Fibroblast growth factor receptor 4 increases epidermal growth factor receptor (EGFR) signaling by inducing amphiregulin expression and attenuates response to EGFR inhibitors in colon cancer

Fibroblast growth factor receptor 4 (FGFR4) is known to induce cancer cell proliferation, invasion, and antiapoptosis through activation of RAS/RAF/ERK and PI3K/AKT pathways, which are also known as major molecular bases of colon cancer carcinogenesis related with epidermal growth factor receptor (EGFR) signaling. However, the interaction between FGFR4 and EGFR signaling in regard to colon cancer progression is unclear. Here, we investigated a potential cross‐talk between FGFR4 and EGFR, and the effect of anti‐EGFR therapy in colon cancer treatment. To explore the biological roles of FGFR4 in cancer progression, RNA sequencing was carried out using FGFR4 transfected colon cell lines. Gene ontology data showed the upregulation of genes related to EGFR signaling, and we identified that FGFR4 overexpression secretes EGFR ligands such as amphiregulin (AREG) with consequent activation of EGFR and ErbB3. This result was also shown in in vivo study and the cooperative interaction between EGFR and FGFR4 promoted tumor growth. In addition, FGFR4 overexpression reduced cetuximab‐induced cytotoxicity and the combination of FGFR4 inhibitor (BLU9931) and cetuximab showed profound antitumor effect compared to cetuximab alone. Clinically, we found the positive correlation between FGFR4 and AREG expression in tumor tissue, but not in normal tissue, from colon cancer patients and these expressions were significantly correlated with poor overall survival in patients treated with cetuximab. Therefore, our results provide the novel mechanism of FGFR4 in connection with EGFR activation and the combination of FGFR4 inhibitor and cetuximab could be a promising therapeutic option to achieve the optimal response to anti‐EGFR therapy in colon cancer.     

Mutations of epidermal growth factor receptor in colon cancer indicate susceptibility or resistance to gefitinib

Somatic mutations of the epidermal growth factor receptor (EGFR) gene may predict the sensitivity of non-small cell lung cancers to gefitinib. In our previous study, we identified somatic mutations in the tyrosine kinase domain of the EGFR gene in 12.1% of colon cancer cases. Herein, we focus on whether the mutations are associated with the sensitivity of colon cancer to gefitinib. The E749K mutation in exon 19 and E762G and A767T mutations in exon 20 were introduced into the full-length EGFR coding sequence in a pBKCMV-hEGFR vector by site-directed mutagenesis and transfected into LS174T cells. The sensitivity to gefitinib was compared between the transfected LS174T and the parental cells by a cytotoxic assay. The LS174T cells with E749K were significantly (p<0.05) more responsive to gefitinib than the parental cells. On the other hand, LS174T cells with E762G or A767T were significantly (p<0.05) more resistant than the parental cells. In conclusion, detection of somatic mutations in the epidermal growth factor receptor may play an important role in predicting sensitivity to gefitinib in colon cancer.     

Increased epidermal growth factor receptor (EGFR) expression in malignant mammary phyllodes tumors

Mammary phyllodes tumors are uncommon stromal-epithelial neoplasms, and are divided into benign, borderline malignant and frankly malignant groups on the basis of their histological features. Accumulating evidence shows that epidermal growth factor receptor (EGFR) is involved in the pathogenesis and progression of many malignancies. This study investigated 453 phyllodes tumors (296 benign, 98 borderline, 59 malignant) for EGFR expression using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) for gene amplification. The staining was correlated to tumor margin status, degree of malignancy, stromal cellularity, mitotic activity, nuclear pleomorphism and stromal overgrowth. Cases with strong positive IHC staining were selected for FISH. The overall positive rate for EGFR was 16.2% (48/296), 30.6% (30/98) and 56% (33/59) for benign, borderline malignant and frankly malignant phyllodes tumors, respectively. FISH demonstrated egfr gene amplification in 8% of immunohistochemically positive cases. The results of this study provide strong evidence that EGFR overexpression is involved in the pathogenesis of phyllodes tumors, although gene amplification may not be the major underlying mechanism for overexpression.     

