Growth Factor Receptor-mediated Signaling Pathways Research Articles

Frankincense myrrh attenuates hepatocellular carcinoma by regulating tumor blood vessel development through multiple epidermal growth factor receptor-mediated signaling pathways.

BACKGROUNDIn traditional Chinese medicine (TCM), frankincense and myrrh are the main components of the antitumor drug Xihuang Pill. These compounds show anticancer activity in other biological systems. However, whether frankincense and/or myrrh can inhibit the occurrence of hepatocellular carcinoma (HCC) is unknown, and the potential molecular mechanism(s) has not yet been determined.AIMTo predict and determine latent anti-HCC therapeutic targets and molecular mechanisms of frankincense and myrrh in vivo.METHODSIn the present study, which was based on the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (http://tcmspw.com/tcmsp.php), Universal Protein database (http://www.uniprot.org), GeneCards: The Human Gene Database (http://www.genecards.org/) and Comparative Toxicogenomics Database (http://www.ctdbase.org/), the efficacy of and mechanism by which frankincense and myrrh act as anti-HCC compounds were predicted. The core prediction targets were screened by molecular docking. In vivo, SMMC-7721 human liver cancer cells were transplanted as xenografts into nude mice to establish a subcutaneous tumor model, and two doses of frankincense plus myrrh or one dose of an EGFR inhibitor was administered to these mice continuously for 14 d. The tumors were collected and evaluated: the tumor volume and growth rate were gauged to evaluate tumor growth; hematoxylin-eosin staining was performed to estimate histopathological changes; immunofluorescence (IF) was performed to detect the expression of CD31, α-SMA and collagen IV; transmission electron microscopy (TEM) was conducted to observe the morphological structure of vascular cells; enzyme-linked immunosorbent assay (ELISA) was performed to measure the levels of secreted HIF-1α and TNF-α; reverse transcription-polymerase chain reaction (RT-qPCR) was performed to measure the mRNA expression of HIF-1α, TNF-α, VEGF and MMP-9; and Western blot (WB) was performed to determine the levels of proteins expressed in the EGFR-mediated PI3K/Akt and MAPK signaling pathways.RESULTSThe results of the network pharmacology analysis showed that there were 35 active components in the frankincense and myrrh extracts targeting 151 key targets. The molecular docking analysis showed that both boswellic acid and stigmasterol showed strong affinity for the targets, with the greatest affinity for EGFR. Frankincense and myrrh treatment may play a role in the treatment of HCC by regulating hypoxia responses and vascular system-related pathological processes, such as cytokine-receptor binding, and pathways, such as those involving serine/threonine protein kinase complexes and MAPK, HIF-1 and ErbB signaling cascades. The animal experiment results were verified. First, we found that, through frankincense and/or myrrh treatment, the volume of subcutaneously transplanted HCC tumors was significantly reduced, and the pathological morphology was attenuated. Then, IF and TEM showed that frankincense and/or myrrh treatment reduced CD31 and collagen IV expression, increased the coverage of perivascular cells, tightened the connection between cells, and improved the shape of blood vessels. In addition, ELISA, RT-qPCR and WB analyses showed that frankincense and/or myrrh treatment inhibited the levels of hypoxia-inducible factors, inflammatory factors and angiogenesis-related factors, namely, HIF-1α, TNF-α, VEGF and MMP-9. Furthermore, mechanistic experiments illustrated that the effect of frankincense plus myrrh treatment was similar to that of an EGFR inhibitor with regard to controlling EGFR activation, thereby inhibiting the phosphorylation activity of its downstream targets: the PI3K/Akt and MAPK (ERK, p38 and JNK) pathways.CONCLUSIONIn summary, frankincense and myrrh treatment targets tumor blood vessels to exert anti-HCC effects via EGFR-activated PI3K/Akt and MAPK signaling pathways, highlighting the potential of this dual TCM compound as an anti-HCC candidate.

Human sulfatase 1 exerts anti-tumor activity by inhibiting the AKT/ CDK4 signaling pathway in melanoma.

