In Silico Identification of Novel Flavonoids Targeting Epidermal Growth Factor Receptor.

Regorafenib, a tyrosine kinase inhibitor (TKI), is used in the treatment of unresectable hepatocellular carcinoma (HCC). However, the occurrence of acquired resistance limits its antitumor efficacy. While multiple studies have highlighted the crucial role of bypass activation in acquired TKI resistance, few have focused on bypass activation in regorafenib resistance in HCC. High-throughput proteomics was used to identify differential proteins associated with bypass activation between acquired regorafenib-resistant cells and parental cells. The ability of epidermal growth factor receptor (EGFR) bypass inhibition to reverse resistance was evaluated both in vitro and in vivo using direct microscopic observation, the CCK-8 assay, colony formation assay, Annexin V-FITC/propidium iodide double staining, cell cycle analysis, western blotting, and a xenograft model. The expression of EGFR, a member of the receptor tyrosine kinase (RTK) family, was significantly increased in acquired regorafenib-resistant HCC cells compared with parental cells. Pharmacological inhibition of EGFR with gefitinib restored the sensitivity of regorafenib-resistant HCC cells to regorafenib. In a xenograft mouse model, gefitinib sensitized resistant tumors to regorafenib. Additionally, levels of RAS, RAF, and P-ERK1/2, components of the downstream EGFR signaling pathway, were positively associated with EGFR expression. EGFR overexpression promotes acquired resistance to regorafenib through RAS/RAF/ERK bypass activation in HCC. Inhibition of EGFR restores sensitivity to regorafenib, and the combination of gefitinib and regorafenib demonstrates significant antitumor efficacy both in vivo and in vitro. These findings suggest that this combination could be a potential strategy for patients with advanced HCC.

Mammalian cells develop various transmembrane receptors including the family of receptor tyrosine kinases (RTKs) to respond to extracellular stimuli. Epidermal growth factor receptor (EGFR) is the first identified member of the RTKs and it plays a pivotal role in colorectal cancer by stimulating cell proliferation and survival. Binding of extracellular ligands, mainly EGF, leads to the dimerization of EGFR that triggers the activation of downstream mitogen activated protein kinases. In addition to the amount of ligand binding, the strength and duration of EGFR signaling are also affected by the posttranslational modifications of the receptor itself, such as phosphorylation, ubiquitination, acetylation, etc. In the previous study, we demonstrated that Sulfiredoxin (Srx) enhances the EGFR signaling in colorectal cancer cells through the inhibition of receptor acetylation at lysine residue 1061. However, the molecular mechanism by which Srx regulates the level of EGFR acetylation is still unclear. In this study, we investigated (1) the mechanism of EGFR acetylation and its regulation by Srx; (2) the functional consequence of EGFR acetylation on EGF-induced receptor dimerization, recycling, trafficking and degradation. Human colon cancer cell lines were cultured and maintained in standard conditions. Western blotting, immunoprecipitation and Mass spectrometry were used to identify cysteine oxidation of HDAC6 and characterize enzymes that are involved in the acetylation of EGFR. Stable cells that overexpress or loss of target genes, such as Srx, HDAC6, EGFR and/or mutants, were established using the 3rd generation lentiviral ShRNA infection or the CRISPR-Cas9 system. The activity of histone deacetylases was determined using commercial kit in the presence/absence of pan- or isoform-specific chemical inhibitors of HDACs. Upon EGF stimulation, the dimerization, recycling, trafficking and degradation of EGFR were demonstrated through a combination of immunoblotting, flow-cytometry and immunofluorescent imaging. We demonstrated that HDAC6 plays a central role in the regulation of EGFR acetylation through its interaction with EGFR. Depletion of Srx in human colon cancer cells increases the levels of intracellular reactive oxygen species, leading to inhibition of HDAC6 activity through regulating the redox state of cysteines 407/417. Depletion of HDAC6 not only leads to increased level of EGFR acetylation but also suppresses the binding between EGFR and its adaptor proteins. EGF-induced receptor dimerization and recycling are altered in HDAC6 knockout cells, result in inhibition of EGFR downstream signaling. Taken together, this study indicates that Srx enhances the strength and duration of EGF signaling through the ROS-HDAC6-EGFR axis in human colon cancer cells. Citation Format: Qi Ying, Hong Jiang, B. Mark Evers, Qiou Wei. Histone deacetylase 6 plays a critical role in sulfiredoxin-mediated activation of the epidermal growth factor receptor signaling in human colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2644.

