical staining with anti CD-31, to demonstrate angiogenesis and toluidine blue staining for mast cells were employed. MVA, MVD and MCD were calculated using the measurement tools of the image analysis software and compared between the groups. One way ANOVA (Analysis of Variance) was used for comparing the parameter for multiple groups followed by Games Howell test. To assess the relationship between micro vessel density and mast cell density, Karl Pearson's correlation was used.

RESULTS

MCD and MVD increased with disease progression and were statistically higher in OSCC than in severe epithelial dysplasia and normal buccal mucosa (p<0.001). MVA increased from normal to severe dysplasia and decreased from dysplasia to OSCC, may be due to revascularization of tumor tissue. A positive correlation was observed between MCD and MVD in OSCC and dysplasia, though were not statistically significant.

CONCLUSION

These findings suggest that mast cells may up regulate angiogenesis in OSCC. MCD and MVD may be used as indicators for disease progression.

THBS1 is induced by TGFB1 in the cancer stroma and promotes invasion of oral squamous cell carcinoma

BACKGROUND

THBS1 (thrombospondin-1) is the extracellular matrix (ECM) protein that affects diverse cellular activities. It constitutes the tumor stroma, but the role of THBS1 in oral squamous cell carcinoma (OSCC) development is unclear. The aim of this study was to clarify the relevance of THBS1 in the pathogenesis of OSCC.

MATERIALS AND METHODS

The expression of THBS1 was examined in 44 OSCC by immunohistochemical analysis and in 43 OSCC by cDNA microarray analysis. Cell culture experiments were conducted using human OSCC cell lines HSC3 and HO1N1 and mouse fibroblast ST2 cells to examine the effect of TGFB1 on THBS1 expression, and the effect of THBS1 on cellular behaviors.

RESULTS

THBS1 was specifically induced in the tumor microenvironment of OSCC. THBS1 appeared to be produced mainly by the stromal cells, but also by OSCC cells. TGFB1 stimulated THBS1 expression in ST2, primary fibroblasts, and the OSCC cells. THBS1 promoted migration and invasion of HSC3 and HO1N1 in transwell migration assays. THBS1 stimulated the expression of MMP3 (matrix metalloprotease 3), MMP9, MMP11, and MMP13 in ST2 cells and MMP3, MMP11, and MMP13 in HO1N1 cells. The RGD peptide suppressed the THBS1-stimulated migration and upregulation of MMP11 and MMP13.

CONCLUSIONS

THBS1 is a tumor-specific ECM protein that is induced by TGFB1 and promotes migration of cancer cells and stimulates the expression of MMPs partly through the integrin signaling, thereby favoring OSCC invasion.

Extracellular matrix proteins and tumor angiogenesis

Tumor development is a complex process that relies on interaction and communication between a number of cellular compartments. Much of the mass of a solid tumor is comprised of the stroma which is richly invested with extracellular matrix. Within this matrix are a host of matricellular proteins that regulate the expression and function of a myriad of proteins that regulate tumorigenic processes. One of the processes that is vital to tumor growth and progression is angiogenesis, or the formation of new blood vessels from preexisting vasculature. Within the extracellular matrix are structural proteins, a host of proteases, and resident pro- and antiangiogenic factors that control tumor angiogenesis in a tightly regulated fashion. This paper discusses the role that the extracellular matrix and ECM proteins play in the regulation of tumor angiogenesis.

Potential relevance of bell-shaped and u-shaped dose-responses for the therapeutic targeting of angiogenesis in cancer

