CAV-1 contributes to bladder cancer progression by inducing epithelial-to-mesenchymal transition

Inhibition of glycolysis and Src/Akt signaling reduces Caveolin-1-enhanced metastasis

Metastasis is the leading cause of cancer-related deaths, making the development of novel, more effective therapies imperative to alleviate patient suffering. Metabolic switching is a hallmark of cancer cells that facilitates metastasis. Cancer cells obtain most of their energy and intermediate metabolites, which are required to proliferate and metastasize, through aerobic glycolysis. Previous work from our laboratory has shown that Caveolin-1 (CAV1) expression in cancer cells promotes glycolysis and metastasis. Here, we sought to determine if limiting glycolysis reduced CAV1-enhanced metastasis and to identify the mechanism(s) involved. We evaluated the effects of the glycolysis inhibitor 2-deoxy-D-glucose (2-DG) in metastatic melanoma and breast cancer cell lines expressing or not CAV1. Non-cytotoxic concentrations of 2-DG (1 mM) inhibited the migration of B16-F10 melanoma and MDA-MB-231 breast cancer cells. CAV1-mediated activation of Src/Akt signaling was required for CAV1-enhanced migration and was blocked in the presence of 2-DG. Moreover, inhibition of Akt reduced CAV1-enhanced lung metastasis of B16-F10 cells. Collectively, these findings highlight the importance of CAV1-induced metabolic reprogramming for metastasis and point towards possible therapeutic approaches to prevent metastatic disease by inhibiting glycolysis and Src/Akt signaling.

Identification and analysis of the molecular targets of statins in colorectal cancer

Colorectal cancer (CRC) is the third most common cancer in the world. According to several types of research, statins may impact the development and treatment of CRC. This work aimed to use bioinformatics to discover the relationship between statin targets and differentially expressed genes (DEGs) in CRC patients and determine the possible molecular effect of statins on CRC suppression. We used CRC datasets from the GEO database to select CRC-related DEGs. DGIdb and STITCH databases were used to identify gene targets of subtypes of statin. Further, we identified the statin target of CRC DEGs hub genes by using a Venn diagram of CRC DEGs and statin targets. Funrich and enrichr databases were carried out for the KEGG pathway and gene ontology (GO) enrichment analysis, respectively. GSE74604 and GSE10950 were used to identify CRC DEGs. After analyzing datasets,1370 genes were identified as CRC DEGs, and 345 targets were found for statins. We found that 35 genes are CRC DEGs statin targets. We found that statin targets in CRC were enriched in the receptor and metallopeptidase activity for molecular function, cytoplasm and plasma membrane for cellular component, signal transduction, and cell communication for biological process genes were substantially enriched based on FunRich enrichment. Analysis of the KEGG pathways revealed that the overexpressed DEGs were enriched in the IL-17, PPAR, and Toll-like receptor signaling pathways. Finally, CCNB1, DNMT1, AURKB, RAC1, PPARGC1A, CDKN1A, CAV1, IL1B, and HSPD1 were identified as hub CRC DEGs statin targets. The genetic and molecular aspects of our findings reveal that statins might have a therapeutic effect on CRC.

Cholesterol depletion induces mesenchymal properties in oral squamous cell carcinoma cell line

BACKGROUND

Cholesterol in cell membranes is crucial for cell signaling, adhesion, and migration. Membranes feature cholesterol-rich caveolae with caveolin proteins, playing roles in epithelial-mesenchymal transition and cancer progression. Despite elevated cholesterol levels in tumors, its precise function and the effects of its depletion in oral squamous cell carcinoma remain unclear. The aim of this study was to evaluate the influence of cholesterol depletion in oral squamous cell carcinoma cell line and epithelial-mesenchymal transition process.

METHODS

Cholesterol depletion was induced on SCC-9 cells by methyl-β-cyclodextrin and cell viability, proliferation, apoptosis, and colony formation capacities were evaluated. Gene and protein expressions were evaluated by reverse transcription polymerase chain reaction (RT-qPCR) and Western Blot, respectively, and cell sublocalization was assessed by immunofluorescence.

RESULTS

Cholesterol depletion resulted in alteration of oral squamous cell carcinoma cell morphology at different concentrations of methyl-β-cyclodextrin, as well as decreased cell proliferation and viability rates. Analysis of CAV1 transcript expression revealed increased gene expression in the treated SCC-9 during the 24 h period, at different concentrations of methyl-β-cyclodextrin: 5 , 7.5, 10, and 15 mM, in relation to parental SCC-9. CAV1 protein expression was increased, with subsequent dose-dependent decrease. A statistically significant difference was observed in samples treated with 5 mM of methyl-β-cyclodextrin (p = 0.02, Kruskal-Wallis test). The immunofluorescence assay showed lower cytoplasmic and membrane labeling intensity in the treated samples for CAV1.

CONCLUSION

These findings indicate the modulation of cholesterol as a possible mechanism underlying the regulation of these molecules and activation of epithelial-mesenchymal transition in oral squamous cell carcinoma.

PROM2 overexpression induces metastatic potential through epithelial-to-mesenchymal transition and ferroptosis resistance in human cancers

INTRODUCTION

Despite considerable therapeutic advances in the last 20 years, metastatic cancers remain a major cause of death. We previously identified prominin-2 (PROM2) as a biomarker predictive of distant metastases and decreased survival, thus providing a promising bio-target. In this translational study, we set out to decipher the biological roles of PROM2 during the metastatic process and resistance to cell death, in particular for metastatic melanoma.

METHODS AND RESULTS

Methods and results: We demonstrated that PROM2 overexpression was closely linked to an increased metastatic potential through the increase of epithelial-to-mesenchymal transition (EMT) marker expression and ferroptosis resistance. This was also found in renal cell carcinoma and triple negative breast cancer patient-derived xenograft models. Using an oligonucleotide anti-sense anti-PROM2, we efficaciously decreased PROM2 expression and prevented metastases in melanoma xenografts. We also demonstrated that PROM2 was implicated in an aggravation loop, contributing to increase the metastatic burden both in murine metastatic models and in patients with metastatic melanoma. The metastatic burden is closely linked to PROM2 expression through the expression of EMT markers and ferroptosis cell death resistance in a deterioration loop.

CONCLUSION

Our results open the way for further studies using PROM2 as a bio-target in resort situations in human metastatic melanoma and also in other cancer types.

