Cetuximab shows activity in colorectal cancer patients with tumors that do not express the epidermal growth factor receptor by immunohistochemistry

Overcoming acquired resistance to cetuximab by dual targeting HER family receptors with antibody-based therapy

Background

Cetuximab, an anti-EGFR monoclonal antibody, is used to treat several cancers. However, many patients who initially respond to cetuximab acquire resistance. To examine mechanisms of acquired resistance, we developed a series of cetuximab-resistant (Ctx^R) clones derived from the cetuximab sensitive (Ctx^S) non-small cell lung cancer (NSCLC) cell line H226. Previous studies characterizing this model revealed that: 1) EGFR was robustly overexpressed in Ctx^R clones due to decreased EGFR ubiquitination and degradation and 2) Ctx^R clones expressed increased HER2 and HER3 activation resulting in constitutive activation of the PI3K/AKT signaling axis. These findings suggest that dual targeting HER family receptors would be highly beneficial in the Ctx^R setting.

Results

Since HER3 has been implicated in resistance to EGFR inhibitors, the efficacy of dually targeting both EGFR and HER3 in Ctx^R models was evaluated. First, EGFR and HER3 expression were knocked down with siRNAs. Compared to the Ctx^S parental cell line (HP), all Ctx^R clones exhibited robust decreases in cell proliferation upon dual knockdown. Analysis of Ctx^R clones indicated that neuregulin-1 was highly overexpressed compared to HP cells. Incubation of HP cells with neuregulin-1 rendered them resistant to cetuximab. Next, dual treatment of Ctx^R clones with cetuximab and the HER3 neutralizing monoclonal antibody (mAb) U3-1287 led to potent anti-proliferative effects. Blockade of EGFR with cetuximab resulted in inactivation of MAPK, while blockade of HER3 with U3-1287 resulted in the inactivation of AKT. Treatment with both mAbs resulted in knockdown of both signaling pathways simultaneously. HER2 was also strongly inactivated upon dual mAb therapy, suggesting that this treatment regimen can diminish signaling from three HER family receptors. De novo Ctx^R H226 mouse xenografts were established to determine if dual therapy could overcome acquired resistance to cetuximab in vivo. Tumors that had acquired resistance to cetuximab were significantly growth delayed upon dual treatment of U3-1287 and cetuximab compared to those continued on cetuximab only. Combinatorial-treated xenograft tumors expressed decreased Ki67 and increased cleaved caspase-3 levels compared to tumors treated with either monotherapy.

Conclusions

These studies demonstrate that dually targeting HER family receptors with antibody-based therapies can overcome acquired resistance to cetuximab.

Biomarkers for predicting the efficacy of anti-epidermal growth factor receptor antibody in the treatment of colorectal cancer

Anti-epidermal growth factor receptor (EGFR) antibodies have been widely utilized as a standard treatment for metastatic colorectal cancer (CRC). Anti-EGFR antibodies bind competitively to EGFRs to inhibit receptor activation and subsequent signal transduction of the RAS/RAF/MEK pathway and PI3K/AKT pathway. By inhibiting EGFR-mediated signal transduction, anti-EGFR antibodies inhibit cell growth, invasion, metastasis and angiogenesis, and they induce apoptosis. The IgG1-type antibody cetuximab is also capable of inducing antibody-dependent cellular cytotoxicity. Several studies have shown that KRAS mutation is a useful biomarker for predicting the efficacy of anti-EGFR agents, and the major guidelines for the treatment of CRC recommend the use of anti-EGFR antibody only for the cancers with wild-type KRAS. Alterations of other genes, including BRAF, NRAS, PTEN and AKT, and EGFR expression/gene copy number have also been reported to be candidate biomarkers for predicting the efficacy of anti-EGFR agents. The predictive values of these biomarkers are still controversial and further investigations are required.

Molecular markers for colon diagnosis, prognosis and targeted therapy

Colorectal adenocarcinoma (CRC), the second leading cancer-related death in the United States, remains a global public health issue. Sporadic CRC is considered the result of sequential mucosal changes from normal colonic mucosa to adenocarcinoma. Efforts in understanding the molecular pathways leading to CRC tumorigenesis may lead to identifying novel, individually tailored therapeutic targets for patients. In this review, we focus on well-published prognostic and predictive markers in CRC and examine their role in clinical practice.

cMET in triple-negative breast cancer: is it a therapeutic target for this subset of breast cancer patients?

INTRODUCTION

The identification and validation of a targeted therapy for triple-negative breast cancer (TNBC) is currently one of the most urgent needs in breast cancer therapeutics. The cMET oncogene encodes a membrane-bound tyrosine kinase implicated in the formation and/or progression of several cancer types, including TNBC. Currently, inhibitors targeting cMET are undergoing clinical trials for a variety of cancers, including TNBC. These include anti-cMET and anti-hepatocyte growth factor (HGF) monoclonal antibodies and tyrosine kinase inhibitors.

AREAS COVERED

This article reviews the structure and mode of action of cMET, the role of cMET in cancer formation/development, with particular emphasis on its role in basal/TNBC and its potential as a therapeutic target for this subtype of breast cancer.

EXPERT OPINION

Due to cancer heterogeneity, it is unlikely that all TNBC patients will be responsive to anti-cMET drugs. Therefore, if cMET is to be used as a target for treatment, it will be important to identify predictive biomarkers to select, upfront, those patients likely to benefit. Potential predictive biomarkers for anti-cMET treatments in basal/TNBC include cMET, phospho-cMET, downstream signaling proteins or HGF. These putative predictive biomarkers should be evaluated in a large panel of basal/TNBC cell lines before incorporation into clinical trials involving anti-cMET drugs.

Mutations in 3'-long terminal repeat of HERV-W family in chromosome 7 upregulate syncytin-1 expression in urothelial cell carcinoma of the bladder through interacting with c-Myb

Human endogenous retrovirus (HERV) accounts for ∼8% of the human genome. Recent studies have reported that multiple HERV genes and long terminal repeats (LTRs) are involved in human tumorigenesis. Here we demonstrated that HERV-W env (syncytin-1) was overexpressed in 75.6% (62/82) of urothelial cell carcinoma (UCC) tissues of the bladder compared with only 6.1% (5/82) of matched tumor-adjacent tissues (P<0.001). Syncytin-1 overexpression increased proliferation and viability of immortalized human uroepithelial cells. Colony-formation experiments and in-vivo tumor xenografts suggested that syncytin-1 overexpression had oncogenic potential. Syncytin-1 3'-LTR mutations (142T>C and 277A>G) were present in 87.8% (72/82) of UCC tissues. Normal 3'-LTR was found in 12.2% (10/82) of UCC tissues compared with 95.1% (78/82) of matched tumor-adjacent tissues (P<0.001). Interestingly, 3'-LTR mutations were significantly associated with syncytin-1 overexpression. Luciferase assay and expression analysis revealed that 3'-LTR mutations, especially the 142T>C mutation, enhanced the syncytin-1 promoter activity and expression. In-silico analysis, electrophoretic mobility shift assays and chromatin immunoprecipitation assays demonstrated the binding of c-Myb to 3'-LTRs when the mutations occurred. This alternative interaction was found to be dependent on 142T>C mutation. C-Myb activated syncytin-1 promoter activity and expression by binding to mutant 3'-LTRs. Taken together, these data indicate that syncytin-1 overexpression may be an indicator of UCC risk. The 3'-LTR mutations may upregulate syncytin-1 expression, enabling it to participate in UCC tumorigenesis and development by interacting with c-Myb.

