Caveolin-1 regulating the invasion and expression of matrix metalloproteinase (MMPs) in pancreatic carcinoma cells

Caveolin-1: an ambiguous entity in breast cancer

Breast cancer (BC) is the most frequently diagnosed cancer in women and the second leading cause of death from cancer among women. Metastasis is the major cause of BC-associated mortality. Accumulating evidence implicates Caveolin-1 (Cav-1), a structural protein of plasma membrane caveolae, in BC metastasis. Cav-1 exhibits a dual role, as both a tumor suppressor and promoter depending on the cellular context and BC subtype. This review highlights the role of Cav-1 in modulating glycolytic metabolism, tumor-stromal interactions, apoptosis, and senescence. Additionally, stromal Cav-1's expression is identified as a potential prognostic marker, offering insights into its contrasting roles in tumor suppression and progression. Furthermore, Cav-1's context-dependent effects are explored in BC subtypes including hormone receptor-positive, HER2-positive, and triple-negative BC (TNBC). The review further delves into the role of Cav-1 in regulating the metastatic cascade including extracellular matrix interactions, cell migration and invasion, and premetastatic niche formation. The later sections discuss the therapeutic targeting of Cav-1 by metabolic inhibitors such as betulinic acid and Cav-1 modulating compounds. While Cav-1 may be a potential biomarker and therapeutic target, its heterogeneous expression and context-specific activity necessitates further research to develop precise interventions. Future studies investigating the mechanistic role of Cav-1 in metastasis may pave the way for effective treatment of metastatic BC.

Genetic Manipulation of Caveolin-1 in a Transgenic Mouse Model of Aortic Root Aneurysm: Sex-Dependent Effects on Endothelial and Smooth Muscle Function

Marfan syndrome (MFS) is a systemic connective tissue disorder stemming from mutations in the gene encoding Fibrillin-1 (Fbn1), a key extracellular matrix glycoprotein. This condition manifests with various clinical features, the most critical of which is the formation of aortic root aneurysms. Reduced nitric oxide (NO) production due to diminished endothelial nitric oxide synthase (eNOS) activity has been linked to MFS aortic aneurysm pathology. Caveolin-1 (Cav1), a structural protein of plasma membrane caveolae, is known to inhibit eNOS activity, suggesting its involvement in MFS aneurysm progression by modulating NO levels. In this study, we examined the role of Cav1 in aortic smooth muscle and endothelial function, aortic wall elasticity, and wall strength in male and female MFS mice (FBN1+/Cys1041Gly) by generating developing Cav1-deficient MFS mice (MFS/Cav1KO). Our findings reveal that Cav1 ablation leads to a pronounced reduction in aortic smooth muscle contraction in response to phenylephrine, attributable to an increase in NO production in the aortic wall. Furthermore, we observed enhanced aortic relaxation responses to acetylcholine in MFS/Cav1KO mice, further underscoring Cav1's inhibitory impact on NO synthesis within the aorta. Notably, van Gieson staining and chamber myography analyses showed improved elastin fiber structure and wall strength in male MFS/Cav1KO mice, whereas these effects were absent in female counterparts. Cav1's regulatory influence on aortic root aneurysm development in MFS through NO-mediated modulation of smooth muscle and endothelial function, with notable sex-dependent variations.

Is there any diagnostic value of serum caveolin-1 levels on the determination of pancreatic adenocarcinoma?

BACKGROUND

Caveolin-1 (CAV-1) is a vital component in cancer pathogenesis, as its expression determines the survival of patients with cancer. This study investigates CAV-1 serum levels in pancreatic adenocarcinoma (PA) patients and their role in tumor progression and prognostic factors.

METHOD

The trial included 33 patients with pathologically confirmed pancreatic cancer (PC). The enzyme-linked immunosorbent assay (ELISA) method was used to measure the concentrations of CAV-1 in the blood. The study also included 20 healthy subjects. The statistical analysis was two-sided, and a P value of ≤ 0.05 was determined as statistically significant.

RESULTS

The median age of the subjects was 59 years (32-84 years) at the time of diagnosis. There were 13 (39%) female participants. In 21 (63%) patients, the primary focus was the pancreatic head. In 23 stage IV patients, hepatic metastasis (n = 19, 83%) was observed. Only one patient (3%) was still alive at the end of the study period. Palliative chemotherapy (CTx) was provided, with 39% of the 23 patients responding to it. The overall survival (OS) rate in this cohort was 41.3 ± 8.3 weeks at a 95% confidence interval (CI), after 25-58 weeks. Serum baseline CAV-1 values among patients with PA were significantly higher compared with controls (p = 0.009). Patients with poor performance status, a pancreatic head tumor, lower albumin levels, higher serum carcinoembryonic antigen (CEA) levels, and higher CA 19.9 levels had significantly higher serum CAV-1 levels (p = 0.01, P = 0.05, P = 0.03, P = 0.02, and P = 0.04, respectively). However, CAV-1 did not show any prognostic value (p = 0.75).

CONCLUSION

Although serum CAV-1 is a useful diagnostic marker in PC patients, it is not a prognostic or predictive marker.

Drug Delivery Strategies for the Treatment of Pancreatic Cancer

Pancreatic cancer is fast becoming a global menace and it is projected to be the second leading cause of cancer-related death by 2030. Pancreatic adenocarcinomas, which develop in the pancreas' exocrine region, are the predominant type of pancreatic cancer, representing about 95% of total pancreatic tumors. The malignancy progresses asymptomatically, making early diagnosis difficult. It is characterized by excessive production of fibrotic stroma known as desmoplasia, which aids tumor growth and metastatic spread by remodeling the extracellular matrix and releasing tumor growth factors. For decades, immense efforts have been harnessed toward developing more effective drug delivery systems for pancreatic cancer treatment leveraging nanotechnology, immunotherapy, drug conjugates, and combinations of these approaches. However, despite the reported preclinical success of these approaches, no substantial progress has been made clinically and the prognosis for pancreatic cancer is worsening. This review provides insights into challenges associated with the delivery of therapeutics for pancreatic cancer treatment and discusses drug delivery strategies to minimize adverse effects associated with current chemotherapy options and to improve the efficiency of drug treatment.

Proteomics analysis of colon cancer progression

BACKGROUND

The aim of this pilot study was to identify proteins associated with advancement of colon cancer (CC).

METHODS

A quantitative proteomics approach was used to determine the global changes in the proteome of primary colon cancer from patients with non-cancer normal colon (NC), non-adenomatous colon polyp (NAP), non-metastatic tumor (CC NM) and metastatic tumor (CC M) tissues, to identify up- and down-regulated proteins. Total protein was extracted from each biopsy, trypsin-digested, iTRAQ-labeled and the resulting peptides separated using strong cation exchange (SCX) and reverse-phase (RP) chromatography on-line to electrospray ionization mass spectrometry (ESI-MS).

