Hypoxia-induced proliferation of HeLa cells depends on epidermal growth factor receptor-mediated arginase II induction

Functionalized α-Cyanostilbene Derivatives for Detection of Hypoxia or Proteostasis Imbalance in Live Cells

α-Cyanostilbene represents one of the easily functionalized aggregation-induced emission (AIE) scaffolds. It has been widely adopted for the construction of fluorescent materials for broad applications. Here, we further expanded the utilization of α-cyanostilbene derivatives for the detection of hypoxia or proteostasis imbalance in live cells. Four different amine containing donors were introduced to construct α-cyanostilbene derivatives (R-ASC) with donor-acceptor scaffolds. Equipped with the cysteine (Cys) reactive group, maleimide (MI), R-ASC-MI shows fluorescence turn-on property upon binding with unfolded proteins in vitro and in live cells under proteostatic stress. By virtue of R-ASC-MI, the level of unfolded protein loads in cells can be quantified by flow cytometry, or visualized under microscope. Furthermore, we also characterized the performance of R-ASC-NO2, synthetic precursors of R-ASC-MI, in cellular hypoxia. R-ASC-NO2 revealed upregulated activities of nitroreductase, as well as increased hydrophobicity in live cells, under either chemical (NaN3) induced or atmospheric (1 % O2) hypoxia. Together, the advantages of easy modification and high signal-to-noise ratio of new α-cyanostilbene derivatives reported in this work highlight the great potential of α-cyanostilbene in constructing functional biosensors and many other domains.

Hypoxic pulmonary endothelial cells release epidermal growth factor leading to vascular smooth muscle cell arginase-2 expression and proliferation

The hallmark of pulmonary hypertension (PH) is vascular remodeling. We have previously shown that human pulmonary microvascular endothelial cells (hPMVEC) respond to hypoxia with epidermal growth factor (EGF) mediated activation of the receptor tyrosine kinase, EGF receptor (EGFR), resulting in arginase-2 (Arg2)-dependent proliferation. We hypothesized that the release of EGF by hPMVEC could result in the proliferation of human pulmonary arterial smooth muscle cells (hPASMC) via activation of EGFR on the hPASMC leading to Arg2 up-regulation. To test this hypothesis, we used conditioned media (CM) from hPMVEC grown either in normoxia (NCM) or hypoxia (HCM). Human PASMC were incubated in normoxia with either HCM or NCM, and HCM caused significant induction of Arg2 and viable cell numbers. When HCM was generated with either an EGF-neutralizing antibody or an EGFR blocking antibody the resulting HCM did not induce Arg2 or increase viable cell numbers in hPASMC. Adding an EGFR blocking antibody to HCM, prevented the HCM-induced increase in Arg2 and viable cell numbers. HCM induced robust phosphorylation of hPASMC EGFR. When hPASMC were transfected with siRNA against EGFR the HCM-induced increase in viable cell numbers was prevented. When hPASMC were treated with the arginase antagonist nor-NOHA, the HCM-induced increase in viable cell numbers was prevented. These data suggest that hypoxic hPMVEC releases EGF, which activates hPASMC EGFR leading to Arg2 protein expression and an increase in viable cell numbers. We speculate that EGF neutralizing antibodies or EGFR blocking antibodies represent potential therapeutics to prevent and/or attenuate vascular remodeling in PH associated with hypoxia.

