Epidermal Growth Factor Receptor Blockade Research Articles

EGFR Inhibition Fails to Suppress Vascular Proliferation and Tumor Growth in a Ewing's Sarcoma Model

Expression of epidermal growth factor receptor (EGFR), a potent regulator of cellular homeostasis, is associated with aggressive tumor behavior. The mechanism by which EGFR inhibition functions is unclear, with controversial results demonstrating an effect on the tumor cells, endothelial cells, or pericytes. EGFR activation has been linked to the expression of vascular endothelial growth factor (VEGF), a known mitogen of angiogenesis, but the relationship between these factors and their effect on tumor vessel development is vague. We hypothesized that using an EGFR inhibitor on a human Ewing's sarcoma model would inhibit tumor growth by suppressing vessel proliferation. A cell proliferation assay was performed on the Ewing's sarcoma (SK-NEP-1) cell line. Tumor cells were implanted intrarenally in athymic mice. Animals received daily gavage with vehicle or gefitinib 1 wk following implantation. Mice (n = 12/cohort) were euthanized 6 wk following implantation. Remaining mice were maintained without treatment for 2 wk. Vascular changes were assessed by angiography and immunohistochemically. EGFR and vascular endothelial growth factor (VEGF) expression were quantified using quantitative polymerase chain reaction (qPCR). Gefitinib suppressed in vitro cell growth with an IC(50) = 1.36 μM. Minimal tumor growth suppression was noted at 6 wk (6.01 ± 1.2 g in control versus 4.61 ± 0.9 g treated, P = 0.36). After cessation of gefitinib, tumor growth was increased in both groups (7.37 ± 1.62 g versus 6.77 ± 1.53 g, P = 0.79). Microvessel density was unchanged despite EGFR inhibition (161,000 ± 16,000 pixels versus 135,000 ± 18,000 pixels, P = 0.31). At 6 wk, the vascular maturity index was similar in both groups (3.63 ± 1.12 versus 4.09 ± 1.71, P = 0.83). A downward trend in EGFR expression (49% of control) and an upward trend in VEGF levels (50% of control) occurred in the treated group. EGFR expression was suppressed in cultured cells and xenograft tumors. Despite a cytotoxic effect on cell lines, gefitinib had little effect on tumor growth. No effects on the tumor vasculature were noted in the setting of EGFR suppression, suggesting that angiogenesis induced by SK-NEP-1 cells is refractory to EGFR inhibition. Interestingly, the resulting increase in VEGF expression following EGFR blockade, provides an alternative pro-angiogenic pathway promoting tumor survival.

A stable IgG-like bispecific antibody targeting the epidermal growth factor receptor and the type I insulin-like growth factor receptor demonstrates superior anti-tumor activity

The epidermal growth factor receptor (EGFR) and the type I insulin-like growth factor receptor (IGF-1R) are two cell surface receptor tyrosine kinases known to cooperate to promote tumor progression and drug resistance. Combined blockade of EGFR and IGF-1R has shown improved anti-tumor activity in preclinical models. Here, we report the characterization of a stable IgG-like bispecific antibody (BsAb) dual-targeting EGFR and IGF-1R that was developed for cancer therapy. The BsAb molecule (EI-04), constructed with a stability-engineered single chain variable fragment (scFv) against IGF-1R attached to the carboxyl-terminus of an IgG against EGFR, displays favorable biophysical properties for biopharmaceutical development. Biochemically, EI-04 bound to human EGFR and IGF-1R with sub nanomolar affinity, co-engaged the two receptors simultaneously, and blocked the binding of their respective ligands with similar potency compared to the parental monoclonal antibodies (mAbs). In tumor cells, EI-04 effectively inhibited EGFR and IGF-1R phosphorylation, and concurrently blocked downstream AKT and ERK activation, resulting in greater inhibition of tumor cell growth and cell cycle progression than the single mAbs. EI-04, likely due to its tetravalent bispecific format, exhibited high avidity binding to BxPC3 tumor cells co-expressing EGFR and IGF-1R, and consequently improved potency at inhibiting IGF-driven cell growth over the mAb combination. Importantly, EI-04 demonstrated enhanced in vivo anti-tumor efficacy over the parental mAbs in two xenograft models, and even over the mAb combination in the BxPC3 model. Our data support the clinical investigation of EI-04 as a superior cancer therapeutic in treating EGFR and IGF-1R pathway responsive tumors.