Tumor angiogenesis, the growth of new blood vessels into tumors, facilitates tumor growth and thus represents an attractive therapeutic target. Numerous experimental angiogenesis inhibitors have been characterised and subsequently trialled in patients. Some of these agents have failed to show any substantial activity in patients. In contrast, others have been more successful, but even these provide only a few months extra patient survival. Recent work has focused on understanding the effects of anti-angiogenic agents on tumor biology and has revealed a number of new findings that may help to explain the limited efficacy of angiogenesis inhibitors. Herein, I review the evidence that hormetic dose-responses (i.e. bell-shaped and U-shaped dose-response curves) are often observed with anti-angiogenic agents. Agents reported to exhibit these types of dose-response include: 5-fluorouracil, ATN-161, bortezomib, cisplatin, endostatin, enterostatin, integrin inhibitors, interferon-α, plasminogen activator-1 (PAI-1), rapamycin, rosiglitazone, statins, thrombospondin-1, TGF-α1 and TGF-α3. Hormesis may also be relevant for drugs that target the vascular endothelial growth factor (VEGF) signalling pathway and for metronomic chemotherapy. Here I argue that hormetic dose-responses present a challenge for the clinical translation of several anti-angiogenic agents and discuss how these problems might be circumvented.

The ethyl alcohol extract of Hizikia fusiforme inhibits matrix metalloproteinase activity and regulates tight junction related protein expression in Hep3B human hepatocarcinoma cells

We tested the correlation between the tightness of tight junctions (TJs) and the anti-invasive activity of the ethyl alcohol extract of Hizikia fusiforme (EHF) in Hep3B human hepatocarcinoma cells. EHF inhibited cell proliferation, motility, and invasiveness, which were associated with increased TJ tightness, as demonstrated by an increase in transepithelial electrical resistance. EHF dose-dependently decreased the secretion of matrix metalloprotease-2 and -9, which correlated with a decrease in mRNA and protein expression, but increased tissue inhibitor of metalloproteinase-1 and -2 mRNA levels. Additionally, immunoblotting results indicated that EHF suppressed the major components of TJ, claudins (-1, -3, and -4), which play a key role in the control and selectivity of paracellular transport. These data indicate that EHF may inhibit cancer cell invasion through the tightening of TJs, which may counteract the up-regulation of claudins. Furthermore, EHF treatment decreased the expression of insulin-like growth factor-1 receptor proteins, while concurrently increasing that of thrombospondin-1 and E-cadherin. In conclusion, these results suggest that EHF treatment may inhibit tumor metastasis and invasion and therefore act as a dietary resource for decreasing the risk of developing cancer.

Enhanced interferon signaling pathway in oral cancer revealed by quantitative proteome analysis of microdissected specimens using 16O/18O labeling and integrated two-dimensional LC-ESI-MALDI tandem MS

Oral squamous cell carcinoma (OSCC) remains one of the most common cancers worldwide, and the mortality rate of this disease has increased in recent years. No molecular markers are available to assist with the early detection and therapeutic evaluation of OSCC; thus, identification of differentially expressed proteins may assist with the detection of potential disease markers and shed light on the molecular mechanisms of OSCC pathogenesis. We performed a multidimensional (16)O/(18)O proteomics analysis using an integrated ESI-ion trap and MALDI-TOF/TOF MS system and a computational data analysis pipeline to identify proteins that are differentially expressed in microdissected OSCC tumor cells relative to adjacent non-tumor epithelia. We identified 1233 unique proteins in microdissected oral squamous epithelia obtained from three pairs of OSCC specimens with a false discovery rate of <3%. Among these, 977 proteins were quantified between tumor and non-tumor cells. Our data revealed 80 dysregulated proteins (53 up-regulated and 27 down-regulated) when a 2.5-fold change was used as the threshold. Immunohistochemical staining and Western blot analyses were performed to confirm the overexpression of 12 up-regulated proteins in OSCC tissues. When the biological roles of 80 differentially expressed proteins were assessed via MetaCore analysis, the interferon (IFN) signaling pathway emerged as one of the most significantly altered pathways in OSCC. As many as 20% (10 of 53) of the up-regulated proteins belonged to the IFN-stimulated gene (ISG) family, including ubiquitin cross-reactive protein (UCRP)/ISG15. Using head-and-neck cancer tissue microarrays, we determined that UCRP is overexpressed in the majority of cheek and tongue cancers and in several cases of larynx cancer. In addition, we found that IFN-beta stimulates UCRP expression in oral cancer cells and enhances their motility in vitro. Our findings shed new light on OSCC pathogenesis and provide a basis for the future development of novel biomarkers.