RESULTS

Database searching of the MS/MS data resulted in the identification of 2777 proteins which were clustered into groups associated with disease progression. Proteins which were changed in all disease stages including benign, and hence indicative of the earliest molecular perturbations, were strongly associated with spliceosomal activity, cell cycle division, and stromal and cytoskeleton disruption reflecting increased proliferation and expansion into the surrounding healthy tissue. Those proteins changed in cancer stages but not in benign, were linked to inflammation/immune response, loss of cell adhesion, mitochondrial function and autophagy, demonstrating early evidence of cells within the nutrient-poor solid mass either undergoing cell death or adjusting for survival. Caveolin-1, which decreased and Matrix metalloproteinase-9, which increased through the three disease stages compared to normal tissue, was selected to validate the proteomics results, but significant patient-to-patient variation obfuscated interpretation so corroborated the contradictory observations made by others.

CONCLUSION

Nevertheless, the study has provided significant insights into CC stage progression for further investigation.

Proteomics analysis of colon cancer progression

BACKGROUND

The aim of this pilot study was to identify proteins associated with advancement of colon cancer (CC).

METHODS

A quantitative proteomics approach was used to determine the global changes in the proteome of primary colon cancer from patients with non-cancer normal colon (NC), non-adenomatous colon polyp (NAP), non-metastatic tumor (CC NM) and metastatic tumor (CC M) tissues, to identify up- and down-regulated proteins. Total protein was extracted from each biopsy, trypsin-digested, iTRAQ-labeled and the resulting peptides separated using strong cation exchange (SCX) and reverse-phase (RP) chromatography on-line to electrospray ionization mass spectrometry (ESI-MS).

RESULTS

Database searching of the MS/MS data resulted in the identification of 2777 proteins which were clustered into groups associated with disease progression. Proteins which were changed in all disease stages including benign, and hence indicative of the earliest molecular perturbations, were strongly associated with spliceosomal activity, cell cycle division, and stromal and cytoskeleton disruption reflecting increased proliferation and expansion into the surrounding healthy tissue. Those proteins changed in cancer stages but not in benign, were linked to inflammation/immune response, loss of cell adhesion, mitochondrial function and autophagy, demonstrating early evidence of cells within the nutrient-poor solid mass either undergoing cell death or adjusting for survival. Caveolin-1, which decreased and Matrix metalloproteinase-9, which increased through the three disease stages compared to normal tissue, was selected to validate the proteomics results, but significant patient-to-patient variation obfuscated interpretation so corroborated the contradictory observations made by others.

CONCLUSION

Nevertheless, the study has provided significant insights into CC stage progression for further investigation.

GSTΠ stimulates caveolin-1-regulated polyamine uptake via actin remodeling

Polyamines spermidine and spermine, and their diamine precursor putrescine, are essential for normal cellular functions in both pro- and eukaryotes. Cellular polyamine levels are regulated by biosynthesis, degradation and transport. Transport of dietary and luminal bacterial polyamines in gastrointestinal (GI) tissues plays a significant role in tissue polyamine homeostasis. We have reported that caveolin-1 play an inhibitory role in polyamine uptake in GI tissues. We investigated the mechanism of caveolin-1-regulated polyamine transport. We found that glutathione S-transferase Π(GSTΠ) was secreted from caveolin-1 knockdown cells and stimulated spermidine transport in human colon-derived HCT116 cells. GSTΠ secreted in the medium increased S-glutathionylated protein level in the plasma membrane fraction. Proteomic analysis revealed that actin was S-glutathionylated by GSTΠ. Immunofluorescence microscopy demonstrated that actin filaments around plasma membrane were S-glutathionylated in caveolin-1 knockdown cells. Inhibition of actin remodeling by jasplakinolide caused a decrease in polyamine uptake activity. These data support a model in which caveolin-1 negatively regulates polyamine uptake by inhibiting GSTΠ secretion, which stimulates actin remodeling and endocytosis.

Deletion of caveolin scaffolding domain alters cancer cell migration

Caveolin-1 (Cav-1) is an integral membrane protein that plays an important role in proliferative and terminally differentiated cells. As a structural component of Caveolae, Cav-1 interacts with signaling molecules via a caveolin scaffolding domain (CSD) regulating cell signaling. Recent reports have shown that Cav-1 is a negative regulator in tumor metastasis. Therefore, we hypothesize that Cav-1 inhibits cell migration through its CSD. HeLa cells were engineered to overexpress Cav-1 (Cav-1 OE), Cav-1 without a functional CSD (∆CSD), or enhanced green fluorescent protein (EGFP) as a control. HeLa cell migration was suppressed in Cav-1 OE cells while ∆CSD showed increased migration, which corresponded to a decrease in the tight junction protein, zonula occludens (ZO-1). The migration phenotype was confirmed in multiple cancer cell lines. Phosphorylated STAT-3 was decreased in Cav-1 OE cells compared to control and ∆CSD cells; reducing STAT-3 expression alone decreased cell migration. ∆CSD blunted HeLa proliferation by increasing the number of cells in the G2/M phase of the cell cycle. Overexpressing the CSD peptide alone suppressed HeLa cell migration and inhibited pSTAT3. These findings suggest that Cav-1 CSD may be critical in controlling the dynamic phenotype of cancer cells by facilitating the interaction of specific signal transduction pathways, regulating STAT3 and participating in a G2/M checkpoint. Modulating the CSD and targeting specific proteins may offer potential new therapies in the treatment of cancer metastasis.

Correlation of the invasive potential of glioblastoma and expression of caveola-forming proteins caveolin-1 and CAVIN1

INTRODUCTION

Glioblastoma (GBM) is the most common primary brain cancer. The average survival time for the majority of patients is approximately 15 months after diagnosis. A major feature of GBM that contributes to its poor prognosis is its high invasiveness. Caveolae are plasma membrane subdomains that participate in numerous biological functions. Caveolin-1 and Caveolae Associated Protein 1 (CAVIN1), formerly termed Polymerase I and Transcript Release Factor, are both necessary for caveola formation. We hypothesized that high expression of caveola-forming proteins in GBM promotes invasiveness via modulation of the production of matrix-degrading enzymes.

METHODS

The mRNA expression of caveola-forming proteins and matrix proteases in GBM samples, and survival after stratifying patients according to caveolin-1 or CAVIN1 expression, were analyzed from TCGA and REMBRANDT databases. The proteolytic profile of cell lines expressing or devoid of caveola-forming proteins was investigated using zymography and real-time qPCR. Invasion through basement membrane-like protein was investigated in vitro.

