Epidermal Growth Factor Receptor ErbB1 Research Articles

Lapatinib in combination with capecitabine in the management of ErbB2-positive (HER2-positive) advanced breast cancer.

Lapatinib is an oral, reversible, dual inhibitor of epidermal growth factor receptor ErbB1 (EGFR) and human epidermal growth factor receptor type 2 ErbB2 (HER2). Results of a phase III study comparing lapatinib plus capecitabine with capecitabine alone in women with ErbB2-overexpressing advanced breast cancer previously treated with an anthracycline, a taxane, and trastuzumab were reported early based on superiority of the combination in prolonging time to tumor progression (TTP). An updated analysis in 399 women supports the earlier findings. In this updated analysis, TTP (hazard ratio [HR] 0.57) favored lapatinib plus capecitabine. Survival trended in favor of the combination. The incidence of cardiac events was numerically higher in the combination arm (5 cases in the combination arm, 2 cases in the monotherapy arm).

Moving Through an Electrical Field

Breast cancer cells tend to first move into the lumen of the mammary ducts, where they proliferate. Then, after tissue deformation occurs, the cells breach the basement membrane and metastasize through the lymph and blood vessels. Pu et al . propose that the transepithelial potential, with the duct lumen having a relatively positive charge, creates an endogenous electric field that contributes to the movement of cancer cells. The authors used electric fields that were smaller than those that should exist across the breast duct epithelium based on the transepithelial potential to test whether breast cancer cell lines responded to the presence of such an electric field. The authors noted a correlation between the metastatic potential of human and rat mammary cancer cell lines and directional migration in the presence of an electric field (the cells moved toward the anode). The abundance of the epidermal growth factor receptor ErbB1 also correlated with directed migration in an electric field, and inhibition of ErbB1 with AG1478 profoundly reduced electric field-induced directed migration. Overexpression of ErbB1, ErbB2, or ErbB3 increased directed migration of two mammary tumor cell lines in response to an electric field. Pharmacological inhibitors were used to explore the signaling pathway responsible for migration, and tyrosine kinase activity, phosphatidylinositol 3-kinase, RhoA, Cdc42, and extracellular signal-regulated kinase (ERK) were all involved. J. Pu, C. D. McCaig, L. Cao, Z. Zhao, J. E. Segall, M. Zhao, EGF receptor signaling is essential for electric-field-directed migration of breast cancer cells. J. Cell Sci. 120 , 3395-3403 (2007). [Abstract] [Full Text]

Herceptin Sensitizes ErbB2–Overexpressing Cells to Apoptosis by Reducing Antiapoptotic Mcl-1 Expression

Monoclonal antibodies, such as herceptin and trastuzumab, against the epidermal growth factor receptor ErbB2 (also known as HER2/neu) are an effective therapy for breast cancer patients with overexpression of ErbB2. Herceptin, in combination with standard chemotherapy, such as taxol or etoposide, gives a synergistically apoptotic response in breast tumors. The mechanism underlying this synergy between chemotherapy and herceptin treatment is not well understood. Herein, we have determined that addition of herceptin, sensitized breast cancer cell lines MDA-MB-231 and MCF-7 to etoposide- or taxol-induced apoptosis. This treatment resulted in reduced expression of ErbB2 and the antiapoptotic Bcl-2 family member Mcl-1 in MDA-MB-231 cells. Using antisense oligonucleotides against Mcl-1, MDA-MB-231 cells were rendered sensitive to etoposide-induced apoptosis similar to herceptin, but combined treatment of antisense against Mcl-1 and herceptin failed to give a significant increase in apoptosis. In 29 human breast tumors immunostained for ErbB2 and Mcl-1, we found that when ErbB2 was overexpressed, there was a corresponding increase in Mcl-1 expression. Using murine fibroblasts that express human ErbB2, but no other ErbB family member (NE2), these cells showed resistance to both taxol- and etoposide-induced apoptosis compared with parental cells. In addition, NE2 cells preferentially express the antiapoptotic Bcl-2 family member Mcl-1 compared with parental cells, and treatment with herceptin reduces Mcl-1 expression. Taken together, these results suggest that herceptin sensitizes ErbB2-overexpressing cells to apoptosis by reducing antiapoptotic Mcl-1 protein levels.

