Cetuximab for the treatment of colorectal cancer

Inhibition of N-linked glycosylation disrupts receptor tyrosine kinase signaling in tumor cells

Receptor tyrosine kinases (RTK) are therapeutic targets for the treatment of malignancy. However, tumor cells develop resistance to targeted therapies through the activation of parallel signaling cascades. Recent evidence has shown that redundant or compensatory survival signals responsible for resistance are initiated by nontargeted glycoprotein RTKs coexpressed by the cell. We hypothesized that disrupting specific functions of the posttranslational machinery of the secretory pathway would be an effective strategy to target both primary and redundant RTK signaling. Using the N-linked glycosylation inhibitor, tunicamycin, we show that expression levels of several RTKS (EGFR, ErbB2, ErbB3, and IGF-IR) are exquisitely sensitive to inhibition of N-linked glycosylation. Disrupting this synthetic process reduces both cellular protein levels and receptor activity in tumor cells through retention of the receptors in the endoplasmic reticulum/Golgi compartments. Using U251 glioma and BXPC3 pancreatic adenocarcinoma cell lines, two cell lines resistant to epidermal growth factor receptor-targeted therapies, we show that inhibiting N-linked glycosylation markedly reduces RTK signaling through Akt and radiosensitizes tumor cells. In comparison, experiments in nontransformed cells showed neither a reduction in RTK-dependent signaling nor an enhancement in radiosensitivity, suggesting the potential for a therapeutic ratio between tumors and normal tissues. This study provides evidence that enzymatic steps regulating N-linked glycosylation are novel targets for developing approaches to sensitize tumor cells to cytotoxic therapies.

Management of colorectal cancer: a role for genetics in prevention and treatment?

Colorectal cancer remains one of the most common cancers in the Western world and amongst the top three causes of cancer morbidity and death. Cancer is caused by genetic mutations, but currently there is little use of genetic information in the clinic with the exception of establishing germline mutations for the uncommon predisposing syndromes. Rapid advances in technologies allowing high throughput analysis of germline and somatic mutations raises the possibility that genetics will find a major role in the clinic distinguishing individuals at low to high risk of cancer, allowing early intervention and stratification of cancers based on mutational pathways for therapeutic interventions. In the future, this will lead to treatment regimes tailored to the individuals and their tumor. Here, we summarize the genetics underlying colorectal cancer and the future role of genetics in prevention, diagnosis, classification and treatment.

Paul Ehrlich's magic bullet concept: 100 years of progress

Exceptional advances in molecular biology and genetic research have expedited cancer drug development tremendously. The declared paradigm is the development of 'personalized and tailored drugs' that precisely target the specific molecular defects of a cancer patient. It is therefore appropriate to revisit the intellectual foundations of the development of such agents, as many have shown great clinical success. One hundred years ago, Paul Ehrlich, the founder of chemotherapy, received the Nobel Prize for Physiology or Medicine. His postulate of creating 'magic bullets' for use in the fight against human diseases inspired generations of scientists to devise powerful molecular cancer therapeutics.

Bevacizumab plus FOLFIRI or FOLFOX as third-line or later treatment in patients with metastatic colorectal cancer after failure of 5-fluorouracil, irinotecan, and oxaliplatin: a retrospective analysis

