Epidermal Growth Factor Receptor Blocking Antibody Research Articles

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

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

The role of RNase 7 in innate cutaneous defense against Pseudomonas aeruginosa.

The ribonuclease RNase 7 is a major skin-derived human antimicrobial protein expressed in keratinocytes. Here we show that the gram-negative pathogen Pseudomonas aeruginosa secretes factor(s) that induced RNase 7 gene and protein expression in human primary keratinocytes. The metalloprotease inhibitor marimastat, the epidermal growth factor receptor (EGFR) inhibitor AG1478 and the EGFR blocking antibody cetuximab significantly attenuated this induction, indicating an important role of the EGFR for the P.aeruginosa-mediated RNase 7 induction. In line with this, siRNA-mediated downregulation of ADAM17, a metalloprotease known to proteolytically mediate the release of soluble EGFR ligands, decreased the P.aeruginosa-mediated RNase 7 induction in keratinocytes. The impact of the EGFR was also demonstrated in a human 3D skin equivalent where blockade of the EGFR diminished induction of RNase 7 by P.aeruginosa. Blockade of Toll-like receptor 5 (TLR5), a pattern recognition receptor (PRR) known to be activated by P.aeruginosa, only moderately reduced the P.aeruginosa-mediated RNase 7 induction in keratinocytes. The functional relevance of RNase 7 to participate in cutaneous defense against P.aeruginosa was demonstrated by antibodies that neutralized the antimicrobial activity of RNase 7. These antibodies significantly inhibited the capacity of human stratum corneum skin extracts to control growth of P.aeruginosa. Taken together, our results indicate that P.aeruginosa induces the expression of RNase 7 in keratinocytes in an EGFR-dependent manner. Enhanced release of RNase 7 contributes to control cutaneous growth of P.aeruginosa.

Hypoxic‐Induction of Arginase II is Associated with EGFR Activation and EGF Production

We have previously shown that hypoxia induces arginase II through epidermal growth factor receptor (EGFR) activation in human pulmonary microvascular endothelial cells (hPMVEC). We hypothesized that hypoxia‐induced EGFR activation occurs via epidermal growth factor (EGF) release. Before studying hPVMEC, HeLa cells were used to dissect cellular mechanisms. Cells were grown in normoxia (21% oxygen) or hypoxia (1% oxygen) for 48 hours and mRNA harvested. RT‐PCR analysis showed substantially higher levels of EGF, EGFR, and arginase II mRNA in the cells incubated in hypoxia than in those incubated in normoxia. Cells were incubated in normoxia or hypoxia for 24 hours, the media harvested and placed on naive cells which were than incubated in normoxia for 48 hours. Cells incubated with hypoxia‐conditioned media had greater arginase II protein levels compared to cells incubated with normoxia‐conditioned media. Cells were then incubated in hypoxia or normoxia for 48 hours with either vehicle or the EGFR kinase inhibitor AG1478 added to the media, and AG1478 treatment prevented hypoxia‐induced arginase II protein expression. Finally, cells were incubated in hypoxia and normoxia for 48 hours with either IgG or an EGFR blocking antibody added to the media, the hypoxia‐induced arginase II expression was substantially lower in the cells incubated with the EGFR blocking antibody than in those incubated with IgG. These findings suggest that hypoxia‐induced arginase II expression may be dependent on EGF‐mediated activation of EGFR. We speculate that the EGFR pathway may be a novel therapeutic target for pulmonary hypertensive disorders associated with hypoxia.

Should the results of the new EPOC trial change practice in the management of patients with resectable metastatic colorectal cancer confined to the liver?

