Dose-dependent increases in circulating TGF-alpha and other EGFR ligands act as pharmacodynamic markers for optimal biological dosing of cetuximab and are tumor independent

Resistance to targeted therapy in metastatic colorectal cancer: Current status and new developments

Colorectal cancer (CRC) is one of the most lethal and common malignancies in the world. Chemotherapy has been the conventional treatment for metastatic CRC (mCRC) patients. However, the effects of chemotherapy have been unsatisfactory. With the advent of targeted therapy, the survival of patients with CRC have been prolonged. Over the past 20 years, targeted therapy for CRC has achieved substantial progress. However, targeted therapy has the same challenge of drug resistance as chemotherapy. Consequently, exploring the resistance mechanism and finding strategies to address the resistance to targeted therapy, along with searching for novel effective regimens, is a constant challenge in the mCRC treatment, and it is also a hot research topic. In this review, we focus on the current status on resistance to existing targeted therapies in mCRC and discuss future developments.

Resistance to anti-EGFR therapies in metastatic colorectal cancer: underlying mechanisms and reversal strategies

Cetuximab and panitumumab are monoclonal antibodies (mAbs) against epidermal growth factor receptor (EGFR) that are effective agents for metastatic colorectal cancer (mCRC). Cetuximab can prolong survival by 8.2 months in RAS wild-type (WT) mCRC patients. Unfortunately, resistance to targeted therapy impairs clinical use and efficiency. The mechanisms of resistance refer to intrinsic and extrinsic alterations of tumours. Multiple therapeutic strategies have been investigated extensively to overcome resistance to anti-EGFR mAbs. The intrinsic mechanisms include EGFR ligand overexpression, EGFR alteration, RAS/RAF/PI3K gene mutations, ERBB2/MET/IGF-1R activation, metabolic remodelling, microsatellite instability and autophagy. For intrinsic mechanisms, therapies mainly cover the following: new EGFR-targeted inhibitors, a combination of multitargeted inhibitors, and metabolic regulators. In addition, new cytotoxic drugs and small molecule compounds increase the efficiency of cetuximab. Extrinsic alterations mainly disrupt the tumour microenvironment, specifically immune cells, cancer-associated fibroblasts (CAFs) and angiogenesis. The directions include the modification or activation of immune cells and suppression of CAFs and anti-VEGFR agents. In this review, we focus on the mechanisms of resistance to anti-EGFR monoclonal antibodies (anti-EGFR mAbs) and discuss diverse approaches to reverse resistance to this therapy in hopes of identifying more mCRC treatment possibilities.

Fatty acid synthase mediates high glucose-induced EGFR activation in oral dysplastic keratinocytes

BACKGROUND

Recent studies point to the epidermal growth factor receptor (EGFR) as a critical mediator of type 2 diabetes mellitus (T2DM)-induced renal, cardiac, and ocular complications. T2DM is considered a systemic contributing factor in oral carcinogenesis. Similarly, increased EGFR gene copy number and protein expression strongly predict tumor progression. Yet, the impact of hyperglycemia on EGFR activity in oral potentially malignant disorders remains unclear. We recently reported that fatty acid synthase (FASN), a key de novo lipogenic enzyme, mediates EGFR activation in nicotine-treated oral dysplastic keratinocytes. While in non-malignant tissues FASN expression is extremely low, it is frequently upregulated in several cancers, including oral squamous cell carcinoma. The present study was carried out to investigate whether high glucose conditions trigger pro-oncogenic responses in oral dysplastic keratinocytes via FASN-mediated EGFR activation.

METHODS

Cell viability and migration of oral dysplastic keratinocytes were evaluated when exposed to normal (5 mM) or high (20 mM) glucose conditions in the presence of FASN and EGFR inhibitors. Western blotting was also performed to assess changes in FASN protein expression and EGFR activation.

RESULTS

Oral dysplastic keratinocytes exposed to high glucose led to EGFR activation in a FASN-dependent manner. Likewise, high glucose significantly enhanced cell viability and migration in a FASN/EGFR-mediated fashion. Notably, EGFR inhibition by the anti-EGFR monoclonal antibody cetuximab significantly reduced the proliferation of FASN-overexpressing oral dysplastic keratinocytes.

CONCLUSION

These novel findings suggest that FASN may act as a key targetable metabolic regulator of glucose-induced EGFR oncogenic signaling in oral potentially malignant disorders.