Responses of cancer cells with wild-type or tyrosine kinase domain-mutated epidermal growth factor receptor (EGFR) to EGFR-targeted therapy are linked to downregulation of hypoxia-inducible factor-1α

Background  

Searching for novel molecular markers that dependably predict or indicate responses of human cancer cells to epidermal growth factor receptor (EGFR)-targeted therapy is strongly warranted. The purpose of the current study was to evaluate hypoxia-inducible factor-1α (HIF-1α) as a novel response marker compared with previously explored markers following treatment with an EGFR-blocking monoclonal antibody (cetuximab) and a small-molecule EGFR tyrosine kinase inhibitor (gefitinib) in a group of cancer cell lines containing wild-type or tyrosine kinase domain-mutated EGFR.     

Fulvestrant regulates epidermal growth factor (EGF) family ligands to activate EGF receptor (EGFR) signaling in breast cancer cells

Estrogen receptor-α (ER) targeted therapies are routinely used to treat breast cancer. However, patient responses are limited by resistance to endocrine therapy. Breast cancer cells resistant to the pure steroidal ER antagonist fulvestrant (fulv) demonstrate increased activation of epidermal growth factor receptor (EGFR) family members and downstream ERK signaling. In this study, we investigated the effects of fulv on EGFR signaling and ligand regulation in several breast cancer cell lines. EGFR/HER2/HER3 phosphorylation and ERK1,2 activation were seen after 24–48 h after fulvestrant treatment in ER-positive breast cancer cell lines. 4-Hydroxy-tamoxifen and estradiol did not cause EGFR activation. Fulvestrant did not affect EGFR expression. Cycloheximide abolished the ability of fulv to activate EGFR suggesting the autocrine production of EGFR ligands might be responsible for fulvestrant induced EGFR signaling. qRT-PCR results showed fulv differentially regulated EGFR ligands; HB-EGF mRNA was increased, while amphiregulin and epiregulin mRNAs were decreased. Fulvestrant induced EGFR activation and upregulation of EGFR ligands were ER dependent since fulv treatment in C4-12, an ER-negative cell line derivative of MCF-7 cells, did not result in EGFR activation or change in ligand mRNA levels. ER downregulation by siRNA induced similar EGFR activation and regulation of EGFR ligands as fulvestrant. Neutralizing HB-EGF antibody blocked fulv-induced EGFR activation. Combination of fulv and EGFR family tyrosine kinase inhibitors (erlotinib and lapatinib) significantly decreased EGFR signaling and cell survival. In conclusion, fulvestrant-activated EGFR family members accompanied by ER dependent upregulation of HB-EGF within 48 h. EGF receptor or ligand inhibition might enhance or prolong the therapeutic effects of targeting ER by fulvestrant in breast cancer.     

Activation of downstream epidermal growth factor receptor (EGFR) signaling provides gefitinib-resistance in cells carrying EGFR mutation

Patients with pulmonary adenocarcinoma carrying the epidermal growth factor receptor (EGFR) mutation tend to display dramatic clinical response to treatment with the EGFR tyrosine kinase inhibitor gefitinib. Unfortunately, in many cases the cancer cells eventually acquire resistance, and this limits the duration of efficacy. To gain insight into these acquired resistance mechanisms, we first prepared HEK293T cell line stably transfected with either wild-type (WT) or mutant (L858R) EGFR, and then expressed oncogenic K-Ras12V mutant in the latter transfectant. Although 293T cells expressing wild-type EGFR did not show any growth inhibition by gefitinib treatment similarly to the non-transfected cells, the cells expressing the EGFR-L858R were exquisitely sensitive. Consistently, phospho-Akt levels were decreased in response to gefitinib in cells expressing EGFR-L858R but not in cells with EGFR-WT. In contrast, 293T cells expressing both EGFR-L858R and oncogenic K-Ras were able to proliferate even in the presence of high concentration of gefitinib probably by inducing Erk1/2 activation. We also expressed K-Ras12V in the gefitinib-sensitive pulmonary adenocarcinoma cell line PC-9, which harbors an in-frame deletion in the EGFR gene. The activated K-Ras inhibited the effects of gefitinib treatment on cell growth, cell death induction and levels of phospho-Akt, as well as phospho-Erk. These data indicate that activated Ras could substitute most of the upstream EGFR signal, and are consistent with the hypothesis that mutational activation of targets immediately downstream from the EGFR could induce the secondary resistance to gefitinib in patients with lung cancer carrying EGFR mutation.     

