Activation of epidermal growth factor receptor in the early phase after renal ischemia-reperfusion in rat

Potential targeted therapy and diagnosis based on novel insight into growth factors, receptors, and downstream effectors in acute kidney injury and acute kidney injury-chronic kidney disease progression

Acute kidney injury (AKI) is defined as a rapid decline in renal function and is characterized by excessive renal inflammation and programmed death of resident cells. AKI shows high morbidity and mortality, and severe or repeated AKI can transition to chronic kidney disease (CKD) or even end-stage renal disease (ESRD); however, very few effective and specific therapies are available, except for supportive treatment. Growth factors, such as epidermal growth factor (EGF), insulin-like growth factor (IGF), and transforming growth factor-β (TGF-β), are significantly altered in AKI models and have been suggested to play critical roles in the repair process of AKI because of their roles in cell regeneration and renal repair. In recent years, a series of studies have shown evidence that growth factors, receptors, and downstream effectors may be highly involved in the mechanism of AKI and may function in the early stage of AKI in response to stimuli by regulating inflammation and programmed cell death. Moreover, certain growth factors or correlated proteins act as biomarkers for AKI due to their sensitivity and specificity. Furthermore, growth factors originating from mesenchymal stem cells (MSCs) via paracrine signaling or extracellular vesicles recruit leukocytes or repair intrinsic cells and may participate in AKI repair or the AKI-CKD transition. In addition, growth factor-modified MSCs show superior therapeutic potential compared to that of unmodified controls. In this review, we summarized the current therapeutic and diagnostic strategies targeting growth factors to treat AKI in clinical trials. We also evaluated the possibilities of other growth factor-correlated molecules as therapeutic targets in the treatment of AKI and the AKI-CKD transition.

Exocyst Sec10 protects renal tubule cells from injury by EGFR/MAPK activation and effects on endocytosis

Acute kidney injury is common and has a high mortality rate, and no effective treatment exists other than supportive care. Using cell culture models, we previously demonstrated that exocyst Sec10 overexpression reduced damage to renal tubule cells and speeded recovery and that the protective effect was mediated by higher basal levels of mitogen-activated protein kinase (MAPK) signaling. The exocyst, a highly-conserved eight-protein complex, is known for regulating protein trafficking. Here we show that the exocyst biochemically interacts with the epidermal growth factor receptor (EGFR), which is upstream of MAPK, and Sec10-overexpressing cells express greater levels of phosphorylated (active) ERK, the final step in the MAPK pathway, in response to EGF stimulation. EGFR endocytosis, which has been linked to activation of the MAPK pathway, increases in Sec10-overexpressing cells, and gefitinib, a specific EGFR inhibitor, and Dynasore, a dynamin inhibitor, both reduce EGFR endocytosis. In turn, inhibition of the MAPK pathway reduces ligand-mediated EGFR endocytosis, suggesting a potential feedback of elevated ERK activity on EGFR endocytosis. Gefitinib also decreases MAPK signaling in Sec10-overexpressing cells to levels seen in control cells and, demonstrating a causal role for EGFR, reverses the protective effect of Sec10 overexpression following cell injury in vitro. Finally, using an in vivo zebrafish model of acute kidney injury, morpholino-induced knockdown of sec10 increases renal tubule cell susceptibility to injury. Taken together, these results suggest that the exocyst, acting through EGFR, endocytosis, and the MAPK pathway is a candidate therapeutic target for acute kidney injury.

Deletion of the epidermal growth factor receptor in renal proximal tubule epithelial cells delays recovery from acute kidney injury

To determine the role of epidermal growth factor receptor (EGFR) activation in renal functional and structural recovery from acute kidney injury (AKI), we generated mice with a specific EGFR deletion in the renal proximal tubule (EGFR^ptKO). Ischemia–reperfusion injury markedly activated EGFR in control littermate mice; however, this was inhibited in either the knockout or wild-type mice given erlotinib, a specific EGFR tyrosine kinase inhibitor. Blood urea nitrogen and serum creatinine increased to a comparable level in EGFR^ptKO and control mice 24 h after reperfusion, but the subsequent rate of renal function recovery was markedly slowed in the knockout mice. Twenty-four hours after reperfusion, both the knockout and the inhibitor-treated mice had a similar degree of histologic renal injury as control mice, but at day 6 there was minimal evidence of injury in the control mice while both EGFR^ptKO and erlotinib-treated mice still had persistent proximal tubule dilation, epithelial simplification, and cast formation. Additionally, renal cell proliferation was delayed due to decreased ERK and Akt signaling. Thus, our studies provide both genetic and pharmacologic evidence that proximal tubule EGFR activation plays an important role in the recovery phase after acute kidney injury.