Abstract 1130: mPGES-1 drives the oncogenic potential of EGFR signaling

Abstract Prostaglandins, mostly PGE-2, have assumed an important role in cancer biology. Regarding of PGE-2 production, recent investigations have focused on PGE-2 synthases (mPGEs-1, mPGEs-2 and cPGEs), specifically on mPGEs-1, the only inducible enzyme among those so far identified in cells. Whereas cPGEs and mPGEs-2 are constitutively expressed at relatively low levels, mPGEs-1 is highly inducible by pro-inflammatory stimuli. mPGEs-1 upregulation has been detected in many epithelial tumors, and its silencing has been reported to reduce preneoplastic lesions. Despite the evidence linking mPGEs-1 and tumorigenesis, most studies investigating the inducible nature of the enzyme in cultured cells have been performed using a variety of inflammatory stimuli, while little is known about the behavior of the enzyme in tumor cells challenged with oncogenic stimuli. In this work we investigated mPGES-1 regulation in cultured epithelial tumor cells exposed to epidermal growth factor (EGF), an oncogene product which, through its receptor, EGF-receptor, is responsible for tumorigenisis in a wide array of solid tumors. We used three cell lines, representative of colon (HT-29), epidermoid (A431) and lung (A549) tumors, examining the expression of mPGEs-1 protein following EGF-receptor activation by EGF. We found that cells responded to EGF-receptor stimulation with a transient surge of the transcription factor Egr-1, its translocation from cytosol to necleus, an increase of mPGEs-1 mRNA and protein, as well as, an enhanced PGE-2 formation. These changes were suppressed by silencing Egr-1 and by EGF-receptor blockade or by inhibitors of the EGF-receptor-dependent mediators, such as MAP-kinase, ERK1/2. Moreover, cell activation through EGF-receptor induced a tumorigenic phenotype, detectable by clonogenic assay, which regressed when mPGEs-1 was silenced. We also explored the effect of inhibiting the EGF-receptor in A431 xenografts on mPGEs-1 expression and tumor growth, finding a parallel decline of both. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1130. doi:10.1158/1538-7445.AM2011-1130

Abstract 2488: Co-targeting EGFR and IGF-1R to sensitize or overcome induced resistance of head and neck cancer models to radiation

Abstract Purpose: Emerging data show crosstalk among receptor tyrosine kinases (RTK), e.g., epidermal growth factor receptor (EGFR) and insulin-like growth factor receptor (IGF-1R). Higher IGF-1R expression was associated with resistance to EGFR inhibitors and ionizing radiation (IR). We investigated the effects of cetuximab (EGFR antibody) and A12 (IGF-1R antibody) on the response of head and neck squamous cell carcinoma (HNSCC) to IR, escape mechanisms from EGFR blockade leading to radioresistance, and strategies to overcome it. Methods: Three HNSCC models (HN-5, FaDu, and UMSCC-1) expressing different levels of EGFR and IGF-1R were studied. The effects of cetuximab and A12 (from Imclone) on cell viability (MTS assay) and radiosensitivity (clonogenic survival assay) were determined. Various scheduling of drugs were examined. Alterations in target signaling were analyzed by Western blots. Results: Cetuximab inhibited viability of cells (14 to 53%) in a cell type dependent manner. The highest EGFR expressing HN-5 was the most responsive to cetuximab. A12 had no effect on cell viability but elicited a moderate radiosensitization of all three cell lines (enhancement factors, EFs, ranged from 1.11 to 1.67). Cetuximab, given 6 h before till 66 h after IR, significantly enhanced the radiosensitivity of HN-5 (EF, 2.55) and FaDu (EF, 1.46), but no effect on UMSCC-1. A 48 h exposure to cetuximab before IR, however, increased radioresistance of HN-5 and FaDu without affecting UMSCC-1. Continuing with cetuximab for 72 h after IR resulted in a net radiation sensitization in HN-5, partially reversed radioresistance in FaDu, and enhanced the radiosensitivity of UMSCC-1. Western blots revealed that cetuximab (48 h) upregulated IGF-1R in FaDu (2.28 fold) and UMSCC-1 (1.26 fold) but, not in HN-5; however, EGFR was upregulated in HN-5. IGF-1R inhibition had no effect on HN-5, reverted the radiation response partially in FaDu, and increased the net radiosensitivity of UMSCC-1. Compared to EGFR inhibition alone, co-targeting of both pathways did not yield a better effect on HN-5, reverted radiosensitivity to the baseline level in FaDu, but further increased UMSCC-1 radiosensitivity. Conclusion: This study showed that tumors responded to prolonged EGFR inhibition by upregulating other pro-survival RTK signaling, e.g. IGF-1R. In HN-5, EGFR was a main pro-survival signaling as EGFR inhibition yielded consistent sensitization that was not enhanced by IGF-1R blockade. UMSCC-1 seemed to rely on EGFR and IGF-1R signaling as dual inhibition yielded better sensitization than single pathway blockade. In FaDu, IGF-1R could become a major pro-survival signaling as it was associated with increased resistance that was only reverted by co-targeting IGF-1R. Taken together our data suggest that therapeutic benefit would result from combining cetuximab and A12 with IR in some HNSCC. Supported by P0-1 CA-06294 Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2488. doi:10.1158/1538-7445.AM2011-2488