RESULTS

Expression of both caveolin-1 and CAVIN1 was increased in GBM compared to normal samples and correlated with expression of urokinase plasminogen activator (uPA) and gelatinases. High expression of caveola-forming proteins was associated with shorter survival time. GBM cell lines capable of forming caveolae expressed more uPA and matrix metalloproteinase-2 (MMP-2) and/or -9 (MMP-9) and were more invasive than GBM cells devoid of caveola-forming proteins. Experimental manipulation of caveolin-1 or CAVIN1 expression in GBM cells recapitulated some, but not all of these features. Caveolae modulate GBM cell invasion in part via matrix protease expression.

Caveolin-1 as a pathophysiological factor and target in psoriasis

Low expression of caveolin-1 (Cav-1) is typical in psoriatic lesions and overexpression of Cav-1 leads to a reduction of inflammation and suppression of epidermal hyperproliferation, thus ameliorating these two well-known hallmarks of psoriasis. At the same time, the interfacial layers of the white adipose tissue (WAT) adjacent to psoriatic lesions demonstrate much higher stiffness, which also points to a modification of Cav-1 expression in this tissue. These processes are connected with each other and regulated via exosomal exchange. Here we discuss the role of Cav-1 expression in inflammatory and hyperproliferative processes and analyze the ways to provide spatially different modulation of Cav-1 expression in the skin and WAT. Such modulation can be induced by different pharmacological and physical factors. These include application of mechanical stress and supra-physiological temperatures. Cav-1 should therefore be considered as an important target in treatment of psoriasis.

Silencing of caveolin-1 in fibroblasts as opposed to epithelial tumor cells results in increased tumor growth rate and chemoresistance in a human pancreatic cancer model

Caveolin-1 (Cav-1) expression has been shown to be associated with tumor growth and resistance to chemotherapy in pancreatic cancer. The primary aim of this study was to explore the significance of Cav-1 expression in pancreatic cancer cells as compared to fibroblasts in relation to cancer cell proliferation and chemoresistance, both in vitro and in vivo, in an immunodeficient mouse model. We also aimed to evaluate the immunohistochemical expression of Cav-1 in the epithelial and stromal component of pancreatic cancer tissue specimens. The immunohistochemical staining of poorly differentiated tissue sections revealed a strong and weak Cav-1 expression in the epithelial tumor cells and stromal fibroblasts, respectively. Conversely, the well-differentiated areas were characterized by a weak epithelial Cav-1 expression. Cav-1 downregulation in cancer cells resulted in an increased proliferation in vitro; however, it had no effect on chemoresistance and growth gain in vivo. By contrast, the decreased expression of Cav-1 in fibroblasts resulted in a growth advantage and the chemo-resistance of cancer cells when they were co-injected into immunodeficient mice to develop mixed fibroblast/cancer cell xenografts. On the whole, the findings of this study suggest that the downregulation of Cav-1 in fibroblasts is associated with an increased tumor proliferation rate in vivo and chemoresistance. Further studies are warranted to explore whether the targeting of Cav-1 in the stroma may represent a novel therapeutic approach in pancreatic cancer.

Caveolin-1 deficiency protects pancreatic β cells against palmitate-induced dysfunction and apoptosis

Lipotoxicity leads to insulin secretion deficiency, which is among the important causes for the onset of type 2 diabetes mellitus. Thus, the restoration of β-cell mass and preservation of its endocrine function are long-sought goals in diabetes research. Previous studies have suggested that the membrane protein caveolin-1 (Cav-1) is implicated in β-cell apoptosis and insulin secretion, however, the underlying mechanisms still remains unclear. Our objective is to explore whether Cav-1 depletion protects pancreatic β cells from lipotoxicity and what are the underlying mechanisms. In this study, we found that Cav-1 silencing significantly promoted β-cell proliferation, inhibited palmitate (PA)-induced pancreatic β-cell apoptosis and enhanced insulin production and secretion. These effects were associated with enhanced activities of Akt and ERK1/2, which in turn downregulated the expression of cell cycle inhibitors (FOXO1, GSK3β, P21, P27 and P53) and upregulated the expression of Cyclin D2 and Cyclin D3. Subsequent inhibition of PI3K/Akt and ERK/MAPK pathways abolished Cav-1 depletion induced β-cell mass protection. Furthermore, under PA induced endoplasmic reticulum (ER) stress, Cav-1 silencing significantly reduced eIF2α phosphorylation and the expression of ER stress-responsive markers BiP and CHOP, which are among the known sensitizers of lipotoxicity. Our findings suggest Cav-1 as potential target molecule in T2DM treatment via the preservation of lipotoxicity-induced β-cell mass reduction and the attenuation of insulin secretion dysfunction.

The overexpression and predictive significance of MMP-12 in esophageal squamous cell carcinoma

Matrix metalloproteinase (MMP)-mediated degradation of the extracellular matrix is a major factor for tumor invasion and metastasis. MMP-12, as metalloelastase, its function in tumor progression remains contradictory. This study was undertaken to investigate the role of MMP-12 in esophageal squamous cell carcinoma (ESCC). We analyzed the protein expression of MMP-12 and its association with clinicopatholigical parameters, as well as survival analysis. MMP-12 was highly expressed in tumor cells comparing with normal epithelial cells. The high expression of MMP-12 was significantly correlated with tumor grade and stage, nodal metastasis and poor survival of ESCC. Cox multivariate analysis revealed that MMP-12 was an independent prognostic factor in ESCC. Our results suggest that MMP-12 might act as a potential target for the development of novel therapeutics of esophageal squamous cell carcinoma.

Caveolin-1: An Oxidative Stress-Related Target for Cancer Prevention

Aberrant oxidative metabolism is one of the hallmarks of cancer. Reactive species overproduction could promote carcinogenesis via inducing genetic mutations and activating oncogenic pathways, and thus, antioxidant therapy was considered as an important strategy for cancer prevention and treatment. Caveolin-1 (Cav-1), a constituent protein of caveolae, has been shown to mediate tumorigenesis and progression through oxidative stress modulation recently. Reactive species could modulate the expression, degradation, posttranslational modifications, and membrane trafficking of Cav-1, while Cav-1-targeted treatments could scavenge the reactive species. More importantly, emerging evidences have indicated that multiple antioxidants could exert antitumor activities in cancer cells and protective activities in normal cells by modulating the Cav-1 pathway. Altogether, these findings indicate that Cav-1 may be a promising oxidative stress-related target for cancer antioxidant prevention. Elucidating the underlying interaction mechanisms between oxidative stress and Cav-1 is helpful for enhancing the preventive effects of antioxidants on cancer, for improving clinical outcomes of antioxidant-related therapeutics in cancer patients, and for developing Cav-1 targeted drugs. Herein, we summarize the available evidence of the roles of Cav-1 and oxidative stress in tumorigenesis and development and shed novel light on designing strategies for cancer prevention or treatment by utilizing the interaction mode between Cav-1 and oxidative stress.

