Epidermal Growth Factor Receptor In Breast Cancer Research Articles

Nuclear EGFR in breast cancer suppresses NK cell recruitment and cytotoxicity.

Natural Killer (NK) cells can target and destroy cancer cells, yet tumor microenvironments typically suppress NK cell recruitment and cytotoxicity. The epidermal growth factor receptor (EGFR) is a potent oncogene that can activate survival, migration, and proliferation pathways, and clinical data suggests it may also play an immunomodulating role in cancers. Recent work has demonstrated a novel role for nuclear EGFR (nEGFR) in regulating transcriptional events unique from the kinase domain. Using a novel peptide therapeutic (cSNX1.3) that inhibits retrograde trafficking of EGFR and an EGFR nuclear localization mutant, we discovered that nEGFR suppresses NK cell recruitment and cytotoxicity. RNA-Seq analysis of breast cancer cells treated with cSNX1.3 or modified to lack a nuclear localization sequence (EGFRΔNLS) revealed the EGF-dependent induction of NK activating receptor ligands, while kinase inhibition by erlotinib did not impact these genes. NanoString analysis of tumor-bearing WAP-TGFα transgenic mice treated with cSNX1.3 demonstrated an increase in immune cell populations and activating genes. Additionally, immunohistochemistry confirmed an increase in NK cells upon cSNX1.3 treatment. Finally, cSNX1.3 treatment was found to enhance NK cell recruitment and cytotoxicity in vitro. Together, the data demonstrate a unique immunomodulatory role for nEGFR.

Abstract LB133: EGFR upregulation in breast cancer cells: A key mechanism of escape from antiestrogen induced death, autophagy, and senescence

Abstract EGFR is upregulated commonly in multiple cancer types, including breast cancer. However, the multiple role(s) of EGFR in breast cancer are not fully elucidated. In this study, we characterized a unique antiestrogen resistant breast cancer subline and provide compelling data that upregulation of the EGFR/MEK1/MAPK1/2 signaling axis during antiestrogen treatment facilitated escape from senescence, autophagy, and BimEL-dependent apoptosis. Our studies were conducted with the antiestrogen resistant TR5 cell line established by our laboratory, using a step-wise drug selection with the antiestrogen 4-hydroxytamoxifen (4-OHT) of the estrogen receptor α (ER+) MCF-7 breast cancer cells. A preliminary microarray comparing mRNA expression between 4-OHT-selected TR5 cells and MCF-7 parent cells identified upregulation of the epidermal growth factor receptor (EGFR). Western blot showed a greater than 5-fold upregulation of EGFR expression and downregulation of estrogen receptor alpha (ERα) compared to the levels in MCF-7 and T47-D (antiestrogen sensitive). Selective inhibition of EGFR, phosphorylated at Tyr 1068, was achieved with erlotinib. Inhibition blocked MEK1/MAPK1/2 signaling, which was also upregulated in 4-OHT selected TR5 cells, with detectable increases in the pro-apoptotic BH3 protein BimEL, and a fifty percent reduction in cell viability. However, a high number of cells survived erlotinib therapy due to autophagy induction determined to be cytoprotective. Autophagy induction was identified by analyzing the expression/turnover of autophagy proteins LC3-II and p62, a standard approach to ascertain autophagy levels in cells. Further, erlotinib treatment induced a 2-fold increase in the number of senescent cells in the surviving population. Senescent cells were identified by β-galactosidase staining of erlotinib-treated cells utilizing confocal microscopy. Interestingly, blockade of autophagy with the lysosomotrophic compound chloroquine enhanced the senescence cell population, suggesting that either autophagy blocked senescence induction or lysosome impairment increased senescence. Mechanistically, we have identified phosphorylated AMP-activated protein kinase (pAMPK) as being elevated under conditions of erlotinib treatment, and reduced in 4-OHT-selected TR5 cells relative to MCF-7 parent cells. This correlation supports the hypothesis that pAMPK was downregulated during 4-OHT selection of TR5 cells by elevated EGFR/MEK/MAPK1/2 signaling to allow surviving cells escape senescence induction and/or anti-proliferative autophagy. Overall we propose that EGFR mediated downregulation of pAMPK is a major regulatory pathway in breast cancer cells surviving endocrine treatment. Our current studies are dissecting the role of EGFR-mediated AMPK regulation with somatic cell-based studies and pharmacological intervention. Citation Format: Mackenzie L. Hagan, Michael McGrath, Carol Joseph, Allison Lewis, John R. Barrett, Muthusamy Thangaraju, David Gewirtz, Patricia V. Schoenlein. EGFR upregulation in breast cancer cells: A key mechanism of escape from antiestrogen induced death, autophagy, and senescence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB133.