Abstract 3269: VEGF inhibitor resistance is associated with stromal EGFR activation and normalized revascularization in an orthotopic model of lung adenocarcinoma

Abstract Therapeutic resistance to angiogenesis inhibitors represents a major obstacle in the treatment of non-small cell lung cancer (NSCLC). Previously, we reported that acquired resistance of subcutaneous murine models of NSCLC to the anti-vascular endothelial growth factor (VEGF) antibody bevacizumab (BV) was mediated by upregulation and activation of the epidermal growth factor receptor (EGFR) signaling pathway in stromal cells. Here, we investigated the effects of BV and dual VEGFR/EGFR inhibition, and the mechanisms of therapeutic resistance in H441 NSCLC orthotopic tumors. Short-term BV treatment (2 weeks) resulted in a significant tumor volume reduction compared with vehicle-treated tumors (p=0.026). For survival analysis, tumor-bearing mice were randomized to receive vehicle, erlotinib (E), BV, erlotinib + BV (E + B), or the VEGFR/EGFR inhibitor vandetanib (V), until moribund. All therapies significantly prolonged survival compared with vehicle (p<0.0001; E vs. vehicle p<0.05). Long-term BV administration improved survival compared with E (median survival 77 vs. 58 days, p=0.00015); however, both E + BV and V treatments (median survival 101 and 91 days, respectively) prolonged survival compared with E or BV alone (p=0.0001 E + BV vs. E or BV; p=0.0004 V vs. E; p=0.022 V vs. BV). Microvessel density (MVD) was strongly decreased in BV-sensitive tumors compared with 2 week vehicle treatment (p=0.0008); however, tumors resistant to BV or dual VEGFR/EGFR inhibition showed revascularization with increased MVD compared with BV-sensitive tumors (p=0.045). In erlotinib-resistant group MVD was significantly lower than in BV-resistant tumors (p=0.034). Levels of p-EGFR increased in BV-resistant tumors compared with controls (p=0.039) and co-localized with the stroma supporting large, normalized vessels. This signaling was suppressed in tumors resistant to VEGFR/EGFR targeting compared with both controls and BV-resistant tumors (p=0.0001 E + BV vs. vehicle; p=0.0008 E + BV vs. BV; p = 0.011 V vs. vehicle; p=0.009 V vs. BV), demonstrating persistent EGFR blockade with treatment. Pericyte coverage increased in BV-resistant tumors compared with controls and BV-sensitive tumors (p=0.003 BV vs. vehicle; p<0.0001 BV progression vs. BV 2 weeks). In tumors resistant to erlotinib or VEGFR/EGFR inhibition, pericyte coverage was reduced to levels comparable to controls (p=0.001 E vs. BV; p=0.054 E + BV vs. BV; p=0.007 V vs. BV). These findings demonstrate that in an orthotopic NSCLC model, resistance to BV is associated with tumor revascularization, featuring large, pericyte-covered vessels with increased perivascular EGFR activation. Dual VEGFR/EGFR blockade abrogates the BV-induced increase in pericyte coverage and delays the emergence of resistance. Stromal EGFR may contribute to VEGF inhibitor resistance through activation on perivascular cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3269. doi:10.1158/1538-7445.AM2011-3269