Human sulfatase 1 (hSulf-1) has aryl sulfatase activity. It can reduce the sulfation of cell surface heparan sulfate proteoglycan (HSPG) and inhibit various growth factor receptor-mediated signaling pathways. In most cancers, hSulf-1 is inactivated, which endows cancer cells with increasesed cell proliferation and metastatic activities, inhibition of apoptosis, and decreased sensitivity to radio- and chemotherapy. In this study, we found that hSulf-1 overexpression in melanoma cells can inhibit cell proliferation and induce cell cycle arrest and apoptosis by decreasing the protein kinase B (AKT) phosphorylation and limiting CDK4 nuclear import. We further confirmed that hSulf-1 overexpression can inhibit AKT phosphorylation and CDK4 nuclear localization and retard the growth of melanoma xenograft tumors in nude mice. Overall, hSulf-1 function in melanoma cells provides an ideal molecular treatment target. An important anti-tumor mechanism of hSulf-1 operates by decreasing downstream AKT signaling pathway activity and inhibiting the nuclear import of CDK4.

Endothelium-derived nitric oxide (NO) activates the NO-epidermal growth factor receptor-mediated signaling pathway in bradykinin-stimulated angiogenesis

Nitric oxide (NO) is involved in angiogenesis and stimulates the EGF-R signaling pathway. Stimulation of different endothelial cell lines with bradykinin (BK) activates the endothelial NO synthase (eNOS) and promotes EGF-R tyrosine phosphorylation. Increase in NO production correlated with enhanced phosphorylation of tyrosine residues and S-nitrosylation of the EGF-R. NO-mediated stimulatory effects on tyrosine phosphorylation of the EGF-R, where cGMP independent. Inhibition of soluble guanylyl cyclase followed by BK stimulation of human umbilical vein endothelial cells (HUVECs) did not change tyrosine phosphorylation levels of EGF-R. BK-stimulation of HUVEC promoted S-nitrosylation of the phosphatase SHP-1 and of p21Ras. Phosphorylation and activation of the ERK1/2 MAP kinases mediated by BK was dependent on the activation of the B2 receptor, of the EGF-R, and of p21 Ras. Inhibition of BK-stimulated S-nitrosylation prevented the activation of the ERK1/2 MAP kinases. Furthermore, activated ERK1/2 MAP kinases inhibited internalization of EGF-R by phosphorylating specific Thr residues of its cytoplasmic domain. BK-induced proliferation of endothelial cells was partially inhibited by the NOS inhibitor (L-NAME) and by the MEK inhibitor (PD98059). BK stimulated the expression of vascular endothelial growth factor (VEGF). VEGF expression was dependent on the activation of the EGF-R, the B2 receptor, p21Ras, and on NO generation. A Matrigel®-based in vitro assay for angiogenesis showed that BK induced the formation of capillary-like structures in HUVEC, but not in those cells expressing a mutant of the EGF-R lacking tyrosine kinase activity. Additionally, pre-treatment of BK-stimulated HUVEC with L-NAME, PD98059, and with SU5416, a specific inhibitor of VEGFR resulted in inhibition of in vitro angiogenesis. Our findings indicate that BK-mediated angiogenesis in endothelial cells involves the induction of the expression of VEGF associated with the activation of the NO/EGF-R/p21Ras/ERK1/2 MAP kinases signaling pathway.

Regulation of cigarette smoke‐mediated mucin expression by hypoxia‐inducible factor‐1α via epidermal growth factor receptor‐mediated signaling pathways