Esophageal Squamous Cell Carcinoma Is Accompanied by Local and Systemic Changes in L-arginine/NO Pathway

The L-arginine/NO pathway holds promise as a source of potential therapy target and biomarker; yet, its status and utility in esophageal squamous cell carcinoma (ESCC) is unclear. We aimed at quantifying pathway metabolites in sera from patients with ESCC (n = 61) and benign conditions (n = 62) using LC-QTOF-MS and enzyme expression in esophageal tumors and matched noncancerous samples (n = 40) using real-time PCR with reference to ESCC pathology and circulating immune/inflammatory mediators, quantified using Luminex xMAP technology. ESCC was associated with elevated systemic arginine and asymmetric dimethylarginine. Citrulline decreased and arginine bioavailability increased along with increasing ESCC advancement. Compared to adjacent tissue, tumors overexpressed ODC1, NOS2, PRMT1, and PRMT5 but had downregulated ARG1, ARG2, and DDAH1. Except for markedly higher NOS2 and lower ODC1 in tumors from M1 patients, the pathology-associated changes in enzyme expression were subtle and present also in noncancerous tissue. Both the local enzyme expression level and systemic metabolite concentration were related to circulating inflammatory and immune mediators, particularly those associated with eosinophils and those promoting viability and self-renewal of cancer stem cells. Metabolic reprogramming in ESCC manifests itself by the altered L-arginine/NO pathway. Upregulation of PRMTs in addition to NOS2 and ODC1 and the pathway link with stemness-promoting cytokines warrants further investigation.

The Role of Pi, Glutamine and the Essential Amino Acids in Modulating the Metabolism in Diabetes and Cancer

Purpose

Re-examine the current metabolic models.

Methods

Review of literature and gene networks.

Results

Insulin activates Pi uptake, glutamine metabolism to stabilise lipid membranes. Tissue turnover maintains the metabolic health. Current model of intermediary metabolism (IM) suggests glucose is the source of energy, and anaplerotic entry of fatty acids and amino acids into mitochondria increases the oxidative capacity of the TCA cycle to produce the energy (ATP). The reduced cofactors, NADH and FADH2, have different roles in regulating the oxidation of nutrients, membrane potentials and biosynthesis. Trans-hydrogenation of NADH to NADPH activates the biosynthesis. FADH2 sustains the membrane potential during the cell transformations. Glycolytic enzymes assume the non-canonical moonlighting functions, enter the nucleus to remodel the genetic programmes to affect the tissue turnover for efficient use of nutrients. Glycosylation of the CD98 (4F2HC) stabilises the nutrient transporters and regulates the entry of cysteine, glutamine and BCAA into the cells. A reciprocal relationship between the leucine and glutamine entry into cells regulates the cholesterol and fatty acid synthesis and homeostasis in cells. Insulin promotes the Pi transport from the blood to tissues, activates the mitochondrial respiratory activity, and glutamine metabolism, which activates the synthesis of cholesterol and the de novo fatty acids for reorganising and stabilising the lipid membranes for nutrient transport and signal transduction in response to fluctuations in the microenvironmental cues. Fatty acids provide the lipid metabolites, activate the second messengers and protein kinases. Insulin resistance suppresses the lipid raft formation and the mitotic slippage activates the fibrosis and slow death pathways.

Ammonia generation by tryptophan synthase drives a key genetic difference between genital and ocular Chlamydia trachomatis isolates

A striking difference between genital and ocular clinical isolates of Chlamydia trachomatis is that only the former express a functional tryptophan synthase and therefore can synthesize tryptophan by indole salvage. Ocular isolates uniformly cannot use indole due to inactivating mutations within tryptophan synthase, indicating a selection against maintaining this enzyme in the ocular environment. Here, we demonstrate that this selection occurs in two steps. First, specific indole derivatives, produced by the human gut microbiome and present in serum, rapidly induce expression of C. trachomatis tryptophan synthase, even under conditions of tryptophan sufficiency. We demonstrate that these indole derivatives function by acting as de-repressors of C. trachomatis TrpR. Second, trp operon de-repression is profoundly deleterious when infected cells are in an indole-deficient environment, because in the absence of indole, tryptophan synthase deaminates serine to pyruvate and ammonia. We have used biochemical and genetic approaches to demonstrate that expression of wild-type tryptophan synthase is required for the bactericidal production of ammonia. Pertinently, although these indole derivatives de-repress the trpRBA operon of C. trachomatis strains with trpA or trpB mutations, no ammonia is produced, and no deleterious effects are observed. Our studies demonstrate that tryptophan synthase can catalyze the ammonia-generating β-elimination reaction within any live bacterium. Our results also likely explain previous observations demonstrating that the same indole derivatives inhibit the growth of other pathogenic bacterial species, and why high serum levels of these indole derivatives are favorable for the prognosis of diseased conditions associated with bacterial dysbiosis.