Biologic agents, specifically epidermal growth factor receptor blockers and vascular endothelial growth factor inhibitors, combined with cytotoxic agents have become a standard of care for the treatment of metastatic colorectal cancer (CRC) but lack proven benefit as adjuvant treatment of primary colon cancer. Patients with resectable CRC metastases limited to the liver represent an intermediate group in terms of their burden of disease and prognosis. In those patients, the 5-year life expectancy after surgery is approximately 35% to 40% compared with 75% in patients with stage III disease and 10% in unselected patients with stage IV disease. In patients with resectable liver-limited CRC randomly assigned to treatment with surgery alone or perioperative chemotherapy with infusional fluorouracil, leucovorin, and oxaliplatin (FOLFOX), the risk of cancer relapse after surgery in the cohort randomly assigned to perioperative FOLFOX was reduced by one quarter. A logical next step is to raise the question, Can outcomes be improved further by combining treatment with biologic and cytotoxic agents in the perioperative setting in this increasingly common patient population? The New EPOC (Eloxatin Peri-Operative Chemotherapy) trial was organized in the United Kingdom to address this question, and the results were published and recently updated. The trial compared two groups of patients who were determined to have resectable liver metastases, all of whom received perioperative chemotherapy with FOLFOX, oxaliplatin and capecitabine (XELOX), or fluorouracil, leucovorin, and irinotecan (FOLFIRI) with a random assignment to treatment with or without the addition of the epidermal growth factor receptor–blocking antibody cetuximab. The trial initially enrolled patients regardless of KRAS mutation status in the tumor but was later restricted to patients whose tumors were found to be KRAS (exon 2) wild type. On the basis of their study’s outcome, the investigators concluded that combinations of cetuximab with chemotherapy in the perioperative setting for treatment of patients with potentially resectable colorectal liver metastases conferred no survival benefit and were actually detrimental. Data from studies in patients with advanced disease show that the addition of cetuximab or panitumumab to combination chemotherapy in patients whose tumors harbor a KRAS (exon 2) or other RAS mutations can be detrimental, although overall, patients without RAS mutations benefit from the combination. If this biology applies in the setting of resected stage IV disease, the initial inclusion of patients who did not have RAS testing may have influenced the outcome. In the N0147 (Comparison of Combination Chemotherapy Regimens With or Without Cetuximab in Treating Patients Who Have Undergone Surgery for Stage III Colon Cancer) study, which assigned patients with resected stage III CRC to FOLFOX with or without cetuximab, there was a statistically nonsignificant trend toward a detrimental effect that was independent of RAS status in the cetuximab-treated cohort. The New EPOC investigators hypothesize that molecular interactions may be playing a role in the observed outcomes in both N0147 and New EPOC, suggesting that the interplay of chemotherapy with cetuximab is different in patients with microscopic residual disease than it is in those with gross residual disease. Organizing randomized clinical trials that involve surgery and chemotherapy is difficult, and few such combined modality studies have been completed. We congratulate the investigators for meeting their accrual goal, but we are concerned that the data they published may not support the conclusions that they drew from their study because of issues surrounding surgical quality control, inclusion of patients whose surgical outcomes did not meet the predetermined study goals, incomplete data, and diversity in both the population enrolled and the regimens they received. Surgery is both an art and a science, and its practice depends on the judgment and skills of the surgeons. Studies have shown that the experience of the surgeon and the surgical team can be an important variable in patient outcomes. The impact of quality assurance of the operative procedures performed in cancer surgery trials has been explicitly demonstrated in two large, randomized Dutch trials that addressed gastric and rectal cancer surgery, both of which were practice changing. In those trials, surgeons could only recruit to the JOURNAL OF CLINICAL ONCOLOGY COMMENTS AND CONTROVERSIES VOLUME 33 NUMBER 3 JANUARY 2

Infection of keratinocytes with Trichophytum rubrum induces epidermal growth factor-dependent RNase 7 and human beta-defensin-3 expression.