Microvessel density >or=60 does not predict for outcome after radiation treatment for locally advanced head and neck squamous cell carcinoma: results of a correlative study from the Radiation Therapy Oncology Group (RTOG) 90-03 Trial

OBJECTIVES

To assess whether microvessel density (MVD), an immunohistochemical marker for tumor vascularity, predicts for radiotherapy (RT) outcome in locally advanced HNSCC patients.

METHODS

A total of 459 patients, enrolled on the RTOG 90-03 trial, had biopsy specimens submitted, and a value for MVD determined, prior to definitive RT. 450 patients were analyzable for this study. Tumor microvessels were stained for factor VIII-related antigen using a standard immunoperoxidase method. The mean number of stained microvessel profiles, from three x200 fields containing the highest MVD (hot spot), was recorded as the MVD. A prospective value of >or=60 was chosen as the threshold for high MVD, tumor vascularity.

RESULTS

The median follow-up for the analyzable patients with MVD assessment was 22.0 months and 79.1 months for all living patients. There were no differences concerning the pretreatment characteristics between those RTOG 90-03 patients with a value for MVD and those without a value for MVD. Thus, the present study cohort possessed comparable characteristics with the entire RTOG 90-03 population. MVD values ranged from 5 to 80, with a median value of 30. Only 37 of 450 (8.2%) patients possessed an MVD >or=60. There were no outcome differences for patients with MVD <60 versus >or=60 on multivariate analysis for time to local-regional failure (P = 0.89), time to distant metastasis (P = 0.80), disease-free survival (P = 0.46), and overall survival (P = 0.39).

CONCLUSIONS

In this large, correlative study, a MVD >or=60, ie, high tumor vascularity, did not predict for outcome in locally advanced head and neck squamous cell carcinoma patients treated with radiotherapy.

Induction of Egr-1 is associated with anti-metastatic and anti-invasive ability of beta-lapachone in human hepatocarcinoma cells

beta-lapachone, a quinone compound obtained from the bark of the lapacho tree (Tabebuia avellanedae), was reported to have anti-inflammatory and anti-cancer activities. In this study, we investigated novel functions of beta-lapachone in terms of anti-metastasis and anti-invasion abilities using human hepatocarcinoma cell lines, HepG2 and Hep3B. beta-lapachone dose-dependently inhibited cell viability and migration of both HepG2 and Hep3B cells, as determined by methylthiazoletetrazolium (MTT) assay and wound healing assay. RT-PCR and Western blot data revealed that beta-lapachone dramatically increased the levels of protein, as well as mRNA expression of early growth response gene-1 (Egr-1) and throbospondin-1 (TSP-1) at an early point in time, and then decreased in a time-dependent manner. In addition, down-regulation of Snail and up-regulation of E-cadherin expression were observed in beta-lapachone-treated HepG2 and Hep3B cells, and this the associated with decreased invasive ability as measured by matrigel invasion assay. Taken together, our results strongly suggest that beta-lapachone may be expected to inhibit the progression and metastasis of hepatoma cells, at least in part by inhibiting the invasive ability of the cells via up-regulation of the expression of the Egr-1, TSP-1, and E-cadherin.

Co-expression of angiogenic markers and associations with prognosis in advanced epithelial ovarian cancer: a Gynecologic Oncology Group study

OBJECTIVES

The aim of this study was to explore the co-expression and prognostic relevance of thrombospondin-1 (THBS-1), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and VEGF receptor 1 (VEGFR-1) in epithelial ovarian cancer (EOC).

METHODS

Frozen tumor specimens with defined p53 status were obtained from 67 patients with previously untreated advanced-stage EOC who participated in a Gynecologic Oncology Group specimen-banking protocol and a phase III treatment protocol. Relative expression of the angiogenic markers was quantified by immunoblot analysis and categorized at the median angiogenic marker/actin ratio. p-values are provided as an indication of confidence in the results and to prioritize further testing.