Bevacizumab, a monoclonal antibody against vascular endothelial growth factor, has shown clinical activity in metastatic colorectal cancer patients when used as either a first-line or second-line treatment. Here, we evaluated the efficacy and safety of bevacizumab plus FOLFIRI (irinotecan, 5-fluorouracil, and leucovorin) or FOLFOX (oxaliplatin, 5-fluorouracil, and leucovorin) in metastatic colorectal cancer cases after failure to FOLFIRI and FOLFOX. Between October 2004 and February 2007, the data on 42 patients with metastatic colorectal cancer after failure of FOLFIRI and FOLFOX were reviewed retrospectively. All patients were treated with bevacizumab plus FOLFIRI or FOLFOX. The median patient age was 57.0 years. The ECOG performance status was 0 or 1 in 27 patients (64.3%). The number of previous chemotherapy regimens was >/=3 in 35 patients (83.3%). Thirty-nine patients were evaluable for response. Four patients had partial responses (PRs) and no patient had a complete response (CR), giving an overall response rate of 9.5%. Twenty-two patients (52.4%) had stable disease and 13 patients (31.0%) showed progressive disease. With a median follow-up time of 12.9 months (range 1.0-30.0 months), the median progression-free survival time and the median overall survival time were 5.3 and 9.5 months, respectively. Grade 3 or 4 neutropenia developed in 18 patients (42.9%), including febrile neutropenia in 4 patients (9.5%). Common non-hematologic toxicities were fatigue (21.4%), neuropathy (21.4%), and mucositis (21.4%). Grade 2 or 3 hypertension occurred in 4 patients (9.6%), and grade 1 or 2 proteinuria was seen in 16 patients (38.1%). The frequencies of adverse events related BV, such as bleeding, thrombosis, and gastrointestinal perforation, were within the ranges of previous reports. However, there were no treatment-related deaths. The combination of bevacizumab plus FOLFIRI or FOLFOX showed modest activity and was relatively tolerable in patients with metastatic colorectal cancer refractory to both FOLFIRI and FOLFOX.

High efficiency reconstitution of a human-mouse chimeric Fab of CAb-1 antibody specific to human colon cancer

Monoclonal antibody (mAb) has been widely applied in the treatment of human diseases, especially in malignant tumours. However, most antibodies produced in mouse by hybridoma technology might induce severe human anti-mouse reactions. We had reported a murine mAb CAb-1 of therapeutic interest for its specifically binding to a cell surface glycoprotein of human colon cancer. Here, we attempted to generate a reconstituted human-mouse chimeric Fab (cFab) of CAb-1 in vitro to reduce its antigenicity and increase its capacity of penetration. First, the genes of heavy and light chain variable region (VH, VL) of CAb-1 were cloned. Then, the chimeric light chain (cL) and Fd (cFd) were constructed and expressed in Escherichia coli. Finally, the reconstituted cFab was obtained by gradient dialysis of the mixture of cFd and cL. SDS-PAGE and western blot analysis showed the reconstituted cFab with a recovery rate of 70.2% when the initial total concentration of cL and cFd proteins to be 100 microg/ml. The reconstituted cFab maintained the affinity and specificity to colon cancer cells compared with its parental antibody as determined by immunostaining analysis, FACS and ELISA. Our results established a foundation for further application of the cFab in diagnosis and treatment of colon cancer.

EPIC: Phase III Trial of Cetuximab Plus Irinotecan After Fluoropyrimidine and Oxaliplatin Failure in Patients With Metastatic Colorectal Cancer

Purpose

To determine whether adding cetuximab to irinotecan prolongs survival in patients with metastatic colorectal cancer (mCRC) previously treated with fluoropyrimidine and oxaliplatin.

Patients and Methods

This multicenter, open-label, phase III study randomly assigned 1,298 patients with epidermal growth factor receptor–expressing mCRC who had experienced first-line fluoropyrimidine and oxaliplatin treatment failure to cetuximab (400 mg/m2day 1 followed by 250 mg/m2weekly) plus irinotecan (350 mg/m2every 3 weeks) or irinotecan alone. Primary end point was overall survival (OS); secondary end points included progression-free survival (PFS), response rate (RR), and quality of life (QOL).

Results

Median OS was comparable between treatments: 10.7 months (95% CI, 9.6 to 11.3) with cetuximab/irinotecan and 10.0 months (95% CI, 9.1 to 11.3) with irinotecan alone (hazard ratio [HR], 0.975; 95% CI, 0.854 to 1.114; P = .71). This lack of difference may have been due to post-trial therapy: 46.9% of patients assigned to irinotecan eventually received cetuximab (87.2% of those who did, received it with irinotecan). Cetuximab added to irinotecan significantly improved PFS (median, 4.0 v 2.6 months; HR, 0.692; 95% CI, 0.617 to 0.776; P ≤ .0001) and RR (16.4% v 4.2%; P < .0001), and resulted in significantly better scores in the QOL analysis of global health status (P = .047). Cetuximab did not exacerbate toxicity, except for acneform rash, diarrhea, hypomagnesemia, and associated electrolyte imbalances. Neutropenia was the most common severe toxicity across treatment arms.

