Caveolin-1-mediated suppression of cyclooxygenase-2 via a beta-catenin-Tcf/Lef-dependent transcriptional mechanism reduced prostaglandin E2 production and survivin expression

Arachidonic acid metabolism as a novel pathogenic factor in gastrointestinal cancers

Gastrointestinal (GI) cancers are a major global health burden, representing 20% of all cancer diagnoses and 22.5% of global cancer-related deaths. Their aggressive nature and resistance to treatment pose a significant challenge, with late-stage survival rates below 15% at five years. Therefore, there is an urgent need to delve deeper into the mechanisms of gastrointestinal cancer progression and optimize treatment strategies. Increasing evidence highlights the active involvement of abnormal arachidonic acid (AA) metabolism in various cancers. AA is a fatty acid mainly metabolized into diverse bioactive compounds by three enzymes: cyclooxygenase, lipoxygenase, and cytochrome P450 enzymes. Abnormal AA metabolism and altered levels of its metabolites may play a pivotal role in the development of GI cancers. However, the underlying mechanisms remain unclear. This review highlights a unique perspective by focusing on the abnormal metabolism of AA and its involvement in GI cancers. We summarize the latest advancements in understanding AA metabolism in GI cancers, outlining changes in AA levels and their potential role in liver, colorectal, pancreatic, esophageal, gastric, and gallbladder cancers. Moreover, we also explore the potential of targeting abnormal AA metabolism for future therapies, considering the current need to explore AA metabolism in GI cancers and outlining promising avenues for further research. Ultimately, such investigations aim to improve treatment options for patients with GI cancers and pave the way for better cancer management in this area.

Phenotypic Heterogeneity, Bidirectionality, Universal Cues, Plasticity, Mechanics, and the Tumor Microenvironment Drive Cancer Metastasis

Tumor diseases become a huge problem when they embark on a path that advances to malignancy, such as the process of metastasis. Cancer metastasis has been thoroughly investigated from a biological perspective in the past, whereas it has still been less explored from a physical perspective. Until now, the intraluminal pathway of cancer metastasis has received the most attention, while the interaction of cancer cells with macrophages has received little attention. Apart from the biochemical characteristics, tumor treatments also rely on the tumor microenvironment, which is recognized to be immunosuppressive and, as has recently been found, mechanically stimulates cancer cells and thus alters their functions. The review article highlights the interaction of cancer cells with other cells in the vascular metastatic route and discusses the impact of this intercellular interplay on the mechanical characteristics and subsequently on the functionality of cancer cells. For instance, macrophages can guide cancer cells on their intravascular route of cancer metastasis, whereby they can help to circumvent the adverse conditions within blood or lymphatic vessels. Macrophages induce microchannel tunneling that can possibly avoid mechanical forces during extra- and intravasation and reduce the forces within the vascular lumen due to vascular flow. The review article highlights the vascular route of cancer metastasis and discusses the key players in this traditional route. Moreover, the effects of flows during the process of metastasis are presented, and the effects of the microenvironment, such as mechanical influences, are characterized. Finally, the increased knowledge of cancer metastasis opens up new perspectives for cancer treatment.

Prostaglandin E2 Exposure Disrupts E-Cadherin/Caveolin-1-Mediated Tumor Suppression to Favor Caveolin-1-Enhanced Migration, Invasion, and Metastasis in Melanoma Models

Caveolin-1 (CAV1) is a membrane-bound protein that suppresses tumor development yet also promotes metastasis. E-cadherin is important in CAV1-dependent tumor suppression and prevents CAV1-enhanced lung metastasis. Here, we used murine B16F10 and human A375 melanoma cells with low levels of endogenous CAV1 and E-cadherin to unravel how co-expression of E-cadherin modulates CAV1 function in vitro and in vivo in WT C57BL/6 or Rag-/- immunodeficient mice and how a pro-inflammatory environment generated by treating cells with prostaglandin E2 (PGE2) alters CAV1 function in the presence of E-cadherin. CAV1 expression augmented migration, invasion, and metastasis of melanoma cells, and these effects were abolished via transient co-expression of E-cadherin. Importantly, exposure of cells to PGE2 reverted the effects of E-cadherin expression and increased CAV1 phosphorylation on tyrosine-14 and metastasis. Moreover, PGE2 administration blocked the ability of the CAV1/E-cadherin complex to prevent tumor formation. Therefore, our results support the notion that PGE2 can override the tumor suppressor potential of the E-cadherin/CAV1 complex and that CAV1 released from the complex is phosphorylated on tyrosine-14 and promotes migration/invasion/metastasis. These observations provide direct evidence showing how a pro-inflammatory environment caused here via PGE2 administration can convert a potent tumor suppressor complex into a promoter of malignant cell behavior.

CAV1 Impacts the Tumor Immune Microenvironment and Has Potential Value of Predicting Response to Immunotherapy in Esophageal Cancer

Caveolin-1 (CAV1) is one of the members of the caveolae, and the role of CAV1 in esophageal cancer (ESCA) is not completely clear. In this study, we found that expression of CAV1 was downregulated in ESCA in The Cancer Genome Atlas and the Genotype-Tissue Expression (GTEx) database and we also use immunohistochemistry of tissue microarray for verification. Then, we used bioinformatics methods to investigate the prognostic value of CAV1, influence on immune cell infiltration in tumor microenvironment (TME) and responding to immunotherapy in ESCA. Our result indicated that CAV1 designs an inflamed TME in ESCA based on the evidence that CAV1 positively correlated with immunomodulators, immune score, stomal score, cancer immunity cycles, tumor-infiltrating immune cells, T cell inflamed score, and immune checkpoints. Immunophenoscore, Tumor Immune Dysfunction and Exclusion algorithms, and the mutation analysis show that the downregulated CAV1 expression indicated higher tumor mutation burden and higher rate of response to immune checkpoint inhibitors (ICIs) in the low-expression group. In a word, our study demonstrated the impact of CAV1 to the TME in ESCA and it may be a new target for ESCA immunotherapy. In addition, the expression of CAV1 can predict the clinical response to ICIs, which may provide clinical treatment guidance.

Systems biology network reveals the correlation between COX-2 expression and Ch 7q copy number alterations in Ch 11q-deleted pediatric neuroblastoma tumors

Tumor-associated inflammation and chromosomal aberrations can play crucial roles in cancer development and progression. In neuroblastoma (NB), the enzyme cyclooxygenase-2 (COX-2) is associated with copy number alterations on the long arm of chromosome 11 (Ch 11q), defining an aggressive disease subset. This retrospective study included formalin-fixed paraffin-embedded tumor samples collected from nine patients during diagnosis at the pediatric Pequeno Principe Hospital, Curitiba, PR, Brazil, and post-chemotherapy (CT). COX-2 expression was evaluated using immunohistochemistry and correlated with the genome profile of paired pre- and post-CT samples, determined by array comparative genomic hybridization. A systems biology approach elucidated the PTGS2 network interaction. The results showed positive correlations between pre-CT Ch 7q gain and COX-2 expression (ρ = 0.825; p-value = 0.006) and negative correlations between Ch 7q gain and Ch 11q deletion (ρ = −0.919; p-value = 0.0005). Three samples showed Ch 11q deletion and Ch 7q gain. Network analysis identified a direct connection between CAV-1 (Ch 7q) and COX-2 in NB tumors and highlighted the connection between amplified genes in Ch 7q and deleted ones in 11q. The identification of hub-bottleneck-switch genes provides new biological insights into this connection between NB, tumorigenesis, and inflammation.