RESULTS

An association was observed between categorized VEGF and p53 overexpression (p=0.022), and between VEGFR-1 and race (p=0.027) or histologic subtype (p=0.007). Unadjusted Cox regression analyses indicated that high compared with low THBS-1, but not VEGF or VEGFR-1, was associated with an increased risk of disease progression (hazard ratio [HR]=2.19; 95% confidence interval [CI]=1.29-3.71; p=0.004) and death (HR=1.93; 95% CI=1.12-3.32; p=0.018) whereas bFGF was associated with a reduced risk of disease progression (HR=0.60; 95% CI=0.36-0.99; p=0.046) and death (HR=0.54; 95% CI=0.32-0.93; p=0.026). After adjusting for prognostic factors including clinical characteristics and p53 overexpression, THBS-1 but not bFGF, VEGF or VEGFR-1 was associated with progression-free and overall survival.

CONCLUSIONS

These data suggest that high THBS-1 is an independent predictor of worse progression-free and overall survival in women with advanced-stage EOC. A larger prospective study is warranted for validation of these findings.

Thrombospondins deployed by thrombopoietic cells determine angiogenic switch and extent of revascularization

Thrombopoietic cells may differentially promote or inhibit tissue vascularization by releasing both pro- and antiangiogenic factors. However, the molecular determinants controlling the angiogenic phenotype of thrombopoietic cells remain unknown. Here, we show that expression and release of thrombospondins (TSPs) by megakaryocytes and platelets function as a major antiangiogenic switch. TSPs inhibited thrombopoiesis, diminished bone marrow microvascular reconstruction following myelosuppression, and limited the extent of revascularization in a model of hind limb ischemia. We demonstrate that thrombopoietic recovery following myelosuppression was significantly enhanced in mice deficient in both TSP1 and TSP2 (TSP-DKO mice) in comparison with WT mice. Megakaryocyte and platelet levels in TSP-DKO mice were rapidly restored, thereby accelerating revascularization of myelosuppressed bone marrow and ischemic hind limbs. In addition, thrombopoietic cells derived from TSP-DKO mice were more effective in supporting neoangiogenesis in Matrigel plugs. The proangiogenic activity of TSP-DKO thrombopoietic cells was mediated through activation of MMP-9 and enhanced release of stromal cell-derived factor 1. Thus, TSP-deficient thrombopoietic cells function as proangiogenic agents, accelerating hemangiogenesis within the marrow and revascularization of ischemic hind limbs. As such, interference with the release of cellular stores of TSPs may be clinically effective in augmenting neoangiogenesis.

Extraction of RNA from archival tissues and measurement of thrombospondin-1 mRNA in normal, dysplastic, and malignant oral tissues

Thrombospondin-1 (TSP-1) is an extracellular matrix glycoprotein implicated in the regulation of angiogenesis and tumour development. Our objectives were to ascertain the quantity and quality of RNA extracted from archival, formalin-fixed, paraffin embedded, oral tissues and their application in measuring the concentrations of TSP-1 mRNA in these tissues. We compared three techniques of isolation of RNA as well as related experimental variables. TSP-1 mRNA was measured in specimens of normal, dysplastic, and malignant oral tissues by real-time reverse transcriptase polymerase chain reaction (RT-PCR). RNA suitable for analysis by real-time RT-PCR was obtained by the three techniques tested, although the yield varied depending on the protocol used (range 0.2-3.6 microg/mm(3)). The mean (S.D.) concentrations of TSP-1 mRNA relative to 18S were 21.1 (7.2) in normal oral tissues (n=9), 11.0 (8.2) in dysplastic tissue (n=8) and 7.3 (5.3) in carcinomatous tissue (n=17). The difference between normal and carcinomatous specimens was significant (p=0.01). This reduction in expression of TSP-1 mRNA from normal to dysplasia to carcinoma may favour the angiogenic drive that accompanies the development of oral tumours.

