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S1-Prognostic value of USP6NL gain in the METABRIC dataset S2-Correleation of USP6NL protein expression with clinical-pathological parameters in the TMA cohort

In vivo rebound MET activation

USP6NL overexpression inhibits GLUT1 endocytosis

MET oncogene amplification is emerging as a major mechanism of acquired resistance to EGFR-directed therapy in lung and colorectal cancers. Furthermore, MET amplification predicts responsiveness to MET inhibitors currently in clinical trials. Among the anti-MET drugs available, ATP-competitive small-molecule kinase inhibitors abrogate receptor autophosphorylation and downstream activation of ERK1/2 and AKT, resulting in cell-cycle arrest. However, this antiproliferative effect allows persistence of a pool of cancer cells that are quiescent but alive. Once the inhibition is removed, rebound activation of MET-driven cell proliferative pathways and tumor growth may occur, an adverse event observed frequently in clinical settings after drug discontinuation. Here we show that inhibitor withdrawal prompts receptor phosphorylation to levels higher than those displayed at steady-state and generates a rebound effect pushing quiescent cancer cells back into the cell cycle, both in vitro and in experimental tumor models in vivo. Mechanistically, we found that inhibitor treatment blocks MET endocytosis, causing a local increase in the number of receptors at the plasma membrane. Upon inhibitor washout, the receptor is readily rephosphorylated. The initial phosphorylation is not only increased but also prolonged in duration due to downmodulation of a phosphatase-mediated MET-negative feedback loop, which accompanies receptor internalization. Notably, treatment with a MET therapeutic antibody that induces proteolytic cleavage of the receptor at the cell surface substantially prevents this rebound effect, providing a rationale to combine or alternate these mechanistically different types of MET-targeted therapy. Cancer Res; 76(17); 5019–29. ©2016 AACR.

Legends to Supplementary Figures S1-S6

The physiological function of the epidermal growth factor receptor (EGFR) is to regulate epithelial tissue development and homeostasis. In pathological settings, mostly in lung and breast cancer and in glioblastoma, the EGFR is a driver of tumorigenesis. Inappropriate activation of the EGFR in cancer mainly results from amplification and point mutations at the genomic locus, but transcriptional upregulation or ligand overproduction due to autocrine/paracrine mechanisms has also been described. Moreover, the EGFR is increasingly recognized as a biomarker of resistance in tumors, as its amplification or secondary mutations have been found to arise under drug pressure. This evidence, in addition to the prominent function that this receptor plays in normal epithelia, has prompted intense investigations into the role of the EGFR both at physiological and at pathological level. Despite the large body of knowledge obtained over the last two decades, previously unrecognized (herein defined as 'noncanonical') functions of the EGFR are currently emerging. Here, we will initially review the canonical ligand-induced EGFR signaling pathway, with particular emphasis to its regulation by endocytosis and subversion in human tumors. We will then focus on the most recent advances in uncovering noncanonical EGFR functions in stress-induced trafficking, autophagy, and energy metabolism, with a perspective on future therapeutic applications.

Tumor microenvironment is particularly enriched with extracellular ATP (eATP), but conflicting evidence has been provided on its functional effects on tumor growth and vascular remodeling. We have previously shown that high eATP concentrations exert a strong anti-migratory, antiangiogenic and normalizing activity on human tumor-derived endothelial cells (TECs). Since both metabotropic and ionotropic purinergic receptors trigger cytosolic calcium increase ([Ca2+]c), the present work investigated the properties of [Ca2+]c events elicited by high eATP in TECs and their role in anti-migratory activity. In particular, the quantitative and kinetic properties of purinergic-induced Ca2+ release from intracellular stores and Ca2+ entry from extracellular medium were investigated. The main conclusions are: (1) stimulation of TECs with high eATP triggers [Ca2+]c signals which include Ca2+ mobilization from intracellular stores (mainly ER) and Ca2+ entry through the plasma membrane, (2) the long-lasting Ca2+ influx phase requires both store-operated Ca2+ entry (SOCE) and non-SOCE components, (3) SOCE is not significantly involved in the antimigratory effect of high ATP stimulation, (4) ER is the main source for intracellular Ca2+ release by eATP: it is required for the constitutive migratory potential of TECs but is not the only determinant for the inhibitory effect of high eATP, (5) a complex interplay occurs among ER, mitochondria and lysosomes upon purinergic stimulation, (6) high eUTP is unable to inhibit TEC migration and evokes [Ca2+]c signals very similar to those described for eATP. The potential role played by store-independent Ca2+ entry and Ca2+-independent events in the regulation of TEC migration by high purinergic stimula deserves future investigation.