Phase I/II Trial of Cetuximab and Erlotinib in Patients with Lung Adenocarcinoma and Acquired Resistance to Erlotinib

In patients with epidermal growth factor receptor (EGFR) mutant lung adenocarcinoma, treatment with erlotinib or gefitinib is associated with a 75% radiographic response rate and progression-free survival of approximately 12 months. The most common mechanism of acquired resistance to erlotinib is development of a secondary mutation in EGFR, suggesting that these tumors continue to depend on EGFR signaling. We hypothesized that combined EGFR blockade would overcome acquired resistance to erlotinib in patients with lung adenocarcinoma. To evaluate the toxicity and efficacy of cetuximab and erlotinib in patients with acquired resistance to erlotinib, we conducted this phase I/II clinical trial. Patients with lung adenocarcinoma and clinically defined acquired resistance to erlotinib were treated with erlotinib 100 mg daily, along with cetuximab every 2 weeks in three escalating dose cohorts (250 mg/m(2), 375 mg/m(2), and 500 mg/m(2)). The recommended phase II dose was then evaluated in a two-stage trial, with a primary end point of objective response rate. A total of 19 patients were enrolled. The most common toxicities for the combination of cetuximab and erlotinib were rash, fatigue, and hypomagnesemia. The recommended phase II dose identified was cetuximab 500 mg/m(2) every 2 weeks and erlotinib 100 mg daily. At this dose and schedule, no radiographic responses were seen (0 of 13, 0%, 95% CI, 0-25). Combined EGFR inhibition, with cetuximab 500 mg/m(2) every 2 weeks and erlotinib 100 mg daily, had no significant activity in patients with acquired resistance to erlotinib.

Role of somatostatin receptor 1 and 5 on epidermal growth factor receptor mediated signaling

Epidermal growth factor (EGF) regulates normal and tumor cell proliferation via epidermal growth factor receptor (EGFR) phosphorylation, homo- or heterodimerization and activation of mitogen-activated protein kinases (MAPKs) and PI3K/AKT cell survival pathways. In contrast, SST via activation of five different receptor subtypes inhibits cell proliferation and has been potential target in tumor treatment. To gain further insight for the effect of SSTRs on EGFR activated signaling, we determine the role of SSTR1 and SSTR1/5 in human embryonic kidney (HEK) 293 cells. We here demonstrate that cells transfected with SSTR1 or SSTR1/5 negatively regulates EGF mediated effects attributed to the inhibition of EGFR phosphorylation, MAPKs as well as the cell survival signaling. Furthermore, SSTR effects were significantly enhanced in cells when EGFR was knock down using siRNA or treated with selective antagonist (AG1478). Most importantly, the presence of SSTR in addition to modulating signaling pathways leads to the dissociation of the constitutive and EGF induced heteromeric complex of EGFR/ErbB2. Furthermore, cells cotransfected with SSTR1/5 display pronounced effect of SST on the signaling and dissociation of the EGFR/ErbB2 heteromeric complex than the cells expressing SSTR1 alone. Taken together this study provides the first evidence that the presence of SSTR controls EGF mediated cell survival pathway via dissociation of ErbB heteromeric complex. We propose that the activation of SSTR and blockade of EGFR might serve novel therapeutic approach in inhibition of tumor proliferation.