Nuclear localization of epidermal growth factor receptor (EGFR) in ameloblastomas

Background: Ameloblastoma is a locally invasive neoplasm often associated with morbidity and facial deformities, showing increased Epidermal Growth Factor Receptor (EGFR) expression. Inhibition of EGFR was suggested as a treatment option for a subset of ameloblastomas. However, there are resistance mechanisms that impair anti-EGFR therapies. One important resistance mechanism for EGFR-inhibition is the EGFR nuclear localization, which activates genes responsible for its mitogenic effects, such as Cyclin D1.Methods: We assessed EGFR nuclear localization in encapsulated (unicystic, n = 3) and infiltrative (multicystic, n = 11) ameloblastomas and its colocalization with Cyclin D1 by using anti-EGFR and anti-lamin B1 double labeling immunofluorescence analyzed by confocal microscopy. Oral inflammatory fibrous hyperplasia and oral squamous cell carcinoma samples were used for comparison.Results: Twelve cases of ameloblastoma exhibited nuclear EGFR colocalization with lamin B1. This positive staining was mainly observed in the ameloblast-like cells. The EGFR nuclear localization was also observed in control samples. In addition, nuclear EGFR colocalized with Cyclin D1 in ameloblastomas.Conclusions: Nuclear EGFR occurs in ameloblastomas in association with Cyclin D1 expression, which is important in terms of tumor biology clarification and raises a concern about anti-EGFR treatment resistance in ameloblastomas.     

Inhibition of Hsp90 down-regulates mutant epidermal growth factor receptor (EGFR) expression and sensitizes EGFR mutant tumors to paclitaxel

Mutations in the kinase domain of the epidermal growth factor receptor (EGFR) are found in a subset of patients with lung cancer and correlate with response to EGFR tyrosine kinase inhibitors (TKI). Resistance to these agents invariably develops, and current treatment strategies have limited efficacy in this setting. Hsp90 inhibitors, such as 17-allylamino-17-demethoxygeldanamycin (17-AAG), induce the degradation of EGFR and other Hsp90 interacting proteins and may thus have utility in tumors dependent upon sensitive Hsp90 clients. We find that the EGFR mutations found most commonly in patients with lung adenocarcinoma who respond to EGFR TKIs are potently degraded by 17-AAG. Although the expression of wild-type EGFR was also down-regulated by 17-AAG, its degradation required higher concentrations of drug and a longer duration of drug exposure. In animal models, a single dose of 17-AAG was sufficient to induce degradation of mutant EGFR and inhibit downstream signaling. 17-AAG treatment, at its maximal tolerated dose, caused a significant delay in H3255 (L858R EGFR) xenograft growth but was less effective than the EGFR TKI gefitinib. 17-AAG alone delayed, but did not completely inhibit, the growth of H1650 and H1975 xenografts, two EGFR mutant models which show intermediate and high levels of gefitinib resistance. 17-AAG could be safely coadministered with paclitaxel, and the combination was significantly more effective than either drug alone. These data suggest that Hsp90 inhibition in combination with chemotherapy may represent an effective treatment strategy for patients whose tumors express EGFR kinase domain mutations, including those with de novo and acquired resistance to EGFR TKIs.     

Toll-like receptor agonists and invariant natural killer T-cells enhance antibody-dependent cell-mediated cytotoxicity (ADCC)

huHMFG-1 (AS1402) is a humanised IgG1 against MUC1, which exerts tumour cell killing through antibody-dependent cellular cytotoxicity (ADCC) mediated by natural killer (NK) cells. Here, we explored the capacity of invariant NKT (iNKT) cells, which are known to activate NK cells, and toll-like receptor (TLR) ligands which activate both iNKT and NK cells, to enhance huHMFG-1-ADCC. Addition of iNKT cells, as well as TLR2/6, 7, 8 and 9 agonists to PBMC improved the efficacy of huHMFG-1. These results suggest that transfer of ex vivo expanded iNKT cells or TLR agonist treatment may improve the efficacy of NK cell-mediated antibody-based tumour immunotherapies.     

Cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR) expression in human pituitary macroadenomas