The different functions and clinical significances of caveolin-1 in human adenocarcinoma and squamous cell carcinoma

Caveolin-1 (Cav-1), a major structural protein of caveolae, is an integral membrane protein which plays an important role in the progression of carcinoma. However, whether Cav-1 acts as a tumor promoter or a tumor suppressor still remains controversial. For example, the tumor-promoting function of Cav-1 has been found in renal cancer, prostate cancer, tongue squamous cell carcinoma (SCC), lung SCC and bladder SCC. In contrast, Cav-1 also plays an inhibitory role in esophagus adenocarcinoma, lung adenocarcinoma and cutaneous SCC. The role of Cav-1 is still controversial in thyroid cancer, hepatocellular carcinoma, gastric adenocarcinoma, colon adenocarcinoma, breast cancer, pancreas cancer, oral SCC, laryngeal SCC, head and neck SCC, esophageal SCC and cervical SCC. Besides, it has been reported that the loss of stromal Cav-1 might predict poor prognosis in breast cancer, gastric cancer, pancreas cancer, prostate cancer, oral SCC and esophageal SCC. However, the accumulation of stromal Cav-1 has been found to be promoted by the progression of tongue SCC. Taken together, Cav-1 seems playing a different role in different cancer subtypes even of the same organ, as well as acting differently in the same cancer subtype of different organs. Thus, we hereby explore the functions of Cav-1 in human adenocarcinoma and SCC from the perspective of clinical significances and pathogenesis. We envision that novel targets may come with the further investigation of Cav-1 in carcinogenesis.

Overexpression of caveolin-1 attenuates brain edema by inhibiting tight junction degradation

Cerebral edema from the disruption of the blood-brain barrier (BBB) after cerebral ischemia is a major cause of morbidity and mortality as well as a common event in patients with stroke. Caveolins (Cavs) are thought to regulate BBB functions. Here, we report for the first time that Cav-1 overexpression (OE) decreased brain edema from BBB disruption following ischemic insult. Edema volumes and Cav-1 expression levels were measured following photothrombosis and middle cerebral artery occlusion (MCAO). Endothelial cells that were transduced with a Cav-1 lentiviral expression vector were transplanted into rats. BBB permeability was quantified with Evans blue extravasation. Edema volume was determined from measures of the extravasation area, brain water content, and average fluorescence intensity after Cy5.5 injections. Tight junction (TJ) protein expression was measured with immunoblotting. Cav-1 expression levels and vasogenic brain edema correlated strongly after ischemic insult. Cav-1 expression and BBB disruption peaked 3 d after the MCAO. In addition, intravenous administration of endothelial cells expressing Cav-1 effectively increased the Cav-1 levels 3 d after the MCAO ischemic insult. Importantly, Cav-1 OE ameliorated the vasogenic edema by inhibiting the degradation of TJ protein expression in the acute phase of ischemic stroke. These results suggested that Cav-1 OE protected the integrity of the BBB mainly by preventing the degradation of TJ proteins in rats. These findings need to be confirmed in a clinical setting in human subjects.

Regulation of Caveolin-1 Expression Determines Early Brain Edema After Experimental Focal Cerebral Ischemia

Background and Purpose—

Most patients with cerebral infarction die of brain edema because of the breakdown of the blood–brain barrier (BBB) in ischemic tissue. Caveolins (a group of proteins) are key modulators of vascular permeability; however, a direct role of caveolin-1 (Cav-1) in the regulation of BBB permeability during ischemic injury has yet to be identified.

Methods—

Cav-1 expression was measured by immunoblotting after photothrombotic ischemia. A direct functional role of Cav-1 in cerebral edema and BBB permeability during cerebral ischemia was investigated by genetic manipulation (gene disruption and re-expression) of Cav-1 protein expression in mice.

Results—

There was a significant correlation between the extent of BBB disruption and the Cav-1 expression. In Cav-1–deficient (Cav-1 −/− ) mice, the extent of BBB disruption after cerebral ischemia was increased compared with wild-type (Cav-1 +/+ ) mice, whereas the increase in cerebral edema volume was ameliorated by lentiviral-mediated re-expression of Cav-1. Furthermore, Cav-1 −/− mice had significantly higher degradation of tight junction proteins and proteolytic activity of matrix metalloproteinase than Cav-1 +/+ mice. Conversely, re-expression of Cav-1 in Cav-1 −/− mice restored tight junction protein expression and reduced matrix metalloproteinase proteolytic activity.

Conclusions—

These results indicate that Cav-1 is a critical determinant of BBB permeability. Strategies for regulating Cav-1 represent a novel therapeutic approach to controlling BBB disruption and subsequent neurological deterioration during cerebral ischemia.

Release of Matrix Metalloproteinases-2 and 9 by S-Nitrosylated Caveolin-1 Contributes to Degradation of Extracellular Matrix in tPA-Treated Hypoxic Endothelial Cells

Intracranial hemorrhage remains the most feared complication in tissue plasminogen activator (tPA) thrombolysis for ischemic stroke. However, the underlying molecular mechanisms are still poorly elucidated. In this study, we reported an important role of caveolin-1 (Cav-1) s-nitrosylation in matrix metalloproteinase (MMP)-2 and 9 secretion from tPA-treated ischemic endothelial cells. Brain vascular endothelial cells (bEND3) were exposed to oxygen-glucose deprivation (OGD) for 2 h before adding recombinant human tPA for 6 h. This treatment induced a significant increase of MMP2 and 9 in the media of bEND3 cells and a simultaneous degradation of fibronectin and laminin β-1, the two main components of extracellular matrix (ECM). Inhibition of MMP2 and 9 with SB-3CT completely blocked the degradation of fibronectin and laminin β-1. ODG+tPA treatment led to Cav-1 shedding from bEND3 cells into the media. Notably, OGD triggered nitric oxide (NO) production and S-nitrosylationof Cav-1 (SNCav-1). Meanwhile tPA induced activation of ERK signal pathway and stimulates the secretion of SNCav-1. Pretreatment of bEND3 cells with C-PTIO (a NO scavenger) or U0126 (a specific ERK inhibitor) significantly reduced OGD-induced S-nitrosylation of Cav-1 in cells and blocked the secretion of Cav-1 and MMP2 and 9 into the media as well as the degradation of fibronectin and laminin β-1 in OGD and tPA-treated cells. These data indicate that OGD-triggered Cav-1 S-nitrosylation interacts with tPA-induced ERK activation to augment MMP2 and 9 secretion and subsequent ECM degradation, which may account for the exacerbation of ischemic blood brain barrier damage following tPA thrombolysis for ischemic stroke.

