Cetuximab monotherapy and cetuximab plus irinotecan in irinotecan-refractory metastatic colorectal cancer

Clinical Trial Designs for Predictive Marker Validation in Cancer Treatment Trials

Current staging and risk-stratification methods in oncology, while helpful, fail to adequately predict malignancy aggressiveness and/or response to specific treatment. Increased knowledge of cancer biology is generating promising marker candidates for more accurate diagnosis, prognosis assessment, and therapeutic targeting. To apply these exciting results to maximize patient benefit, a disciplined application of well-designed clinical trials for assessing the utility of markers should be used. In this article, we first review the major issues to consider when designing a clinical trial assessing the usefulness of a predictive marker. We then present two classes of clinical trial designs: the Marker by Treatment Interaction Design and the Marker-Based Strategy Design. In the first design, we assume that the marker splits the population into groups in which the efficacy of a particular treatment will differ. This design can be viewed as a classical randomized clinical trial with upfront stratification for the marker. In the second design, after the marker status is known, each patient is randomly assigned either to have therapy determined by their marker status or to receive therapy independent of marker status. The predictive value of the marker is assessed by comparing the outcome of all patients in the marker-based arm to that of all of the patients in the non–marker-based arm. We present detailed sample size calculations for a specific clinical scenario. We discuss the advantages and disadvantages of the two trial designs and their appropriateness to specific clinical situations to assist investigators seeking to design rigorous, marker-based clinical trials.

Neoadjuvant Chemotherapy Before Liver Resection for Patients With Unresectable Liver Metastases From Colorectal Carcinoma

Colorectal carcinoma is one of the most common cancers in the world, and more than 50% of these patients develop liver metastases. Despite recent advances, systemic chemotherapy for metastatic disease without the use of surgery is considered palliative, as there are rarely long-term survivors. However, patients who are candidates for surgical resection of their liver metastases can have a prolonged survival or possibly a cure. Consensus guidelines on criteria for resection and prognostic scores help facilitate patient selection, yet only 25% of patients with liver metastases are considered to have resectable metastases. Neoadjuvant chemotherapy has been explored in an attempt to render more patients candidates for resection. First reports using neoadjuvant systemic chemotherapy in patients with unresectable disease found that 13% to 16% of patients could be rendered resectable. Efforts to increase response rates using hepatic arterial infusion or biologic agents may increase resection rates. This review summarizes the current data on neoadjuvant chemotherapy, the rationale for this approach, potential complications, and future prospects.

Preoperative evaluation and postoperative follow-up for patients with rectal cancer

Rectal cancer has a wide variety of presentations. In most cases, it is the surgeon who is faced with the challenge of determining the extent of disease and advising the patient how to proceed with treatment. Utilizing diagnostic tests of the highest accuracy and relevance will help in the selection of the best initial therapy, which is critical for achieving the highest cure rate while also avoiding over-treatment and unnecessary morbidity. Following curative treatment, surveillance testing for detection of recurrence is traditionally done, but the efficacy of this practice has been questioned. Surveillance will detect a number of asymptomatic recurrences that are treatable by potentially curative salvage surgery, but to what extent early detection improves salvage therapy is not well established. In this brief review, the goals, methods, and expected benefits of rectal cancer staging and surveillance are assessed.

[Antibodies against cancer]

Within the revolution of molecular biology in cancer, it should be pointed out the role of monoclonal antibodies clinically utilized as if they were "magic bullets". From the works of Kohler and Milstein in 1975 the evolution has been fast and its inclusion in daily clinical practice gradual. Among the more significant there is anti-CD20 that has revolutionized the treatment of lymphomas. Currently, antibodies conjugated with isotopes derived from anti-CD20 have been produced. Trastuzumab antibody against HER2/neu has opened new prospects in the treatment of breast cancer. Cetuximab antibody against EGFR has achieved good results in the treatment of chemotherapy-resistent colon cancer. Bevacizumab is perhaps the most promising antibody against solid tumors, having shown effectiveness as first line therapy in metastatic colon cancer in combination with chemotherapy.