Inhibiting epidermal growth factor receptor attenuates reactive astrogliosis and improves functional outcome after spinal cord injury in rats

As a physical barrier to regenerating axons, reactive astrogliosis is also a biochemical barrier which can secrete inhibitory molecules, including chondroitin sulfate proteoglycans (CSPGs) in the pathological mechanism of spinal cord injury (SCI). Thus, inhibition of astroglial proliferation and CSPG production might facilitate axonal regeneration after SCI. Recent studies have demonstrated that epidermal growth factor receptor (EGFR) activation triggers quiescent astrocytes into becoming reactive astrocytes and forming glial scar after CNS injury. In the present study, we investigated whether a specific EGFR inhibitor (AG1478) could attenuate the reactive astrogliosis and production of CSPGs, alleviate demyelination, and eventually enhance the functional recovery after SCI in rats. Our results showed that pEGFR immunoreactivity was up-regulated significantly post injury, mainly confined to astrocytes. Meanwhile, astrocytes near the injury site after SCI became activated obviously characterized by hypertrophic morphology and enhanced GFAP expression. However, administration of AG1478 remarkably reduced trauma induced-reactive astrogliosis and accumulation of CSPGs. Furthermore, the treatment with AG1478 also alleviated demyelination, increased expression of growth-associated proteins-43 (GAP-43) and improved hindlimb function after SCI. Therefore, the local blockade of EGFR in an injured area is beneficial to functional outcome by facilitating a more favorable environment for axonal regeneration in SCI rats.

Immuntherapie von Kopf-Hals-Karzinomen

The epidermal growth factor receptor (EGFR) is found to be overexpressed in nearly all squamous cell carcinomas of the head and neck (SCCHN). Monoclonal antibodies (mAbs) against EGFR are currently used to treat recurrent or metastatic disease; however, their mode of action is not fully understood. To investigate the immunological effects of anti-EGFR mAb, a three-dimensional spheroid model of EGFR-expressing SCCHN was generated and used to study the effect of anti-EGFR mAb on leukocyte migration towards tumors. The blockade of EGFR by anti-EGFR mAb in EGFR-overexpressing SCCHN cells led to differential expression (array) of several cytokines and chemokines, including the chemokine MCP-1/CCL-2. This was confirmed by quantitative PCR and ELISPOT analyses and shown to be functionally relevant by blocking experiments. These findings demonstrate that anti-EGFR mAb induces leukocyte infiltration to tumor spheroids by up-regulating chemokine expression. This novel mechanism for anti-EGFR mAb action may contribute to the anti-tumor effects of anti-EGFR mAb in vivo.

Kinase-driven pathways of EGFR in lung carcinomas: perspectives on targeting therapy

Despite remarkable advances in oncology medicine, the prognosis of lung cancer patients has not greatly improved over the past few decades. To overcome the current limit, new classes of agents that specifically target particular cascades have been developed. Gefitinib and erlotinib, which are tyrosine kinase inhibitors specific for the epidermal growth factor receptor (EGFR), have provided hope for better survival. The relationship between the sensitivity to gefitinib and the tumors' EGFR mutations have allowed the selective and accelerated use of these therapies. However, their efficacy is still limited, predominantly due to side effects and drug resistance. Further development of rational clinical strategies will require greater clarification of the key signaling factors downstream of EGFR which are potential targets for cancer therapies. In this review, we describe the various observed abnormalities in EGFR, the mechanisms of activation of several critical signaling cascades in lung cancer. Summarizing the data gleaned from preclinical, and clinicopathological aspects, we discuss the molecular mechanisms that may underlie a possible successful response to the blockade of EGFR and/or its downstream signaling.

484 Angiogenesis-related gene profiles with predictive value in advanced ovarian carcinoma (AOC)

Head and neck squamous cell carcinoma (HNSCC) is characterized by overexpression of the epidermal growth factor receptor (EGFR) where treatments targeting EGFR have met with limited clinical success. Elucidation of the key downstream-pathways that remain activated in the setting of EGFR blockade may reveal new therapeutic targets. The present study was undertaken to test the hypothesis that inhibition of the mammalian target of rapamycin (mTOR) complex would enhance the effects of EGFR blockade in HNSCC preclinical models. Treatment of HNSCC cell lines with the newly developed TORC1/TORC2 inhibitor OSI-027/ASP4876 resulted in dose-dependent inhibition of proliferation with abrogation of phosphorylation of known downstream targets including phospho-AKT (Ser473), phospho-4E-BP1, phospho-p70s6K, and phospho-PRAS40. Furthermore, combined treatment with OSI-027 and erlotinib resulted in enhanced biochemical effects and synergistic growth inhibition in vitro. Treatment of mice bearing HNSCC xenografts with a combination of the Food and Drug Administration (FDA)-approved EGFR inhibitor cetuximab and OSI-027 demonstrated a significant reduction of tumor volumes compared with either treatment alone. These findings suggest that TORC1/TORC2 inhibition in conjunction with EGFR blockade represents a plausible therapeutic strategy for HNSCC.