Non-small cell lung cancer (NSCLC) is one of the most lethal types of cancer and is associated with significant mortality and morbidity worldwide. Despite improvements in conventional treatment for NSCLC, survival remains poor and improvements in patient outcome are warranted. Over recent years, basic scientific research has dramatically increased our knowledge of the pathogenesis of lung cancer and allowed us to uncover and understand the cellular pathways involved in this process. This has led to the development of therapies to selectively target these pathways. Among these, the epidermal growth factor receptor (EGFR) tyrosine kinase family and related downstream pathways play a critical role in cancer development and over recent years have become a validated target in NSCLC. The development of monoclonal antibodies and first-generation tyrosine kinase inhibitors (TKIs) targeted towards EGFR has had a considerable impact on patient outcomes. However, despite dramatic and sustained responses and the discovery of specific patient subgroups that may derive clinical benefit, resistance to first-generation EGFR TKIs inevitably develops. A new generation of agents have been developed to provide superior potency of target inhibition and further individualize the treatment of NSCLC. This article reviews EGFR-targeted therapies currently available for use and undergoing clinical development for the treatment of NSCLC, specifically focusing on next generation agents including BIBW 2992, an irreversible dual inhibitor of EGFR and HER2 kinases.

14071 Background: Triple-negative BrCa lacks expression of hormone receptors and HER-2 but does express EGFR. It is associated with early relapse and poor survival. There is no targeted therapy for triple-negative BrCa. We are studying the potential role of EGFR inhibition. Methods: EGFR expression was examined in triple-negative BrCa cell lines, (BT20, HCC1937, and MDA-MB-231) by western blot. IC50 assays were determined for three EGFR inhibitors, gefitinib (G) and erlotinib (T), which are small-molecule tyrosine kinase inhibitors, and cetuximab (E) which is a monoclonal antibody against EGFR, and chemotherapy (CRx) drugs docetaxel (D) and carboplatin (P)), using the acid phosphatase assay. The controls were HER2+ BrCa cell lines, BT474 and SKBR3 which express low levels of EGFR. Results: The three triple-negative cell lines over-express EGFR. IC50 values for G and T were significantly higher in the triple-negative than in the HER2+ cell lines. E did not cause significant inhibition in any cell line (max inhibition 20% at 100 μg/ml E). IC50 values for G were lower than for T in the triple-negative cell lines (IC50s for HCC1937: G - 8.4 ± 1.5 μM; T - 26.2 ± 9.3 μM). Combined EGFR inhibition with CRx was tested in HCC1937 cells. G combined with P or with D for 5 days showed an additive effect on inhibition of proliferation ( Table 1 ). Alternate scheduling of the drugs did not significantly influence response. Conclusions: Our results suggest that triple-negative BrCa cells over-express EGFR but are not as sensitive to EGFR inhibition as HER2+ BrCa cells. However, EGFR inhibition may enhance response to CRx in triple-negative BrCa. [Table: see text] No significant financial relationships to disclose.

FGFR4 increases EGFR oncogenic signaling in lung adenocarcinoma, and their combined inhibition is highly effective

Virtually any molecule can serve as a target for therapy. The ideal target, however, is present only on abnormal cells, allowing normal cells to be spared from the treatment effect. Rituximab was the first monoclonal antibody approved by the United States Food and Drug Administration for the treatment of cancer. It is a chimeric human/murine monoclonal anti-CD20 immunoglobulin G1 (IgG1) antibody. CD20 is a cell surface protein expressed on most B cells but not on uncommitted hematopoietic precursor cells. Rituximab is approved for the treatment of B-cell lymphoma. Rituximab has also been used successfully in the treatment of other lymphoprolif-erative disorders in the orbit, including lymphoid hyperplasia Ibritumomab is a murine IgG1 anti-CD20 antibody. It can be coupled with tiuxetan, a chelator, and ibritumomab tiuxetan can bind yttrium-90 to form yttrium-90-labeled ibritumomab tiuxetan (hereafter referred to as ibritumomab; Zevalin) [32]. In a trial comparing rituximab to rituximab plus ibritumomab for refractory or relapsed follicular or low-grade non-Hodgkin lymphoma, response rates were 56% for rituximab alone and 80% for the combination. In a prospective trial, 12 patients underwent combined treatment with rituximab and ibritumomab as front-line treatment for stage I-E ocular adn-exal lymphoma. Ten patients had a complete response, and two had a partial response. There was one local recurrence during the follow-up period; there were no distant relapses[14]. Imatinib mesylate (imatinib; Gleevec) is a selective tyrosine kinase inhibitor used in the treatment of chronic myeloid leukemia (CML) and gastrointestinal stromal tumors. Edema is the most commonly seen adverse effect associated with imatinib mesylate, and the periorbital region is the most common site for edema. In a phase I trial of imatinib for the treatment of gastrointestinal stromal tumor, edema of the periorbital region or eyelids was seen in 55.1% of the 174 patients treated. Rarely, the edema can be so severe that surgical treatment is required. Cetuximab is a monoclonal antibody directed against epidermal growth factor receptor (EGFR), a member of the ErbB family of tyrosine kinase receptors. Cetuximab is used in the treatment of colon cancer and head and neck squamous cell carcinoma (SCC). Although SCC in the head and neck can involve the orbit, we found no published reports of cetuximab used in the treatment of periorbital SCC at the time of preparation of this chapter. However, there have been reports of EGFR expression in conjunctival SCC as well as in both ocular and extraocular sebaceous gland carcinomas, suggesting a potential role for EGFR inhibitors in treatment of conjunctival SCC, and sebaceous gland carcinoma of the eyelid. A common ocular side effect of cetuximab and other EGFR inhibitors is trichomegaly