Pharmacological Activation of Potassium Channel Kv11.1 with NS1643 Attenuates Triple Negative Breast Cancer Cell Migration by Promoting the Dephosphorylation of Caveolin-1

The prevention of metastasis is a central goal of cancer therapy. Caveolin-1 (Cav-1) is a structural membrane and scaffolding protein shown to be a key regulator of late-stage breast cancer metastasis. However, therapeutic strategies targeting Cav-1 are still lacking. Here, we demonstrate that the pharmacological activation of potassium channel Kv11.1, which is uniquely expressed in MDA-MB-231 triple negative breast cancer cells (TNBCs) but not in normal MCF-10A cells, induces the dephosphorylation of Cav-1 Tyr-14 by promoting the Ca2+-dependent stimulation of protein tyrosine phosphatase 1B (PTP1B). Consequently, the dephosphorylation of Cav-1 resulted in its disassociation from β-catenin, which enabled the accumulation of β-catenin at cell borders, where it facilitated the formation of cell-cell adhesion complexes via interactions with R-cadherin and desmosomal proteins. Kv11.1 activation-dependent Cav-1 dephosphorylation induced with NS1643 also reduced cell migration and invasion, consistent with its ability to regulate focal adhesion dynamics. Thus, this study sheds light on a novel pharmacological mechanism of promoting Cav-1 dephosphorylation, which may prove to be effective at reducing metastasis and promoting contact inhibition.

Prognostic significance and therapeutic implications of Caveolin-1 in gastrointestinal tract malignancies

Caveolin-1 (CAV1) is expressed in several solid tumors both in cancerous cells as well as in tumor stroma and is reported to be related to cancer progression, metastasis, therapy resistance and clinical outcomes. Many studies report contrasting functions of this protein depending on the tumor cell model, the tumor type, or the stage of cancer studied. This protein is reported to function both as tumor suppressor and as tumor promoter. In this review, we aim to summarize translational and clinical studies that provide evidence of the role of CAV1 in tumor progression and survival outcome focusing on tumors of the gastrointestinal (GI) tract. Towards this aim, a detailed search has been performed for studies on the expression and the role of CAV1 in oesophageal, gastric, colorectal, pancreatic cancer and cholangiocarcinoma prognosis. We also review and discuss the implication of CAV1 in the outcome of pharmacological interventions. We conclude that CAV1 has the potential to become an important prognostic, and possibly predictive, biomarker in GI malignancies. It may also become a novel target towards the development of improved cancer therapies. However, it is obvious that there remains a lack of consensus on important issues such as the methodologies and cut-off levels in caveolin assessment. This ultimately result in many studies being contradictory not only in terms of the role of CAV1 as a tumor-promoting or suppressing gene but also in terms of the tumor compartment in which the levels of this protein may be of clinical significance. Addressing these important technical issues, in conjunction with a further elucidation of the role of CAV1 in tumor formation and progression, will delineate the importance of CAV1 in prognostic and therapeutic perspectives.

Caveolin-1 function at the plasma membrane and in intracellular compartments in cancer

Caveolin-1 (CAV1) is commonly considered to function as a cell surface protein, for instance in the genesis of caveolae. Nonetheless, it is also present in many intracellular organelles and compartments. The contributions of these intracellular pools to CAV1 function are generally less well understood, and this is also the case in the context of cancer. This review will summarize literature available on the role of CAV1 in cancer, highlighting particularly our understanding of the canonical (CAV1 in the plasma membrane) and non-canonical pathways (CAV1 in organelles and exosomes) linked to the dual role of the protein as a tumor suppressor and promoter of metastasis. With this in mind, we will focus on recently emerging concepts linking CAV1 function to the regulation of intracellular organelle communication within the same cell where CAV1 is expressed. However, we now know that CAV1 can be released from cells in exosomes and generate systemic effects. Thus, we will also elaborate on how CAV1 participates in intracellular communication between organelles as well as signaling between cells (non-canonical pathways) in cancer.

Primer on the Pathogenesis of Severe COVID-19: Part Two

In the following continuation article, the author will expand on how the mechanisms discussed in Part One capitalise on host characteristics to produce the organ specific damage seen in severe coronavirus disease (COVID-19), with specific reference to pulmonary and cardiac manifestations. Pneumonia is the primary manifestation of COVID-19; presentation varies from a mild, self-limiting pneumonitis to a fulminant and progressive respiratory failure. Features of disease severity tend to directly correlate with patient age, with elderly populations faring poorest. Advancing age parallels an increasingly pro-oxidative pulmonary milieu, a consequence of increasing host expression of phospholipase A2 Group IID. Virally induced expression of NADPH oxidase intensifies this pro-oxidant environment. The virus avails of the host response by exploiting caveolin-1 to assist in disabling host defenses and adopting a glycolytic metabolic pathway to self-replicate.

Acoustic Waves in Axonal Membrane and Caveolins are the New Targets for Pain Treatment with High Frequency Ultrasound

Reciprocal interaction between electrical and mechanical waves observed in axonal membrane during its excitation leads to a paradigm shift in pain research making the uncoupling of electro-mechanical signals an interesting target in pain treatment. This uncoupling can be realized either through direct disturbance of the mechanical surface waves in axonal membrane or through shifting of the thermodynamic state of this membrane far from its phase transition point. Both effects can be effectively realized through application of the very high frequency ultrasound waves. Additional target for application of ultrasound in pain treatment is the caveolin-1, which is abundantly present in Schwann cells as well as in the non-axonal tissues. Both targets demonstrate frequency-dependent reactions, thus making a very high frequency ultrasound a promising treatment modality in pain treatment.

Metformin Reduces NGF-Induced Tumour Promoter Effects in Epithelial Ovarian Cancer Cells

Epithelial ovarian cancer (EOC) is a lethal gynaecological neoplasm characterized by rapid growth and angiogenesis. Nerve growth factor (NGF) and its high affinity receptor tropomyosin receptor kinase A (TRKA) contribute to EOC progression by increasing the expression of c-MYC, survivin and vascular endothelial growth factor (VEGF) along with a decrease in microRNAs (miR) 23b and 145. We previously reported that metformin prevents NGF-induced proliferation and angiogenic potential of EOC cells. In this study, we sought to obtain a better understanding of the mechanism(s) by which metformin blocks these NGF-induced effects in EOC cells. Human ovarian surface epithelial (HOSE) and EOC (A2780/SKOV3) cells were stimulated with NGF and/or metformin to assess the expression of c-MYC, β-catenin, survivin and VEGF and the abundance of the tumor suppressor miRs 23b and 145. Metformin decreased the NGF-induced transcriptional activity of MYC and β-catenin/T-cell factor/lymphoid enhancer-binding factor (TCF-Lef), as well as the expression of c-MYC, survivin and VEGF in EOC cells, while it increased miR-23b and miR-145 levels. The preliminary analysis of ovarian biopsies from women users or non-users of metformin was consistent with these in vitro results. Our observations shed light on the mechanisms by which metformin may suppress tumour growth in EOC and suggest that metformin should be considered as a possible complementary therapy in EOC treatment.