Optimizing sequential treatment with anti-EGFR and VEGF mAb in metastatic colorectal cancer: current results and controversies

Anti-EGFR mAb (cetuximab or panitumumab) and anti-VEGF mAb (bevacizumab) are the two main targeted agents available for RAS wild-type (WT) metastatic colorectal cancer (mCRC) treatment. Nonetheless, three head-to-head clinical trials evaluating anti-EGFR mAb vs -VEGF mAb in first-line treatment failed to conclude a uniform result. Recently, a few small clinical studies revealed that prior use of bevacizumab may impair the effect of cetuximab or panitumumab. Preclinical studies have also suggested that pretreatment with bevacizumab may lead to simultaneous resistance to anti-EGFR mAb. Therefore, we performed this review to summarize the available data regarding the optimal sequential treatment of anti-EGFR and -VEGF mAb for RAS or KRAS WT mCRC and discuss the potential mechanisms that may explain this phenomenon. Primary tumor location and early tumor shrinkage have emerged as new potential prognostic and predictive factors in mCRC. We also collected information to explore whether these factors affect the optimal sequencing of targeted therapy in mCRC. However, definite conclusions cannot be made, and we can only speculate on optimal treatment recommendations based on the contradictory results.

Macrophage-Derived IL1β and TNFα Regulate Arginine Metabolism in Neuroblastoma

Neuroblastoma is the most common childhood solid tumor, yet the prognosis for high-risk disease remains poor. We demonstrate here that arginase 2 (ARG2) drives neuroblastoma cell proliferation via regulation of arginine metabolism. Targeting arginine metabolism, either by blocking cationic amino acid transporter 1 (CAT-1)-dependent arginine uptake in vitro or therapeutic depletion of arginine by pegylated recombinant arginase BCT-100, significantly delayed tumor development and prolonged murine survival. Tumor cells polarized infiltrating monocytes to an M1-macrophage phenotype, which released IL1β and TNFα in a RAC-alpha serine/threonine-protein kinase (AKT)-dependent manner. IL1β and TNFα established a feedback loop to upregulate ARG2 expression via p38 and extracellular regulated kinases 1/2 (ERK1/2) signaling in neuroblastoma and neural crest-derived cells. Proteomic analysis revealed that enrichment of IL1β and TNFα in stage IV human tumor microenvironments was associated with a worse prognosis. These data thus describe an immune-metabolic regulatory loop between tumor cells and infiltrating myeloid cells regulating ARG2, which can be clinically exploited. SIGNIFICANCE: These findings illustrate that cross-talk between myeloid cells and tumor cells creates a metabolic regulatory loop that promotes neuroblastoma progression.

Hypoxic-induction of arginase II requires EGF-mediated EGFR activation in human pulmonary microvascular endothelial cells