The Position of EGF Deprivation in the Management of Advanced Non-Small Cell Lung Cancer

Advanced non-small cell lung cancer (NSCLC) has faced a therapeutic revolution with the advent of tyrosine kinase inhibitors (TKIs) and immune checkpoints inhibitors (ICIs) approved for first and subsequent therapies. CIMAvax-EGF is a chemical conjugate between human-recombinant EGF and P64, a recombinant protein from Neisseria meningitides, which induces neutralizing antibodies against EGF. In the last 15 years, it has been extensively evaluated in advanced NSCLC patients. CIMAvax-EGF is safe, even after extended use, and able to keep EGF serum concentration below detectable levels. In a randomized phase III study, CIMAvax-EGF increased median overall survival of advanced NSCLC patients with at least stable disease after front-line chemotherapy. Patients bearing squamous-cell or adenocarcinomas and serum EGF concentration above 870 pg/ml had better survival compared to control patients treated with best supportive care as maintenance, confirming tumors’ sensitivity to the EGF depletion. This manuscript reviews the state-of-the-art NSCLC therapy and proposes the most promising scenarios for evaluating CIMAvax-EGF, particularly in combination with TKIs or ICIs. We hypothesize that the optimal combination of CIMAvax-EGF with established therapies can further contribute to transform advanced cancer into a manageable chronic disease, compatible with years of good quality of life.

Anti-EGF antibodies as surrogate biomarkers of clinical efficacy in stage IIIB/IV non-small-cell lung cancer patients treated with an optimized CIMAvax-EGF vaccination schedule

We previously reported that CIMAvax-EGF vaccine is safe, immunogenic and efficacious to treat advanced non-small-cell lung cancer (NSCLC) patients. A phase III trial was designed using an optimized immunization schedule. It included higher antigen dose and injections at multiple sites. Immune response and circulating biomarkers were studied in a subset of patients. EGF-specific antibody titers, IgG subclasses, peptide immunodominance and circulating biomarkers were assessed by ELISA. In vitro EGF-neutralization capacity of immune sera and EGF-IgG binding kinetics was evaluated by Western Blot and Surface Plasmon Resonance (SPR) technology, respectively. We show that CIMAvax-EGF elicited mainly IgG3/IgG4 antibodies at titers exceeding 1:4000 in 80% of vaccinated patients after 3 months of treatment. The EGF-specific humoral response was directed against the central region of the EGF molecule. For the first time, the kinetic constants of EGF-specific antibodies were measured evidencing affinity maturation of antibody repertoire up to month 12 of vaccination. Notably, the capacity of post-immune sera to inhibit EGFR phosphorylation significantly increased during the course of the immunization scheme and was related to clinical outcome (P = .013, log-rank test). Basal concentrations of EGF and TGFα in the serum were affected by EGF-based immunization. In conclusion, the CIMAvax-EGF vaccine induces an EGF-specific protective humoral response in a high percent of NSCLC vaccinated patients, the quantity and quality of which were associated with clinical benefit (clinical trial registration number: RPCEC00000161, http://registroclinico.sld.cu/).

Abbreviations

EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; Ab: antibody; AR: amphiregulin; NSCLC: non-small-cell lung cancer; rhEGF: recombinant human epidermal growth factor; BSC: best supportive care; TGFα: tumor growth factor alpha; IL-8: interleukin 8; MAb: monoclonal antibody; SPR: surface plasmon resonance

The pro-tumorigenic host response to cancer therapies

Resistance to cancer therapy remains a major challenge in clinical oncology. Although the initial treatment phase is often successful, eventual resistance, characterized by tumour relapse or spread, is discouraging. The majority of studies devoted to investigating the basis of resistance have focused on tumour-related changes that contribute to therapy resistance and tumour aggressiveness. However, over the last decade, the diverse roles of various host cells in promoting therapy resistance have become more appreciated. A growing body of evidence demonstrates that cancer therapy can induce host-mediated local and systemic responses, many of which shift the delicate balance within the tumour microenvironment, ultimately facilitating or supporting tumour progression. In this Review, recent advances in understanding how the host response to different cancer therapies may promote therapy resistance are discussed, with a focus on therapy-induced immunological, angiogenic and metastatic effects. Also summarized is the potential of evaluating the host response to cancer therapy in an era of precision medicine in oncology.

Colorectal cancer spheroid biobanks: multi-level approaches to drug sensitivity studies

Biobanking of molecularly characterized colorectal cancer stem cells (CSCs) generated from individual patients and growing as spheroids in defined serum-free media offer a fast, feasible, and multi-level approach for the screening of targeted therapies and drug resistance molecular studies. By combining in vitro and in vivo analyses of cetuximab efficacy with genetic data on an ongoing collection of stem cell-enriched spheroids, we describe the identification and preliminary characterization of microsatellite stable (MSS) CSCs that, despite the presence of the KRAS (G12D) mutation, display epidermal growth factor (EGF)-dependent growth and are strongly inhibited by anti-EGF-receptor (EGFR) treatment. In parallel, we detected an increased resistance to anti-EGFR therapy of microsatellite instable (MSI) CSC lines irrespective of KRAS mutational status. MSI CSC lines carried mutations in genes coding for proteins with a role in RAS and calcium signaling, highlighting the role of a genomically unstable context in determining anti-EGFR resistance. Altogether, these results argue for a multifactorial origin of anti-EGFR resistance that emerges as the effect of multiple events targeting direct and indirect regulators of the EGFR pathway. An improved understanding of key molecular determinants of sensitivity/resistance to EGFR inhibition will be instrumental to optimize the clinical efficacy of anti-EGFR agents, representing a further step towards personalized treatments.