Critical update and emerging trends in epidermal growth factor receptor targeting in cancer

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase of the ErbB receptor family that is abnormally activated in many epithelial tumors. The aberrant activation of the EGFR leads to enhanced proliferation and other tumor-promoting activities, which provide a strong rationale to target this receptor family. There are two classes of anti-EGFR agents: monoclonal antibodies (MAbs) directed at the extracellular domain of the receptor and small molecule, adenosine triphosphate-competitive inhibitors of the receptor's tyrosine kinase. Anti-EGFR MAbs have shown antitumor activity in advanced colorectal carcinoma, squamous cell carcinomas of the head and neck, non-small-cell lung cancer (NSCLC) and renal cell carcinomas. The tyrosine kinase inhibitors (TKIs) have a partially different activity profile. They are active against NSCLC, and a specific EGFR inhibitor has shown improvement in survival. Recently, mutations and amplifications of the EGFR gene have been identified in NSCLC and predict for enhanced sensitivity to anti-EGFR TKIs. In addition to specific anti-EGFR TKIs, there are broader acting inhibitors such as dual EGFR HER-2 inhibitors and combined anti-pan-ErbB and antivascular endothelial growth factor receptor inhibitors. Current research efforts are directed at selecting the optimal dose and schedule and identifying predictive factors of response and resistance beyond EGFR gene mutations and/or amplifications. Finally, there is a need for improved strategies to integrate anti-EGFR agents with conventional therapies and to explore combinations with other molecular targeted approaches including other antireceptor therapies, receptor-downstream signaling transduction inhibitors, and targeted approaches interfering with other essential drivers of cancer, such as angiogenesis.

HER1/EGFR-targeted agents: predicting the future for patients with unpredictable outcomes to therapy

Therapeutic agents that target the epidermal growth factor receptor (HER1/EGFR) signal pathway, such as small-molecule tyrosine kinase inhibitors and monoclonal antibodies are now advanced in clinical development and two are already licensed for use. Complete/ongoing phase II studies with these agents clearly demonstrate that a small, but significant proportion of patients respond to HER1/EGFR inhibition. However, with our current understanding of tumour biology and genetics, we cannot explain why some patients respond well and others less so or not at all. These differences may be a result of many factors, such as patients' genotype and phenotype, pharmacological and pharmacokinetic differences between agents or the inherent molecular heterogeneity of tumours. In this article, we explore current strategies to identify patients who respond differently and ways to maximise the clinical benefit of these therapies. This includes defining optimal dose and dosing schedules, identifying appropriate combination partners and finding predictive and surrogate markers of response. The association between HER1/EGFR gene mutations in non-small cell lung cancer (NSCLC) tumours and response to HER1/EGFR-targeted agents is also discussed. This may help us to preselect responsive patients, tailor the dose according to the individual's tolerability, or monitor these agents to optimise/interrupt therapy at an early stage.

[The pathologist and EGFR in 2004: I like you, nor do it]

Epithelial growth factor receptor (EGFR) appears as a key element in carcinogenesis. It displays high levels of expression in some tumor types. Its activation induces cell proliferation, angiogenesis, cell mobility and inhibition of apoptosis. EGFR inhibitors such as monoclonal antibodies or small molecules tyrosine kinase inhibitors have been developed. For EGFR, the diversity of the activation means (amplification, mutation, enhanced transcription, ligands...) leads to technical caveats. Immunohistochemistry appears to be the most appropriate test for clinical use, but standardized assays and scoring systems are mandatory. Pathologists are involved in the selection of patients for a monoclonal antibody based targeted treatment, Erbitux, and numerous standardization efforts are provided. No consensus has been reached, to date, for a scoring system. Whether the EGFR status has to be tested for the selection of patients is a non answered question. The selection of the "right patient for the right treatment" might be through the evaluation of other putative markers involved in resistance. EGFR testing may be required before targeted treatment. An exciting endpoint might be the functional and dynamic evaluation of EGFR and downstream proteins, for patients, before and during treatment. The exact role of the pathologist still have to be accurately determined.

