Expression of caveolin-1 in mucoepidermoid carcinoma of the salivary glands: correlation with vascular endothelial growth factor, microvessel density, and clinical outcome

Expression of caveolin-1 in tooth germ, ameloblastoma and ameloblastic carcinoma

BACKGROUND

The caveolin-1 protein (structural component of membrane caveolae) plays important roles in several biological functions, such as endocytosis, cell adhesion, and cell signaling. However, this protein has been associated with mechanisms of tumorigenesis in several neoplasms. The expression patterns and roles of caveolin-1 in the oral epithelium and in embryonic and odontogenic tumor tissues are still unclear.

MATERIAL AND METHODS

The expression of caveolin-1 was evaluated in samples of the normal gingival epithelium (n=7), human tooth germ (TG) (n=12), ameloblastoma (AM) (n=83), and ameloblastic carcinoma (AC) (n=9) by immunohistochemistry. Additionally, AM samples were analyzed by qRT-PCR and Western blot.

RESULTS

Most TG (91.7%), AM (73.5%) and AC (100%) samples showed diverse patterns of immunohistochemical positivity for caveolin-1, while only one gingival sample was positive. The transcript levels of cav-1 were significantly upregulated by 14.9-fold in AM tissue (P = 0.0014) compared to those in normal gingival epithelial tissue, as shown by qRT-PCR. Presence of caveolin-1 protein was confirmed by Western blot analysis. The caveolin-1 immunoexpression patterns throughout the stages of TG show its importance during odontogenesis.

CONCLUSIONS

The overexpression of caveolin-1 in AM and AC compared to its expression in normal gingival epithelium (adult tissue) suggests a possible role of caveolin-1 in protumoral events, but due to the similar immunoexpression observed in AM and AC, caveolin-1 may not necessarily participate in the malignant transformation process. However, future studies are needed to clarify and confirm these hypotheses.

Prognostic value of the immunohistochemical expression of vascular endothelial growth factors in malignant salivary gland neoplasms: a systematic review and meta-analysis

BACKGROUND

 The immunohistochemical expression of vascular endothelial growth factor is a prognostic marker in several cancer types. In salivary gland tumors, the association between vascular endothelial growth factor and prognosis remains unclear. The purpose of this study was to perform a systematic review and meta-analysis to assess whether the immunohistochemical expression of vascular endothelial growth factor in patients with salivary gland neoplasms presents prognostic value.

MATERIAL AND METHODS

Immunohistochemical studies assessing the predictive value of vascular endothelial growth factor in salivary gland neoplasms were systematically reviewed using PubMed, Scopus, Embase, Cochrane Library, and Web of Science databases. It was assessed any survival rates. The fixed-effect model with an adjusted hazard ratio (HR) and 95% confidence intervals (95% CI) as effect measures were performed in the meta-analysis. The Quality in Prognosis Studies (QUIPS) tool was used to assess the quality of the included studies, and the evidence quality was assessed by the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) system.

RESULTS

The immunohistochemical overexpression of vascular endothelial growth factor in patients with salivary gland neoplasms was associated with shortened survival (HR=5.37, 95% CI: 2.67-10.83, P = 0.00001). In addition, the presence of vascular endothelial growth factor was tightly associated with tumor size, lymph node metastasis, clinical stage, perineural invasion, vascular invasion, poor local control of the disease, and recurrence.

CONCLUSIONS

The immunohistochemical overexpression of vascular endothelial growth factor in patients with salivary gland neoplasms has prognostic value and was associated with decreased survival time. However, more primary well-designed studies are necessary to increase the level of evidence.

The Impact of Angiogenesis in the Most Common Salivary Gland Malignant Tumors

Salivary gland carcinomas (SGCs) represent a group of rare tumors, with complete surgical resection being the main treatment option. Therapeutic armory for cases of locally aggressive, recurrent, and/or metastatic SGCs, though, remains poor since they exhibit high rates of resistance to systematic therapy. Angiogenesis is considered one of the contemporary hallmarks of cancer and anti-angiogenic factors have already been approved for the treatment of several cancer types. This review aims to summarize, in a histotype-specific manner, the most current available data on the angiogenic factors implicated in SGC angiogenesis, in order to highlight the differences between the most common SGC histotypes and the factors that may have a potential role as therapeutic targets.