A Molecularly Annotated Model of Patient-Derived Colon Cancer Stem-Like Cells to Assess Genetic and Nongenetic Mechanisms of Resistance to Anti-EGFR Therapy

Purpose: Patient-derived xenografts ("xenopatients") of colorectal cancer metastases have been essential to identify genetic determinants of resistance to the anti-EGFR antibody cetuximab and to explore new therapeutic strategies. From xenopatients, a genetically annotated collection of stem-like cultures ("xenospheres") was generated and characterized for response to targeted therapies.Experimental Design: Xenospheres underwent exome-sequencing analysis, gene expression profile, and in vitro targeted treatments to assess genetic, biological, and pharmacologic correspondence with xenopatients, and to investigate nongenetic biomarkers of therapeutic resistance. The outcome of EGFR family inhibition was tested in an NRG1-expressing in vivo model.Results: Xenospheres faithfully retained the genetic make-up of their matched xenopatients over in vitro and in vivo passages. Frequent and rare genetic lesions triggering primary resistance to cetuximab through constitutive activation of the RAS signaling pathway were conserved, as well as the vulnerability to their respective targeted treatments. Xenospheres lacking such alterations (RAS^wt) were highly sensitive to cetuximab, but were protected by ligands activating the EGFR family, mostly NRG1. Upon reconstitution of NRG1 expression, xenospheres displayed increased tumorigenic potential in vivo and generated tumors completely resistant to cetuximab, and sensitive only to comprehensive EGFR family inhibition.Conclusions: Xenospheres are a reliable model to identify both genetic and nongenetic mechanisms of response and resistance to targeted therapies in colorectal cancer. In the absence of RAS pathway mutations, NRG1 and other EGFR ligands can play a major role in conferring primary cetuximab resistance, indicating that comprehensive inhibition of the EGFR family is required to achieve a significant therapeutic response. Clin Cancer Res; 24(4); 807-20. ©2017 AACRSee related commentary by Napolitano and Ciardiello, p. 727.

Influence of the HER receptor ligand system on sensitivity to cetuximab and trastuzumab in gastric cancer cell lines

Purpose

Gastric cancer remains a major health concern, and improvement of the therapeutic options is crucial. Treatment with targeted therapeutics such as the EGFR-targeting antibody cetuximab or the HER2-targeting antibody trastuzumab is either ineffective or moderately effective in this disease, respectively. In this study, we analysed the involvement of the HER receptor ligands amphiregulin (AREG), epidermal growth factor (EGF), heparin-binding epidermal growth factor (HB-EGF) and transforming growth factor alpha (TGFα) in the responsiveness of gastric cancer cell lines to cetuximab and trastuzumab.

Methods

A panel of 11 gastric cancer cell lines was characterized for cetuximab and trastuzumab sensitivity, ligand secretion and expression and activation of the HER receptors using WST-1 cell proliferation assays, ELISAs and Western blot analyses. We further investigated the effects of an exogenous ligand application on the cetuximab and trastuzumab sensitivity.

Results

We found no correlation between TGFα secretion and the sensitivity to cetuximab or trastuzumab. For AREG, we confirmed previous results indicating that this ligand is a positive predictor of cetuximab sensitivity. Exogenous HB-EGF was effective in rescuing sensitive cell lines from inhibition of cell proliferation by both, cetuximab and trastuzumab.

Conclusions

Our data indicate that HB-EGF may be a useful marker for the prediction of trastuzumab sensitivity in gastric cancer.

Electronic supplementary material

The online version of this article (doi:10.1007/s00432-016-2308-z) contains supplementary material, which is available to authorized users.

Balancing efficacy of and host immune responses to cancer therapy: the yin and yang effects

Local and systemic treatments for cancer include surgery, radiation, chemotherapy, hormonal therapy, molecularly targeted therapies, antiangiogenic therapy, and immunotherapy. Many of these therapies can be curative in patients with early stage disease, but much less frequently is this the case when they are used to treat advanced-stage metastatic disease. In the latter setting, innate and/or acquired resistance are among the reasons for reduced responsiveness or nonresponsiveness to therapy, or for tumour relapse after an initial response. Most studies of resistance or reduced responsiveness focus on 'driver' genetic (or epigenetic) changes in the tumour-cell population. Several studies have highlighted the contribution of therapy-induced physiological changes in host tissues and cells that can reduce or even nullify the desired antitumour effects of therapy. These unwanted host effects can promote tumour-cell proliferation (repopulation) and even malignant aggressiveness. These effects occur as a result of systemic release of numerous cytokines, and mobilization of various host accessory cells, which can invade the treated tumour microenvironment. In short, the desired tumour-targeting effects of therapy (the 'yin') can be offset by a reactive host response (the 'yang'); proactively preventing or actively suppressing the latter represents a possible new approach to improving the efficacy of both local and systemic cancer therapies.