Effects of ethanol on the expression of caveolin-1 in HepG2 cells

This study aimed to investigate the effects of ethanol on the expression of caveolin‑1 (CAV‑1) in HepG2 hepatocarcinoma cells. Ethanol‑treated HepG2 cells were investigated using the in vitro model to determine whether ethanol can influence the expression of CAV‑1. Cell viability was measured using the colorimetric 3‑(4, 5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Expression of CAV‑1 was detected using western blot analysis. Quantitative PCR (qPCR) was used to determine CAV‑1 mRNA levels. The distribution of CAV‑1 in HepG2 cells was analyzed using immunofluorescence. The MTT assay results revealed that cell viability was not altered at ethanol concentrations of <1.0%, while ethanol concentrations >1.0% caused cell shedding, but not cell fragmentation. Western blot analysis showed significant differences in the levels of CAV‑1 expression between the control group and the 1.0% ethanol‑treated group at 6, 12 and 24 h (all P<0.05). qPCR showed significant differences in the expression levels of caveolin‑1 mRNA between the control group and the 1.0% ethanol‑treated group at 6 h, 12 h and 24 h (all P<0.05). Immunofluorescence demonstrated that CAV‑1 was distributed discontinuously at the boundaries of HepG2 cells. The results indicate that ethanol may increase the expression of CAV‑1 in HepG2 cells.

Caveolae: molecular insights and therapeutic targets for stroke

INTRODUCTION

Caveolae are specialized plasma membrane micro-invaginations of most mammalian cell types. The organization and function of caveolae are carried out by their coat proteins, caveolins and adaptor proteins, cavins. Caveolae/caveolins physically interact with membrane-associated signaling molecules and function in cholesterol incorporation, signaling transduction and macromolecular transport/permeability.

AREAS COVERED

Recent investigations have implicated a check-and-balance role of caveolae in the pathophysiology of cerebral ischemia. Caveolin knockout mice displayed exacerbated ischemic injury, whereas caveolin peptide exerted remarkable protection against ischemia/reperfusion injury. This review attempts to provide a comprehensive synopsis of how caveolae/caveolins modulate blood-brain barrier permeability, pro-survival signaling, angiogenesis and neuroinflammation, and how this may contribute to a better understanding of the participation of caveolae in ischemic cascade. The role of caveolin in the preconditioning-induced tolerance against ischemia is also discussed.

EXPERT OPINION

Caveolae represent a novel target for cerebral ischemia. It remains open how to manipulate caveolin expression in a practical way to recapitulate the beneficial therapeutic outcomes. Caveolin peptides and associated antagomirs may be efficacious and deserve further investigations for their potential benefits for stroke.

High Serum MiR-130a Levels Are Associated with Severe Perihematomal Edema and Predict Adverse Outcome in Acute ICH

The development and/or progression of perihematomal edema (PHE) in patients with acute spontaneous intracerebral hemorrhage (ICH) vary substantially with different individuals. Although hematoma volume is a useful indicator for predicting PHE, its predictive power was not good at the early stage of ICH. Better predictors are urgently needed. In this study, we found that miR-130a was elevated in the serum of ICH patients and was an independent indicator positively associated with PHE volume within the first 3 days after onset. The R (2) was further evaluated when it is used in combination with hematoma mass. Serum miR-130a levels were associated with clinical outcome (National Institute of Health Stroke Scale (NIHSS) scores at day 14 and modified Rankin Scale (mRS) scores at day 90) only in patients with deep hematoma. Moreover, miR-130a was significantly increased in rat serum and perihematomal tissues and was in line with the change in brain edema. MiR-130a inhibitors reduced brain edema, blood-brain barrier (BBB) permeability, and increased neurological deficit scores, and miR-130a mimics increased monolayer permeability. Thrombin-stimulated brain microvascular endothelial cells (BMECs) were a main source of miR-130a under ICH. In the experimental model, the elevated miR-130a level was accompanied by the decreased caveolin-1 and increased matrix metalloproleinase (MMP)-2/9. Meanwhile, caveolin-1 (cav-1) was reduced by miR-130a mimics, accompanied by an increase in MMP-2/9 expression. The upregulated MMP-2/9 was then downregulated by cavtratin, a cav-1 scaffolding domain peptide. This regulation mechanism was authenticated in a thrombin-induced cellular ICH model. Our results suggest that serum miR-130a may serve as a useful early biomarker for monitoring post-ICH PHE and predicting prognosis and may be helpful in the decision-making of individualized therapy.

CRKL protein overexpression enhances cell proliferation and invasion in pancreatic cancer

CRKL is an adapter protein which is overexpressed in many malignant tumors and plays crucial roles in tumor progression. However, expression pattern and biological roles of CRKL in pancreatic cancer have not been examined. In the present study, we found that CRKL expression in pancreatic cancer specimens was higher than that in normal pancreatic tissues. Colony formation assay and Matrigel invasion assay showed that the overexpression of CRKL in Bxpc3 and Capan2 cell lines with low endogenous expression increased cell proliferation and invasion. Flow cytometry showed that CRKL promoted cell proliferation by facilitating cell cycle. Further analysis of cell cycle- and invasion-related molecules showed that CRKL upregulated cyclin D1, cyclin A, matrix metalloproteinase 2 (MMP2) expression, and phosphorylated extracellular signal (ERK)-regulated kinase. In conclusion, our study demonstrated that CRKL was overexpressed in human pancreatic cancers and contributed to pancreatic cancer cell proliferation and invasion through ERK signaling.

CAV1 promotes HCC cell progression and metastasis through Wnt/β-catenin pathway

Caveolin-1 (CAV1) has significant roles in many primary tumors and metastasis, despite the fact that malignant cells from different cancer types have different profiles of CAV1 expression. There is little information concerning CAV1 expression and role in hepatocellular carcinoma (HCC) progresion and metastasis. The role of CAV1 in HCC progression was explored in this study. We reported that CAV1 was overexpressed in highly invasive HCC cell lines compared with poorly invasive ones. The immunohistochemical staining was obviously stronger in metastatic HCC samples than in the non-metastatic specimens via tissue microarrays. Furthermore, CAV1 overexpression enhanced HCC cell invasiveness in vitro, and promoted tumorigenicity and lung metastasis in vivo. By contrast, CAV1 stable knockdown markedly reduced these malignant behaviors. Importantly, we found that CAV1 could induce EMT process through Wnt/β-catenin pathway to promote HCC metastasis. We also identify MMP-7 as a novel downstream target of CAV1. We have determined that CAV1 acts as a mediator between hyperactive ERK1/2 signaling and regulation of MMP-7 transcription. Together, these studies mechanistically show a previously unrecognized interplay between CAV1, EMT, ERK1/2 and MMP-7 that is likely significant in the progression of HCC toward metastasis.