Caveolin-1 Expression Together with VEGF can be a Predictor for Lung Metastasis and Poor Prognosis in Osteosarcoma

Caveolin-1, the major protein component of caveolae, plays vital functions in tumorigenesis and metastasis. Previous evidence demonstrated the positive role of Caveolin-1 in the regulation of endothelial cell differentiation and the involvement of Caveolin-1 in vascular endothelial growth factor (VEGF) mediated angiogenesis. The correlation of Caveolin-1 expression and angiogenesis is not yet elucidated in osteosarcoma. This study aimed to investigate the expression levels of Caveolin-1 and VEGF in osteosarcoma and their associations with clinicopathological data. This study included 66 formalin-fixed and paraffin embedded osteosarcoma tissue samples. The expression levels of Caveolin-1 and VEGF were assessed by immunohistochemistry. Then associations with clinicopathological variables and the correlation between both markers were evaluated statistically. We also investigated the expression of Caveolin-1 and VEGF values in gene microarrays of osteosarcoma patients and cell lines by using GEO data sets on https://www.ncbi.nlm.nih.gov. Caveolin-1 and VEGF were expressed in 19.6% and 77.3%, respectively. Caveolin-1 expression was associated positively with osteoblastic histological subtype (P < 0.0001). VEGF expression showed positive association with patient age, histological grade and clinical stage (P = 0.031, P = 0.024 and P < 0.001; respectively). An inverse correlation between Caveolin-1 and VEGF expressions in osteosarcoma was found (r = 0.2 P = 0.04). In silico analysis of Caveolin-1 and VEGF expression supported our results. Our results suggest that Caveolin-1 may act as a tumor suppressor in osteosarcoma. Down-regulation of Caveolin-1 can be used as an indicator for poor prognosis in osteosarcoma patients. Meanwhile, overexpression of VEGF is a predictor of pulmonary metastasis and poor prognosis.

Expression of Vascular Endothelial-Cadherin in Mucoepidermoid Carcinoma: Role in Cancer Development

Objectives:

Mucoepidermoid carcinoma (MEC) accounts for 35% of all malignant salivary gland tumors. Previous investigations have shown that vasculogenic mimicry (VM) exists in many cancers which can be used as a prognostic factor of poor prognosis. Elevated expression level of vascular endothelial (VE)-cadherin has been implicated in cancer neovascularization, growth, and progression. The current study aimed to study the presence of VE-cadherin in VM channels and tumor cells in different grades of MEC.

Materials and Methods:

A total of 63 MEC samples (21 samples in each grade) were collected from the archive of pathology department of Besat Educational Hospital, Hamadan, Iran, from 2002 to 2016. Hematoxylin and eosin staining was performed to confirm the previous diagnosis. The specimens were then processed for immunohistochemistry analysis. Then, periodic acid–Schiff staining was performed. Analyses were conducted through SPSS software version 22.0 (SPSS, Inc., Chicago, IL, USA). Chi-square test was used to examine the differences between categorical variables. Significance level was set at 0.05. Pearson's correlation was used to assess the co-localization of the marker.

Results:

A total of 63 samples (35 men; 55.6%, and 28 women; 44.4%) were used for immunohistochemical study. There were statistically significant differences between tumor grade and the expression levels of VE-cadherin (P = 0.000), between tumor grade and VM formation (P = 0.000), and also between tumor grade and microvessel density (MVD) (P = 0.000). Additionally, there was a strong positive correlation between tumor grade and VE-cadherin expression level (Pearson's r = 0.875, P < 0.000).

Conclusions:

Our results may disclose a definite relationship between VE-cadherin expression level, VM, epithelial–mesenchymal transition, cancer stem cells, and MVD in MEC samples. Thus, it is reasonable to suggest that VE-cadherin is related to angiogenesis and VM formation in MECs.

Expression and significance of caveolin-1 in hepatitis B virus-associated hepatocellular carcinoma

