Altered Lipid Domains Facilitate Enhanced Pulmonary Vasoconstriction after Chronic Hypoxia.

Chronic hypoxia (CH) augments depolarization-induced pulmonary vasoconstriction through superoxide-dependent, Rho kinase-mediated Ca2+ sensitization. Nicotinamide adenine dinucleotide phosphate oxidase and EGFR (epidermal growth factor receptor) signaling contributes to this response. Caveolin-1 regulates the activity of a variety of proteins, including EGFR and nicotinamide adenine dinucleotide phosphate oxidase, and membrane cholesterol is an important regulator of caveolin-1 protein interactions. We hypothesized that derangement of these membrane lipid domain components augments depolarization-induced Ca2+ sensitization and resultant vasoconstriction after CH. Although exposure of rats to CH (4 wk, ∼380 mm Hg) did not alter caveolin-1 expression in intrapulmonary arteries or the incidence of caveolae in arterial smooth muscle, CH markedly reduced smooth muscle membrane cholesterol content as assessed by filipin fluorescence. Effects of CH on vasoreactivity and superoxide generation were examined using pressurized, Ca2+-permeabilized, endothelium-disrupted pulmonary arteries (∼150 µm inner diameter) from CH and control rats. Depolarizing concentrations of KCl evoked greater constriction in arteries from CH rats than in those obtained from control rats, and increased superoxide production as assessed by dihydroethidium fluorescence only in arteries from CH rats. Both cholesterol supplementation and the caveolin-1 scaffolding domain peptide antennapedia-Cav prevented these effects of CH, with each treatment restoring membrane cholesterol in CH arteries to control levels. Enhanced EGF-dependent vasoconstriction after CH similarly required reduced membrane cholesterol. However, these responses to CH were not associated with changes in EGFR expression or activity, suggesting that cholesterol regulates this signaling pathway downstream of EGFR. We conclude that alterations in membrane lipid domain signaling resulting from reduced cholesterol content facilitate enhanced depolarization- and EGF-induced pulmonary vasoconstriction after CH.

Colorectal cancer spheroid biobanks: multi-level approaches to drug sensitivity studies.

Biobanking of molecularly characterized colorectal cancer stem cells (CSCs) generated from individual patients and growing as spheroids in defined serum-free media offer a fast, feasible, and multi-level approach for the screening of targeted therapies and drug resistance molecular studies. By combining in vitro and in vivo analyses of cetuximab efficacy with genetic data on an ongoing collection of stem cell-enriched spheroids, we describe the identification and preliminary characterization of microsatellite stable (MSS) CSCs that, despite the presence of the KRAS (G12D) mutation, display epidermal growth factor (EGF)-dependent growth and are strongly inhibited by anti-EGF-receptor (EGFR) treatment. In parallel, we detected an increased resistance to anti-EGFR therapy of microsatellite instable (MSI) CSC lines irrespective of KRAS mutational status. MSI CSC lines carried mutations in genes coding for proteins with a role in RAS and calcium signaling, highlighting the role of a genomically unstable context in determining anti-EGFR resistance. Altogether, these results argue for a multifactorial origin of anti-EGFR resistance that emerges as the effect of multiple events targeting direct and indirect regulators of the EGFR pathway. An improved understanding of key molecular determinants of sensitivity/resistance to EGFR inhibition will be instrumental to optimize the clinical efficacy of anti-EGFR agents, representing a further step towards personalized treatments.

New insights into sorafenib resistance in hepatocellular carcinoma: Responsible mechanisms and promising strategies.

It is disappointing that only a few patients with hepatocellular carcinoma (HCC) obtain a significant survival benefit from the sorafenib treatment, which is currently regarded as a first-line chemotherapeutic therapy in patients with advanced HCC. Most patients are highly refractory to this therapy. Therefore, it is necessary to identify resistant factors and explore potential protocols that can be used to overcome the resistance or substitute sorafenib once the resistance is formed. In fact, a growing body of studies has been focusing on the resistance mechanisms or the method to overcome it. The limitation of sorafenib efficacy has been partially but not fully elucidated. Moreover, some protocols have shown encouraging outcomes but still need to be further verified in clinical trials. In this review, we summarize the recent findings on the potential mechanisms that contribute to sorafenib resistance and discuss strategies that can be used to improve the treatment outcome.

A Flavonoid Glycoside Compound from Murraya paniculata (L.) Interrupts Metastatic Characteristics of A549 Cells by Regulating STAT3/NF-κB/COX-2 and EGFR Signaling Pathways.