Regulation of tumor angiogenesis by thrombospondin-1

Angiogenesis plays a critical role in the growth and metastasis of tumors. Thrombospondin-1 (TSP-1) is a potent angiogenesis inhibitor, and down-regulation of TSP-1 has been suggested to alter tumor growth by modulating angiogenesis in a variety of tumor types. Expression of TSP-1 is up-regulated by the tumor suppressor gene, p53, and down-regulated by oncogenes such as Myc and Ras. TSP-1 inhibits angiogenesis by inhibiting endothelial cell migration and proliferation and by inducing apoptosis. In addition, activation of transforming growth factor beta (TGF-beta) by TSP-1 plays a crucial role in the regulation of tumor progression. An understanding of the molecular basis of TSP-1-mediated inhibition of angiogenesis and tumor progression will aid in the development of novel therapeutics for the treatment of cancer.

Suppression of tumor cell invasion by cyclooxygenase inhibitors is mediated by thrombospondin-1 via the early growth response geneEgr-1

Cyclooxygenase (COX) inhibitors have antitumorigenic activity and increase the expression of the early growth response gene Egr-1, a tumor suppressor gene and transcription factor. In this study, we have investigated the gene regulatory and anti-invasive activity of two traditional nonsteroidal anti-inflammatory drugs (NSAID), sulindac sulfide and indomethacin. These compounds inhibited tumor cell invasion and induced Egr-1 expression in lung adenocarcinoma A549 cells. Overexpression of Egr-1 reduced cellular invasion in the Matrigel system, whereas suppression of Egr-1 by small interference RNA (siRNA) attenuated the inhibition of Matrigel invasion by these compounds, indicating that Egr-1 is responsible for the decrease in invasion reported following treatment with NSAIDs. Egr-1-overexpressing cells were analyzed for genes involved in invasion and metastasis. Thrombospondin-1 (TSP-1) an antiangiogenic and anti-invasion protein was up-regulated by Egr-1 overexpression, which was confirmed following treatment with sulindac sulfide. Furthermore, the induction of TSP-1 by sulindac sulfide was blocked by Egr-1 siRNA. When TSP-1 was sequestered by the addition of anti-TSP-1 antibody, the inhibition of invasion by sulindac sulfide was attenuated, indicating that TSP-1 is involved in the inhibition of invasion by NSAIDs. We used the Min mouse model to determine if sulindac sulfide would increase Egr-1 and TSP-1 in vivo, because this model is widely used to study the effects of NSAIDs on tumor formation. Treatment of Min mice with concentrations of sulindac sulfide that inhibit tumor formation increased the expression of Egr-1 and TSP-1 in colonic tissues and in the polyps of these mice. This is the first report suggesting that COX inhibitors suppress tumor cell invasion via TSP-1, which occurs downstream of Egr-1.

Immunohistochemical expression of thrombospondin-1 in invasive vulvar squamous cell carcinoma

OBJECTIVES

Thrombospondin-1 (TSP-1) is a multifunctional matricellular glycoprotein involved in several mechanisms critical to the formation and progression of solid tumors including cell adhesion, proliferation, migration, invasion, and angiogenesis. The present study was designed to investigate the expression of TSP-1 in invasive vulvar squamous cell carcinoma.

METHODS

A total of 75 invasive vulvar squamous cell carcinomas were evaluated for TSP-1 expression by immunohistochemistry. Results were correlated with the clinicopathologic parameters including tumor stage, groin lymph node status, tumor grade, patient's age, patients' disease-free, and overall survival.

RESULTS

TSP-1 expression was detected in 35/75 (46.7%) specimens of invasive vulvar squamous cell carcinomas. The expression of TSP-1 was generally localized to the cytoplasm and occasionally seen in the nucleus. An increased TSP-1 expression was detected in patients with an advanced tumor stage (P = 0.01) and a positive groin lymph nodes status (P = 0.01). Tumor stage and groin lymph node status were associated with patients' disease-free and overall survival. All other parameters failed to be of prognostic significance.