NGF/TRKA Decrease miR-145-5p Levels in Epithelial Ovarian Cancer Cells

Nerve Growth Factor (NGF) and its high-affinity receptor tropomyosin receptor kinase A (TRKA) increase their expression during the progression of epithelial ovarian cancer (EOC), promoting cell proliferation and angiogenesis through several oncogenic proteins, such as c-MYC and vascular endothelial growth factor (VEGF). The expression of these proteins is controlled by microRNAs (miRs), such as miR-145, whose dysregulation has been related to cancer. The aims of this work were to evaluate in EOC cells whether NGF/TRKA decreases miR-145 levels, and the effect of miR-145 upregulation. The levels of miR-145-5p were assessed by qPCR in ovarian biopsies and ovarian cell lines (human ovarian surface epithelial cells (HOSE), A2780 and SKOV3) stimulated with NGF. Overexpression of miR-145 in ovarian cells was used to evaluate cell proliferation, migration, invasion, c-MYC and VEGF protein levels, as well as tumor formation and metastasis in vivo. In EOC samples, miR-145-5p levels were lower than in epithelial ovarian tumors. Overexpression of miR-145 decreased cell proliferation, migration and invasion of EOC cells, changes that were concomitant with the decrease in c-MYC and VEGF protein levels. We observed decreased tumor formation and suppressed metastasis behavior in mice injected with EOC cells that overexpressed miR-145. As expected, ovarian cell lines stimulated with NGF diminished miR-145-5p transcription and abundance. These results suggest that the tumoral effects of NGF/TRKA depend on the regulation of miR-145-5p levels in EOC cells, and that its upregulation could be used as a possible therapeutic strategy for EOC.

Caveolin-1-Mediated Tumor Suppression Is Linked to Reduced HIF1α S-Nitrosylation and Transcriptional Activity in Hypoxia

Caveolin-1 (CAV1) is a well-established nitric oxide synthase inhibitor, whose function as a tumor suppressor is favored by, but not entirely dependent on, the presence of E-cadherin. Tumors are frequently hypoxic and the activation of the hypoxia-inducible factor-1α (HIF1α) promotes tumor growth. HIF1α is regulated by several post-translational modifications, including S-nitrosylation. Here, we evaluate the mechanisms underlying tumor suppression by CAV1 in cancer cells lacking E-cadherin in hypoxia. Our main findings are that CAV1 reduced HIF activity and Vascular Endothelial Growth Factor expression in vitro and in vivo. This effect was neither due to reduced HIF1α protein stability or reduced nuclear translocation. Instead, HIF1α S-nitrosylation observed in hypoxia was diminished by the presence of CAV1, and nitric oxide synthase (NOS) inhibition by Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) reduced HIF1α transcriptional activity in cells to the same extent as observed upon CAV1 expression. Additionally, arginase inhibition by (S)-(2-Boronoethyl)-L-cysteine (BEC) partially rescued cells from the CAV1-mediated suppression of HIF1α transcriptional activity. In vivo, CAV1-mediated tumor suppression was dependent on NOS activity. In summary, CAV1-dependent tumor suppression in the absence of E-cadherin is linked to reduced HIF1α transcriptional activity via diminished NOS-mediated HIF1α S-nitrosylation.

Caveolin-1 suppresses tumor formation through the inhibition of the unfolded protein response

Caveolin-1 (CAV1), is a broadly expressed, membrane-associated scaffolding protein that acts both, as a tumor suppressor and a promoter of metastasis, depending on the type of cancer and stage. CAV1 is downregulated in human tumors, tumor cell lines and oncogene-transformed cells. The tumor suppressor activity of CAV1 is generally associated with its presence at the plasma membrane, where it participates, together with cavins, in the formation of caveolae and also has been suggested to interact with and inhibit a wide variety of proteins through interactions mediated by the scaffolding domain. However, a pool of CAV1 is also located at the endoplasmic reticulum (ER), modulating the secretory pathway in a manner dependent on serine-80 (S80) phosphorylation. In melanoma cells, CAV1 expression suppresses tumor formation, but the protein is largely absent from the plasma membrane and does not form caveolae. Perturbations to the function of the ER are emerging as a central driver of cancer, highlighting the activation of the unfolded protein response (UPR), a central pathway involved in stress mitigation. Here we provide evidence indicating that the expression of CAV1 represses the activation of the UPR in vitro and in solid tumors, reflected in the attenuation of PERK and IRE1α signaling. These effects correlated with increased susceptibility of cells to ER stress and hypoxia. Interestingly, the tumor suppressor activity of CAV1 was abrogated by site-directed mutagenesis of S80, correlating with a reduced ability to repress the UPR. We conclude that the tumor suppression by CAV1 involves the attenuation of the UPR, and identified S80 as essential in this context. This suggests that intracellular CAV1 regulates cancer through alternative signaling outputs.

The non-receptor tyrosine phosphatase type 14 blocks caveolin-1-enhanced cancer cell metastasis

Caveolin-1 (CAV1) enhanced migration, invasion, and metastasis of cancer cells is inhibited by co-expression of the glycoprotein E-cadherin. Although the two proteins form a multiprotein complex that includes β-catenin, it remained unclear how this would contribute to blocking the metastasis promoting function of CAV1. Here, we characterized by mass spectrometry the protein composition of CAV1 immunoprecipitates from B16F10 murine melanoma cells expressing or not E-cadherin. The novel protein tyrosine phosphatase PTPN14 was identified by mass spectrometry analysis exclusively in co-immunoprecipitates of CAV1 with E-cadherin. Interestingly, PTPN14 is implicated in controlling metastasis, but only few known PTPN14 substrates exist. We corroborated by western blotting experiments that PTPN14 and CAV1 co-inmunoprecipitated in the presence of E-cadherin in B16F10 melanoma and other cancer cells. Moreover, the CAV1(Y14F) mutant protein was shown to co-immunoprecipitate with PTPN14 even in the absence of E-cadherin, and overexpression of PTPN14 reduced CAV1 phosphorylation on tyrosine-14, as well as suppressed CAV1-enhanced cell migration, invasion and Rac-1 activation in B16F10, metastatic colon [HT29(US)] and breast cancer (MDA-MB-231) cell lines. Finally, PTPN14 overexpression in B16F10 cells reduced the ability of CAV1 to induce metastasis in vivo. In summary, we identify here CAV1 as a novel substrate for PTPN14 and show that overexpression of this phosphatase suffices to reduce CAV1-induced metastasis.