Conclusion

Cetuximab and irinotecan improved PFS and RR, and resulted in better QOL versus irinotecan alone. OS was similar between study groups, possibly influenced by the large number of patients in the irinotecan arm who received cetuximab and irinotecan poststudy.

Systemic treatment of colorectal cancer

Colorectal cancer is the fourth most common noncutaneous malignancy in the United States and the second most frequent cause of cancer-related death. Over the past 12 years, significant progress has been made in the systemic treatment of this malignant condition. Six new chemotherapeutic agents have been introduced, increasing median overall survival for patients with metastatic colorectal cancer from less than 9 months with no treatment to approximately 24 months. For patients with stage III (lymph node positive) colon cancer, an overall survival benefit for fluorouracil-based chemotherapy has been firmly established, and recent data have shown further efficacy for the inclusion of oxaliplatin in such adjuvant treatment programs. For patients with stage II colon cancer, the use of adjuvant chemotherapy remains controversial, but may be appropriate in a subset of individuals at higher risk for disease recurrence. Ongoing randomized clinical trials are evaluating how best to combine currently available therapies, while smaller studies are evaluating new agents, with the goal of continued progress in prolonging life among patients with metastatic colorectal cancer and increasing cure rates among those with resectable disease.

Where to position monoclonal antibodies in first-line treatment of advanced colorectal cancer

The treatment of metastatic colorectal cancer with modern cytotoxic agents in combination with monoclonal antibodies against vascular endothelial growth factor (VEGF) and the epidermal growth factor receptor (EGFR) has improved median overall survival from 6 months to almost 2 years. Uncertainty remains over the optimal chemotherapy combination and sequencing, and to which line of treatment monoclonal antibodies should be added. This article reviews the rationale and evidence for the use of monoclonal antibodies in the first-line treatment of metastatic colorectal cancer in both general and specific situations, and provides a perspective on how to position their use in contemporary practice.

A randomised phase III study on capecitabine, oxaliplatin and bevacizumab with or without cetuximab in first-line advanced colorectal cancer, the CAIRO2 study of the Dutch Colorectal Cancer Group (DCCG). An interim analysis of toxicity

BACKGROUND

Targeting the vascular endothelial growth factor or the epidermal growth factor receptor (EGFR) has shown efficacy in advanced colorectal cancer (ACC), but no data are available on the combination of these strategies with chemotherapy in the first-line treatment. The CAIRO2 study evaluates the effect of adding cetuximab, a chimeric mAb against EGFR, to capecitabine, oxaliplatin and bevacizumab in the first-line treatment of ACC.

PATIENTS AND METHODS

In all, 755 patients were randomly assigned between treatment with capecitabine, oxaliplatin and bevacizumab with or without cetuximab. The primary end point is progression-free survival. We here present the toxicity results in the first 400 patients that entered the study.

RESULTS

The incidence of overall grade 3-4 toxicity was significantly higher in arm B compared with arm A (81% versus 72%, P = 0.03). This difference is fully attributed to cetuximab-related skin toxicity. The addition of cetuximab did not result in an increase of gastrointestinal toxicity or treatment-related mortality.

CONCLUSIONS

The addition of cetuximab to capecitabine, oxaliplatin and bevacizumab in the first-line treatment of ACC appears to be safe and feasible. No excessive or unexpected toxicity in the cetuximab-containing treatment arm was observed.