Mechanotransduction and epigenetic modulations of chromatin: Role of mechanical signals in gene regulation

Mechanical forces may be generated within a cell due to tissue stiffness, cytoskeletal reorganization, and the changes (even subtle) in the cell's physical surroundings. These changes of forces impose a mechanical tension within the intracellular protein network (both cytosolic and nuclear). Mechanical tension could be released by a series of protein-protein interactions often facilitated by membrane lipids, lectins and sugar molecules and thus generate a type of signal to drive cellular processes, including cell differentiation, polarity, growth, adhesion, movement, and survival. Recent experimental data have accentuated the molecular mechanism of this mechanical signal transduction pathway, dubbed mechanotransduction. Mechanosensitive proteins in the cell's plasma membrane discern the physical forces and channel the information to the cell interior. Cells respond to the message by altering their cytoskeletal arrangement and directly transmitting the signal to the nucleus through the connection of the cytoskeleton and nucleoskeleton before the information despatched to the nucleus by biochemical signaling pathways. Nuclear transmission of the force leads to the activation of chromatin modifiers and modulation of the epigenetic landscape, inducing chromatin reorganization and gene expression regulation; by the time chemical messengers (transcription factors) arrive into the nucleus. While significant research has been done on the role of mechanotransduction in tumor development and cancer progression/metastasis, the mechanistic basis of force-activated carcinogenesis is still enigmatic. Here, in this review, we have discussed the various cues and molecular connections to better comprehend the cellular mechanotransduction pathway, and we also explored the detailed role of some of the multiple players (proteins and macromolecular complexes) involved in mechanotransduction. Thus, we have described an avenue: how mechanical stress directs the epigenetic modifiers to modulate the epigenome of the cells and how aberrant stress leads to the cancer phenotype.

Involvement of caveolin-1 in skin diseases

The skin is the outermost layer and largest organ in the human body. Since the skin interfaces with the environment, it has a variety of roles, including providing a protective barrier against external factors, regulating body temperature, and retaining water in the body. It is also involved in the immune system, interacting with immune cells residing in the dermis. Caveolin-1 (CAV-1) is essential for caveolae formation and has multiple functions including endocytosis, lipid homeostasis, and signal transduction. CAV-1 is known to interact with a variety of signaling molecules and receptors and may influence cell proliferation and migration. Several skin-related disorders, especially those of the inflammatory or hyperproliferative type such as skin cancers, psoriasis, fibrosis, and wound healing, are reported to be associated with aberrant CAV-1 expression. In this review, we have explored CAV-1 involvement in skin physiology and skin diseases.

Mitochondrial Dysfunction and the Glycolytic Switch Induced by Caveolin-1 Phosphorylation Promote Cancer Cell Migration, Invasion, and Metastasis

Simple Summary

Caveolin-1 (CAV1) is a membrane protein that has been attributed a dual role in cancer, acting at early stages as a tumor suppressor and in later stages of the disease as a promoter of metastasis. In the latter case, enhanced expression of CAV1 favors the malignant phenotype and correlates with a poorer prognosis of the patients. Bearing in mind that the reprogramming of energy metabolism is required in cancer cells to meet both the bioenergetic and biosynthetic needs to sustain increased proliferation, migration, and invasion, we evaluated the metabolism of metastatic cells expressing or not CAV1. In this study, we show that the expression of CAV1 promotes in cancer cells a metabolic switch to an aerobic, glycolytic phenotype by blocking mitochondrial respiration.

Abstract

Cancer cells often display impaired mitochondrial function, reduced oxidative phosphorylation, and augmented aerobic glycolysis (Warburg effect) to fulfill their bioenergetic and biosynthetic needs. Caveolin-1 (CAV1) is a scaffolding protein that promotes cancer cell migration, invasion, and metastasis in a manner dependent on CAV1 phosphorylation on tyrosine-14 (pY14). Here, we show that CAV1 expression increased glycolysis rates, while mitochondrial respiration was reduced by inhibition of the mitochondrial complex IV. These effects correlated with increased reactive oxygen species (ROS) levels that favored CAV1-induced migration and invasion. Interestingly, pY14-CAV1 promoted the metabolic switch associated with increased migration/invasion and augmented ROS-inhibited PTP1B, a phosphatase that controls pY14 levels. Finally, the glycolysis inhibitor 2-deoxy-D-glucose reduced CAV1-enhanced migration in vitro and metastasis in vivo of murine melanoma cells. In conclusion, CAV1 promotes the Warburg effect and ROS production, which inhibits PTP1B to augment CAV1 phosphorylation on tyrosine-14, thereby increasing the metastatic potential of cancer cells.

Frontiers in Lichen Planopilaris and Frontal Fibrosing Alopecia Research: Pathobiology Progress and Translational Horizons

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are primary, lymphocytic cicatricial hair loss disorders. These model epithelial stem cell (SC) diseases are thought to result from a CD8⁺ T-cell‒dominated immune attack on the hair follicle (HF) SC niche (bulge) after the latter has lost its immune privilege (IP) for as yet unknown reasons. This induces both apoptosis and pathological epithelial‒mesenchymal transition in epithelial SCs, thus depletes the bulge, causes fibrosis, and ultimately abrogates the HFs' capacity to regenerate. In this paper, we synthesize recent progress in LPP and FFA pathobiology research, integrate our limited current understanding of the roles that genetic, hormonal, environmental, and other factors may play, and define major open questions. We propose that LPP and FFA share a common initial pathobiology, which then bifurcates into two distinct clinical phenotypes, with macrophages possibly playing a key role in phenotype determination. As particularly promising translational research avenues toward direly needed progress in the management of these disfiguring, deeply distressful cicatricial alopecia variants, we advocate to focus on the development of bulge IP and epithelial SC protectants such as, for example, topically effective, HF‒penetrating and immunoinhibitory preparations that contain tacrolimus, peroxisome proliferator-activated receptor-γ, and/or CB1 agonists.

Proteomics as a Complementary Technique to Characterize Bladder Cancer

Simple Summary

Although immunohistochemistry is a routine technique in clinics, and genomics has been rapidly incorporated, proteomics is a step behind. This general situation is also the norm in bladder cancer research. This review shows the contributions of proteomics to the molecular classification of bladder cancer, and to the study of histopathology due to tissue insults caused by tumors. Furthermore, the importance of proteomics for understanding the cellular and molecular changes as a consequence of the therapy of bladder cancer cannot be neglected.