NGF-Enhanced Vasculogenic Properties of Epithelial Ovarian Cancer Cells Is Reduced by Inhibition of the COX-2/PGE2 Signaling Axis

Epithelial ovarian cancer (EOC) is a lethal gynecological neoplasia characterized by extensive angiogenesis and overexpression of nerve growth factor (NGF). Here, we investigated the mechanism by which NGF increases vascular endothelial growth factor (VEGF) expression and the vasculogenic potential of EOC cells, as well as the contribution of the cyclooxygenase 2/prostaglandin E₂ (COX-2/PGE₂) signaling axis to these events. EOC biopsies and ovarian cell lines were used to determine COX-2 and PGE₂ levels, as well as those of the potentially pro-angiogenic proteins c-MYC (a member of the Myc transcription factors family), survivin, and β-catenin. We observed that COX-2 and survivin protein levels increased during EOC progression. In the EOC cell lines, NGF increased the COX-2 and PGE₂ levels. In addition, NGF increased survivin, c-MYC, and VEGF protein levels, as well as the transcriptional activity of c-MYC and β-catenin/T-cell factor/lymphoid enhancer-binding factor (TCF-Lef) in a Tropomyosin receptor kinase A (TRKA)-dependent manner. Also, COX-2 inhibition prevented the NGF-induced increases in these proteins and reduced the angiogenic score of endothelial cells stimulated with conditioned media from EOC cells. In summary, we show here that the pro-angiogenic effect of NGF in EOC depends on the COX-2/PGE2 signaling axis. Thus, inhibition COX-2/PGE2 signaling will likely be beneficial in the treatment of EOC.

Cell Intrinsic and Extrinsic Mechanisms of Caveolin-1-Enhanced Metastasis

Caveolin-1 (CAV1) is a scaffolding protein with a controversial role in cancer. This review will initially discuss earlier studies focused on the role as a tumor suppressor before elaborating subsequently on those relating to function of the protein as a promoter of metastasis. Different mechanisms are summarized illustrating how CAV1 promotes such traits upon expression in cancer cells (intrinsic mechanisms). More recently, it has become apparent that CAV1 is also a secreted protein that can be included into exosomes where it plays a significant role in determining cargo composition. Thus, we will also discuss how CAV1 containing exosomes from metastatic cells promote malignant traits in more benign recipient cells (extrinsic mechanisms). This ability appears, at least in part, attributable to the transfer of specific cargos present due to CAV1 rather than the transfer of CAV1 itself. The evolution of how our perception of CAV1 function has changed since its discovery is summarized graphically in a time line figure.

Gold nanoparticles as tracking devices to shed light on the role of caveolin-1 in early stages of melanoma metastasis

AIM

To track early events during lung metastasis, we labeled cells expressing (B16F10_CAV1) or lacking CAV1 (B16F10_mock) with gold nanoparticles conjugated to the peptide TAT (AuNPs-PEG-TAT).

METHODS

B16F10 expressing or lacking CAV1 were labeled with AuNPs-PEG-TAT. The physicochemical properties and cytotoxicity of these nanoparticles, as well as their effects on migration and invasiveness of B16F10 cells in vitro were evaluated. Ex vivo lung distribution of the labeled cells after tail vein injection into C57BL/6 mice was examined.

RESULTS

AuNPs-PEG-TAT did not affect B16F10 viability, migration and invasiveness. The metastatic and tumorigenic capability of the labeled B16F10 was also not modified in comparison to unlabeled B16F10 cells. CAV1 expression favored the retention of B16F10 cells in the lungs of mice 2 h post injection, suggesting CAV1 promoted adherence to endothelial cells and transendothelial migration.

CONCLUSIONS

We developed a protocol to label B16F10 cells with AuNPs-PEG-TAT that permits subsequent tracking of cells in mice. CAV1 overexpression was found to increase retention and transendothelial migration of B16F10 cells in the lung.

The regulation of host cellular and gut microbial metabolism in the development and prevention of colorectal cancer

Metabolism regulation is crucial in colorectal cancer (CRC) and has emerged as a remarkable field currently. The cellular metabolism of glucose, amino acids and lipids in CRC are all reprogrammed. Each of them changes tumour microenvironment, modulates bacterial composition and activity, and eventually promotes CRC development. Metabolites such as short chain fatty acids, secondary bile acids, N-nitroso compounds, hydrogen sulphide, polyphenols and toxins like fragilysin, FadA, cytolethal distending toxin and colibactin play a dual role in CRC. The relationship of gut microbe-metabolite is essential in remodelling intestinal microbial ecology composition and metabolic activity. It regulates the metabolism of colonic epithelial cells and changes the tumour microenvironment in CRC. Microbial metabolism manipulation has been considered to be potentially preventive in CRC, but more large-scale clinical trials are required before their application in clinical practice in the near future.

One-step self-assembled nanomicelles for improving the oral bioavailability of nimodipine

Our study aimed to develop a self-assembled nanomicelle for oral administration of nimodipine (NIM) with poor water solubility. Using Solutol(®) HS15, the NIM-loaded self-assembled nanomicelles displayed a near-spherical morphology with a narrow size distribution of 12.57 ± 0.21 nm (polydispersity index =0.071 ± 0.011). Compared with Nimotop(®) (NIM tablets), the intestinal absorption of NIM from NIM nanomicelle in rats was improved by 3.13- and 2.25-fold in duodenum and jejunum at 1 hour after oral administration. The cellular transport of NIM nanomicelle in Caco-2 cell monolayers was significantly enhanced compared to that of Nimotop(®). Regarding the transport pathways, clathrin, lipid raft/caveolae, and macropinocytosis mediated the cell uptake of NIM nanomicelles, while P-glycoprotein and endoplasmic reticulum/Golgi complex (ER/Golgi) pathways were involved in exocytosis. Pharmacokinetic studies in our research laboratory have showed that the area under the plasma concentration-time curve (AUC0-∞) of NIM nanomicelles was 3.72-fold that of Nimotop(®) via oral administration in rats. Moreover, the NIM concentration in the brain from NIM nanomicelles was dramatically improved. Therefore, Solutol(®) HS15-based self-assembled nanomicelles represent a promising delivery system to enhance the oral bioavailability of NIM.

Dehydroleucodine inhibits tumor growth in a preclinical melanoma model by inducing cell cycle arrest, senescence and apoptosis

Malignant melanoma represents the fastest growing public health risk of all cancer types worldwide. Several strategies and anti-cancer drugs have been used in an effort to improve treatments, but the development of resistance to anti-neoplastic drugs remains the major cause of chemotherapy failure in melanomas. Previously, we showed that the sesquiterpene lactone, dehydroleucodine (DhL), promotes the accumulation of DNA damage markers, such as H2AX and 53BP1, in human tumor cells. Also DhL was shown to trigger either cell senescence or apoptosis in a concentration-dependent manner in HeLa and MCF7 cells. Here, we evaluated the effects of DhL on B16F0 mouse melanoma cells in vitro and in a pre-clinical melanoma model. DhL inhibited the proliferation of B16F0 cells by inducing senescence or apoptosis in a concentration-dependent manner. Also, DhL reduced the expression of the cell cycle proteins cyclin D1 and B1 and the inhibitor of apoptosis protein, survivin. In melanomas generated by subcutaneous injection of B16F0 cells into C57/BL6 mice, the treatment with 20 mg DhL /Kg/day in preventive, simultaneous and therapeutic protocols reduced tumor volumes by 70%, 60% and 50%, respectively. DhL treatments reduced the number of proliferating, while increasing the number of senescent and apoptotic tumor cells. To estimate the long-term effects of DhL, a mathematical model was applied to fit experimental data. Extrapolation beyond experimental time points revealed that DhL administration following preventive and therapeutic protocols is predicted to be more effective than simultaneous treatments with DhL in restricting tumor growth.

