anti-EGFR Monoclonal Cetuximab Research Articles

Novel acquisitions on the immunoprotective roles of the EGF receptor in the skin

The EGF receptor (EGFR) and its ligands represent one of the most powerful and complex signaling networks in higher vertebrates. This system exerts an unusually wide spectrum of diverse bioregulatory functions. Numerous indications have been collected in the past decades, essentially based on mouse models, that emphasize its central role in the development and homeostasis of the skin. In particular, the multiple phenotypes of mouse models with distinct dysregulations of the EGFR pathway indicate clearly that this system exerts a major impact on keratinocyte proliferation and differentiation and, eventually, on the process of wound healing, hair follicle morphogenesis and malignant transformation [1]. Notably, despite a long history of robust investigation into the diverse biological outcomes deriving from its possible dysfunctions in vivo in the mouse, a novel and, at least in part, unprecedented compendium of the role of EGFR in human skin is now emerging from the widespread use of EGFR inhibitors in the therapy of EGFR-dependent tumors. Currently, a humanized anti-EGFR monoclonal antibody (cetuximab), a fully human monoclonal antibody (panitumumab) and two smallmolecule EGFR tyrosine kinase inhibitors (gefitinib and erlotinib) are available for the treatment of four metastatic epithelial cancers: non-small-cell lung cancer, squamous cell carcinoma of the head and neck, colorectal cancer and pancreatic cancer [2]. In patients treated with these drugs, a common adverse effect is a cutaneous inflammatory rash, characterized by papular pustular or acneiform eruption, which can be severe enough to lead to treatment modification or cessation [3]. These skin lesions are frequently pruritic and mostly affect the face and the upper trunk, although they may affect areas such as the dorsal arms and lower legs, and respond to anti-inflammatory drugs. Data from a large number of clinical trials suggest that the presence and severity of this cutaneous toxic effect are the most important positive correlates and predictors of the efficacy of anti-EGFR therapy in terms of progression-free survival [2,3]. Nonetheless, there is a serious need for an improved understanding of this side

Potential value of PTEN in predicting cetuximab response in colorectal cancer: An exploratory study

BackgroundThe epidermal growth factor receptor (EGFR) is over-expressed in 70–75% of colorectal adenocarcinomas (CRC). The anti-EGFR monoclonal antibody cetuximab has been approved for the treatment of metastatic CRC, however tumor response to cetuximab has not been found to be associated with EGFR over-expression by immunohistochemistry (IHC). The aim of this study was to explore EGFR and the downstream effector phosphatase and tensin homologue deleted on chromosome 10 (PTEN) as potential predictors of response to cetuximab.MethodsCRC patients treated with cetuximab by the Hellenic Cooperative Oncology group, whose formalin-fixed paraffin-embedded tumor tissue was available, were included. Tissue was tested for EGFR and PTEN by IHC and fluorescence in situ hybridization (FISH).ResultsEighty-eight patients were identified and 72 were included based on the availability of tissue blocks with adequate material for analysis on them. All patients, except one, received cetuximab in combination with chemotherapy. Median follow-up was 53 months from diagnosis and 17 months from cetuximab initiation. At the time of the analysis 53% of the patients had died. Best response was complete response in one and partial response in 23 patients. In 16 patients disease stabilized. Lack of PTEN gene amplification was associated with more responses to cetuximab and longer time to progression (p = 0.042).ConclusionPTEN could be one of the molecular determinants of cetuximab response. Due to the heterogeneity of the population and the retrospective nature of the study, our results are hypothesis generating and should be approached with caution. Further prospective studies are needed to validate this finding.