Cigarette smoking is strongly implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Mucus hypersecretion is the key manifestation in patients with COPD and mucin 5AC (MUC5AC) is a major component of airway mucus. Hypoxia inducible factor-1 (HIF-1) is a transcriptional factor which can be stimulated to bind to the MUC5AC promoter and induce MUC5AC promoter activation. Previous studies have reported that activation of HIF-1α pathways by cigarette smoke contributes to the development of COPD. We hypothesize that cigarette smoke up-regulates HIF-1α production and HIF-1 activity through epidermal growth factor receptor (EGFR)-activated signal cascades pathways, leading to mucin production in human airway epithelial cells (16HBE). We show that cigarette smoke increases HIF-1α production, HIF-1 activity and MUC5AC expression. These effects are prevented by small interfering RNA (siRNA) for HIF-1α, indicating that cigarette smoke-induced mucin production is HIF-1α-dependent. Cigarette smoke activates extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphatidylinositol 3-kinase (PI3K) signal pathways, both of which are inhibited by gefitinib (an inhibitor of EGFR), suggesting that cigarette smoke-activated signal pathways are mediated by EGFR in 16HBE cells. Furthermore, pretreatment with gefitinib and the pharmacological inhibitors of PI3K (LY294002) and ERK1/2 (PD98059) prevented cigarette smoke-mediated Akt and ERK1/2 phosphorylation responses, HIF-1α production, HIF-1 activity and MUC5AC expression. These observations demonstrate an important role for EGFR-mediated signaling pathways in regulating cigarette smoke-induced HIF-1 activation and MUC5AC expression. Our results suggest that cigarette smoke activates EGFR-mediated signaling pathways, leading to HIF-1α production and HIF-1 activation, resulting in mucin expression in human airway epithelial cells.

The Effect of Secoisolariciresinol Diglucoside and Flaxseed Oil, Alone and in Combination, on MCF-7 Tumor Growth and Signaling Pathways

Flaxseed (FS), an oilseed containing high amounts of the phytoestrogen lignan, secoisolariciresinol diglucoside (SDG), and n-3 fatty acid, α-linolenic acid-rich oil (FO), has been shown to inhibit the growth of established human breast tumors (MCF-7) in ovariectomized (OVX) athymic mice. However, the major FS component responsible for this effect and the mechanism(s) of its action are unclear. Hence, this study determined, in a 2 × 2 factorial design, the effect of SDG and FO, alone or in combination, on the growth of established human estrogen receptor positive (ER+) breast tumors and the potential mechanism(s) of its action. OVX mice with established ER+ human breast tumors (MCF-7) were treated for 8 wk with basal diet (BD, control) or BD supplemented with SDG (1 g/kg), FO (38.5 g/kg), or SDG + FO. All treatments reduced the tumor growth, but SDG had the greatest effect primarily through reducing tumor cell proliferation rather than increasing apoptosis. SDG had a main effect in the reduction of PS2, BCL2, and IGF-1R mRNA expression, whereas FO had a main effect only in PAKT reduction. SDG alone also lowered the ERα, ERβ, EGFR, BCL2 mRNA, and PMAPK protein, indicating that its effect involves the modulation of the ER– and growth factor receptor-mediated signaling pathways.

New Functional Proteins Identified by Proteomic Analysis in the Epidermal Growth Factor Receptor-mediated Signaling Pathway and Application for Practical Use

To clarify the whole picture of epidermal growth factor (EGF) signaling pathway, we identified proteins from the EGF-stimulated A431 cells by anti-phospho-tyrosine antibody column chromatography. Over 150 proteins were detected including previously unidentified proteins as well as well-studied proteins. Among these proteins, we picked up four proteins that had not been known in EGF signaling pathway and analyzed their functions. We report the functions of these proteins in this article. 1) CFBP interacts with CD2AP family proteins and functions as a key component in downregulation of EGF receptor protein level following EGF stimulation. 2) Ymer is found to be phosphorylated and ubiquitinated upon EGF stimulation, and functions as a regulator for the downregulation and endocytosis of EGF receptor. 3) CLPABP binds to mitochondria-specific phospholipids, cardiolipin, through its PH domain, and its complex includes various proteins related to mRNA metabolism. 4) GAREM is associated with Grb2 and Shp2. Each association affects the ERK activity. Finally, we discuss the possibilities that these proteins can be used as a novel biomarker protein for cancer and other diseases.