Nitric oxide-matrix metaloproteinase-9 interactions: biological and pharmacological significance--NO and MMP-9 interactions

Nitric oxide (NO) and matrix metalloproteinase 9 (MMP-9) levels are found to increase in inflammation states and in cancer, and their levels may be reciprocally modulated. Understanding interactions between NO and MMP-9 is of biological and pharmacological relevance and may prove crucial in designing new therapeutics. The reciprocal interaction between NO and MMP-9 have been studied for nearly twenty years but to our knowledge, are yet to be the subject of a review. This review provides a summary of published data regarding the complex and sometimes contradictory effects of NO on MMP-9. We also analyse molecular mechanisms modulating and mediating NO-MMP-9 interactions. Finally, a potential therapeutic relevance of these interactions is presented.

Single domain antibody against carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) inhibits proliferation, migration, invasion and angiogenesis of pancreatic cancer cells

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is over-expressed in pancreatic cancer cells, and it is associated with the progression of pancreatic cancer. We tested a single domain antibody (sdAb) targeting CEACAM6, 2A3, which was isolated previously from a llama immune library, and an Fc conjugated version of this sdAb, to determine how they affect the pancreatic cancer cell line BxPC3. We also compared the effects of the antibodies to gemcitabine. Gemcitabine and 2A3 slowed down cancer cell proliferation. However, only 2A3 retarded cancer cell invasion, angiogenesis within the cancer mass and BxPC3 cell MMP-9 activity, three features important for tumour growth and metastasis. The IC50s for 2A3, 2A3-Fc and gemcitabine were determined as 6.5μM, 8μM and 12nM, respectively. While the 2A3 antibody inhibited MMP-9 activity by 33% compared to non-treated control cells, gemcitabine failed to inhibit MMP-9 activity. Moreover, 2A3 and 2A3-Fc inhibited invasion of BxPC3 by 73% compared to non-treated cells. When conditioned media that were produced using 2A3- or 2A3-Fc-treated BxPC3 cells were used in a capillary formation assay, the capillary length was reduced by 21% and 49%, respectively. Therefore 2A3 is an ideal candidate for treating tumours that over-express CEACAM6.

Caveolin-1 is a negative regulator of tumor growth in glioblastoma and modulates chemosensitivity to temozolomide

Caveolin-1 (Cav-1) is a critical regulator of tumor progression in a variety of cancers where it has been shown to act as either a tumor suppressor or tumor promoter. In glioblastoma multiforme, it has been previously demonstrated to function as a putative tumor suppressor. Our studies here, using the human glioblastoma-derived cell line U-87MG, further support the role of Cav-1 as a negative regulator of tumor growth. Using a lentiviral transduction approach, we were able to stably overexpress Cav-1 in U-87MG cells. Gene expression microarray analyses demonstrated significant enrichment in gene signatures corresponding to downregulation of MAPK, PI3K/AKT and mTOR signaling, as well as activation of apoptotic pathways in Cav-1-overexpressing U-87MG cells. These same gene signatures were later confirmed at the protein level in vitro. To explore the ability of Cav-1 to regulate tumor growth in vivo, we further show that Cav-1-overexpressing U-87MG cells display reduced tumorigenicity in an ectopic xenograft mouse model, with marked hypoactivation of MAPK and PI3K/mTOR pathways. Finally, we demonstrate that Cav-1 overexpression confers sensitivity to the most commonly used chemotherapy for glioblastoma, temozolomide. In conclusion, Cav-1 negatively regulates key cell growth and survival pathways and may be an effective biomarker for predicting response to chemotherapy in glioblastoma.

Caveolin-1 as a promoter of tumour spreading: when, how, where and why

Caveolae are non-clathrin invaginations of the plasma membrane in most cell types; they are involved in signalling functions and molecule trafficking, thus modulating several biological functions, including cell growth, apoptosis and angiogenesis. The major structural protein in caveolae is caveolin-1, which is known to act as a key regulator in cancer onset and progression through its role as a tumour suppressor. Caveolin-1 can also promote cell proliferation, survival and metastasis as well as chemo- and radioresistance. Here, we discuss recent findings and novel concepts that support a role for caveolin-1 in cancer development and its distant spreading. We also address the potential application of caveolin-1 in tumour therapy and diagnosis.

Significance of caveolin-1 regulators in pancreatic cancer

Caveolin-1 is a scaffold protein on the cell membrane. As the main component of caveolae, caveolin-1 is involved in many biological processes that include substance uptake and transmembrane signaling. Many of these processes and thus caveolin-1 contribute to cell transformation, tumorigenesis, and metastasis. Of particular interest are the dual rolesof tumor suppressor and oncogene that caveolin-1 appear to play in different malignancies, including pancreatic cancer. Therefore, analyzing caveolin-1 regulators and understanding their mechanisms of actionis key to identifying novel diagnostic and therapeutic tools for pancreatic cancer. This review details the mechanisms of action of caveolin-1 regulators and the potential significance for pancreatic cancer treatment.

In vitro anti-angiogenesis effects and active constituents of the saponin fraction from Gleditsia sinensis

BACKGROUND

The anomalous fruits of Gleditsia sinensis Lam. (Leguminosae), a crude drug in China, have long been used in traditional Chinese medicine for the treatment of various diseases. The saponin fraction isolated from the fruits (SFGS) is considered as the active component for the antitumor activity of this crude drug.

OBJECTIVES

The present study was performed to investigate the anti-angiogenesis activities and active constituents of SFGS.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with SFGS in the presence or absence of basic fibroblast growth factor (bFGF) in vitro. The proliferation, migration, and tube formation were studied by MTT, Transwell, and 2D Matrigel assays, respectively. The cell cycle and apoptosis were analyzed by flow cytometry. Enzyme-linked immunosorbent assay for protein expression of vascular endothelial growth factor (VEGF) and western blot analysis for caspase-3, caspase-8, and caspase-9 as well as Fas were performed. In addition, the effects of 13 saponin compounds isolated from SFGS on the tube formation of HUVECs were screened, and the structure-activity relationships were discussed.

RESULTS

SFGS, at concentrations (1, 3, and 10 µg/mL) without significant cytotoxicity on endothelial cells, significantly inhibited the proliferation, migration, and tube formation of HUVECs induced by bFGF (10 ng/mL). It moderately arrested the cell cycle to G1 phase but greatly induced cell apoptosis and increased the expressions of caspases-3, caspase-8, and Fas but not caspase-9 in HUVECs. Moreover, SFGS did not affect the bFGF-induced autosecretion of VEGF from endothelial cells. Among the 13 saponin compounds tested, gleditsiosides B, I, J, O, and Q showed inhibition of the tube formation at a concentration of 3 µM, and only gleditsioside B exerted significant inhibition at 1 µM.