Oncologists' response to new data regarding the use of epidermal growth factor receptor inhibitors in colorectal cancer

PURPOSE

Although initially approved for metastatic colorectal cancer (mCRC) tumors with epidermal growth factor receptor (EGFR) overexpression, the use of anti-EGFR antibodies is now restricted to wild-type KRAS tumors. Little is known about prescribers' response to new clinical data, practice guidelines, and US Food and Drug Administration (FDA) label change with regard to the use of anti-EGFR antibodies in clinical practice.

METHODS

Commercially insured patients with mCRC who received second-line therapy between 2004 and 2010 were identified by dusing the LifeLink Health Plan Claims Database. We calculated the fraction of patients receiving anti-EGFR antibody in 2-month intervals. χ(2) tests were used to compare treatment rates at four time points: time 1: June 2008, ASCO presentation of clinical data; time 2: February 2009, ASCO guidelines publication; time 3: August 2009, FDA label change; time 4: April 2010 to 8 months after FDA label change.

RESULTS

Five thousand eighty-nine patients received second-line therapy; of these, 2,599 patients received an anti-EGFR antibody. Median age was 60 years (range, 20 to 97), with 57% male sex. The majority of patients (59.4%) received an anti-EGFR antibody at time 1, with significant decrease at each of the subsequent time points (time 2: 46.2% [P = .019]; time 3: 35.2% [P < .001]; Time 4: 16.2% [P < .001]). Multivariable logistic regression did not show any affect of age, sex, comorbidities, or region of the country on this pattern.

CONCLUSIONS

The use of anti-EGFR antibodies for mCRC decreased after the presentation of clinical trial data, ASCO guidelines publication, and FDA label change. These data suggest that oncologists respond rapidly to new evidence and professional guidelines, and readily incorporate predictive biomarkers into clinical practice.

Advances and new perspectives in the treatment of metastatic colon cancer

During the last decade we have witnessed an unprecedented outburst of new treatment approaches for the management of metastatic colon cancer. Anti-angiogenic drugs, epidermal growth factor receptor blockers and multi-kinase inhibitors have all resulted in small but consistent improvement in clinical outcomes. However, this progress has paradoxically leaded us into new challenges. In many cases the clinical development was done in parallel and the lack of head-to-head comparison evolved into circumstances where several valid new "standards of care" are available. Even though desirable in essence, the availability of many options as well as different possible combinations frequently leaves the busy clinician in the difficult situation of having to choose between one or the other, sometimes without solid evidence to support each decision. In addition, progress never stops and new agents are continuously tested. For these reason this review will try to summarize all the clinical trials that constitute the theoretical framework that support our daily practice but will also procure the reader with rational answers to common clinical dilemmas by critically appraising the current literature. Lastly, we will provide with a compilation of promising new agents that may soon become our next line of defense against this deadly disease.

Deficient HER3 expression in poorly-differentiated colorectal cancer cells enhances gefitinib sensitivity

Poorly-differentiated colorectal cancers (PD-CRC) show high metastatic potential and poor prognosis. However, molecular characteristics of PD-CRC remain unknown to date, particularly in molecular targeting therapy for patients with PD-CRC. In this study, we examined the expression of EGFR, HER2 and HER3 in PD-CRC by immunohistochemical analysis of archived clinical specimens of primary tumors and investigated the sensitivity of PD-CRC cell lines to gefitinib, a tyrosine kinase inhibitor for EGFR in vitro. We found that HER3 expression of PD-CRC among members of the HER family was significantly lower than that of well to moderately differentiated CRC (WMD-CRC) and 37% of the PD cases showed a EGFR+/HER2+/HER3- expression pattern. COLM-5 cells, a PD-CRC-derived cell line, which exhibits EGFR+/HER2+/HER3- expression pattern and recapitulates the typical histology of PD-CRC in xenografted tumors, showed high gefitinib sensitivity both in vitro and in vivo, compared with WMD-CRC cell line (COLM-2). Treatment with gefitinib resulted in the upregulation of p27Kip1 expression and induction of G1 cell cycle arrest, concomitantly associated with inactivation of PI3K/Akt signaling in COLM-5 cells and marked inhibition of xenografted tumors in nude mice, but not evident in COLM-2 cells. Treatment with sodium butyrate, an HDAC inhibitor that induces differentiation, upregulated the expression of HER3 associated with enhancement of the PI3K/Akt signaling, attenuated gefitinib-mediated p27Kip1 upregulation and reduced gefitinib sensitivity in COLM-5 cells in vitro. Furthermore, enforced expression of HER3 in COLM-5 cells resulted in significant resistance to gefitinib treatment both in vitro and in vivo. These findings suggest that deficient HER3 expression plays an important role in gefitinib sensitivity and that a malignant subset of PD with EGFR+/HER2+/HER3- phenotype is a potential candidate for a target of anti-EGFR molecular therapy such as gefitinib.

Central endoscopy reads in inflammatory bowel disease clinical trials: The role of the imaging core lab

Clinical trials in inflammatory bowel disease (IBD) are evolving at a rapid pace by employing central reading for endoscopic mucosal assessment in a field that was, historically, largely based on assessments by local physicians. This transition from local to central reading carries with it numerous technical, operational, and scientific challenges, many of which can be resolved by imaging core laboratories (ICLs), a concept that has a longer history in clinical trials in a number of diseases outside the realm of gastroenterology. For IBD trials, ICLs have the dual goals of providing objective, consistent assessments of endoscopic findings using central-reading paradigms whilst providing important expertise with regard to operational issues and regulatory expectations. This review focuses on current approaches to using ICLs for central endoscopic reading in IBD trials.

Final results from PRIME: randomized phase III study of panitumumab with FOLFOX4 for first-line treatment of metastatic colorectal cancer

BACKGROUND

The Panitumumab Randomized trial In combination with chemotherapy for Metastatic colorectal cancer to determine Efficacy (PRIME) demonstrated that panitumumab-FOLFOX4 significantly improved progression-free survival (PFS) versus FOLFOX4 as first-line treatment of wild-type (WT) KRAS metastatic colorectal cancer (mCRC), the primary end point of the study.

PATIENTS AND METHODS

Patients were randomized 1:1 to panitumumab 6.0 mg/kg every 2 weeks + FOLFOX4 (arm 1) or FOLFOX4 (arm 2). This prespecified final descriptive analysis of efficacy and safety was planned for 30 months after the last patient was enrolled.

RESULTS

A total of 1183 patients were randomized. Median PFS for WT KRAS mCRC was 10.0 months [95% confidence interval (CI) 9.3-11.4 months] for arm 1 and 8.6 months (95% CI 7.5-9.5 months) for arm 2; hazard ratio (HR) = 0.80; 95% CI 0.67-0.95; P = 0.01. Median overall survival (OS) for WT KRAS mCRC was 23.9 months (95% CI 20.3-27.7 months) for arm 1 and 19.7 months (95% CI 17.6-22.7 months) for arm 2; HR = 0.88; 95% CI 0.73-1.06; P = 0.17 (68% OS events). An exploratory analysis of updated survival (>80% OS events) was carried out which demonstrated improvement in OS; HR = 0.83; 95% CI 0.70-0.98; P = 0.03 for WT KRAS mCRC. The adverse event profile was consistent with the primary analysis.

CONCLUSIONS

In WT KRAS mCRC, PFS was improved, objective response was higher, and there was a trend toward improved OS with panitumumab-FOLFOX4, with significant improvement in OS observed in an updated analysis of survival in patients with WT KRAS mCRC treated with panitumumab + FOLFOX4 versus FOLFOX4 alone (P = 0.03). These data support a positive benefit-risk profile for panitumumab-FOLFOX4 for patients with previously untreated WT KRAS mCRC. KRAS testing is critical to select appropriate patients for treatment with panitumumab.