High-mobility group box 1 enhances the inflammatory process in diabetic lung

Diabetes mellitus generates metabolic changes associated with inflammatory events that may eventually affect all body tissues. Both high-mobility group box 1 (HMGB1) and β-catenin are active players in inflammation. The study aimed to determine whether HMGB1 modulates the β-catenin activity in supporting inflammation, using an experimental type 1 diabetes mouse model. The protein and gene expression of HMGB1 were significantly increased (2-fold) in the diabetic lung compared to control and were positively correlated with the HMGB1 levels detected in serum. Co-immunoprecipitation of HMGB1 with RAGE co-exists with activation of PI3K/AKT1 and NF-kB signaling pathways. At the same time β-catenin was increased in nuclear fraction (3.5 fold) while it was down-regulated in diabetic plasma membrane (2-fold). There was no difference of β-catenin gene expression between the control and diabetic mice. β-Catenin phosphorylation at Ser552 was higher in diabetic nuclear fraction, suggesting that AKT1 activation promotes β-catenin nuclear translocation. In addition, c-Jun directly binds β-catenin indicating the transcriptional activity of β-catenin in diabetes, sustained by significantly COX2 increase by 6-fold in the cytosolic extract of diabetic lung compared to control. Taken together, the data support the new concept that HMGB1 maintains the inflammation through RAGE/AKT1/β-catenin pathway in the diabetic lung.

Caveolin and cavin family members: dual roles in cancer

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

Survivin expression promotes VEGF-induced tumor angiogenesis via PI3K/Akt enhanced β-catenin/Tcf-Lef dependent transcription

Early in cancer development, tumour cells express vascular endothelial growth factor (VEGF), a secreted molecule that is important in all stages of angiogenesis, an essential process that provides nutrients and oxygen to the nascent tumor and thereby enhances tumor-cell survival and facilitates growth. Survivin, another protein involved in angiogenesis, is strongly expressed in most human cancers, where it promotes tumor survival by reducing apoptosis as well as favoring endothelial cell proliferation and migration. The mechanisms by which cancer cells induce VEGF expression and angiogenesis upon survivin up-regulation remain to be fully established. Since the PI3K/Akt signalling and β-catenin-Tcf/Lef dependent transcription have been implicated in the expression of many cancer-related genes, including survivin and VEGF, we evaluated whether survivin may favor VEGF expression, release from tumor cells and induction of angiogenesis in a PI3K/Akt-β-catenin-Tcf/Lef-dependent manner. Here, we provide evidence linking survivin expression in tumor cells to increased β-catenin protein levels, β-catenin-Tcf/Lef transcriptional activity and expression of several target genes of this pathway, including survivin and VEGF, which accumulates in the culture medium. Alternatively, survivin downregulation reduced β-catenin protein levels and β-catenin-Tcf/Lef transcriptional activity. Also, using inhibitors of PI3K and the expression of dominant negative Akt, we show that survivin acts upstream in an amplification loop to promote VEGF expression. Moreover, survivin knock-down in B16F10 murine melanoma cells diminished the number of blood vessels and reduced VEGF expression in tumors formed in C57BL/6 mice. Finally, in the chick chorioallantoid membrane assay, survivin expression in tumor cells enhanced VEGF liberation and blood vessel formation. Importantly, the presence of neutralizing anti-VEGF antibodies precluded survivin-enhanced angiogenesis in this assay. These findings provide evidence for the existance of a posititve feedback loop connecting survivin expression in tumor cells to PI3K/Akt enhanced β-catenin-Tcf/Lef-dependent transcription followed by secretion of VEGF and angiogenesis.

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

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

Caveolin-1 limits human influenza A virus (H1N1) propagation in mouse embryo-derived fibroblasts

Caveolin expression supports the multiplication of retro-, ortho- and paramyxoviruses in susceptible cells. However, human influenza A virus (IAV), an orthomyxovirus, does not multiply efficiently in mouse embryo fibroblasts (MEFs), which are abundant in caveolin-1 (Cav-1). Surprisingly, the absence of Cav-1 in a MEF cell line removed the block for IAV replication and raised the infectious titer 250-fold, whereas the re-introduction of Cav-1 reversed the effect. The monitoring of cellular pathways revealed that Cav-1 loss considerably increased activities of p53. Furthermore, infection of MEF Cav-1 (-/-) induced reactive oxygen species (ROS) and pronounced apoptosis in the late phase of viral multiplication, but no type I IFN response. Strikingly, pharmacological inactivation showed that the elevated levels of ROS together with apoptosis caused the increase of virus yield. Thus, Cav-1 represents a new negative regulator of IAV infection in MEF that diminishes IAV infectious titer by controlling virus-supportive pathways.

Celecoxib decreases growth and angiogenesis and promotes apoptosis in a tumor cell line resistant to chemotherapy

BACKGROUND

During the last few years it has been shown in several laboratories that Celecoxib (Cx), a non-steroidal anti-inflammatory agent (NSAID) normally used for pain and arthritis, mediates antitumor and antiangiogenic effects. However, the effects of this drug on a tumor cell line resistant to chemotherapeutical drugs used in cancer have not been described.

RESULTS

Cx reduces angiogenesis in the chick embryonic chorioallantoic membrane assay (CAM), inhibits the growth and microvascular density of the murine TA3-MTXR tumor, reduces microvascular density of tumor metastases, promotes apoptosis and reduces vascular endothelial growth factor (VEGF) production and cell proliferation in the tumor.

CONCLUSION

The antiangiogenic and antitumor Cx effects correlate with its activity on other tumor cell lines, suggesting that Prostaglandins (PGs) and VEGF production are involved. These results open the possibility of using Celecoxib combined with other experimental therapies, ideally aiming to get synergic effects.

The hidden switches underlying RORα-mediated circuits that critically regulate uncontrolled cell proliferation

Prostaglandin E2 (PGE2) is known to have a key role in the development of colorectal cancer, but previous experiments showed its contrasting (i.e. tumor-promoting or tumor-suppressive) roles depending on experimental conditions. To elucidate the mechanisms underlying such contrasting roles of PGE2 in tumorigenesis, we investigated all the previous experiments and found a new signal transduction pathway mediated by retinoic acid receptor-related orphan receptor (ROR)α, in which PGE2/PKCα-dependent phosphorylation of RORα attenuates Wnt target gene expression in colon cancer cells. From mathematical simulations combined with biochemical experimentation, we revealed that RORα induces a biphasic response of Wnt target genes to PGE2 stimulation through a regulatory switch formed by an incoherent feedforward loop, which provides a mechanistic explanation on the contrasting roles of PGE2 observed in previous experiments. More interestingly, we found that RORα constitutes another regulatory switch formed by coupled positive and negative feedback loops, which regulates the hysteretic response of Wnt signaling and eventually converts a proliferative cellular state into an anti-proliferative state in a very delicate way. Our results indicate that RORα is the key regulator at the center of these hidden switches that critically regulate cancer cell proliferation and thereby being a promising anti-cancer therapeutic target.