CD44 correlates with clinicopathological characteristics and is upregulated by EGFR in breast cancer.

Cluster of differentiation 44 (CD44), a well-known transmembrane glycoprotein, serves as a promoting factor in the carcinogenesis and progression of a variety of neoplasms. Previous studies have demonstrated that aberrant expression of CD44 was associated with the initiation, invasion, metastasis, and therapy-resistance of breast cancer, but whether there was any association between CD44 and pathological characteristics of breast cancer or epidermal growth factor receptor (EGFR) has not been clearly elucidated. In this study, we utilized public microarray data analysis and tissue microarray technologies to display that CD44 level was enhanced in breast cancer and was significantly correlated with histological grade and the status of estrogen receptor, progesterone receptor and human epidermal growth factor receptor-2 (HER2) and EGFR. Furthermore, mRNA expression of CD44 in breast tumors was positively correlated with basal cytokeratin markers KRT5 and KRT17, but inversely associated with luminal marker FOXA1. Besides, Kaplan-Meier analysis showed that high CD44 mRNA level had adverse impact on the progression-free survival of patients with HER2-expressing or basal-like breast cancer. Functionally, inhibition of EGFR activity by erlotinib impaired the invasion and migration ability of breast cancer cell lines. Western blot assays demonstrated that erlotinib treatment decreased the expression of CD44, accompanied with the reduced protein levels of mesenchymal and cancer stem cell markers. Collectively, this study suggested that the expression of CD44 was upregulated by EGFR pathway and CD44 had a robust impact on the development of breast cancer.

Expression of PTEN, p53 and EGFR in the molecular subtypes of breast carcinoma and the correlation among them

To study the expression of PTEN, p53 and epidermal growth factor receptor (EGFR) in the molecular subtypes of breast carcinoma and to evaluate the correlations with triple-negative breast cancer. Immunohistochemical MaxVision(TM) method was used to detect the expression of PTEN, p53, EGFR, estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) in 291 cases of infiltrating ductal carcinoma of breast. The positive expression of PTEN, p53 and EGFR protein in breast carcinoma was 57.0%, 57.0% and 38.5%, respectively, which were significantly different from those in benign breast diseases (P<0.05). The expression of PTEN or EGFR in breast cancer was correlated with tumor size, histological grade, lymph node metastasis, TNM stage, ER and HER2 status (P<0.05); the expression of p53 was correlated with tumor size, histological grade and ER status (P<0.05). The difference of positive expression rates of PTEN, p53 and EGFR protein among different subtypes including luminal A, luminal B (HER2-), luminal B (HER2+), HER2 over-expression and triple-negative was statistically significant (P<0.05). There were close correlations among PTEN, p53 and EGFR in the triple-negative subtype (P<0.05). Low expression of PTEN and high expression of EGFR and p53 are observed in triple-negative breast cancer, which may synergistically contribute to the pathogenesis of triple-negative breast cancer.

Clinical significance of serum epidermal growth factor receptor (EGFR) levels in patients with breast cancer

Epidermal growth factor receptor (EGFR) plays an important role in the pathogenesis of multiple malignancies and its expression strongly also affects the outcomes of cancer patients. The objective of this study was to determine the clinical significance of the serum levels of EGFR in breast cancer (BC) patients. A total of 96 patients with a pathologically confirmed diagnosis of BC were enrolled into this study. Serum EGFR levels were determined by the solid-phase sandwich ELISA method. Age and sex matched 30 healthy controls were included in the analysis. Median age of diagnosis was 48years old (range: 29–80). Thirty-seven (39%) consisted of metastatic disease. The baseline serum EGFR levels were significantly higher than in the healthy control group (p<0.001). The serum EGFR concentrations were also significantly higher only in patients with ER-negative and triple-negative tumor (p=0.05 and p=0.04, respectively). The other known clinical variables, including grade of histology, stage of disease, serum CA 15.3 levels, and response to chemotherapy were not found to be correlated with serum EGFR concentrations (p>0.05). Likewise, serum EGFR levels were found to play no prognostic role for survival (p=0.35). In conclusion, while serum EGFR levels were elevated in BC patients, EGFR level has no predictive and prognostic value in these patients.