Caveolin-1 (Cav-1) is a major component of caveolae and has been recently identified as a tumor suppressor. As little is known about Cav-1 in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC), the aim of the present study was to investigate the expression and significance of Cav-1 in HBV-associated HCC. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect the mRNA expression level of Cav-1 in 40 cases of HBV-associated HCC, the corresponding 11 non-tumor cases of HBV-associated chronic hepatitis, 29 non-tumor cases of HBV-associated cirrhosis and 6 cases of normal liver tissues. Immunohistochemical analysis indicated the expression of Cav-1, cluster of differentiation 34 and vascular endothelial growth factor (VEGF) in HBV-associated HCC tissue samples. In addition, the association of Cav-1 expression with angiogenesis and clinicopathological characteristics of HBV-associated HCC was also analyzed. RT-PCR results demonstrated that the expression rate of Cav-1 mRNA in HBV-associated HCC, non-tumor HBV-associated chronic hepatitis and cirrhosis liver tissues and control normal liver tissues from patients with metastatic carcinoma was 92.5, 85.0 and 16.7%, respectively. mRNA expression level of Cav-1 was significantly increased in chronic hepatitis, cirrhosis and HBV-associated HCC livers compared with normal control livers (P<0.05 and P<0.01, respectively). Cav-1 protein was detected by immunohistochemistry in 80% of the samples of HBV-associated HCC. Furthermore, Cav-1 and VEGF protein expression levels were correlated with microvessel density (MVD; γ_s<0.46, P=0.01 and γ_s<0.31, P=0.05, respectively). In addition, Cav-1 expression and MVD were significantly associated with metastasis (P=0.031 and P=0.046, respectively). In conclusion, Cav-1 may have an important role in the carcinogenesis and progression of HBV-associated HCC and angiogenesis may be affected by Cav-1 during this process.

Immunoexpression of GLUT-1 and angiogenic index in pleomorphic adenomas, adenoid cystic carcinomas, and mucoepidermoid carcinomas of the salivary glands

This study aimed to evaluate and compare the immunoexpression of glucose transporter-1 (GLUT-1) and angiogenic index between pleomorphic adenomas (PAs), adenoid cystic carcinomas (ACCs), and mucoepidermoid carcinomas (MECs) of the salivary glands, and establish associations with the respective subtype/histological grade. Twenty PAs, 20 ACCs, and 10 MECs were submitted to morphological and immunohistochemical analysis. GLUT-1 expression was semi-quantitatively evaluated and angiogenic index was assessed by microvessel counts using anti-CD34 antibody. Higher GLUT-1 immunoexpression was observed in the MECs compared to PAs and ACCs (p = 0.022). Mean number of microvessels was 66.5 in MECs, 40.4 in PAs, and 21.2 in ACCs (p < 0.001). GLUT-1 expression and angiogenic index showed no significant correlation in the tumors studied. Results suggest that differences in biological behavior of the studied tumors are related to GLUT-1. Benign and malignant salivary gland tumors differ in the angiogenic index; however, angiogenesis may be independent of the tumor cell's metabolic demand.

Caveolin-1 overexpression in benign and malignant salivary gland tumors

Caveolin-1, a tyrosine-phosphorylated protein, is supposed to have different regulatory roles as promoter or suppressor in many human cancers. However, no published study concerned its expression in benign and malignant salivary gland tumors. The aim of this study was to evaluate and compare the expression of Cav-1 in the most common benign and malignant salivary gland tumors and evaluate its correlation with proliferation activity. In this cross-sectional retrospective study, immunohistochemical expression of caveolin-1 and Ki67 were evaluated in 49 samples, including 11 normal salivary glands, 15 cases of pleomorphic adenoma (PA), 13 adenoid cystic carcinomas (AdCC), and 10 mucoepidermoid carcinomas (MEC). The expression of Cav-1 was seen in 18 % of normal salivary glands and 85 % of tumors. The immunoreaction in the tumors was significantly higher than normal tissues (P = 0.001), but the difference between benign and malignant tumors was not significant (P = 0.07). Expression of Cav-1 was correlated with Ki67 labeling index in PAs, but not in malignant tumors. Cav-1 expression was not in association with tumor size and stage. Overexpression of Cav-1 was found in salivary gland tumors in comparison with normal tissues, but no significant difference was observed between benign and malignant tumors. Cav-1 was inversely correlated with proliferation in PA. Therefore, this marker may participate in tumorigenesis of salivary gland tumors and may be a potential biomarker for cancer treatments.