Evaluation of tumor gene expression and K-Ras mutations in FFPE tumor tissue as predictors of response to cetuximab in metastatic colorectal cancer

3512 Background: The anti-EGFR monoclonal antibody cetuximab shows activity in a subset of patients with metastatic colorectal cancer (mCRC). This study was conducted to discover and validate markers that are found to be associated with disease control and improved progression-free survival (PFS) time in patients treated with cetuximab. Methods: Formalin-fixed paraffin-embedded primary tumors of 226 patients from three studies of cetuximab monotherapy in advanced mCRC were retrospectively assayed for K-Ras mutations and for expression of candidate genes. The expression of K-Ras sequences (7 mutations and 1 wild-type) and 102 candidate genes were measured by quantitative RT-PCR. Statistical associations of mutation and gene expression with disease control (CR+PR+SD) or PFS were determined. Results: 82 (36%) of the 226 analyzed samples had K-Ras mutations. Patients whose tumors did not have K- Ras mutations had a significantly higher disease control rate (60%) than those with K-Ras mutations (23%) (p<< 0.001). Among all 226 patients, quantitative expression of 40 genes was significantly associated with disease control (p<0.05) after adjusting for multiplicity. Among 144 patients without K-Ras mutation, 31 genes were significantly associated with disease control (p<0.05) after adjusting for multiplicity. Genes that were strongly associated with disease control in both analyses included genes encoding the EGFR ligands epiregulin (EREG) and amphiregulin (AREG). Based on these results, we have developed multi-gene predictors that incorporate EREG and AREG, which when used in conjunction with K-Ras mutation status increase the ability to predict who might benefit from cetuximab treatment over K-Ras mutation status alone. Conclusions: A multi-parameter marker test comprising of K-Ras mutation status in combination with the expression levels of a small number of genes could be developed further to select patients for cetuximab therapy. Applicability of this test to cetuximab combination therapy should be explored. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Bristol-Myers Squibb, Genomic Health, Inc., ImClone Systems, Inc. Bristol-Myers Squibb, Genomic Health, Inc., ImClone Systems, Inc.

Cetuximab as second-line therapy in patients with metastatic esophageal cancer: A phase II Southwest Oncology Group Study

4536 Background: Survival for patients (pts) with metastatic esophageal cancer is poor, with no established therapy for patients failing first-line treatment. Esophageal adenocarcinoma over-expresses the epidermal growth factor receptor (EGFR), providing the rationale for examining the use of the anti-EGFR monoclonal antibody cetuximab. Methods: This was a multicenter, open-label phase II study of single agent cetuximab in pts with metastatic esophageal adenocarcinoma who had failed one prior chemotherapy regimen for advanced disease. Prior (neo) adjuvant therapy was allowed, but prior treatment targeting the EGFR pathway was not. Adequate organ function and Zubrod performance status of 0–2 were required. Pts received cetuximab 400 mg/m2 IV on week one, and 250 mg/m2 IV weekly thereafter. Pts were evaluated for toxicity weekly and for response every 8 weeks. The primary endpoint was a six-month overall survival rate > 40%. Secondary endpoints included progression-free survival, response rate, and toxicity. Tumor tissue was collected for correlative studies. Results: 63 pts were registered, 8 were not eligible. 55 eligible pts (male=49, female=6), median age 61.2 years (range 30.7–88.5) were enrolled. Out of 55 eligible and evaluable pts, 20 survived > 6 months for a 6-month overall survival rate of 36% (95% CI: 24%, 50%). The median overall survival was 4 months (95% CI: 3.2, 5.9), and the median progression-free survival was 1.8 months (95% CI: 1.7, 1.9). There were 3 unconfirmed partial responses. Two pts experienced Grade 4 fatigue, and there was one treatment-related death due to pneumonitis. Four pts had Grade 3 rash, and three of them survived > 6 months. Conclusions: This trial did not meet the primary objective of 23 pts surviving beyond 6 months, and thus cetuximab alone cannot be recommended in the second-line treatment of metastatic esophageal cancer. However, the regimen was associated with a 36% 6-month survival rate, and it was well tolerated. Trials combining cetuximab with cytotoxic chemotherapy in metastatic esophageal cancer are reasonable, and several are in development. Correlative science data from S0415 will be available in June. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Bristol-Myers Squibb, ImClone

Phase II trial of cetuximab in patients (pts) with metastatic and/or locally advanced soft tissue and bone sarcomas