Single-arm phase II study of multiagent concurrent chemoradiotherapy and gefitinib in locoregionally advanced squamous cell carcinoma of the head and neck

BACKGROUND

This phase II study tested the addition of the oral epidermal growth factor receptor gefitinib to multiagent concurrent chemoradiotherapy regimen in head and neck squamous cell cancer (HNSCC).

METHODS

Patients with stage III-IV HNSCC received hyperfractionated radiation (72-74.4 Gy at 120 cGy twice daily), with concurrent 96-hour infusions of cisplatin 20 mg/m(2) /day and fluorouracil 1000 mg/m(2) /day given during weeks 1 and 4. Daily gefitinib 250 mg was started on day 1 of radiation and continued for 2 years. Results were retrospectively compared with our previous study using identical chemoradiotherapy without gefitinib.

RESULTS

Sixty patients were enrolled in the study; 80% had stage IV disease and 68% had oropharyngeal primary tumors. The full course of gefitinib was not tolerated by 42%; there were 5 treatment-related deaths (8%). With a median follow-up of 54 months, 2- and 3-year overall survival estimates were 80% and 71%, respectively. Projected distant metastatic control at 2 and 3 years was 88%. When compared with our historical cohort, acute toxicities including renal dysfunction and unplanned rehospitalization were worse in the study patients. Projected outcome estimates did not differ between the 2 cohorts.

CONCLUSIONS

Addition of gefitinib to concurrent chemoradiotherapy was difficult to complete, did not improve outcomes, and increased toxicity.

Activation of epidermal growth factor receptor mediates reperfusion arrhythmias in anaesthetized rats

AIMS

Epidermal growth factor receptor (EGFR) plays a critical role in the development and function of the heart. Previous studies have demonstrated that EGFR is involved in regulating electrical excitability of the heart. The present study was designed to investigate whether EGFR activation would mediate cardiac arrhythmias induced by reperfusion in anaesthetized rats.

METHODS AND RESULTS

Reperfusion arrhythmias were induced by 10 min ligation of the left anterior descending coronary artery, followed by a 30 min reperfusion in anaesthetized rats. The incidence and severity of cardiac arrhythmias were significantly reduced by pre-treatment with the EGFR kinase inhibitor AG556. The phosphorylation level of myocardial EGFR was increased during ischaemia and at early reperfusion. Intramyocardial transfection of EGFR siRNA reduced EGFR mRNA and protein, and decreased the incidence of ventricular fibrillation induced by reperfusion. Interestingly, tyrosine phosphorylation levels of cardiac Na(+) channels (I(Na)) and L-type Ca(2+) channels (I(Ca,L)) were significantly increased at time points corresponding to the alteration of EGFR phosphorylation levels during reperfusion. AG556 pre-treatment countered the increased tyrosine phosphorylation level of Na(+) and L-type Ca(2+) channels induced by reperfusion. Patch-clamp studies proved that AG556 could inhibit I(Na) and I(Ca,L) in rat ventricular myocytes. No significant alteration was observed in tyrosine phosphorylation levels of cardiac Kv4.2 and Kir2.1 channels during reperfusion.

CONCLUSION

These results demonstrate for the first time that EGFR plays an important role in the genesis of arrhythmias induced by reperfusion, which is likely mediated at least in part by enhancing tyrosine phosphorylation of cardiac Na(+) and L-type Ca(2+) channels.

Heparin binding epidermal growth factor in renal ischaemia/reperfusion injury

The epidermal growth factor (EGF) receptor and its ligands are crucially involved in the renal response to ischaemia. We studied the heparin binding-epidermal growth factor (HB-EGF), a major ligand for the EGF receptor, in experimental and human ischaemia/reperfusion injury (IRI). HB-EGF mRNA and protein expression was studied in rat kidneys and cultured human tubular (HK-2) cells that were subjected to IRI and in human donor kidneys during transplantation. The effect of EGF receptor inhibition was investigated in vivo and in vitro. Furthermore, urinary HB-EGF protein excretion was studied after renal transplantation. Finally, HB-EGF KO and WT mice were subjected to IRI to study the role of HB-EGF in renal injury. HB-EGF mRNA was significantly up-regulated in the early phase of IRI in rats, cells, and human donor biopsies. Treatment with PKI-166 reduces macrophage accumulation and interstitial alpha-SMA in the early phase of IRI in rats. In vitro, PKI-166 causes a marked reduction in HB-EGF-induced cellular proliferation. Urinary HB-EGF is increased after transplantation compared with control urines from healthy subjects. HB-EGF KO mice subjected to IRI revealed significantly less morphological damage after IRI, compared with WT mice. We conclude that IRI results in early induction of HB-EGF mRNA and protein in vivo and in vitro. Absence of HB-EGF and inhibition of the EGF receptor in the early phase of IRI has protective effects, suggesting a modulating role for HB-EGF.