Human keratinocytes are able to express various antimicrobial peptides (AMP) to protect the skin from exaggerated microbial colonization and infection. Recently, in vitro growth-inhibiting activity of the skin-derived AMP psoriasin, RNase 7 and human beta-defensin (hBD)-2 against dermatophytes such as Trichophyton (T.) rubrum have been reported. To evaluate whether keratinocytes are able to respond to T. rubrum infection by an induced expression of AMP we exposed primary keratinocytes to living conidia of T. rubrum. This led to conidia germination and mycelial growth which was paralleled by a strong gene induction of the skin-derived AMP RNase 7 and hBD-3. Gene expression of the AMP psoriasin (S100A7) and hBD-2 were only slightly induced. The T. rubrum-mediated RNase 7 gene induction was accompanied by increased secretion of RNase 7. Parallel treatment of the keratinocytes with T. rubrum and the cytokine combination IL-17A/IFN-γ resulted in synergistic induction of RNase 7 and hBD-3 expression. Since patients receiving therapy by inhibition of the epidermal growth factor receptor (EGFR) more often suffer from dermatophytoses we investigated whether EGFR may be involved in the T. rubrum-mediated RNase 7 and hBD-3 induction. Primary keratinocytes incubated with an EGFR blocking antibody as well as with the EGFR antagonist AG1478 showed a significantly diminished RNase 7 and hBD-3 induction upon exposure of the keratinocytes to T. rubrum indicating that EGFR is involved in the T. rubrum-mediated induction of RNase 7 and hBD-3. The growth of T. rubrum in vitro was inhibited by hBD-3 in a dose-dependent manner suggesting that hBD-3 may contribute to cutaneous innate defense against T. rubrum. Taken together our data indicate that keratinocytes are able to initiate a fast defense response towards T. rubrum by the increased expression of AMP active against T. rubrum. A dysregulation of AMP may contribute to chronic and recurring dermatophytoses.

Laminin-5γ-2 (LAMC2) Is Highly Expressed in Anaplastic Thyroid Carcinoma and Is Associated With Tumor Progression, Migration, and Invasion by Modulating Signaling of EGFR

Anaplastic thyroid carcinoma (ATC) is an aggressive malignancy having no effective treatment. Laminin subunit-γ-2 (LAMC2) is an epithelial basement membrane protein involved in cell migration and tumor invasion and might represent an ideal target for the development of novel therapeutic approaches for ATC. The objective of the investigation was to study the role of LAMC2 in ATC tumorigenesis. LAMC2 expression was evaluated by RT-PCR, Western blotting, and immunohistochemistry in tumor specimens, adjacent noncancerous tissues, and cell lines. The short hairpin RNA (shRNA) approach was used to investigate the effect of LAMC2 knockdown on the tumorigenesis of ATC. LAMC2 was highly expressed in ATC samples and cell lines compared with normal thyroid tissues. Silencing LAMC2 by shRNA in ATC cells moderately inhibited cell growth in liquid culture and dramatically decreased growth in soft agar and in xenografts growing in immunodeficient mice. Silencing LAMC2 caused cell cycle arrest and significantly suppressed the migration, invasion, and wound healing of ATC cells. Rescue experiments by overexpressing LAMC2 in LAMC2 knockdown cells reversed the inhibitory effects as shown by increased cell proliferation and colony formation. Microarray data demonstrated that LAMC2 shRNA significantly altered the expression of genes associated with migration, invasion, proliferation, and survival. Immunoprecipitation studies showed that LAMC2 bound to epidermal growth factor receptor (EGFR) in the ATC cells. Silencing LAMC2 partially blocked epidermal growth factor-mediated activation of EGFR and its downstream pathway. Interestingly, cetuximab (an EGFR blocking antibody) or EGFR small interfering RNA additively enhanced the antiproliferative activity of the LAMC2 knockdown ATC cells compared with the control cells. To our knowledge, this is the first report investigating the effect of LAMC2 on cell growth, cell cycle, migration, invasion, and EGFR signaling in ATC cells, suggesting that LAMC2 may be a potential therapeutic target for the treatment of ATC.