10537 Background: Cytotoxic therapy has resulted in limited improvement in outcomes of pts with advanced sarcoma. The epidermal growth factor receptor (EGFR) pathway plays a role in tumorigenicity and is expressed in many sarcoma subtypes. Blockade of EGFR in certain sarcoma cell lines has decreased cell growth and increased tumor apoptosis. Therefore, we conducted a phase II trial of the anti-EGFR monoclonal antibody cetuximab in EGFR positive(+) and negative sarcoma and report here results of the EGFR+ group. Methods: Pts ≥ 16 years old with advanced sarcoma who progressed on ≥ 1 prior therapy were eligible. Cetuximab was administered at 400mg/m2 on day 1 and 250mg/m2 during subsequent weekly infusions. A cycle was defined as 4 weeks of therapy with radiographic assessment every 2 cycles. The primary objective was 4-month progression-free survival (PFS) rate in EGFR+ pts. Using a Simon two-stage design and a 10 and 30% rate as the null and alternative hypothesis, 22 pts were to be accrued in the first stage, with an additional 11 pts if ≥ 3 pts met primary endpoint. EGFR+ was defined by immunohistochemistry (IHC) as 1+, 2+, or 3+. Secondary objectives included assessment of response rate and evaluation of molecular alterations in EGFR pathway by IHC and mutational analysis using PCR/direct sequencing. Results: 22 evaluable pts with EGFR+ sarcoma were enrolled. Subtypes included synovial (32%), liposarcoma (27%), malignant fibrous histiocytoma (18%), leiomyosarcoma (14%), myxofibrosarcoma (4%), and malignant peripheral nerve sheath (4%). The median number of prior therapies was 2; the median number of cycles was 2; the median PFS was 52 days (95% CI: 48 - 54). One patient was free of progression for over 4 months. No objective responses were seen. Two patients withdrew from study due to ileus and acute renal failure. MAP-K, PTEN, and phospho-EGFR staining revealed variable expression without discernible pattern. No EGFR mutations were detected in exons tested in available specimens. Conclusions: Cetuximab has minimal activity in advanced EGFR+ sarcoma, and further investigation as a single agent is not indicated. Cetuximab in combination with cytotoxic therapy or following definition of specific molecular abnormalities in sarcoma requires further study. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Bristol-Myers Squibb

Targeted therapy in head and neck cancer

In patients with squamous cell carcinoma of the head and neck (SCCHN), tumor recurrence, secondary tumors, and comorbidities contribute to therapy failure, and treatment approaches often are limited by their toxicity. With the incorporation of targeted therapies, the number of options available for patients with SCCHN is growing. The epidermal growth factor receptor (EGFR) is involved in the development and progression of SCCHN and is associated with a poor prognosis. The anti-EGFR monoclonal antibody (MoAb) cetuximab is the first targeted therapy to be developed for SCCHN. Recent data confirmed a survival advantage and enhanced locoregional control of SCCHN with cetuximab plus radiotherapy (RT) in patients with locally advanced (LA) SCCHN. Single-agent cetuximab conferred clinical benefits for patients with platinum-refractory metastatic disease, and a recent phase 3 trial demonstrated a survival benefit with cetuximab and standard platinum-based therapy in the front-line treatment of recurrent/metastatic disease. Cetuximab has a toxicity profile milder than that of cytoxic agents and does not exacerbate RT toxicity when it is used in combination. Small-molecule EGFR-tyrosine kinase inhibitors also have shown promise in combination with chemoradiotherapy or as single agents, although they are in earlier stages of developmental. Other targeted approaches (eg, antiangiogenics) are also under investigation. Ongoing clinical trials will further define targeted treatment roles in all stages of SCCHN.