Syndecan-1 Is Essential for the Myeloma Cell Growth Factor Activity of EGF-Family Ligands in Multiple Myeloma.

Aim was to assess the role of the epidermal growth factor (EGF)/EGF receptor (ErbB1 (EGFR), ErbB2, ErbB3 and ErbB4) family in the pathogenesis of multiple myeloma (MM) investigating (i) their expression profile and (ii) their functional activity. Comparing Affymetrix DNA-microarray-expression-profiles of CD138-purified plasma-cells from 65 MM patients and 7 normal individuals to those of plasmablastic- and B-cells, we found 5/10 EGF-family genes to be overexpressed in myeloma cells (MMC). Two of them -neuregulin(NRG)-2 and NRG-3- were expressed by MMC only, while other three -NRG-1, amphiregulin (AREG) and TGF-α- were expressed by both MMC and normal bone marrow (BM) plasma cells (PCs). In addition, using real-time PCR, we found 4/10 EGF-ligands -HB-EGF, AREG, NRG-1 and epiregulin- to be expressed by cells from the BM-environment. ErbB receptors were expressed by normal and malignant plasma cells but were lacking on plasmablastic- and B-cells. ErbB1 and ErbB2 were expressed by MMC and BMPC, whereas ErbB3 and ErbB4 were expressed by MMC exclusively. The growth of myeloma cell lines was promoted by EGF-ligands able to bind heparan sulfate (HS) proteoglycans (PGs), i.e. NRG-1, amphiregulin and HB-EGF, but not by other EGF-ligands, i.e. EGF, TGF-α, epiregulin and betacellulin. Proliferation induced by HS-binding EGF-ligands was completely abrogated when the growth factors where pre-incubated with heparin. A truncated form of NRG-1 that lacks the HS-binding domain but has kept the ErbB binding domain was unable to promote MMC growth. MMC could bind large levels of HS-binding EGF-ligands through syndecan-1, which is expressed on myeloma cells at a high density contrary to other 10 HSPGs -syndecan-2-4, glypican-1-6 and CD44v3-. The binding was abrogated by either pre-treatment with heparitinase (which cleaves HS chains), or pre-incubation of the growth factors with heparin. None of the EGF-ligands could bind or induce proliferation of the XG-10 myeloma cell line which doesn't express syndecan-1. Thus, EGF/EGF-receptor genes are expressed during plasma cell differentiation and malignant transformation: MMC express ErbB receptors and several HS-binding EGF-ligands. Cells from the BM-environment can also be a source of EGF-family members delivering a paracrine growth signal to MMC. Myeloma cell growth is stimulated by EGF-ligands that bind HS, via binding to syndecan-1, which likely concentrates high levels of HS-binding-EGF-ligands in the proximity of ErbB receptors at the cell membrane and therefore facilitates ErbB-activation. This accumulation of EGF-family members at cell membrane is required to promote their myeloma cell growth activity. We have previously shown that pan-ErbB inhibitors like CI-1033 induce strong apoptosis of primary MMC cultured with their bone-marrow environment. Together with these data, this further recommends EGF-signalling as promising target for MM therapy.

The Inhibitory Effect of ErbB2 on Epidermal Growth Factor-induced Formation of Clathrin-coated Pits Correlates with Retention of Epidermal Growth Factor Receptor-ErbB2 Oligomeric Complexes at the Plasma Membrane

By constructing stably transfected cells harboring the same amount of epidermal growth factor (EGF) receptor (EGFR), but with increasing overexpression of ErbB2, we have demonstrated that ErbB2 efficiently inhibits internalization of ligand-bound EGFR. Apparently, ErbB2 inhibits internalization of EGF-bound EGFR by constitutively driving EGFR-ErbB2 hetero/oligomerization. We have demonstrated that ErbB2 does not inhibit phosphorylation or ubiquitination of the EGFR. Our data further indicate that the endocytosis deficiency of ErbB2 and of EGFR-ErbB2 heterodimers/oligomers cannot be explained by anchoring of ErbB2 to PDZ-containing proteins such as Erbin. Instead, we demonstrate that in contrast to EGFR homodimers, which are capable of inducing new clathrin-coated pits in serum-starved cells upon incubation with EGF, clathrin-coated pits are not induced upon activation of EGFR-ErbB2 heterodimers/oligomers.

