Epidermal growth factor induces cell death in the absence of overexpressed epidermal growth factor receptor and ErbB2 in various human cancer cell lines

DNA damage alters EGFR signaling and reprograms cellular response via Mre-11

To combat the various DNA lesions and their harmful effects, cells have evolved different strategies, collectively referred as DNA damage response (DDR). The DDR largely relies on intranuclear protein networks, which sense DNA lesions, recruit DNA repair enzymes, and coordinates several aspects of the cellular response, including a temporary cell cycle arrest. In addition, external cues mediated by the surface EGF receptor (EGFR) through downstream signaling pathways contribute to the cellular DNA repair capacity. However, cell cycle progression driven by EGFR activation should be reconciled with cell cycle arrest necessary for effective DNA repair. Here, we show that in damaged cells, the expression of Mig-6 (mitogen-inducible gene 6), a known regulator of EGFR signaling, is reduced resulting in heightened EGFR phosphorylation and downstream signaling. These changes in Mig-6 expression and EGFR signaling do not occur in cells deficient of Mre-11, a component of the MRN complex, playing a central role in double-strand break (DSB) repair or when cells are treated with the MRN inhibitor, mirin. RNAseq and functional analysis reveal that DNA damage induces a shift in cell response to EGFR triggering that potentiates DDR-induced p53 pathway and cell cycle arrest. These data demonstrate that the cellular response to EGFR triggering is skewed by components of the DDR, thus providing a plausible explanation for the paradox of the known role played by a growth factor such as EGFR in the DNA damage repair.

Biased signaling downstream of epidermal growth factor receptor regulates proliferative versus apoptotic response to ligand

Inhibition of epidermal growth factor receptor (EGFR) signaling by small molecule kinase inhibitors and monoclonal antibodies has proven effective in the treatment of multiple cancers. In contrast, metastatic breast cancers (BC) derived from EGFR-expressing mammary tumors are inherently resistant to EGFR-targeted therapies. Mechanisms that contribute to this inherent resistance remain poorly defined. Here, we show that in contrast to primary tumors, ligand-mediated activation of EGFR in metastatic BC is dominated by STAT1 signaling. This change in downstream signaling leads to apoptosis and growth inhibition in response to epidermal growth factor (EGF) in metastatic BC cells. Mechanistically, these changes in downstream signaling result from an increase in the internalized pool of EGFR in metastatic cells, increasing physical access to the nuclear pool of STAT1. Along these lines, an EGFR mutant that is defective in endocytosis is unable to elicit STAT1 phosphorylation and apoptosis. Additionally, inhibition of endosomal signaling using an EGFR inhibitor linked to a nuclear localization signal specifically prevents EGF-induced STAT1 phosphorylation and cell death, without affecting EGFR:ERK1/2 signaling. Pharmacologic blockade of ERK1/2 signaling through the use of the allosteric MEK1/2 inhibitor, trametinib, dramatically biases downstream EGFR signaling toward a STAT1-dominated event, resulting in enhanced EGF-induced apoptosis in metastatic BC cells. Importantly, combined administration of trametinib and EGF also facilitated an apoptotic switch in EGFR-transformed primary tumor cells, but not normal mammary epithelial cells. These studies reveal a fundamental distinction for EGFR function in metastatic BC. Furthermore, the data demonstrate that pharmacological biasing of EGFR signaling toward STAT1 activation is capable of revealing the apoptotic function of this critical pathway.

Paradoxical induction of growth arrest and apoptosis by EGF via the up-regulation of PTEN by activating Redox factor-1/Egr-1 in human lung cancer cells

Epidermal growth factor (EGF) signaling promotes cell proliferation and survival in several types of cancer. Here, however, we showed that EGF inhibits proliferation and promotes programmed cell death in non-small cell lung cancer (NSCLC) cells. In A549 cells, EGF increased redox factor-1 (Ref-1) expression and the association of Ref-1 with zinc finger-containing transcriptional regulator (EGR1) via activation of p22phox, RAC1, and an NADPH oxidase subunit. EGF increased p22phox and RAC1 expression through activation of purinergic receptors (P2Y). Elevated Ref-1/EGR1 levels increased phosphatase and tensin homolog (PTEN) levels, leading to inhibition of the Akt pathway. EGF-induced PTEN upregulation increased apoptosis and autophagy-induced damage in A549 cells, whereas Ref-1 knockdown blocked EGF-induced PTEN upregulation in an NADPH oxidase p22phox subunit-independent manner. In addition, p22phox knockdown restored EGF-induced effects, implying that changes in P2Y activity caused by EGF, which activates NADPH oxidase via RAC1, influenced Ref-1-mediated redox regulation. Finally, EGF similarly attenuated cell proliferation and promoted autophagy and apoptosis in vivo in a xenograft model using A549 cells. These findings reveal that EGF-induced redox signaling is linked to Ref-1-induced death in NSCLC cells.