Abstract

Bladder cancer (BC) is the most common tumor of the urinary tract and is conventionally classified as either non-muscle invasive or muscle invasive. In addition, histological variants exist, as organized by the WHO-2016 classification. However, innovations in next-generation sequencing have led to molecular classifications of BC. These innovations have also allowed for the tracing of major tumorigenic pathways and, therefore, are positioned as strong supporters of precision medicine. In parallel, immunohistochemistry is still the clinical reference to discriminate histological layers and to stage BC. Key contributions have been made to enlarge the panel of protein immunomarkers. Moreover, the analysis of proteins in liquid biopsy has also provided potential markers. Notwithstanding, their clinical adoption is still low, with very few approved tests. In this context, mass spectrometry-based proteomics has remained a step behind; hence, we aimed to develop them in the community. Herein, the authors introduce the epidemiology and the conventional classifications to review the molecular classification of BC, highlighting the contributions of proteomics. Then, the advances in mass spectrometry techniques focusing on maintaining the integrity of the biological structures are presented, a milestone for the emergence of histoproteomics. Within this field, the review then discusses selected proteins for the comprehension of the pathophysiological mechanisms of BC. Finally, because there is still insufficient knowledge, this review considers proteomics as an important source for the development of BC therapies.

Eupafolin induces apoptosis and autophagy of breast cancer cells through PI3K/AKT, MAPKs and NF-κB signaling pathways

Eupafolin is a flavonoid that can be extracted from common sage. Previous studies have reported that Eupafolin has antioxidant, anti-inflammatory and anti-tumor properties. However, no studies have investigated the role of Eupafolin in breast cancer. Herein, we investigated the effect of Eupafolin on two human breast cancer cell lines, as well as its potential mechanism of action. Next, the data showed that proliferation, migration and invasion ability of breast cancer cells that were treated with Eupafolin was significantly reduced, while the apoptosis rate was significantly increased. In addition, Eupafolin treatment caused breast cancer cell proliferation to be blocked in the S phase. Moreover, Eupafolin significantly induced autophagy in breast cancer cells, with an increase in the expression of LC3B-II. PI3K/AKT, MAPKs and NF-κB pathways were significantly inhibited by Eupafolin treatment. Additionally, 3-MA (a blocker of autophagosome formation) significantly reduced Eupafolin-induced activation of LC3B-II in breast cancer cells. Furthermore, Eupafolin displayed good in vitro anti-angiogenic activity. Additionally, anti-breast cancer activity of Eupafolin was found to be partially mediated by Cav-1. Moreover, Eupafolin treatment significantly weakened carcinogenesis of MCF-7 cells in nude mice. Therefore, this data provides novel directions on the use of Eupafolin for treatment of breast cancer.

Role of caveolin-1 in human organ function and disease: friend or foe?

Caveolin-1 (Cav-1) is a structural protein component of caveolae, which are invaginations of the plasma membrane involved in various cellular processes, including endocytosis, extracellular matrix organization, cholesterol distribution, cell migration, and signaling. Mounting evidence over the last 10-15 years has demonstrated a central role of Cav-1 in many diseases, such as cancer, diabetes, and fibrosis. Cav-1 plays positive and negative roles in various diseases through its different regulation pathways. Here, we review the current knowledge on Cav-1 in different diseases and discuss the role of this protein in human organs and diseases.

MicroRNA-203 inhibits epithelial-mesenchymal transition, migration, and invasion of renal cell carcinoma cells via the inactivation of the PI3K/AKT signaling pathway by inhibiting CAV1

The present study aimed to evaluate the underlying mechanism of microRNA-203 (miR-203) in renal cell carcinoma (RCC) involving the PI3K/AKT signaling pathway. The results revealed downregulated miR-203 and upregulated CAV1 in RCC tissues. Upregulated miR-203 and downregulated CAV1 increased E-cadherin expression and cell apoptosis, decreased β-catenin and N-cadherin expression and cell proliferation, migration and invasion, and blocked cell cycle entry. CAV1, a target gene of miR-203, decreased by up-regulated miR-203, and silencing CAV1 led to the inactivation of PI3K/AKT signaling pathway. In conclusion, our findings suggested that miR-203-mediated direct suppression of CAV1 inhibits EMT of RCC cells via inactivation of the PI3K/AKT signaling pathway.

Caveolin-1 facilitates cell migration by upregulating nuclear receptor 4A2/retinoid X receptor α-mediated β-galactoside α2,6-sialyltransferase I expression in human hepatocarcinoma cells

It has been reported that caveolin-1 (Cav-1) acts as a tumor promoter in hepatocellular carcinoma (HCC). Our previous studies showed that Cav-1 promoted mouse hepatocarcinoma cell adhesion to fibronectin by upregulating β-galactoside α2,6-sialyltransferase I (ST6Gal-I) expression. However, the detailed mechanism by which Cav-1 regulates ST6Gal-I is not fully understood. In this study, we found that the expression levels of Cav-1 and ST6Gal-I were increased in HCC tissues and correlated with poor prognosis. Cav-1 upregulated ST6Gal-I expression to promote the migration and invasion of HCC cells by inducing epithelial-to-mesenchymal transition. Importantly, the binding of the transcription factor nuclear receptor 4A2/retinoid X receptor alpha (NR4A2/RXRα) to the -550/-200 region of the ST6GAL1 promoter was critical for Cav-1-induced ST6GAL1 gene expression. Furthermore, Cav-1 expression activated the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling pathway, followed by upregulation of NR4A2 expression and phosphorylation of RXRα, which facilitated the complex of NR4A2 and phosphorylated RXRα forming and binding to the ST6GAL1 promoter region to induce its transcription. Finally, in the diethylnitrosamine (DEN)-induced HCC murine model, the expression levels of NR4A2, p-RXRα, ST6Gal-I, and α2,6-linked sialic acid decreased in parallel in Cav-1^-/- mice compared with Cav-1^+/+ mice, which was consistent with the above in vitro results. These findings provide insight into the mechanism of ST6GAL1 gene transcription mediated by Cav-1, which may lead to the development of novel therapeutic strategies targeting metastasis in HCC.

A Cell Membrane-Level Approach to Cicatricial Alopecia Management: Is Caveolin-1 a Viable Therapeutic Target in Frontal Fibrosing Alopecia?