USP6NL, also named RN-tre, is a GTPase-activating protein involved in control of endocytosis and signal transduction. Here we report that USP6NL is overexpressed in breast cancer, mainly of the basal-like/integrative cluster 10 subtype. Increased USP6NL levels were accompanied by gene amplification and were associated with worse prognosis in the METABRIC dataset, retaining prognostic value in multivariable analysis. High levels of USP6NL in breast cancer cells delayed endocytosis and degradation of the EGFR, causing chronic AKT (protein kinase B) activation. In turn, AKT stabilized the glucose transporter GLUT1 at the plasma membrane, increasing aerobic glycolysis. In agreement, elevated USP6NL sensitized breast cancer cells to glucose deprivation, indicating that their glycolytic capacity relies on this protein. Depletion of USP6NL accelerated EGFR/AKT downregulation and GLUT1 degradation, impairing cell proliferation exclusively in breast cancer cells that harbored increased levels of USP6NL. Overall, these findings argue that USP6NL overexpression generates a metabolic rewiring that is essential to foster the glycolytic demand of breast cancer cells and promote their proliferation. Significance: USP6NL overexpression leads to glycolysis addiction of breast cancer cells and presents a point of metabolic vulnerability for therapeutic targeting in a subset of aggressive basal-like breast tumors. Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3432/F1.large.jpg. Cancer Res; 78(13); 3432–44. ©2018 AACR.

Purinergic signaling is involved in inflammation and cancer. Extracellular ATP accumulates in tumor interstitium, reaching hundreds micromolar concentrations, but its functional role on tumor vasculature and endothelium is unknown. Here we show that high ATP doses (>20 μM) strongly inhibit migration of endothelial cells from human breast carcinoma (BTEC), but not of normal human microvascular EC. Lower doses (1–10 μM) result ineffective. The anti-migratory activity is associated with cytoskeleton remodeling and is significantly prevented by hypoxia. Pharmacological and molecular evidences suggest a major role for P2X7R and P2Y11R in ATP-mediated inhibition of TEC migration: selective activation of these purinergic receptors by BzATP mimics the anti-migratory effect of ATP, which is in turn impaired by their pharmacological or molecular silencing. Downstream pathway includes calcium-dependent Adenilyl Cyclase 10 (AC10) recruitment, cAMP release and EPAC-1 activation. Notably, high ATP enhances TEC-mediated attraction of human pericytes, leading to a decrease of endothelial permeability, a hallmark of vessel normalization. Finally, we provide the first evidence of in vivo P2X7R expression in blood vessels of murine and human breast carcinoma. In conclusion, we have identified a purinergic pathway selectively acting as an antiangiogenic and normalizing signal for human tumor-derived vascular endothelium.

Hydrogen sulphide (H 2 S) is a newly discovered gasotransmitter that regulates multiple steps in VEGF-induced angiogenesis. An increase in intracellular Ca 2+ concentration ([Ca 2+ ] i ) is central to endothelial proliferation and may be triggered by both VEGF and H 2 S. Albeit VEGFR-2 might serve as H 2 S receptor, the mechanistic relationship between VEGF- and H 2 S-induced Ca 2+ signals in endothelial cells is unclear. The present study aimed at assessing whether and how NaHS, a widely employed H 2 S donor, stimulates pro-angiogenic Ca 2+ signals in Ea.hy926 cells, a suitable surrogate for mature endothelial cells, and human endothelial progenitor cells (EPCs). We found that NaHS induced a dose-dependent increase in [Ca 2+ ] i in Ea.hy926 cells. NaHS-induced Ca 2+ signals in Ea.hy926 cells did not require extracellular Ca 2+ entry, while they were inhibited upon pharmacological blockade of the phospholipase C/inositol-1,4,5-trisphosphate (InsP 3 ) signalling pathway. Moreover, the Ca 2+ response to NaHS was prevented by genistein, but not by SU5416, which selectively inhibits VEGFR-2. However, VEGF-induced Ca 2+ signals were suppressed by dl -propargylglycine (PAG), which blocks the H 2 S-producing enzyme, cystathionine γ-lyase. Consistent with these data, VEGF-induced proliferation and migration were inhibited by PAG in Ea.hy926 cells, albeit NaHS alone did not influence these processes. Conversely, NaHS elevated [Ca 2+ ] i only in a modest fraction of circulating EPCs, whereas neither VEGF-induced Ca 2+ oscillations nor VEGF-dependent proliferation were affected by PAG. Therefore, H 2 S-evoked elevation in [Ca 2+ ] i is essential to trigger the pro-angiogenic Ca 2+ response to VEGF in mature endothelial cells, but not in their immature progenitors.