Abstract 4267: MUC1 increases epidermal growth factor receptor levels and signaling in endometrial cancer cell lines.

Abstract Endometrial cancer is the most common gynecological cancer, affecting over 600,000 women in the United States. Furthermore, increased incidence of endometrial cancer is observed among obese and premenopausal women. Currently, the standard of care is hysterectomy with the addition of radiation and chemotherapy for late stage cancers. Novel therapies are required to avoid surgical complications associated with obese patients and to preserve the fertility of young patients. MUC1 is a large, heavily glycosylated transmembrane protein that functions to lubricate mucosal surfaces, protect cells from external insult and modulates the embryo implantation process. Recent evidence suggests that the C-terminus of MUC1 is involved in intracellular signaling through interaction with several cancer-associated proteins. One of these proteins is the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase that influences cellular proliferation, migration and apoptosis. Elevated MUC1 levels are associated with increased levels and signaling of EGFR in breast cancer; however, this phenomenon has not been described in the context of endometrial cancer and the mechanisms involved are not well understood in any context. To this end, human endometrial cancer cell lines were subjected to siRNA knockdown of MUC1 followed by qRT-PCR, western blotting, EGFR promoter-driven luciferase assays, proliferation and migration assays. These assays demonstrate a correlation of MUC1 levels with EGFR mRNA levels, protein levels, signaling, gene expression and cellular proliferation and migration. These results demonstrate that MUC1 control of EGFR levels and signaling also occurs in endometrial cancer-derived cell lines. Future experiments will elucidate the mechanisms by which MUC1 promotes EGFR gene expression and signaling in endometrial cancer. These insights may provide novel MUC1-based targets for endometrial cancer therapies which when used in conjunction with current non-surgical treatments may provide a therapeutic strategy that avoids surgical complications and preserves fertility. (Work supported by NIH grants RO1 HD 29963 and NCI 2P5098258-06 as well as Rice University funds to DDC). Citation Format: Brian J. Engel, Daniel D. Carson. MUC1 increases epidermal growth factor receptor levels and signaling in endometrial cancer cell lines. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4267. doi:10.1158/1538-7445.AM2013-4267

Very low prevalence of epidermal growth factor receptor (EGFR) protein expression and gene amplification in Saudi breast cancer patients.

BackgroundBreast cancers which demonstrate EGFR protein expression, gene amplification and/or gene mutations may benefit therapeutically from tyrosine kinase inhibitors. In Western studies, EGFR protein expression has been demonstrated in 7-36% of breast cancer patients, while gene amplification has been found in around 6% of cases and mutations were either absent or extremely rare. Studies addressing EGFR protein expression and gene amplification in Saudi breast cancer patients are extremely scanty and the results reported have been mostly non-conclusive. Herein we report the prevalence of EGFR protein expression and gene amplification in a cohort of Saudi breast cancer patients.FindingsWe noticed a remarkably low incidence of EGFR protein expression (1.3%) while analyzing the spectrum of molecular subtypes of breast cancer in a Saudi population by immunohistochemistry. Also, EGFR gene amplification could not be demonstrated in any of 231 cases studied using silver enhanced in situ hybridization.ConclusionsThe extremely low incidence of EGFR protein expression and gene amplification in Saudi breast cancer patients as compared to Western populations is most probably ethnically related as supported by our previous finding in the same cohort of a spectrum of molecular breast cancer types that is unique to the Saudi population and in stark contrast with Western and other regionally based studies. Further support to this view is provided by earlier studies from Saudi Arabia that have similarly shown variability in molecular breast cancer subtype distribution between Saudi and Caucasian populations as well as a predominance of the high-grade pathway in breast cancer development in Middle East women. More studies on EGFR in breast cancer are needed from different regions of Saudi Arabia before our assumption can be confirmed, however.