5-hydroxytryptamine receptor stimulation of mitochondrial biogenesis

Mitochondrial dysfunction is both a cause and target of reactive oxygen species during ischemia-reperfusion, drug, and toxicant injury. After injury, renal proximal tubular cells (RPTC) recover mitochondrial function by increasing the expression of the master regulator of mitochondrial biogenesis, peroxisome-proliferator-activated-receptor-gamma-coactivator-1alpha (PGC-1alpha). The goal of this study was to determine whether 5-hydroxytryptamine (5-HT) receptor agonists increase mitochondrial biogenesis and accelerate the recovery of mitochondrial function. Reverse transcription-polymerase chain reaction analysis confirmed the presence of 5-HT2A, 5-HT2B, and 5-HT2C receptor mRNA in RPTC. The 5-HT2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI; 3-10 microM) increased PGC-1alpha levels, expression of mitochondrial proteins ATP synthase beta and NADH dehydrogenase (ubiquinone) 1beta subcomplex 8 (NDUFB8), MitoTracker Red staining intensity, cellular respiration, and ATP levels through a 5-HT receptor and PGC-1alpha-dependent pathway. Similar effects were observed with the 5-HT2 agonist m-chlorophenylpiperazine and were blocked by the 5-HT2 antagonist 8-[3-(4-fluorophenoxy) propyl]-1-phenyl-1,3,8-triazaspiro[4,5]decan-4-one (AMI-193). In addition, DOI accelerated the recovery of mitochondrial function after oxidant-induced injury in RPTC. This is the first report to demonstrate 5-HT receptor-mediated mitochondrial biogenesis, and we suggest that 5-HT-agonists may be effective in the treatment of mitochondrial and cell injury.

Soluble HB-EGF induces epithelial-to-mesenchymal transition in inner medullary collecting duct cells by upregulating Snail-2

Animal models of acute renal injury suggest that the epidermal growth factor receptor (EGFR) axis may have a beneficial role in the recovery from acute renal injury, but recent reports describe detrimental effects of EGFR activation in chronic renal injury. Expression of the EGFR ligand heparin-binding EGF-like growth factor (HB-EGF) increases following renal injury, but the effects of this sustained upregulation have not been well studied. Here, stable overexpression of soluble HB-EGF (sHB-EGF) in mouse inner medullary collecting duct (IMCD) cells led to marked phenotypic changes: sHB-EGF-expressing cells demonstrated a fibroblast-like morphology, did not form epithelial sheets, exhibited cytoplasmic projections, decreased expression of epithelial markers, and increased expression of fibroblast-specific protein-1. They also demonstrated anchorage-independent growth and formed tumors when injected subcutaneously into nude mice. Quantitative RT-PCR and a luciferase reporter assay suggested that sHB-EGF repressed transcription of E-cadherin, and a concomitant TGF-beta-independent upregulation of the E-cadherin repressor Snail-2 was observed. Stable downregulation of Snail-2 in sHB-EGF-overexpressing cells restored epithelial characteristics (E-cadherin and cytokeratin expression) but did not alter their anchorage-independent growth. In summary, sustained exposure to sHB-EGF induces epithelial-to-mesenchymal transition of IMCD cells, in part by upregulating the E-cadherin transcriptional repressor Snail-2.

Src regulates cell cycle protein expression and renal epithelial cell proliferation via PI3K/Akt signaling-dependent and -independent mechanisms

Our recent studies showed that Src family kinases (SFKs) are important mediators of proliferation in renal proximal tubular cells (RPTC). In this study, we elucidate the signaling mechanisms that mediate SFK regulation of cell proliferation and cycle protein expression, and identify the SFK member responsible for these responses in a mouse RPTC line. Akt, a target of phosphoinositide-3-kinase (PI3K), and ERK1/2 were constitutively phosphorylated in RPTC cultured in the presence of serum. While treatment of cells with PP1, a specific SFK inhibitor, completely blocked phosphorylation of ERK1/2 and Akt, only inhibition of PI3K/Akt resulted in decreased RPTC proliferation. Incubation of cells with PP1 decreased cyclin D1 expression, decreased p27 and p57 phosphorylation, and increased p27 and p57 expression, two cyclin-dependent kinase inhibitors. Inhibition of the PI3K pathway decreased expression of cyclin D1 without altering expression of p27 and p57. In contrast, PP1 and PI3K inhibition had no effect on cyclin E and p21. Although RPTC expressed Src, Fyn, and Lyn, only siRNA-mediated knockdown of Src decreased RPTC proliferation, decreased cyclin D1 expression, and increased p27 and p57 expression. These data reveal that Src is a crucial mediator of RPTC proliferation and Src-mediated proliferation is associated with PI3K-dependent upregulation of cyclin D1 and PI3K-independent downregulation of p27 and p57.