Metastasis remains the leading cause of death from lung carcinoma. It is urgent to find safe and efficient pre-metastasis preventive agents for cancer survivors. We isolated a flavonoid glycoside, hexamethoxy flavanone-o-[rhamnopyranosyl-(1 â†’ 4)-rhamnopyranoside (HMFRR), from the traditional Chinese medicine (TCM) Murraya paniculata (L.) that can effectively inhibit the adhesion, migration, and invasion of lung adenocarcinoma A549 cells in vitro. Molecular and cellular studies demonstrated that HMFRR significantly downregulated the expressions of cell adhesion-related and invasion-related molecules such as integrin ß1, EGFR, COX-2, MMP-2, and MMP-9 proteins. Additionally, HMFRR effectively downregulated the expressions of epithelial-mesenchymal transition (EMT) markers (N-cadherin and vimentin) and upregulated that of E-cadherin. Moreover, these inhibitions were mediated by interrupting STAT3/NF-κB/COX-2 and EGFR/PI3K/AKT signaling pathways. Furthermore, HMFRR counteracted the expressions of cell adhesion molecules (ICAM-1, VCAM-1, and E-selectin) stimulated by interleukin-1ß in human pulmonary microvascular endothelial cells (HPMECs). As a result, HMFRR interrupted the adhesion of A549 cells to HPMECs. Collectively, these results indicate that HMFRR may become a good candidate for cancer metastatic chemopreventive agents by interrupting the STAT3/NF-κB/COX-2 and EGFR signaling pathways.

Function and mechanism of neurotensin (NTS) and its receptor 1 (NTSR1) in occurrence and development of tumors.

As a neuropeptide, neurotensin (NTS) is widely expressed in central and peripheral nervous system, which is mainly mediated byneurotensin receptor1 (NTSR1) to activate the related downstream signaling pathways. After summarized the function and mechanism of NTS/NTSR1 in various malignant tumors, we found that NTS/NTSR1 played essential roles during tumor initiation and development. NTS/NTSR1 regulates tumor initiation, proliferation, apoptosis, metastasis and differentiation mainly through three pathways, including IP3/Ca2+ /PKC/MAPKs pathway, MMPs/EGFR/MAPKs (PI3K/Akt) pathway, or Rho-GTPsaes and non-receptor tyrosine kinase pathway. Besides, NTS/NTSR1 is also regulated by some upstream pathways and some traditional Chinese medicine preparations and traditional Chinese medicine therapies. In this article, we summarized the function of NTS/NTSR1 and its mechanisms, and discussed the prospective in its application to clinical diagnosis and drugs targeting.

Moderate inappropriately high aldosterone/NaCl constellation in mice: cardiovascular effects and the role of cardiovascular epidermal growth factor receptor.

Non-physiological activation of the mineralocorticoid receptor (MR), e.g. by aldosterone under conditions of high salt intake, contributes to the pathogenesis of cardiovascular diseases, although beneficial effects of aldosterone also have been described. The epidermal growth factor receptor (EGFR) contributes to cardiovascular alterations and mediates part of the MR effects. Recently, we showed that EGFR is required for physiological homeostasis and function of heart and arteries in adult animals. We hypothesize that moderate high aldosterone/NaCl, at normal blood pressure, affects the cardiovascular system depending on cardiovascular EGFR. Therefore we performed an experimental series in male and female animals each, using a recently established mouse model with EGFR knockout in vascular smooth muscle cells and cardiomyocytes and determined the effects of a mild-high aldosterone-to-NaCl constellation on a.o. marker gene expression, heart size, systolic blood pressure, impulse conduction and heart rate. Our data show that (i) cardiac tissue of male but not of female mice is sensitive to mild aldosterone/NaCl treatment, (ii) EGFR knockout induces stronger cardiac disturbances in male as compared to female animals and (iii) mild aldosterone/NaCl treatment requires the EGFR in order to disturb cardiac tissue homeostasis whereas beneficial effects of aldosterone seem to be independent of EGFR.

Oleanolic acid isolated from ethanolic extract of Phytolacca decandra induces apoptosis in A375 skin melanoma cells: drug-DNA interaction and signaling cascade.