Controversial evaluation of EGFR protein and gene status in predicting response to anti-EGFR monoclonal antibodies in metastatic colorectal cancer: a case report and review of the literature

Clinical studies showed that only 10% of patients with metastatic colorectal cancer (mCRC) respond to treatment with the anti-epidermal growth factor receptor (EGFR) monoclonal antibodies panitumumab or cetuximab, regardless of the line of treatment. The current tool used to select patients, i.e. immunohistochemistry (IHC) evaluation of EGFR expression by EGFR pharmDx™ Kit, is not reliable in predicting response. Retrospective analyses of factors such as increased EGFR gene copy number and KRAS and/or BRAF mutations showed that such molecular changes could affect clinical benefit from anti-EGFR monoclonal antibodies. We report here the case of a 66-year-old man with chemorefractory mCRC, considered not eligible to salvage treatment with the anti-EGFR monoclonal antibody cetuximab and irinotecan because the primary adenocarcinoma of the rectum was found not expressing EGFR protein by IHC. However, FISH analysis of EGFR gene copy number and evaluation of KRAS and/or BRAF specific mutations by gene sequencing showed characteristics associated with favourable clinical outcome to anti-EGFR therapy. Based on the EGFR protein expression by IHC in a liver metastasis, the patient was then treated with cetuximab plus irinotecan, obtaining symptoms improvement and a dramatic objective tumor response in all sites of disease, lasting 4.2 months. We also discuss literature findings about the role of different biological characteristics in predicting clinical benefit from anti-EGFR therapy in patients with mCRC.

Determinants of RASistance to Anti–Epidermal Growth Factor Receptor Agents

Determinants of <i>RAS</i>istance to Anti–Epidermal Growth Factor Receptor Agents

Dual Inhibition of the Epidermal Growth Factor Receptor with Cetuximab, an IgG1 Monoclonal Antibody, and Gefitinib, A Tyrosine Kinase Inhibitor, in Patients with Refractory Non-small Cell Lung Cancer (NSCLC): A Phase I Study

To determine the optimal doses of the antiepidermal growth factor receptor (anti-EGFR) monoclonal antibody cetuximab and the EGFR tyrosine kinase inhibitor gefitinib when administered as a combination for patients with advanced/metastatic non-small cell lung cancer (NSCLC) previously treated with platinum-based chemotherapy. Patients with advanced/metastatic NSCLC treated with prior platinum-based chemotherapy received escalating doses of weekly cetuximab (100, 200, and 250 mg/m(2), IV) and fixed doses of gefitinib (250 mg/d, PO) until disease progression or unacceptable toxicity. Available tumor samples were analyzed for EGFR expression, EGFR gene copy number and mutations, and K-RAS mutations. Thirteen patients were enrolled in three cohorts. Treatment was generally well-tolerated at all doses. One grade 3 headache, observed on the first treatment cycle was initially considered dose-limiting toxicity (DLT); this event was eventually determined to be caused by a brain metastasis, not toxicity. Three cases of grade 3/4 hypomagnesemia and 1 case of grade 3 skin rash occurred in the highest-dose cohort. Grade 1/2 infusion reactions occurred in three patients without requiring treatment discontinuation. Four patients (31%) achieved stable disease, no responses were observed. None of the patients had EGFR mutations or gene amplification in their tumor samples. Dual EGFR inhibition with cetuximab and gefitinib is feasible; the combination can be safely administered and may have modest activity in advanced/metastatic NSCLC. Cetuximab 250 mg/m(2) weekly IV and gefitinib 250 mg/d PO is the recommended phase II dose, although the potential for late-onset hypomagnesemia warrants close monitoring of patients receiving this combined dosage.

A Retrospective on the Inhibition of Epidermal Growth Factor Receptor as a Therapeutic Strategy for Patients with Relapsed Metastatic Colorectal Cancer: Impact on Treatment of Today's Patients