Insulin-like Growth Factor Receptor as a Therapeutic Target in Head and Neck Cancer

Insulin-like growth factor type I receptor (IGF-IR) plays critical roles in epithelial cancer cell development, proliferation, motility, and survival, and new therapeutic agents targeting IGF-IR are in development. Another receptor tyrosine kinase, the epidermal growth factor receptor (EGFR), is an established therapeutic target in head and neck cancer and IGF-IR/EGFR heterodimerization has been reported in other epithelial cancers. The present study was undertaken to determine the effects of anti-IGF-IR therapeutic targeting on cell signaling and cancer cell phenotypes in squamous cell carcinomas of the head and neck (SCCHN). The therapeutic efficacy of the human anti-IGF-IR antibody IMC-A12 alone and in combination with the EGFR blocking antibody cetuximab (C225) was tested in SCCHN cell lines and in tumor xenografts. IGF-IR was overexpressed in human head and neck cancer cell lines and tumors. Pretreatment of serum-starved 183A or TU159 SCCHN cell lines with A12 (10 microg/mL) blocked IGF-stimulated activation of IGF-IR, insulin receptor substrate (IRS)-1 and IRS-2, mitogen-activated protein kinase, and phosphatidylinositol 3-kinase. A12 induced G(0)-G(1) cell cycle arrest and blocked cell growth, motility, and anchorage-independent growth. Stimulation of head and neck cancer cells with either IGF or EGF resulted in IGF-IR and EGFR heterodimerization, but only IGF caused activating phosphorylation of both receptors. Combined treatment with A12 and the EGFR blocking antibody C225 was more effective at reducing cell proliferation and migration than either agent alone. Finally, TU159 tongue cancer cell xenografts grown in athymic nude mice were treated thrice weekly for 4 weeks with vehicle, A12 (40 mg/kg i.p.), C225 (40 mg/kg i.p.), or both agents (n=8 mice per group; 2 tumors per mouse). Linear regression slope analysis showed significant differences in median tumor volume over time between all three treatment groups and the control group. Complete regression was seen in 31% (A12), 31% (C225), and 44% (A12 + C225) of tumors. Here we found the overexpression of IGF-IR, the functional heterodimerization of IGF-IR and EGFR, and effective therapeutic targeting of these receptors in human head and neck cancer xenografts.

Hyaluronidase Expression Induces Prostate Tumor Metastasis in an Orthotopic Mouse Model

Molecular mechanisms of prostate cancer progression are frequently studied in mice by orthotopic injection of aggressive cell lines, which yield primary tumors that spontaneously metastasize to lymph nodes. In this report, we characterized the human prostate carcinoma cell line 22Rv1 in an orthotopic system and evaluated the functional relevance of the hyaluronidase Hyal1, a correlate of invasive human prostate cancer, to progression in this model. To provide real-time insights into these processes, we first validated use of an epidermal growth factor-conjugated fluorophore to illuminate orthotopic prostate tumors and their metastases in whole animal imaging. Animals receiving intraprostatic injections were tracked throughout a 6-week period. Tumor sizes were correlated 92% with total fluorescence intensities of 22 prostate tumors. In contrast to the highly tumorigenic and metastatic PC3M-LN4 cells, the 22Rv1 line was orthotopically tumorigenic but not metastatic, despite larger tumor sizes. Lymph node metastasis was successfully imaged in animals with PC3M-LN4 tumors on endpoint dissection. Stable transfection of 22Rv1 cells with Hyal1 did not alter growth kinetics of primary orthotopic tumors, but all animals implanted with Hyal1 transfectants exhibited tumor-positive para-aortic lymph nodes. Hyal1 is implicated as an inducer of prostate cancer metastatic progression.

Autocrine EGF receptor activation mediates endothelial cell migration and vascular morphogenesis induced by VEGF under interstitial flow