Lesser-Known Molecules in Ovarian Carcinogenesis

Currently, the deciphering of the signaling pathways brings about new advances in the understanding of the pathogenic mechanism of ovarian carcinogenesis, which is based on the interaction of several molecules with different biochemical structure that, consequently, intervene in cell metabolism, through their role as regulators in proliferation, differentiation, and cell death. Given that the ensemble of biomarkers in OC includes more than 50 molecules the interest of the researchers focuses on the possible validation of each one's potential as prognosis markers and/or therapeutic targets. Within this framework, this review presents three protein molecules: ALCAM, c-FLIP, and caveolin, motivated by the perspectives provided through the current limited knowledge on their role in ovarian carcinogenesis and on their potential as prognosis factors. Their structural stability, once altered, triggers the initiation of the sequences characteristic for ovarian carcinogenesis, through their role as modulators for several signaling pathways, contributing to the disruption of cellular junctions, disturbance of pro-/antiapoptotic equilibrium, and alteration of transmission of the signals specific for the molecular pathways. For each molecule, the text is built as follows: (i) general remarks, (ii) structural details, and (iii) particularities in expression, from different tumors to landmarks in ovarian carcinoma.

Immunohistochemical analysis of CD34 expression in salivary gland tumors

Background:

Tumor growth depends on angiogenesis which is assessed by measuring the tumor microvessel density (MVD) through CD34 immunostaining. The present study was performed to evaluate the situation of angiogenic activity in salivary gland neoplasms. The possible role of CD34 in progression and invasion of salivary gland tumors is also investigated.

Materials and Methods:

Tissue specimens of 15 pleomorphic adenoma (PA) and 15 malignant salivary gland tumors including mucoepidermoid carcinoma (MEC), adenoid cystic carcinoma (AdCC) and salivary duct carcinoma (SDC) were immunostained for CD34 protein. The most vascularized areas at low power magnification (hotspots) were selected for vessel counting at ×400 magnification. Then, the mean number of microvessels in three fields within the tumor mass was calculated.

Results:

MVD in PA and malignant salivary gland tumors were 10.93 ± 5.95 and 26.46 ± 7.32, respectively. Tumor angiogenesis in PA was much lower than other lesions (P < 0.05). No significant difference was observed between malignant tumors (P > 0.05).

Conclusion:

Salivary gland carcinomas demonstrated higher vascular density than benign PA despite of cell types and architecture. The reason for this higher angiogenic activity could be related to metabolic characteristics of malignant cells.

Genetic Variants in Caveolin-1 and RhoA/ROCK1 Are Associated with Clear Cell Renal Cell Carcinoma Risk in a Chinese Population

Background

The RhoA/ROCK pathway and Caveolin-1 (Cav-1) participate in the process of tumorigenesis in numerous types of cancer. Up-regulation of RhoA/ROCK and Cav-1 expression is considered to be associated with the development and progression of clear cell renal cell carcinoma (ccRCC). We investigated the association between genetic variations of RhoA/ROCK and Cav-1 and the risk of ccRCC in the Chinese population.

Methods

Between May 2004 and March 2014, a total of 1,248 clear cell renal cell carcinoma cases and 1,440 cancer-free controls were enrolled in this hospital-based case-control study. Nine SNPs in RhoA/ROCK and Cav-1 were genotyped using the TaqMan assay.

Result

We found two SNPs (Cav-1 rs1049334 and ROCK1 rs35996865) were significantly associated with the increasing risk of ccRCC (P = 0.002 and P < 0.001 respectively). The analysis of combined risk alleles revealed that patients with 2–4 risk alleles showed a more remarkable growth of ccRCC risk than the patients with 0–1 risk alleles(OR = 1.66, 95%CI = 1.31–2.11, P < 0.001). Younger subjects (P = 0.001, OR = 1.83, 95%CI = 1.30–2.57), higher weight subjects (P = 0.001, OR = 1.76, 95%CI = 1.25–2.47), female subjects (P = 0.007, OR = 1.75, 95% CI = 1.17–2.62), nonsmokers (P < 0.001, OR = 1.67, 95%CI = 1.26–2.23), drinkers (P = 0.025, OR = 1.75, 95% CI = 1.07–2.85), subjects with hypertension (P = 0.025, OR = 1.75, 95% CI = 1.07–2.85) and diabetes (P = 0.026, OR = 4.31, 95% CI = 1.19–15.62) showed a stronger association between the combined risk alleles and the risk of ccRCC by using the stratification analysis. Furthermore, we observed higher Cav-1 mRNA levels in the presence of the rs1049334 A allele in normal renal tissues.

Conclusion

Our results indicate that the two SNPs (Cav-1 rs1049334 and ROCK1 rs35996865) and genotypes with a combination of 2–4 risk alleles were associated with the risk of ccRCC. The functional SNP rs1049334 may affect the risk of ccRCC by altering the expression of Cav-1 and the relevance between the risk effects and the functional impact of this polymorphism needs further validation.