The epidermal growth factor receptor (EGFR) pathway is overexpressed in many colorectal cancers (CRCs) and is associated with a worse prognosis compared with tumors that do not express EGFR. The development of monoclonal antibodies against this receptor, including cetuximab and panitumumab, and small-molecule inhibitors against the tyrosine kinase protein has led to new therapeutic paradigms in the treatment of metastatic CRC (mCRC). The anti-EGFR monoclonal antibody cetuximab has been shown to reverse chemotherapy resistance in patients with irinotecanrefractory mCRC, to improve survival compared with best supportive care (BSC) alone, and to prolong progression free-survival (PFS) in the first-and second-line settings. Panitumumab prolongs PFS compared with BSC, and trials in the first-and second-line settings are ongoing. Clinical trials with tyrosine kinase inhibitors have yielded disappointing results. This article reviews the clinical trial evidence for treatment strategies based on EGFR inhibition in relapsed/refractory mCRC, mechanisms of resistance to EGFR agents, clinical uncertainties, and future directions.

Combined Antiangiogenesis and Antiepidermal Growth Factor Receptor Targeting in the Treatment of Cancer: Hold Back, We Are Not There Yet

This issue of the Journal of Clinical Oncology (JCO) contains the results of two randomized phase II studies evaluating the activity of combined targeted therapy directed at the vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR). In the first study, Bowel Oncology and Cetuximab Antibody (BOND)-2, 83 patients with metastatic colorectal carcinoma (CRC) refractory to irinotecan-based chemotherapy were randomly assigned to receive the combination of the anti-EGFR monoclonal antibody cetuximab, the anti-VEGF monoclonal antibody bevacizumab, and irinotecan (CBI) or cetuximab plus bevacizumab (CB). Both arms demonstrated promising activity compared with historical controls, and there was a suggestion that the addition of bevacizumab improved the antitumor activity of cetuximab either alone or in combination with irinotecan. In the second study, 104 patients with previously untreated renal cell carcinoma (RCC) received bevacizumab in combination with the EGFR tyrosine kinase inhibitor erlotinib or with placebo. In this study, the addition of erlotinib to bevacizumab was well tolerated, but did not provide additional clinical benefit compared with bevacizumab alone. In summary, the combination of the antiVEGF antibody bevacizumab with an anti-EGFR agent was positive in patients with CRC, whereas it did not provide any additional benefit to bevacizumab alone in patients with RCC. In this editorial, we review the potential reason(s) for these discordant results and explore the implications of these studies for future research and daily clinical practice. First, both studies were designed based on a strong rationale exploring combined antiangiogenesis and anti-EGFR approaches. Solid tumors are genetically complex, and with rare exceptions, it is unlikely that a given tumor will be entirely dependent on one abnormally activated kinase or signaling pathway for its malignant behavior. There is also a considerable level of compensatory cross talk among receptors within one signaling pathway, as well as cross talk among distinct signaling pathways regulating cell proliferation, trafficking, and survival. As with conventional chemotherapeutic agents, which are often most effective when administered as combination therapies, rationally developed combinations of molecularly targeted agents are likely to be more potent than singleagent therapies. In the case of the potential interactions between EGFR signaling and angiogenesis, several studies have shown that both EGFR monoclonal antibodies and tyrosine kinase inhibitors reduce VEGF levels and microvessel density in tumors that regress on EGFR blockade. Interestingly, tumor cells with acquired resistance to cetuximab exhibit increased expression and secretion of VEGF, and forced expression of VEGF in sensitive cancer cells renders them resistant to cetuximab in vivo. These data suggest that inhibition of EGFR-dependent tumor neoangiogenesis is central for the antitumor effect of EGFR inhibitors; in turn, enhanced angiogenesis may endow tumors with resistance to EGFR blockade. Therefore, it is not surprising that the combination of antiangiogenic and anti-EGFR agents has showed greater antitumor activity than when these agents are administered alone. However, even carefully characterized preclinical models have limitations. For example, renal carcinoma cell lines are sensitive to cetuximab in vitro, whereas a series of clinical trials in RCC with anti-EGFR agents uniformly have shown lack of activity in patients. In this regard, the findings from the study by Bukowski et al in this issue of JCO provide one more piece of evidence for the lack of activity of anti-EGFR agents in RCC, and also raises the question as to whether single-agent activity may be required for any anti-EGFR agent to be incorporated into a combined-therapy approach. Conversely, the interpretation of the BOND-2 study in patients with refractory CRC seems to be more complex. This study follows the same approach as the initial BOND study, in which a total of 329 patients with EGFR-expressing colorectal cancer refractory to irinotecan-based chemotherapy were randomly assigned to receive cetuximab or irinotecan plus cetuximab. The combination treatment was superior to cetuximab as a single agent, both in terms of response rate (23% v 11%; P .007) and median progression-free survival (PFS; 4.1 v 1.5 months; P .001). The trial was not powered to demonstrate any advantage in overall (OS) survival, and half of the patients receiving cetuximab as a single agent were switched to the combination treatment when progression of the disease was documented. Nevertheless, a better median OS was observed in those patients receiving the combination as first-line treatment (8.6 v 6.9 months). In the BOND-2 study, patients refractory to irinotecan-based chemotherapy were randomly assigned to receive CBI or CB. Although the study was closed to accrual before the completion of target size (150 patients) due to poor accrual after the commercialization of bevacizumab, the results of the study showed promising activity: the CBI arm had JOURNAL OF CLINICAL ONCOLOGY E D I T O R I A L VOLUME 25 NUMBER 29 OCTOBER 1