Molecular mechanisms of drug resistance

Resistance to chemotherapy limits the effectiveness of anti-cancer drug treatment. Tumours may be intrinsically drug-resistant or develop resistance to chemotherapy during treatment. Acquired resistance is a particular problem, as tumours not only become resistant to the drugs originally used to treat them, but may also become cross-resistant to other drugs with different mechanisms of action. Resistance to chemotherapy is believed to cause treatment failure in over 90% of patients with metastatic cancer, and resistant micrometastic tumour cells may also reduce the effectiveness of chemotherapy in the adjuvant setting. Clearly, if drug resistance could be overcome, the impact on survival would be highly significant. This review focuses on molecular mechanisms of drug resistance that operate to reduce drug sensitivity in cancer cells. Drug resistance can occur at many levels, including increased drug efflux, drug inactivation, alterations in drug target, processing of drug-induced damage, and evasion of apoptosis. Advances in DNA microarray and proteomic technology, and the ongoing development of new targeted therapies have opened up new opportunities to combat drug resistance. We are now able to characterize the signalling pathways involved in regulating tumour cell response to chemotherapy more completely than ever before. This will facilitate the future development of rational combined chemotherapy regimens, in which the newer targeted therapies are used in combination with cytotoxic drugs to enhance chemotherapy activity. The ability to predict response to chemotherapy and to modulate this response with targeted therapies will permit selection of the best treatment for individual patients.

New science-based endpoints to accelerate oncology drug development

Although several new oncology drugs have reached the market, more than 80% of drugs for all indications entering clinical development do not get marketing approval, with many failing late in development often in Phase III trials, because of unexpected safety issues or difficulty determining efficacy, including confounded outcomes. These factors contribute to the high costs of oncology drug development and clearly show the need for faster, more cost-effective strategies for evaluating oncology drugs and better definition of patients who will benefit from treatment. Remarkable advances in the understanding of neoplastic progression at the cellular and molecular levels have spurred the discovery of molecularly targeted drugs. This progress along with advances in imaging and bioassay technologies are the basis for describing and evaluating new biomarker endpoints as well as for defining other biomarkers for identifying patient populations, potential toxicity, and providing evidence of drug effect and efficacy. Definitions and classifications of these biomarkers for use in oncology drug development are presented in this paper. Science-based and practical criteria for validating biomarkers have been developed including considerations of mechanistic plausibility, available methods and technology, and clinical feasibility. New promising tools for measuring biomarkers have also been developed and are based on genomics and proteomics, direct visualisation by microscopy (e.g., confocal microscopy and computer-assisted image analysis of cellular features), nanotechnologies, and direct and remote imaging (e.g., fluorescence endoscopy and anatomical, functional and molecular imaging techniques). The identification and evaluation of potential surrogate endpoints and other biomarkers require access to and analysis of large amounts of data, new technologies and extensive research resources. Further, there is a requirement for a convergence of research, regulatory and drug developer thinking - an effort that will not be accomplished by individual scientists or research institutions. Research collaborations are needed to foster development of these new endpoints and other biomarkers and, in the United States (US), include ongoing efforts among the Food and Drug Administration (FDA), National Cancer Institute (NCI), academia, and industry.

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

PURPOSE

To establish evidence of activity, or lack thereof, of cetuximab-based therapy in patients with refractory colorectal cancer with tumors that do not demonstrate epidermal growth factor receptor (EGFR) expression by immunohistochemistry (IHC).

PATIENTS AND METHODS

Pharmacy computer records were reviewed to identify all patients who received cetuximab at Memorial Sloan-Kettering Cancer Center in a nonstudy setting during the first 3 months of cetuximab's commercial availability. Medical records of these patients were then reviewed to identify colorectal cancer patients who had experienced failure with a prior irinotecan-based regimen and who had a pathology report indicating an EGFR-negative tumor by IHC. Pathology slides from these patients were reviewed by a reference pathologist to confirm EGFR negativity, and computed tomography scans during cetuximab-based therapy were reviewed by a reference radiologist. Response rates were reported using WHO criteria.

RESULTS

Sixteen chemotherapy-refractory, EGFR-negative colorectal cancer patients who received cetuximab in a nonstudy setting were identified. Fourteen of these patients received cetuximab plus irinotecan, and two received cetuximab monotherapy. In the 16 patients, four major objective responses were seen (response rate, 25%; 95% CI, 4% to 46%).