Under Pressure to Increase EGF

Tschumperlin et al. investigated the effects of compressive stress on epithelial cells and uncovered an intriguing mechanism whereby mechanical stimuli could provoke a biochemical response by modulating extracellular-fluid volume. Bronchial epithelial cells undergo compressive stress during airway constriction; this stimulates the production of proinflammatory and profibrotic cytokines, a response that may contribute to the pathogenesis of asthma. Tschumperlin et al. used Western analysis to show that transcellular pressure applied to cultured human bronchial epithelial (HBE) cells promoted phosphorylation of extracellular signal-regulated kinase (ERK). The authors used pharmacological analysis and function-blocking antibodies to demonstrate that ERK phosphorylation required metalloprotease-dependent shedding of the heparin-binding epidermal growth factor (HB-EGF) ectodomain. This led to autocrine stimulation of the ErbB1 epidermal growth factor receptor, which was present on the basolateral surfaces of HBE surrounding the lateral intercellular spaces (LIS) between cells. Two-photon microscopy revealed that transcellular pressure substantially decreased the volume of the LIS, without affecting cell volume per se. Exposure to different concentrations of soluble HB-EGF elicited increases in ERK phosphorylation consistent with increases in the local concentration of HB-EGF in the LIS predicted on the basis of the observed changes in volume. Thus, pressure appears to modulate bronchial epithelial cell signaling through a localized increase in the concentration of ligand, a mechanism that could apply to other systems with similar morphology. D. J. Tschumperlin, G. Dai, I. V. Maly, T. Kikuchi, L. H. Lalho, A. K. McVittie, K. J. Haley, C. M. Lilly, P. T. C. So, D. A. Lauffenburger, R. D. Kamm, J. M. Drazen, Mechanotransduction through growth-factor shedding into the extracellular space. Nature 429 , 83-86 (2004). [Online Journal]

Metalloprotease-dependent ErbB ligand shedding in mediating EGFR transactivation and vascular remodelling.

AngII (angiotensin II) and its G-protein-coupled AT(1) receptor play critical roles in mediating cardiovascular diseases such as hypertension, atherosclerosis and restenosis after vascular injury. It is widely believed that AngII promotes these diseases by inducing vascular remodelling that involves hypertrophy, hyperplasia and migration of VSMCs (vascular smooth muscle cells). We have shown that transactivation of an ErbB family receptor, EGFR (epidermal growth factor receptor; ErbB1), is essential for VSMC hypertrophy and migration induced by AngII. However, the precise signal transduction mechanism by which AngII transactivates EGFR/ErbB1 and whether other ErbBs are also required for AngII function remains unclear. Recent studies suggest an involvement of a metalloprotease-dependent ErbB family ligand production in the transactivation. Here, we will discuss the roles and mechanisms of AngII/AT(1) receptor in promoting ErbB receptors transactivation in VSMCs. Further elucidation of this ErbB activation machinery not only will give us a better understanding of the critical molecular mechanism underlying vascular remodelling stimulated by AngII, but will also contribute to development of novel treatment strategies for cardiovascular diseases.

EGF stimulates rat spermatogonial DNA synthesis in seminiferous tubule segments in vitro

Epidermal growth factor (EGF) superfamily of peptide growth factors (EGF-GFs) plays a role in male germ cell development, but the precise function is yet to be defined. The present study shows that EGF-GFs stimulate spermatogonial proliferation in vitro. The EGF-GF ligands, EGF, transforming growth factor-α and betacellulin all stimulated DNA synthesis in microdissected stage I segments of rat testis seminiferous tubules in vitro, as revealed by 3H-thymidine incorporation and 5-bromo-2′-deoxyuridine (BrdU) labeling. A fourfold increase over control of BrdU labeled cells, identified as spermatogonia, was seen after treatment with EGF. RT-PCR analysis revealed that the EGF receptors erbB1, erbB2, erbB3 and erbB4 were expressed at all stages of the spermatogenic wave, whereas differential expression was found in isolated Leydig, Sertoli and peritubular cells. The results show that EGF-GFs is spermatogonial growth factor(s) in vitro, although we have not discriminated between a direct action and an indirect effect via somatic cells. We suggest that EGF-GFs is involved in the paracrine control of spermatogenesis in vivo.