Quantum dot-based quantitative immunofluorescence detection and spectrum analysis of epidermal growth factor receptor in breast cancer tissue arrays

BackgroundThe epidermal growth factor receptor (EGFR) is a promising therapeutic target in cancer, but its clinical value in breast cancer remains controversial. Our previous studies have found that quantitative analysis of biomarkers with quantum dot-based nanotechnology had better detection performance than conventional immunohistochemistry. The present study was undertaken to investigate the prognostic value of EGFR in breast cancer using quantum dot-based quantitative spectral analysis.MethodsEGFR expression in 65 breast cancer specimens was detected by immunohistochemistry and quantum dot-immunohistochemistry, and comparisons were made between the two methods. EGFR expression in tissue microarrays of 240 breast cancer patients was then detected by quantum dot-immunohistochemistry and spectral analysis. The prognostic value of EGFR immunofluorescence area (EGFR area) for five-year recurrence-free survival was investigated.ResultsThe same antigen localization, high correlation of staining rates (r = 0.914), and high agreement of measurement (κ = 0.848) of EGFR expression in breast cancer were found by quantum dot-immunohistochemistry and immunohistochemistry. The EGFR area showed significant differences by tumor grade, lymph node status, HER2 status, and hormone receptor status (all P < 0.05). Patients in the large EGFR area (≥30.51) group had a significantly higher five-year recurrence rate (47.2% versus 27.4%, P = 0.002) and worse five-year recurrence-free survival (log-rank test, P = 0.0015) than those in the small EGFR area (<30.51) group. In the subgroups, EGFR area was an independent prognosticator in the HER2-positive and lymph node-positive subgroups.ConclusionQuantum dot-based quantitative detection demonstrates the prognostic value of EGFR area in the HER2-positive and lymph node-positive subgroups of invasive breast cancer.

Over-expression of EGFR in breast cancer

ObjectiveTo explore the relationship of overexpression of epidermal growth factor receptor (EGFR) in occurrence, development and treatment of breast cancer.MethodsSamples of 46 breast adenoma tissues and 86 breast cancer tissues were regularly dehydrate-fixed, embedded in paraffin, sliced in to 5 μm thick, stained with SABC immunohistochemistry and coloured with DAB.ResultsThe positive staining of EGFR was shown as brown-yellow and distributed in cytoplasm. The positive rates in the tissues of breast adenosis and breast cancer were 17.04% (6/46) and 56.98% (49/86) respectively. The positive rates of EGFR in the tissue of invasive ductal carcinoma was 64.49% (41/59), which was significantly higher than that in in situ carcinoma (P<0.05). The positive rate of lymph metastasis group was higher than that in non-lymph metastasis group (P<0.05).ConclusionThe overexpression of EGFR was related with occurrence, lymph metastasis and pathologic types of breast cancer. The examination of EGFR in the breast cancer can serve as a guidance for target chemotherapy.

Epidermal Growth Factor Receptor Status in Breast Cancer Metastases to the Central Nervous System

Abstract Context.—The development of drug therapies (ZD1839) targeting epidermal growth factor receptor (EGFR) offers a pragmatic reason for exploring expression of EGFR in breast cancer, particularly metastatic breast cancer. There is a reported synergistic relationship between trastuzumab and ZD1839 therapy in patients with breast cancer. Although EGFR is the preferred dimerization partner for HER-2, it is unclear whether expression of these 2 interrelated receptors in a given patient with breast cancer would be parallel or mutually exclusive. Objectives.—To assess EGFR status in primary breast carcinoma versus metastatic central nervous system (CNS) sites and to compare results with HER-2/neu status in the same tumor. Design.—Central nervous system metastases (n = 51) from 33 patients and corresponding primary breast cancer specimens, when available (n = 11), were immunohistochemically stained for EGFR using a monoclonal mouse anti-EGFR antibody (clone 31G7) that recognizes both the wild-type form and the 145-kd variant III form of EGFR. The sections were evaluated by visual and image analysis techniques, and results were compared to previously assessed HER-2/neu status. Results.—Epidermal growth factor receptor expression was found in CNS metastases from 39% of patients, with 82% concordance between the EGFR status of the primary breast and metastatic sites, and 92% concordance between the EGFR status among multiple CNS metastases in a given patient. Epidermal growth factor receptor and HER-2/neu status were concordant at the primary site in only 45% of patients. Additionally, EGFR and HER-2/neu status were concordant among multiple CNS metastases per individual case in only 45% of patients. Conclusion.—Thirty-nine percent of patients with metastatic breast cancer express EGFR, with parallel expression between metastatic sites and the primary neoplasm in 82% of the cases. The discordance in 18% of the cases, however, suggests that anti-EGFR agents might not show equal efficacy against metastatic tumor deposits and the primary tumor within a given patient. An additional corollary for pathologists based on this nonhomogeneity of receptor expression is that both the primary breast and multiple metastatic tumor deposits may need to be individually assessed for EGFR status. In our study, most metastatic tumor deposits showed expression for either EGFR or HER-2/neu, and less often for both, implying that drug therapies could be individualized for patients based on test results for both receptors.