Phase II trial of cetuximab and erlotinib in patients with lung adenocarcinoma and acquired resistance to erlotinib.

7557 Background: The most common mechanism of acquired resistance to erlotinib (initial response followed by progressive disease) is development of a secondary mutation in the epidermal growth factor receptor (EGFR), suggesting that these tumors continue to depend upon EGFR signaling. We hypothesized that combined EGFR blockade would overcome acquired resistance to erlotinib in patients with lung adenocarcinoma. A prior phase I trial demonstrated the MTD of cetuximab given every 2 weeks in combination with erlotinib was 500 mg/m2. We conducted this phase II trial to determine the efficacy of cetuximab and erlotinib in patients with acquired resistance to erlotinib. Methods: Eligible patients had metastatic lung adenocarcinoma with either radiographic response (RECIST) to treatment with erlotinib or a documented EGFR mutation. All patients had previous treatment with erlotinib for more than 3 months, radiographic progression by RECIST during treatment with erlotinib, and continuous treatment with erlotinib for 1 month prior to initiating treatment. All patients met consensus definition of acquired resistance (Jackman JCO 28:357). Patients with grade 2 or greater skin toxicity on erlotinib monotherapy were not eligible. All patients received erlotinib 100 mg daily along with cetuximab 500 mg/m2 every two weeks. Results: Between December 2008 and July 2009, 13 patients were enrolled and treated. Median age was 60 (range 50-69), 9 women/4 men. The median time from beginning erlotinib was 19 months (range 5-72 months). Baseline EGFR mutations: exon 19 deletions (9), L858R (2), unknown (2). Acquired resistance T790M: present (7), absent (1), unknown (5). The median number of cycles received was 2 (range 1-7). Most common grade 3 and grade 4 toxicities were rash and hypomagnesemia. Response rate (CR+PR) was 0% (0/13, 95% CI 0-25%). Median progression-free and overall survival were 3 months and not reached (> 6 months). Conclusions: Combined EGFR inhibition with cetuximab 500 mg/m2 every 2 weeks and erlotinib 100 mg daily had no significant activity in patients with acquired resistance to erlotinib. Supported, in part, by Bristol-Myers Squibb and Imclone. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Bristol-Myers Squibb, Genentech, ImClone Systems

Cetuximab and circadian chronomodulated chemotherapy as salvage treatment for metastatic colorectal cancer (mCRC): safety, efficacy and improved secondary surgical resectability

Circadian rhythm disruption was linked to high serum levels of Transforming Growth Factor Receptor α, an Epidermal Growth Factor Receptor (EGFR) ligand and poor survival in patients with metastatic colorectal cancer (mCRC). We hypothesized that EGFR blockade with cetuximab would enhance the activity of chronotherapy as a result of improved circadian coordination. All the patients with mCRC referred to our unit for progression on prior chemotherapy over a 30-month-period received weekly cetuximab and fortnightly chronotherapy. Fifty-six patients were treated with a median of six courses of fluoropyrimidine-based chemotherapy and irinotecan (61%), oxaliplatin (25%) or both (14%) after a median of three prior regimens. We found no EFGR amplification by FISH in the tumor of 27 consecutive patients. Acneiform rash and diarrhea were the most common toxicities. Objective response rate was 32.1% and positively correlated with rash grade (p = 0.025). None of the responders had K-Ras mutation in their tumor. Median progression-free and overall survival were 4.6 and 13.7 months, respectively. Complete macroscopic resections of metastases in liver, lung or other abdominopelvic sites were performed following tumor downstaging by the treatment regimen in 11 patients (21%), 8 of whom being alive at 3 years. These figures are twice as high as those reported for first-line combination of cetuximab with conventional chemotherapy or for third line chronotherapy. The addition of cetuximab to chronotherapy allowed safe and effective therapeutic control of metastases, including their complete resection, despite previous failure of several treatment regimens.