p66shc inhibits pro-survival epidermal growth factor receptor/ERK signaling during severe oxidative stress in mouse renal proximal tubule cells

The fully executed epidermal growth factor receptor (EGFR)/Ras/MEK/ERK pathway serves a pro-survival role in renal epithelia under moderate oxidative stress. We and others have demonstrated that during severe oxidative stress, however, the activated EGFR is disconnected from ERK activation in cultured renal proximal tubule cells and also in renal proximal tubules after ischemia/reperfusion injury, resulting in necrotic death. Studies have shown that the tyrosine-phosphorylated p46/52 isoforms of the ShcA family of adaptor proteins connect the activated EGFR to activation of Ras and ERK, whereas the p66(shc) isoform can inhibit this p46/52(shc) function. Here, we determined that severe oxidative stress (after a brief period of activation) terminates activation of the Ras/MEK/ERK pathway, which coincides with ERK/JNK-dependent Ser(36) phosphorylation of p66(shc). Isoform-specific knockdown of p66(shc) or mutation of Ser(36) to Ala, but not to Asp, attenuated severe oxidative stress-mediated ERK inhibition and cell death in vitro. Also, severe oxidative stress (unlike ligand stimulation and moderate oxidative stress, both of which support survival) increased binding of p66(shc) to the activated EGFR and Grb2. This binding dissociated the SOS1 adaptor protein from the EGFR-recruited signaling complex, leading to termination of Ras/MEK/ERK activation. Notably, Ser(36) phosphorylation of p66(shc) and its increased binding to the EGFR also occurred in the kidney after ischemia/reperfusion injury in vivo. At the same time, SOS1 binding to the EGFR declined, similar to the in vitro findings. Thus, the mechanism we propose in vitro offers a means to ameliorate oxidative stress-induced cell injury by either inhibiting Ser(36) phosphorylation of p66(shc) or knocking down p66(shc) expression in vivo.

Heparin-binding epidermal growth factor and Src family kinases in proliferation of renal epithelial cells

Our recent studies have shown that proliferation of renal proximal tubular cells (RPTC) in the absence of growth factors requires activation of the epidermal growth factor (EGF) receptor. We sought to identify the endogenous EGF receptor ligand and investigate the mechanism(s) by which RPTC proliferate in different models. RPTC expressed both pro- and cleaved forms of heparin-binding epidermal growth factor (HB-EGF) and several metalloproteinases (MMP-2, -3, -9, and ADAM10, ADAM17) that have been reported to cleave HB-EGF. Treatment of RPTC with CRM 197, an inhibitor of HB-EGF binding to the EGF receptor, or downregulation of HB-EGF with small interfering RNA inhibited RPTC proliferation following plating. Furthermore, GM6001 (pan-MMP inhibitor), tumor-necrosis factor protease inhibitor-1 (TAPI-1; MMP and ADAM17 inhibitor), and GW280264X (ADAM10 and -17 inhibitor), but not GI254023X (ADAM10 inhibitor), attenuated the proliferation after plating. Although EGF receptor activation is required for RPTC proliferation after oxidant injury, CRM197, GM6001, and TAPI-1 did not block this response. In contrast, inhibition of Src with PP1 blocked EGF receptor activation and RPTC proliferation after oxidant injury. In addition, PP1 treatment attenuated HB-EGF-enhanced RPTC proliferation. We suggest that RPTC proliferation after plating is mediated by HB-EGF produced through an autocrine/paracrine mechanism and RPTC proliferation following oxidant injury is mediated by Src without involvement of HB-EGF.