TRPM8 and prostate cancer: to overexpress or repress, that is the question—comment on “Effects of TRPM8 on proliferation and motility of prostate cancer PC-3 cells” by Yang ZH et al. in Asian Journal of Andrology

The progression of cells from a normal differentiated state in which the rates of proliferation and apoptosis are in check, to a tumorigenic and metastatic state where these rates are imbalanced, likely involves the accumulation of mutations in multiple genes, and the evolution and clonal selection of more aggressive phenotypes. These events are associated with changes in the expression of numerous gene products including the transient receptor potential (TRP) proteins. TRP proteins are a family of Ca2+- and Na+-permeable channels that play a diverse and important role in cellular physiology and pathology. One member of this family, TRPM8, a receptor-activated non-selective cation channel is highly expressed in prostate cancer (PCa) cells and in recent years, has emerged as a promising prognostic marker and putative therapeutic target in PCa. In prostate epithelial cells, expression of TRPM8 is regulated by androgen and is elevated in androgen-sensitive cancerous cells compared with normal cells. While there is some evidence that in PCa cells Ca2+ and Na+ inflow through TRPM8 is necessary for survival and function, the precise function of TRPM8 remains largely unknown. Nonetheless, in the androgen-responsive LNCaP cell line where the TRPM8 protein is expressed in the endoplasmic reticulum and plasma membrane, inhibiting its activity with an antagonist or knocking down its mRNA expression with siRNA results in cell death 1. These results indicate that TRPM8 is an important determinator of Ca2+ homeostasis in prostate epithelial cells and may be a potential pharmaceutical target for androgen-sensitive PCa. In contrast to androgen sensitive PCa, expression of TRPM8 is substantially decreased in androgen-independent and metastatic prostate cancer 2. These observations would imply that the scope of TRPM8 as a therapeutic target may be limited to androgen-sensitive PCA. Not withstanding this apparent limitation, in this issue of the Asian Journal of Andrology, Yang et al. 3 provide exciting new evidence to support a potential therapeutic role for TRPM8 in hormone-refractory PCa (HRPC). Using the androgen-insensitive prostate cell line PC-3 as a model system, the authors demonstrate that although at an extremely low level, PC-3 cells express functional TRPM8 on both endoplasmic reticulum and plasma membrane just like PC-3 cells that overexpress TRPM8 (PC-3-TRPM8). However, overexpression of TRPM8 induced a significant cell cycle arrest in G0/G1 stage and facilitated the apoptosis of cells induced by starvation. Furthermore, TRPM8 significantly inhibited the migration of PC-3-TRPM8 through the inactivation of focal adhesion kinase (FAK). FAK is a non-receptor protein tyrosine kinase that localizes to cellular focal adhesions or cell contacts within the extracellular matrix and participates in growth factor receptor-mediated signaling pathways and plays essential roles in cell survival, proliferation, migration, and invasion. Considered together, Yang et al. 3 provide good evidence that although, TRPM8 may not essential for the survival of androgen-independent PCa cells, overexpression of TRPM8 has negative effects on the proliferation and migration of PC-3 cells. These tantalizing data suggest that overexpressing TRPM8 or perhaps its activation via an agonist may offer novel approaches to treat HRPC. Despite the promise offered by the work of Yang et al. 3, much remains to be learnt about the consequences of TRPM8 inhibition/repression and the mechanism employed to achieve this endpoint especially, with agonists of TRPM8. For example, it is well known that menthol binds and activates the TRPM8 Ca2+-permeable channel that exhibits abnormal expression patterns in PCa, suggesting that TRPM8 links Ca2+ transport pathways to tumor biology. However, a recent study 4 has demonstrated that menthol increases Ca2+(i) via Ca2+ influx mechanism(s) independent of TRPM8 in PC-3 cells. Indeed, menthol increased a phosphorylated form of c-jun Nterminal kinase (JNK) in PC-3 cells through TRPM8-independent mechanisms. Thus, the data indicate that there is an apparent lack of causality between TRPM8 activation and that one could inadvertently uncouple TRPM8 activation and cell death. Finally, Yang et al. 3 do not explain why the rat and not human TRPM8 cDNA was used in their study. Given the high prevalence of PCa, aging of the population, and potential morbidity of treatment, there is a dire need for novel therapeutics to treat HRPC. Recently, the Getzenberg laboratory 5, 6 demonstrated that overexpression of yet another protein, the purine-rich element binding protein (PUR) alpha, is down-regulated the androgen-independent PC3 and DU145 cells. Interestingly, the authors found that like in the case of TRPM8, overexpressing PURα also negatively regulates cell proliferation, resulting in decreases in PCNA expression both in vitro and in vivo. Although it is clear that additional studies are required to assess the role of TRPM8 and PURα in HRPC and to advance them to the clinic, these novel approaches appear to have considerable promise in the near future. But unlike Prince Hamlet's dilemma in the famed play Hamlet, we may be able to answer this dilemma; overexpress TRPM8/PUR α to treat HRPC but repress them in androgen-sensitive PCa.

