Epidermal growth factor receptor (EGFR) status in primary colorectal tumors does not correlate with EGFR expression in related metastatic sites: implications for treatment with EGFR-targeted monoclonal antibodies

Effect of erlotinib on epidermal growth factor receptor and downstream signaling in oral cavity squamous cell carcinoma

BACKGROUND

The purpose of this study was to determine if there are differences in biomarker modulation and epidermal growth factor receptor (EGFR) degradation between the tumor and the normal mucosa after treatment with an EGFR inhibitor, erlotinib, in head and neck cancer.

METHODS

Patients with primary oral cavity squamous cell cancers received a course of erlotinib, 150 mg every day for 7 days before surgical resection. Tumor and normal mucosa biopsies were obtained both pre-erlotinib and post-erlotinib. Changes in known markers of EGFR activity (phospho, AKT, STAT3) were measured by immunoblotting, whereas changes in tissue distribution were analyzed by immunohistochemical analysis.

RESULTS

Twelve patients were enrolled; 7 had evaluable paired tumors and normal mucosa biopsies pretreatment and posttreatment. Expression of EGFR was higher in tumors compared to the normal mucosa (p = .005). Erlotinib administration was associated with marked inhibition of phosphorylated epidermal growth factor receptor (pEGFR) and reduction in total EGFR protein (p = .004, p = .007) in tumors, whereas there was heterogeneity in EGFR inhibition in the normal mucosa (p = .10 [pEGFR], and p = .07 [EGFR]). Reduced levels of pSrc and pSTAT3 and enhanced p27 levels were noted in tumors after erlotinib. Cell culture studies confirmed that EGFR is degraded in tumor cells after prolonged treatment with erlotinib.

CONCLUSION

Our results show that EGFR inhibition by erlotinib led to a marked reduction in EGFR protein levels in patients. Differential effects of erlotinib on tumors compared to the normal mucosa suggest there may be individual patient heterogeneity. These preliminary data suggest EGFR degradation should be further analyzed as a potential biomarker in selecting patients likely to benefit from EGFR inhibitors.

The orexin receptor OX(1)R in colon cancer: a promising therapeutic target and a new paradigm in G protein-coupled receptor signalling through ITIMs

An exciting aspect of the heptahelical orexin receptor 1 (OX(1)R) has emerged recently, when it was shown that it drives apoptosis in human colon cancer cell lines. Here we review recent findings related to the role of OX(1)R in colorectal cancers and the unexpected mechanism whereby this G protein-coupled receptor works. The OX(1)R is aberrantly expressed at all steps of primary colorectal tumour progression and after local (lymph node) or distant (liver, lung) metastasis. No OX(1)R is detected in normal colonic epithelial cells. Treatment of human colon cancer cells in culture with orexins promotes robust apoptosis and subsequent reduction of growth including in cells that are resistant to 5-fluorouracil, the most commonly used drug in chemotherapy. When human colon cancer cells are xenografted in nude mice, treatment with orexins dramatically slows tumour growth and even reverses the development of established tumours. Thus, OX(1)R agonists might be novel candidates for colon cancer therapy. Activation of OX(1)R drives apoptosis through G(q) protein but independently of classical Gα(q) activation of phospholipase C. In fact, it is the freed βγ dimer of G(q) that plays a pivotal role by stimulating Src-tyrosine kinase. This results in phosphorylation of two immunoreceptor tyrosine-based inhibitory motifs (ITIM) in OX(1)R and subsequent recruitment by OX(1)R of the phosphotyrosine phosphatase SHP-2, which is activated thereby. Downstream events include release of cytochrome c from mitochondria and activation of caspase-3 and caspase-7. The role of ITIMs in OX(1)R-driven apoptosis represents a new paradigm of G protein-coupled receptor signalling.

Prognostic and predictive biomarkers for epidermal growth factor receptor-targeted therapy in colorectal cancer: beyond KRAS mutations

The advent of the epidermal growth factor receptor (EGFR)-targeted monoclonal antibodies (mAbs), cetuximab and panitumumab has expanded the range of treatment options for metastatic colorectal cancer (CRC). Despite these agents have paved the way to individualized therapy, our understanding why some patients respond to treatment whereas others do not remain poor. The realization that detection of positive EGFR expression by IHC does not reliably predict clinical outcome of EGFR-targeted treatment has led to an intense search for alternative predictive biomarkers. Data derived from multiple phase III trials have indicated that KRAS mutations can be considered a highly specific negative biomarker of benefit to anti-EGFR mAbs. Oncologists are now facing emerging issues in the treatment of metastatic CRC, including the identification of additional genetic determinants of primary resistance to EGFR-targeted therapy for further improving selection of patients, the explanation of rare cases of patients carrying KRAS-mutated tumours who have been reported to respond to cetuximab and panitumumab and the discovery of mechanisms of secondary resistance to EGFR-targeted therapy. Current data suggest that, together with KRAS mutations, the evaluation of EGFR gene copy number (GCN), BRAF, NRAS, PIK3CA mutations or loss of PTEN expression could also be useful for selecting patients with reduced chance to benefit from anti-EGFR mAbs. This review aims to provide an updated of the most recent data on predictive and prognostic biomarkers within the EGFR pathway, the challenges this emerging field presents and the future role of these molecular markers in CRC treatment.

Phase III trial of cetuximab with continuous or intermittent fluorouracil, leucovorin, and oxaliplatin (Nordic FLOX) versus FLOX alone in first-line treatment of metastatic colorectal cancer: the NORDIC-VII study

PURPOSE

The NORDIC-VII multicenter phase III trial investigated the efficacy of cetuximab when added to bolus fluorouracil/folinic acid and oxaliplatin (Nordic FLOX), administered continuously or intermittently, in previously untreated metastatic colorectal cancer (mCRC). The influence of KRAS mutation status on treatment outcome was also investigated.

PATIENTS AND METHODS

Patients were randomly assigned to receive either standard Nordic FLOX (arm A), cetuximab and FLOX (arm B), or cetuximab combined with intermittent FLOX (arm C). Primary end point was progression-free survival (PFS). Overall survival (OS), response rate, R0 resection rate, and safety were secondary end points.

RESULTS

Of the 571 patients randomly assigned, 566 were evaluable in intention-to-treat (ITT) analyses. KRAS and BRAF mutation analyses were obtained in 498 (88%) and 457 patients (81%), respectively. KRAS mutations were present in 39% of the tumors; 12% of tumors had BRAF mutations. The presence of BRAF mutations was a strong negative prognostic factor. In the ITT population, median PFS was 7.9, 8.3, and 7.3 months for the three arms, respectively (not significantly different). OS was almost identical for the three groups (20.4, 19.7, 20.3 months, respectively), and confirmed response rates were 41%, 49%, and 47%, respectively. In patients with KRAS wild-type tumors, cetuximab did not provide any additional benefit compared with FLOX alone. In patients with KRAS mutations, no significant difference was detected, although a trend toward improved PFS was observed in arm B. The regimens were well tolerated.