We show here that autocrine ligand activation of epidermal growth factor (EGF) receptor in combination with interstitial flow is critically involved in the morphogenetic response of endothelial cells to VEGF stimulation. Human umbilical vein endothelial cell (HUVEC) monolayers cultured on a collagen gel and exposed to low interstitial flow in the absence of EGF and VEGF remained viable and mitotic but exhibited little evidence of vascular morphogenesis. Addition of VEGF produced a flow-dependent morphogenetic response within 48 to 72 h, characterized by branched capillary-like structures. The response was substantially abolished by inhibitors related to the autocrine EGF receptor pathway including Galardin, AG1478, PD98059, and an EGF receptor-blocking antibody, indicating that regulation of the morphogenetic process operates via autocrine EGF receptor activation. Moreover, we observed that in our system the EGF receptor was always activated independently of the interstitial flow, and, in addition, the EGF receptor inhibitors used above reduced the phosphorylation state of the receptor, correlating with inhibition of capillary morphogenesis. Finally, 5'bromo-2'-deoxyuridine (BrdU) labeling identified dividing cells at the monolayer but not in the extending capillary-like structures. EGF pathway inhibitors Galardin and AG1478 did not reduce BrdU incorporation in the monolayer, indicating that the EGF-receptor-mediated morphogenetic behavior is mainly due to cell migration rather than proliferation. Based on these results, we propose a two-step model for in vitro capillary morphogenesis in response to VEGF stimulation with interstitial fluid flow: monolayer maintenance by mitotic activity independent of EGF receptors and a migratory response mediated by autocrine EGF receptor activation wherein cells establish capillary-like structures.

Phase III evaluation of radiation with and without cetuximab for locoregionally advanced head and neck cancer

Phase III evaluation of radiation with and without cetuximab for locoregionally advanced head and neck cancer

Epidermal Growth Factor Receptor Inhibition Promotes Desmosome Assembly and Strengthens Intercellular Adhesion in Squamous Cell Carcinoma Cells

The epidermal growth factor receptor (EGFR) has been proposed as a key modulator of cadherin-containing intercellular junctions, particularly in tumors that overexpress this tyrosine kinase. Here the EGFR tyrosine kinase inhibitor PKI166 and EGFR blocking antibody C225, both of which are used clinically to treat head and neck cancers, were used to determine the effects of EGFR inhibition on intercellular junction assembly and adhesion in oral squamous cell carcinoma cells. EGFR inhibition resulted in a transition from a fibroblastic morphology to a more epithelial phenotype in cells grown in low calcium; under these conditions cadherin-mediated cell-cell adhesion is normally reduced, and desmosomes are absent. The accumulated levels of desmoglein 2 (Dsg2) and desmocollin 2 increased 1.7-2.0-fold, and both desmosomal cadherin and plaque components were recruited to cell-cell borders. This redistribution was paralleled by an increase in Dsg2 and desmoplakin in the Triton-insoluble cell fraction, suggesting that EGFR blockade promotes desmosome assembly. Importantly, E-cadherin expression and solubility were unchanged. Furthermore, PKI166 blocked tyrosine phosphorylation of Dsg2 and plakoglobin following epidermal growth factor stimulation, whereas no change in phosphorylation was detected for E-cadherin and beta-catenin. The increase in Dsg2 protein was in part due to the inhibition of matrix metalloproteinase-dependent proteolysis of this desmosomal cadherin. These morphological and biochemical changes were accompanied by an increase in intercellular adhesion based on functional assays at all calcium concentrations tested. Our results suggest that EGFR inhibition promotes desmosome assembly in oral squamous cell carcinoma cells, resulting in increased cell-cell adhesion.

Interleukin-1beta-induced mucin production in human airway epithelium is mediated by cyclooxygenase-2, prostaglandin E2 receptors, and cyclic AMP-protein kinase A signaling.