Cetuximab Inhibits T790M-Mediated Resistance to Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor in a Lung Adenocarcinoma Patient-Derived Xenograft Mouse Model

BACKGROUND

The epidermal growth factor receptor (EGFR) kinase domain T790M (amino acid substitution at position 790 in EGFR from threonine [T] to methionine [M]) mutation in non-small-cell lung cancer (NSCLC) results in resistance to EGFR tyrosine kinase inhibitors (TKIs). We used a patient-derived tumor xenograft (PDX) model containing an EGFR exon 19 deletion/T790M mutation to assess response to the EGFR-directed antibody cetuximab. Changes in the EGFR signaling pathway and ligand expression after treatment were investigated.

METHODS

PDX were randomized into control and treatment arms. Pharmacodynamic studies were performed at 2 and 24 hours and at 4 days after a single administration of cetuximab, erlotinib, or dacomitinib. Changes in the EGFR signaling pathway were assessed using Western blot analysis, and baseline mRNA expression of EGFR ligands using microarray analysis. Relative changes after treatment were assessed using quantitative polymerase chain reaction.

RESULTS

The xenograft showed a dramatic response to cetuximab. A complete reduction of total EGFR and phosphorylated EGFR occurred after cetuximab treatment. The PDX had increased baseline levels of heparin-binding epidermal growth factor-like growth factor (HB-EGF) compared with other PDX models with or without EGFR mutations. Amphiregulin was significantly reduced 2 hours after treatment with cetuximab. Compared with control mice, cetuximab- and EGFR-TKI-treated mice had significantly reduced HB-EGF gene expression at 2 hours, however, by day 4 the level of HB-EGF expression was higher. The effect of cetuximab compared with EGFR TKI on HB-EGF gene expression levels differed significantly at 2 and 24 hours but not at 4 days.

CONCLUSION

We showed a dramatic tumor response with cetuximab in an exon 19 deletion/T790M EGFR mutant lung adenocarcinoma PDX model, which suggests a role for the autocrine feedback loop in the mutant EGFR signaling pathway. Further investigation using cetuximab in NSCLC with T790M mutation is warranted.

Endocytosis of Ubiquitylation-Deficient EGFR Mutants via Clathrin-Coated Pits is Mediated by Ubiquitylation

Signaling by epidermal growth factor receptor (EGFR) is controlled by endocytosis. However, mechanisms of EGFR endocytosis remain poorly understood. Here, we found that the EGFR mutant lacking known ubiquitylation, acetylation and clathrin adaptor AP-2-binding sites (21KRΔAP2) was internalized at relatively high rates via the clathrin-dependent pathway in human duodenal adenocarcinoma HuTu-80 cells. RNA interference analysis revealed that this residual internalization is strongly inhibited by depletion of Grb2 and the E2 ubiquitin-conjugating enzyme UbcH5b/c, and partially affected by depletion of the E3 ubiquitin ligase Cbl and ubiquitin-binding adaptors, indicating that an ubiquitylation process is involved. Several new ubiquitin conjugation sites were identified by mass spectrometry in the 21KRΔAP2 mutant, suggesting that cryptic ubiquitylation may mediate endocytosis of this mutant. Total internal reflection fluorescence microscopy imaging of HuTu-80 cells transfected with labeled ubiquitin adaptor epsin1 demonstrated that the ubiquitylation-deficient EGFR mutant was endocytosed through a limited population of epsin-enriched clathrin-coated pits (CCPs), although with a prolonged CCP lifetime. Native EGFR was recruited with the same efficiency into CCPs containing either AP-2 or epsin1 that were tagged with fluorescent proteins by genome editing of MDA-MD-231 cells. We propose that two redundant mechanisms, ubiquitylation and interaction with AP-2, contribute to EGFR endocytosis via CCPs in a stochastic fashion.

Receptor occupancy assessment by flow cytometry as a pharmacodynamic biomarker in biopharmaceutical development

Receptor occupancy (RO) assays are designed to quantify the binding of therapeutics to their targets on the cell surface and are frequently used to generate pharmacodynamic (PD) biomarker data in nonclinical and clinical studies of biopharmaceuticals. When combined with the pharmacokinetic (PK) profile, RO data can establish PKPD relationships, which are crucial for informing dose decisions. RO is commonly measured by flow cytometry on fresh blood specimens and is subject to numerous technical and logistical challenges. To ensure that reliable and high quality results are generated from RO assays, careful assay design, key reagent characterization, data normalization/reporting, and thorough planning for implementation are of critical importance during development. In this article, the authors share their experiences and perspectives in these areas and discuss challenges and potential solutions when developing and implementing a flow cytometry‐based RO method in support of biopharmaceutical drug development. © 2015 The Authors Cytometry Part B: Clinical Cytometry Published by Wiley Periodicals, Inc.