Extracellular signal-regulated kinase activation during renal ischemia/reperfusion mediates focal adhesion dissolution and renal injury

Acute renal failure due to ischemia/reperfusion involves disruption of integrin-mediated cellular adhesion and activation of the extracellular signal-regulated kinase (ERK) pathway. The dynamics of focal adhesion organization and phosphorylation during ischemia/reperfusion in relation to ERK activation are unknown. In control kidneys, protein tyrosine-rich focal adhesions, containing focal adhesion kinase, paxillin, and talin, were present at the basolateral membrane of tubular cells and colocalized with short F-actin stress fibers. Unilateral renal ischemia/reperfusion caused a reversible protein dephosphorylation and loss of focal adhesions. The focal adhesion protein phosphorylation rebounded in a biphasic manner, in association with increased focal adhesion kinase, Src, and paxillin tyrosine phosphorylation. Preceding phosphorylation of these focal adhesion proteins, reperfusion caused increased phosphorylation of ERK. The specific mitogen-activated protein kinase kinase 1/2 inhibitor U0126 prevented ERK activation and attenuated focal adhesion kinase, paxillin, and Src phosphorylation, focal adhesion restructuring, and ischemia/reperfusion-induced renal injury. We propose a model whereby ERK activation enhanced protein tyrosine phosphorylation during ischemia/reperfusion, thereby driving the dynamic dissolution and restructuring of focal adhesions and F-actin cytoskeleton during reperfusion and renal injury.

Signaling of Mitochondrial Biogenesis following Oxidant Injury

Mitochondrial dysfunction is a common consequence of ischemia-reperfusion and drug injuries. For example, sublethal injury of renal proximal tubular cells (RPTCs) with the model oxidant tert-butylhydroperoxide (TBHP) causes mitochondrial injury that recovers over the course of six days. Although regeneration of mitochondrial function is integral to cell repair and function, the signaling pathway of mitochondrial biogenesis following oxidant injury has not been examined. A 10-fold overexpression of the mitochondrial biogenesis regulator PPAR-gamma cofactor-1alpha (PGC-1alpha) in control RPTCs resulted in a 52% increase in mitochondrial number, a 27% increase in respiratory capacity, and a 30% increase in mitochondrial protein markers, demonstrating that PGC-1alpha mediates mitochondrial biogenesis in RPTCs. RPTCs sublethally injured with TBHP exhibited a 50% decrease in mitochondrial function and increased mitochondrial autophagy. Compared with the controls, PGC-1alpha levels increased 12-fold on days 1, 2, and 3 post-injury and returned to base line on day 4 as mitochondrial function returned. Inhibition p38 MAPK blocked the up-regulation of PGC-1alpha following oxidant injury, whereas inhibition of calcium-calmodulin-dependent protein kinase, calcineurin A, nitric-oxide synthase, and phosphoinositol 3-kinase had no effect. The epidermal growth factor receptor (EGFR) was activated following TBHP exposure, and the EGFR inhibitor AG1478 blocked the up-regulation of PGC-1alpha. Additional inhibitor studies revealed that the sequential activation of Src, p38 MAPK, EGFR, and p38 MAPK regulate the expression of PGC-1alpha following oxidant injury. In contrast, although Akt was activated following oxidant injury, it did not play a role in PGC-1alpha expression. We suggest that mitochondrial biogenesis following oxidant injury is mediated by p38 and EGFR activation of PGC-1alpha.

STAT3 attenuates EGFR-mediated ERK activation and cell survival during oxidant stress in mouse proximal tubular cells

We have shown that renal epithelial cell survival depends on the sustained activation of the extracellular signal-regulated protein kinase (ERK) and lack of this activation was associated with death during oxidative stress. ERK is activated via the canonical epidermal growth factor receptor (EGFR)-Ras-MEK pathway, which could be attenuated by oxidants. We now show that the failure to activate ERK in a sustained manner during severe oxidative stress is owing to the activation of the signal transducer and activator of transcription-3 (STAT3) rather than the failure to activate the EGFR. Tyrosine phosphorylation of the EGFR and STAT3 was studied in hydrogen peroxide (H(2)O(2))-treated mouse proximal tubule (TKPTS) cells or in mouse kidney after ischemia/reperfusion (I/R) injury by Western blotting. STAT3 activation was inhibited by either pharmacologically (AG490) through its upstream janus kinase (JAK2) or by a dominant-negative STAT3 adenovirus. EGFR was inhibited by AG1478. Survival was determined by fluorescence-activated cell sorter analysis and trypan blue exclusion. We found that the EGFR was phosphorylated on its major autophosphorylation site (Tyr1173) regardless of the H(2)O(2) dose. On the other hand, both I/R and severe oxidative stress - but not moderate stress - increased tyrosine phosphorylation of STAT3 in an EGFR and JAK2-dependent manner. Inhibition of JAK2 or STAT3 lead to increased ERK activation and survival of TKPTS cells during severe oxidative stress. Our data suggest a role of tyrosine-phosphorylated STAT3 in the suppression of ERK activation. These data suggest that the STAT3 pathway might represent a new target for improved survival of proximal tubule cells exposed to severe oxidant injury.