Prognostic value of the combination of epidermal growth factor receptor and c-erbB-2 in breast cancer

Background. Epidermal growth factor receptor (EGFR) and c-erbB-2 are 2 of the 4 members of the erbB receptor family that play a role in signaling by forming heterodimers between family members. Methods. The immunohistochemical expression of EGFR and c-erbB-2 was determined on 670 women who underwent operation for primary breast cancer. Results. According to the combination of EGFR and c-erbB-2, 670 patients were classified into 4 groups: EGFR(−)/c-erbB-2(−) (417 patients); EGFR(+)/c-erbB-2(−) (136 patients); EGFR(−)/c-erbB-2(+) (72 patients); and EGFR(+)/c-erbB-2(+) (45 patients). Univariate analyses on disease-free and overall survival showed a significant difference among these 4 groups, whereas the difference between patients with positive and negative expression of EGFR was not statistically significant in patients with positive expression of c-erbB-2. A multivariate analysis indicated the combination of EGFR and c-erbB-2 to be an independently significant prognostic factor for disease-free and overall survival. Conclusions. Breast cancer with both a positive EGFR and c-erbB-2 expression had the worst prognosis, whereas the prognostic value of c-erbB-2 was stronger than that of EGFR in breast cancer. (Surgery 2003;133:219-21.)

Proximal Events in Signaling by Plasma Membrane Estrogen Receptors

Estradiol (E2) rapidly stimulates signal transduction from plasma membrane estrogen receptors (ER) that are G protein-coupled. This is reported to occur through the transactivation of the epidermal growth factor receptor (EGFR) or insulin-like growth factor-1 receptor, similar to other G protein-coupled receptors. Here, we define the signaling events that result in EGFR and ERK activation. E2-stimulated ERK required ER in breast cancer and endothelial cells and was substantially prevented by expression of a dominant negative EGFR or by tyrphostin AG1478, a specific inhibitor for EGFR tyrosine kinase activity. Transactivation/phosphorylation of EGFR by E2 was dependent on the rapid liberation of heparin-binding EGF (HB-EGF) from cultured MCF-7 cells and was blocked by antibodies to this ligand for EGFR. Expression of dominant negative mini-genes for Galpha(q) and Galpha(i) blocked E2-induced, EGFR-dependent ERK activation, and Gbetagamma also contributed. G protein activation led to activation of matrix metalloproteinases (MMP)-2 and -9. This resulted from Src-induced MMP activation, implicated using PP2 (Src family kinase inhibitor) or the expression of a dominant negative Src protein. Antisense oligonucleotides to MMP-2 and MMP-9 or ICI 182780 (ER antagonist) each prevented E2-induced HB-EGF liberation and ERK activation. E2 also induced AKT up-regulation in MCF-7 cells and p38beta MAP kinase activity in endothelial cells, blocked by an MMP inhibitor, GM6001, and tyrphostin AG1478. Targeting of only the E domain of ERalpha to the plasma membrane resulted in MMP activation and EGFR transactivation. Thus, specific G proteins mediate the ability of E2 to activate MMP-2 and MMP-9 via Src. This leads to HB-EGF transactivation of EGFR and signaling to multiple kinase cascades in several target cells for E2. The E domain is sufficient to enact these events, defining additional details of the important cross-talk between membrane ER and EGFR in breast cancer.