The paradoxical functions of EGFR during breast cancer progression

The epidermal growth factor receptor (EGFR) is one of the most well-studied signaling pathways in cancer progression. As a result, numerous therapeutics including small-molecule inhibitors and monoclonal antibodies have been developed to target this critical oncogenic driver. Several of these EGFR inhibitors (EGFRi) have been evaluated in metastatic breast cancer, as high-level EGFR expression in primary tumors correlates with the highly aggressive basal-like phenotype and predicts for poor patient prognosis. Surprisingly, these trials have been unanimously unsuccessful at improving patient outcomes. Numerous factors, such as lack of proper patient selection may have contributed to the failure of these trials. However, recent findings suggest that there are fundamental changes in EGFR signaling that take place during primary tumor invasion, dissemination and ultimate metastasis of breast cancer cells. Herein, we review the outcomes of EGFR-targeted clinical trials in breast cancer and explore our current understanding of EGFR signaling within primary mammary tumors and how these events are altered in the metastatic setting. Overall, we put forth the hypothesis that fundamental changes in EGFR signaling between primary and metastatic tumors, a process we term the 'EGFR paradox,' contribute to the clinically observed inherent resistance to EGFRi. Furthermore, this hypothesis introduces the possibility of utilizing EGFR agonism as a potential therapeutic approach for the treatment of metastatic breast cancer.

Tumor Growth Suppression and Enhanced Radioresponse by an Exogenous Epidermal Growth Factor in Mouse Xenograft Models with A431 Cells

Purpose

The purpose of this study was to evaluate whether an exogenous epidermal growth factor (EGF) could induce anti-tumor and radiosensitizing effects in vivo.

Materials and Methods

BALB/c-nu mice that were inoculated with A431 (human squamous cell carcinoma) cells in the right hind legs were divided into five groups: I (no treatment), II (EGF for 6 days), III (EGF for 20 days), IV (radiotherapy [RT]), and V (RT plus concomitant EGF). EGF was administered intraperitoneally (5 mg/kg) once a day and the RT dose was 30 Gy in six fractions. Hematoxylin and eosin (H&E) stained sections of tumor, liver, lung, and kidney tissues were investigated. Additionally, tumors were subjected to immunohistochemistry staining with caspase-3.

Results

EGF for 6 days decreased tumor volume, but it approached the level of the control group at the end of follow-up (p=0.550). The duration of tumor shrinkage was prolonged in group V while the slope of tumor re-growth phase was steeper in group IV (p=0.034). EGF for 20 days decreased tumor volume until the end of the observation period (p < 0.001). Immunohistochemistry revealed that mice in group V showed stronger intensity than those in group IV. There were no abnormal histological findings upon H&E staining of the normal organs.

Conclusion

EGF-induced anti-tumor effect was ascertained in the xenograft mouse models with A431 cells. Concomitant use of EGF has the potential role as a radiosensitizer in the design of fractionated irradiation.

The safety and efficacy of EGF-based cream for the prevention of radiotherapy-induced skin injury: results from a multicenter observational study

Purpose

This study was designed to evaluate the efficacy and safety of topically applied recombinant human epidermal growth factor (rhEGF) for the prevention of radiation-induced dermatitis in cancer patients.

Materials and Methods

From December 2010 to April 2012, a total of 1,172 cancer patients who received radiotherapy (RT) of more than 50 Gy were prospectively enrolled and treated with EGF-based cream. An acute skin reaction classified according to the Radiation Therapy Oncology Group 6-point rating scale was the primary end point and we also assessed the occurrence of edema, dry skin, or pruritus.

Results

The percentage of radiation dermatitis with maximum grade 0 and grade 1 was 19% and 58% at the time of 50 Gy, and it became 29% and 47% after completion of planned RT. This increment was observed only in breast cancer patients (from 18%/62% to 32%/49%). Adverse events related to the EGF-based cream developed in 49 patients (4%) with mild erythema the most common. Skin toxicity grade >2 was observed in 5% of the patients. Edema, dry skin, and pruritus grade ≥3 developed in 9%, 9%, and 1% of the patients, respectively.

Conclusion

Prophylactic use of an EGF-based cream is effective in preventing radiation dermatitis with tolerable toxicity. Further studies comparing EGF cream with other topical agents may be necessary.

Effect of recombinant human epidermal growth factor impregnated chitosan film on hemostasis and healing of blood vessels

Background

Bleeding can be a problem in wound debridement. In search for an effective hemostatic agent, we experimented with a chitosan film combined with the recombinant human epidermal growth factor (rh-EGF), hypothesizing that it would achieve effective hemostasis and simultaneously enhance arterial healing.

Methods

Forty-eight Sprague-Dawley rats were used, and 96 puncture wounds were made. The wounds were divided into the following four groups: treated with sterile gauze, treated with gelatin sponge, treated with chitosan, and treated with chitosan combined with rh-EGF. Immediate hemostasis was evaluated, and arterial healing was observed histologically.