CONCLUSION

SFGS is substantially able to prevent angiogenesis by interfering with multiple steps. The findings provide a new explanation for the antitumor effects of G sinensis fruits. Gleditsiosides B, I, J, O, and Q are probably the main active constituents of SFGS.

A novel FoxM1-caveolin signaling pathway promotes pancreatic cancer invasion and metastasis

Caveolin-1 (Cav-1), a principal structural component of caveolar membrane domains, contributes to cancer development but its precise functional roles and regulation remain unclear. In this study, we determined the oncogenic function of Cav-1 in preclinical models of pancreatic cancer and in human tissue specimens. Cav-1 expression levels correlated with metastatic potential and epithelial-mesenchymal transition (EMT) in both mouse and human pancreatic cancer cells. Elevated levels in cells promoted EMT, migration, invasion, and metastasis in animal models, whereas RNA interference (RNAi)-mediated knockdown inhibited these processes. We determined that levels of Cav-1 and the Forkhead transcription factor FoxM1 correlated directly in pancreatic cancer cells and tumor tissues. Enforced expression of FoxM1 increased Cav-1 levels, whereas RNAi-mediated knockdown of FoxM1 had the opposite effect. FoxM1 directly bound to the promoter region of Cav-1 gene and positively transactivated its activity. Collectively, our findings defined Cav-1 as an important downstream oncogenic target of FoxM1, suggesting that dysregulated signaling of this novel FoxM1-Cav-1 pathway promotes pancreatic cancer development and progression.

Caveolin-1 in sarcomas: friend or foe?

Sarcomas represent a heterogeneous group of tumors with a complex and difficult reproducible classification. Their pathogenesis is poorly understood and there are few effective treatment options for advanced disease. Caveolin-1 is a multifunctional scaffolding protein with multiple binding partners that regulates multiple cancer-associated processes including cellular transformation, tumor growth, cell death and survival, multidrug resistance, angiogenesis, cell migration and metastasis. However, ambiguous roles have been ascribed to caveolin-1 in signal transduction and cancer, including sarcomas. In particular, evidence indicating that caveolin-1 function is cell context dependent has been repeatedly reported. Caveolin-1 appears to act as a tumor suppressor protein at early stages of cancer progression. In contrast, a growing body of evidence indicates that caveolin-1 is up-regulated in several multidrug-resistant and metastatic cancer cell lines and human tumor specimens. This review is focused on the role of caveolin-1 in several soft tissue and bone sarcomas and discusses the use of this protein as a potential diagnostic and prognostic marker and as a therapeutic target.

Caveolin-1 upregulation mediates suppression of primary breast tumor growth and brain metastases by stat3 inhibition

Stat3 activation has been implicated as an important driver of brain metastasis in breast cancer, but the critical targets of Stat3 in this process are yet to be fully defined. In this study, we identified the lipid raft organizing protein Caveolin-1 (Cav-1) as a critical genetic target of Stat3 in this process. In human breast cancers, we found that activated Stat3 correlated with attenuation of Cav-1 in brain metastases relative to primary tumors. Cav-1 promoter activity and gene expression were increased by overexpressing an activated form of Stat3 but decreased by attenuation of Stat3 activity or expression. We identified putative Stat3-binding elements in the Cav-1 promoter and showed a direct repression of Cav-1 transcription by Stat3. Reciprocally, we showed that strategies to increase or decrease Cav-1 expression were sufficient to attenuate or promote breast cancer cell invasion. Furthermore, increased expression of Cav-1 phenocopied the effects of Stat3 activation in blocking primary tumor growth and abrogating formation of brain metastases. Collectively, our findings provide clinical and mechanistic evidence that Cav-1 is a critical target for suppression by Stat3 in driving invasion and metastasis of breast cancer cells.

Transient gene silencing of galectin-3 suppresses pancreatic cancer cell migration and invasion through degradation of β-catenin

Pancreatic cancer is a leading cause of cancer-related mortality and often has a poor prognosis because of its late diagnosis, aggressive local invasion, early metastasis and poor response to chemotherapy. The chemotherapeutic agent gemcitabine is effective for treating advanced pancreatic cancer, but its efficacy remains less than satisfactory. It is expected that further investigation of pancreatic cancer cell invasion and development of strategies to block this process should improve the disease prognosis. In this study, we tested our hypothesis that galectin-3 (gal-3), a multifunctional member of the β-galactoside-binding protein family, may regulate pancreatic cancer cell motility and silencing of it inhibit cell motility. Previous studies demonstrated that this protein is associated with tumor cell adhesion, proliferation, differentiation, angiogenesis, apoptosis and metastasis. Here, we used gal-3 small interfering RNA (siRNA) to silence its expression in various pancreatic cancer cell lines to determine whether gal-3 regulates cell proliferation, migration and invasion in vitro. We found that silencing gal-3 reduced cellular migration and invasion, but failed to affect proliferation. In gal-3 siRNA-transfected cells, we detected a decrease in β-catenin expression, an important signal for cancer cell invasion, which was caused by downregulation of phosphorylated Akt and GSK-3β. We also found that matrix metalloproteinase (MMP)-2 expression was reduced by gal-3 silencing. These results indicate that gal-3-mediated invasion via MMP-2 regulated by β-catenin degradation is initiated by Akt phosphorylation in pancreatic cancer cells. Our results suggest that gal-3 can be a novel therapeutic target in pancreatic cancer.

AMP-activated protein kinase suppresses matrix metalloproteinase-9 expression in mouse embryonic fibroblasts

Matrix metalloproteinase-9 (MMP-9) plays a critical role in tissue remodeling under both physiological and pathological conditions. Although MMP-9 expression is low in most cells and is tightly controlled, the mechanism of its regulation is poorly understood. We utilized mouse embryonic fibroblasts (MEFs) that were nullizygous for the catalytic α subunit of AMP-activated protein kinase (AMPK), which is a key regulator of energy homeostasis, to identify AMPK as a suppressor of MMP-9 expression. Total AMPKα deletion significantly elevated MMP-9 expression compared with wild-type (WT) MEFs, whereas single knock-out of the isoforms AMPKα1 and AMPKα2 caused minimal change in the level of MMP-9 expression. The suppressive role of AMPK on MMP-9 expression was mediated through both its activity and presence. The AMPK activators 5-amino-4-imidazole carboxamide riboside and A769662 suppressed MMP-9 expression in WT MEFs, and AMPK inhibition by the overexpression of dominant negative (DN) AMPKα elevated MMP-9 expression. However, in AMPKα(-/-) MEFs transduced with DN AMPKα, MMP-9 expression was suppressed. AMPKα(-/-) MEFs showed increased phosphorylation of IκBα, expression of IκBα mRNA, nuclear localization of nuclear factor-κB (NF-κB), and DNA-binding activity of NF-κB compared with WT. Consistently, selective NF-κB inhibitors BMS345541 and SM7368 decreased MMP-9 expression in AMPKα(-/-) MEFs. Overall, our results suggest that both AMPKα isoforms suppress MMP-9 expression and that both the activity and presence of AMPKα contribute to its function as a regulator of MMP-9 expression by inhibiting the NF-κB pathway.