MET oncogene amplification is emerging as a major mechanism of acquired resistance to EGFR-directed therapy in lung and colorectal cancers. Furthermore, MET amplification predicts responsiveness to MET inhibitors currently in clinical trials. Among the anti-MET drugs available, ATP-competitive small-molecule kinase inhibitors abrogate receptor autophosphorylation and downstream activation of ERK1/2 and AKT, resulting in cell-cycle arrest. However, this antiproliferative effect allows persistence of a pool of cancer cells that are quiescent but alive. Once the inhibition is removed, rebound activation of MET-driven cell proliferative pathways and tumor growth may occur, an adverse event observed frequently in clinical settings after drug discontinuation. Here we show that inhibitor withdrawal prompts receptor phosphorylation to levels higher than those displayed at steady-state and generates a rebound effect pushing quiescent cancer cells back into the cell cycle, both in vitro and in experimental tumor models in vivo. Mechanistically, we found that inhibitor treatment blocks MET endocytosis, causing a local increase in the number of receptors at the plasma membrane. Upon inhibitor washout, the receptor is readily rephosphorylated. The initial phosphorylation is not only increased but also prolonged in duration due to downmodulation of a phosphatase-mediated MET-negative feedback loop, which accompanies receptor internalization. Notably, treatment with a MET therapeutic antibody that induces proteolytic cleavage of the receptor at the cell surface substantially prevents this rebound effect, providing a rationale to combine or alternate these mechanistically different types of MET-targeted therapy. Cancer Res; 76(17); 5019–29. ©2016 AACR.

Endothelial cells (ECs) play a key role to maintain the functionality of blood vessels. Altered EC permeability causes severe impairment in vessel stability and is a hallmark of pathologies such as cancer and thrombosis. Integrating label-free quantitative proteomics data into genome-wide metabolic modeling, we built up a model that predicts the metabolic fluxes in ECs when cultured on a tridimensional matrix and organize into a vascular-like network. We discovered how fatty acid oxidation increases when ECs are assembled into a fully formed network that can be disrupted by inhibiting CPT1A, the fatty acid oxidation rate-limiting enzyme. Acute CPT1A inhibition reduces cellular ATP levels and oxygen consumption, which are restored by replenishing the tricarboxylic acid cycle. Remarkably, global phosphoproteomic changes measured upon acute CPT1A inhibition pinpointed altered calcium signaling. Indeed, CPT1A inhibition increases intracellular calcium oscillations. Finally, inhibiting CPT1A induces hyperpermeability in vitro and leakage of blood vessel in vivo, which were restored blocking calcium influx or replenishing the tricarboxylic acid cycle. Fatty acid oxidation emerges as central regulator of endothelial functions and blood vessel stability and druggable pathway to control pathological vascular permeability.

f these authors contributed equally Abstract Background: Hydrogen sulfide contributes to the reduction of oxidative stress-related injury in cardiomyocytes but the underlying mechanism is still unclear. Aims: Here we investigated the role of voltage-operated calcium channels (VOCCs) as mediators of the beneficial effect of H 2 S against oxidative stress in cultured rat cardiomyoblasts (H9c2). Methods: Intracellular calcium signals were measured by fluorimetric live cell imaging and cell viability by colorimetric assay. Results: Treatment with H 2 S donor (NaHS 10 µM) or Nifedipine (10 µM) decreased resting intracellular calcium concentration (Ca) i , suggesting that L-type VOCCs are negatively modulated by H 2 S. In the presence of Nifedipine H 2 S was still able to lower (Ca) i , while co- incubation with Nifedipine and Ni 2+ 100 µM completely prevented H 2 S-dependent (Ca) i decrease, suggesting that both L-type and T-type VOCCs are inhibited by H 2 S. In addition, in the same experimental conditions, H 2 S triggered a slow increase of (Ca) i whose molecular nature remains to be clarified. Pretreatment of H9c2 with NaHS (10 µM) significantly prevented cell death induced by H 2 O 2 . This effect was mimicked by pretreatment with L-Type calcium channel inhibitor Nifedipine (10 µM). Conclusions: The data provide the first evidence that H 2 S protects rat cardiomyoblasts against oxidative challenge through the inhibition of L-type calcium channels.