OBJECTIVE: Oleanolic acid (OA) has been reported to have anticancer effects, but the extent of its cytotoxicity, its ability to interact with nuclear DNA, its action against skin melanoma, as well as the molecular mechanism of its action against cell proliferation and in support of cell death are still unexplored. This led us to examine the efficacy of OA, a bioactive compound isolated from Phytolacca decandra, on these issues in the present investigation. METHODS: Studies related to analyses of cell viability, drug-DNA interaction, cell proliferation, cell cycle and epidermal growth factor receptor (EGFR) activity were performed. To investigate whether cells undergo apoptosis, studies like fluorescence microscopy, poly (ADP-ribose) polymerase (PARP) degradation, annexin V-fluorescein isothiocyanate/propidium iodide assay, alteration in mitochondrial membrane potential and activity of some relevant signaling proteins were performed. RESULTS: OA displayed a minimal and negligible cytotoxic effect on normal HaCaT cells (skin keratinocytes) and peripheral blood mononuclear cells but by contrast it reduced A375 cell viability significantly. OA interacted with nuclear DNA quickly after exposure. It acted as an anti-proliferative agent. It suppressed EGFR activity. OA administration led the cells to mitochondria-dependent caspase 3-mediated apoptosis. CONCLUSION: OA interacts with cellular DNA, inhibits proliferation possibly through modulating EGFR activity and induces mitochondria-dependent caspase 3-mediated apoptosis in A375 cells which would qualify it as a potent anticancer agent.

EGFR signaling-dependent inhibition of glioblastoma growth by ginsenoside Rh2.

Glioblastoma is the most common and most aggressive malignant primary brain tumor in humans, accounting for 52 % of all functional tissue brain tumor cases and 20 % of all intracranial tumors. The typical treatment involves a combination of chemotherapy, radiation, and surgery, whereas it still achieves fairly poor patient survival. Ginsenoside Rh2 has been reported to have a therapeutic effect on some tumors, but its effect on glioblastoma has not been extensively evaluated. Here, we show that ginsenoside Rh2 can substantially inhibit the growth of glioblastoma in vitro and in vivo in a mouse model. Moreover, the inhibition of the tumor growth appears to result from combined effects on decreased tumor cell proliferation and increased tumor cell apoptosis. Further analyses suggest that ginsenoside Rh2 may have its antiglioblastoma effect through inhibition of the epidermal growth factor receptor (EGFR) signaling pathway in tumor cells. In a lose-of-function experiment, recombinant EGFR was given together with ginsenoside Rh2 to the tumor cells in vitro and in vivo, which completely blocked the antitumor effects of ginsenoside Rh2. Thus, our data not only reveal an anti-glioblastoma effect of ginsenoside Rh2 but also demonstrate that this effect may function via inhibition of EGFR signaling in glioblastoma cells.

Bile acid at low pH reduces squamous differentiation and activates EGFR signaling in esophageal squamous cells in 3-D culture.

BACKGROUND: Barrett's esophagus is a preneoplastic metaplasia in which the normal squamous epithelium of the esophagus changes to an intestinal, columnar phenotype due to long-term gastro-esophageal reflux. The major components of this reflux are bile and stomach acid. Previous in vitro studies on the effect of bile and acid on esophageal cells have predominantly relied on transformed esophageal squamous cells or cancer cells grown in monolayer culture. DISCUSSION: In this study, we expanded our previous work using an immortalized primary esophageal squamous cell line (EPC1). We demonstrate that EPC1 cells form a multi-layer, stratified epithelium when grown on polyester transwell filters in media supplemented with calcium. When exposed to short pulses of bile and pH 5, but not either condition alone, EPC1 cells demonstrate a reduction in stratification layers and reduced expression of squamous epithelium-specific genes. Bile at pH 5 also causes activation of epidermal growth factor receptor and down-stream pathways. Blocking epidermal growth factor receptor activation partially attenuates the effects of bile acid and pH 5. These results suggest that bile at low pH, but not bile or low pH alone, promotes loss of differentiation status of stratified squamous esophageal epithelium in vitro, possibly by initiating a mucosal repair response through epidermal growth factor activation.

Epidermal growth factor receptor expression and signaling are essential in glutamine's cytoprotective mechanism in heat-stressed intestinal epithelial-6 cells.