Irreversible destruction of the hair follicle (HF) in primary cicatricial alopecia and its most common variant, frontal fibrosing alopecia (FFA), results from apoptosis and pathological epithelial-mesenchymal transition (EMT) of epithelial HF stem cells (eHFSCs), in conjunction with the collapse of bulge immune privilege (IP) and interferon-gamma-mediated chronic inflammation. The scaffolding protein caveolin-1 (Cav1) is a key component of specialized cell membrane microdomains (caveolae) that regulates multiple signaling events, and even though Cav1 is most prominently expressed in the bulge area of human scalp HFs, it has not been investigated in any cicatricial alopecia context. Interestingly, in mice, Cav1 is involved in the regulation of (1) key HF IP guardians (TGF-β and α-MSH signaling), (2) IP collapse inducers/markers (IFNγ, substance P and MICA), and (3) EMT. Therefore, we hypothesize that Cav1 may be an unrecognized, important player in the pathobiology of cicatricial alopecias, and particularly, in FFA, which is currently considered as the most common type of primary lymphocytic scarring alopecia in the world. We envision that localized therapeutic inhibition of Cav1 in management of FFA (by cholesterol depleting agents, i.e., cyclodextrins/statins), could inhibit and potentially reverse bulge IP collapse and pathological EMT. Moreover, manipulation of HF Cav1 expression/localization would not only be relevant for management of cicatricial alopecia, but FFA could also serve as a model disease for elucidating the role of Cav1 in other stem cell- and/or IP collapse-related pathologies.

Hypoxia-Induced Suppression of Antiapoptotic Bcl-2 Expression in Human Bladder Tumor Cells Is Regulated by Caveolin-1-Dependent Adenosine Monophosphate-Activated Protein Kinase Activity

Purpose

Adenosine monophosphate-activated protein kinase (AMPK) is thought to inhibit cell proliferation or promote cell death, but the details remain unclear. In this study, we propose that AMPK inhibits the expression of anti-apoptotic B-cell lymphoma 2 (Bcl-2) by relying on the hypoxia-inducible factor 1 alpha (HIF-1α)-induced caveolin-1 (Cav-1) expression pathway in noninvasive human bladder tumor (RT4) cells.

Methods

In cells exposed to a hypoxic environment (0.5% oxygen), the levels of expression and phospho-activity of the relevant signaling enzymes were examined via Western blots and reverse transcription-polymerase chain reaction. Cell proliferation was assessed using a Cell Counting Kit-8 assay.

Results

The level of expression of Cav-1 was very low or undetectable in RT4 cells. Hypoxia was associated with significantly decreased cell growth, along with marked induction of HIF-1α and Cav-1 expression; additionally, it suppressed the expression of the antiapoptotic marker Bcl-2 while leaving AMPK activity unchanged. Under hypoxic conditions, HIF-1α acts as a transcription factor for Cav-1 mRNA gene expression. The cell growth and Bcl-2 expression suppressed under hypoxia were reversed along with decreases in the induced HIF-1α and Cav-1 levels by AMPK activation with metformin (1mM) or phenformin (0.1mM). In addition, pretreatment with AMPK small interfering RNA not only increased the hypoxia-induced expression of HIF-1α and Cav-1, but also reversed the suppression of Bcl-2 expression. These results suggest that HIF-1α and Cav-1 expression in hypoxic environments is regulated by basal AMPK activity; therefore, the inhibition of Bcl-2 expression cannot be expected when AMPK activity is suppressed, even if Cav-1 expression is elevated.

Conclusions

For the first time, we find that AMPK activation can regulate HIF-1α induction as well as HIF-1α-induced Cav1 expression, and the hypoxia-induced inhibitory effect on the antiapoptotic pathway in RT4 cells is due to Cav-1-dependent AMPK activity.

Role of Cholesterol and Lipid Rafts in Cancer Signaling: A Promising Therapeutic Opportunity?

Cholesterol is a lipid molecule that plays an essential role in a number of biological processes, both physiological and pathological. It is an essential structural constituent of cell membranes, and it is fundamental for biosynthesis, integrity, and functions of biological membranes, including membrane trafficking and signaling. Moreover, cholesterol is the major lipid component of lipid rafts, a sort of lipid-based structures that regulate the assembly and functioning of numerous cell signaling pathways, including those related to cancer, such as tumor cell growth, adhesion, migration, invasion, and apoptosis. Considering the importance of cholesterol metabolism, its homeostasis is strictly regulated at every stage: import, synthesis, export, metabolism, and storage. The alterations of this homeostatic balance are known to be associated with cardiovascular diseases and atherosclerosis, but mounting evidence also connects these behaviors to increased cancer risks. Although there is conflicting evidence on the role of cholesterol in cancer development, most of the studies consistently suggest that a dysregulation of cholesterol homeostasis could lead to cancer development. This review aims to discuss the current understanding of cholesterol homeostasis in normal and cancerous cells, summarizing key findings from recent preclinical and clinical studies that have investigated the role of major players in cholesterol regulation and the organization of lipid rafts, which could represent promising therapeutic targets.

Betulinic Acid Restricts Human Bladder Cancer Cell Proliferation In Vitro by Inducing Caspase-Dependent Cell Death and Cell Cycle Arrest, and Decreasing Metastatic Potential

Betulinic acid (BA) is a naturally occurring pentacyclic triterpenoid and generally found in the bark of birch trees (Betula sp.). Although several studies have been reported that BA has diverse biological activities, including anti-tumor effects, the underlying anti-cancer mechanism in bladder cancer cells is still lacking. Therefore, this study aims to investigate the anti-proliferative effect of BA in human bladder cancer cell lines T-24, UMUC-3, and 5637, and identify the underlying mechanism. Our results showed that BA induced cell death in bladder cancer cells and that are accompanied by apoptosis, necrosis, and cell cycle arrest. Furthermore, BA decreased the expression of cell cycle regulators, such as cyclin B1, cyclin A, cyclin-dependent kinase (Cdk) 2, cell division cycle (Cdc) 2, and Cdc25c. In addition, BA-induced apoptosis was associated with mitochondrial dysfunction that is caused by loss of mitochondrial membrane potential, which led to the activation of mitochondrial-mediated intrinsic pathway. BA up-regulated the expression of Bcl-2-accociated X protein (Bax) and cleaved poly-ADP ribose polymerase (PARP), and subsequently activated caspase-3, -8, and -9. However, pre-treatment of pan-caspase inhibitor markedly suppressed BA-induced apoptosis. Meanwhile, BA did not affect the levels of intracellular reactive oxygen species (ROS), indicating BA-mediated apoptosis was ROS-independent. Furthermore, we found that BA suppressed the wound healing and invasion ability, and decreased the expression of Snail and Slug in T24 and 5637 cells, and matrix metalloproteinase (MMP)-9 in UMUC-3 cells. Taken together, this is the first study showing that BA suppresses the proliferation of human bladder cancer cells, which is due to induction of apoptosis, necrosis, and cell cycle arrest, and decrease of migration and invasion. Furthermore, BA-induced apoptosis is regulated by caspase-dependent and ROS-independent pathways, and these results provide the underlying anti-proliferative molecular mechanism of BA in human bladder cancer cells.