CONCLUSION

Colorectal cancer patients with EGFR-negative tumors have the potential to respond to cetuximab-based therapies. EGFR analysis by current IHC techniques does not seem to have predictive value, and selection or exclusion of patients for cetuximab therapy on the basis of currently available EGFR IHC does not seem warranted.

Projecting future drug expenditures—2005

PURPOSE

Drug expenditure trends in 2003 and 2004 and projected drug expenditures for 2005 are discussed.

SUMMARY

Various factors are likely to affect drug costs, including drug prices, drugs in development, and generic drugs. In 2003 there was a continued moderation of the increase in drug expenditures. Drug expenditures increased by 11.4% from 2002 to 2003. Through the first nine months of 2004, expenditures increased by only 8.7% compared with 2003. This moderation can be attributed to many factors, particularly patent expirations, prescription-to-nonprescription conversions and a continued slowdown in new drug approvals. Higher cost sharing for consumers and continued weaknesses in several sectors of the U.S. economy affecting employment levels and insurance coverage also contributed to this smaller increase in drug utilization. It is expected that 2005 drug expenditure growth will out-pace the growth in overall health care expenditures and growth in the economy.

CONCLUSION

In 2005, there should be a 10-12% increase in drug expenditures in outpatient settings, a 12-15% increase in clinics, and a 6-9% increase in hospitals.

New options and old dilemmas in the treatment of patients with advanced colorectal cancer

With more data on the use of oxaliplatin and irinotecan available, and the recent approval of two signal transduction inhibitors for patients with advanced colorectal cancer, there are now many treatment options to choose from. From the current regimens no straightforward choice can be made that provides any patient with the optimal chance for prolonged survival with the least side-effects. The current data concerning timing and duration of chemotherapy, combination or sequential therapy, preference of agents for first-line treatment, oral fluoropyrimidines, neo-adjuvant chemotherapy for irresectable liver metastases, and the use of signal transduction inhibitors are reviewed.

Colorectal cancer

Every year, more than 945000 people develop colorectal cancer worldwide, and around 492000 patients die. This form of cancer develops sporadically, in the setting of hereditary cancer syndromes, or on the basis of inflammatory bowel diseases. Screening and prevention programmes are available for all these causes and should be more widely publicised. The adenoma-carcinoma sequence is the basis for development of colorectal cancer, and the underlying molecular changes have largely been identified. Prognosis depends on factors related to the patient, treatment, and tumour, and the expertise of the treatment team is one of the major determinants of outcome. New information on the molecular basis of this cancer have led to the development of targeted therapeutic options, which are being tested in clinical trials. Further clinical progress will largely depend on the broader implementation of multidisciplinary treatment strategies following the principles of evidence-based medicine.

Lessons from TRAIL-resistance mechanisms in colorectal cancer cells: paving the road to patient-tailored therapy

Colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Intrinsic, as well as acquired, resistance to chemotherapy remains a major problem in the treatment of this disease. It is, therefore, of great importance to develop new, patient-tailored, treatment strategies for colorectal cancer patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) acts through the pro-apoptotic DR4 and DR5 receptors in tumor cells without harming normal cells and will soon be tested in clinical trials as a novel anti-cancer agent. However, not all human colon cancer cell lines are sensitive to TRAIL due to intrinsic or acquired TRAIL-resistance. This review discusses the mechanisms and modulation of TRAIL-resistance in colon cancer cells. Cell sensitivity to TRAIL can be affected by TRAIL-receptor expression at the cell membrane, DR4/DR5 ratio and functionality of TRAIL-receptors. Additional intracellular factors leading to TRAIL-resistance affect the caspase 8/c-FLIP ratio, such as loss of caspase 8 and caspase 10 due to mutations or gene methylation, CARP-dependent degradation of active caspase 8 and changes in caspase 8 or c-FLIP expression levels. Further downstream in the TRAIL apoptotic pathway, Bax mutations, or increased expression of IAP family members, in particularly XIAP and survivin, also cause resistance. Chemotherapeutic drugs, NSAIDs, interferon-gamma and proteasome inhibitors can overcome TRAIL-resistance by acting on TRAIL-receptor expression or changing the expression of pro- or anti-apoptotic proteins.