Enhanced Targeting of the EGFR Network with MM-151, an Oligoclonal Anti-EGFR Antibody Therapeutic

Although EGFR is a validated therapeutic target across multiple cancer indications, the often modest clinical responses to current anti-EGFR agents suggest the need for improved therapeutics. Here, we demonstrate that signal amplification driven by high-affinity EGFR ligands limits the capacity of monoclonal anti-EGFR antibodies to block pathway signaling and cell proliferation and that these ligands are commonly coexpressed with low-affinity EGFR ligands in epithelial tumors. To develop an improved antibody therapeutic capable of overcoming high-affinity ligand-mediated signal amplification, we used a network biology approach comprised of signaling studies and computational modeling of receptor-antagonist interactions. Model simulations suggested that an oligoclonal antibody combination may overcome signal amplification within the EGFR:ERK pathway driven by all EGFR ligands. Based on this, we designed MM-151, a combination of three fully human IgG1 monoclonal antibodies that can simultaneously engage distinct, nonoverlapping epitopes on EGFR with subnanomolar affinities. In signaling studies, MM-151 antagonized high-affinity EGFR ligands more effectively than cetuximab, leading to an approximately 65-fold greater decrease in signal amplification to ERK. In cell viability studies, MM-151 demonstrated antiproliferative activity against high-affinity EGFR ligands, either singly or in combination, while cetuximab activity was largely abrogated under these conditions. We confirmed this finding both in vitro and in vivo in a cell line model of autocrine high-affinity ligand expression. Together, these preclinical studies provide rationale for the clinical study of MM-151 and suggest that high-affinity EGFR ligand expression may be a predictive response marker that distinguishes MM-151 from other anti-EGFR therapeutics.

Pharmacodynamic change in plasma angiogenic proteins: a dose-escalation phase 1 study of the multi-kinase inhibitor lenvatinib

Background

Lenvatinib (E7080), an oral multi-kinase inhibitor, has inhibitory action on tumor cell proliferation and tumor angiogenesis in preclinical models. We evaluated correlations between pharmacodynamic (PD) biomarkers with patient clinical outcomes in a lenvatinib phase 1 dose-escalation study.

Methods

Plasma angiogenic proteins were evaluated as potential PD biomarkers of response to lenvatinib in a dose-escalation phase 1 study. Lenvatinib was administered to 27 patients by twice-daily dosing in 3-week cycles; 2 weeks of treatment followed by 1 week of rest until discontinuation. Blood samples for plasma proteins were collected on days 1 (baseline), 8, and 15 of cycle 1, and days 1, 8, and 15 of cycle 2. Selected clinical outcomes, including tumor shrinkage and adverse events (AEs), were used for correlative analyses of pharmacokinetic parameters and PD biomarkers.

Results

Tumor shrinkage and changes in PD biomarkers (increased vascular endothelial growth factor [VEGF] and stromal cell-derived factor 1 alpha [SDF1α] levels and decreased soluble VEGF receptor 2 [sVEGFR2] levels) significantly correlated with increasing lenvatinib exposure. Observed changes in levels of VEGF, SDF1α, and sVEGFR2 were maintained on day 15 of cycle 1, but returned to baseline during the 1-week rest period, and similar changes were induced by reinstitution of treatment in cycle 2. The worst grades of hypertension, proteinuria, and fatigue were associated with changes in VEGF and HGF at day 8 of cycle 1. Maximum tumor shrinkage was correlated with increased SDF1α levels. Decreased sVEGFR2 level was also correlated with tumor shrinkage and frequency of hypertension, proteinuria, and fatigue. Tumor shrinkage significantly correlated with the worst grade of proteinuria, but not with hypertension or fatigue.

Conclusion

PD biomarker changes observed in plasma angiogenic proteins are correlated with lenvatinib-induced tumor shrinkage and AEs. Our findings warrant further assessment of plasma proteins associated with angiogenesis as potential biomarkers of lenvatinib activity.

Trial registration

ClinicalTrial.gov: NCT00280397 (January 20, 2006).

TGFα and amphiregulin paracrine network promotes resistance to EGFR blockade in colorectal cancer cells

PURPOSE

Targeted inhibition of EGFR with the mAbs cetuximab or panitumumab is a valuable treatment for RAS wild-type colorectal cancers. The efficacy of EGFR blockade is limited by the emergence of acquired resistance often attributed to secondary KRAS mutations. Remarkably, tumor biopsies from resistant patients show that only a fraction of the resilient cells carry KRAS mutations. We hypothesized that a paracrine cross-talk driven by the resistant subpopulation may provide in trans protection of surrounding sensitive cells.

EXPERIMENTAL DESIGN

Conditioned medium assays and three-dimensional cocultures were used to assess paracrine networks between cetuximab-sensitive and -resistant cells. Production of EGFR ligands by cells sensitive to cetuximab and panitumumab was measured. The ability of recombinant EGFR ligands to protect sensitive cells from cetuximab was assessed. Biochemical activation of the EGFR signaling pathway was measured by Western blotting.

