TFEB inhibition induces melanoma shut-down by blocking the cell cycle and rewiring metabolism

Melanomas are characterised by accelerated cell proliferation and metabolic reprogramming resulting from the contemporary dysregulation of the MAPK pathway, glycolysis and the tricarboxylic acid (TCA) cycle. Here, we suggest that the oncogenic transcription factor EB (TFEB), a key regulator of lysosomal biogenesis and function, controls melanoma tumour growth through a transcriptional programme targeting ERK1/2 activity and glucose, glutamine and cholesterol metabolism. Mechanistically, TFEB binds and negatively regulates the promoter of DUSP-1, which dephosphorylates ERK1/2. In melanoma cells, TFEB silencing correlates with ERK1/2 dephosphorylation at the activation-related p-Thr185 and p-Tyr187 residues. The decreased ERK1/2 activity synergises with TFEB control of CDK4 expression, resulting in cell proliferation blockade. Simultaneously, TFEB rewires metabolism, influencing glycolysis, glucose and glutamine uptake, and cholesterol synthesis. In TFEB-silenced melanoma cells, cholesterol synthesis is impaired, and the uptake of glucose and glutamine is inhibited, leading to a reduction in glycolysis, glutaminolysis and oxidative phosphorylation. Moreover, the reduction in TFEB level induces reverses TCA cycle, leading to fatty acid production. A syngeneic BRAFV600E melanoma model recapitulated the in vitro study results, showing that TFEB silencing sustains the reduction in tumour growth, increase in DUSP-1 level and inhibition of ERK1/2 action, suggesting a pivotal role for TFEB in maintaining proliferative melanoma cell behaviour and the operational metabolic pathways necessary for meeting the high energy demands of melanoma cells.

FAM49B, a novel regulator of mitochondrial function and integrity that suppresses tumor metastasis

Mitochondrial dysregulation plays a central role in cancers and drives reactive oxygen species (ROS)-dependent tumor progression. We investigated the pro-tumoral roles of mitochondrial dynamics and altered intracellular ROS levels in pancreatic ductal adenocarcinoma (PDAC). We identified 'family with sequence similarity 49 member B' (FAM49B) as a mitochondria-localized protein that regulates mitochondrial fission and cancer progression. Silencing FAM49B in PDAC cells resulted in increased fission and mitochondrial ROS generation, which enhanced PDAC cell proliferation and invasion. Notably, FAM49B expression levels in PDAC cells were downregulated by the tumor microenvironment. Overall, the results of this study show that FAM49B acts as a suppressor of cancer cell proliferation and invasion in PDAC by regulating tumor mitochondrial redox reactions and metabolism.

The association of statins plus LDL receptor-targeted liposome-encapsulated doxorubicin increases in vitro drug delivery across blood-brain barrier cells

BACKGROUND AND PURPOSE

The passage of drugs across the blood-brain barrier (BBB) limits the efficacy of chemotherapy in brain tumours. For instance, the anticancer drug doxorubicin, which is effective against glioblastoma in vitro, has poor efficacy in vivo, because it is extruded by P-glycoprotein (Pgp/ABCB1), multidrug resistance-related proteins and breast cancer resistance protein (BCRP/ABCG2) in BBB cells. The aim of this study was to convert poorly permeant drugs like doxorubicin into drugs able to cross the BBB.

EXPERIMENTAL APPROACH

Experiments were performed on primary human cerebral microvascular endothelial hCMEC/D3 cells, alone and co-cultured with human brain and epithelial tumour cells.

KEY RESULTS

Statins reduced the efflux activity of Pgp/ABCB1 and BCRP/ABCG2 in hCMEC/D3 cells by increasing the synthesis of NO, which elicits the nitration of critical tyrosine residues on these transporters. Statins also increased the number of low-density lipoprotein (LDL) receptors exposed on the surface of BBB cells, as well as on tumour cells like human glioblastoma. We showed that the association of statins plus drug-loaded nanoparticles engineered as LDLs was effective as a vehicle for non-permeant drugs like doxorubicin to cross the BBB, allowing its delivery into primary and metastatic brain tumour cells and to achieve significant anti-tumour cytotoxicity.

CONCLUSIONS AND IMPLICATIONS

We suggest that our 'Trojan horse' approach, based on the administration of statins plus a LDL receptor-targeted liposomal drug, might have potential applications in the pharmacological therapy of different brain diseases for which the BBB represents an obstacle.