Epidermal growth factor receptor targeted therapy of squamous cell carcinoma of the head and neck

Cumulative evidence implicates the epidermal growth factor receptor (EGFR) as an important therapeutic target in head and neck squamous cell carcinoma (HNSCC). The basis for the lack of correlation between EGFR expression in the HNSCC tumor and clinical responses to EGFR inhibitors is incompletely understood. Although a variety of mechanisms likely contribute to the effectiveness of EGFR blockade, this review focuses on the biologic implications of known EGFR variations and the role of the immune system in mediating clinical responses to EGFR inhibitors. A Medline review of articles published in the last 10 years (1999-present) on EGFR in HNSCC was performed in combination with preliminary data from our laboratories. Studies published to date suggest no association between the expression of EGFR on HNSCC tumors and clinical responses to EGFR inhibitors. Several mechanisms have been proposed to mediate clinical response to EGFR inhibitors in HNSCC. Cumulative results from our laboratories support the role of several mechanisms, including cellular immune activation and mutated EGFR variants, in contributing to the discrepancy between level of EGFR expression and clinical response to EGFR inhibitors. The efficacy of EGFR targeted therapies may be mediated, at least in part, by the immune system and the presence of the truncated EGFR variant, EGFRvIII, among other factors. Criteria to identify the subset of patients likely to be responsive to EGFR targeted therapies are needed.

Inhibitory effects of cytoplasmic-domain substituted epidermal growth factor receptor on growth, invasion and angiogenesis in human gastric cancer cells.

Epidermal growth factor receptor (EGFR) blockade is a promising therapeutic approach for gastric cancer overexpressing EGFR. EGFR, with a cytoplasmic domain substituted by enhanced green fluorescent protein (DNEGFR-EGFP), can act as a dominant negative mutant receptor to block the EGFR signaling pathway by competing with endogenous EGFR for ligands. The aim of this study was to investigate the effects of DNEGFR-EGFP on the growth, invasion and angiogenesis of human gastric cancer cells, and to elucidate the possible mechanisms behind them. Using multiple cellular and molecular approaches such as gene transfection, MTT, flow cytometry, Western blotting, ELISA, invasion and angiogenesis assays, we found that DNEGFR-EGFP led to G0/G1 arrest by down-regulating cyclin D1 and CDK2 and up-regulating p27, and repressed the invasion and angiogenesis of SGC-7901 cells by inhibiting them from secreting MMP-2, MMP-9 and VEGF. These results indicate that the EGFR blockade strategy (termed dominant negative strategy targeting EGFR) may serve as a promising therapy for the treatment of EGFR-overexpressed gastric cancer.

Inhibitory effects of cytoplasmic-domain substituted epidermal growth factor receptor on growth, invasion and angiogenesis in human gastric cancer cells

Epidermal growth factor receptor (EGFR) blockade is a promising therapeutic approach for gastric cancer overexpressing EGFR. EGFR, with a cytoplasmic domain substituted by enhanced green fluorescent protein (DNEGFR-EGFP), can act as a dominant negative mutant receptor to block the EGFR signaling pathway by competing with endogenous EGFR for ligands. The aim of this study was to investigate the effects of DNEGFR-EGFP on the growth, invasion and angiogenesis of human gastric cancer cells, and to elucidate the possible mechanisms behind them. Using multiple cellular and molecular approaches such as gene transfection, MTT, flow cytometry, Western blotting, ELISA, invasion and angiogenesis assays, we found that DNEGFR-EGFP led to G0/G1 arrest by down-regulating cyclin D1 and CDK2 and up-regulating p27, and repressed the invasion and angiogenesis of SGC-7901 cells by inhibiting them from secreting MMP-2, MMP-9 and VEGF. These results indicate that the EGFR blockade strategy (termed dominant negative strategy targeting EGFR) may serve as a promising therapy for the treatment of EGFR-overexpressed gastric cancer.