Vascular endothelial growth factor immunoexpression is increased in malignant salivary gland tumors

Salivary gland tumors (SGTs) consist of a heterogeneous group of lesions accounting for 3% to 10% of all head and neck neoplasms. Little is known about their angiogenic properties, and despite vascular endothelial growth factor (VEGF) has been previously studied in these lesions, further investigations are warranted to better determine its clinical and prognostic significance. In the current study, a total of 132 formalin-fixed, paraffin-embedded SGTs were organized in tissue microarray blocks and submitted to immunohistochemistry against VEGF protein. Slides were scanned and immunoreactions analyzed using Pixelcount V9 algorithm (Aperio Technologies Inc, Vista, CA, USA). Clinical and follow-up data were retrieved from patients' medical charts. Tumors included 50 cases of pleomorphic adenoma, 32 mucoepidermoid carcinomas, 30 adenocarcinomas not otherwise specified, and 20 adenoid cystic carcinomas. A slight male preponderance was found (1.1:1.0), with a mean age of 47.5 years. Parotid gland was the most affected location. Vascular endothelial growth factor expression was found in the cytoplasm of all cases analyzed with variable intensity, proving to be overexpressed in malignant tumors if compared with pleomorphic adenoma. A significant correlation of VEGF reactivity was found only with age, showing no further significant associations. Age and presence of paresthesia were the only features that predicted a lower specific survival rate under univariate and multivariate analyses. Log-rank test evidenced VEGF high expression as a potential determinant of reduced survival, although a statistical significance could not be reached. Hence, considering VEGF overexpression in malignant tumors and its potential association with a lower survival rate, this protein might be associated with SGTs pathogenesis and aggressiveness.

Caveolin and cavin family members: dual roles in cancer

Caveolae are specialized plasma membrane subdomains with distinct lipid and protein compositions, which play an essential role in cell physiology through regulation of trafficking and signaling functions. The structure and functions of caveolae have been shown to require the proteins caveolins. Recently, members of the cavin protein family were found to be required, in concert with caveolins, for the formation and function of caveolae. Caveolins have a paradoxical role in the development of cancer formation. They have been involved in both tumor suppression and oncogenesis, depending on tumor type and progress stage. High expression of caveolins and cavins leads to inhibition of cancer-related pathways, such as growth factor signaling pathways. However, certain cancer cells that express caveolins and cavins have been shown to be more aggressive and metastatic because of their increased potential for anchorage-independent growth. Here, we will survey the functional roles of caveolins and of different cavin family members in cancer regulation.

Value of caveolin-1 in cancer progression and prognosis: Emphasis on cancer-associated fibroblasts, human cancer cells and mechanism of caveolin-1 expression (Review)

Caveolin-1 (Cav-1) is found predominately in terminally differentiated cells, such as adipocytes, endothelia and smooth muscle cells, as well as type I pneumocytes. As a main structural component of caveolae, Cav-1 is important in modulating cellular signaling. In the present study, the expression and clinical role of Cav-1 were analyzed in tumor stromal and human cancer cells, respectively. The results of previous studies have shown that the downregulation of tumor stromal Cav-1 promotes tumor survival and predicts a poor tumor prognosis, predominantly concentrating on the mechanism of the metabolism of the cancer microenvironment (according to the autophagic tumor stroma model of cancer metabolism and the reverse Warburg effect). However, contradictory results concerning the expression, clinical roles and associated mechanisms of Cav-1 have been reported. An improved understanding of Cav-1 expression in tumor stromal and cancer cells will increase knowledge with regard to the clinical value of Cav-1 and its detailed mechanisms. This review summarizes the novel data concerning the clinical values and probable mechanisms of Cav-1 expression in tumor stromal (predominantly in cancer-associated fibroblasts) and cancer cells, respectively.

Salivary mucoepidermoid carcinoma revisited

Clinicopathological features, prognosis and therapeutic strategies for mucoepidermoid carcinoma originating in salivary and salivary-type glands of the head and neck are reviewed. We emphasise histopathological aspects, appraise the value of histochemistry, electron microscopy, immunohistochemistry and cytophotometry, and discuss histogenesis and characteristic gene translocations. We additionally consider possible diagnostic difficulties, problems related to histological grading and accuracy of existing literature, and areas of controversy or uncertainty which may benefit from further investigations.