We reported recently that interleukin (IL)-1beta exposure resulted in a prolonged increase in MUC5AC mucin production in normal, well differentiated, human tracheobronchial epithelial (NHTBE) cell cultures, without significantly increasing MUC5AC mRNA (Am J Physiol 286:L320-L330, 2004). The goal of the present study was to elucidate the signaling pathways involved in IL-1beta-induced MUC5AC production. We found that IL-1beta increased cyclooxygenase-2 (COX-2) mRNA expression and prostaglandin (PG) E(2) production and that the COX-2 inhibitor celecoxib suppressed IL-1beta-induced MUC5AC production. Addition of exogenous PGE(2) to NHTBE cultures also increased MUC5AC production and IL-1beta-induced Muc5ac hypersecretion in tracheas from wild-type but not from COX-2-/- mice. NHTBE cells expressed all four E-prostanoid (EP) receptor subtypes and misoprostol, an EP2 and EP4 agonist, increased MUC5AC production, whereas sulprostone, an EP1 and EP3 agonist, did not. Furthermore, specific protein kinase A (PKA) inhibitors blocked IL-1beta and PGE(2)-induced MUC5AC production. However, neither inhibition of epidermal growth factor receptor (EGFR) activation with the tyrosine kinase inhibitor 4-(3-chloroanilino)-6,7-dimethoxyquinazoline HCl (AG-1478) or EGFR blocking antibody nor inhibition of extracellular signal-regulated kinase/P-38 mitogen activated protein kinases with specific inhibitors blocked IL-1beta stimulation of MUC5AC mucin production. We also observed that tumor necrosis factor (TNF)-alpha, platelet activating factor (PAF), and lipopolysaccharide (LPS) induced COX-2 and increased MUC5AC production that was blocked by celecoxib, suggesting a common signaling pathway of inflammatory mediator-induced MUC5AC production in NHTBE cells. We conclude that the induction of MUC5AC by IL-1beta, TNF-alpha, PAF, and LPS involves COX-2- generated PGE(2), activation of EP2 and/or EP4 receptor(s), and cAMP-PKA-mediated signaling.

Cetuximab prolongs survival in patients with locoregionally advanced squamous cell carcinoma of head and neck: A phase III study of high dose radiation therapy with or without cetuximab

5507 Background: The majority of head and neck cancers overexpress the epidermal growth factor receptor (EGFR), which is associated with aggressive tumor behavior and poor clinical outcome. Preclinical in vitro and in vivo model systems demonstrate radiosensitization following molecular inhibition of EGFR signaling. Promising phase I/II clinical results were achieved when radiation was combined with the EGFR blocking antibody, cetuximab, in patients with locoregionally advanced squamous cell carcinoma (SCC) of the head and neck (H&N). This phase III international trial was designed to examine the impact of combining cetuximab with high dose radiation on locoregional disease control and survival in patients with locally advanced H&N cancer. Methods: Patients with locoregionally advanced SCC of the oropharynx, hypopharynx or larynx with measurable disease were eligible to enroll. Patients were stratified by Karnofsky score 60–80 vs. 90–100, node positive vs. negative, T1–3 vs. T4, radiation fractionation regimen (once-a-day vs. twice-a-day vs. concomitant boost), and were randomized to receive either radiation alone for 6–7 weeks, or radiation plus weekly cetuximab. Following completion of treatment, patients were followed by physical examination and radiographic imaging every 4 months for 2 years, and then every 6 months up to 5 years. Results: From 04/99 to 03/02, 424 patients were randomized on this trial in the USA (61%), Europe (28%), and other countries. Median age was 57; 80% were male; 69% had KPS 90–100; 60% had oropharyngeal, 25% laryngeal, and 15% hypopharyngeal primary tumors. The two treatment arms were well balanced with regard to patient characteristics and stratification factors. The two arms were also well balanced with respect to radiation dose and fractions received, use of post-radiotherapy neck dissection, and secondary cancer therapy. Minimum and median durations of follow-up were 24 and 38 months, respectively. Median survival times, two and three-year survival rates derive from Kaplan-Meier estimates. Survival and selected safety results are as follows: The overall toxicity profile was dominated by classic known effects of high dose H&N radiation, although some additional toxicity was attributed to cetuximab. Locoregional control assessment is ongoing. Conclusions: The addition of cetuximab to high dose radiation in patients with locoregionally advanced SCC of H&N demonstrated a statistically significant prolongation in overall survival. This clinical benefit was achieved with minimal enhancement in the overall toxicity profile associated with curative-intent radiation therapy. These results corroborate the promising preclinical and earlier phase clinical results supporting the use of EGFR blockade in combination with radiation for advanced SCC of H&N. Furthermore, this combination treatment should be explored in other common epithelial malignancies demonstrating EGFR overexpression. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration ImClone Systems ImClone Systems ImClone Systems ImClone Systems

Heparin blockade of thrombin-induced smooth muscle cell migration involves inhibition of epidermal growth factor (EGF) receptor transactivation by heparin-binding EGF-like growth factor.