Treatment Intensification in the ‘High-risk’ Individual

AbstractThe high-risk individual merits treatment intensification. However, there are concerns with CERT. More supportive care is necessary as toxicity is higher. Treatment related death is a reality. Hence before we set out to prescribe concurrent chemoradiation we would need to stratify them according to the risk factors, their performance status and bear in mind the costs involved in intensive support during treatment.Apart from chemoradiation we need to explore emerging treatment strategies such as fractionated radiation therapy, and targeted therapies such as epidermal growth factor receptor blockade which might offer better if not similar results but with lesser toxicity.

RNAi Nanoparticles in The Service of Personalized Medicine

The understanding of cancer molecular origins and the different intracellular signaling pathways that are perturbed in the various types of malignancies have laid the foundation to realize why patients react diversely to therapy. For example, in colon cancer, an efficient treatment of EGF-receptor blockade with monoclonal antibody was found not to benefit patients with tumors positive for the K - ras mutation [1]. This slowly but steadily brought a shift from a ‘one size fits all’ therapy approach to a more person alized attitude, in which each patient is treated according to their tumor-specific genetic defects. To support this new approach, a substantial effort is invested in developing a new class of molecular diagnostic tools identifying patients’ tumor-personal gene-expression signatures, as well as mutation profiles. RNA interference (RNAi) is a is a ubiquitous, highly specific, endogenous mechanism of gene silencing that can be activated by incorporating small interfering (si)RNAs into the cell

Targeting Epidermal Growth Factor Receptor in Solid Tumors: Critical Evaluation of the Biological Importance of Therapeutic Monoclonal Antibodies

Numerous cellular pathways have a significant impact in the growth and metastatic potential of tumors. Essential element of such pathways is the epidermal growth factor receptor (EGFR), a member of the HER family of receptor tyrosine kinases. One of the most important issues in cancer, which attracted the attention of clinical oncologists, is the potential use of targeted therapies. EGFR signaling pathway is implicated in the control of cell survival, proliferation, metastasis and angiogenesis. EGFR is, therefore, an appealing target for molecular-targeted cancer therapy as it is expressed in a variety of solid tumors (colorectal, breast, head and neck, etc.). Receptor antagonists that target EGFR have already been of high interest for a number of years. Multiple therapeutic strategies have been developed to target EGFR, including monoclonal antibodies (mAbs), tyrosine kinase inhibitors (TKIs), ligand-toxin conjugates, and antisense oligonucleotides. In particular, mAbs block ligand from binding to the extracellular domain of the receptor. Two mAbs that block EGFR (erbB1), cetuximab and panitumumab, have been approved by FDA. Cetuximab is a chimeric IgG1 anti-EGFR monoclonal antibody, whereas panitumumab is a fully human IgG2 anti-EGFR monoclonal antibody. This review highlights the cellular effects of EGFR blockade by mAbs and their relationship to therapeutic efficacy and biological significance.

Evolving role of cetuximab in the treatment of colorectal cancer

In recent years, the monoclonal epidermal growth factor receptor (EGFR)-targeting antibody cetuximab was introduced into systemic therapy of colorectal cancer and gained an established role in the treatment of this disease. Cetuximab was shown to be active as a single agent in chemorefractory metastatic disease as well as in combination with varying chemotherapies. Recently, randomized trials demonstrated the activity of cetuximab combinations in the first-line setting of metastatic colorectal cancer. Interestingly, the activity of cetuximab was restricted to patients with KRAS wildtype tumors, as was seen with panitumumab, another EGFR antibody. While 60%-70% of tumors harbor KRAS wildtype genes, 30%-40% of tumors express oncogenic KRAS with mutations in codons 12 and 13 causing constitutive activation of signaling cascades downstream of EGFR and resistance to EGFR blockade. Since proof of KRAS wildtype status became a prerequisite for cetuximab treatment, KRAS testing is being established throughout the world. Future trials will address the question which part of the KRAS wildtype cohort will benefit from EGFR inhibition and how to identify those patients. Additionally, new strategies for treatment of KRAS mutated tumors are strongly needed. Recent developments and future strategies will be summarized.