Prognostic value of vascular endothelial growth factor in patients with head and neck cancer: A meta-analysis

BACKGROUND

The correlation between vascular endothelial growth factor (VEGF) overexpression and the clinical outcome of head and neck cancer remains inconclusive. This meta-analysis aimed to evaluate the prognostic value of VEGF in patients with head and neck cancer.

METHODS

We searched Ovid MEDLINE, EMBASE and 2 Chinese science databases in order to enroll all eligible articles. Forty-seven studies were included in this meta-analysis. All results were evaluated by the random-effects model.

RESULTS

VEGF overexpression is significantly associated with worse overall survival (OS; hazard ratio [HR], 1.89; 95% confidence interval [CI], 1.61-2.22) and progression-free survival (PFS; HR, 1.68; 95% CI, 1.33-2.12). Subgroup analysis reveals that VEGF overexpression is a significant poor predictor for nasopharyngeal cancer (HR, 1.66; 95% CI, 1.30-2.12) and salivary gland cancer (HR, 3.32; 95% CI, 1.61-6.84).

CONCLUSION

Our meta-analysis supports that VEGF overexpression is an available poor predictor for patients with head and neck cancer.

Hypoxia promotes ligand-independent EGF receptor signaling via hypoxia-inducible factor-mediated upregulation of caveolin-1

Caveolin-1 (CAV1) is an essential structural constituent of caveolae, specialized lipid raft microdomains on the cell membrane involved in endocytosis and signal transduction, which are inexplicably deregulated and are associated with aggressiveness in numerous cancers. Here we identify CAV1 as a direct transcriptional target of oxygen-labile hypoxia-inducible factor 1 and 2 that accentuates the formation of caveolae, leading to increased dimerization of EGF receptor within the confined surface area of caveolae and its subsequent phosphorylation in the absence of ligand. Hypoxia-inducible factor-dependent up-regulation of CAV1 enhanced the oncogenic potential of tumor cells by increasing the cell proliferative, migratory, and invasive capacities. These results support a concept in which a crisis in oxygen availability or a tumor exhibiting hypoxic signature triggers caveolae formation that bypasses the requirement for ligand engagement to initiate receptor activation and the critical downstream adaptive signaling during a period when ligands required to activate these receptors are limited or are not yet available.

Regulation of Cell Signaling and Function by Endothelial Caveolins: Implications in Disease

Caveolae are cholesterol- and glycosphingolipid-rich omega-shaped invaginations of the plasma membrane that are very abundant in vascular endothelial cells and present in most cell types. Caveolins are the major coat protein components of caveolae. Multiple studies using knockout mouse, small interfering RNA, and cell-permeable peptide delivery approaches have significantly enhanced our understanding of the role of endothelial caveolae and caveolin-1 in physiology and disease. Several postnatal pulmonary and cardiovascular pathologies have been reported in caveolin-1 knockout mice, many of which have been recently rescued by selective re-expression of caveolin-1 in endothelium of these mice. A large body of experimental evidence mostly using caveolin-1 knockout mice suggests that, depending on the disease model, endothelial caveolin-1 may play either a protective or a detrimental role. For instance, physiological or higher expression levels of caveolin-1 in endothelium might be beneficial in such diseases as pulmonary hypertension, cardiac hypertrophy, or ischemic injury. On the other hand, endothelial caveolin-1 might contribute to acute lung injury and inflammation, atherosclerosis or pathological angiogenesis associated with inflammatory bowel disease. Moreover, depending on the specific model, endothelial caveolin-1 may either promote or suppress tumor-induced angiogenesis. In addition to overwhelming evidence for the role of endothelial caveolin-1, more recent studies also suggest that endothelial caveolin-2 could possibly play a role in pulmonary disease. The purpose of this review is to focus on how caveolin-1 expressed in endothelial cells regulates endothelial cell signaling and function. The review places particular emphasis on relevance to disease, including but not limited to Pulmonary and cardiovascular disorders as well as cancer. In addition to caveolin-1, possible importance of the less-studied endothelial caveolin-2 in pulmonary diseases will be also discussed.