Preclinical comparison of near-infrared-labeled cetuximab and panitumumab for optical imaging of head and neck squamous cell carcinoma

PURPOSE

Though various targets have been proposed and evaluated, no agent has yet been investigated in a clinical setting for head and neck cancer. The present study aimed to compare two fluorescently labeled anti-epidermal growth factor receptor (EGFR) antibodies for detection of head and neck squamous cell carcinoma (HNSCC).

PROCEDURES

Antigen specificities and in vitro imaging of the fluorescently labeled anti-EGFR antibodies were performed. Next, immunodeficient mice (n = 22) bearing HNSCC (OSC-19 and SCC-1) tongue tumors received systemic injections of cetuximab-IRDye800CW, panitumumab-IRDye800CW, or IgG-IRDye800CW (a nonspecific control). Tumors were imaged and resected using two near-infrared imaging systems, SPY and Pearl. Fluorescent lymph nodes were also identified, and all resected tissues were sent for pathology.

RESULTS

Panitumumab-IRDye800CW and cetuximab-IRDye800CW had specific and high affinity binding for EGFR (K D = 0.12 and 0.31 nM, respectively). Panitumumab-IRDye800CW demonstrated a 2-fold increase in fluorescence intensity compared to cetuximab-IRDye800CW in vitro. In vivo, both fluorescently labeled antibodies produced higher tumor-to-background ratios compared to IgG-IRDye800CW. However, there was no significant difference between the two in either cell line or imaging modality (OSC-19: p = 0.08 SPY, p = 0.48 Pearl; SCC-1: p = 0.77 SPY, p = 0.59 Pearl; paired t tests).

CONCLUSIONS

There was no significant difference between the two fluorescently labeled anti-EGFR monoclonal antibodies in murine models of HNSCC. Both cetuximab and panitumumab can be considered suitable targeting agents for fluorescent intraoperative detection of HNSCC.

Resistance of oral squamous cell carcinoma cells to cetuximab is associated with EGFR insensitivity and enhanced stem cell-like potency

Cetuximab, a specific anti-epidermal growth factor receptor (EGFR) monoclonal antibody, is used in cancer treatment. Although development of resistance to cetuximab is well recognized, the underlying mechanisms remain unclear. In the present study, we characterized cetuximab-resistant oral squamous cell carcinoma (OSCC) cell lines. The human OSCC cell lines HSC3, HSC4 and SAS were used in the present study. Effects of inhibitors including cetuximab on growth in cells were assessed by MTT assays. Southern blotting and immunofluorescence analysis were performed to examine protein expression and localization. Sphere formation was used to characterize stem cell-like properties. Floating aggregation culture was used for anchorage-independent growth. Cetuximab inhibited proliferation of HSC3 and HSC4 cells, but not SAS cells. Proliferation of all three cell lines was inhibited by the EGFR/ErbB2/ErbB4 inhibitor II. The EGFR inhibitor AG1478 strongly inhibited HSC3 and HSC4 proliferation, but that of SAS cells only moderately. EGFR proteins were localized on cell surface and phosphorylated in all three cell lines. SAS cells could proliferate in serum-free monolayer culture and formed spheres from single cells in floating culture. HSC3 and HSC4 could not proliferate under serum-free culture conditions and could not form spheres. Growth of SAS spheres required serum, and was inhibited by both AG1478 and cetuximab. Thus, cetuximab-resistant SAS cells not only engaged in EGFR-independent growth but also exhibited stem cell-like properties. However, growth was EGFR-dependent in aggregation culture, and the SAS cell aggregates became cetuximab-sensitive. This suggests that cetuximab sensitivity is not only cell-type-dependent but is also affected by the growth microenvironment.

Predictive biomarkers to anti-EGF receptor inhibitors in the treatment of metastatic colorectal cancer

SUMMARY

The prognosis of patients harboring metastatic colorectal cancer (CRC) remains poor despite therapeutic improvements obtained in recent years thanks to new biologic agents. A resistance mechanism limits the effectiveness of current cancer therapies to treat metastatic CRC patients. The identification of mechanisms of drug resistance may highlight new biomarkers useful to predict the clinical outcome or the likely responsiveness to pharmacological treatment of those metastatic CRC patients who cannot benefit from current therapeutic regimen. Moreover, the recognition of panels of biomarkers may suggest new strategies to overcome resistance by rational drug design and combination treatment. This review discusses CRC biomarkers, focusing initially on the most recent findings about the known ones, and mostly about the novel protagonists of this complex scenario.

Combined assessment of epidermal [corrected] growth factor receptor dual color in situ hybridization and immunohistochemistry with downstream gene mutations in prediction of response to the anti-EGFR therapy for patients with metastatic colorectal cancer

BACKGROUND AND AIMS

Biomarkers associated with anti-EGFR antibodies therapy have been investigated in metastatic colorectal cancer (CRC). We conducted this study to evaluate the clinical utility of a combined assessment of EGFR status and genomic mutations of the EGFR downstream signal pathway in predicting the efficacy of anti-EGFR antibody treatment.

METHODS

We collected formalin-fixed paraffin-embedded tumor tissues and evaluated the EGFR status by immunohistochemistry (IHC), dual color in situ hybridization (DISH) and genomic analyses of KRAS, BRAF, PIK3CA and NRAS by direct sequencing.

RESULTS

A total of 129 patients were evaluated in our study. Among KRAS wild-type patients, EGFR DISH positivity was associated with a higher response rate than DISH negativity (56.3 vs. 21.1%, p = 0.011). A subgroup with EGFR DISH positivity plus IHC3+ and wild-type of EGFR downstream gene mutations achieved higher response rate and disease control rate. EGFR DISH positivity, KRAS codon 146 mutation and NRAS codon 61 mutation were prognostic factors in both progression-free survival and overall survival by multivariate analyses.

CONCLUSIONS

Combined assessment of DISH plus IHC and EGFR downstream gene mutations was useful to predict the response to anti-EGFR antibodies treatment in metastatic colorectal cancer patients in our study.

EGFR gene gain and PTEN protein expression are favorable prognostic factors in patients with KRAS wild-type metastatic colorectal cancer treated with cetuximab

INTRODUCTION

Cetuximab is a monoclonal epidermal growth factor receptor (EGFR)-targeting antibody, used in the treatment of colon cancer. KRAS mutation status is strongly predictive of cetuximab efficacy, but more predictive factors are needed for better patient selection. PTEN is a downstream inhibitor of the EGFR pathway and has been evaluated as a predictive factor of cetuximab efficacy in colorectal cancer.

PATIENTS AND METHODS

Formalin-fixed paraffin-embedded tumor tissue samples were collected from 226 patients with advanced or metastatic colorectal cancer that had been treated with cetuximab. Clinical information was collected retrospectively from the patients' medical records. After central evaluation, 147 cases with adequate material were eligible for further evaluation. EGFR and PTEN status was evaluated with immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Data were associated with cetuximab treatment outcome. Additional analysis was performed with previously published data on PIK3CA, BRAF and KRAS mutation status and EGFR ligand amphiregulin (AREG) and epiregulin intratumoral mRNA expression levels. PIK3CA mutation status and PTEN protein expression were also analyzed as a single complex parameter, to evaluate the predictive value of PI3K/PTEN axis dysfunction as one entity.

RESULTS

Analysis showed a borderline association of overall response rate (ORR) and time to progression (TTP) with EGFR protein overexpression by IHC (p = 0.059 and p = 0.057, respectively) and a positive association of EGFR gain by FISH (found in only five cases) with longer TTP (p = 0.026). No association was found between ORR or TTP and PTEN IHC or FISH status. Comparative analysis with previously published data showed that PTEN protein expression is associated with longer TTP in patients with wild-type (WT) KRAS (p = 0.036) and especially in the ones with elevated AREG levels (p = 0.046), as well as in patients with both KRAS and BRAF WT (p = 0.019). Patients with both PIK3CA WT and PTEN protein expression had significantly longer TTP (p = 0.010) versus all others, in the absence of BRAF and KRAS mutations, a finding which persisted in the KRAS WT/AREG high subgroup (p = 0.046).