An IGF-I antagonist does not inhibit renal fibrosis in the rat following subtotal nephrectomy

Insulin-like growth factor I (IGF-I) has been proposed as a mediator of kidney scarring, although no interventional studies on the role of IGF-I in models of chronic kidney disease have been reported. The effect of a peptide IGF-I receptor antagonist (JB3) has been examined on kidney fibrosis and function in the rat following 5/6 subtotal nephrectomy (SNx). Male Wistar rats were anesthetized with halothane and subjected to SNx. JB3 was delivered by subcutaneous infusion using Alzet osmotic minipumps. In vitro studies showed JB3 to displace125I-IGF-I binding to isolated rat glomeruli and to inhibit IGF-I-induced receptor phosphorylation in renal tubular cells in culture. In the 7-day SNx rats, IGF-I immunostain was present in collecting tubules and JB3 inhibited compensatory renal growth, the maximum effect occuring at 10 μg·kg−1·day−1. After 90 days, the SNx rats developed proteinuria, hypertension, and a fall in glomerular filtration rate. IGF-I immunostain was present in the tubulointerstitial space of the remnant kidney together with marked tubulointerstitial fibrosis. Treatment with JB3 at a dose of 10 μg·kg−1·day−1had no effect on the renal fibrosis measured by Masson's trichrome staining or immunostain for collagen III and collagen IV. The proteinuria, hypertension, and lower creatinine clearance all remained unchanged. The remnant kidney was associated with a 50% decrease in renal IGF-I mRNA, which was partially restored by treatment with JB3. Thus an interventional study with an IGF-I receptor antagonist does not support a role for IGF-I in the development of renal fibrosis in the SNx rat, although IGF-I does make an important contribution to compensatory kidney growth.

Small tumor size and limited smoking history predicts activated epidermal growth factor receptor in early-stage non-small cell lung cancer

STUDY OBJECTIVE

Epidermal growth factor receptor (EGFR) signaling has been implicated in the pathogenesis of bronchial dysplasia and overt non-small cell lung cancer (NSCLC). We hypothesized that assaying for EGFR activity using an antibody that recognizes phosphorylated EGFR (pEGFR) may identify a subset of patients whose tumor cells are dependent on EGFR signaling. We also hypothesized that EGFR activity may be prognostic for early-stage NSCLC.

DESIGN

We constructed high-density tissue microarrays using tissues from 193 surgically resected stage I NSCLCs. These arrays were immunostained with a pEGFR antibody, and the intensity of staining was correlated with clinicopathologic variables, as well as disease-free and overall survival (OS). Staining was scored by intensity and the percentage of positively stained tumor cells in triplicate.

MEASUREMENTS AND RESULTS

We found the expression of pEGFR (with > 50% of tumor cells staining positive) in 51% of tumor tissues. We found an inverse correlation between pEGFR, and both tumor size and the degree of tobacco smoking. In addition, we found a trend in which pEGFR expression was inversely correlated with disease stage (IA higher than IB). There was no correlation with sex, histology, or disease-free or OS.

CONCLUSIONS

Our results suggest that pEGFR levels are present in early-stage NSCLC, especially in patients with small tumors and in those with short smoking histories, but there is no prognostic impact on a patient's disease course. Targeting EGFR may therefore have more promise in chemoprevention or in patients with smaller early-stage NSCLCs compared with those with more advanced disease.

Heparin-binding EGF-like growth factor (HB-EGF) and necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal disease that occurs predominantly in premature infants. Despite various advances in management, the mortality of this disease remains high. During the last decade, studies from our laboratory have shown that heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the epidermal growth factor (EGF) family, can protect intestinal epithelial cells (IEC) from various forms of injury in vitro. Furthermore, we have used both an intestinal I/R injury model in adult rats, and a neonatal rat pup model of NEC, to show that HB-EGF can protect the intestines from injury. On administration of HB-EGF in the neonatal rat model, the incidence of NEC is reduced from 65% to 27.3% (P < 0.05), and the histological injury score is decreased from 2 to 1.1 (P < 0.05). In addition, the survival rate is increased from 25% to 63.6% and the survival time extended from 59 hours to 73 hours (P < 0.05). In addition, using human specimens from newborns undergoing bowel resection for NEC, we found that the expression of endogenous HB-EGF mRNA in normal areas of the intestine at the resection margins was higher than that of the intestine afflicted with acute NEC. Endogenous HB-EGF may be involved in epithelial cell repair, proliferation, and regeneration during recovery from injury. Exogenous administration of HB-EGF potentiates recovery from intestinal injury in vitro and in vivo. Taken together, these results support a potential therapeutic role for HB-EGF in the treatment of NEC in the future.

p38 kinase-mediated transactivation of the epidermal growth factor receptor is required for dedifferentiation of renal epithelial cells after oxidant injury