Molecular profiles of parvalbumin-immunoreactive neurons in the superior temporal cortex in schizophrenia

Dysregulation of pyramidal cell network function by the soma- and axon-targeting inhibitory neurons that contain the calcium-binding protein parvalbumin (PV) represents a core pathophysiological feature of schizophrenia. In order to gain insight into the molecular basis of their functional impairment, we used laser capture microdissection (LCM) to isolate PV-immunolabeled neurons from layer 3 of Brodmann's area 42 of the superior temporal gyrus (STG) from postmortem schizophrenia and normal control brains. We then extracted ribonucleic acid (RNA) from these neurons and determined their messenger RNA (mRNA) expression profile using the Affymetrix platform of microarray technology. Seven hundred thirty-nine mRNA transcripts were found to be differentially expressed in PV neurons in subjects with schizophrenia, including genes associated with WNT (wingless-type), NOTCH, and PGE2 (prostaglandin E2) signaling, in addition to genes that regulate cell cycle and apoptosis. Of these 739 genes, only 89 (12%) were also differentially expressed in pyramidal neurons, as described in the accompanying paper, suggesting that the molecular pathophysiology of schizophrenia appears to be predominantly neuronal type specific. In addition, we identified 15 microRNAs (miRNAs) that were differentially expressed in schizophrenia; enrichment analysis of the predicted targets of these miRNAs included the signaling pathways found by microarray to be dysregulated in schizophrenia. Taken together, findings of this study provide a neurobiological framework within which hypotheses of the molecular mechanisms that underlie the dysfunction of PV neurons in schizophrenia can be generated and experimentally explored and, as such, may ultimately inform the conceptualization of rational targeted molecular intervention for this debilitating disorder.

Tumor suppression and promotion by autophagy

Autophagy is a highly regulated catabolic process that involves lysosomal degradation of proteins and organelles, mostly mitochondria, for the maintenance of cellular homeostasis and reduction of metabolic stress. Problems in the execution of this process are linked to different pathological conditions, such as neurodegeneration, aging, and cancer. Many of the proteins that regulate autophagy are either oncogenes or tumor suppressor proteins. Specifically, tumor suppressor genes that negatively regulate mTOR, such as PTEN, AMPK, LKB1, and TSC1/2 stimulate autophagy while, conversely, oncogenes that activate mTOR, such as class I PI3K, Ras, Rheb, and AKT, inhibit autophagy, suggesting that autophagy is a tumor suppressor mechanism. Consistent with this hypothesis, the inhibition of autophagy promotes oxidative stress, genomic instability, and tumorigenesis. Nevertheless, autophagy also functions as a cytoprotective mechanism under stress conditions, including hypoxia and nutrient starvation, that promotes tumor growth and resistance to chemotherapy in established tumors. Here, in this brief review, we will focus the discussion on this ambiguous role of autophagy in the development and progression of cancer.

Chondroprotective Activity of Murraya exotica through Inhibiting β -Catenin Signaling Pathway

Osteoarthritis (OA) is a degenerative joint disease that affects millions of people. Currently, there is no effective drug treatment for it. The purpose of this study is to investigate the chondroprotective effects of Murraya exotica (L.) on OA. The rat OA models were duplicated to prepare for separating OA chondrocytes, synovial fluid (SF), and serum containing M. exotica (50 mg/kg, 100 mg/kg, and 200 mg/kg), M. exotica showed the activity of decreasing the contents of TNF-α and IL-1β in SF and the chondrocyte apoptosis in a dose-dependent manner. To investigate the probable mechanism, quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to determine gene expression and protein profiles, respectively. The results reveal that M. exotica can downregulate mRNA and protein expressions of β-catenin and COX-2 and reporter activity significantly. Conclusively, M. exotica exhibits antiapoptotic chondroprotective activity probably through inhibiting β-catenin signaling.

The less-often-traveled surface of stem cells: caveolin-1 and caveolae in stem cells, tissue repair and regeneration

Stem cells are an important resource for tissue repair and regeneration. While a great deal of attention has focused on derivation and molecular regulation of stem cells, relatively little research has focused on how the subcellular structure and composition of the cell membrane influences stem cell activities such as proliferation, differentiation and homing. Caveolae are specialized membrane lipid rafts coated with caveolin scaffolding proteins, which can regulate cholesterol transport and the activity of cell signaling receptors and their downstream effectors. Caveolin-1 is involved in the regulation of many cellular processes, including growth, control of mitochondrial antioxidant levels, migration and senescence. These activities are of relevance to stem cell biology, and in this review evidence for caveolin-1 involvement in stem cell biology is summarized. Altered stem and progenitor cell populations in caveolin-1 null mice suggest that caveolin-1 can regulate stem cell proliferation, and in vitro studies with isolated stem cells suggest that caveolin-1 regulates stem cell differentiation. The available evidence leads us to hypothesize that caveolin-1 expression may stabilize the differentiated and undifferentiated stem cell phenotype, and transient downregulation of caveolin-1 expression may be required for transition between the two. Such regulation would probably be critical in regenerative applications of adult stem cells and during tissue regeneration. We also review here the temporal changes in caveolin-1 expression reported during tissue repair. Delayed muscle regeneration in transgenic mice overexpressing caveolin-1 as well as compromised cardiac, brain and liver tissue repair and delayed wound healing in caveolin-1 null mice suggest that caveolin-1 plays an important role in tissue repair, but that this role may be negative or positive depending on the tissue type and the nature of the repair process. Finally, we also discuss how caveolin-1 quiescence-inducing activities and effects on mitochondrial antioxidant levels may influence stem cell aging.

E-cadherin determines Caveolin-1 tumor suppression or metastasis enhancing function in melanoma cells

The role of caveolin-1 (CAV1) in cancer is highly controversial. CAV1 suppresses genes that favor tumor development, yet also promotes focal adhesion turnover and migration of metastatic cells. How these contrasting observations relate to CAV1 function in vivo is unclear. Our previous studies implicate E-cadherin in CAV1-dependent tumor suppression. Here, we use murine melanoma B16F10 cells, with low levels of endogenous CAV1 and E-cadherin, to unravel how CAV1 affects tumor growth and metastasis and to assess how co-expression of E-cadherin modulates CAV1 function in vivo in C57BL/6 mice. We find that overexpression of CAV1 in B16F10 (cav-1) cells reduces subcutaneous tumor formation, but enhances metastasis relative to control cells. Furthermore, E-cadherin expression in B16F10 (E-cad) cells reduces subcutaneous tumor formation and lung metastasis when intravenously injected. Importantly, co-expression of CAV1 and E-cadherin in B16F10 (cav-1/E-cad) cells abolishes tumor formation, lung metastasis, increased Rac-1 activity, and cell migration observed with B16F10 (cav-1) cells. Finally, consistent with the notion that CAV1 participates in switching human melanomas to a more malignant phenotype, elevated levels of CAV1 expression correlated with enhanced migration and Rac-1 activation in these cells.