Dual Inhibition of Focal Adhesion Kinase and Epidermal Growth Factor Receptor Pathways Cooperatively Induces Death Receptor-mediated Apoptosis in Human Breast Cancer Cells

The focal adhesion kinase (FAK) and epidermal growth factor receptor (EGFR) are protein-tyrosine kinases that are overexpressed and activated in human breast cancer. To determine the role of EGFR and FAK survival signaling in breast cancer, EGFR was stably overexpressed in BT474 breast cancer cells, and each signaling pathway was specifically targeted for inhibition. FAK and EGFR constitutively co-immunoprecipitated in EGFR-overexpressing BT474 cells. In low EGFR-expressing BT474-pcDNA3 vector control cells, inhibition of FAK by the FAK C-terminal domain caused detachment and apoptosis via pathways involving activation of caspase-3 and -8, cleavage of poly(ADP-ribose) polymerase, and caspase-3-dependent degradation of AKT. This apoptosis could be rescued by the dominant-negative Fas-associated death domain, indicating involvement of the death receptor pathway. EGFR overexpression did not inhibit detachment induced by the FAK C-terminal domain, but did suppress apoptosis, activating AKT and ERK1/2 survival pathways and inhibiting cleavage of FAK, caspase-3 and -8, and poly(ADP-ribose) polymerase. Furthermore, this protective effect of EGFR signaling was reversed by EGFR kinase inhibition with AG1478. In addition, inhibition of FAK and EGFR in another breast cancer cell line (BT20) endogenously overexpressing these kinases also induced apoptosis via the same mechanism as in the EGFR-overexpressing BT474 cells. The results of this study indicate that dual inhibition of FAK and EGFR signaling pathways can cooperatively enhance apoptosis in breast cancers.

Identification and characterization of a negative regulatory element within the epidermal growth factor receptor gene first intron in hormone-dependent breast cancer cells.

The epidermal growth factor receptor (EGFR) exhibits an inverse correlation with estrogen receptor (ER) expression in the majority of breast cancers, predicting a poor response to endocrine therapy and poor survival rate. Inappropriate overexpression of EGFR in breast cancer is associated with a more aggressive phenotype. Transcriptional regulation is the major regulatory mechanism controlling EGFR overexpression in breast cancer cells. We have identified a region within the first intron of the EGFR gene that mediates transcriptional repression of EGFR gene expression in ER +/low EGFR expressing but not in ER-/high EGFR expressing breast cancer cells. Utilizing transient transfections of homologous and heterologous promoter-reporter constructs, we localized optimal repressive activity to a 96 bp intron domain. The 96 bp fragment displayed differential DNA-protein complex formation with nuclear extracts from ER + vs. ER- breast cancer cells. Moreover, factors interacting with this intron negative regulatory element appear to be estrogen-regulated. Consequently, our results suggest that we have identified a potential mechanism by which maintenance of low levels of EGFR expression and subsequent EGFR upregulation may be attributed to the loss of transcriptional repression of EGFR gene expression in hormone-dependent breast cancer cells.

Expression of TGF-alpha and EGFR in Breast Cancer and its Relation to Angiogenesis.

Immunohistochemical analysis of the expression of transforming growth factor alpha (TGF-alpha) and its receptor, epidermal growth factor receptor (EGFR), was performed in a series of 86 invasive carcinomas of the breast. TGF-alpha immunostaining was observed in the majority of the cases (72.1%), both in epithelial cells and in adjacent stromal cells. EGFR was also present in tumors (34.2%) and in the endothelial cells (46.1% of the cases) near the tumors. A significant association was observed between TGF-alpha expression and angiogenesis evaluated by immunohistochemistry using an antibody against factor VIII-related antigen. No association was observed between TGF-alpha expression and other clinicopathologic features. In contrast, EGFR expression in the tumor was associated with features of poor prognosis, such as tumor size, histologic grade, lymph node status, estrogen receptor content, p53 expression, sialyl-Tn expression, and age. The presence of EGFR in endothelial cells was correlated to young patient age. We also observed an association of EGFR in endothelial cells and angiogenesis in tumors with a size of less than 2 cm. Inversely, in larger tumors, angiogenesis was only associated with tumor TGF-alpha expression. These results indicate that endothelial EGFR may play a role in the early steps of breast cancer angiogenesis.