Macroadenomas are tumors of the pituitary gland and are considered almost to be always benign and curable. The clinical manifestations of a pituitary tumor depend on the hormone secreted by the tumor as well as on the pattern of tumor growth within the sella turcica. Current trends attempt to target new molecular markers that also may serve as potential therapeutic targets. Cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR) are upregulated in a number of epithelial tumors. No published reports exist about expression of COX-2 in pituitary macroadenomas, and only a few reports with differing results exist concerning EGFR expression in pituitary macroadenomas. This study sought to determine whether a relationship exists between COX-2 and EGFR expression and pituitary macroadenomas. Thirty specimens of pituitary macroadenomas were evaluated after being identified in the surgical pathology database of Thomas Jefferson University Hospital. The hematoxylin and eosin-stained slides were reviewed, and the representative paraffin blocks containing the index case were chosen and immunohistochemically stained for COX-2 and EGFR expression. The COX-2 and EGFR-stained slides were reviewed and an immunohistochemical score was calculated and analyzed. The pituitary macroadenomas were classified on the basis of hormone expression: none (nonsecreting), minor (nondominant, plurihormonal), single (dominant nonplurihormonal), or plurihormonal (dominant plurihormonal). The hormonal classification was then analyzed for association with COX-2 expression. COX-2 expression was significantly associated with plurihormonal pituitary macroadenomas (p value 0.03). COX-2 expression was significantly associated with expression of luteinizing hormone (p value 0.007) and with expression of thyroid-stimulating hormone (TSH) (p value 0.04). Additionally, COX-2 expression was significantly associated with single-hormone of pituitary adenoma (p value 0.049). The expression of COX-2 in 100% of the normal autopsy pituitary glands establishes an additional central nervous system location of COX-2 expression. EGFR was not expressed in any of the pituitary macroadenomas. The expression of COX-2 in plurihormonal pituitary macroadenomas, particularly those secreting TSH, may be a potential target for treatment in addition to surgical and/or radiotherapy treatment in these benign but clinically significant tumors. COX-2 is expressed in normal autopsy pituitary tissue.     

酒精对乳腺癌细胞表皮生长因子受体-钙激活中性蛋白酶通路及细胞迁移的影响

背景与目的：酒精(ethyl alcohol,EtOH)可促进乳腺癌的恶性演进,但其信号机制尚未完全明了。本研究通过观察EtOH对乳腺癌细胞钙激活中性蛋白酶(calcium-activated neutral protease,CANP)-周期蛋白E/局部黏着斑激酶(focal adhesion kinase,FAK)信号通路和细胞迁移的影响,以及表皮生长因子受体(epidermal growth factor receptor,EGFR)在其中的介导作用,探讨EtOH促进乳腺癌细胞迁移的信号机制。方法：以人乳腺肿瘤细胞系MCF-7为模型细胞(MCF-10A乳腺上皮细胞为对照);采用蛋白[质]印迹法(Western blot)分析周期蛋白E和FAK蛋白剪切反应;通过伤口愈合实验观察细胞迁移效应;采用EGFR抑制剂(EGFR inhibitor, EGFR-I)或CANP抑制剂Calpeptin抑制EGFR或CANP活性,观察抑制剂对EtOH诱导CANP1大亚基、周期蛋白E/FAK蛋白剪切及细胞迁移的影响。结果：以EtOH(0.3%)处理模型细胞可观察到周期蛋白E和FAK出现明显蛋白剪切且该效应呈剂量和时间依赖性,还观察到EtOH刺激细胞迁移活动(+47.30%,P<0.05),但EtOH对MCF-10A细胞迁移无明显影响;以Calpeptin(10μmol/L)预处理模型细胞,可见EtOH(0.3%)或EGF(10 ng/mL)诱导的周期蛋白E/FAK蛋白剪切效应受到明显抑制;EGFR-I(3μmol/L)可显著抑制EtOH诱导的CANP1大亚基和周期蛋白E/FAK蛋白剪切及细胞迁移效应(-53.00%,P<0.01)。结论：EtOH可通过EGFR激活乳腺癌细胞CANP信号活动并促进细胞迁移,EGFR-CANP通路参与介导EtOH与EGF之间的串话,提示EGFR-CANP信号通路中的关键分子可为防止乳腺癌转移的潜在药物靶点。     

Molecular mechanisms of epidermal growth factor receptor (EGFR) activation and response to gefitinib and other EGFR-targeting drugs.

The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases, including EGFR, HER2/erbB2, and HER3/erbB3, is an attractive target for antitumor strategies. Aberrant EGFR signaling is correlated with progression of various malignancies, and somatic tyrosine kinase domain mutations in the EGFR gene have been discovered in patients with non-small cell lung cancer responding to EGFR-targeting small molecular agents, such as gefitinib and erlotinib. EGFR overexpression is thought to be the principal mechanism of activation in various malignant tumors. Moreover, an increased EGFR copy number is associated with improved survival in non-small cell lung cancer patients, suggesting that increased expression of mutant and/or wild-type EGFR molecules could be molecular determinants of responses to gefitinib. However, as EGFR mutations and/or gene gains are not observed in all patients who respond partially to treatment, alternative mechanisms might confer sensitivity to EGFR-targeting agents. Preclinical studies showed that sensitivity to EGFR tyrosine kinase inhibitors depends on how closely cell survival and growth signalings are coupled with EGFR, and also with HER2 and HER3, in each cancer. This review also describes a possible association between EGFR phosphorylation and drug sensitivity in cancer cells, as well as discussing the antiangiogenic effect of gefitinib in association with EGFR activation and phosphatidylinositol 3-kinase/Akt activation in vascular endothelial cells.     