Combined analysis of VEGF and EGFR predicts complete tumour response in rectal cancer treated with preoperative radiotherapy

The ability to predict complete pathologic response or sensitivity to radiation before treatment would have a significant impact on the selection of patients for preoperative radiotherapy or chemo-radiation therapy schedules. The aim of this study was to determine the value of epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), p53, Bcl-2 and apoptosis protease-activating factor-1 (APAF-1) as predictors of complete pathologic tumour regression in patients undergoing preoperative radiotherapy for advanced rectal cancer. Pretreatment tumour biopsies from predominantly cT3 patients undergoing a preoperative high-dose-rate brachytherapy protocol were immunostained for EGFR, VEGF, p53, Bcl-2 and APAF-1. Immunoreactivity was evaluated by three pathologists. Cut-off scores for tumour marker positivity were obtained by receiver-operating characteristic (ROC) curve analysis. The association of marker expression with complete pathologic response was analysed in univariate and multivariable analysis. Multi-marker phenotypes of the independent protein markers were evaluated. In multivariable analysis, loss of VEGF (P-value=0.009; odds ratio (OR) (95% CI)=0.24 (0.08–0.69)) and positive EGFR (P-value=0.01; OR (95% CI)=3.82 (1.37–10.6)) both demonstrated independent predictive value for complete pathologic response. The odds of complete response were 12.8 for the multi-marker combination of VEGF-negative and EGFR-positive tumours. Of the 34 EGFR-negative- and VEGF-positive cases, 32 (94.1%) had no complete pathologic response. The combined analysis of VEGF and EGFR is predictive of complete pathologic response in patients undergoing preoperative radiotherapy. In addition, the findings of this study have identified a subgroup of simultaneous EGFR-negative and VEGF-positive patients who are highly resistant to radiotherapy and should perhaps be considered candidates for innovative neoadjuvant combined modalities.

EGF-receptor targeting with monoclonal antibodies in colorectal carcinomas: rationale for a pharmacogenomic approach

Monoclonal antibodies directed against the EGF-receptor (EGFR) have recently been approved for the treatment of metastatic colorectal cancer (CRC) patients with EGFR-positive tumors at immunohistochemistry (IHC). Surprisingly, data demonstrate a lack of correlation between the tumor’s EGFR expression at IHC and outcome. Indeed, as pointed out from small experiences, patients with EGFR-IHC-negative metastatic CRC have the same chance as EGFR-IHC-positive patients to benefit from an anti-EGFR monoclonal antibody, underlying the importance of different, more reliable, selection criteria. In particular, the identification of such predictive factors is important as these agents are expensive, have side effects and are really only effective in a minority of patients. Several potential clinical and biological predictive markers of activity and/or efficacy for such agents have been evaluated in retrospective series with promising results. Moving from clinical data suggesting that there could be a subpopulation of CRC patients that are more liable to benefit from anti-EGFR monoclonal antibodies, here we review major studies on determinants of outcome in this field.

In vivo biomarkers for targeting colorectal neoplasms

Colorectal carcinoma continues to be a leading cause of cancer morbidity and mortality despite widespread adoption of screening methods. Targeted detection and therapy using recent advances in our knowledge of in vivo cancer biomarkers promise to significantly improve methods for early detection, risk stratification, and therapeutic intervention. The behavior of molecular targets in transformed tissues is being comprehensively assessed using new techniques of gene expression profiling and high throughput analyses. The identification of promising targets is stimulating the development of novel molecular probes, including significant progress in the field of activatable and peptide probes. These probes are being evaluated in small animal models of colorectal neoplasia and recently in the clinic. Furthermore, innovations in optical imaging instrumentation are resulting in the scaling down of size for endoscope compatibility. Advances in target identification, probe development, and novel instruments are progressing rapidly, and the integration of these technologies has a promising future in molecular medicine.

The multidisciplinary management of gastrointestinal cancer. The integration of cytotoxics and biologicals in the treatment of metastatic colorectal cancer

The management of patients with metastatic colorectal cancer (CRC) has changed dramatically over the last five years, with increasing chances of prolonged survival. The development of new drugs has contributed to the better outcome of patients with metastatic colorectal cancer. Until the mid-1990s the only available drug, with limited activity in metastatic CRC, was 5-fluorouracil (5-FU). The development of the cytotoxic agents irinotecan, oxaliplatin and capecitabine and of the monoclonal antibodies against the vascular endothelial growth factor (VEGF) bevacizumab and against the epidermal growth factor receptor (EGFR) cetuximab and panitumumab have clearly increased the therapeutic options and have improved the outcome for patients with metastatic colorectal cancer. However, their introduction also raises many new questions and challenges.