An increasing body of evidence suggests the involvement of hydrogen sulfide (H(2)S) in different physiological and pathological processes. Similarly to the other gasotransmitters nitric oxide (NO) and carbon monoxide (CO), this bioactive compound is rapidly diffusible through the biological membranes and acts in a paracrine fashion. Despite the large amount of biological actions observed in vitro and in vivo upon stimulation with H(2)S donors, as well as by interfering with its synthesis, the molecular targets and mechanisms through which it exerts its intracellular effects are only partially known. A number of proteins are covalently modified by H(2)S through sulfhydration of specific cysteine residues. However, only in few cases their identity has been discovered and the functional role of this post-translational modification needs to be investigated in more detail. Great attention has been devoted to potassium channels, particularly K(ATP), as they are considered key mediators of H(2)S-induced effects, and their sulfhydration has been clearly demonstrated. Recently, different authors reported the ability of H(2)S to interfere with calcium homeostasis in neurons, cardiomyocytes and endothelial cells. Since calcium signaling is involved in all cell processes, these observations attracted increasing attention from basic biology and medicine. Although some effects of H(2)S on calcium signals can be ascribed to K(ATP) modulation, there is growing consensus about the existence of other targets for the gasotransmitter. Some of them are Ca(2+)-permeable channels. In this review we discuss the state of the art in this specific field, providing an updated report of H(2)S interaction with Ca(2+) channels and its functional outcomes.

Endothelial cells (ECs) play a key role in maintaining vascular functionality. Alterations in vessel stability and permeability are hallmarks of tumor angiogenesis and may affect the efficacy of anti-cancer therapy. Modulating EC metabolism has emerged as a promising strategy to target angiogenesis in pathological conditions, but so far, little is known about the role of EC metabolism in the regulation of vessel stability and permeability. In this work we took advantage of a simplified in-vitro model of angiogenesis, where HUVECs (human umbilical vein endothelial cells) form a vascular-like network on a tridimensional matrix, to elucidate the role of EC metabolism during this process. By integrating high resolution proteomic data with a human genome scale metabolic model we built up the first predictive model of metabolic fluxes occurring in ECs forming a complex network and identified increased fluxes for reactions involving fatty acid oxidation (FAO) enzymes when ECs are assembled into a fully formed network. Upon inhibition of CPT1, the FAO rate-limiting enzyme, we disrupted the network and reduced cellular ATP levels and oxygen consumption, which were restored by replenishing the tricarboxylic acid cycle (TCAc). Remarkably, phosphoproteomic changes measured upon CPT1A inhibition evoked those triggered by thrombin, a potent inducer of EC permeability through calcium signaling. Indeed, acute CPT1A inhibition increased EC permeability in-vitro and leakage of fully formed blood vessel in-vivo, which were restored by replenishing the TCAc or inhibiting calcium influx. FAO emerges as central regulator of blood vessel stability, revealing the possibility of targeting FAO to interfere with tumor vessel permeability. Citation Format: Francesca Patella, Zachary T. Schug, Erez Persi, Lisa J. Neilson, Zahra Erami, Daniele Avanzato, Federica Maione, Juan R. Hernandez-Fernaud, Gillian Mackay, Liang Zheng, Steven Reid, Christian Frezza, Enrico Giraudo, Alessandra Fiorio Pla, Kurt Anderson, Eytan Ruppin, Eyal Gottlieb, Sara Zanivan. In-depth proteomics unveils fatty acid oxidation role in controlling vascular permeability. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr B17.

Tumor vascularization is a critical process that determines tumor growth and metastasis. In the last decade new experimental evidence obtained from in vitro and in vivo studies have challenged the classical angiogenesis model forcing us to consider new scenarios for tumor neovascularization. In particular, the genetic stability of tumor-derived endothelial cells (TECs) has been recently questioned in several studies, which show that TECs, as well as pericytes, differ significantly from their normal counterparts at genetic and functional levels. In addition to such an epigenetic action of tumor microenvironment on endothelial cells (ECs) commitment, the distinct characteristics of TECs could be due to differences in their origin compared with preexisting differentiated ECs. Intracellular Ca2+ signals are involved at different critical phases in the regulation of the complex process of angiogenesis and tumor progression. These signals are generated by a wide variety of intrinsic and extrinsic factors. Several key components of Ca2+ signaling including Ca2+ channels in the plasma membrane, endoplasmic reticulum, calcium pumps, and mitochondria contribute to the generation, amplitude, and frequency of these Ca2+ change. In particular, several members of the transient receptor potential (TRP) family of calcium-permeable channels have profound effects on the function of ECs. Because of its multifaceted role in the control of cell function, proliferation, and motility, TRP channels have been suggested as a potential molecular target for control of tumor neovascularization. Since plasma membrane Ca2+ channels are easily and directly accessible via the bloodstream, they are potential targets for a number of pharmacological and antibody-targeted therapeutic strategies, with specificity being the main limitation. In this review we discuss recent advances in understanding the role of Ca2+ channels, with specific reference to TRP channels, in tumor vascularization process.