CONCLUSION

Cetuximab did not add significant benefit to the Nordic FLOX regimen in first-line treatment of mCRC.

Differential response to EGFR- and VEGF-targeted therapies in patient-derived tumor tissue xenograft models of colon carcinoma and related metastases

Heterogeneity in primary tumors and related metastases may result in failure of antitumor therapies, particularly in targeted therapies for the treatment of cancer. In this study, patient-derived tumor tissue (PDTT) xenograft models of colon carcinoma with lymphatic and hepatic metastases were used to evaluate the response to EGFR- and VEGF-targeted therapies. Our results showed that primary colon carcinoma and its corresponding lymphatic and hepatic metastases have a different response rate to anti-EGFR (cetuximab) and anti-VEGF (bevacizumab) therapies. However, the underlying mechanism of these types of phenomenon is still unclear. To investigate whether such phenomena may result from the heterogeneity in primary colon carcinoma and related metastases, we compared the expression levels of cell signaling pathway proteins using immunohistochemical staining and western blotting, and the gene status of KRAS using pyrosequencing in the same primary colon carcinoma and its corresponding lymphatic and hepatic metastatic tissues which were used for establishing the PDTT xenograft models. Our results showed that the expression levels of EGFR, VEGF, Akt/pAkt, ERK/pERK, MAPK/pMAPK, and mTOR/pmTOR were different in primary colon carcinoma and matched lymphatic and hepatic metastases although the KRAS gene status in all cases was wild-type. Our results indicate that the heterogeneity in primary colon carcinoma and its corresponding lymphatic and hepatic metastases may result in differences in the response to dual-inhibition of EGFR and VEGF.

Phosphorylated AKT and MAPK expression in primary tumours and in corresponding metastases and clinical outcome in colorectal cancer patients receiving irinotecan-cetuximab

Background

Clinical observations suggested that a non negligible proportion of patients, ranging from 40% to 70%, does not seem to benefit from the use of anti-EGFR targeted antibodies even in the absence of a mutation of the K- RAS gene. The EGFR pathway activation via the Ras-Raf-MAP-kinase and the protein-serine/threonine kinase AKT could determine resistance to anti-EGFR treatment.

Methods

We tested the interaction between phosphorylated AKT and MAPK expression in colorectal tumours and corresponding metastases and global outcome in K-RAS wild type patients receiving irinotecan-cetuximab.

Results

Seventy-two patients with histologically proven metastatic colorectal cancer, treated with Irinotecan and Cetuximab based chemotherapy, were eligible for our analysis.

In metastases pAKT correlated with RR (9% vs. 58%, p = 0.004), PFS (2.3 months vs.9.2 months p < 0.0001) and OS (6.1 months vs.26.7 months p < 0.0001) and pMAPK correlated with RR (10% vs., 47%, p = 0.002), PFS (2.3 months vs.8.6 months p < 0.0001) and OS (7.8 months vs.26 months p = 0.0004). At multivariate analysis pAKT and pMAPK in metastases were able to independently predict PFS. pAKT in metastases independently correlated with RR as well

Discussion

pAKT and pMAPK expression in metastases may modulate the activity of EGFR-targeted antibodies. We could speculate that in patients with pAKT and pMAPK metastases expression targeting these factors may be crucial.

Molecular pathology of lung cancer: key to personalized medicine

The majority of lung adenocarcinoma patients with epidermal growth factor receptor- (EGFR) mutated or EML4-ALK rearrangement-positive tumors are sensitive to tyrosine kinase inhibitors. Both primary and acquired resistance in a significant number of those patients to these therapies remains a major clinical problem. The specific molecular mechanisms associated with tyrosine kinase inhibitor resistance are not fully understood. Clinicopathological observations suggest that molecular alterations involving so-called 'driver mutations' could be used as markers that aid in the selection of patients most likely to benefit from targeted therapies. In this review, we summarize recent developments involving the specific molecular mechanisms and markers that have been associated with primary and acquired resistance to EGFR-targeted therapy in lung adenocarcinomas. Understanding these mechanisms may provide new treatment avenues and improve current treatment algorithms.

Immunohistochemical discrimination of wild-type EGFR from EGFRvIII in fixed tumour specimens using anti-EGFR mAbs ICR9 and ICR10

Background:

The human epidermal growth factor receptor (EGFR) is an important therapeutic target in oncology, and three different types of EGFR inhibitors have been approved for the treatment of cancer patients. However, there has been no clear association between the expression levels of EGFR protein in the tumours determined by the FDA-approved EGFR PharmDx kit (Dako) or other standard anti-EGFR antibodies and the response to the EGFR inhibitors.

Method:

In this study, we investigated the potential of our anti-EGFR monoclonal antibodies (mAbs; ICR9, ICR10, ICR16) for immunohistochemical diagnosis of wild-type EGFR and/or the type-III deletion mutant form of EGFR (EGFRvIII) in formalin-fixed, paraffin-embedded human tumour specimens.

Results:

We found that the anti-EGFR mAb in the EGFR PharmDx kit stained both wild-type and EGFRvIII-expressing cells in formalin-fixed, paraffin-embedded sections. This pattern of EGFR immunostaining was also found with our anti-EGFR mAb ICR16. In contrast, mAbs ICR10 and ICR9 were specific for the wild-type EGFR.

Conclusion:

We conclude that mAbs ICR9 and ICR10 are ideal tools for investigating the expression patterns of wild-type EGFR protein in tumour specimens using immunohistochemistry, and to determine their prognostic significance, as well as predictive value for response to therapy with EGFR antibodies.

Assessment of a novel VEGF targeted agent using patient-derived tumor tissue xenograft models of colon carcinoma with lymphatic and hepatic metastases

The lack of appropriate tumor models of primary tumors and corresponding metastases that can reliably predict for response to anticancer agents remains a major deficiency in the clinical practice of cancer therapy. It was the aim of our study to establish patient-derived tumor tissue (PDTT) xenograft models of colon carcinoma with lymphatic and hepatic metastases useful for testing of novel molecularly targeted agents. PDTT of primary colon carcinoma, lymphatic and hepatic metastases were used to create xenograft models. Hematoxylin and eosin staining, immunohistochemical staining, genome-wide gene expression analysis, pyrosequencing, qRT-PCR, and western blotting were used to determine the biological stability of the xenografts during serial transplantation compared with the original tumor tissues. Early passages of the PDTT xenograft models of primary colon carcinoma, lymphatic and hepatic metastases revealed a high degree of similarity with the original clinical tumor samples with regard to histology, immunohistochemistry, genes expression, and mutation status as well as mRNA expression. After we have ascertained that these xenografts models retained similar histopathological features and molecular signatures as the original tumors, drug sensitivities of the xenografts to a novel VEGF targeted agent, FP3 was evaluated. In this study, PDTT xenograft models of colon carcinoma with lymphatic and hepatic metastasis have been successfully established. They provide appropriate models for testing of novel molecularly targeted agents.