Epidermal growth factor receptor (EGFR) expression and signaling can induce cellular protection after intestinal inflammation. L-Glutamine (GLN) is known to prevent apoptosis after intestinal injury by activating MAPK and phosphatidylinositol 3-kinase (PI3-K)/Akt pathways. However, the role of EGFR expression and signaling in GLN-mediated cellular protection in intestinal epithelial-6 (IEC-6) cells after heat stress (HS) is unknown. To address the role of EGFR in GLN-mediated protection, IEC-6 cells were treated with GLN in the presence or absence of EGFR small interfering RNA, the EGFR tyrosine kinase inhibitor AG1478, the ERK1/2 inhibitor PD98059, the p38MAPK inhibitor SB203580, or the PI3-K/Akt inhibitor LY294002 under basal and HS conditions. GLN-mediated cell survival was measured using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. Phosphorylated and/or total levels of EGFR, cleaved caspase-3, poly(ADP-ribose) polymerase-1, ERK1/2, p38MAPK, and Akt were assessed by Western blotting. We showed that HS induced a decrease in total, cytoplasmic, and nuclear EGFR levels in IEC-6 cells, which was prevented by GLN supplementation, leading to attenuated apoptosis via EGFR small interfering RNA. Furthermore, the protective effect of GLN was lessened by AG1478, PD98059, and LY294002 but was not affected by SB203580. AG1478 attenuated GLN-mediated increases in ERK1/2 and decreases in p38MAPK phosphorylation. However, AG1478 had no effect on GLN-mediated augmentations in Akt phosphorylation. In summary, EGFR expression was important in the protective mechanism of GLN, as well as GLN-mediated activation of EGFR tyrosine kinase activity. GLN-mediated EGFR signaling activated ERK1/2 and decreased p38MAPK signaling. However, GLN-mediated Akt phosphorylation after HS seems to be independent of EGFR signaling.

Suppressive effects of SuHeXiang Wan on amyloid-ß42-induced extracellular signal-regulated kinase hyperactivation and glial cell proliferation in a transgenic Drosophila model of Alzheimer's disease.

SuHeXiang Wan (SHXW), a Chinese traditional medicine, has been used to treat infantile convulsions, seizures and strokes. Previously, we reported that modified SHXW, called KSOP1009, suppressed the hyper-activation of c-Jun N-terminal kinase (JNK) and Alzheimer's disease (AD)-like phenotypes in amyloid-ß42 (Aß42)-expressing Drosophila AD models. In the present study, we, further, investigated the detailed mechanism by which KSOP1009 suppresses the AD-like phenotypes of the model flies. As seen in the brains of AD patients, pan-neuronal expression of Aß42 in Drosophila increased activation of extracellular signal-regulated kinase (ERK), which was monitored by its phosphorylation level, and the number of glial cells in the brain. Suppression of caspase activity did not affect these phenomena, suggesting that Aß42 induces ERK activation and glial cell proliferation independently of apoptotic processes. KSOP1009 intake significantly reduced the level of ERK activation and the number of glial cells. Moreover, KSOP1009 intake also effectively decreased the defects in the wing vein formation induced by Epidermal growth factor receptor (Egfr) overexpression in fly wings, suggesting that it may contain an inhibitory substance that inhibits the EGFR/ERK signaling pathway. In addition, the Aß42-induced locomotive defect was partially rescued by inhibition of the elevated ERK activity through its antagonistic drug treatment. Taken together, these results suggest that KSOP1009 exerts its therapeutic effect by inhibiting the EGFR/ERK pathway and glial cell proliferation and by suppressing the JNK pathway and apoptosis.

Epidermal growth factor upregulates endometrial CYR61 expression via activation of the JAK2/STAT3 pathway.

Endometrial cysteine-rich protein 61 (CYR61, CCN1) is a growth factor-inducible gene whose expression is elevated during the proliferative phase of the menstrual cycle and which has been implicated in the pathogenesis of endometriosis. This study aimed to define the mediators of epidermal growth factor (EGF) signalling on CYR61 expression in spontaneously immortalised human endometrial epithelial cells (HES) as a model system. After 30 min of EGF treatment, the receptor was phosphorylated and internalised as well as mRNA CYR61 increased in HES cells. However, neither inhibition of C-terminal EGF receptor (EGFR)-phosphorylation nor blockage of the mitogen-activated proteinkinase/extracellular signal-regulated kinase (MAPK/ERK) pathway was able to reduce CYR61 levels. Surprisingly, the HES cells showed upregulation of CYR61 mRNA expression after inhibition of the MAPK/ERK pathway when treated with EGF. Specific inhibitor studies identified the contribution of Janus kinase 2 (JAK2) and the signal transducer and activator of transcription protein STAT3 to the regulation of CYR61 expression. The JAK2/STAT3 interaction contributed to the basal expression of CYR61 and mediated EGF-driven regulation of CYR61 after 30 and 120 min of treatment. In summary, EGF-mediated CYR61 upregulation in HES cells involves STAT3 and is counter-regulated by the EGFR/MAPK/ERK pathway.