Increased expression of the type 1 growth factor receptor family in the conjunctival epithelium of patients with keratoconjunctivitis sicca

PURPOSE: To investigate the expression of type 1 growth factor receptors (epidermal growth factor receptor, ErbB2, and ErbB3) in the conjunctival epithelium of patients with keratoconjunctivitis sicca. METHODS: Immunofluorescent staining and Western blotting were performed to grade the level of expression of the epidermal growth factor receptor ErbB2, and ErbB3 in conjunctival epithelial impression cytologies taken from both eyes of seven normal subjects and 22 patients with keratoconjunctivitis sicca. RESULTS: Epidermal growth factor receptor staining was observed in a greater percentage of keratoconjunctivitis sicca than normal samples ( P < .05). ErbB2 and ErB3 staining in the apical conjunctival epithelium was observed in both groups, but stronger ErbB2 and ErbB3 staining was noted in keratoconjunctivitis sicca conjunctival samples ( P < .05). The relative levels of expression of these receptor proteins on immunoblots were consistent with immunofluorescent staining. On immunoblots, epidermal growth factor receptor protein was detected in 50% of keratoconjunctivitis sicca samples, but none of the normal samples ( P < .025). The expression of ErbB2 and ErbB3 on immunoblots was also greater in the keratoconjunctivitis sicca samples ( P < .05). Immunofluorescent staining scores for these receptors were correlated with conjunctival lissamine green staining scores (r = .574, P < .01 for epidermal growth factor receptor; r = .620, P < .0025 for ErbB2; r = .502, P < .025 for ErbB3) and with corneal fluorescein staining (r = .409, P < .05 for ErbB2; r = .588, P < .005 for ErbB3). CONCLUSION: The expression of the type 1 growth factor receptors is significantly greater in the conjunctival epithelium of eyes with keratoconjunctivitis sicca than normal eyes. The increased expression of these receptors was positively correlated with ocular surface dye staining. The increased expression of these receptors may contribute to the abnormal growth and differentiation of the conjunctival epithelium that occurs in keratoconjunctivitis sicca.

Studies on the betacellulin receptor in pancreatic AR42J cells.

Betacellulin is a member of the epidermal growth factor family and converts pancreatic AR42J cells into insulin-producing cells. This study was conducted to characterise the receptor for betacellulin in AR42J cells. AR42J cells expressed two classes of binding sites for radioactive iodine labelled betacellulin, with Kd values of 4.6 x 10(-11) mol/l and 3.0 x 10(-10) mol/l. The binding of [125I]betacellulin was inhibited by unlabelled betacellulin in a dose-dependent manner, but epidermal growth factor was 50 fold less effective than betacellulin. Affinity cross-linking showed a [125I]betacellulin-binding protein with a molecular weight of approximately 180 KDa. When this protein was immunoprecipitated with antibody against epidermal growth factor receptors ErbB-1, ErbB-2, ErbB-3 or ErbB-4, it was immunoprecipitated only by the anti-ErbB-1 antibody. When the [125I]betacellulin-labelled proteins were immunoprecipitated with a combination of the four ErbB antibodies, and the unprecipitated proteins were then immunoprecipitated with anti-phosphotyrosine antibody, a 190 KDa protein was observed. Betacellulin induced the tyrosine phosphorylation of ErbB-1, ErbB-2 and ErbB-4. Finally, while 100 pmol/1 betacellulin converted all of the AR42J into insulin-producing cells in the presence of activin A, 10 nmol/l epidermal growth factor induced differentiation in only about 30 % of the cells. Higher concentrations of epidermal growth factor were less effective. Neu differentiation factor in the presence or absence of epidermal growth factor was ineffective. These results indicate that betacellulin binds to ErbB-1 and possibly another protein with a molecular weight of 190 KDa. The latter betacellulin-binding protein may be involved in the differentiation-inducing activity of betacellulin.