Beyond KRAS: perspectives on new potential markers of intrinsic and acquired resistance to epidermal growth factor receptor inhibitors in metastatic colorectal cancer

The monoclonal antibodies cetuximab and panitumumab, directed against the epidermal growth factor receptor (EGFR), are licensed for the treatment of KRAS wild-type metastatic colorectal cancer (mCRC). Such 'molecular restriction' derived from post-hoc analyses of randomized trials and from other retrospective series all indicate how tumors bearing KRAS (v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) mutations are resistant to EGFR inhibition. Even if highly sensitive for nonresponse, KRAS testing is not very specific. In fact, a limited but still considerable proportion of KRAS wild-type patients rapidly progress on treatment with an EGFR inhibitor. New potential molecular determinants of benefit from such treatment are under investigation and may further refine the selection of patients. Pharmacogenomic analyses and translational studies are also ongoing for exploring the field of acquired resistance to anti-EGFRs, since all patients eventually progress. New biological data are awaited for optimizing the use of molecular agents in colorectal cancer and for identifying promising targets that could allow to better understand and, potentially, overcome mechanisms of primary or secondary resistance to EGFR inhibitors.

The landscape of EGFR pathways and personalized management of non-small-cell lung cancer

Two classes of anti-EGF receptor (EGFR) agents, monoclonal anti-EGFR antibodies and small-molecule EGFR tyrosine kinase inhibitors, have been used for the treatment of non-small-cell lung cancer (NSCLC). However, only a subset of patients will benefit from EGFR-targeted therapy. The discovery of biomarkers that select the appropriate patients for the therapy and predict the responses to the therapy is urgently needed. Molecular genetic analyses provide new insights into EGFR pathway alterations and demonstrate promise for predicting the clinical outcome of patients with NSCLC. In this article, we summarize the latest available knowledge on the clinical impact of EGFR mutations, gene copy number, EGFR overexpression, phosphorylation expression and the alteration of the EGFR pathway downstream factors in predicting the response to EGFR-targeted therapy in NSCLC patients. The role of KRAS and BRAF mutations and ALK rearrangement in lung cancer-targeted therapy, are also reviewed.

Molecular differences in the KRAS gene mutation between a primary tumor and related metastatic sites - case report and a literature review

In recent years the the set of diagnostic tools in colorectal cancers has been extended by the assessment of the KRAS gene status. Currently it is a necessary step in order to qualify patients for the targeted therapy. The results of the analysis of several studies revealed a high rate of compliance of the KRAS gene mutational status in primary and metastatic tumors. In this paper we present a rare case of incompatibility of the KRAS mutations in the primary tumor located in the colon and metastatic changes in the liver.

Biweekly cetuximab plus irinotecan as second-line chemotherapy for patients with irinotecan-refractory and KRAS wild-type metastatic colorectal cancer according to epidermal growth factor receptor expression status

BACKGROUND

Cetuximab plus irinotecan has been shown to be effective in metastatic colorectal cancer (mCRC) patients with wild-type (WT) KRAS and positive EGFR expressions (EGFR+). Retrospective analysis revealed that the efficacy of cetuximab was similar in mCRC patients negative (EGFR-) and positive for EGFR. However, the efficacy of cetuximab has not been assessed prospectively in EGFR- mCRC patients.

METHODS

This was a prospective, multicenter phase II study assessed the efficacy and safety of biweekly cetuximab (500 mg/m(2)) and irinotecan (150-180 mg/m(2)) in patients with histologically proven adenocarcinoma with WT-KRAS and measurable lesion(s), either EGFR + or EGFR-, determined immunohistochemically, who failed first-line irinotecan-containing chemotherapy. The primary endpoint was response rate (RR), and the secondary endpoints included safety, progression-free survival (PFS) and overall survival (OS).

RESULTS

Forty patients were enrolled; 20 EGFR + and 20 EGFR-; their baseline characteristics were balanced. The overall RR was 45% (18/40, 95% CI 29.6-60.4), 55% (11/20) in EGFR + and 35% (7/20) in EGFR- patients. Median PFS was 7.1 months (95% CI 4.8-9.4), 8.3 months in EGFR + and 4.9 months in EGFR- patients. Median OS was 18.5 months (95% CI 15.2-21.8), 17.2 months in EGFR + and 18.5 months in EGFR- patients. Grade 3 or 4 toxicities included neutropenia in 5 patients (12.5%) and febrile neutropenia/skin rash/asthenia in 2 (5%).

CONCLUSIONS

Biweekly cetuximab plus irinotecan as second-line treatment showed significant anti-tumor activity in patients with irinotecan-refractory mCRC and WT-KRAS regardless of EGFR expression status.

Epidermal growth factor receptor (EGFR) gene promoter methylation and cetuximab treatment in colorectal cancer patients

Background:

Epidermal growth factor receptor (EGFR) promoter methylation may be responsible for the loss of EGFR expression in neoplastic cells. The primary aim of our study was to verify a possible correlation between EGFR gene promoter methylation and clinical outcome in metastatic colorectal cancer patients receiving chemotherapy with irinotecan and cetuximab.

Methods:

Colorectal samples from patients treated with irinotecan–cetuximab were analysed for EGFR promoter methylation and EGFR immunohistochemistry.

Results:

Fifty-two patients were analysed. Thirty patients (58%) showed EGFR promoter hypermethylation. In EGFR promoter methylated and EGFR promoter unmethylated patients, we observed a partial response in 3 (10%) and 13 (59%) patients, respectively (P=0.03), progressive disease was obtained in 19 (63%) and 2 (9%) patients, respectively, with EGFR promoter methylated and EGFR promoter unmethylated tumours (P=0.0001). Median progression-free survival was 2.4 months in patients showing EGFR promoter methylated tumours and 7.4 months for those who had EGFR promoter unmethylated tumours (P<0.0001; Figure 1). Median overall survival was 6.1 months in patients showing EGFR promoter methylated tumours and 17.8 months for those who had EGFR promoter unmethylated tumours (P<0.0001; Figure 2). CONCLUSION:EGFR promoter hypermethylation, after confirmation in larger data set, may represent a valuable asset in further studies investigating EGFR as a therapeutic target in colorectal cancer.