CONCLUSIONS

In this cetuximab-treated colorectal cancer population, EGFR gain was associated with better outcome and PTEN protein expression with longer TTP in KRAS WT, KRAS WT/AREG high and KRAS/BRAF WT subpopulations. Cetuximab efficacy is greater with intact and activated EGFR signaling, without activating mutations of KRAS/BRAF and in the presence of preserved PTEN inhibitory activity upon the PI3K/AKT pathway. These results reflect a solid biological rationale and warrant further evaluation of the predictive role of PTEN in prospective studies.

Predictive and prognostic biomarkers with therapeutic targets in advanced colorectal cancer

Colorectal cancer (CRC) is one of the most common human malignant diseases and the second leading cause of cancer-related deaths worldwide. The treatment of advanced CRC has improved significantly in recent years. With the emergence of two targeted antibodies, cetuximab (Erbitux), an anti-epidermal growth factor receptor monoclonal antibody and bevacizumab (Avastin), a vascular endothelial growth factor monoclonal antibody, the treatment of metastatic CRC has entered the era of personalized therapy. Predictive and prognostic biomarkers have, and will continue to, facilitate the selection of suitable patients and the personalization of treatment for metastatic CRC (mCRC). In this review, we will focus primarily on the important progresses made in the personalized treatment of mCRC and discuss the potentially novel predictive and prognostic biomarkers for improved selection of patients for anti-cancer treatment in the future.

Epidermal growth factor receptor: pathway, therapies, and pipeline

BACKGROUND

The epidermal growth factor receptor (EGFR) pathway is important in tumor growth, survival, and metastasis and is now the target of several therapeutic agents.

OBJECTIVES

This paper seeks to review the EGFR pathway, the study and use of EGFR-directed agents in non-small-cell lung cancer (NSCLC) and colorectal cancer (CRC), and related new drug development.

METHODS

PubMed was searched for English-language articles by MeSH and title terms of EGFR published from 2006 to 2013, using the limits of clinical trials as well as reviews. Reference lists were assessed for relevant articles, and guidelines were searched. Clinicaltrials.gov and meeting abstracts were queried for investigational agents. Eligible papers included those concerning EGFR biology, NSCLC or CRC studies involving EGFR-directed agents, and/or investigational drugs targeting EGFR and/or associated pathways.

RESULTS

The activity of oral tyrosine kinase inhibitors (TKIs) against EGFR has improved survival in NSCLC, and these agents particularly effective in cancers with an EGFR mutation. Resistance to TKIs is most commonly related to a second, T790M, mutation, or to MET amplification, with newer agents directed against these mechanisms. Conversely, in CRC, TKIs have been ineffective, whereas monoclonal antibodies have improved survival. Both primary and secondary KRAS mutations in CRC abrogate mAb effectiveness. Several targets, including MET, BRAF, and PI3K, may serve useful in combination with anti-EGFR drugs.

CONCLUSIONS

Exploitation of EGFR-directed therapies has offered improvement in survival and quality of life in NSCLC and CRC. New therapies directed at EGFR may offer further improvements. However, resistance mechanisms suggest that combination therapies or multitargeted agents will be crucial in making significant future advances.

Gain of ALK gene copy number may predict lack of benefit from anti-EGFR treatment in patients with advanced colorectal cancer and RAS-RAF-PI3KCA wild-type status

Introduction

Although cetuximab and panitumumab show an increased efficacy for patients with KRAS-NRAS-BRAF and PI3KCA wild-type metastatic colorectal cancer, primary resistance occurs in a relevant subset of molecularly enriched populations.

Patients and Methods

We evaluated the outcome of 68 patients with advanced colorectal cancer and RAS, BRAF and PI3KCA status according to ALK gene status (disomic vs. gain of ALK gene copy number – defined as mean of 3 to 5 fusion signals in ≥10% of cells). All consecutive patients received cetuximab and irinotecan or panitumumab alone for chemorefractory disease.

Results

No ALK translocations or amplifications were detected. ALK gene copy number gain was found in 25 (37%) tumors. Response rate was significantly higher in patients with disomic ALK as compared to those with gain of gene copy number (70% vs. 32%; p = 0.0048). Similarly, progression-free survival was significantly different when comparing the two groups (6.7 vs. 5.3 months; p = 0.045). A trend was observed also for overall survival (18.5 vs. 15.6 months; p = 0.885).

Conclusion

Gain of ALK gene copy number might represent a negative prognostic factor in mCRC and may have a role in resistance to anti-EGFR therapy.

Comparison of KRAS mutation analysis of primary tumors and matched circulating cell-free DNA in plasmas of patients with colorectal cancer

Colorectal cancer (CRC) patients with KRAS mutations do not benefit from epidermal growth factor receptor (EGFR) targeted therapy. In clinical practice, identifying patients with KRAS mutations is critical prior to EGFR targeting therapy, and gene testing is generally performed using the DNA extracted from tumor tissue. The aim of this study was to compare the presence of KRAS mutations in circulating cell-free DNA (cfDNA) and primary tumor tissue using a peptide nucleic acid mediated polymerase chain reaction. We extracted and analyzed the DNA from plasmas and corresponding primary tumor samples from 52 patients with CRC. The results demonstrated that the detection rate of KRAS sequence variations was 50% (26 of 52) in plasma samples and 28.8% (15 of 52) in resected primary tumor tissue samples. The majority of KRAS mutations detected in tumors were also found in matched plasma specimens with an agreement rate of 78.8%. Eleven plasma cfDNA were found positive for KRAS mutation but not in their corresponding tissue. In conclusion, our results suggest that circulating cfDNA provides a better representation of the malignant disease as a whole and could be a reliable source of diagnostic DNA to replace the tumor tissue in a diagnostic setting.

Theranostic applications of antibodies in oncology

Targeted therapies, including antibodies, are becoming increasingly important in cancer therapy. Important limitations, however, are that not every patient benefits from a specific antibody therapy and that responses could be short-lived due to acquired resistance. In addition, targeted therapies are quite expensive and are not completely devoid of side-effects. This urges the need for accurate patient selection and response monitoring. An important step towards personalizing antibody treatment could be the implementation of theranostics. Antibody theranostics combine the diagnostic and therapeutic potential of an antibody, thereby selecting those patients who are most likely to benefit from antibody treatment. This review focuses on the clinical application of theranostic antibodies in oncology. It provides detailed information concerning the suitability of antibodies for theranostics, the different types of theranostic tests available and summarizes the efficacy of theranostic antibodies used in current clinical practice. Advanced theranostic applications, including radiolabeled antibodies for non-invasive functional imagining, are also addressed. Finally, we discuss the importance of theranostics in the emerging field of personalized medicine and critically evaluate recent data to determine the best way to apply antibody theranostics in the future.

EGFR gene copy number as a predictive biomarker for resistance to anti-EGFR monoclonal antibodies in metastatic colorectal cancer treatment: a meta-analysis

OBJECTIVE

The epidermal growth factor receptor (EGFR) inhibitors monoclonal antibodies (MoAbs) have already shown the therapeutic effectiveness in patients with metastatic colorectal cancer (mCRC). But many patients resist to the treatment. The aim of this meta-analysis was to assess EGFR gene copy number (GCN) as a candidate predictive biomarker for resistance to anti-EGFR MoAbs in mCRC treatment.

METHODS

Systematic computerized searches of the PubMed, EMBase and Cochrane Library were performed. The primary endpoint was objective response rate (ORR). The second endpoints included progression-free survival (PFS), and overall survival (OS). The pooled odd ratio (OR) and pooled sensitivity, specificity, and summary receiver operator characteristic (SROC) for ORR were estimated. The pooled hazard ratios (HR) for PFS and OS were also calculated.