Cholesterol and Sphingolipid Enriched Lipid Rafts as Therapeutic Targets in Cancer

Lipid rafts are critical cell membrane lipid platforms enriched in sphingolipid and cholesterol content involved in diverse cellular processes. They have been proposed to influence membrane properties and to accommodate receptors within themselves by facilitating their interaction with ligands. Over the past decade, technical advances have improved our understanding of lipid rafts as bioactive structures. In this review, we will cover the more recent findings about cholesterol, sphingolipids and lipid rafts located in cellular and nuclear membranes in cancer. Collectively, the data provide insights on the role of lipid rafts as biomolecular targets in cancer with good perspectives for the development of innovative therapeutic strategies.

Adaptive phenotypic modulations lead to therapy resistance in chronic myeloid leukemia cells

Tyrosine kinase inhibitor (TKI) resistance is a major problem in chronic myeloid leukemia (CML). We generated a TKI-resistant K562 sub-population, K562-IR, under selective imatinib-mesylate pressure. K562-IR cells are CD34-/CD38-, BCR-Abl-independent, proliferate slowly, highly adherent and form intact tumor spheroids. Loss of CD45 and other hematopoietic markers reveal these cells have diverged from their hematopoietic origin. CD34 negativity, high expression of E-cadherin and CD44; decreased levels of CD45 and β-catenin do not fully confer with the leukemic stem cell (LSC) phenotype. Expression analyses reveal that K562-IR cells differentially express tissue/organ development and differentiation genes. Our data suggest that the observed phenotypic shift is an adaptive process rendering cells under TKI stress to become oncogene independent. Cells develop transcriptional instability in search for a gene expression framework suitable for new environmental stresses, resulting in an adaptive phenotypic shift in which some cells partially display LSC-like properties. With leukemic/cancer stem cell targeted therapies underway, the difference between treating an entity and a spectrum of dynamic cellular states will have conclusive effects on the outcome.

Dynamic Regulation of Caveolin-1 Phosphorylation and Caveolae Formation by Mammalian Target of Rapamycin Complex 2 in Bladder Cancer Cells

The mammalian target of rapamycin (mTOR) and associated phosphatidylinositol 3-kinase/AKT/mTOR signaling pathway is commonly up-regulated in cancer, including bladder cancer. mTOR complex 2 (mTORC2) is a major regulator of bladder cancer cell migration and invasion, but the mechanisms by which mTORC2 regulates these processes are unclear. A discovery mass spectrometry and reverse-phase protein array-based proteomics dual approach was used to identify novel mTORC2 phosphoprotein targets in actively invading cancer cells. mTORC2 targets included focal adhesion kinase, proto-oncogene tyrosine-protein kinase Src, and caveolin-1 (Cav-1), among others. Functional testing shows that mTORC2 regulates Cav-1 localization and dynamic phosphorylation of Cav-1 on Y14. Regulation of Cav-1 activity by mTORC2 also alters the abundance of caveolae, which are specialized lipid raft invaginations of the plasma membrane associated with cell signaling and membrane compartmentalization. Our results demonstrate a unique role for mTORC2-mediated regulation of caveolae formation in actively migrating cancer cells.

Caveolin-1 and dynamin-2 overexpression is associated with the progression of bladder cancer

Caveolae-mediated endocytosis regulates cell adhesion and growth in an anchorage-dependent manner. Studies of the endocytic function of caveolae have suggested a wide-ranging list of cargoes, including a number of receptors and extracellular proteins, ligands and nutrients from the extracellular matrix. Disruption of the processes of caveolae-mediated endocytosis mediated by signaling proteins is critical to cellular integrity. Caveolin-1 and dynamin-2 are the 2 major proteins associated with endocytotic function. Mechanistically, dynamin-2 has a co-equal role with caveolin-1 in terms of caveolae-derived endosome formation. Recent studies have revealed the pathological outcomes associated with the dysregulation of caveolin-1 and dynamin-2 expression. Increased expression levels of the gene for caveolin, Cav-1, resulting in augmented cellular metastasis and invasion, have been demonstrated in various types of cancer, and overexpression of the gene for dynamin-2, DNM2, has been associated with tumorigenesis in cervical, pancreatic and lung cancer. An increased expression of Cav-1 and DNM2 is known to be associated with the invasive behavior of cancer cells, and with cancer progression. Furthermore, it has been previously demonstrated that, in caveolar assembly and caveolae mediated endocytosis, Cav-1 interacts directly with DNM2 during the processes. Altered expression of the 2 genes is critical for the normal function of the cell. The expression patterns of Cav-1 and DNM2 have been previously examined in bladder cancer cell lines, and were each demonstrated to be overexpressed. In the present study, the expression levels of these 2 genes in bladder cancer samples were quantified. The gene expression levels of Cav-1 and DNM2 were identified to be increased 8.88- and 8.62-fold, respectively, in tumors compared with the normal controls. Furthermore, high-grade tumors exhibited significantly increased expression levels of Cav-1 and DNM2 (both P<0.0001) compared with the low-grade tumors. In addition, compared with normal control samples, the expression of the 2 genes in tumor samples was observed to be highly significant (P<0.0001), with a marked positive correlation identified for the tumors (Pearson's correlation coefficient, r=0.80 for the tumor samples vs. r=0.32 in the normal control samples). Taken together, the results of the present study demonstrated that the overexpression of Cav-1 and DNM2 genes, and a determination of their correlation coefficients, may be a potential risk factor for bladder cancer, in addition to other clinical factors.