Caveolin-1 and cancer metabolism in the tumor microenvironment: markers, models, and mechanisms

Caveolins are a family of membrane-bound scaffolding proteins that compartmentalize and negatively regulate signal transduction. Recent studies have implicated a loss of caveolin-1 (Cav-1) expression in the pathogenesis of human cancers. Loss of Cav-1 expression in cancer-associated fibroblasts results in an activated tumor microenvironment, thereby driving early tumor recurrence, metastasis, and poor clinical outcome in breast and prostate cancers. We describe various paracrine signaling mechanism(s) by which the loss of stromal Cav-1 promotes tumor progression, including fibrosis, extracellular matrix remodeling, and the metabolic/catabolic reprogramming of cancer-associated fibroblast, to fuel the growth of adjacent tumor cells. It appears that oxidative stress is the root cause of initiation of the loss of stromal Cav-1 via autophagy, which provides further impetus for the use of antioxidants in anticancer therapy. Finally, we discuss the functional role of Cav-1 in epithelial cancer cells.

Extracellular matrix metalloproteinase inducer expression in salivary gland tumors: a correlation with microvessel density

The purpose of this study was to investigate the expression pattern of extracellular matrix metalloproteinase inducer (EMMPRIN) as well as the correlation between EMMPRIN and microvessel density (MVD) in salivary gland tumors. Extracellular matrix metalloproteinase inducer expression and MVD were examined immunohistochemically on paraffin-embedded tissue specimens from 95 patients with salivary gland tumors, who underwent surgical resection from 1998 to 2006. Reverse transcription-polymerase chain reaction was used to monitor EMMPRIN mRNA expression in frozen samples. Extracellular matrix metalloproteinase inducer expression in mucoepidermoid carcinomas and adenoid cystic carcinomas was significantly higher than in normal salivary gland tissues and pleomorphic adenomas (P < 0.05). The MVD of mucoepidermoid carcinomas and adenoid cystic carcinomas was significantly higher compared with pleomorphic adenomas (P < 0.05). The MVD of the EMMPRIN-positive expression group was significantly higher than the MVD of the EMMPRIN-negative expression group (P < 0.05). Extracellular matrix metalloproteinase inducer mRNA expression in malignant salivary gland tumors was higher than that in pleomorphic adenomas (P < 0.05). This study suggests that EMMPRIN expression is an important feature of malignant salivary gland tumors and can be used as a biologic marker to characterize salivary gland tumors. Extracellular matrix metalloproteinase inducer is also a positive angiogenic factor in salivary gland tumors.

Correlation between ANGPTL3 expression and tumor angiogenesis in hepatocellular carcinoma

AIM: To investigate the correlation between the expression of angiopoietin-like protein 3 (ANGPTL3) and tumor angiogenesis in hepatocellular carcinoma (HCC).

METHODS: The expression of ANGPTL3 and VEGF proteins in 96 HCC specimens and matched tumor-adjacent specimens was detected by immunohistochemistry and Western blot. Immunohistochemical staining for CD34 was performed in the above specimens to evaluate microvessel density (MVD).

RESULTS: The positive rates of ANGPTL3 and VEGF expression in HCC were significantly higher than that in tumor-adjacent tissue (62.50% vs 32.29%; 81.25% vs 29.17%, both P < 0.05). Active angiogenesis was detected in HCC compared to tumor-adjacent tissue (67.71% vs 31.25%, P < 0.05). Tumor angiogenesis was related with ANGPTL3 expression in HCC. The expression of ANGPTL3 and VEGF protein was significantly up-regulated in HCC compared with matched tumor-adjacent noncancerous tissue.

CONCLUSION: High expression of ANGPTL3 is associated with tumor angiogenesis in HCC.

MMTV promoter-regulated caveolin-1 overexpression yields defective parenchymal epithelia in multiple exocrine organs of transgenic mice

Caveolin-1 (Cav-1) is a major structural protein of caveolae, specialized plasma membrane invaginations that are involved in a cell-specific fashion in diverse cell activities such as molecular transport, cell adhesion, and signal transduction. In normal adult mammals, Cav-1 expression is abundant in mesenchyme-derived cells but relatively low in epithelial parenchyma. However, epithelial Cav-1 overexpression is associated with development and/or progression of many carcinomas. In this study, we generated and characterized a transgenic mouse model of Cav-1 overexpression under the control of a mouse mammary tumor virus (MMTV) long terminal-repeat promoter, which is predominantly expressed in specific epithelial cells. The MMTVcav-1(+) transgenic mice were fertile, and females bore litters of normal size with no obvious developmental abnormalities. However, by age 11months, the MMTVcav-1(+) mice demonstrated overtly different phenotypes in multiple exocrine organs when compared with their nontransgenic MMTVcav-1(-) littermates. Cav-1 overexpression in MMTVcav-1(+) mice produced organ-specific abnormalities, including hypotrophy of mammary glandular epithelia, bronchiolar epithelial hyperplasia and atypia, mucous-cell hyperplasia in salivary glands, elongated hair follicles and dermal thickening in the skin, and reduced accumulation of enzymogen granules in pancreatic acinar cells. In addition, the MMTVcav-1(+) transgenic mice tended to have a greater incidence of malignant tumors, including lung and liver carcinomas and lymphoma, than their MMTVcav-1(-) littermates. Our results indicate that Cav-1 overexpression causes organ-specific, age-related epithelial disorders and suggest the potential for increased susceptibility to carcinogenesis.