A diabetic milieu promotes OCT4 and NANOG production in human visceral-derived adipose stem cells

AIMS/HYPOTHESIS

Successful outcomes have been obtained by exploiting adipose-derived stem cells (ASCs) in regenerative medicine. NADPH oxidase (NOX)-generated reactive oxygen species (ROS) are known to control stem cell self-renewal. Several high glucose (HG)-mediated effects depend on NOX-generated ROS. In this study, we investigated whether, and how mechanistically, HG concentrations control ASC fate in patients with diabetes.

METHODS

ASCs from the visceral adipose tissue of non-diabetic (N-ASCs) and diabetic participants (D-ASCs), identified by surface markers, were counted and evaluated for ROS generation and stem cell properties. Their ability to release soluble factors was assessed by BioPlex analysis. To reproduce an in vitro diabetic glucose milieu, N-ASCs were cultured in HG (25 mmol/l) or normal glucose (NG) concentration (5 mmol/l), as control. ASC pluripotency was assessed by in vitro study. The p47(phox) NOX subunit, AKT and octamer-binding transcription factor 4 (OCT4; also known as POU5F1) were knocked down by small-interfering RNA technology. Stem-cell features were evaluated by sphere cluster formation.

RESULTS

The ASC number was higher in diabetic patients than in non-diabetic controls. Production of OCT4 and NANOG, stem-cell-specific transcription factors, was upregulated in D-ASCs compared with N-ASCs. Moreover, we found that ROS production and AKT activation drove D-ASC, but not N-ASC, secretion. When N-ASCs were cultured in vitro in the presence of HG, they also expressed OCT4/NANOG and formed spheres. By knock-down of the p47(phox) NOX subunit, AKT and OCT4 we demonstrated that NOX-generated ROS and their downstream signals are crucial for HG-mediated ASC de-differentiation and proinflammatory cytokine production.

CONCLUSIONS/INTERPRETATION

We herein provide a rationale for exploiting D-ASCs in regenerative medicine and/or exploiting HG preconditioning to increase ASCs ex vivo.

Pleiotropic effects of cardioactive glycosides

Cardioactive glycosides, like digoxin, ouabain and related compounds, are drugs that inhibit Na(+)/K(+)-ATPase and have a strong inotropic effect on heart: they cause the Na(+)/Ca(2+) exchanger to extrude Na+ in exchange with Ca(2+) and therefore increase the [Ca(2+)](i) concentration. For this reason, some of these drugs are currently used in the treatment of congestive heart failure and cardiac arrhythmias. Recently it has been discovered that cardiac glycosides exert pleiotropic effects on many aspects of cell metabolism. Na(+)/K(+)-ATPase is not the exclusive target, as they affect the cell response to hypoxia, modulate several signaling pathways involved in cell death and proliferation, regulate the transcription of different genes and modify the pharmacokinetics of other drugs, by altering the expression and activity of drug-metabolizing enzymes. Some of these effects are related to the steroid structure of glycosides, a property which also makes them fine modulators of the synthesis of cholesterol and steroid hormones. Moreover, new endogenously synthesized glycosides have been discovered in the last years: these molecules are involved in the balance of salt and in the control of blood pressure. This review will focus on the recent studies which have demonstrated that exogenous and endogenous glycosides, besides playing a role as inotropic agents, are also important in the pathogenesis and therapy of different human diseases, such as stroke, diabetes, neurological diseases and cancer.

Geranylgeraniol prevents the cytotoxic effects of mevastatin in THP-1 cells, without decreasing the beneficial effects on cholesterol synthesis

BACKGROUND AND PURPOSE

Statins, inhibitors of hydroxymethylglutaryl-CoA reductase, reduce the intracellular synthesis of cholesterol and prevent the onset of atherosclerosis. They also decrease the synthesis of isoprenoid molecules, such as the side chain of ubiquinone and geranylgeranyl pyrophosphate. As a consequence, statins impair mitochondrial metabolism and the activation of small monomeric GTPases (such as Rho and Ras), causing toxic effects. To date, a successful strategy to prevent statin toxicity is lacking.

EXPERIMENTAL APPROACH

In human monocytic THP-1 cells, we measured the synthesis of cholesterol and isoprenoids, mitochondrial electron flow, the activity of RhoA and Rac, cell death and proliferation.

KEY RESULTS

Mevastatin reduced the synthesis of cholesterol, geranylgeranyl pyrophosphate and ubiquinone, mitochondrial electron transport, activity of RhoA and Rac, and cell proliferation, accompanied by increased cell death. Geranylgeraniol, a cell-permeable analogue of geranylgeranyl pyrophosphate, reversed all these effects of mevastatin, without affecting its ability to reduce cholesterol synthesis. Notably, geranylgeraniol was more effective than the addition of exogenous ubiquinone, which rescued mitochondrial respiratory activity and reversed mevastatin cytotoxicity, but did not alter the decrease in cell proliferation. The same results were obtained in human liver HepG2 cells.