Inhibition of epidermal growth factor receptor tyrosine kinase ameliorates collagen-induced arthritis.

Rheumatoid arthritis (RA) is an autoimmune synovitis characterized by the formation of pannus and the destruction of cartilage and bone in the synovial joints. Although immune cells, which infiltrate the pannus and promote inflammation, play a prominent role in the pathogenesis of RA, other cell types also contribute. Proliferation of synovial fibroblasts, for example, underlies the formation of the pannus, while proliferation of endothelial cells results in neovascularization, which supports the growth of the pannus by supplying it with nutrients and oxygen. The synovial fibroblasts also promote inflammation in the synovium by producing cytokines and chemokines. Finally, osteoclasts cause the destruction of bone. In this study, we show that erlotinib, an inhibitor of the tyrosine kinase epidermal growth factor receptor (EGFR), reduces the severity of established collagen-induced arthritis, a mouse model of RA, and that it does so by targeting synovial fibroblasts, endothelial cells, and osteoclasts. Erlotinib-induced attenuation of autoimmune arthritis was associated with a reduction in number of osteoclasts and blood vessels, and erlotinib inhibited the formation of murine osteoclasts and the proliferation of human endothelial cells in vitro. Erlotinib also inhibited the proliferation and cytokine production of human synovial fibroblasts in vitro. Moreover, EGFR was highly expressed and activated in the synovium of mice with collagen-induced arthritis and patients with RA. Taken together, these findings suggest that EGFR plays a central role in the pathogenesis of RA and that EGFR inhibition may provide benefits in the treatment of RA.

Colon-specific delivery of a probiotic-derived soluble protein ameliorates intestinal inflammation in mice through an EGFR-dependent mechanism.

Probiotic bacteria can potentially have beneficial effects on the clinical course of several intestinal disorders, but our understanding of probiotic action is limited. We have identified a probiotic bacteria-derived soluble protein, p40, from Lactobacillus rhamnosus GG (LGG), which prevents cytokine-induced apoptosis in intestinal epithelial cells. In the current study, we analyzed the mechanisms by which p40 regulates cellular responses in intestinal epithelial cells and p40's effects on experimental colitis using mouse models. We show that the recombinant p40 protein activated EGFR, leading to Akt activation. Activation of EGFR by p40 was required for inhibition of cytokine-induced apoptosis in intestinal epithelial cells in vitro and ex vivo. Furthermore, we developed a pectin/zein hydrogel bead system to specifically deliver p40 to the mouse colon, which activated EGFR in colon epithelial cells. Administration of p40-containing beads reduced intestinal epithelial apoptosis and disruption of barrier function in the colon epithelium in an EGFR-dependent manner, thereby preventing and treating DSS-induced intestinal injury and acute colitis. Furthermore, p40 activation of EGFR was required for ameliorating colon epithelial cell apoptosis and chronic inflammation in oxazolone-induced colitis. These data define what we believe to be a previously unrecognized mechanism of probiotic-derived soluble proteins in protecting the intestine from injury and inflammation.

From probiotics to therapeutics: another step forward?

Preclinical studies with probiotics continue to unravel mechanisms of cytoprotection and suggest that approaches utilizing microbial products as therapeutics in acute and chronic gastrointestinal disorders could be effective. However, clinical trials using these bacteria have thus far been inconsistent. In this issue of the JCI, Yan et al. describe a novel mechanism of cytoprotection by p40, a soluble product of Lactobacillus rhamnosus GG, mediated via EGFR. The efficacy of p40 in three models of chemically induced colitis indicates tremendous therapeutic potential, though this finding will need to be verified in human patients.

Gomisin N enhances TNF-α-induced apoptosis via inhibition of the NF-κB and EGFR survival pathways.

Tumor necrosis factor (TNF-α) is a pleiotropic cytokine that plays an important role in the control of cell proliferation, differentiation, and apoptosis. TNF-α-induced apoptosis is limited by TAK1-mediated activation of NF-κB (mainly p65-p50 hetrodimer) signaling pathway. We have recently reported that TAK1 regulates phosphorylation of EGFR at Ser-1046/7 through p38 MAPK, which cooperates with NF-κB in TNF-α-induced apoptosis. The present study investigated the effect of gomisins A and N, dibenzocyclooctadiene lignans isolated from the fruit of Schisandra chinensis, on TNF-α-induced apoptosis in HeLa cells. Gomisins A and N strongly promoted TNF-α-induced cleavage of caspase-3 and PARP-1, which are key markers of apoptosis. We found that gomisin N, but not gomisin A, inhibited the TNF-α-induced activation of NF-κB by suppressing the activation of IKKα. Gomisin N also inhibited p38-mediated phosphorylation of the EGFR at Ser-1046/7 and subsequent endocytosis of EGFR, another prosurvival pathway. The findings suggested that gomisin N enhanced TNF-α-induced apoptosis by suppressing of NF-κB and EGFR signaling pathways.

ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system.

Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders.

Antiproliferative effect of growth hormone-releasing hormone (GHRH) antagonist on ovarian cancer cells through the EGFR-Akt pathway.

BACKGROUND: Antagonists of growth hormone-releasing hormone (GHRH) are being developed for the treatment of various human cancers. METHODS: MTT assay was used to test the proliferation of SKOV3 and CaOV3. The splice variant expression of GHRH receptors was examined by RT-PCR. The expression of protein in signal pathway was examined by Western blotting. siRNA was used to block the effect of EGFR. RESULTS: In this study, we investigated the effects of a new GHRH antagonist JMR-132, in ovarian cancer cell lines SKOV3 and CaOV3 expressing splice variant (SV)1 of GHRH receptors. MTT assay showed that JMR-132 had strong antiproliferative effects on SKOV3 and CaOV3 cells in both a time-dependent and dose-dependent fashion. JMR-132 also induced the activation and increased cleaved caspase3 in a time- and dose-dependent manner in both cell lines. In addition, JMR-132 treatments decreased significantly the epidermal growth factor receptor (EGFR) level and the phosphorylation of Akt (p-Akt), suggesting that JMR-132 inhibits the EGFR-Akt pathway in ovarian cancer cells. More importantly, treatment of SKOV3 and CaOV3 cells with 100 nM JMR-132 attenuated proliferation and the antiapoptotic effect induced by EGF in both cell lines. After the knockdown of the expression of EGFR by siRNA, the antiproliferative effect of JMR-132 was abolished in SKOV3 and CaOV3 cells. CONCLUSIONS: The present study demonstrates that the inhibitory effect of the GHRH antagonist JMR-132 on proliferation is due, in part, to an interference with the EGFR-Akt pathway in ovarian cancer cells.

Acquired resistance of non-small cell lung cancer cells to MET kinase inhibition is mediated by a switch to epidermal growth factor receptor dependency.

Cancer cells harboring MET amplification display striking sensitivity to selective small molecule inhibitors of MET kinase, prompting their clinical evaluation. Similar to the experience with traditional therapeutics, most patients responding to treatment with such molecular targeted therapeutics ultimately relapse with drug-resistant disease. In this study we modeled acquired resistance to experimental MET kinase inhibitor PF2341066 in MET-amplified non-small cell lung carcinoma (NSCLC) cell lines to identify drug resistance mechanisms that may arise in clinic. We found that activation of the epidermal growth factor receptor (EGFR) pathway emerges as a resistance mechanism in MET-amplified cells after prolonged exposure to PF2341066. Whereas combined inhibition of MET and EGFR kinases in MET-dependent NSCLC cells did not enhance their initial sensitivity to PF2341066, this combination dramatically suppressed the eventual emergence of drug-resistant clones after prolonged drug exposure. Conversely, activation of the EGFR pathway increased the yield of PF2341066-resistant clones, confirming the significance of this pathway in conferring resistance. Our findings support an intimate relationship between the EGFR and MET signaling pathways in NSCLC, and they suggest that combination treatment with MET and EGFR kinase inhibitors may be beneficial in MET-amplified NSCLC by reducing selection for drug resistant clones.

Ganoderma tsugae extract inhibits expression of epidermal growth factor receptor and angiogenesis in human epidermoid carcinoma cells: In vitro and in vivo.

We examined the anti-angiogenic effects of Ganoderma tsugae methanol extract (GTME) on human epidermoid carcinoma A-431 cells. Our data indicate that GTME inhibits the expression of epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) in vitro and in vivo, and also inhibits the capillary tube formation of human umbilical vein endothelial cells (HUVECs). We also show that the suppression of VEGF expression by GTME can be restored by treatment with EGF. These results suggest that GTME inhibits VEGF expression via the suppression of EGFR expression, resulting in the downregulation of VEGF secretion from epidermoid carcinoma A-431 cells. These findings reveal a novel role for G. tsugae in inhibiting EGFR and VEGF expression, which are important for tumor angiogenesis and growth. Thus, GTME may provide a potential therapeutic approach for anti-tumor treatment.