Activation of Growth Factor Receptors in Esophageal Cancer—Implications for Therapy

Esophageal cancer is a highly aggressive disease and is the seventh most common cause of cancer-related death in the western world. Worldwide, it ranks as the sixth most frequent cause of cancer death. Despite advances in surgical techniques and treatment, the prognosis of esophageal cancer remains poor, with very few long-term survivors. The need for novel strategies to detect esophageal cancer earlier and to improve current therapy is urgent. It is well established that growth factors and growth factor receptor-mediated signaling pathways are important components of the transformation process in many forms of cancer, including esophageal cancer. With the recent advances in drug development, there are emerging possibilities to use growth factor signal transduction pathways in targeted therapy. This review provides a summary of the role of growth factors and their receptors in esophageal cancer and discusses their potential roles as biomarkers and as targets in therapy.

Suppression of the Ligand-mediated Down-regulation of Epidermal Growth Factor Receptor by Ymer, a Novel Tyrosine-phosphorylated and Ubiquitinated Protein

The ligand-mediated down-regulation of the growth factor receptors is preceded by the involvement of various other factors. In particular, a ubiquitin ligase, Cbl, plays a central role in this event. Several candidates that have potential effects on the negative control of the epidermal growth factor (EGF) receptor have now been identified by our recent studies in phospho-proteomics. Among these molecules, we focus on characterizing a novel protein, Ymer, which is a tyrosine-phosphorylated and ubiquitinated protein. Ymer is found to be phosphorylated at tyrosine 145 and 146 upon EGF stimulation, and lysine 129 of Ymer has been identified as a ubiquitination site. Ymer has two motifs interacting with the ubiquitin (MIU) domains that might function as a binding site for the ubiquitinated EGF receptor. Although Ymer and EGF receptors are associated in an EGF-dependent manner, their interaction is required not only for MIU domains but also for the tyrosine phosphorylation of Ymer. Phosphorylated Ymer is mainly located at the plasma membrane with EGF receptor and functions in its endocytosis and degradation. Furthermore, EGF-mediated secondary modifications of an activated-EGF receptor are inhibited by overexpressing Ymer in COS7 cells. Therefore, Ymer may have competitive effects on the activation of the EGF receptor. Our findings suggest that Ymer functions as a novel inhibitor for the down-regulation of the EGF receptor and plays a crucial role for regulating the amount of the EGF receptor on the cell surface membrane.

N-methyl- N′-nitro- N-nitrosoguanidine interferes with the epidermal growth factor receptor-mediated signaling pathway