New chemotherapeutic strategies in colorectal cancer

Since colorectal cancer is the second most prevalent cancer worldwide, its treatment remains a major challenge for researchers, gastroenterologists and oncologists. Despite curative resections, half of all patients diagnosed with colorectal cancer die because of their underlying disease. Integral chemotherapeutic components of standard regimens are 5-fluorouracil (5-FU), its modulation by folinic acid and irinotecan or oxaliplatin. All these drugs sequentially given have results in terms of median overall survival of more than 20 months in the palliative treatment of advanced colorectal cancer. Oral fluoropyrimidines, currently under clinical investigation, are likely to substitute continuous 5-FU. Inhibitors of growth factor receptors or their signaling may further prolong disease-free and overall survival rates. Preliminary evidence exists that improved adjuvant and neoadjuvant chemotherapy strategies may further improve the prognosis, mainly because more patients are able to go for primary or secondary surgery with curative intent.

Mechanisms of drug resistance in cancer chemotherapy

The management of cancer involves procedures, which include surgery, radiotherapy and chemotherapy. Development of chemoresistance is a persistent problem during the treatment of local and disseminated disease. A plethora of cytotoxic drugs that selectively, but not exclusively, target actively proliferating cells include such diverse groups as DNA alkylating agents, antimetabolites, intercalating agents and mitotic inhibitors. Resistance constitutes a lack of response to drug-induced tumour growth inhibition; it may be inherent in a subpopulation of heterogeneous cancer cells or be acquired as a cellular response to drug exposure. Resistance varies. Although regulatory approval may require efficacy in as few as 20% of trial cohorts, a drug may subsequently be used in unselected patients displaying resistance to the treatment. Principal mechanisms may include altered membrane transport involving the P-glycoprotein product of the multidrug resistance (MDR) gene as well as other associated proteins, altered target enzyme (e.g. mutated topoisomerase II), decreased drug activation, increased drug degradation due to altered expression of drug-metabolising enzymes, drug inactivation due to conjugation with increased glutathione, subcellular redistribution, drug interaction, enhanced DNA repair and failure to apoptose as a result of mutated cell cycle proteins such as p53. Attempts to overcome resistance mainly involve the use of combination drug therapy using different classes of drugs with minimally overlapping toxicities to allow maximal dosages and with narrowest cycle intervals, necessary for bone marrow recovery. Adjuvant therapy with P-glycoprotein inhibitors and, in specific instances, the use of growth factor and protein kinase C inhibitors are newer experimental approaches that may also prove effective in abrogating or delaying onset of resistance. Gene knockout using antisense molecules may be another effective way of blocking drug resistance genes. Conversely, drug resistance may also be used to good purpose by transplanting retrovirally transformed CD34 cells expressing the MDR gene to protect the bone marrow during high-dose chemotherapy.

Role for the epidermal growth factor receptor in neurofibromatosis-related peripheral nerve tumorigenesis

Benign neurofibromas and malignant peripheral nerve sheath tumors are serious complications of neurofibromatosis type 1. The epidermal growth factor receptor is not expressed by normal Schwann cells, yet is overexpressed in subpopulations of Nf1 mutant Schwann cells. We evaluated the role of EGFR in Schwann cell tumorigenesis. Expression of EGFR in transgenic mouse Schwann cells elicited features of neurofibromas: Schwann cell hyperplasia, excess collagen, mast cell accumulation, and progressive dissociation of non-myelin-forming Schwann cells from axons. Mating EGFR transgenic mice to Nf1 hemizygotes did not enhance this phenotype. Genetic reduction of EGFR in Nf1(+/-);p53(+/-) mice that develop sarcomas significantly improved survival. Thus, gain- and loss-of-function experiments support the relevance of EGFR to peripheral nerve tumor formation.

Timeline: Chemotherapy and the war on cancer

The era of chemotherapy began in the 1940s with the first uses of nitrogen mustards and antifolate drugs. Cancer drug development since then has transformed from a low-budget, government-supported research effort to a high-stakes, multi-billion dollar industry. The targeted-therapy revolution has arrived, but the principles and limitations of chemotherapy discovered by the early researchers still apply. This article chronicles the history of modern chemotherapy and identifies remaining challenges for the next generation of researchers.