Predictive factors of response to targeted therapies: the example of colorectal cancer

EGF receptor (EGFR), the VEGF and its receptors represent currently the most promising therapeutic targets in colorectal cancer. Strategies of EGFR targeting have been numerous with mainly monoclonal antibodies specifically binding the extracellular domain of the EGFR and enzymatic inhibitors of the intracellular part of the receptors with tyrosine kinase activity. These two latter therapeutic tools have been under active clinical development. The clinical application currently the most successful is the association of the anti-EGFR monoclonal antibody cetuximab with irinotecan in metastatic colorectal cancer. Recent clinical data point on panitumumab as another good candidate. The therapeutic classes used to antagonize the EGFR were applied as well for VEGF targeting. Encouraging clinical results came from the association between an anti-VEGF antibody, bevacizumab, with 5FU-folinic acid combination. Reliable predictive tools are needed to apply these treatments for potentially sensitive tumors only. This review underlines the lack of clinically-validated tools so as to provide a firm answer to this crucial question.

Epidermal Growth Factor Receptor (EGFR) Ubiquitination as a Mechanism of Acquired Resistance Escaping Treatment by the Anti-EGFR Monoclonal Antibody Cetuximab

Cetuximab is an epidermal growth factor receptor (EGFR)-blocking antibody that has been approved for treatment of patients with metastatic colorectal cancer. In this study, we investigated biochemical changes in signaling pathways of a cetuximab-resistant subline of DiFi colorectal cancer cells (DiFi5) that was developed by exposing the parental sensitive cells to subeffective doses of cetuximab over an extended period of time. Compared with parental DiFi cells that express high levels of EGFR and in which cetuximab induces apoptosis, the cetuximab-resistant DiFi5 cells showed markedly lower protein levels of EGFR, an increased association of EGFR with Cbl, and an increased ubiquitination of EGFR. DiFi5 cells also had a markedly higher level of Src-Y416 phosphorylation both at baseline and on EGF stimulation. Although EGFR levels were low, DiFi5 cells responded to EGF stimulation with robust phosphorylation of EGFR on Y845 and strong phosphorylation of Akt and extracellular signal-regulated kinase, comparable to those of parental cells. Most importantly, inhibition of Src kinase activity with PP2 reversed the resistance of DiFi5 cells to cetuximab-induced apoptosis without affecting the levels of EGFR in the cells. Our results indicate that colorectal cancer cells may develop acquired resistance to cetuximab via altering EGFR levels through promotion of EGFR ubiquitination and degradation and using Src kinase-mediated cell signaling to bypass their dependency on EGFR for cell growth and survival.