RESULTS

Fourteen studies with 1,021 patients were included. Increased EGFR GCN was associated with increased ORR (OR=6.905; 95% CI: 4.489-10.620). It was also found in wild-type KRAS mCRC patients, with the pooled OR of 8.133 (95% CI: 4.316-15.326). GCN has medium value for predicting ORR, with the pooled sensitivity of 0.79 (95% CI: 0.73-0.84), the pooled specificity of 0.59 (95% CI: 0.55-0.62). In wild-type KRAS mCRC patients, the sensitivity and the specificity were 0.80 (95% CI: 0.70-0.87) and 0.60 (95% CI: 0.53-0.66), respectively. Increased EGFR GCN was associated with increased PFS (HR=0.557; 95% CI: 0.382-0.732) and OS (HR=0.579; 95% CI: 0.422-0.737).

CONCLUSIONS

This meta-analysis suggests that EGFR GCN represents a predictive biomarker for tumor response in mCRC patients treated with MoAbs regardless of KRAS mutation. mCRC patients with increased EGFR GCN are more likely to have a better response, PFS, and OS when treated with cetuximab or panitumumab.

Personalized oncology in interventional radiology

As personalized medicine becomes more applicable to oncologic practice, image-guided biopsies will be integral for enabling predictive and pharmacodynamic molecular pathology. Interventional radiology has a key role in defining patient-specific management. Advances in diagnostic techniques, genomics, and proteomics enable a window into subcellular mechanisms driving hyperproliferation, metastatic capabilities, and tumor angiogenesis. A new era of personalized medicine has evolved whereby clinical decisions are adjusted according to a patient's molecular profile. Several mutations and key markers already have been introduced into standard oncologic practice. A broader understanding of personalized oncology will help interventionalists play a greater role in therapy selection and discovery.

177Lu-labeled antibodies for EGFR-targeted SPECT/CT imaging and radioimmunotherapy in a preclinical head and neck carcinoma model

Epidermal growth factor receptor (EGFR) has been well characterized as an important target for cancer therapy. Immunotherapy based on EGFR-specific antibodies (e.g., panitumumab and cetuximab) has shown great clinical promise. However, increasing evidence has indicated that only a subgroup of patients receiving these antibodies will benefit from them, and even patients who do initially experience a major response may eventually develop therapeutic resistance. In this study, we investigated whether panitumumab and cetuximab can serve as delivery vehicles for tumor-targeted radionuclide therapy in a preclinical tumor model that did not respond to immunotherapy. The in vitro toxicity and cell binding properties of panitumumab and cetuximab were characterized. Both antibodies were conjugated with 1,4,7,10-tetraazadodecane-N,N',N",N"'-tetraacetic acid (DOTA) and radiolabeled with (177)Lu. Small-animal SPECT/CT, biodistribution, and radioimmunotherapy (RIT) studies of (177)Lu-DOTA-panitumumab ((177)Lu-Pan) and (177)Lu-DOTA-cetuximab ((177)Lu-Cet) were performed in the UM-SCC-22B tumor model. Both (177)Lu-Pan and (177)Lu-Cet exhibited favorable tumor targeting efficacy. The tumor uptake was 20.92 ± 4.45, 26.10 ± 5.18, and 13.27 ± 1.94% ID/g for (177)Lu-Pan, and 15.67 ± 3.84, 15.72 ± 3.49, and 7.82 ± 2.36% ID/g for (177)Lu-Cet at 24, 72, and 120 h p.i., respectively. RIT with a single dose of 14.8 MBq of (177)Lu-Pan or (177)Lu-Cet significantly delayed tumor growth. (177)Lu-Pan induced more effective tumor growth inhibition due to a higher tumor uptake. Our results suggest that panitumumab and cetuximab can function as effective carriers for tumor-targeted delivery of radiation, and that RIT is promising for targeted therapy of EGFR-positive tumors, especially for those tumors that are resistant to antibody-based immunotherapy.

Predictive and prognostic biomarkers with therapeutic targets in breast, colorectal, and non-small cell lung cancers: a systemic review of current development, evidence, and recommendation

Appropriate evidence-based roles of prognostic and predictive biomarkers of known therapeutic targets in breast, colorectal, and non-small cell lung cancers in adults are reviewed, with summary of evidence for use and recommendation. Current development in biomarker studies is also discussed. Computerized literature searches of PubMed (National Library of Medicine), the Cochrane Collaboration Library, and commonly accepted US and international guidelines (American Society of Clinical Oncology, European Society for Medical Oncology, and National Comprehensive Cancer Network) were performed from 2001 to 2012. Literature published before 2001 was noted for historical interest but not evaluated. Literature review was focused on available systematic reviews and meta-analyses of published predictive (associated with treatment response and/or efficacy) and prognostic (associated with disease outcome) biomarkers of known therapeutic targets in colorectal, breast, and non-small cell lung cancers. In general, significant health outcomes (e.g. predicted response to therapy, overall survival, disease-free survival, quality of life, lesser toxicity, and cost-effectiveness) were used for making recommendations. Four breast cancer biomarkers were evaluated, two of which (2D6 genotyping, Oncotype Dx) were considered emerging with insufficient evidence. Seven colorectal cancer biomarkers were evaluated, five of which (EGFR gene expression, K-ras G13D gene mutation, B-raf V600E gene mutation, dihydropyrimidine dehydrogenase deficiency, and UGT1A1 genotyping) were considered emerging. Seven non-small cell lung cancer biomarkers were evaluated, five of which were emerging (EGFR gene expression, ERCC gene expression, RRM1 gene expression, K-ras gene mutation, and TS gene expression). Of all 18 biomarkers evaluated, the following showed evidence of clinical utility and were recommended for routine use in practice: ER/PR and HER2 for breast cancer; K-ras gene mutation (except G13D gene mutation) for colorectal cancer; mismatch repair deficiency or microsatellite instability for colorectal cancer; and EGFR and EML4-ALK gene mutations for non-small cell lung. Not all recommendations for these biomarkers were uniformly supported by all guidelines.

Combination treatment of human pancreatic cancer xenograft models with the epidermal growth factor receptor tyrosine kinase inhibitor erlotinib and oncolytic herpes simplex virus HF10

BACKGROUND

There is the potential to use replication-competent oncolytic viruses to treat cancer. We evaluated the efficacy of HF10, a herpes simplex virus type 1 (HSV-1) mutant, in combination with erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor, in human pancreatic cancer xenograft models.

METHODS

The viability of human pancreatic cancer cell lines (BxPC-3 and PANC-1) treated with HF10 and erlotinib, on their own or in combination, was determined. Effects of erlotinib on HF10 entry into tumor cells were also investigated. BxPC-3 subcutaneous tumor-bearing mice were treated with HF10 and erlotinib, on their own or in combination, with effects on tumor volume determined. Immunohistochemical examination of HSV-1 and CD31 was conducted to assess virus distribution and angiogenesis within tumors. A peritoneally disseminated BxPC-3 xenograft model was evaluated for survival.

RESULTS

HF10 combined with erlotinib demonstrated the highest cytotoxicity against BxPC-3. A combination effect was not observed in PANC-1 cells, and erlotinib did not affect virus entry into tumor cells. In the peritoneally disseminated model, HF10 combined with erlotinib had no beneficial effect on survival. In the subcutaneous tumor model, combination therapy resulted in the inhibition of tumor growth to a greater extent than using each agent on its own. Immunohistochemistry revealed that virus distribution within the tumor persisted in the combination therapy group.

CONCLUSIONS

Combination therapy with HF10 and erlotinib warrants further investigation to establish a new treatment strategy against human pancreatic cancers.