Renal proximal tubular cell (RPTC) dedifferentiation is thought to be a prerequisite for regenerative proliferation and migration after renal injury. However, the specific mediators and the mechanisms that regulate RPTC dedifferentiation have not been elucidated. Because epidermal growth factor (EGF) receptor activity is required for recovery from acute renal failure, we examined the role of the EGF receptor in dedifferentiation and the mechanisms of EGF receptor transactivation in primary cultures of RPTCs after oxidant injury. Exposure of confluent RPTCs to H2O2 resulted in 40% cell death, and surviving RPTCs acquired a dedifferentiated phenotype (e.g. elongated morphology and vimetin expression). The EGF receptor, p38, Src, and MKK3 were activated after oxidant injury and inhibition of the EGF receptor or p38 with specific inhibitors (AG1478 and SB203580, respectively) blocked RPTC dedifferentiation. Treatment with SB203580 or adenoviral overexpression of dominant negative p38alpha or its upstream activator, MKK3, inhibited EGF receptor phosphorylation induced by oxidant injury, whereas AG1478 had no effect on p38 phosphorylation. Inhibition of Src with 4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]-pyrimidine (PP1) blocked MKK3 and p38 activation, and inhibition of MKK3 blocked p38 activation. In addition, inactivation of Src, MKK3, p38, or the EGF receptor blocked tyrosine phosphorylation of beta-catenin, a key signaling intermediate that is involved in the epithelial-mesenchymal transition and vimentin expression. These results reveal that p38 mediates EGF receptor activation after oxidant injury; that Src activates MMK3, which, in turn, activates p38; and that the EGF receptor signaling pathway plays a critical role in RPTC dedifferentiation.

Requirement of the epidermal growth factor receptor in renal epithelial cell proliferation and migration

We showed that renal proximal tubular cells (RPTC) can proliferate and migrate following plating and oxidant or mechanical injury in the absence of exogenous growth factors; however, the mechanisms of this response remain unclear. We examined whether epidermal growth factor receptor (EGFR) signaling is activated following plating and mechanical injury and mediates RPTC proliferation and migration. EGFR, Akt [a target of phosphoinositide-3-kinase (PI3K)], and ERK1/2 were activated after plating and mechanical injury, and their phosphorylation was further enhanced by addition of exogenous EGF. Inactivation of the EGFR with the selective inhibitor AG-1478 completely blocked phosphorylation of EGFR, Akt, and ERK1/2 and blocked cell proliferation and migration after plating and injury. Inhibition of PI3K with LY-294002 blocked Akt phosphorylation and proliferation, whereas U-0126 blocked ERK1/2 phosphorylation but had no effect on proliferation. Furthermore, p38 was phosphorylated following mechanical injury and the p38 inhibitor SB-203580 blocked p38 phosphorylation and cell migration. In contrast, neither PI3K nor ERK1/2 inhibition blocked cell migration. These results show that EGFR activation is required for RPTC proliferation and migration and that proliferation is mediated by PI3K, whereas migration is mediated by p38.

Heparin-binding epidermal growth factor-like growth factor and intestinal ischemia-reperfusion injury

Intestinal ischemia/reperfusion (I/R) injury affects patients of different ages, especially premature babies and the elderly. The outcome after intestinal I/R is often dismal, which may be attributed to loss of the barrier and immune functions of the intestines, as well as development of secondary injury in remote organs. The available treatment for advanced gut ischemia mandates extensive resection, which may cause growth retardation in infants and nutritional problems in the elderly. Throughout the past decade we have been investigating the potential therapeutic role of heparin-binding epidermal growth factor-like factor (HB-EGF) in intestinal I/R. The mitogenic and chemoattractant functions of HB-EGF formed the initial rationale for our investigations. In addition, HB-EGF is a potent antiapoptotic protein that enables cells and tissues exposed to different apoptotic stimuli to survive hypoxic, oxidative, and nutritional stresses. HB-EGF is known to have a vital role in wound healing and postischemic regeneration in different organs. In the current review, we summarize the results of our findings of the beneficial effects of HB-EGF in intestinal I/R, supported by additional evidence from the literature and an explanation of different possible mechanisms of its actions. Collectively, the data strongly suggest a potential therapeutic role for the use of HB-EGF to treat intestinal ischemic diseases such as I/R and necrotizing enterocolitis.