CONCLUSIONS

We are the first to report on the immunohistochemical expression of TSP-1 in invasive vulvar squamous cell carcinoma. Increased TSP-1 expression was associated with an advanced tumor stage and a positive groin lymph node status, suggesting its pro-angiogenic potential in vulvar carcinogenesis.

Expression of thrombospondin-1 is correlated with microvessel density in gastric carcinoma

Thrombospondin-1 (TSP-1) has been shown to play a role in angiogenesis in a variety of cancers, but some studies indicated a difference in the mechanism of TSP-1 on neovascularization according to organ or histological type. Wild-type p53 protein has been shown to induce TSP-1 expression. We examined the expression of TSP-1 protein in 80 gastric carcinomas using immunohistochemistry and studied the relationship with microvessel counts, p53 expression and clinicopathological factors. We also performed reverse-transcriptase polymerase chain reaction analysis for the TSP-1 mRNA expression in gastric carcinoma cell lines and gastric cancer tissue after laser capture microdissection. Strong expression of TSP-1 protein was detected in 30 (38%) of the 80 cases. Positive staining for TSP-1 was seen in the cytoplasm of the cancer cells. TSP-1 mRNA expression was confirmed in a majority of gastric carcinoma cell lines and carcinoma tissues. Microvessel counts were significantly higher in tumors with strong TSP-1 protein expression than in those without expression or weak expression of TSP-1 ( P=0.011). No significant correlation was found between TSP-1 expression and p53 staining and clinicopathological factors. Our results support an idea that increased TSP-1 expression may be associated with an angiogenic phenotype in gastric carcinoma and suggest that TSP-1 may play diverse roles in each organ.

Thymidine phosphorylase expression in oral squamous cell carcinoma

Thymidine phosphorylase (TP), as an enzyme involved in DNA synthesis, catalyzes the reversible conversion of thymidine to thymine. It is also identical to the angiogenic factor, platelet-derived endothelial cell growth factor. We examined TP expression using immunohistochemistry in 66 archival samples obtained from the patients with primary oral squamous cell carcinoma (SCC) and investigated its relation to tumor vascularity, cell proliferation, apoptosis, clinicopathological features and survival. TP expression was identified in cytonucleus and/or cytoplasm in carcinomas, but was not identified in histologically normal epithelia distant to tumor in most cases. No significant difference of microvessel density (MVD) was found between the carcinomas with high TP expression (H-TP) and low TP expression (L-TP). The percentages of proliferative cells marked by Ki-67 staining in H-TP carcinomas was significantly higher than that in L-TP carcinomas (P=0.0222). The apoptotic indice (AI) in H-TP carcinomas tended to be lower than that in L-TP carcinomas (P=0.0723). Moreover, the level of TP expression was significantly correlated the pattern of tumor invasion (P=0.0146) and marginally correlated with lymph nodal metastasis (P=0.0804). Our results suggested that TP enzyme may play a role in promotion of tumor growth in oral SCC, and that its expression can be indicative of tumor aggressiveness in this tumor type.

Thrombospondin-1 as an endogenous inhibitor of angiogenesis and tumor growth

Thrombospondin-1 (TSP-1) is a matricellular glycoprotein that influences cellular phenotype and the structure of the extracellular matrix. These effects are important components of the tissue remodeling that is associated with angiogenesis and neoplasia. The genetic mutations in oncogenes and tumor suppressor genes that occur within tumor cells are frequently associated with decreased expression of TSP-1. However, the TSP-1 that is produced by stromal fibroblasts, endothelial cells and immune cells suppresses tumor progression. TSP-1 inhibits angiogenesis through direct effects on endothelial cell migration and survival and through indirect effects on growth factor mobilization. TSP-1 that is present in the tumor microenvironment also acts to suppress tumor cell growth through activation of transforming growth factor beta in those tumor cells that are responsive to TGF beta. In this review, the molecular basis for the role of TSP-1 in the inhibition of tumor growth and angiogenesis is summarized.