Many environmental factors, such as ultraviolet (UV) and arsenic, can induce the clustering of cell surface receptors, including epidermal growth factor receptor (EGFR). This is accompanied by the phosphorylation of the receptors and the activation of ensuing cellular signal transduction pathways, which are implicated in the various cellular responses caused by the exposure to these factors. In this study, we have shown that N-methyl- N′-nitro- N-nitrosoguanidine (MNNG), an alkylating agent, also induced the clustering of EGFR in human amnion FL cells, which was similar in morphology to that of epidermal growth factor treatment. However, MNNG treatment did not activate Ras, the downstream mediator in EGFR signaling pathway, as compared to EGF treatment. The autophosphorylation of tyrosine residues Y1068 and Y1173 at the intracellular domain of EGFR, which is related to Ras activation under EGF treatment, was also not observed by MNNG exposure. Interestingly, although MNNG did not affect the binding of EGF to EGFR, MNNG can interfere with EGF function. For instance, pre-incubating FL cells with MNNG inhibited the autophosphorylation of EGFR by EGF treatment, as well as the activation of Ras. In addition, the phosphorylation of Y845 on EGFR by EGF, which is mediated through c-Src or related kinases but not autophosphorylation, was also affected by MNNG. Therefore, MNNG may influence the tyrosine kinase activity as well as the phosphorylation of EGFR through its interaction with EGFR.

Commitment and differentiation of lung cell lineages

To form a large diffusible interface capable of conducting respiratory gases to and from the circulation, the lung must undergo extensive cell proliferation, branching morphogenesis, and alveolar saccule formation, to generate sufficient surface area. In addition, the cells must differentiate into at least 40 distinct lung cell lineages. Specific transcriptional factors, peptide growth factor receptor-mediated signaling pathways, extracellular matrix components, and integrin-signaling pathways interact to direct lung morphogenesis and lung cell lineage differentiation. Branching mutants of the respiratory tracheae in Drosophila have identified several functionally conserved genes in the fibroblast growth factor signaling pathway that also regulate pulmonary organogenesis in mice and probably also in man. Key transcriptional factors including Nkx2.1, hepatocyte nuclear factor family forkhead homologues, GATA family zinc finger factors, pou and homeodomain proteins, as well as basic helix-loop-helix factors, serve as master genes to integrate the developmental genetic instruction of lung morphogenesis and cell lineage determination. Lung mesenchyme serves as a 'compleat' inducer of lung morphogenesis by secreting soluble peptide growth factors. In general, peptide growth factors signaling through cognate receptors with tyrosine kinase intracellular signaling domains such as epidermal growth factor receptor, fibroblast growth factor receptors, hepatocyte growth factor/scatter factor receptor, c-met, insulin-like growth factor receptor, and platelet-derived growth factor receptor, stimulate lung morphogenesis, while the cognate receptors with serine/threonine kinase intracellular signaling domains, such as the transforming growth factor-beta receptor family are inhibitory. The extracellular matrix also plays a key role in determining branching morphogenesis. Pulmonary neuroendocrine (PNE) cells differentiate earliest in gestation among lung epithelial cells. PNE cells are principally derived from endoderm and not neural crest. PNE cells have been proposed to function as airway chemoreceptors, while PNE cell secretory granules contain many bioactive substances such as GRP which may direct proliferation of adjacent epithelial cells. Mammalian achaete-schute homolog-1 null mutant mice do not develop PNE cells. Candidate molecular switches in the transition from a quiescent to a proliferative alveolar epithelial cell (AEC) phenotype and back again following acute hyperoxia, include autocrine peptide growth factor signaling pathways and cell cycle regulatory elements. AEC type 2 also appear capable of reversible transdifferentiation into AEC type 1 and intermediate phenotypes in response to cues from extracellular matrix and cell shape, as well as soluble factors. Evidence for expression of telomerase by alveolar epithelial stem cells, which correlates with self-renewal potential, is now beginning to emerge. Lung regeneration following lobectomy in juvenile rodents is associated with co-ordinated cell proliferation, re-expression of elastin and formation of alveoli. Retinoic acid has recently shown promise as a stimulator of alveolization in juvenile rats. Our future goal is to devise new rational and gene therapeutic strategies to stimulating lung growth and maturation, ameliorating lung injury, augmenting lung repair, and inducing lung regeneration. The ideal agent or agents would therefore mimic the instructive role of lung mesenchyme, correctly inducing the temporospatial pattern of lung cell lineages necessary to restore pulmonary gas diffusing capacity.