RESULTS

Colorectal cancer cells sensitive to EGFR blockade can successfully grow despite cetuximab treatment when in the company of their resistant derivatives. Media conditioned by resistant cells protect sensitive parental cells from cetuximab. EGFR blockade triggers increased secretion of TGFα and amphiregulin. Increased secretion of ligands by resistant cells can sustain EGFR/ERK signaling in sensitive cells.

CONCLUSIONS

Colorectal cancer cells that develop resistance to cetuximab and panitumumab secrete TGFα and amphiregulin, which protect the surrounding cells from EGFR blockade. This paracrine protective mechanism might be therapeutically exploitable.

Increased TGF-α as a mechanism of acquired resistance to the anti-EGFR inhibitor cetuximab through EGFR-MET interaction and activation of MET signaling in colon cancer cells

PURPOSE

Although cetuximab, an anti-EGF receptor (EGFR) monoclonal antibody, is an effective treatment for patients with KRAS wild-type metastatic colorectal cancer (mCRC), its clinical use is limited by onset of resistance.

EXPERIMENTAL DESIGN

We characterized two colorectal cancer models to study the mechanisms of acquired resistance to cetuximab.

RESULTS

Following chronic treatment of nude mice bearing cetuximab-sensitive human GEO colon xenografts, cetuximab-resistant GEO (GEO-CR) cells were obtained. In GEO-CR cells, proliferation and survival signals were constitutively active despite EGFR inhibition by cetuximab treatment. Whole gene expression profiling identified a series of genes involved in the hepatocyte growth factor (HGF)-MET-dependent pathways, which were upregulated in GEO-CR cells. Furthermore, activated, phosphorylated MET was detected in GEO-CR cells. A second colorectal cancer cell line with acquired resistance to cetuximab was obtained (SW48-CR). Inhibition of MET expression by siRNA restored cetuximab sensitivity in GEO-CR and SW48-CR cells, whereas exogenous activation of MET by HGF stimulation in cetuximab-sensitive GEO and SW48 cells induced resistance to cetuximab. Treatment of GEO-CR and SW48-CR cells with PHA665752, a selective MET inhibitor, inhibited cell growth, proliferation, and survival signals and impaired cancer cell migration. Overexpression of TGF-α, a specific EGFR ligand, was involved in the acquisition of cetuximab resistance in GEO-CR and SW48-CR cells. In fact, TGF-α overexpression induced the EGFR-MET interaction, with subsequent MET phosphorylation and activation of MET downstream effectors in GEO-CR and SW48-CR cells.

CONCLUSIONS

These results suggest that overexpression of TGF-α through induction of EGFR-MET interaction contributes to cetuximab resistance in colorectal cancer cells. The combined inhibition of EGFR and MET receptor could represent a strategy for preventing and/or overcoming cetuximab resistance in patients with colorectal cancer.

EGFR ligands as pharmacodynamic biomarkers in metastatic colorectal cancer patients treated with cetuximab and irinotecan

This study was conducted to describe the modulation of plasma epidermal growth factor receptor (EGFR) ligands in EGFR-positive metastatic colorectal cancer (mCRC) patients during treatment with cetuximab and irinotecan and to explore the clinical implication of plasma levels' variations as potential biomarkers of benefit. Plasma amphiregulin (AR), epidermal growth factor (EGF), transforming growth factor-α, and heparin binding-EGF were assessed by ELISA in 45 chemorefractory mCRC patients, treated with cetuximab and irinotecan. Plasma levels were measured before and 1 h after the first administration of cetuximab, before and 1 h after the second administration, and before the third and the fifth cycles. KRAS and BRAF mutational status were determined. EGFR ligands' levels were differently modulated according to tumor KRAS and BRAF mutational status. In KRAS wild-type patients (n = 34), AR and EGF early increased and higher increases were significantly associated with worse clinical outcome. By adopting a specific cut-off value, patients with higher levels of AR 1 h after the first administration had significantly worse response rate, progression free survival, and overall survival. This hypothesis-generating study shows that EGFR ligands are significantly modulated by cetuximab plus irinotecan according to KRAS and BRAF mutational status, and they warrant further investigation as pharmacodynamic markers of resistance to anti-EGFRs.

A novel, high-sensitivity and drug-tolerant sandwich immunoassay for the quantitative measurement of circulating proteins

Background: Accurate measurement of a total protein target (free plus bound) is essential to optimize dose selection for monoclonal antibody drugs. Herein, we describe a novel sandwich immunoassay format in which the biotherapeutic antibody itself serves as the primary detection antibody. A signal is then generated through the addition of a labeled secondary antibody that recognizes the biotherapeutic antibody. The secondary antibody is conjugated with ruthenium to facilitate electrochemiluminescent analysis. Results: Data are presented from the analysis of two protein biomarkers having disparate size and structure; a 4.5 kDa peptide and a 60 kDa protein. In both cases, validated, highly specific assays were developed and shown to be tolerant to elevated levels of the therapeutic monoclonal antibody in question. Conclusion: Our novel format allows drug-tolerant measurement of soluble protein biomarkers targeted by monoclonal antibodies when only two independent epitopes for antibody binding are available and one is recognized by the therapeutic antibody.