Importance of Functional EGF Receptors in Recovery from Acute Nephrotoxic Injury

ABSTRACT. Previous studies have demonstrated increased renal expression of EGF receptor (EGFR) and EGFR ligands in response to acute toxic or ischemic renal tubular injury and have indicated that exogenous administration of EGF accelerates recovery from such injury. However, no studies to date have proved definitively an essential role for EGFR-mediated responses in regeneration after tubule injury. To this end, waved-2 (wa-2) mice, which contain a point mutation in EGFR that reduces receptor tyrosine kinase activity by >90%, were studied. These mice have a mild phenotype (wavy coat, curly whiskers, and runted stature) and normally developed kidneys. Acute nephrotoxic injury was induced in wa-2 and wild-type mice with HgCl2. One day after HgCl2 injection, functional renal compromise was comparable in wild-type and wa-2 mice. However, the rates of recovery of serum blood urea nitrogen and creatinine levels were markedly slower in wa-2 mice. Histologic evidence of tubular injury also was more severe and persisted longer in wa-2 mice. Furthermore, their kidneys demonstrated reduced levels of DNA synthesis and increased TdT-mediated dUTP nick-end labeling staining. These studies indicate that functional EGFR activity is an essential component of the kidney’s ability to recover from acute injury and that EGFR may regulate genes involved in growth, repair, and cell survival in the kidney.

Cyclosporine or FK506 decrease mature epidermal growth factor protein expression and renal tubular regeneration in rat kidneys with ischemia/reperfusion injury

BACKGROUND

Epidermal growth factor (EGF) plays an important role in tubular regeneration in kidneys with ischemia/reperfusion (I/R) injury. This study was undertaken to evaluate the influence of cyclosporine A (CsA) or FK506 on mature EGF expression and tubular regeneration in rat kidneys with I/R injury.

METHODS

Two separate studies were performed. First, the expression of EGF and tubular regeneration was observed in rat kidneys with I/R injury on days 1, 2, 3, 5, and 7. Second, the dose-dependent response of EGF expression and tubular regeneration to CsA (5, 10, and 20 mg/kg) or FK506 (0.25, 0.5, and 1.0 mg/kg) was observed in rat kidneys with I/R injury. I/R injury was induced by clamping both renal arteries for 45 min, and CsA or FK506 was injected just after release of vascular clamps. Rats were sacrificed on day 1 for evaluation of EGF expression, and on day 2 for evaluation of BudU-positive cells. Renal function, tubular injury score, EGF expression assessed by immunoblotting, levels of CsA and FK506 in whole blood, and immunostaining for BrdU was studied.

RESULTS

EGF expression was maximal on day 1 (cortex, 29-fold; medulla, 31-fold compared with sham-operated controls), and renal tubular regeneration measured with the number of BrdU-positive cells was maximal on days 2 and 3 in kidney with I/R injury, and thereafter the level of EGF and the number of BrdU-positive cells decreased progressively. CsA or FK506 treatment to ischemic rat kidneys reduced the expression of EGF and the number of BrdU-positive cells in a dose-dependent manner.

CONCLUSIONS

CsA or FK506 treatment delays recovery from acute tubular necrosis, and this may be associated with decreased EGF expression by CsA or FK506.

Hemorrhage and renal ischemia-reperfusion upregulates the epidermal growth factor receptor in rabbit duodenum

To study the role of EGF-R in small intestinal adaptation to hemorrhage and I/R, anesthetized rabbits were implanted aseptically with arterial and venous catheters and bilateral renal artery Doppler flow probes and silastic occluders and allowed to recover. Rabbits were then randomly assigned to one of six groups: time control; hemorrhage (22.5 mL/kg) and 2.5 hours of renal occlusion (hemorrhage plus I/R); hemorrhage plus I/R and 2:1 LRS resuscitation; hemorrhage plus I/R and 3:1 LRS resuscitation; hemorrhage alone; or I/R alone. Rabbits were killed 48 hours after hemorrhage, and a section of duodenum was collected for analysis. Hemorrhage plus I/R induced a 2.5-fold increase in EGF-R tyrosine kinase activity compared with that found in the control group (P < .05), and this effect was not modified by either LRS resuscitation regimen. This increased activity was associated with similar Increases in EGF-R protein concentrations and approximately a 50% increase in EGF-R messenger (m)RNA levels compared with levels found in the control group. Further analysis of possible regulatory mechanisms for the increased EGF-R expression after hemorrhage plus I/R detected higher levels of EGF-R phosphorylation compared with those found in the control group but no significant increases in transforming growth factor-alpha mRNA levels. These data, coupled with a significant increase in duodenal thlobarbituric acid-reactive substance concentrations from rabbits in the hemorrhage plus I/R group, support the hypothesis that tyrosine kinase signal transduction pathways involving the EGF-R are activated in the small intestine after hemorrhage, renal I/R, or both, and this process may be mediated, at least in part, by oxidant stress.