Is biomarker research advancing in the era of personalized medicine for head and neck cancer?

Recent progress in molecular biology and translational research has initiated an era of personalized medicine in head and neck clinical oncology. The genetic information defined by biomarker analysis in tumors and individuals is indispensable for the administration of molecular targeting agents. The epidermal growth factor receptor (EGFR) signaling pathway is an important therapeutic target in head and neck squamous cell carcinoma (HNSCC). The use of an anti-EGFR monoclonal antibody (mAb), cetuximab (Cmab), has been approved for the treatment of patients with head and neck cancer. Although KRAS mutation has been established as a potential biomarker for predicting the efficacy of anti-EGFR mAb in colorectal cancer, little is known about predictive markers for Cmab in head and neck cancer. Optimal predictive and prognostic markers as well as safety markers are required to promote the appropriate clinical use of Cmab and to determine malignant phenotypes in head and neck cancer. This article first reviews the role of EGFR signaling in HNSCC. The article then focuses on Ras/Raf/Mek/Erk and PTEN/PI3K/Akt signaling pathways as predictive markers for Cmab. Subsequently, the molecular basis and clinical outcome of human papillomavirus (HPV)-positive cancer is highlighted, and the potential role of anti-EGFR target therapy for HPV-positive HNSCC is discussed. Finally, the possible mechanism for resistance to anti-EGFR target therapy is reviewed, and I discuss approaches to overcome the resistance with reference to an ongoing clinical trial.

Targeting AKT with the allosteric AKT inhibitor MK-2206 in non-small cell lung cancer cells with acquired resistance to cetuximab

The epidermal growth factor receptor (EGFR) is a central regulator of tumor progression in human cancers. Cetuximab is an anti-EGFR monoclonal antibody that has been approved for use in oncology. Despite clinical success the majority of patients do not respond to cetuximab and those who initially respond frequently acquire resistance. To understand how tumor cells acquire resistance to cetuximab we developed a model of resistance using the non-small cell lung cancer line NCI-H226. We found that cetuximab-resistant (Ctx (R) ) clones manifested strong activation of EGFR, PI3K/AKT and MAPK. To investigate the role of AKT signaling in cetuximab resistance we analyzed the activation of the AKT pathway effector molecules using a human AKT phospho-antibody array. Strong activation was observed in Ctx (R) clones for several key AKT substrates including c-jun, GSK3β, eIF4E, rpS6, IKKα, IRS-1 and Raf1. Inhibition of AKT signaling by siAKT1/2 or by the allosteric AKT inhibitor MK-2206 resulted in robust inhibition of cell proliferation in all Ctx (R) clones. Moreover, the combinational treatment of cetuximab and MK-2206 resulted in further decreases in proliferation than either drug alone. This combinatorial treatment resulted in decreased activity of both AKT and MAPK thus highlighting the importance of simultaneous pathway inhibition to maximally affect the growth of Ctx (R) cells. Collectively, our findings demonstrate that AKT activation is an important pathway in acquired resistance to cetuximab and suggests that combinatorial therapy directed at both the AKT and EGFR/MAPK pathways may be beneficial in this setting.

Cetuximab plus irinotecan in refractory colorectal cancer patients

Since the mid-1980s, it has been known that the epidermal growth factor receptor, an immunoglobulin G cytoplasmic membrane protein and member of the type I subfamily of tyrosine kinase receptors, plays a key role in tumor growth and metastasis. Cetuximab is the first immunoglobulin G1 monoclonal antibody that blocks the epidermal growth factor receptor, resulting in an inhibition of tumor growth, angiogenesis, tumor spread and metastasis. Cetuximab is active in heavily pretreated colorectal cancer, as a single agent or in combination with irinotecan, a conclusion that is strongly suggested by the Bowel Oncology with Cetuximab Antibody (BOND) study in terms of response rate (11% monotherapy vs 23% in combination; p < 0.007) and time to progression (1.5 vs 4.1 months; p < 0.001). The main adverse event related to cetuximab is skin reaction, the intensity of which is correlated with efficacy. The Monoclonal Antibody Erbitux in a European Pre-License (MABEL) study has confirmed these results, recently generating a median survival of 9.2 months, comparable to 8.6 months achieved in the BOND study. Cetuximab has shown efficacy (with or without irinotecan) as second-line treatment in patients who have failed irinotecan in combination with bevacizumab, an antivascular endothelial growth factor monoclonal antibody. The combination is currently being tested in the first-line management of advanced colorectal cancer, as well as in the adjuvant setting. The evaluation of other combinations either with oxaliplatin or capecitabine, is ongoing, with preliminary reports of promising activity.

Predicting response to epidermal growth factor receptor-targeted therapy in colorectal cancer

The discovery over 20 years ago by the Nobel Laureate Stanley Cohen of epidermal growth factor and its receptor, followed by the recognition that this receptor is overexpressed in multiple cancer types, has been of phenomenal significance. From these events the 'Holy Grail' of targeted therapy has looked increasingly realistic. Over the last 5 years this work has come of age with the licensing of multiple agents targeting this important mitogenic pathway in multiple tumor types. However, these agents and the technology behind them, while impressive, have resulted in lower clinical response rates than anticipated. In this review we will focus on the epidermal growth factor receptor-targeted therapies in colorectal cancer, why our expectations from these therapies have not yet been fulfilled and how we may predict those cancers that are likely to respond or be resistant to these therapies through a greater appreciation of the intricacy, diversity and dynamism of cellular signaling mechanisms.

Panitumumab in colorectal cancer

The combination of chemotherapy and targeted therapies is rapidly becoming the standard of care in the treatment of metastatic colorectal cancer. Panitumumab (formerly ABX-EGF) is a fully human antibody developed to target the human epidermal growth factor receptor (EGFR/HER-1), which is expressed in up to 75% of patients with colorectal cancer. As a fully human antibody, panitumumab can be administered without any premedication and few infusion reactions have been reported. It has recently been approved in the USA for the treatment of colorectal cancer as a single agent in the salvage setting. Ongoing studies are being performed to determine whether the addition of panitumumab to standard treatment for metastatic colorectal cancer will improve the survival of these patients.

Optimal treatment of metastatic colorectal cancer

For over 40 years, fluorouracil has been the only drug registered for the treatment of metastatic colorectal cancer. During the past 5 years, combination chemotherapy regimens including either irinotecan or oxaliplatin have proven to be superior to fluorouracil monotherapy in randomized clinical trials, in terms of response rate, progression-free survival and overall survival. Both doublets demonstrated similar efficacy, therefore either combination can be considered standard first-line treatment for metastatic colorectal cancer. Recently, a new orally active fluorouracil analog, capecitabine, and two targeted biological agents, cetuximab and bevacizumab, have been added to the armamentarium of drugs active against metastatic colorectal cancer, thus making the scenario more complex. Moreover, ongoing clinical trials are currently testing new promising molecularly targeted agents. Thus, we are facing a new era in which the rapid clinical development of novel agents is outpacing the ability to perform Phase III clinical trials. At present, there is no single standard treatment suitable for all patients. However, general principles of management can be derived from the available clinical data in order to guide the therapeutic choice and individualize treatment.

New approaches in systemic treatment of advanced colorectal cancer: the molecular targets era

The prognosis of advanced colorectal cancer remains poor in spite of the advances obtained in recent years with new therapeutic agents, new approaches in surgical procedures and new diagnostic methods. New treatments directed to molecular targets have emerged and are being developed to improve these results, but there is a need to optimize and define the best use of these new approaches. In this review, the authors examine the most important trials with monoclonal antibodies and tyrosine kinase inhibitors in the treatment of advanced colorectal cancer.