Dual blockade of the EGFR and COX-2 pathways: a phase II trial of cetuximab and celecoxib in patients with chemotherapy refractory metastatic colorectal cancer

OBJECTIVES

The epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) pathways play key and often complementary roles in the pathogenesis of colorectal cancer (CRC). This study explores the clinical and biological effects of combined blockade of these pathways.

METHODS

Cetuximab-naive patients with refractory CRC were treated with cetuximab (400 mg/m loading dose followed by weekly cetuximab at 250 mg/m) and celecoxib (200 mg orally twice daily). Urinary PGE-M, a stable metabolite of PGE2 that correlates with in vivo COX-2 activity, and serum TGF-α, a ligand that binds to EGFR, were measured serially to assess the biological effect of COX-2 and EGFR blockade.

RESULTS

Seventeen patients accrued in this study. Of the 13 patients evaluable for response, 2 (15.4%) had confirmed partial responses, 4 (30.8%) had stable disease, and 7 (53.8%) had progressive disease. The median progression-free survival for all evaluable patients was 55 days (95% confidence interval, 45-112; range, 10-295 d). This study was terminated early owing to lack of sufficient clinical activity. There were no statistically significant differences in serum TGF-α or urinary PGE-M between cycles in responders or nonresponders.

CONCLUSIONS

This regimen resulted in response rates similar to those published for cetuximab monotherapy in patients with recurrent CRC. Apart from a higher than expected rate of infusion reactions, no other unexpected toxicities were observed. No differences in serum TGF-α or urinary PGE-M between cycles were seen, suggesting that the appropriate targets may not have been hit.

Cetuximab after bevacizumab in metastatic colorectal cancer: is it the best sequence?

BACKGROUND

Chemotherapy combinations and addition of cetuximab or bevacizumab to chemotherapy have been shown to improve overall survival of metastatic colorectal cancer (CRC) patients. However, the efficacy of cetuximab when administered after bevacizumab failure is still unknown.

METHODS

Fifty-eight consecutive patients diagnosed with advanced colorectal cancer between treated with cetuximab following irinotecan failure were included in our analysis. A multivariate Cox model analysis was performed to estimate the effect of previous bevacizumab regimen on survival.

RESULTS

Thirteen (22.4%) were pre-treated with anti-VEGF agents. None of them responded to cetuximab, and this subgroup presented a significantly decreased disease-specific survival as compared to treatment-naïve patients (9.1 months vs. 4.9 months; p=0.026). This difference remained statistically significant in a multivariate Cox model after adjusting for age, sex, performance status (PS), and K-RAS status (RR=2.2; 95% CI: 1.1-4.5, p=0.03).

CONCLUSION

These study results suggest that a previous anti-VEGF therapy decrease cetuximab efficiency.

Phase I and pharmacokinetic study of dasatinib and cetuximab in patients with advanced solid malignancies

BACKGROUND

Combined inhibition of epidermal growth factor receptor (EGFR) and Src family kinases (SFK) may lead to improved therapeutic effects. We evaluated the combination of dasatinib, an inhibitor of SFK and other kinases, and cetuximab, an anti-EGFR monoclonal antibody.

PATIENTS AND METHODS

Patients with advanced solid malignancies received cetuximab intravenously on a standard weekly schedule and dasatinib orally, once daily at 3 dose levels: (1) 100 mg, (2) 150 mg, (3) 200 mg. Pharmacokinetic and pharmacodynamic studies of dasatinib were performed prior to starting cetuximab and following 14 days of treatment.

RESULTS

Twenty-five patients (3 dose level 1; 19 dose level 2; 3 dose level 3) were initially treated. Three patients developed dose-limiting toxicities: 1 at dose level 2 (headache) and 2 at dose level 3 (headache, nausea). Grade 3-4 toxicities in more than 2 patients included: dyspnea (4), vomiting (4), nausea (3), hypersensitivity reactions (3), headache (3) and anemia (3). Twenty-one patients developed headache (8 grade 1; 10 grade 2), which occurred after the loading of cetuximab and lasted 1-3 days. Six additional patients were treated with dasatinib starting 3 days after the loading dose of cetuximab; none developed headache after dasatinib. Dasatinib pharmacokinetics and a transient decrease in SFK PY416 levels in peripheral blood mononuclear cells were not altered by cetuximab. Patients with higher plasma TGF-alpha levels had worse progression-free survival.