Lost expression of cell adhesion molecule 1 is associated with bladder cancer progression and recurrence and its overexpression inhibited tumor cell malignant behaviors

Cell adhesion molecule 1 (CADM1) regulates cell-cell adhesion and an altered expression level is associated with tumorigenesis and progression. The present study assessed CADM1 expression level in 84 bladder tissues to investigate the association with clinicopathological parameters from bladder cancer patients and then investigated the effects of CADM1 overexpression on T24 bladder cancer cells in vitro. The results demonstrated that expression level of CADM1 protein was significantly reduced in bladder cancer tissues (0.26±0.14) compared with in normal bladder mucosa (0.69±0.092; P<0.01), and methylation of CADM1 promoter was responsible for silencing of CADM1 protein expression and significantly associated with tumor size, recurrence, pathology classification and clinical stage (P<0.05). Overexpression of CADM1 protein inhibited tumor cell proliferation, reduced tumor cell invasion capacity and induced tumor cell apoptosis in vitro. At the gene level, CADM1 expression level upregulated caspase-3 activity and expression of Bax and p27 protein and downregulated levels of B cell lymphoma-2, cyclinD1, cyclinE1 and cyclin dependent kinase 2 proteins. Furthermore, overexpression of CADM1 regulated the expression level of epithelial to mesenchymal transition markers, including increased expression level of E-cadherin and β-catenin, whereas it decreased the levels of Vimentin. The present study demonstrated that lost expression of CADM1 protein may exert an essential role in the development and progression of bladder cancer and suggested that CADM1 may be a novel molecular target for the control of this disease in clinical practice.

Caveolin-1 and -2 regulate cell motility in castration-resistant prostate cancer

Background

Caveolin (Cav)-1 and Cav-2 are cell membrane proteins, which are structural proteins of caveolae and are reported to be positive regulators of cell survival and metastasis in prostate cancer (PC). In a previous study, we reported that elevated levels of Cav-1 and Cav-2 were significantly associated with PC progression. However, their functions in PC have not yet been clarified. In this study, we examined the function of Cav-1 and Cav-2 in PC cell invasiveness and motility.

Materials and methods

We introduced Cav-1- and Cav-2-specific small interfering into PC3 cells to knock-down (KD) both molecules. We also performed cell proliferation assay, wound healing assay, migration assay, and invasion assay using PC3 cells and compared the results between Cav-1-KD, Cav-2-KD, and negative control PC3 cells. In addition, we performed real-time quantitative PCR (RT-qPCR) and RT2 Profiler PCR Array analysis to identify factors influencing migration.

Results

We observed no significant difference in the proliferative and invasive activities of Cav-1-KD and Cav-2-KD PC3 cells; however, the cell motility was significantly decreased compared with negative control PC3 cells. RT-qPCR revealed that the expression of vimentin and N-cadherin was downregulated in Cav-1-KD PC3 cells. In addition, PCR array revealed a decreased expression of MGAT5, MMP13, and MYCL in Cav-1-KD PC3 and ETV4, FGFR4, and SRC in Cav-2-KD PC3.

Conclusion

Cav-1 and Cav-2 may positively contribute to the upregulation of castration-resistant PC cell migration. Cav-induced regulation of several molecules including vimentin, N-cadherin, MGAT5, MMP13, MYCL, ETV4, FGFR4, and SRC may have an important role in PC3 cell motility. However, further examination will be required.

Caveolin-1, cancer and therapy resistance

Resistance of solid tumors to chemo- and radiotherapy remains a major obstacle in anti-cancer treatment. Herein, the membrane protein caveolin-1 (CAV1) came into focus as it is highly expressed in many tumors and high CAV1 levels were correlated with tumor progression, invasion and metastasis, and thus a worse clinical outcome. Increasing evidence further indicates that the heterogeneous tumor microenvironment, also known as the tumor stroma, contributes to therapy resistance resulting in poor clinical outcome. Again, CAV1 seems to play an important role in modulating tumor host interactions by promoting tumor growth, metastasis, therapy resistance and cell survival. However, the mechanisms driving stroma-mediated tumor growth and radiation resistance remain to be clarified. Understanding these interactions and thus, targeting CAV1 may offer a novel strategy for preventing cancer therapy resistance and improving clinical outcomes. In this review, we will summarize the resistance-promoting effects of CAV1 in tumors, and emphasize its role in the tumor-stroma communication as well as the resulting malignant phenotype of epithelial tumors.

Clinical Significance of Gli-1 And Caveolin-1 Expression in the Human Small Cell Lung Cancer

Background: Lung cancer is the leading causes of cancer-related deaths around the world. Abnormal activation of the hedgehog (Hh) signaling pathway has been found to be involved in the occurrence, invasion, and metastasis of cancers. Autophagy also plays a significant role in the growth and metastasis of cancers. However, the correlation between the Hh signaling pathway and autophagy in small cell lung cancer (SCLC) is still poorly understood. This study aimed to investigate the significance of Hh signaling pathway and autophagy in SCLC. Materials and Methods: The expression of the Hh-induced transcriptional factor, glioma associated oncogene-1 (Gli-1) and the autophagy-related molecule caveolin-1 (Cav-1) and their clinical significance was performed to detect and assay by immunohistochemistry in tissue microarray including 70 patients with SCLC. Results: In our study, 47 (67.1%) patients had positive Gli-1 expression, 49 (70.0%) patients had positive Cav-1 expression, and 44 (62.9%) patients had negative fibroblastic Cav-1 expression. In SCLC, Gli-1 expression increased markedly, and was closely associated with decreased fibroblastic Cav-1 expression. Furthermore, we also found that Gli-1 expression was closely associated with increased Cav-1 expression. Conclusions: Our findings suggested that abnormal activation of the Hh signaling pathway is closely related to autophagy in SCLC. We envision that novel targets may come with the further investigation of Gli-1 and Cav-1 in carcinogenesis of SCLC.

ITGB1-dependent upregulation of Caveolin-1 switches TGFβ signalling from tumour-suppressive to oncogenic in prostate cancer

Caveolin-1 (CAV1) is over-expressed in prostate cancer (PCa) and is associated with adverse prognosis, but the molecular mechanisms linking CAV1 expression to disease progression are poorly understood. Extensive gene expression correlation analysis, quantitative multiplex imaging of clinical samples, and analysis of the CAV1-dependent transcriptome, supported that CAV1 re-programmes TGFβ signalling from tumour suppressive to oncogenic (i.e. induction of SLUG, PAI-1 and suppression of CDH1, DSP, CDKN1A). Supporting such a role, CAV1 knockdown led to growth arrest and inhibition of cell invasion in prostate cancer cell lines. Rationalized RNAi screening and high-content microscopy in search for CAV1 upstream regulators revealed integrin beta1 (ITGB1) and integrin associated proteins as CAV1 regulators. Our work suggests TGFβ signalling and beta1 integrins as potential therapeutic targets in PCa over-expressing CAV1, and contributes to better understand the paradoxical dual role of TGFβ in tumour biology.