Sorafenib and irinotecan (NEXIRI) as second- or later-line treatment for patients with metastatic colorectal cancer and KRAS-mutated tumours: a multicentre Phase I/II trial

Background:

This trial evaluated the feasibility and efficacy of combined sorafenib and irinotecan (NEXIRI) as second- or later-line treatment of patients with KRAS-mutated metastatic colorectal cancer (mCRC), who had progressed after irinotecan-based chemotherapy.

Methods:

In Phase I, in a 3+3 dose escalation schedule, patients received irinotecan (125, 150 or 180 mg m⁻² every 2 weeks), in combination with 400 mg sorafenib b.d. The primary end point was the maximum-tolerated dose of irinotecan. In Phase II, the primary end point was disease control rate (DCR). Secondary end points were progression-free survival (PFS), overall survival (OS) and toxicity.

Results:

Phase I included 10 patients (median age 63 (49–73)); no dose-limiting toxicity was seen. In Phase II, 54 patients (median age 60 (43–80) years) received irinotecan 180 mg m⁻² every 2 weeks with sorafenib 400 mg b.d. Nine patients (17%) remained on full-dose sorafenib. The DCR was 64.9% (95% CI, 51–77). Median PFS and OS were 3.7 (95% CI, 3.2–4.7) and 8.0 (95% CI, 4.8–9.7) months, respectively. Toxicities included Grade 3 diarrhoea (37%), neutropenia (18%), hand-foot syndrome (13%) and Grade 4 neutropenia (17%).

Conclusion:

The NEXIRI regimen showed promising activity as second- or later-line treatment in this heavily pretreated mCRC population (ClinicalTrials.gov NCT00989469).

The prognostic values of EGFR expression and KRAS mutation in patients with synchronous or metachronous metastatic colorectal cancer

BACKGROUND

The epidermal growth factor receptor (EGFR)/RAS/RAF/MEK/MAPK pathway is an important pathway in the carcinogenesis, invasion and metastasis of colorectal cancers (CRCs). We conducted a retrospective study to determine the prognostic values of EGFR expression and KRAS mutation in patients with metastatic CRC (mCRC) based on synchronous or metachronous status.

METHODS

From October 2002 to March 2012, 205 patients with mCRC were retrospectively analyzed; 98 were found to have metachronous mCRC while 107 were found to have synchronous mCRC. The EGFR expressions were determinate by IHC (immunohistochemistry) analysis and categorized 1+ (weak intensity), 2+ (moderate intensity), and 3+ (strong intensity). Genomic DNA was isolated from frozen primary CRC tissues and direct sequencing of KRAS was performed. The clinicopathological features of these mCRC patients were retrospectively investigated according to EGFR expression and KRAS mutation status. Moreover, we analyzed the prognostic values of EGFR expression and KRAS mutation among these patients.

RESULTS

Of the 205 patients with mCRC, EGFR expression was analyzed in 167 patients, and positive EGFR expression was noted in 140 of those patients (83.8%). KRAS mutation was investigated in 205 patients and mutations were noted in 88 of those patients (42.9%). In patients with metachronous mCRC, positive EGFR expression was significantly correlated with well-and moderately-differentiated tumors (P=0.028), poorer disease-free survival (DFS) (P<0.001), and overall survival (OS) (P<0.001). Furthermore, positive EGFR expression was a significant independent prognostic factor of DFS (P=0.006, HR: 4.012, 95% CI: 1.130-8.445) and OS (P=0.028, HR: 3.090, 95% CI: 1.477-10.900) in metachronous mCRC patients. KRAS mutation status was not significantly related to DFS and OS of patients with metachronous mCRC; likewise, KRAS mutation status was not significantly different in the progression-free survival (PFS) and OS of patients with synchronous mCRC (all P>0.05).

CONCLUSIONS

The present study demonstrated that EGFR expression has prognostic value only for patients with metachronous mCRC. However, KRAS mutation did not have prognostic value in patients with metachronous or synchronous mCRC.

Colon cancer cells escape 5FU chemotherapy-induced cell death by entering stemness and quiescence associated with the c-Yes/YAP axis

PURPOSE

Metastasis and drug resistance are the major limitations in the survival and management of patients with cancer. This study aimed to identify the mechanisms underlying HT29 colon cancer cell chemoresistance acquired after sequential exposure to 5-fluorouracil (5FU), a classical anticancer drug for treatment of epithelial solid tumors. We examined its clinical relevance in a cohort of patients with colon cancer with liver metastases after 5FU-based neoadjuvant chemotherapy and surgery.

RESULTS

We show that a clonal 5F31 cell population, resistant to 1 μmol/L 5FU, express a typical cancer stem cell-like phenotype and enter into a reversible quiescent G0 state upon reexposure to higher 5FU concentrations. These quiescent cells overexpressed the tyrosine kinase c-Yes that became activated and membrane-associated upon 5FU exposure. This enhanced signaling pathway induced the dissociation of the Yes/YAP (Yes-associated protein) molecular complex and depleted nuclear YAP levels. Consistently, YES1 silencing decreased nuclear YAP accumulation and induced cellular quiescence in 5F31 cells cultured in 5FU-free medium. Importantly, YES1 and YAP transcript levels were higher in liver metastases of patients with colon cancer after 5FU-based neoadjuvant chemotherapy. Moreover, the YES1 and YAP transcript levels positively correlated with colon cancer relapse and shorter patient survival (P < 0.05 and P < 0.025, respectively).

CONCLUSIONS

We identified c-Yes and YAP as potential molecular targets to eradicate quiescent cancer cells and dormant micrometastases during 5FU chemotherapy and resistance and as predictive survival markers for colon cancer.

[A perspective: role of targeted therapy in colon cancer]

Colorectal cancer is the third most common malignant disease in incidence according to a report in 2009 from Korea. The 5-fluorouracil (5-FU) remains to be a major chemotherapeutic agents. But, over the last 10-15 years, the treatment pattern for metastatic colorectal cancer changed significantly. Irinotecan and oxaliplatin are cytotoxic drugs, or bevacizumab and cetuximab are monoclonal antibodies against molecular targets. The introduction of novel agents targeting specific molecular features of cancer cells promises more options and marked improvements in efficacy for the treatment of metastatic colon cancer. Bevacizumab has been shown to extend survival in colorectal cancer when used in combination with irinotecan and 5-FU-based chemotherapy, and the addition of cetuximab to irinotecan and 5-FU-based chemotherapy eliminates irinotecan resistance. Better understanding of the tumor biology and the molecular pathway and mechanisms of tumorigenesis has led to the discovery of novel agents with improved outcomes.

Personalized treatment for advanced colorectal cancer: KRAS and beyond

Targeted therapies have improved the survival of patients with advanced colorectal cancer (CRC). However, further improvements in patient outcomes may be gained by the development of predictive biomarkers in order to select individuals who are most likely to benefit from treatment, thus personalizing treatment. Using the epidermal growth-factor receptor (EGFR) pathway, we discuss the existing and potential predictive biomarkers in clinical development for use with EGFR-targeted agents in metastatic CRC. The data and technological issues surrounding such biomarkers as expression of EGFR or its family members or ligands, KRAS-, NRAS-, and BRAF-mutation status, PI3K/PTEN expression, and imaging and clinical biomarkers, such as rash and hypomagnesemia, are summarized. Although the discovery of KRAS mutations has improved patient selection for EGFR-targeted treatments, further biomarkers are required, especially for those patients who exhibit KRAS mutations rather than the wild-type gene.