CONCLUSIONS

Dasatinib 150 mg once daily plus weekly cetuximab is recommended for phase II studies. Early-onset headache was ameliorated by starting dasatinib after cetuximab.

PK-PD modeling of protein drugs: implications in assay development

Pharmacokinetic-pharmacodynamic (PK-PD) modeling is an integral part of the preclinical and clinical development of protein drugs. Bioanalytical data from appropriately selected and well-characterized PK and PD biomarker assays can be incorporated into mechanistic PK-PD models and allow a quantitative relationship between protein drug exposure, target modulation, and biochemical, physiological and pathophysiological effects to be established. The selection of PD biomarkers that assess target engagement and modulation in the extracellular milieu and downstream cellular effects can provide proof-of-mechanism and define the magnitude and duration of target modulation following drug administration. The PK-PD data can provide an important link between magnitude of target modulation and clinical efficacy and safety outcomes, and guide the selection of doses and dosing schedules for clinical trials. In this article, approaches to the selection and development of fit-for-purpose, PK and PD assays for protein drugs are reviewed, and the applications of the assay results in PK-PD models are discussed.

Plasma transforming growth factor alpha and amphiregulin protein levels in NCIC Clinical Trials Group BR.21

PURPOSE

To evaluate the prognostic and predictive significance of plasma levels of the epidermal growth factor receptor (EGFR) ligands, transforming growth factor α (TGF-α) and amphiregulin, in patients with non-small-cell lung cancer (NSCLC) enrolled in NCIC Clinical Trials Group BR.21 comparing erlotinib with placebo.

PATIENTS AND METHODS

TGF-α and amphiregulin were assessed retrospectively by enzyme-linked immunosorbent assay from available prospectively collected baseline plasma samples in 565 of 731 BR.21 patients. Cutoff points were determined for both amphiregulin (low, <10 pg/mL; high, ≥10 pg/mL) and TGF-α (low, ≤12 pg/mL; high, >12 pg/mL) using a graphical method. Cox regression models were used to correlate biomarker data and baseline characteristics with outcomes including overall (OS) and progression-free survival (PFS).

RESULTS

High TGF-α and amphiregulin were associated with poorer performance status (P=.06 and P<.0001, respectively) and no prior platinum therapy (P=.06 and P=.02, respectively). High amphiregulin was also associated with anemia (P=.001), increased lactate dehydrogenase (P=.03), ever-smokers (P=.04), and non-Asian ethnicity (P=.001). Patients on the placebo arm with high amphiregulin had poorer OS than patients with low amphiregulin (hazard ratio [HR]=1.88; 95% CI, 1.34 to 2.64; P=.0002), which remained significant in multivariate analysis. Amphiregulin levels did not predict for benefit from erlotinib (interaction P=.87). Conversely, TGF-α levels did not have prognostic significance, but high TGF-α predicted lack of benefit from erlotinib compared with low TGF-α (TGF-α low, OS HR=0.66; 95% CI, 0.54 to 0.81; P<.0001; high, OS HR=1.32; 95% CI, 0.73 to 2.39; P=.36; interaction P=.04).

CONCLUSION

High baseline amphiregulin is a poor prognostic factor, whereas high baseline TGF-α predicts for lack of benefit from erlotinib in advanced NSCLC.

Regulation of heparin-binding EGF-like growth factor by miR-212 and acquired cetuximab-resistance in head and neck squamous cell carcinoma

Background

We hypothesized that chronic inhibition of epidermal growth factor receptor (EGFR) by cetuximab, a monoclonal anti-EGFR antibody, induces up-regulation of its ligands resulting in resistance and that microRNAs (miRs) play an important role in the ligand regulation in head and neck squamous cell carcinoma (HNSCC).

Methodology/Principal Findings

Genome-wide changes in gene and miR expression were determined in cetuximab-sensitive cell line, SCC1, and its resistant derivative 1Cc8 using DNA microarrays and RT-PCR. The effects of differentially expressed EGFR ligands and miRs were examined by MTS, colony formation, ELISA, and western blot assays. Heparin-binding EGF-like growth factor (HB-EGF) and its regulator, miR-212, were differentially expressed with statistical significance when SCC1 and 1Cc8 were compared for gene and miR expression. Stimulation with HB-EGF induced cetuximab resistance in sensitive cell lines. Inhibition of HB-EGF and the addition of miR-212 mimic induced cetuximab sensitivity in resistant cell lines. MicroRNA-212 and HB-EGF expression were inversely correlated in an additional 33 HNSCC and keratinocyte cell lines. Six tumors and 46 plasma samples from HNSCC patients were examined for HB-EGF levels. HB-EGF plasma levels were lower in newly diagnosed HNSCC patients when compared to patients with recurrent disease.

Conclusions/Significance

Increased expression of HB-EGF due to down-regulation of miR-212 is a possible mechanism of cetuximab resistance. The combination of EGFR ligand inhibitors or miR modulators with cetuximab may improve the clinical outcome of cetuximab therapy in HNSCC.