Caveolin-1 Inhibits Proliferation, Migration, and Invasion of Human Colorectal Cancer Cells by Suppressing Phosphorylation of Epidermal Growth Factor Receptor

Background

Although downregulation of caveolin-1 (Cav-1), which is a key constituent of membrane caveolae and a regulator of cellular processes, is associated with colorectal cancer (CRC), its involvement in the disease progression is largely unknown. This study aimed to explore the role of Cav-1 in CRC and the associated mechanisms.

Material/Methods

Fresh tissues from patients with CRC and human CRC SW480 cells were used to evaluate Cav-1 and Ki-67 expression using immunohistochemistry and Western blotting. The MTS and Transwell assays were performed to determine the effects of Cav-1 overexpression via pcDNA3.1/Cav-1 plasmid on cell proliferation and metastasis. The effect of Cav-1 on the epidermal growth factor receptor (EGFR) activation was evaluated by Western blotting. The correlation of Cav-1 expression with clinicopathological factors was statistically analyzed.

Results

Overexpression of Cav-1 significantly reduced proliferation, migration, and invasion of SW480 cancer cells in vitro. The EGF-induced phosphorylation of EGFR and activations of the RAF-MEK-ERK and PI3K-AKT pathways were adversely regulated by Cav-1 overexpression in vitro. In 76 cases of CRC patients with EGFR expression, a negative correlation was observed between the level of Cav-1 and tumor-node-metastasis stage, lymph node metastasis, and distant metastasis (All p<0.05). Finally, the expression level of Cav-1 was negatively correlated with that of Ki-67.

Conclusions

This report is the first to show that overexpression of Cav-1significantly inhibits the proliferation, migration, and invasion potential of SW480 cells, possibly through reducing EGF-induced EGFR activation. High Cav-1 expression level may be a predictor of positive outcomes in patients with colorectal cancer.

Deregulated expression of miR-107 inhibits metastasis of PDAC through inhibition PI3K/Akt signaling via caveolin-1 and PTEN

Pancreatic ductal adenocarcinoma (PDAC) displays a highly aggressive malignancy and is considered to be an incurable and rapidly lethal disease. MicroRNAs (miRNAs) are small non-coding RNAs of approximately nucleotides that regulate several aspects of tumors pathogenesis, including migration, invasion, metastasis and epithelial-mesenchymal transition. We have found that miR-107 was significantly high expression in PDAC tissues and cells. High miR-107 expression is associated with poor clinicopathological parameters and prognosis in PDAC patients. Deregulated expression of miR-107 in PDAC cells (AsPC-1 and Panc-1) is sufficient to reduce cell migration and invasion, and to induce upregulation of epithelial markers (β-catenin, ZO-1 and E-cadherin) and a decrease of mesenchymal marker expression (ZEB-1 and vimentin). We also found that the caveolin-1, PTEN and p-Akt expression are modulated by miR-107 in PDAC cells. Moreover, our study clearly demonstrated that deregulated expression of miR-107 inhibited cell migration and invasion and EMT by up-regulation of caveolin-1 and PTEN, and inhibition of PI3K/Akt signaling in PDAC cells. Our study suggested that miR‑107 expression might both be a useful indicator of the metastatic potential and provided a new potential therapeutic target in PDAC.

Knockdown of HMGN5 increases the chemosensitivity of human urothelial bladder cancer cells to cisplatin by targeting PI3K/Akt signaling

High-mobility group nucleosome-binding domain 5 (HMGN5) is the latest member of the HMGN family of proteins. Numerous studies have confirmed the carcinogenic role of HMGN5 in cancer, but its function in the regulation of chemosensitivity is largely unknown and controversial. A previous study by the authors of the present study demonstrated that HMGN5 contributes to the progression of urothelial bladder cancer (UBC) through regulating the expression of E-cadherin and vascular endothelial growth factor (VEGF)-C, which are associated with the sensitivity of tumor cells to cisplatin. Therefore, the present study aimed to elucidate the mechanisms underlying the regulation of HMGN5 and investigate the involvement of HMGN5 in cisplatin treatment. The results of the present study revealed that HMGN5 is able to positively regulate the expression of phosphorylated (p-)Akt in UBC cells. In addition, HMGN5 expression was negatively associated with the response of UBC cells to cisplatin. The findings indicated that HMGN5 may be a potential therapeutic target of cisplatin treatment, since cisplatin treatment reduced HMGN5 expression in a dose-dependent manner. It was also confirmed that the knockdown of HMGN5 decreased the viability, colony formation and invasion of 5637 cells but increased apoptosis under cisplatin treatment. The changes caused by HMGN5 knockdown in 5637 cells were able to be reversed by treatment with insulin-like growth factor-1 (IGF-1), which is a phosphoinositide 3-kinase (PI3K)/Akt signaling activator. Additionally, with the decreased expression of HMGN5, the expression of p-Akt, slug, E-cadherin and VEGF-C was subsequently inhibited. By contrast, the expression of cytochrome c, cleaved-caspase-3 and cleaved-poly ADP ribose polymerase was increased following HMGN5 knockdown. Consistently, these changes in protein expression were able to be reversed by IGF-1 treatment. In conclusion, findings from the in vitro experiments indicate that HMGN5 may a target of cisplatin treatment and that the inhibition of HMGN5 increases the chemosensitivity of UBC cells by inhibiting PI3K/Akt signaling.

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.

Progression-related loss of stromal Caveolin 1 levels fosters the growth of human PC3 xenografts and mediates radiation resistance

Despite good treatment results in localized prostate tumors, advanced disease stages usually have a pronounced resistance to chemotherapy and radiotherapy. The membrane protein caveolin-1 (Cav1) functions here as an important oncogene. Therefore we examined the impact of stromal Cav1 expression for tumor growth and sensitivity to ionizing radiation (IR). Silencing of Cav1 expression in PC3 cells resulted in increased tumor growth and a reduced growth delay after IR when compared to tumors generated by Cav1-expressing PC3 cells. The increased radiation resistance was associated with increasing amounts of reactive tumor stroma and a Cav1 re-expression in the malignant epithelial cells. Mimicking the human situation these results were confirmed using co-implantation of Cav1-silenced PC3 cells with Cav1-silenced or Cav1-expressing fibroblasts. Immunohistochemically analysis of irradiated tumors as well as human prostate tissue specimen confirmed that alterations in stromal-epithelial Cav1 expressions were accompanied by a more reactive Cav1-reduced tumor stroma after radiation and within advanced prostate cancer tissues which potentially mediates the resistance to radiation treatment. Conclusively, the radiation response of human prostate tumors is critically regulated by Cav1 expression in stromal fibroblasts. Loss of stromal Cav1 expression in advanced tumor stages may thus contribute to resistance of these tumors to radiotherapy.