Genomics and the second golden era of cancer drug development

The first golden era of cancer drug development was initiated in the 1940s and gave rise to the cytotoxic agents that dominate current cancer medicine. The second golden era is now underway in which cancer genomics will direct drug development.

The Evolution of Antibodies into Versatile Tumor-Targeting Agents

In recent years, monoclonal antibodies have become important weapons in the arsenal of anticancer drugs, and in select cases are now the drugs of choice due to their favorable toxicity profiles. Originally developed to confer passive immunity against tumor-specific antigens, clinical uses of monoclonal antibodies are expanding to include growth factor sequestration, signal transduction modulation, and tumor-specific drug delivery. In this review, we shall present the origins of antibody therapeutics within the field of immunotherapy and their evolution into effective anticancer agents, then discuss their multiple mechanisms of action, the basis of their tumor selectivity, and their therapeutic properties compared with traditional therapies. Antibodies are complex molecules whose efficacy and toxicity depend on the antigen, the antibody, any conjugated groups, and even the patient. Finally, we shall present new technologies being developed to increase the efficacy and selectivity of antibody-based therapeutics. Interestingly, many of the new approaches straddle the middle ground between immunotherapy and the traditional modalities of chemotherapy and radiotherapy, and can be seen as ways of combining the selectivity of the former with the efficacy of the latter.

Epidermal growth factor receptor-targeted treatment for advanced colorectal carcinoma

Substantial effort has focused on the development of novel targeted agents for treating patients with late-stage colorectal carcinoma. These agents are designed specifically to inhibit biochemical processes associated with pathogenesis. Numerous molecules targeting the epidermal growth factor receptor have been investigated as therapeutic agents and appear to herald a shift in the treatment paradigm for colorectal carcinoma.

Prevention and therapy of colorectal cancer

Colorectal cancer is expected to affect more than 146,000 and kill more than 57,000 Americans in 2004. Increased understanding of carcinogenesis is transforming clinical approaches to all stages of this disease. During the last 5 years, four new drugs have been approved for colorectal cancer treatment, and substantial progress has been made in identifying and developing agents that prevent or delay carcinogenesis. These advances substantiate target-driven approaches to cancer prevention and treatment, and provide fruitful opportunities for future investigations.

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

PURPOSE

We hypothesized that the detection of epidermal growth factor receptor (EGFR) expression performed in primary tumors for treatment with EGFR-targeted monoclonal antibodies could not always correlate with EGFR status in metastatic sites, thus making cancer cells in these sites resistant to therapy. The aim of our study was to correlate EGFR expression on primary tumors and related metastases in order to find out whether assessing EGFR status on primary cancer is to be considered an effective tool for planning treatment with EGFR-targeted antibodies.

PATIENTS AND METHODS

We retrospectively evaluated EGFR immunohistochemistry from primary tumors and related metastatic sites in 99 colorectal cancer patients. The site of primary tumor was colon in 77 patients (78%) and rectum in 22 patients (22%). Metastatic sites analyzed were liver in 84 patients (81%), lung in 13 patients (13%), bone in one patient (1%), and brain in five patients (5%). EGFR status was defined as positive if the percentage of malignant cells stained was > or = 1%.

RESULTS

EGFR status was positive in 53 primary tumors (53%). In 19 primary tumors expressing EGFR (36%), the corresponding metastatic site was found negative, whereas it was found positive in seven metastases (15%) from EGFR-negative primary cancers. The difference between these two groups of patients (ie, EGFR-positive to EGFR-negative v EGFR-negative to EGFR-positive) was statistically significant (P = .036).

CONCLUSION

Our results suggest that the detection of the EGFR in primary colorectal cancer could be inadequate for planning therapy with EGFR-targeted monoclonal antibodies in a considerable proportion of both EGFR-positive and -negative primary tumors (36% and 15%, respectively).