CONCLUSIONS AND IMPLICATIONS

Geranylgeraniol had a broader protective effect against the cytotoxicity of statins than exogenous ubiquinone. Therefore, geranylgeraniol may be a more useful and practical means of limiting the toxicities of statins, without reducing their efficacy as cholesterol lowering agents.

Artemisinin induces doxorubicin resistance in human colon cancer cells via calcium-dependent activation of HIF-1alpha and P-glycoprotein overexpression

BACKGROUND AND PURPOSE

Artemisinin is an antimalarial drug exerting pleiotropic effects, such as the inhibition of the transcription factor nuclear factor-kappa B and of the sarcoplasmic/endoplasmic reticulum Ca(++)-ATPase (SERCA) of P. falciparum. As the sesquiterpene lactone thapsigargin, a known inhibitor of mammalian SERCA, enhances the expression of P-glycoprotein (Pgp) by increasing the intracellular Ca(++) ([Ca(++)](i)) level, we investigated whether artemisinin and its structural homologue parthenolide could inhibit SERCA in human colon carcinoma HT29 cells and induce a resistance to doxorubicin.

EXPERIMENTAL APPROACH

HT29 cells were incubated with artemisinin or parthenolide and assessed for SERCA activity, [Ca(++)](i) levels, Pgp expression, doxorubicin accumulation and toxicity, and translocation of the hypoxia-inducible factor, HIF-1alpha.

KEY RESULTS

Artemisinin and parthenolide, like the specific SERCA inhibitors thapsigargin and cyclopiazonic acid, reduced the activity of SERCA. They also increased intracellular calcium concentration ([Ca(++)](i)) and Pgp expression and decreased doxorubicin accumulation and cytotoxicity. The intracellular Ca(++) chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, and the inhibitor of calmodulin-dependent kinase II (CaMKII) KN93 prevented these effects. CaMKII is known to promote the phosphorylation and the activation of HIF-1alpha, which may induce Pgp. In HT29 cells, artemisinin and parthenolide induced the phosphorylation of HIF-1alpha, which was inhibited by KN93.

CONCLUSIONS AND IMPLICATIONS

Our results suggest that artemisinin and parthenolide may act as SERCA inhibitors and, like other SERCA inhibitors, induce resistance to doxorubicin in human colon cancer cells, via the CaMKII-dependent activation of HIF-1alpha and the induction of Pgp.

Asbestos induces doxorubicin resistance in MM98 mesothelioma cells via HIF-1alpha

Human malignant mesothelioma (HMM), which is strongly related to asbestos exposure, exhibits high resistance to many anticancer drugs. Asbestos fibre deposition in the lung may cause hypoxia and iron chelation at the fibre surface. Hypoxia-inducible factor (HIF)-1alpha, which is upregulated by a decreased availability of oxygen and iron, controls the expression of membrane transporters, such as P-glycoprotein (Pgp), which actively extrude the anticancer drugs. The present study aimed to assess whether asbestos may play a role in the induction of doxorubicin resistance in HMM cells through the activation of HIF-1alpha and an increased expression of Pgp. After 24-h incubation with crocidolite asbestos or with the iron chelator dexrazoxane, or under hypoxia, HMM cells were tested for HIF-1alpha activation, Pgp expression, accumulation of doxorubicin and sensitivity to its toxic effect. Crocidolite, dexrazoxane and hypoxia caused HIF-1alpha activation, Pgp overexpression and increased resistance to doxorubicin accumulation and toxicity. These effects were prevented by the co-incubation with the cell-permeating iron salt ferric nitrilotriacetate, which caused an increase of intracellular iron bioavailability, measured as increased activity of the iron regulatory protein-1. Crocidolite, dexrazoxane and hypoxia induce doxorubicin resistance in human malignant mesothelioma cells by increasing hypoxia-inducible factor-1alpha activity, through an iron-sensitive mechanism.

Insulin activates hypoxia-inducible factor-1alpha in human and rat vascular smooth muscle cells via phosphatidylinositol-3 kinase and mitogen-activated protein kinase pathways: impairment in insulin resistance owing to defects in insulin signalling

AIMS/HYPOTHESIS

We previously demonstrated that insulin stimulates vascular endothelial growth factor (VEGF) synthesis and secretion via phosphatidylinositol-3 kinase (PI3-K) and mitogen-activated protein kinase (MAPK) pathways in vascular smooth muscle cells (VSMC) from humans and from insulin-sensitive lean Zucker fa/+ rats. We also showed that this effect is attenuated in VSMC from insulin-resistant obese Zucker fa/fa rats. As it is not known whether the effects of insulin on VEGF involve activation of hypoxia-inducible factor-1 (HIF-1), we aimed to evaluate: (1) whether insulin modulates HIF-1alpha protein synthesis and activity; (2) the insulin signalling pathways involved; and (3) the role of insulin resistance.