Molecular detection of epidermal growth factor receptor in colorectal cancer: does it still make sense?

AIM

The aim of the study was to detect and compare the epidermal growth factor receptor (EGFr) content using different methods, to establish whether the quantitative detection and functional study of EGFr in colorectal cancer, using methods other than immunohistochemistry (IHC), are appropriate.

METHOD

Analysis of EGFr by IHC was performed in 230 colorectal cancer patients using monoclonal anti-EGFr. Total and activated EGFr (pY1068) contents were determined in 92 patients and real-time PCR, to determine the level of EGFr messenger RNA, was carried out in 60 patients.

RESULTS

There was no association between EGFr IHC groups and the mean total EGFr levels measured using ELISA.

CONCLUSION

The study shows that the results of different EGFr detection methods do not correlate with each other. Hence, the real role of EGFr in colorectal cancer remains unsettled. Clinically, the receptor itself does not seem to be important and it would be better to focus on EGFr signalling in downstream pathways.

Aberrant expression of OX1 receptors for orexins in colon cancers and liver metastases: an openable gate to apoptosis

Resistance to apoptosis is a recurrent theme in colon cancer. We have shown previously that the 7-transmembrane spanning receptor OX1R for orexins promotes robust apoptosis in the human colon cancer cell line HT29 through an entirely novel mechanism involving phosphorylation of tyrosine-based motifs in OX1R. Here, we investigated the status of OX1R in a large series of human colorectal tumors and hepatic metastases. All primary colorectal tumors regardless of their localization and Duke's stages and all hepatic metastases tested expressed OX1R mRNA and/or protein. In sharp contrast, adjacent normal colonocytes or hepatocytes as well as control normal tissues were negative. Next, we showed that nine human colon cancer cell lines established from primary tumors or metastases expressed OX1R mRNA and underwent important apoptosis on orexin-A challenge. Most interestingly, orexin-A also promoted robust apoptosis in cells that are resistant to the most commonly used drug in colon cancer chemotherapy, 5-fluorouracil. When human colon cancer cells were xenografted in nude mice, orexin-A administered at day 0 strongly slowed the tumor growth and even reversed the development of established tumors when administered 7 days after cell inoculation. Orexin-A also acts by promoting tumor apoptosis in vivo because caspase-3 is activated in tumors on orexin treatment of nude mice. These findings support that OX1R is an Achilles heel of colon cancers, even after metastasis or chemoresistance. They suggest that OX1R agonists might be novel candidates for colon cancer therapy.

Heterogeneity in primary tumors and corresponding metastases: could it provide us with any hints to personalize cancer therapy?

Interpatient variability in response to anticancer drugs is associated with different clinical outcomes, which is partially owing to the individual differences among patients. Many investigators have hoped that tumor heterogeneity would help to reveal the underlying mechanism of interpatient variability in response to anticancer therapy. Numerous studies have demonstrated the presence of intratumor heterogeneity and the heterogeneity in primary tumors and corresponding metastases in a wide range of tumors at different levels and have indicated that the heterogeneity might make sense as a potential determinant of anticancer therapy response. This article discusses tumor heterogeneity, focusing on the heterogeneity in primary tumors and corresponding metastases as well as the effect on anticancer therapy response. Furthermore, an idea of tumor-site-based personalized cancer therapy for patients with metastatic malignancies was hypothesized, and a strategy using a patient-derived tumor tissue xenograft model to realize this idea is also proposed in this article.

Predictive markers of colorectal cancer liver metastases

Liver metastases are the most common site of distant failure after curative resection of colorectal cancer and a source of significant cancer-related morbidity and mortality. Currently, imaging and conventional histopathologic features, such as T-stage and N-stage, are used by clinicians to inform prognosis and guide adjuvant treatment to reduce the risk of developing distant metastases. However, these tools only have a moderate ability to predict the development of liver metastases. Novel methods, including the detection of circulating tumor cells and carcinoembryonic antigens in serum, have been developed, and their prognostic and predictive characteristics have been assessed. In addition, several molecular and genetic markers in the primary tumor have been studied. Unfortunately, these studies are often small and their results have been mixed, yielding no consistent sets of externally validated predictors of colorectal liver metastases. For widespread clinical relevance, future tests need to be independently carried out on large independent patient samples.

Time-resolved fluorescence resonance energy transfer (TR-FRET) to analyze the disruption of EGFR/HER2 dimers: a new method to evaluate the efficiency of targeted therapy using monoclonal antibodies

In oncology, simultaneous inhibition of epidermal growth factor receptor (EGFR) and HER2 by monoclonal antibodies (mAbs) is an efficient therapeutic strategy but the underlying mechanisms are not fully understood. Here, we describe a time-resolved fluorescence resonance energy transfer (TR-FRET) method to quantify EGFR/HER2 heterodimers on cell surface to shed some light on the mechanism of such therapies. First, we tested this antibody-based TR-FRET assay in NIH/3T3 cell lines that express EGFR and/or HER2 and in various tumor cell lines. Then, we used the antibody-based TR-FRET assay to evaluate in vitro the effect of different targeted therapies on EGFR/HER2 heterodimers in the ovarian carcinoma cell line SKOV-3. A simultaneous incubation with Cetuximab (anti-EGFR) and Trastuzumab (anti-HER2) disturbed EGFR/HER2 heterodimers resulting in a 72% reduction. Cetuximab, Trastuzumab or Pertuzumab (anti-HER2) alone induced a 48, 44, or 24% reduction, respectively. In contrast, the tyrosine kinase inhibitors Erlotinib and Lapatinib had very little effect on EGFR/HER2 dimers concentration. In vivo, the combination of Cetuximab and Trastuzumab showed a better therapeutic effect (median survival and percentage of tumor-free mice) than the single mAbs. These results suggest a correlation between the extent of the mAb-induced EGFR/HER2 heterodimer reduction and the efficacy of such mAbs in targeted therapies. In conclusion, quantifying EGFR/HER2 heterodimers using our antibody-based TR-FRET assay may represent a useful method to predict the efficacy and explain the mechanisms of action of therapeutic mAbs, in addition to other commonly used techniques that focus on antibody-dependent cellular cytotoxicity, phosphorylation, and cell proliferation.