Introduction: Use of both the vascular endothelial growth factor (VEGF) inhibitor bevacizumab and the epidermal growth factor receptor (EGFR) inhibitors cetuximab and panitumumab as potential first-line therapies for patients with RAS-wild-type metastatic colorectal cancer presents clinicians with an important decision. We review clinical data evaluating first-line treatment with EGFR inhibitors. Additionally, by undertaking an integrated ‘bench-to-bedside’ approach, we provide potential models, testable hypotheses and biological rationales that might account for these clinical observations.Areas covered: A literature search encompassing PubMed and the ASCO/ESMO websites was undertaken in October 2014. Search terms included ‘colorectal cancer’, ‘cetuximab’, ‘panitumumab’ and ‘bevacizumab’.Expert opinion: A number of clinical studies indicate a survival benefit for patients receiving EGFR inhibitors in combination with chemotherapy in the first-line setting, relative to both chemotherapy alone and VEGF inhibitors plus chemotherapy. Existing preclinical and clinical data suggest that a biological basis exists for providing RAS-wild-type patients with first-line EGFR inhibitors, followed by second-line VEGF inhibitors. More specifically, first-line treatment with EGFR inhibitors may elicit unique biological changes that sensitize tumors to subsequent lines of therapy; conversely, first-line treatment with VEGF inhibitors may elicit biological changes that desensitize tumors to subsequent lines of therapy.

Epidermal growth factor receptor (EGFR) is a cell surface molecule and member of the ErbB family of receptor tyrosine kinases. Its activation leads to proliferation, antiapoptosis, and metastatic spread, making inhibition of this pathway a compelling target. In recent years, an increasing number of clinical trials in the management of solid malignancies have become available indicating the clinical efficacy of anti-EGFR monoclonal antibodies and oral small molecule tyrosine kinase inhibitors (TKIs). This review addresses frequently used EGFR inhibitors, summarizes clinical efficacy data of these new therapeutic agents, and discusses their associated toxicity and management.

Epidermal growth factor receptor (EGFR) inhibitors are highly effective in treating non-small cell lung cancers (NSCLC) expressing activated EGFR, particularly those harboring EGFR mutations. However, most patients who benefit from EGFR inhibitors achieve only partial responses or stable disease, facilitating the emergence of resistance. Thus, progression-free survival advantages in responding patients are modest. Combination therapy, preferably using agents with synergistic activity, could both improve responses and reduce acquired resistance rates. We hypothesized that combining MEK inhibitors with EGFR inhibitors could result in such a benefit. The MAPK pathway lies downstream of EGFR and transduces both proliferative and survival signals in a variety of cancer types. Inhibitors of this pathway are currently in clinical trials, but little evidence exists supporting the use of these agents as monotherapy in EGFR-dependent non-small cell lung cancer. In this study, we find EGFR-dependent NSCLC cell lines are moderately sensitive to loss of ERK1/2 activity, either by small molecule inhibition or by siRNA knockdown. The consequence of inhibition is dependent upon the trophic content of the culture media, primarily anti-proliferative in serum-rich conditions and pro-apoptotic in serum-poor conditions. However, when ERK inhibition combined with EGFR inhibitors, cytotoxic synergy was observed for all EGFR-dependent cell lines tested in serum-containing media. Enhanced cytotoxicity is demonstrated in cell lines with and without EGFR mutations, including those harboring the T790M escape mutation. These findings support future clinical studies that combine EGFR- and MEK1/2-targeted agents to investigate whether improved outcomes can be achieved in clinically screened EGFR-dependent NSCLC.