Agonists of G protein-coupled receptors, such as thrombin, act in part by transactivating the epidermal growth factor (EGF) receptor (EGFR). Although at first a ligand-independent mechanism for EGFR transactivation was postulated, it has recently been shown that this transactivation by various G protein-coupled receptor agonists can involve heparin-binding EGF-like growth factor (HB-EGF). Because thrombin stimulation of vascular smooth muscle cell migration is blocked by heparin and because heparin can displace HB-EGF, we investigated the possibility that thrombin stimulation of smooth muscle cells (SMCs) depends on EGFR activation by HB-EGF. In rat SMCs, EGFR phosphorylation and extracellular signal-regulated kinase (ERK) activation in response to thrombin are inhibited not only by the EGFR inhibitor AG1478 and by EGFR blocking antibody but also by heparin and by neutralizing HB-EGF antibody. HB-EGF-dependent signaling induced by thrombin is inhibited by batimastat, which suggests a requirement for pro-HB-EGF shedding by a metalloproteinase. We further demonstrate that this novel pathway is required for the migration of rat and baboon SMCs in response to thrombin. We conclude from these data that the inhibitory effect of heparin on SMC migration induced by thrombin relies, at least in part, on a blockade of HB-EGF-mediated EGFR transactivation.

EGF-related peptides are involved in the proliferation and survival of MDA-MB-468 human breast carcinoma cells.

A majority of human breast carcinomas co-express the epidermal growth factor (EGF)-like peptides CRIPTO (CR), amphiregulin (AR) and transforming growth factor alpha (TGF-alpha). MDA-MB-468 breast carcinoma cells express CR, AR and TGFalpha, while SK-BR-3 cells express CR and TGF-alpha. Anti-sense phosphorothioate oligodeoxynucleotides (AS S-oligos) directed against either CR or TGF-alpha inhibit the proliferation of both cell lines. A 40-50% growth inhibition was observed at a 2-microM concentration of each AS S-oligo. Treatment with the AR AS S-oligo also resulted in a significant inhibition of MDA-MB-468 anchorage dependent growth (ADG). No significant growth inhibition was observed when MDA-MB-468 or SK-BR-3 cells were treated with a mis-sense S-oligo. The AS S-oligos inhibited the expression of AR, CR or TGF-alpha proteins and mRNAs, as assessed by immuno-cytochemistry and semi-quantitative RT-PCR. An additive growth-inhibitory effect was observed when MDA-MB-468 cells were treated with a combination of EGF-related AS S-oligos. Indeed, treatment of MDA-MB-468 cells with a combination of AR, CR and TGF-alpha AS S-oligos resulted in about 70% growth inhibition at a concentration of 0.7 microM each. Finally, treatment of MDA-MB-468 cells with a combination either of the 3 AS S-oligos or of an EGF receptor-blocking antibody (MAb 225) and either CR, AR or TGFalpha AS S-oligos resulted in a significant increase in DNA fragmentation. Our data suggest that the EGF-related peptides are involved in the proliferation and survival of breast carcinoma cells.

Expression of TGFalpha autocrine activity in human colon carcinoma CBS cells is autoregulated and independent of exogenous epidermal growth factor.