Time-resolved fluorescence resonance energy transfer (TR-FRET) to analyze the disruption of EGFR/HER2 dimers: a new method to evaluate the efficiency of targeted therapy using monoclonal antibodies

In oncology, simultaneous inhibition of epidermal growth factor receptor (EGFR) and HER2 by monoclonal antibodies (mAbs) is an efficient therapeutic strategy but the underlying mechanisms are not fully understood. Here, we describe a time-resolved fluorescence resonance energy transfer (TR-FRET) method to quantify EGFR/HER2 heterodimers on cell surface to shed some light on the mechanism of such therapies. First, we tested this antibody-based TR-FRET assay in NIH/3T3 cell lines that express EGFR and/or HER2 and in various tumor cell lines. Then, we used the antibody-based TR-FRET assay to evaluate in vitro the effect of different targeted therapies on EGFR/HER2 heterodimers in the ovarian carcinoma cell line SKOV-3. A simultaneous incubation with Cetuximab (anti-EGFR) and Trastuzumab (anti-HER2) disturbed EGFR/HER2 heterodimers resulting in a 72% reduction. Cetuximab, Trastuzumab or Pertuzumab (anti-HER2) alone induced a 48, 44, or 24% reduction, respectively. In contrast, the tyrosine kinase inhibitors Erlotinib and Lapatinib had very little effect on EGFR/HER2 dimers concentration. In vivo, the combination of Cetuximab and Trastuzumab showed a better therapeutic effect (median survival and percentage of tumor-free mice) than the single mAbs. These results suggest a correlation between the extent of the mAb-induced EGFR/HER2 heterodimer reduction and the efficacy of such mAbs in targeted therapies. In conclusion, quantifying EGFR/HER2 heterodimers using our antibody-based TR-FRET assay may represent a useful method to predict the efficacy and explain the mechanisms of action of therapeutic mAbs, in addition to other commonly used techniques that focus on antibody-dependent cellular cytotoxicity, phosphorylation, and cell proliferation.

MEK1/2 inhibitors AS703026 and AZD6244 may be potential therapies for KRAS mutated colorectal cancer that is resistant to EGFR monoclonal antibody therapy

Epidermal growth factor receptor (EGFR) monoclonal antibodies (mAb) are used widely to treat metastatic colorectal cancer (mCRC) patients, but it is now clear that patients harboring K-ras mutation are resistant to EGFR mAbs such as cetuximab (Erbitux) and panitumumab (Vectibix). For this reason, current recommendations for patient care involve diagnosing the K-ras mutational status of patients prior to EGFR mAb therapy. In this study, we investigated the ability of two MEK inhibitors currently in clinical trials, AS703026 and AZD6244, to address the challenge posed by the resistance of K-ras mutated colorectal cancers to EGFR mAb. AS703026 and AZD6244 were tested in various cell-based assays and tumor xenograft studies, focusing on isogenic human colorectal tumor cell lines that expressed only WT or mutant K-Ras (D-WT or D-MUT). The EGFR mAb cetuximab inhibited the Ras-ERK pathway and proliferation of D-WT cells in vitro and in vivo, but it did not inhibit proliferation of D-MUT cells in either setting. In contrast, AS703026 and AZD6244 effectively inhibited the growth of D-MUT cells in vitro and in vivo by specific inhibition of the key MEK downstream target kinase ERK. Inhibition of MEK by AS703026 or AZD6244 also suppressed cetuximab-resistant colorectal cancer cells attributed to K-ras mutation both in vitro and in vivo. Our findings offer proof-of-concept for the use of MEK inhibitors as an effective therapy in K-ras mutated CRC.

Practical and molecular evaluation of colorectal cancer: new roles for the pathologist in the era of targeted therapy

CONTEXT

Colorectal cancer is the third most common cancer and the fourth most common cause of cancer death worldwide. Patient cases are discussed in multidisciplinary meetings to decide on the best management on an individual basis. Until recently, the main task of the pathologist in such teams was to provide clinically useful reports comprising staging of colorectal cancer in surgical specimens. The advent of total mesorectal excision and the application of anti-epidermal growth factor receptor (EGFR)-targeted therapies for selected patients with metastasized colorectal cancer have changed the role of the pathologist.

OBJECTIVES

To present the traditional role of the pathologist in the multidisciplinary team treating patients with colorectal cancer, to address the technique of total mesorectal excision and its implications for the evaluation of surgical specimens, to offer background information on the various EGFR-targeted therapies, and to review the currently investigated tissue biomarkers assumed to be predictive for efficacy of such therapies, with a focus on the role of the pathologist in determining the status of such biomarkers in individual tumors.

DATA SOURCES

This article is based on selected articles pertaining to biopsy evaluation of colorectal carcinoma and reviews of EGFR-targeted therapies for this cancer. All references are accessible via the PubMed database (US National Library of Medicine and the National Institutes of Health).

CONCLUSIONS

Pathologists play an increasingly important role in the diagnosis and management of colorectal cancer because of the advent of new surgical techniques and of targeted therapies. It is expected that this role will increase further in the near future.

Colorectal cancer in review: the role of the EGFR pathway

IMPORTANCE OF THE FIELD

The overexpression of EGFR has been documented in 30-90% of cases of advanced colorectal cancer (CRC). An increased understanding of the EGFR pathway in CRC has paved the way for the development of other targeted agents to augment therapeutic efficacy as well as for efforts to circumvent tumor resistance to therapy.

AREAS COVERED IN THIS REVIEW

Our aim is to discuss the recent progress in the role of the EGFR pathway, the status of anti-EGFR therapeutic agents currently in use and the rationale for the development of novel agents that work along the pathway for the treatment of CRC.

WHAT THE READER WILL GAIN

The readers will learn about the development and evolution of mAbs directed against EGFR as well as tyrosine kinase inhibitors in the management of CRC patients. In the same vein, determination of optimal dosing and better methods of defining those subsets of patients most likely to benefit will be discussed.

TAKE HOME MESSAGE

All these data must encourage clinicians and basic researches to continue in their efforts to untangle the network behind EGFR and try to focus all that effort towards improving patient's quality of life as well as survival.

Epidermal growth factor receptor inhibitors in cancer treatment: advances, challenges and opportunities

Aberrant expression of the epidermal growth factor receptor (EGFR) system has been reported in a wide range of epithelial cancers. In some studies, this has also been associated with a poor prognosis and resistance to the conventional forms of therapies. These discoveries have led to the strategic development of several kinds of EGFR inhibitors, five of which have gained US Food and Drug Administration approval for the treatment of patients with non-small-cell lung cancer (gefitinib and erlotinib), metastatic colorectal cancer (cetuximab and panitumumab), head and neck (cetuximab), pancreatic cancer (erlotinib) and breast (lapatinib) cancer. Despite these advances and recent studies on the predictive value of activating EGFR mutation and KRAS mutations with response in non-small-cell lung cancer and colon cancer patients, there is currently no reliable predictive marker for response to therapy with the anti-EGFR monoclonal antibodies cetuximab and panitumumab or the small molecule EGFR tyrosine kinase inhibitors gefitinib and erlotinib. In particular, there has been no clear association between the expression of EGFR, determined by the US Food and Drug Administration-approved EGFR PharmDX kit, and response to the EGFR inhibitors. Here, we discuss some of the controversial data and explanatory factors as well as future studies for the establishment of more reliable markers for response to therapy with EGFR inhibitors. Such investigations should lead to the selection of a more specific subpopulation of cancer patients who benefit from therapy with EGFR inhibitors, but equally to spare those who will receive no benefit or a detrimental effect from such biological agents.