(-)-Epigallocatechin gallate causes internalization of the epidermal growth factor receptor in human colon cancer cells

We recently found that the inhibitory effect of (-)-epigallocatechin gallate (EGCG) on epidermal growth factor (EGF) binding to the epidermal growth factor receptor (EGFR) is associated with alterations in lipid organization in the plasma membrane of colon cancer cells. Since changes in lipid organizations are thought to play a role in the trafficking of several membrane proteins, in this study we examined the effects of EGCG on cellular localization of the EGFR in SW480 cells. Treatment of the cells for 30 min with as little as 1 microg/ml of EGCG caused a decrease in cell surface-associated EGFRs and this was associated with internalization of EGFRs into endosomal vesicles. Similar effects were seen with a green fluorescent protein (GFP)-EGFR fusion protein. As expected, the EGFR protein was phosphorylated at tyrosine residues, ubiquitinated and partially degraded when the cells were treated with EGF, but treatment with EGCG caused none of these effects. The loss of EGFRs from the cell surface induced by treating the cells with EGF for 30 min persisted for at least 2 h. However, the loss of EGFRs from the cell surface induced by temporary exposure to EGCG was partially restored within 1-2 h. These studies provide the first evidence that EGCG can induce internalization of EGFRs into endosomes, which can recycle back to the cell surface. This sequestrating of inactivated EGFRs into endosomes may explain, at least in part, the ability of EGCG to inhibit activation of the EGFR and thereby exert anticancer effects.     

Transforming growth factor alpha and epidermal growth factor levels in bladder cancer and their relationship to epidermal growth factor receptor.

We have examined levels of epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) in neoplastic and non-neoplastic bladder tissue using a standard radioimmunoassay technique. Tumour samples had much higher TGF-alpha levels compared with EGF and TGF-alpha levels in malignant tissue were significantly higher than in benign bladder samples. There was, in addition, a difference in mean EGF levels from ''normal'' bladder samples from non-tumour bearing areas of bladder in patients with bladder cancer compared with ''normal'' bladder tissue obtained at the time of organ retrieval surgery. Levels of EGF and TGF-alpha did not correlate with levels of EGF receptor (EGFR) as determined by a radioligand binding method but levels of TGF-alpha > 10 ng gm-1 of tumour tissue did correlate with EGFR positivity defined using immunohistochemistry. These data suggest that TGF-alpha is the likely ligand for EGFR in bladder tumours.     

Claudin-2 expression increases tumorigenicity of colon cancer cells: role of epidermal growth factor receptor activation

Claudin-2 is a unique member of the claudin family of transmembrane proteins, as its expression is restricted to the leaky epithelium in vivo and correlates with epithelial leakiness in vitro. However, recent evidence suggests potential functions of claudin-2 that are relevant to neoplastic transformation and growth. In accordance, here we report, on the basis of analysis of mRNA and protein expression using a total of 309 patient samples that claudin-2 expression is significantly increased in colorectal cancer and correlates with cancer progression. We also report similar increases in claudin-2 expression in inflammatory bowel disease-associated colorectal cancer. Most importantly, we demonstrate that the increased claudin-2 expression in colorectal cancer is causally associated with tumor growth as forced claudin-2 expression in colon cancer cells that do not express claudin-2 resulted in significant increases in cell proliferation, anchorage-independent growth and tumor growth in vivo. We further show that the colonic microenvironment regulates claudin-2 expression in a manner dependent on signaling through the EGF receptor (EGFR), a key regulator of colon tumorigenesis. In addition, claudin-2 expression is specifically decreased in the colon of waved-2 mice, naturally deficient in EGFR activation. Furthermore, genetic silencing of claudin-2 expression in Caco-2, a colon cancer cell line, prevents the EGF-induced increase in cell proliferation. Taken together, these results uncover a novel role for claudin-2 in promoting colon cancer, potentially via EGFR transactivation.