Autocrine transforming growth factor alpha (TGFalpha) activity and control mechanisms for its expression were examined in a representative clonal isolate (CBS4) of a well-differentiated human colon carcinoma cell line designated CBS. CBS4 cells expressed TGFalpha and its receptor, epidermal growth factor receptor (EGFr). Blockade of EGFr and TGFalpha by neutralizing antibodies inhibited clonal growth and the initiation of DNA synthesis from quiescence in CBS4 cells. Therefore, TGFalpha is an autocrine growth factor for CBS4 cells. Several studies have indicated that activation of the EGFr by exogenous EGF stimulates TGFalpha expression. However, in CBS4 cells EGF did not induce TGFalpha mRNA expression, indicating that EGF does not affect TGFalpha transcription in these cells. Exogenous treatment of exponentially growing cells with either EGF or EGFr blocking antibody enhanced release of TGFalpha protein into the conditioned medium. This indicated that the release of TGFalpha into the conditioned medium by exogenous EGF was at least partially due to the displacement of TGFalpha from the TGFalpha/EGFr complexes. Similarly to exponentially growing cells, the EGFr blocking antibody and EGF also enhanced TGFalpha release into the medium of CBS4 cells after release from quiescence. These results indicated that exogenous EGF had little if any effect on TGFalpha expression in these cells and suggested that TGFalpha expression might be under endogenous TGFalpha control. Blockade of the autocrine TGFalpha loop by TGFalpha neutralizing antibody suppressed TGFalpha mRNA both in exponentially growing and quiescent cells, demonstrating that autocrine TGFalpha is autoregulatory in this system.

Identification and biological characterization of an epidermal growth factor-related protein: cripto-1.

The human and mouse cripto-1 (CR-1) genes can code for proteins related in structure to epidermal growth factor (EGF). A specific 36-kDa immunoreactive protein was detected by Western blot analysis in human cell lines that express CR-1 mRNA but not in cell lines that fail to express this transcript. Immunoprecipitation of GEO colon carcinoma or mouse embryonal carcinoma cells detected 27-29-kDa and 24-kDa proteins, respectively. Cell lysates and conditioned medium that were prepared from several CHO clones and were expressing either a recombinant human or mouse CR-1 cDNA contained immunospecific 27-29-kDa and 24-kDa proteins, respectively. Monensin or tunicamycin treatment resulted in a shift of the 27-29-kDa human CR-1 protein to 24 kDa and 20 kDa, respectively. The 20-kDa protein was also observed after digestion of the 27-29-kDa human CR-1 protein with N-glycosidase F. Using two CR-1 synthetic refolded peptides that correspond to the EGF-like domain of the human CR-1 sequence or conditioned medium obtained from human CR-1 expressing CHO cells, growth stimulatory activity could be detected on non-transformed human mammary epithelial cells and on two human breast cancer cell lines. EGF receptor-blocking antibody did not inhibit the growth stimulatory action of the CR-1 protein. Likewise, the CR-1 refolded peptides or conditioned medium from the human CR-1-expressing CHO cells failed to inhibit the binding of 125I-EGF in an EGF-radioreceptor assay. These data demonstrate that the CR-1 is a glycoprotein that can function as a growth factor through an EGF receptor-independent pathway.

Interactions between epidermal growth factor-mediated autocrine regulation and linoleic acid-stimulated growth of a human prostate cancer cell line.

Human prostate cancer (PC) cell lines possess epidermal growth factor (EGF) receptors and secrete EGF-related polypeptides. We used an EGF receptor-blocking antibody (anti-EGF.R) to demonstrate a functional autocrine loop, as well as the interaction between this and the effects of linoleic acid (LA), an omega-6 fatty acid, on PC cell growth. The anti-EGF.R competed effectively with [125I]EGF for receptors on DU145 PC cells, and on a high-passage DU145 variant (DU145M); when added to the culture medium, it suppressed both DU145 and DU145M cell growth in a dose-dependent manner. LA, a precursor for eicosanoid synthesis, had little effect on DU145 cell growth rate but stimulated DU145M growth in a concentration-related manner over a range of 0.25-2.0 micrograms/ml. anti-EGF.R (10(-9) M) caused suppression of LA-stimulated growth of DU145M cells in serum-free medium, which was prevented by the addition of 2 nM EGF. We conclude that an EGF.R-mediated autocrine loop is involved in PC cell growth regulation and that at least one site of action may be the synthesis of eicosanoids from their LA precursor.