High epidermal growth factor receptor expression in metastatic colorectal cancer lymph nodes may be more prognostic of poor survival than in primary tumor

OBJECTIVES

High epidermal growth factor receptor (EGFR) expression in the primary tumor predicts poor survival in colorectal cancer. However, EGFR expression may be discordant in primary tumor versus nodal or distant metastasis. We evaluated prognostic values of high EGFR expression in nodal metastasis versus primary tumor tissue.

METHODS

Tissue microarrays from 94 surgically resected colorectal primary tumors were analyzed for EGFR expression using immunohistochemistry along with 49 paired positive metastatic nodes and 19 distant metastases. Proportional odds regression and log-rank tests described the association of tumor stage and survival with EGFR, dichotomized to low expression (0, 1) versus high expression (2, 3).

RESULTS

High EGFR expression rates in the primary tumor, metastatic lymph node and distant metastases were 18%, 24%, and 21%, respectively. The concordance rate was 71% for stage III/IV patients. High EGFR expression in primary tumor was associated with higher tumor stage (odds ratio 4.3, P = 0.005) and thus predicted poor survival (P = 0.046). High EGFR expression in the primary tumor was not associated with survival in patients with stage III or IV disease, whereas high EGFR expression in metastatic lymph nodes was associated with relatively poor survival (P = 0.005), for both stage III (P = 0.002) and stage IV patients (P = 0.014). Concordant high EGFR expression in primary tumor and lymph nodes conferred added risk of death (P = 0.003), conversely, concordant EGFR-negative primary tumor and lymph node was protective (P = 0.097).

CONCLUSIONS

EGFR expression may be discordant among primary, nodes, and metastases in colorectal cancer. High EGFR expressions in metastatic lymph nodes seem to be more accurate in predicting survival than in primary or metastatic tissues.

Imaging of EGFR expression in murine xenografts using site-specifically labelled anti-EGFR 111In-DOTA-Z EGFR:2377 Affibody molecule: aspect of the injected tracer amount

INTRODUCTION

Overexpression of epidermal growth factor receptor (EGFR) is a prognostic and predictive biomarker in a number of malignant tumours. Radionuclide molecular imaging of EGFR expression in cancer could influence patient management. However, EGFR expression in normal tissues might complicate in vivo imaging. The aim of this study was to evaluate if optimization of the injected protein dose might improve imaging of EGFR expression in tumours using a novel EGFR-targeting protein, the DOTA-Z(EGFR:2377) Affibody molecule.

METHODS

An anti-EGFR Affibody molecule, Z(EGFR:2377), was labelled with (111)In via the DOTA chelator site-specifically conjugated to a C-terminal cysteine. The affinity of DOTA-Z(EGFR:2377) for murine and human EGFR was measured by surface plasmon resonance. The cellular processing of (111)In-DOTA-Z(EGFR:2377) was evaluated in vitro. The biodistribution of radiolabelled Affibody molecules injected in a broad range of injected Affibody protein doses was evaluated in mice bearing EGFR-expressing A431 xenografts.

RESULTS

Site-specific coupling of DOTA provided a uniform conjugate possessing equal affinity for human and murine EGFR. The internalization of (111)In-DOTA-Z(EGFR:2377) by A431 cells was slow. In vivo, the conjugate accumulated specifically in xenografts and in EGFR-expressing tissues. The curve representing the dependence of tumour uptake on the injected Affibody protein dose was bell-shaped. The highest specific radioactivity (lowest injected protein dose) provided a suboptimal tumour-to-blood ratio. The results of the biodistribution study were confirmed by gamma-camera imaging.

CONCLUSION

The (111)In-DOTA-Z(EGFR:2377) Affibody molecule is a promising tracer for radionuclide molecular imaging of EGFR expression in malignant tumours. Careful optimization of protein dose is required for high-contrast imaging of EGFR expression in vivo.

A phase II, multicenter study of cetuximab monotherapy in patients with refractory, metastatic colorectal carcinoma with absent epidermal growth factor receptor immunostaining

PURPOSE

To determine antitumor activity of cetuximab monotherapy in patients with refractory metastatic colorectal carcinoma (mCRC) with lack of specific membrane immunostaining for the epidermal growth factor receptor (EGFR).

PATIENTS AND METHODS

Patients had immunohistochemical (IHC)-determined mCRC with absent EGFR immunostaining that progressed after receiving at least one standard, fluoropyrimidine-containing chemotherapeutic regimen. Absent EGFR immunostaining was defined as the IHC absence of specific membrane staining in ≥500 cancer cells examined in well-preserved tissue. The study was performed prior to results of studies linking cetuximab sensitivity to K-ras mutation status. Patients received 400 mg/m(2) of intravenous (i.v.) cetuximab followed by once-weekly i.v. cetuximab 250 mg/m(2) until disease progression or unacceptable toxicity. Patients were evaluated for objective response at least every 6 weeks. Kaplan-Meier estimates were calculated for duration of response, time to progression (TTP), and overall survival (OS).

RESULTS

Seven (8.2%) of 85 mCRC patients whose tumors lacked EGFR immunostaining had major responses following cetuximab treatment. The median duration of response was 5.1 months. Median TTP and OS were 2.5 months and 10.0 months, respectively; the 1-year survival rate was 39.6%. The most frequently reported cetuximab-related adverse events were acneiform dermatitis, fatigue, headache, and dry skin.

CONCLUSION

Cetuximab monotherapy produces objective antitumor activity in patients with mCRC that does not express EGFR as determined by IHC. The activity and safety profiles of cetuximab monotherapy in mCRC lacking EGFR immunostaining are similar to previous observations in EGFR IHC-positive disease that was not selected based on K-ras mutation status.