Targeting epidermal growth factor receptor signaling in the treatment of head and neck cancer

In this review, key aspects of epidermal growth factor receptor (EGFR) biology and the fruitful translation of these fundamental findings into recent treatment advances in head and neck squamous cell cancer (HNSCC) are highlighted. In contrast to a number of contemporary reviews of the EGFR, many of which focus on colorectal and nonsmall cell lung cancer, this review discusses the EGFR as a validated therapeutic target in HNSCC. Recent data confirm a survival advantage for the addition of the anti-EGFR monoclonal antibody cetuximab to definitive radiation therapy in locoregionally advanced HNSCC patients, as well as palliative benefits for patients with incurable recurrent and metastatic HNSCC. Small-molecule EGFR tyrosine kinase inhibitors also show considerable promise in this disease, both alone and in combination with radiation and chemotherapy. Both classes of anti-EGFR agent are generally well tolerated, with side effects (notably skin rash) that are distinct from the toxicities of conventional chemotherapy. Ongoing clinical trials will more clearly define the role for EGFR inhibitors in all treatment phases of HNSCC.

Novel Toll-Like Receptor 9 Agonist Induces Epidermal Growth Factor Receptor (EGFR) Inhibition and Synergistic Antitumor Activity with EGFR Inhibitors

Immunostimulating Toll-like receptor 9 (TLR9) agonists cause antitumor activity interfering also with cancer proliferation and angiogenesis by mechanisms still incompletely understood. We hypothesized that modified TLR9 agonists could impair epidermal growth factor receptor (EGFR) signaling and, by this means, greatly enhance EGFR inhibitors effect, acting on both the receptor targeting and the immunologic arm. We used a novel second-generation, modified, immunomodulatory TLR9 agonist (IMO), alone and in combination with the anti-EGFR monoclonal antibody cetuximab or tyrosine kinase inhibitor gefitinib, on the growth of GEO and cetuximab-resistant derivatives GEO-CR colon cancer xenografts. We have also evaluated the expression of several proteins critical for cell proliferation, apoptosis, and angiogenesis, including EGFR, mitogen-activated protein kinase, Akt, bcl-2, cyclooxygenase-2, vascular endothelial growth factor, and nuclear factor-kappaB. IMO inhibited GEO growth and signaling by EGFR and the other proteins critical for cell proliferation and angiogenesis. IMO plus the anti-EGFR antibody cetuximab synergistically inhibited tumor growth, signaling proteins, and microvessel formation. EGFR signaling inhibition by IMO is relevant because IMO cooperated also with EGFR tyrosine kinase inhibitor gefitinib in GEO tumors, while it was inactive against GEO-CR xenografts. On the other hand, IMO boosted the non-EGFR-dependent cetuximab activity, causing a cooperative antitumor effect in GEO-CR cells. Finally, combination of IMO, cetuximab and chemotherapeutic irinotecan eradicated the tumors in 90% of mice. IMO interferes with EGFR-related signaling and angiogenesis and has a synergistic antitumor effect with EGFR inhibitors, especially with cetuximab, boosting both the EGFR dependent and independent activity of this agent. Moreover, this therapeutic strategy could be translated in patients affected by colorectal cancer.

Expression of the epidermal growth factor receptor (EGFR or HER1) and human epidermal growth factor receptor 2 (HER2) in a large scale metastatic colorectal cancer (mCRC) trial

3630 Background: EGFR is commonly expressed in CRC (72–82%) and is therefore a target for anticancer therapies, such as the anti-EGFR monoclonal antibody cetuximab (Erbitux). There appears to be no...

Gene copy number for epidermal growth factor receptor (EGFR) and clinical response to antiEGFR treatment in colorectal cancer: a cohort study