METHODS

Using aortic VSMC taken from humans and Zucker rats and cultured in normoxia, the following were evaluated: (1) dose-dependent (0.5, 1, 2 nmol/l) and time-dependent (2, 4, 6 h) effects exerted by insulin on HIF-1alpha content in both nucleus and cytosol, measured by Western blots; (2) insulin effects on HIF-1 DNA-binding activity on the VEGF gene, measured by electrophoretic mobility shift assay; and (3) involvement of the insulin signalling molecules in these insulin actions, by using the following inhibitors: LY294002 (PI3-K), PD98059 (extracellular signal regulated kinase [ERK]), SP600125 (Jun N terminal kinase [JNK]), SB203580 (p38 mitogen-activated protein kinase) and rapamycin (mammalian target of rapamycin), and by detecting the insulin signalling molecules by Western blots.

RESULTS

In aortic VSMC from humans and Zucker fa/+ rats cultured in normoxia insulin increases the HIF-1alpha content in cytosol and nucleus via dose- and time-dependent mechanisms, and HIF-1 DNA-binding activity on the VEGF gene. The insulin-induced increase of HIF-1alpha is blunted by the translation inhibitor cycloheximide, LY294002, PD98059, SP600125 and rapamycin, but not by SB203580. It is also reduced in Zucker fa/fa rats, which present an impaired ability of insulin to induce Akt, ERK-1/2 and JNK-1/2 phosphorylation.

CONCLUSIONS/INTERPRETATION

These results provide a biological mechanism for the impaired collateral vessel formation in obesity.

Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells

OBJECTIVE

In cultured human vascular smooth muscle cells, insulin increases cyclic GMP production by inducing nitric oxide (NO) synthesis. The aim of the present study was to determine whether in these cells the insulin-stimulated NO/cyclic GMP pathway plays a role in the regulation of glucose uptake.

METHODS AND RESULTS

Glucose transport in human vascular smooth muscle cells was measured as uptake of 2-deoxy-d-[3H]glucose, cyclic GMP synthesis was checked by radioimmunoassay, and GLUT4 recruitment into the plasma membrane was determined by immunofluorescence. Insulin-stimulated glucose transport and GLUT4 recruitment were blocked by an inhibitor of NO synthesis and mimicked by NO-releasing drugs. Insulin- and NO-elicited glucose uptake were blocked by inhibitors of soluble guanylate cyclase and cyclic GMP-dependent protein kinase; furthermore, glucose transport was stimulated by an analog of cyclic GMP.

CONCLUSIONS

Our results suggest that insulin-elicited glucose transport (and the corresponding GLUT4 recruitment into the plasma membrane) in human vascular smooth muscle cells is mediated by an increased synthesis of NO, which stimulates the production of cyclic GMP and the subsequent activation of a cyclic GMP-dependent protein kinase.

[Informed consent forms in medical practice: the results of a knowledge survey]

"Federico II" University of Naples Hospital Management's Staff considered 47 informed consent forms in order to evaluate quality and quantity of the information transmitted to patients. Every form, distinguished by procedure (surgical, pharmacological, anesthesiologic or related to blood transfusions) was evaluated for the accuracy and validity of information related to: diagnosis, prognosis, diagnostic and therapeutic opportunities, expected benefits, adverse-side effects, iatrogenic risks, privacy policy on personal data. The forms were judged by information completeness criteria "conformed" or "not conformed" with standards. Our analysis demonstrate that physicians often are unaware of legal and ethical topics related to constructing informed consent forms. They usually omit crucial information or would use strict technical language. So far, we conclude Hospital Management's Staff definitively has a role in improving informed consent forms by establishing guidelines and promoting ethical issues. Final result could be to deserve stronger patient confidence in medical institutions.

Upper respiratory infections in children: response to endonasal administration of IGA

Children, 36, predisposed to frequent upper respiratory infections were treated with endonasal administration of an IgA enriched preparation or placebo in a randomized double blind trial. We found a reduction in the number of infectious episodes and in the number of enlarged regional lymph nodes. Also, an increase of IgA levels in saliva in the treated group was observed, probably not only due to the effect of IgA supplementation, but also to an immunoregulatory effect on the mucosa caused by the preparation administered. We found this therapy very useful in the prophylaxis of upper respiratory infections, being the nasal administration very convenient to be used in children.