Expression and potential correlation among Forkhead box protein M1, Caveolin-1 and E-cadherin in colorectal cancer

The aim of the present study was to investigate the expression and functions of Forkhead box protein M1 (FoxM1), Caveolin-1 (Cav-1) and E-cadherin in colorectal cancer (CRC), and to determine the correlations among these proteins in CRC development and progression. The protein expression of FoxM1, Cav-1 and E-cadherin was identified using a human CRC and normal tissue microarray. A standard immunohistochemistry assay was performed employing anti-FoxM1, anti-Cav-1 and anti-E-cadherin antibodies. The clinicopathological significance of FoxM1, Cav-1 and E-cadherin in CRC was determined, and correlations were investigated between FoxM1 and Cav-1, FoxM1 and E-cadherin, Cav-1 and E-cadherin, respectively. The level of FoxM1, Cav-1 and E-Cadherin protein expression in CRC was found to be associated with pathological grade, tumor clinical stages and the presence of metastasis, respectively. Elevated expression of FoxM1 and Cav-1 was observed in the CRC tissues, and a significant correlation was found between the two proteins in CRC. However, it was also observed that FoxM1 was overexpressed while E-cadherin expression was low, indicating that there was a negative correlation between FoxM1 expression and E-cadherin expression. Moreover, there was also a negative correlation between Cav-1 and E-cadherin expression. Overall, the elevated expression of FoxM1 and Cav-1 in a human CRC microarray provided novel clinical evidence to elucidate the fact that they may play a critical role in the development and progression of CRC by negatively regulating E-cadherin expression. Furthermore, the positive correlation between FoxM1 and Cav-1 suggested that the proteins may constitute a novel signaling pathway in human CRC.

Mechanosensitive caveolin-1 activation-induced PI3K/Akt/mTOR signaling pathway promotes breast cancer motility, invadopodia formation and metastasis in vivo

Cancer cells are subjected to fluid shear stress during passage through the venous and lymphatic system. Caveolin-1 (Cav-1), a principal structural component of caveolar membrane domains, contributes to cancer development but its mechanobiological roles under low shear stress (LSS) conditions remain largely unknown. Here, we identified Cav-1 is mechanosensitive to LSS exposure, and its activation-induced PI3K/Akt/mTOR signaling promotes motility, invadopodia formation and metastasis of breast carcinoma MDA-MB-231 cells. Application of LSS (1.8 and 4.0 dynes/cm2) to MDA-MB-231 cells significantly increased the cell motility, invadopodia formation, MT1-MMP expression, ECM degradation, and also induced a sustained activation of Cav-1 and PI3K/Akt/mTOR signaling cascades. Methyl-β-cyclodextrin-caused caveolae destruction markedly decreased LSS-induced activation of both Cav-1 and PI3K/Akt/mTOR, leading to suppress MT1-MMP expression, inhibit invadopodia formation and ECM degradation, suggesting that caveolae integrity also involved in metastasis. Immunocytochemical assay showed that LSS induces the Cav-1 clustering in lipid rafts and co-localization of Cav-1 and MT1-MMP on invadopodia. Immunofluorescence confocal analysis demonstrated that Cav-1 activation were required for the acquisition of a polarized phenotype in MDA-MB-231 cells. Finally, Cav-1 knockdown significantly suppressed tumor colonization in the lungs and distant metastases in animal models. Our findings highlight the importance of Cav-1 in hematogenous metastasis, and provide new insights into the underlying mechanisms of mechanotransduction induced by LSS.

β-Carotene Induces Apoptosis in Human Esophageal Squamous Cell Carcinoma Cell Lines via the Cav-1/AKT/NF-κB Signaling Pathway

β-carotene, a type of terpenoid, has many metabolic and physiological functions. In particular, β-carotene has an antitumor effect. However, the efficacy of β-carotene against esophageal squamous cell carcinoma (ESCC) remains unclear. In our study, β-carotene inhibited the growth of ESCC cells and downregulated expression of the Caveolin-1 (Cav-1) protein. Cav-1 protein was expressed only in ESCC cells, not in Het-1A cells. Moreover, β-carotene triggered apoptosis, induced cell cycle G0⁄G1 phase arrest, and inhibited cell migration. To explore the mechanism involved in these processes, we further examined the effect of β-carotene on the Cav-1-mediated AKT/NF-κB pathway. The results showed that the level of AKT and NF-κB phosphorylation was dramatically inhibited, which led to an increase in the Bax/Bcl-2 ratio. Correspondingly, the activity of Caspase-3 was also enhanced. These data suggest that β-carotene has an antiproliferative role in ESCC cells and may be a promising chemotherapeutic agent for use against ESCC cells.

Emerging roles of sumoylation in the regulation of actin, microtubules, intermediate filaments, and septins

Sumoylation is a powerful regulatory system that controls many of the critical processes in the cell, including DNA repair, transcriptional regulation, nuclear transport, and DNA replication. Recently, new functions for SUMO have begun to emerge. SUMO is covalently attached to components of each of the four major cytoskeletal networks, including microtubule-associated proteins, septins, and intermediate filaments, in addition to nuclear actin and actin-regulatory proteins. However, knowledge of the mechanisms by which this signal transduction system controls the cytoskeleton is still in its infancy. One story that is beginning to unfold is that SUMO may regulate the microtubule motor protein dynein by modification of its adaptor Lis1. In other instances, cytoskeletal elements can both bind to SUMO non-covalently and also be conjugated by it. The molecular mechanisms for many of these new functions are not yet clear, but are under active investigation. One emerging model links the function of MAP sumoylation to protein degradation through SUMO-targeted ubiquitin ligases, also known as STUbL enzymes. Other possible functions for cytoskeletal sumoylation are also discussed.