Future directions in the use of antiangiogenic agents in patients with colorectal cancer

Considerable progress has been achieved in the treatment of colorectal cancer over the last few years, but it remains a major cause of cancer death in the United States. Among the most important recent developments is the understanding that angiogenesis is a fundamental requirement of early tumor growth and metastasis and therefore is an important target for therapy. The recent positive results obtained by adding bevacizumab to a standard regimen of chemotherapy highlight the potential impact of angiogenesis. Although not the final answer to the problem of advanced colorectal cancer, the success obtained with bevacizumab should encourage the development of even more effective and less toxic molecular targeted agents and regimens. The tyrosine kinase inhibitor vatalanib (PTK787/ZK222584) is in the final stages of clinical development, and several other promising compounds will be available for clinical development in the near future. Agents already commercially available, such as the monoclonal antibody cetuximab, may have some antiangiogenic properties as well. However, the greatest benefit from antiangiogenic therapies may come from their combined use, not only with conventional chemotherapy but also with other molecular targeted agents, radiotherapy, and surgery in a true multidisciplinary approach.

15-Hydroxyprostaglandin dehydrogenase is down-regulated in colorectal cancer

Prostaglandin E2 (PGE2) can stimulate tumor progression by modulating several proneoplastic pathways, including proliferation, angiogenesis, cell migration, invasion, and apoptosis. Although steady-state tissue levels of PGE2 stem from relative rates of biosynthesis and breakdown, most reports examining PGE2 have focused solely on the cyclooxygenase-dependent formation of this bioactive lipid. Enzymatic degradation of PGE2 involves the NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). The present study examined a range of normal tissues in the human and mouse and found high levels of 15-PGDH in the large intestine. By contrast, the expression of 15-PGDH is decreased in several colorectal carcinoma cell lines and in other human malignancies such as breast and lung carcinomas. Consistent with these findings, we observe diminished 15-Pgdh expression in ApcMin+/- mouse adenomas. Enzymatic activity of 15-PGDH correlates with expression levels and the genetic disruption of 15-Pgdh completely blocks production of the urinary PGE2 metabolite. Finally, 15-PGDH expression and activity are significantly down-regulated in human colorectal carcinomas relative to matched normal tissue. In summary, these results suggest a novel tumor suppressive role for 15-PGDH due to loss of expression during colorectal tumor progression.

Modulation of DNA Repair In vitro after Treatment with Chemotherapeutic Agents by the Epidermal Growth Factor Receptor Inhibitor Gefitinib (ZD1839)

PURPOSE

The epidermal growth factor receptor (EGFR) is commonly expressed in human tumors and provides a target for therapy. Gefitinib (Iressa, ZD1839) is a quinazoline derivative that inhibits EGFR tyrosine kinase activity. Gefitinib demonstrated anticancer efficacy in vivo, and although experiments in vitro have suggested that inhibition of EGFR modulates the activity of chemotherapeutic agents, the mechanism of this interaction is unclear. We investigated mechanisms for this modulation.

EXPERIMENTAL DESIGN

The antiproliferative effect of gefitinib alone or combined with cisplatin, melphalan, and etoposide was determined in a human breast (MCF-7) cancer cell line. Using the alkaline single-cell gel electrophoresis (comet) assay, we investigated kinetics of DNA damage and repair after treatment with the chemotherapeutic drugs combined with gefitinib. To investigate whether the phosphatidylinositol 3'-kinase pathway was contributing to repair-inhibition produced by gefitinib, cells were exposed to chemotherapy in combination with the phosphatidylinositol 3'-kinase inhibitor LY294002.

RESULTS

A superadditive (synergistic) increase in growth inhibition for combined treatment with gefitinib was found for cisplatin and etoposide, but not with melphalan. There was delayed repair of DNA strand breaks after treatment with etoposide combined with gefitinib, and repair of DNA interstrand cross-links produced by cisplatin is delayed in combination with gefitinib. Inhibition of cell proliferation and DNA repair was identical in cells treated with LY294002. Immunoprecipitation of cell extracts demonstrated that after exposure to gefitinib, there was an association between EGFR and DNA-PK(CS).

CONCLUSION

Gefitinib acts through inhibition of repair of cisplatin and etoposide-induced DNA damage; this effect is mimicked by inhibitors of the phosphatidylinositol 3'-kinase suggesting similar mechanisms of action.