Morphometric analysis of CD34-positive vessels in salivary gland adenoid cystic and mucoepidermoid carcinomas

BACKGROUND

Carcinomas of the salivary glands are uncommon and morphologically a diverse group of malignancies. To evaluate the prognostic value of CD34 immunostaining of the vessels in adenoid cystic carcinoma (AdCC) and mucoepidermoid carcinoma (MEC), an automated image analysis method was used.

METHOD

In a nationwide study, covering salivary gland cancer (SGC) patients in Finland 1991-1996, 37 AdCC and 18 MEC patients (M 25, F 30, age 25-90, mean 63) were included. In addition to clinical characteristics the size, shape, staining intensity and vessel density in CD34 immunostained histologic samples were measured.

RESULTS

Altogether 4433 vessels were measured from AdCC and 2615 from MEC tumor. Of the total tumor vessels measured, 2651 were from patients who deceased with disease (Group I) and 4397 were from specimens derived from those who did not die of disease (Group II) during the 10-year follow-up. The staining intensity was significantly higher in MEC than in AdCC tumor (P = 0.0005). In MEC, the Group I patients had a higher staining intensity among high-grade patients compared with patients with low grade disease, whereas the tumors in Group II had a lower staining intensity among the high-grade compared with the low grade tumors (P = 0.018). A higher vessel density was found in patients with MEC in group II compared with group I (P = 0.017).

CONCLUSIONS

The staining intensity of CD34 positive vessels in MEC was higher than in AdCC. In MEC, higher staining intensity of vessels in high-grade tumors and lower vessel density in all MEC patients, predicted poor survival.

Caveats of caveolin-1 in cancer progression

Caveolin-1, an essential scaffold protein of caveolae and cellular transport processes, lately gained recognition as a stage- and tissue-specific tumor modulator in vivo. Patient studies and rodent models corroborated its janus-faced role as a tumor suppressor in non-neoplastic tissue, its down-regulation (loss of function) upon transformation and its re-expression (regain of function) in advanced-stage metastatic and multidrug resistant tumors. This review is focussed on the role of caveolin-1 in metastasis and angiogenesis and its clinical implications as a prognostic marker in cancer progression.

Correlative evidence that tumor cell-derived caveolin-1 mediates angiogenesis in meningiomas

Since it has recently been reported that caveolin-1 (cav-1) may favor the progression of prostatic and renal cancers by stimulating tumor neoangiogenesis, we thought it of interest to analyze the correlation between cav-1 expression and tumor microvessel density (MVD) in meningiomas. In the present study we quantified cav-1 expression by immunohistochemistry and used CD105 immunohistochemical staining to measure MVD. Sixty-two formalin-fixed, paraffin-embedded, surgically resected meningiomas were submitted to the analysis. On the basis of cav-1 immuno-expression, cases were subdivided into meningiomas displaying a low (n = 34) and a high (n = 28) cav-1 immuno-expression, respectively. Mann-Whitney test showed that a significantly higher MVD was present in the cases with a high cav-1 expression than in those with a low expression (mean 24.44 vs. 41.28 microvessels/mm(2)) (P = 0.0001). Moreover, Spearman test revealed a significant positive correlation between cav-1 rate of expression and MVD counts in the meningiomas of our series (r = 0.390; P = 0.0023). Therefore, our study demonstrates the existence of an association between cav-1 expression and neoangiogenesis in meningiomas, suggesting that cav-1 may mediate the progression of these tumors by stimulating the angiogenic process. Besides, it is known that the progression of meningiomas is paralleled by an increase in MVD. The clarification of cav-1 role in the neoangiogensis of meningiomas may open new insights about the possibility of novel therapeutic strategies in these neoplasias.