The antiepidermal growth factor receptor (antiEGFR) monoclonal antibodies cetuximab and panitumumab have good clinical activity in about 10% of patients with metastatic colorectal cancer that is resistant to chemotherapy. The molecular mechanisms underlying clinical response or resistance to these agents are unknown. Tumours from 31 patients with metastatic colorectal cancer who had either an objective response (n=10) or stable disease or progressive disease (n=21) after treatment with cetuximab or panitumumab were screened for genetic changes in EGFR or its immediate intracellular effectors. Specifically, we assessed the EGFR copy number and the mutation profile of the EGFR catalytic domain and of selected exons in KRAS, BRAF, and PIK3CA. Eight of nine of patients with objective responses who were assessable by fluorescence in-situ hybridisation (FISH) had an increased EGFR copy number. By contrast, one of 21 non-responders assessable by FISH had an increased EGFR copy number (p<0.0001 for responders vs non-responders, Fisher's exact test). The mutation status of the EGFR catalytic domain and its immediate downstream effectors PIK3CA, KRAS, and BRAF did not correlate with disease response. In colorectal-cancer cell lines, the concentration of cetuximab that completely inhibited proliferation of cells with amplified EGFR copy number did not affect proliferation of cells with unamplified EGFR. We propose that the response to antiEGFR treatment has a genetic basis and suggest that patients might be selected for treatment on the basis of EGFR copy number.

Epidermal Growth Factor Receptor Inhibitors in Colorectal Cancer: It's Time to Get Back on Target

A key signature of targeted cancer therapy is selectivity. This selectivity depends on identification of a target that is tightly associated with the malignant phenotype. Inhibition of the target must alter this phenotype and must not adversely affect normal tissues. An ability to measure the presence of the target is a requirement for clinical development, such that individuals with tumors that do not express the target are spared exposure to ineffective treatment. Inhibitors of the epidermal growth factor receptor (EGFR) illustrate some of the triumphs and pitfalls associated with the development of targeted cancer therapy. Murine epidermal growth factor was identified more than 40 years ago, and its human homolog and receptor were isolated 15 years later. 1-5 Subsequently, the receptor was shown to have intrinsic kinase activity. 5 During the 1980s and 1990s, several significant observations established EGFR as a potential therapeutic target. 6,7 First, studies demonstrated homology between EGFR and the proto-oncogene v-erbB. 8 Second, frequent expression of EGFR was found in a variety of epithelial malignancies, with expression conferring poor prognosis. Finally, inhibitory antibodies and small molecules were shown to block receptor phosphorylation, cellular proliferation, and xenograft growth. 9-12 Given the frequent expression of EGFR in colorectal cancer (approximately 70% to 75% by immunohistochemistry [IHC]), 13 this malignancy was identified as appropriate for the clinical development of EGFR inhibitors. Clinical activity has been demonstrated for the anti-EGFR monoclonal antibodies cetuximab 14-16 (a human-mouse chimera) and panitumumab 17 (a fully human antibody) in patients with metastatic colorectal cancer. Cetuximab is approved by the US Food and Drug Administration for use in patients with EGFRexpressing metastatic colorectal cancer. 18 Based on xenograft models that indicated potentiation of anti-EGFR monoclonal activity with cytotoxic chemotherapy, 11 the initial phase II trial of cetuximab in patients with metastatic colorectal cancer was a combination study of irinotecan plus cetuximab. 14 Subsequent clinical trials confirmed the hypothesis that irinotecan plus cetuximab in combination is superior to cetuximab monotherapy, with response rates of approximately 20%v 10%, respectively, in patients who previously showed resistance to irinotecan. 15,16 The most common toxicity associated with cetuximab is skin rash, and the presence and severity of rash have been consistently predictive of response and survival in patients with colorectal cancer. 14,16 This clinical observation has led to the exploration of skin as a surrogate pharmacodynamic marker of EGFR inhibition, and numerous studies have demonstrated the predicted downstream perturbations of EGFR signaling, such as phosphorylated EGFR, phosphorylated AKT, Ki67, and p27 in the skin of patients treated with antibody and small-molecule EGFR inhibitors. 19-21 Unfortunately, a clear association between signaling inhibition in skin and antitumor response has not been found.

Anti-EGFR monoclonal antibody cetuximab binds the EGFR variant III receptor and internalizes phosphorylated receptor on the cell surface

Anti-EGFR monoclonal antibody cetuximab binds the EGFR variant III receptor and internalizes phosphorylated receptor on the cell surface