We have previously shown that hypoxia-induced proliferation of human pulmonary microvascular endothelial cells (hPMVEC) depends on arginase II, and that epidermal growth factor receptor (EGFR) is necessary for hypoxic-induction of arginase II. However, it remains unclear how hypoxia activates EGFR-mediated signaling in hPMVEC. We hypothesized that hypoxia results in epidermal growth factor (EGF) production and that EGF binds to EGFR to activate the signaling cascade leading to arginase II induction and proliferation in hPMVEC. We found that hypoxia significantly increased the mRNA levels of EGF, EGFR, and arginase in hPMVEC. Hypoxia significantly increased pEGFR(Tyr845) protein levels and an EGF neutralizing antibody prevented the hypoxic induction of pEGFR. Inhibiting EGFR activation prevented hypoxia-induced arginase II mRNA and protein induction. Treatment of hPMVEC with exogenous EGF resulted in greater levels of arginase II protein both in normoxia and hypoxia. An EGF neutralizing antibody diminished hypoxic induction of arginase II and resulted in fewer viable cells in hPMVEC. Similarly, siRNA against EGF prevented hypoxic induction of arginase II and resulted in fewer viable cells. Finally, conditioned media from hypoxic hPMVEC induced proliferation in human pulmonary artery smooth muscle cells (hPASMC), however, conditioned media from a group of hypoxic hPMVEC in which EGF were knocked down did not promote hPASMC proliferation. These findings demonstrate that hypoxia-induced arginase II expression and cellular proliferation depend on autocrine EGF production leading to EGFR activation in hPMVEC. We speculate that EGF-EGFR signaling may be a novel therapeutic target for pulmonary hypertensive disorders associated with hypoxia.

Hypoxia-induced proliferation of HeLa cells depends on epidermal growth factor receptor-mediated arginase II induction

Solid tumors can often be hypoxic in regions, and cancer cells can respond to hypoxia with an increase in proliferation and a decrease in apoptosis, leading to a net increase in viable cell numbers. We have recently found that in an osteosarcoma cell line, hypoxia-induced proliferation depends on arginase II induction. Epidermal growth factor receptor (EGFR) has been shown to mediate the hypoxia-induced cellular proliferation in some cancer cell lines. We hypothesized that hypoxia-induced proliferation of HeLa cells would depend on arginase II induction and that this induction of arginase II would occur through EGFR activation. Exposure of HeLa cells to hypoxia resulted in an upregulation of arginase II mRNA and protein levels, with no effect on arginase I expression. Hypoxia also resulted in significantly greater viable cell numbers than did normoxia. The hypoxia-induced increase in viable cell numbers was prevented by either a small molecule inhibitor of arginase or siRNA targeting arginase II Overexpression of arginase II resulted in an increase in viable cell numbers both in normoxia and hypoxia. Hypoxia caused a substantial induction of both epidermal growth factor (EGF) and EGFR Preventing hypoxia-induced EGFR expression using siRNA abolished hypoxia-induced arginase II expression and the increase in viable cell numbers. Treatment with EGF in normoxia not only induced arginase II expression but also resulted in an increase in viable cell numbers. Blocking EGF interactions with EGFR using either an EGF neutralizing antibody or an EGFR antibody prevented the hypoxia-induced increase in viable cell numbers. These results demonstrate an EGF/EGFR/arginase II pathway that is necessary for hypoxic proliferation in HeLa cells.

Ataxin-1 is involved in tumorigenesis of cervical cancer cells via the EGFR-RAS-MAPK signaling pathway

Ataxin-1 (ATXN1) is a coregulator protein within which expansion of the polyglutamine tract causes spinocerebellar ataxia type 1, an autosomal dominant neurodegenerative disorder. Previously, we reported that ATXN1 regulates the epithelial–mesenchymal transition of cervical cancer cells. In the present study, we demonstrate that ATXN1 is involved in cervical cancer tumorigenesis by promoting the proliferation of human cervical cancer cells. Chromatin immunoprecipitation assays showed that ATXN1 bound to the promoter region within cyclin D1 and activated cyclin D1 transcription, resulting in cell proliferation. ATXN1 promoted cyclin D1 expression through the EGFR–RAS–MAPK signaling pathway. Mouse xenograft tumorigenicity assays showed that ATXN1 downregulation inhibited tumorigenesis in cervical cancer cell lines in nude mice. Human cervical cancer tissue microarrays and immunohistochemical techniques showed that ATXN1 was significantly upregulated in many such tissues. Our results suggest that ATXN1 plays an important role in cervical cancer tumorigenesis and is a prognostic marker for cervical cancer.