Sleep deprivation effects on EGFR signaling in a zebrafish exposed to rotenone

Is There a Role for the Irreversible Epidermal Growth Factor Receptor Inhibitor EKB-569 in the Treatment of Cancer? A Mutation-Driven Question

Aberrant EGFR signaling is widespread in cancer, making the EGFR an important target for therapy. EGFR gene amplification and mutation are common in glioblastoma (GBM), but EGFR inhibition has not been effective in treating this tumor. Here, we propose that primary resistance to EGFR inhibition in glioma cells results from a rapid compensatory response to EGFR inhibition that mediates cell survival. We show that in glioma cells expressing either EGFR wild type or the mutant EGFRvIII, EGFR inhibition triggers a rapid adaptive response driven by increased TNF secretion that leads to activation of a TNF-JNK-Axl-ERK signaling axis. Inhibition of this adaptive axis at multiple nodes renders glioma cells with primary resistance sensitive to EGFR inhibition. Our findings provide a possible explanation for the multiple failures of anti-EGFR therapy in GBM and suggest a new approach to the treatment of EGFR expressing GBM using a combination of EGFR and TNF inhibition.

Review of epidermal growth factor receptor biology

<div>Abstract<p>Epidermal growth factor receptor (EGFR) inhibitors are increasingly used in combination with radiotherapy in the treatment of various EGFR-overexpressing cancers. However, little is known about the effects of cell cycle status on EGFR inhibitor-mediated radiosensitization. Using EGFR-overexpressing A431 and UMSCC-1 cells in culture, we found that radiation activated the EGFR and extracellular signal-regulated kinase pathways in quiescent cells, leading to progression of cells from G<sub>1</sub> to S, but this activation and progression did not occur in proliferating cells. Inhibition of this activation blocked S-phase progression and protected quiescent cells from radiation-induced death. To determine if these effects were caused by EGFR expression, we transfected Chinese hamster ovary (CHO) cells, which lack EGFR expression, with EGFR expression vector. EGFR expressed in CHO cells also became activated in quiescent cells but not in proliferating cells after irradiation. Moreover, quiescent cells expressing EGFR underwent increased radiation-induced clonogenic death compared with both proliferating CHO cells expressing EGFR and quiescent wild-type CHO cells. Our data show that radiation-induced enhancement of cell death in quiescent cells involves activation of the EGFR and extracellular signal-regulated kinase pathways. Furthermore, they suggest that EGFR inhibitors may protect quiescent tumor cells, whereas radiosensitization of proliferating cells may be caused by downstream effects such as cell cycle redistribution. These findings emphasize the need for careful scheduling of treatment with the combination of EGFR inhibitors and radiation and suggest that EGFR inhibitors might best be given after radiation in order to optimize clinical outcome. [Cancer Res 2009;69(12):5108–14]</p></div>

<div>Abstract<p>Epidermal growth factor receptor (EGFR) inhibitors are increasingly used in combination with radiotherapy in the treatment of various EGFR-overexpressing cancers. However, little is known about the effects of cell cycle status on EGFR inhibitor-mediated radiosensitization. Using EGFR-overexpressing A431 and UMSCC-1 cells in culture, we found that radiation activated the EGFR and extracellular signal-regulated kinase pathways in quiescent cells, leading to progression of cells from G<sub>1</sub> to S, but this activation and progression did not occur in proliferating cells. Inhibition of this activation blocked S-phase progression and protected quiescent cells from radiation-induced death. To determine if these effects were caused by EGFR expression, we transfected Chinese hamster ovary (CHO) cells, which lack EGFR expression, with EGFR expression vector. EGFR expressed in CHO cells also became activated in quiescent cells but not in proliferating cells after irradiation. Moreover, quiescent cells expressing EGFR underwent increased radiation-induced clonogenic death compared with both proliferating CHO cells expressing EGFR and quiescent wild-type CHO cells. Our data show that radiation-induced enhancement of cell death in quiescent cells involves activation of the EGFR and extracellular signal-regulated kinase pathways. Furthermore, they suggest that EGFR inhibitors may protect quiescent tumor cells, whereas radiosensitization of proliferating cells may be caused by downstream effects such as cell cycle redistribution. These findings emphasize the need for careful scheduling of treatment with the combination of EGFR inhibitors and radiation and suggest that EGFR inhibitors might best be given after radiation in order to optimize clinical outcome. [Cancer Res 2009;69(12):5108–14]</p></div>