Results

Groups B, C, and D showed a significant rate of immediate hemostasis as compared to group A (P<0.05), but there were no significant differences among groups B, C, and D. Histologically, only group D showed good continuity of the vessel wall after 1 week. It was the only group to show smooth muscle cell nuclei of the vessel wall.

Conclusions

We observed that chitosan has an effective hemostatic potential and the mix of rh-EGF and chitosan does not interfere with chitosan's hemostatic capabilities. We also identified enhanced healing of vessel walls when rh-EGF was added to chitosan. Further research based on these positive findings is needed to evaluate the potential use of this combination on difficult wounds like chronic diabetic ulcerations.

Highly efficient colorimetric detection of target cancer cells utilizing superior catalytic activity of graphene oxide-magnetic-platinum nanohybrids

Enzyme-linked immunosorbent assays (ELISAs) have most widely been applied in immunoassays for several decades. However, several unavoidable limitations (e.g., instability caused by structural unfolding) of natural enzymes have hindered their widespread applications. Here, we describe a new nanohybrid consisting of Fe₃O₄ magnetic nanoparticles (MNPs) and platinum nanoparticles (Pt NPs), simultaneously immobilized on the surface of graphene oxide (GO). By synergistically integrating highly catalytically active Pt NPs and MNPs on GO whose frameworks possess high substrate affinity, the nanohybrid is able to achieve up to a 30-fold higher maximal reaction velocity (V(max)) compared to that of free GO for the colorimetric reaction of the peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), and enable rapid detection of target cancer cells. Specifically, using this new assay system, clinically important breast cancer cells are detected in a 5 min time period at room temperature with high specificity and sensitivity. The remarkably high capability to catalyze oxidation reactions could allow the nanohybrid to replace conventional peroxidase-based immunoassay systems as part of new, rapid, robust and convenient assay systems which can be widely utilized for the identification of important target molecules.

Recombinant human epidermal growth factor (rhEGF) protects radiation-induced intestine injury in murine system

This study was to investigate whether rhEGF protects radiation induced intestine injury without compromising antitumor effect of radiation in murine system. A radiation induced intestinal injury model was established in mice by whole body irradiation. Using this model, 4 groups were set; control, rhEGF (100 µg/kg intraperitoneally), radiation (10 Gy), and a combination (rhEGF and radiation). The level of apoptosis and proliferation were analyzed by TUNEL assay and proliferation cell nuclear antigen (PCNA) immunohistochemical staining, respectively, as well as observation of survival and body weight change. A tumor growth delay assay was performed using murine syngeneic tumors; one radioresistant tumor, HCa-I and one radiosensitive tumor, MCa-K. In the radiation induced intestinal injury model, the 10 Gy group had significantly more weight loss with less number of crypt cells and higher apoptosis than the 8 Gy group. Using 10 Gy model, radioprotective effect of rhEGF was tested. Addition of rhEGF improved not only the body weight loss but also survival following radiation. It also induced suppression of apoptosis as well as increase of PCNA expression and recovery of villi. rhEGF did not enhance the tumor growth after radiation exposure in the tested tumors. These findings suggest that combination of exogenous rhEGF and radiation can be a new anticancer strategy by protecting radiation-induced intestinal injury without alleviating antitumor effect of radiation.

Therapeutic effects of recombinant human epidermal growth factor (rhEGF) in a murine model of concurrent chemo- and radiotherapy-induced oral mucositis

Concurrent chemotherapy with radiotherapy (CCRT) has been applied for the treatment of advanced stage of head and neck cancer patients. However CCRT is associated with several complications including mucositis, dermatitis, stomatitis, etc. This study was conducted to evaluate the therapeutic effect of systemically administrated recombinant human epidermal growth factor (rhEGF) in CCRT-induced oral mucositis in a mouse model. Oral mucositis was induced in male BALB/c mice through combination treatment with cisplatin (11 mg/kg, i.p.) and irradiation (17 Gy) of the head and neck area. rhEGF (1.0 mg/kg/day for consecutive 3 days) was administered systemically, and the therapeutic effect was determined by histological evaluation of the oral mucosa. To elucidate optimal dose of rhEGF on CCRT-induced mucositis, various concentrations (0.04-3 mg/kg) of rhEGF were injected for 3 days. Systemic rhEGF administration accelerated the recovery of body weight. Histologically, rhEGF-treated mice showed significantly increased epithelial cell layer thickness, basal cell number, and expression of Ki-67 compared to control mice. Most effective dose was 1 mg/kg among other doses tested. Systemic administration of 1 mg/kg of rhEGF reduces the severity of oral mucositis induced by CCRT in a mouse model, suggesting that rhEGF can be used for treating CCRT-induced mucositis during the cancer treatment.