Caveolin-1 regulates proliferation and osteogenic differentiation of human mesenchymal stem cells

Caveolin-1 is a scaffolding protein of cholesterol-rich caveolae lipid rafts in the plasma membrane. In addition to regulating cholesterol transport, caveolin-1 has the ability to bind a diverse array of cell signaling molecules and regulate cell signal transduction in caveolae. Currently, there is little known about the role of caveolin-1 in stem cells. It has been reported that the caveolin-1 null mouse has an expanded population of cells expressing stem cell markers in the gut, mammary gland, and brain, suggestive of a role for caveolin-1 in stem cell regulation. The caveolin-1 null mouse also has increased bone mass and an increased bone formation rate, and its bone marrow-derived mesenchymal stem cells (MSCs) have enhanced osteogenic potential. However, the role of caveolin-1 in human MSC osteogenic differentiation remains unexplored. In this study, we have characterized the expression of caveolin-1 in human bone marrow derived MSCs. We show that caveolin-1 protein is enriched in density gradient-fractionated MSC plasma membrane, consisting of ~100 nm diameter membrane-bound vesicles, and is distributed in a punctate pattern by immunofluoresence localization. Expression of caveolin-1 increases in MSCs induced to undergo osteogenic differentiation, and siRNA-mediated knockdown of caveolin-1 expression enhances MSC proliferation and osteogenic differentiation. Taken together, these findings suggest that caveolin-1 normally acts to regulate the differentiation and renewal of MSCs, and increased caveolin-1 expression during MSC osteogenesis likely acts as a negative feedback to stabilize the cell phenotype.

Epithelium-dependent modulation of responsiveness of airways from caveolin-1 knockout mice is mediated through cyclooxygenase-2 and 5-lipoxygenase

BACKGROUND AND PURPOSE

Acute silencing of caveolin-1 (Cav-1) modulates receptor-mediated contraction of airway smooth muscle. Moreover, COX-2- and 5-lipoxygenase (5-LO)-derived prostaglandin and leukotriene biosynthesis can influence smooth muscle reactivity. COX-2 half-life can be prolonged through association with Cav-1. We suggested that lack of Cav-1 modulated levels of COX-2 which in turn modulated tracheal contraction, when arachidonic acid signalling was disturbed by inhibition of COX-2.

EXPERIMENTAL APPROACH

Using tracheal rings from Cav-1 knockout (KO) and wild-type mice (B6129SF2/J), we measured isometric contractions to methacholine and used PCR, immunoblotting and immunohistology to monitor expression of relevant proteins.

KEY RESULTS

Tracheal rings from Cav-1 KO and wild-type mice exhibited similar responses, but the COX-2 inhibitor, indomethacin, increased responses of tracheal rings from Cav-1 KO mice to methacholine. The phospholipase A₂ inhibitor, eicosatetraynoic acid, which inhibits formation of both COX-2 and 5-LO metabolites, had no effect on wild-type or Cav-1 KO tissues. Indomethacin-mediated hyperreactivity was ablated by the LTD₄ receptor antagonist (montelukast) and 5-LO inhibitor (zileuton). The potentiating effect of indomethacin on Cav-1 KO responses to methacholine was blocked by epithelial denudation. Immunoprecipitation showed that COX-2 binds Cav-1 in wild-type lungs. Immunoblotting and qPCR revealed elevated levels of COX-2 and 5-LO protein, but not COX-1, in Cav-1 KO tracheas, a feature that was prevented by removal of the epithelium.

CONCLUSION AND IMPLICATIONS

The indomethacin-induced hypercontractility observed in Cav-1 KO tracheas was linked to increased expression of COX-2 and 5-LO, which probably enhanced arachidonic acid shunting and generation of pro-contractile leukotrienes when COX-2 was inhibited.

Transcription factor TCF4 maintains the properties of human corneal epithelial stem cells

TCF4, a key transcription factor of Wnt signaling system, has been recently found to be essential for maintaining stem cells. However, its signaling pathway is not well elucidated. This study was to explore the functional roles and signaling pathway of TCF4 in maintaining adult stem cell properties using human corneal epithelial stem cells as a model. With immunofluorescent staining and real-time polymerase chain reaction, we observed that TCF4 was exclusively expressed in the basal layer of human limbal epithelium where corneal epithelial stem cells reside. TCF4 was found to be well colocalized with ABCG2 and p63, two recognized epithelial stem/progenitor cell markers. Using in vitro culture models of primary human corneal epithelial cells, we revealed that TCF4 mRNA and protein were upregulated by cells in exponential growth stage, and RNA interference by small interfering RNA-TCF4 (10-50 nM) transfection blocked TCF4 signaling and suppressed cell proliferation as measured by WST-1 assay. TCF4 silence was found to be accompanied by downregulated proliferation-associated factors p63 and survivin, as well as upregulated cyclin-dependent kinase inhibitor 1C (p57). By creating a wound healing model in vitro, we identified upregulation and activation of β-catenin/TCF4 with their protein translocation from cytoplasm to nuclei, as evaluated by reverse transcription-quantitative real-time polymerase chain reaction, immunostaining, and Western blotting. Upregulated p63/survivin and downregulated p57 were further identified to be TCF4 downstream molecules that promote cell migration and proliferation in wound healing process. These findings demonstrate that transcription factor TCF4 plays an important role in determining or maintaining the phenotype and functional properties of human corneal epithelial stem cells.

Caveolin-1: role in cell signaling

Caveolins (Cavs) are integrated plasma membrane proteins that are complex signaling regulators with numerous partners and whose activity is highly dependent on cellular context. Cavs are both positive and negative regulators of cell signaling in and/or out of caveolae, invaginated lipid raft domains whose formation is caveolin expression dependent. Caveolins and rafts have been implicated in membrane compartmentalization; proteins and lipids accumulate in these membrane microdomains where they transmit fast, amplified and specific signaling cascades. The concept of plasma membrane organization within functional rafts is still in exploration and sometimes questioned. In this chapter, we discuss the opposing functions of caveolin in cell signaling regulation focusing on the role of caveolin both as a promoter and inhibitor of different signaling pathways and on the impact of membrane domain localization on caveolin functionality in cell proliferation, survival, apoptosis and migration.

Prostaglandins in cancer cell adhesion, migration, and invasion

Prostaglandins exert a profound influence over the adhesive, migratory, and invasive behavior of cells during the development and progression of cancer. Cyclooxygenase-2 (COX-2) and microsomal prostaglandin E₂ synthase-1 (mPGES-1) are upregulated in inflammation and cancer. This results in the production of prostaglandin E₂ (PGE₂), which binds to and activates G-protein-coupled prostaglandin E_1–4 receptors (EP_1–4). Selectively targeting the COX-2/mPGES-1/PGE₂/EP_1–4 axis of the prostaglandin pathway can reduce the adhesion, migration, invasion, and angiogenesis. Once stimulated by prostaglandins, cadherin adhesive connections between epithelial or endothelial cells are lost. This enables cells to invade through the underlying basement membrane and extracellular matrix (ECM). Interactions with the ECM are mediated by cell surface integrins by “outside-in signaling” through Src and focal adhesion kinase (FAK) and/or “inside-out signaling” through talins and kindlins. Combining the use of COX-2/mPGES-1/PGE₂/EP_1–4 axis-targeted molecules with those targeting cell surface adhesion receptors or their downstream signaling molecules may enhance cancer therapy.