Biomarkers predicting clinical outcome of epidermal growth factor receptor-targeted therapy in metastatic colorectal cancer

The monoclonal antibodies panitumumab and cetuximab that target the epidermal growth factor receptor (EGFR) have expanded the range of treatment options for metastatic colorectal cancer. Initial evaluation of these agents as monotherapy in patients with EGFR-expressing chemotherapy-refractory tumors yielded response rates of approximately 10%. The realization that detection of positive EGFR expression by immunostaining does not reliably predict clinical outcome of EGFR-targeted treatment has led to an intense search for alternative predictive biomarkers. Oncogenic activation of signaling pathways downstream of the EGFR, such as mutation of KRAS, BRAF, or PIK3CA oncogenes, or inactivation of the PTEN tumor suppressor gene is central to the progression of colorectal cancer. Tumor KRAS mutations, which may be present in 35%-45% of patients with colorectal cancer, have emerged as an important predictive marker of resistance to panitumumab or cetuximab treatment. In addition, among colorectal tumors carrying wild-type KRAS, mutation of BRAF or PIK3CA or loss of PTEN expression may be associated with resistance to EGFR-targeted monoclonal antibody treatment, although these additional biomarkers require further validation before incorporation into clinical practice. Additional knowledge of the molecular basis for sensitivity or resistance to EGFR-targeted monoclonal antibodies will allow the development of new treatment algorithms to identify patients who are most likely to respond to treatment and could also provide rationale for combining therapies to overcome primary resistance. The use of KRAS mutations as a selection biomarker for anti-EGFR monoclonal antibody (eg, panitumumab or cetuximab) treatment is the first major step toward individualized treatment for patients with metastatic colorectal cancer.

ErbB family immunohistochemical expression in colorectal cancer patients with higher risk of recurrence after radical surgery

PURPOSE

Investigate ErbB family expression in colorectal cancer patients with higher risk of recurrence after surgical treatment.

METHODS

We studied 109 individuals with high risk stage II and stage III patients submitted to radical surgery. ErbB expression was assessed by tissue microarray technique.

RESULTS

The immunohistochemical expression was considered positive for EGFR, ErbB2, ErbB3, ErbB4 membrane, and ErbB4 cytoplasmic in respectively 57.8%, 8.3%, 69.7%, 11%, and 19.3% of patients. ErbB3 negative expression was associated with lymphovascular invasion. EGFR, ErbB2, and cytoplasmic ErbB4 expression was not associated with prognosis. Membranous positive ErbB4 expression was an independent prognostic factor for recurrence. ErbB3 negative expression was an independent prognostic factor for recurrence and survival in the multivariate analysis.

CONCLUSIONS

The immunohistochemical expression of ErbB3 and ErbB4 may identify a subgroup with stage II and III colorectal cancer at higher risk of recurrence.

Improving disease control in advanced colorectal cancer: Panitumumab and cetuximab

Colorectal cancer remains a major public health concern in Europe and North America. It is responsible for one million new cases and half a million deaths per year worldwide. During the past few years new effective treatments have evolved improving the outcome of patients with this disease. Several alternatives are currently available for advanced colorectal cancer patients including different chemotherapeutic regimens (fluoropyrimidines, irinotecan and oxaliplatin) and targeted therapies such as bevacizumab and cetuximab. Different combinations achieve a median survival of over 2 years. Intense efforts focus on identifying agents targeting growth factor receptors, signal transduction pathways or angiogenesis mediators. One of the last available drugs for the management of advanced colorectal cancer is panitumumab, a well-tolerated and effective anti-EGFR monoclonal antibody approved as a single agent in chemotherapy refractory patients. We discuss the current evidence supporting panitumumab for metastatic colorectal cancer treatment, potential predictive biomarkers and ongoing clinical trials with different combinations including panitumumab.

Epidermal growth factor receptor expression discrepancies in metastatic colorectal cancer patients treated with cetuximab plus irinotecan-based chemotherapy refractory to irinotecan and oxaliplatin

PURPOSE

This study was designed to evaluate the efficacy and safety of cetuximab plus irinotecan-based therapy in metastatic colorectal cancer refractory to irinotecan and oxaliplatin. In addition, discrepancies in the expression of epidermal growth factor receptor were examined by immunohistochemistry using two different antibodies.

METHODS

The records of patients with metastatic colorectal cancer who were heavily pretreated with irinotecan and oxaliplatin and subsequently received cetuximab plus irinotecan-based therapy were reviewed. Differences in the expression of epidermal growth factor receptor detected by the PharmDx antibody and the clone H11 antibody in these patients were compared.

RESULTS

Between February 2005 and August 2007, 52 patients were treated; median age was 53.5 years. The confirmed overall response rate was 30.8 percent, and the disease control rate was 67.3 percent. Median time to progression was 3.1 months, and median overall survival was 8.1 months. Of the 27 patients evaluable for epidermal growth factor receptor status, epidermal growth factor receptor expression was positive in 12 patients (44.4 percent) using the clone H11 antibody test and in 26 patients (96.3 percent) with the PharmDx kit.

CONCLUSION

Cetuximab plus irinotecan-based therapy showed promising antitumor activity even in patients with metastatic colorectal cancer refractory to irinotecan and oxaliplatin. In addition, discrepancies in the expression of the epidermal growth factor receptor detected by the clone H11 antibody and the PharmDx kit were observed.

PTEN expression and KRAS mutations on primary tumors and metastases in the prediction of benefit from cetuximab plus irinotecan for patients with metastatic colorectal cancer

PURPOSE

PTEN, AKT, and KRAS are epidermal growth factor receptor (EGFR) downstream regulators. KRAS mutations confer resistance to cetuximab. This retrospective study investigated the role of PTEN loss, AKT phosphorylation, and KRAS mutations on the activity of cetuximab plus irinotecan in patients with metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

A cohort of patients with irinotecan-refractory mCRC who were treated with cetuximab plus irinotecan was tested for PTEN immunoreactivity (ie, immunohistochemistry; IHC), pAKT IHC, and KRAS mutations. Analyses were performed both on primary tumors and on related metastases, and the association among IHC, mutational results, and treatment outcomes was investigated.

RESULTS

One-hundred two patients were eligible. Ninety-six primary tumors, 59 metastases, and 53 paired samples were available. Forty-nine primary tumors (58% of assessable samples) had a preserved PTEN expression (PTEN-positive), whereas 35 (40% of assessable samples) were pAKT-positive. Levels of concordance between primary tumors and metastases were 60%, 68%, and 95% for PTEN, pAKT, and KRAS, respectively. PTEN status on primary tumors and pAKT status both on primary tumors and on metastases did not predict response or progression-free survival (PFS). On metastases, 12 (36%) of 33 patients with PTEN-positive tumors were responders compared with one (5%) of 22 who had PTEN-negative tumors (P = .007). The median PFS of patients with PTEN-positive metastases was 4.7 months compared with 3.3 months for those with PTEN-negative metastases (hazard ratio [HR], 0.49; P = .005). Patients with PTEN-positive metastases and KRAS wild type had longer PFS compared with other patients (5.5 months v 3.8 months; HR, 0.42; P = .001).