Caveolin-1 modulates the ability of Ewing's sarcoma to metastasize

Metastasis is the final stage of tumor progression and is thought to be responsible for up to 90% of deaths associated with solid tumors. Caveolin-1 (CAV1) regulates multiple cancer-associated processes related to malignant tumor progression. In the present study, we tested the hypothesis that CAV1 modulates the metastatic ability of cells from the Ewing's sarcoma family of tumors (ESFT). First, we analyzed the expression of CAV1 by immunostaining a tissue microarray containing 43 paraffin-embedded ESFT tumors with known EWS translocations. Even though no evidence was found for a significant association between CAV1 expression and stage, size or tumor site, all metastatic samples (10 of 10) had significantly high CAV1 expression, suggesting that high CAV1 content could positively contribute to enhance ESFT metastasis. To determine the effect of CAV1 on the migratory and invasive capabilities of ESFT cells, we knocked down CAV1 expression in TC252 and A673 cells by stably transfecting a previously validated shRNA construct. In vitro, migration and invasion assays showed that for both cell lines, CAV1 knocked-down cells migrated and invaded significantly less (P ≤ 0.01) than control cells. Moreover, control A673 cells introduced into BALB/c nude mice by tail vein injection strongly colonized the lungs. In contrast, animals injected with CAV1 knocked-down cells showed either no incidence of metastasis or developed lung metastases after a significant delay (P < 0.0001). Finally, we show that the molecular mechanisms by which CAV1 carries out its key role in regulating ESFT metastasis involve matrix metalloproteinase production and activation as well as the control of the expression of SPARC, a known determinant of lung colonization.

Oxymatrine inhibits MMP-2 expression and reduces cell invasion in human pancreatic carcinoma cell line SW1990

AIM: To examine the effects of treatment with oxymatrine (OM) on MMP-2 expression and cell invasion in human pancreatic carcinoma cell line SW1990.

METHODS: Cultured SW1990 cells were randomly divided into two groups: control group and OM group. The OM group was further divided into three subgroups, which were treated with three different doses of OM (1, 2 and 4 g/L). MMP-2 expression in SW1990 cells was analyzed by real-time RT-PCR. Cell invasion, migration and proliferation were measured by scratch assay, transwell invasion assay and MTT assay, respectively.

RESULTS: The expression levels of MMP-2 mRNA in SW1990 cells in the three OM subgroups were significantly lower than that in the control group (0.53 ± 0.03, 0.42 ± 0.02, 0.29 ± 0.03 vs 0.70 ± 0.03, all P < 0.05). The invasion of cells in the three OM subgroups was markedly lower than that in the control group (325 ± 64.43, 206 ± 84.76, 124 ± 46.78 vs 498 ± 78.54, all P < 0.05). The mobility of cells in the three OM subgroups was also significantly lower than that in the control group (385.0 ± 58.9, 287.0 ± 79.8, 186.0 ± 60.9 vs 586.0 ± 85.8, all P < 0.05).

CONCLUSION: OM reduces the invasion of SW1990 cells possibly by inhibiting the expression of MMP-2.

Regulation of lung cancer cell migration and invasion by reactive oxygen species and caveolin-1

The acquired capability of tumor cells to migrate and invade neighboring tissues is associated with high metastatic potential and advanced stage of cancers. Recently, signaling molecules such as reactive oxygen species (ROS) and caveolin-1 (Cav-1) have been implicated in the aggressive behavior of cancer cells. However, the roles of specific ROS in cancer cell migration and Cav-1 regulation are unclear. We demonstrate here that Cav-1 plays an important role in the migration and invasion of human lung carcinoma H460 cells and that these effects are differentially regulated by cellular ROS. Using various known inhibitors and donors of ROS, we found that different ROS have different effects on Cav-1 expression and cell migration and invasion. Superoxide anion and hydrogen peroxide down-regulated Cav-1 expression and inhibited cell migration and invasion, whereas hydroxyl radical up-regulated the Cav-1 expression and promoted cell migration and invasion. The down-regulating effect of superoxide anion and hydrogen peroxide on Cav-1 is mediated through a transcription-independent mechanism that involves protein degradation via the ubiquitin-proteasome pathway. These results indicate the essential role of different ROS in cancer cell motility and through Cav-1 expression, which may provide a key mechanism controlling tumor progression and metastasis. The up-regulation of Cav-1 and cell motility by hydroxyl free radical suggests an important role of this ROS as a positive regulator of tumor progression.

PTRF-cavin-1 expression decreases the migration of PC3 prostate cancer cells: role of matrix metalloprotease 9

Caveolae are specialized plasma membrane subdomains with a distinct lipid and protein composition, which play an essential role in cell physiology by performing trafficking and signalling functions. The structure and functions of caveolae have been shown to require caveolin-1, a major protein component of caveolae. Caveolin-1 expression and secretion are increased in metastatic prostate cancer, and caveolin-1 seems to contribute to prostate cancer growth and metastasis. Recently, a cytoplasmic protein named PTRF (Polymerase I and Transcript Release Factor) or cavin-1 was found to be required, in concert with caveolin-1, for the formation and functions of caveolae. Genetic ablation of PTRF results in loss of caveolae while caveolin-1 is still expressed, albeit at reduced level, but associates with flat plasma membrane. In metastatic PC3 prostate cancer cells that express abundant caveolin-1 but no PTRF, heterologous PTRF expression restores caveola formation and caveolin-1 distribution (Hill et al., 2008; Cell 132, 113-124). We now show that PTRF/cavin-1-expressing PC3 cells exhibit decreased migration, and that this effect is mediated by reduced MMP9 production. PTRF/cavin-1, and to a lesser extent, cavin-2, -3, and -4 all decreased MMP9. We further show that the PTRF/cavin-1-mediated reduction of MMP9 production is independent of caveola formation. Taken together, our results suggest that PTRF/cavin-1 expression alters prostate cancer aggressiveness.