Protein kinase CK2 promotes cancer cell viability via up-regulation of cyclooxygenase-2 expression and enhanced prostaglandin E2 production

Augmented expression of protein kinase CK2 is associated with hyperproliferation and resistance to apoptosis in cancer cells. Effects of CK2 are at least partially linked to signaling via the Wnt/β-catenin pathway, which is dramatically enhanced in colon cancer. Cyclooxygenase-2 (COX-2), a Wnt/β-catenin target gene, has been associated with enhanced cancer progression and metastasis. However, the possibility that a connection may exist between CK2 and COX-2 has not been explored previously. Here we investigated changes in COX-2 expression and activity upon CK2 modulation and evaluated how these changes affected cell viability. COX-2 expression and cell viability decreased upon selective inhibition of COX-2 with SC-791 or CK2 with 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT), both in human colon (HT29-ATCC, HT29-US, DLD-1) and breast (ZR-75) cancer cells, as well as in human embryonic kidney (HEK-293T) cells. On the other hand, ectopic CK2α expression promoted up-regulation of COX-2 by activating the Wnt/β-catenin pathway in HEK-293T cells. Noteworthy, over-expression of either CK2α, β-catenin or COX-2, as well as supplementation of the medium with prostaglandin E2 (PGE2), all were individually sufficient to overcome limitations in cell viability triggered by CK2 inhibition either upon addition of DMAT or over-expression of a dominant negative CK2α variant. Altogether, these findings provide new insight to the role of CK2 in cancer by up-regulating COX-2 expression and thereby PGE2 production.

Leukotriene B(4) receptors BLT1 and BLT2 are involved in interleukin-8 production in human neutrophils induced by Trichomonas vaginalis-derived secretory products

OBJECTIVE AND METHOD

Trichomonas vaginalis is a flagellated protozoan parasite that causes human trichomoniasis. Although T. vaginalis itself can secrete lipid mediator leukotriene (LT) B(4) leading to neutrophil activation, information regarding the signaling mechanism involved in neutrophil activation induced by T. vaginalis-secreted LTB(4) is limited. We investigated whether LTB(4) contained in the T. vaginalis-derived secretory products (TvSP) is closely involved in interleukin (IL)-8 production in human neutrophils via LTB(4) receptors BLT1 or BLT2.

RESULTS

T. vaginalis produced more than 714 pg/ml of LTB(4) per 1 × 10(7) trichomonads. The ability of trichomonads to secrete LTB(4) was inhibited by treatment of trichomonads with the 5-lipo-oxygenease inhibitor AA861, but not the cyclo-oxygenease I inhibitor FR122047. When neutrophils were incubated with TvSP obtained from 1 × 10(7) trichomonads, IL-8 protein secretion was significantly increased compared to results for cells incubated with medium alone. The stimulatory effect of TvSP on IL-8 production was strongly inhibited by pretreatment of TvSP with lipase, although pretreatment with heat or proteinase K showed little inhibitory effect. Moreover, TvSP-induced IL-8 production was efficiently inhibited when trichomonads were pretreated with AA861 or when neutrophils were pretreated with antagonists for BLT1 or BLT2.

CONCLUSION

Our results suggest that LTB(4) receptors BLT1 and BLT2 are involved in IL-8 production in neutrophils induced by T. vaginalis.

New glimpses of caveolin-1 functions in embryonic development and human diseases

Caveolin-1 (Cav-1) isoforms, including Cav-1α and Cav-1β, were identified as integral membrane proteins and the major components of caveolae. Cav-1 proteins are highly conserved during evolution from {itCaenorhabditis elegans} to human and are capable of interacting with many signaling molecules through their caveolin scaffolding domains to regulate the activities of multiple signaling pathways. Thus, Cav-1 plays crucial roles in the regulation of cellular proliferation, differentiation and apoptosis in a cell-specific and contextual manner. In addition, Cav-1 is essential for embryonic development of vertebrates owing to its regulation of BMP, Wnt, TGF-β and other key signaling molecules. Moreover, Cav-1 is mainly expressed in terminally differentiated cells and its abnormal expression is often associated with human diseases, such as tumor progression, cardiovascular diseases, fibrosis, lung regeneration, and diseases related to virus. In this review, we will further discuss the potential of Cav-1 as a target for disease therapy and multiple drug resistance.

The role of caveolin-1 in human breast cancer

Caveolin-1 is the essential constituent protein of specialised plasma membrane invaginations called caveolae. The unique topology of caveolin-1 facilitates the role of caveolae as molecular hubs, integrating the activity of a multitude of signalling molecules. Despite improvements in our understanding of caveolin-1 interactions and the function of caveolae, the relationship between dysfunctional caveolin-1 and tumourigenesis remains contentious. Perhaps most intriguing has been the demonstration of both oncogenic and tumour suppressor function within particular tumour types, including breast cancer. In this review, the biological and clinical relevance of caveolin-1 in human breast cancer are considered. Evidence is systematically presented for the potential tumour suppressor and oncogenic functions of caveolin-1. Specific reference is made to interactions between caveolin-1 and signalling pathways in the clinical and biological subtypes of breast cancer. Areas of controversy are discussed and technical considerations are highlighted. Translational implications and potential for specific therapeutic manipulation of caveolin-1 are evaluated in the context of evidence from in vitro and in vivo studies.

CK2 functionally interacts with AKT/PKB to promote the β-catenin-dependent expression of survivin and enhance cell survival

β-Catenin is crucial in the canonical Wnt signaling pathway. This pathway is up-regulated by CK2 which is associated with an enhanced expression of the antiapoptotic protein survivin, although the underlying molecular mechanism is unknown. AKT/PKB kinase phosphorylates and promotes β-catenin transcriptional activity, whereas CK2 hyperactivates AKT by phosphorylation at Ser129; however, the role of this phosphorylation on β-catenin transcriptional activity and cell survival is unclear. We studied in HEK-293T cells, the effect of CK2-dependent hyperactivation of AKT on cell viability, as well as analyzed β-catenin subcellular localization and transcriptional activity and survivin expression. CK2α overexpression led to an augmented β-catenin-dependent transcription and protein levels of survivin, and consequently an enhanced resistance to apoptosis. However, CK2α-enhancing effects were reversed when an AKT mutant deficient in Ser129 phosphorylation by CK2 was co-expressed. Therefore, our results strongly suggest that CK2α-specific enhancement of β-catenin transcriptional activity as well as cell survival may depend on AKT hyperactivation by CK2.

Caveolin-1: an essential modulator of cancer cell radio-and chemoresistance

Caveolin-1 is a ubiquitously expressed integral membrane protein and essential for the formation of so-called Caveolae, small invaginations of the plasma membrane. Caveolae are involved in major physiological functions of the mammalian cell, including endocytosis and transcytosis processes, signal transduction and cholesterol homeostasis. During the last decade, it became evident that Caveolin-1 plays a key role in cancer progression and metastasis. As it has also been described as a tumor suppressor, the plethora of intracellular processes Caveolin-1 contributes to remains to be fully identified. Differences in pathophysiological protein function have been ascribed to cell-specific roles of Caveolin-1 and to cancer stage dependency. An important aspect of the protein in terms of cancer cure seems to be its relevance as a prognostic marker and for induction of metastasis. These diverse functions of Caveolin-1 were expanded by recent data showing its role in radio- and chemoresistance of tumor cells, a new aspect this review will concentrate on. Since resistance of tumor cells to conventional treatment regimes is still a major obstacle in cancer treatment, new targeting approaches in combination with conventional radio- and chemotherapy are highly desirable and of great interest to improve cancer patient cure.