CONCLUSION

PTEN loss in metastases may be predictive of resistance to cetuximab plus irinotecan. The combination of PTEN IHC and KRAS mutational analyses could help to identify a subgroup of patients with mCRC who have higher chances of benefiting from EGFR inhibition.

Differing deregulation of EGFR and downstream proteins in primary colorectal cancer and related metastatic sites may be clinically relevant

Cetuximab and panitumumab efficacy in metastatic colorectal cancer (mCRC) may be influenced by EGFR gene status and/or deregulation of its downstream signalling proteins detected in primary tumour. However, metastasis might have different molecular patterns with respect to primary tumour, possibly affecting the prediction of EGFR-targeted therapy efficacy. We analysed primary tumour and metastasis in 38 mCRC patients. Twelve cases were cetuximab/panitumumab treated. EGFR gene status and protein expression were investigated through fluorescent in situ hybridisation and immunohistochemistry (IHC), K-Ras/BRAF mutations by sequencing and PTEN expression by IHC. We observed EGFR gene deregulation in 25 out of 36 primary tumours and 29 out of 36 metastases, K-Ras mutations in 16 out of 37 cancers and in 15 out of 37 metastases, BRAF mutations in 2 out of 36 cancers and 2 out of 36 metastases and PTEN loss in 8 out of 38 cancers and 12 out of 38 metastases. For the first time in literature, we show that primary colorectal cancer and paired metastasis may exhibit difference with respect to EGFR pathway deregulation mechanisms possibly implying a different response to cetuximab or panitumumab treatment. The investigation of treated patients confirms this hypothesis. We therefore suggest that the analysis of metastatic lesion should be considered in patient management as well as in designing future clinical trials aimed to investigate the effect of anti-EGFR monoclonal antibodies in the treatment of mCRC.

Immunohistochemical detection of receptor tyrosine kinases c-kit, EGF-R, and PDGF-R in colorectal adenocarcinomas

PURPOSE

The selective inhibition of tyrosine kinases is a promising strategy in the treatment of several human malignancies. This study aimed to clarify expression patterns of therapeutically addressable receptor tyrosine kinases in colorectal cancer.

MATERIALS AND METHODS

In this study, we used tissue arrays to analyze 263 specimen of colorectal carcinoma for the expression of the tyrosine kinases c-kit (CD117), epidermal growth factor receptor (EGF-R), and platelet-derived growth factor receptor (PDGF-R). Staining patterns were then correlated with tumor stage and survival.

RESULTS

Five tumors (1.9%) showed a strong expression of c-kit (CD117), while in 40 samples (15.2%), a weak/intermediate expression was observed. Positive staining did not correlate with histopathological parameters although a trend toward a better survival of c-kit-positive patients was observed. No positivity for PDGF-R was observed in 263 samples of colorectal carcinomas. Positive EGF-R expression was identified in 39 cases (15.2%), whereas 218 samples (84.8%) stained negative.

CONCLUSIONS

Our study confirms that expression of the tyrosine kinases c-kit and PDGF-R are rare in colorectal carcinomas and do not correlate with tumor stage.

Toward an individualizing therapy for colorectal cancer: the example of the anti-EGFR monoclonal antibodies

Anti-EGF receptor (EGFR) antibodies (cetuximab and panitumumab) have been demonstrated to be efficient in the treatment of metastatic colorectal cancer. However, these costly and potentially toxic treatments are active in a subset of patients, which renders necessary the identification of factors that are able to better define which patients will benefit from these treatments. Advances in the understanding of signaling pathways inhibited by these targeted therapies led to the identification of KRAS mutations as a strong predictor of resistance to anti-EGFR therapies. Other molecular markers, which are involved in the EGF signaling pathway or in the antibody dependent cell-mediated cytotoxicity-related anti-tumor effect of these anti-EGFR therapies, are also interesting and will have to be evaluated in future clinical trials.

Immunohistochemical expression of EGFR in colorectal carcinoma correlates with high but not low level gene amplification, as demonstrated by CISH

AIM

To assess and compare immunohistochemical expression of epidermal growth factor receptor (EGFR) with gene amplification as demonstrated by chromogenic in situ hybridisation (CISH), in colorectal adenocarcinoma.

METHODS

Sections from 100 consecutive colorectal cancer resection specimens were stained for EGFR using immunohistochemistry and CISH. Immunohistochemical assessment was independently performed at two laboratories, using the same antibody and protocols.

RESULTS

With immunohistochemistry, strong circumferential membrane staining (3+ staining) was demonstrated in only 5% of cases, and this was only focal in three of five cases. At one laboratory, weak or incomplete staining (1+ or 2+) was observed in five further cases (5%), which had been negative at the other laboratory. CISH demonstrated high level gene amplification (>10 copies/nucleus) in the same five cases which had demonstrated 3+ staining with immunohistochemistry, and in those cases where the staining was focal, the amplification was demonstrated in the same foci of the tumour. Five further cases (5%) had low level amplification (5-10 copies per nucleus); these cases did not exhibit significant positive staining with immunohistochemistry. All the cases which demonstrated gene amplification (high or low level) arose in the distal colon. There was no correlation between gene amplification status and a variety of other variables, including stage at diagnosis, mucinous differentiation, neuroendocrine differentiation, or loss of expression of mismatch repair proteins.

CONCLUSIONS

Immunohistochemical expression of EGFR is variable between laboratories, even using standardised protocols. 3+ staining is predictive of high level gene amplification, but correlates very poorly with low level amplification, which may still be clinically significant. In some cases gene amplification was only focal, offering a potential explanation for poor response to targeted therapy in patients with EGFR positive tumours.

Clinical biomarkers of kinase activity: examples from EGFR inhibition trials

INTRODUCTION

Tumor response and duration of patient survival after treatment with inhibitors of the epidermal growth factor receptor (EGFR) varies considerably between different kinds of EGFR inhibitors, different combination schedules, but also between individual patients.

DISCUSSION

Development and introduction of biomarkers into clinical practice is necessary to predict treatment response and thereby to individualize cancer therapy. Due to specific interactions of EGFR inhibitors with biological effects of irradiation, biomarkers are expected to differ for radiation oncology compared to application of the drugs alone or within chemotherapy treatment schedules and therefore need to be established and tested separately.

OBJECTIVES

The review summarizes the current status of potential predictors for the effect of EGFR inhibitors used as single agents or in combination with chemotherapy.

CONCLUSION

Based on this knowledge and on preclinical radiotherapy data, candidate biomarkers and further research strategies for radiation oncology are discussed.