The ErbB/HER family of protein-tyrosine kinases and cancer

The human epidermal growth factor receptor (EGFR) family consists of four members that belong to the ErbB lineage of proteins (ErbB1-4). These receptors consist of a glycosylated extracellular domain, a single hydrophobic transmembrane segment, and an intracellular portion with a juxtamembrane segment, a protein kinase domain, and a carboxyterminal tail. Seven ligands bind to EGFR including epidermal growth factor and transforming growth factor α, none bind to ErbB2, two bind to ErbB3, and seven ligands bind to ErbB4. The ErbB proteins function as homo and heterodimers. The heterodimer consisting of ErbB2, which lacks a ligand, and ErbB3, which is kinase impaired, is surprisingly the most robust signaling complex of the ErbB family. Growth factor binding to EGFR induces a large conformational change in the extracellular domain, which leads to the exposure of a dimerization arm in domain II of the extracellular segment. Two ligand-EGFR complexes unite to form a back-to-back dimer in which the ligands are on opposite sides of the aggregate. Following ligand binding, EGFR intracellular kinase domains form an asymmetric homodimer that resembles the heterodimer formed by cyclin and cyclin-dependent kinase. The carboxyterminal lobe of the activator kinase of the dimer interacts with the amino-terminal lobe of the receiver kinase thereby leading to its allosteric stimulation. Downstream ErbB signaling modules include the phosphatidylinositol 3-kinase/Akt (PKB) pathway, the Ras/Raf/MEK/ERK1/2 pathway, and the phospholipase C (PLCγ) pathway. Several malignancies are associated with the mutation or increased expression of members of the ErbB family including lung, breast, stomach, colorectal, head and neck, and pancreatic carcinomas and glioblastoma (a brain tumor). Gefitinib, erlotinib, and afatinib are orally effective protein-kinase targeted quinazoline derivatives that are used in the treatment of ERBB1-mutant lung cancer. Lapatinib is an orally effective quinazoline derivative used in the treatment of ErbB2-overexpressing breast cancer. Trastuzumab, pertuzumab, and ado-trastuzumab emtansine, which are given intravenously, are monoclonal antibodies that target the extracellular domain and are used for the treatment of ErbB2-positive breast cancer; ado-trastuzumab emtansine is an antibody-drug conjugate that delivers a cytotoxic drug to cells overexpressing ErbB2. Cetuximab and panitumumab are monoclonal antibodies that target ErbB1 and are used in the treatment of colorectal cancer. Cancers treated with these targeted drugs eventually become resistant to them. The role of combinations of targeted drugs or targeted drugs with cytotoxic therapies is being explored in an effort to prevent or delay drug resistance in the treatment of these malignancies.

Open-label, multicentre expansion cohort to evaluate imgatuzumab in pre-treated patients with KRAS-mutant advanced colorectal carcinoma

AIM

Imgatuzumab (GA201) is a novel anti-epidermal growth factor receptor (anti-EGFR) antibody glycoengineered for enhanced antibody-dependent cell-mediated cytotoxicity (ADCC). We investigated the efficacy of imgatuzumab in patients with EGFR-positive, KRAS-mutant advanced colorectal cancer.

METHODS

Patients received single-agent imgatuzumab (1400mg on day 1 and 8 followed by q2W) as third line therapy in an open-label, multicentre, non-randomised, expansion study. The primary end-point was tumour response. Pre- and on-treatment biopsies and blood samples were investigated for biomarkers related to imgatuzumab's believed mechanism of action (MoA).

RESULTS

25 patients were treated and the best overall response was stable disease occurring in 40% of patients at 8weeks, 24% at 16weeks and 8% (two patients) at 32weeks. Median overall survival was 9.3months (95% confidence interval (CI): 5.1-12.3). Treatment-related rash, hypomagnesaemia and infusion-related reactions were the most common adverse events. Comparison of pre- and post-treatment biopsies revealed that the number of tumour-infiltrating immune cells increased notably after one cycle of therapy (median compound immune reactive score of 1491 versus 898 cells/mm(3) at baseline), whereas the number of peripheral natural killer cells decreased. A potential association between baseline tumour immune infiltration and clinical efficacy was seen.

CONCLUSIONS

These data may suggest that the MoA of imgatuzumab involves ADCC-related immune effects in the tumour and is not limited to simple receptor blockade.

Genetic and immune factors underlying the efficacy of cetuximab and panitumumab in the treatment of patients with metastatic colorectal cancer

Efficacy of monoclonal anti-EGFR antibodies (cetuximab, panitumumab) used in combination with chemotherapy or alone has been demonstrated in clinical trials of patients with mCRC. Both drugs block signaling EGFR pathway in malignant cells (blocking ligand binding and EGFR dimerization). Obtaining treatment responses with anti-EGFR agents is possible only in a selected subgroup of patients with mCRC. Successful treatment with cetuximab and panitumab is possible almost exclusively in patients without RAS mutations. Research on predictive value of EGFR gene copy number, PI3KCA gene mutations, P53 and PTEN, and EGFR their ligands concentrations is ongoing. Cetuximab, as IgG1 class antibody, can cause antibody dependent cellular cytotoxicity against neoplasm cells, while panitumumab, as IgG2 class antibody, does not induce such effect. Therefore a potential predictor cetuximab therapy may be the presence of different polymorphic forms of the genes for receptor immunoglobulin Fc fragments: FcγRIIa and FcγRIII subclasses.

Epidermal growth factor receptor-targeted therapy in squamous cell carcinoma of the penis: a report of 3 cases

OBJECTIVE

To describe 3 cases of advanced refractory penile cancer treated with targeted therapy against the epidermal growth factor receptor (EGFR).

MATERIALS AND METHODS

We identified 3 patients with advanced penile cancer who had disease progression after platinum chemotherapy refractory and who subsequently received EGFR-targeted therapy. Their tumor tissue was evaluated for expression of EGFR by immunohistochemistry and messenger ribonucleic acid quantitation and was also tested for the presence of human papillomavirus deoxyribonucleic acid by line hybridization. K-ras mutation was evaluated by polymerase chain reaction for 6 mutations in codon 12 and 1 mutation in codon 13.

RESULTS

One patient responded to cetuximab and remains disease-free 42 months after presentation. One patient responded to panitumumab, then suffered relapse. One other progressed through EGFR-targeted therapy. EGFR expression by immunohistochemistry was 1-2+ in all cases, and messenger ribonucleic acid expression ranged from 4.08 to 7.33. No K-ras mutations or human papillomavirus deoxyribonucleic acid was detected.

CONCLUSION

We report 3 cases in which EGFR-targeted therapy was used to treat platinum-refractory penile cancer patients. Because 2 of the 3 had clinical benefit, future prospective trials of EGFR-targeted therapy in penile cancer are warranted.

Molecularly targeted drugs for metastatic colorectal cancer

The survival rate of patients with metastatic colorectal cancer (mCRC) has significantly improved with applications of molecularly targeted drugs, such as bevacizumab, and led to a substantial improvement in the overall survival rate. These drugs are capable of specifically targeting the inherent abnormal pathways in cancer cells, which are potentially less toxic than traditional nonselective chemotherapeutics. In this review, the recent clinical information about molecularly targeted therapy for mCRC is summarized, with specific focus on several of the US Food and Drug Administration-approved molecularly targeted drugs for the treatment of mCRC in the clinic. Progression-free and overall survival in patients with mCRC was improved greatly by the addition of bevacizumab and/or cetuximab to standard chemotherapy, in either first- or second-line treatment. Aflibercept has been used in combination with folinic acid (leucovorin)-fluorouracil-irinotecan (FOLFIRI) chemotherapy in mCRC patients and among patients with mCRC with wild-type KRAS, the outcomes were significantly improved by panitumumab in combination with folinic acid (leucovorin)-fluorouracil-oxaliplatin (FOLFOX) or FOLFIRI. Because of the new preliminary studies, it has been recommended that regorafenib be used with FOLFOX or FOLFIRI as first- or second-line treatment of mCRC chemotherapy. In summary, an era of new opportunities has been opened for treatment of mCRC and/or other malignancies, resulting from the discovery of new selective targeting drugs.