Growth factor receptors as targets for lung cancer therapy

Dysregulated signal transduction of growth factor receptors contributes to the process of malignant transformation by promoting cell proliferation, motility, and invasion through extracellular matrix as well as angiogenesis. Epidermal growth factor receptors (EGFR), and to a lesser extent HER2/neu, is overexpressed in the majority of nonsmall cell lung cancer (NSCLC) compared with normal tissue, making them ideal targets for the development of novel therapeutics for this disease. Multiple clinical trials have demonstrated that antireceptor strategies employing antagonistic monoclonal antibodies or low molecular weight tyrosine kinase inhibitors against EGFR are well tolerated and occasionally result in objective clinical responses in patients with advanced NSCLC. This report provides an overview of the molecular basis and the preclinical evidence supporting clinical development of anti-EGFR therapy as well as results of phase I-III clinical trials of these compounds in treating patients with solid tumors including NSCLC.     

Comparison of the cytotoxic activities of chemotherapeutic drugs using a human bladder cancer cell line

Summary Many chemotherapeutic drugs have been used to treat patients with advanced bladder cancer, but few of these have been evaluated adequately in phase II clinical trials. Continuous cell lines provide one means for comparing the in vitro cytotoxicities of anticancer agents. In this study, a continuous cell line derived from a transitional cell cancer of the human bladder, which still produces tumours histologically similar to the tumour of origin on xenotransplantation, was used to measure the in vitro cytotoxicities of twelve chemotherapeutic drugs by clonogenic assay. The most cytotoxic agents tested were methotrexate, mitoxantrone, adriamycin, mitomycin C and cisplatin. These in vitro findings are compatible with the activity of these drugs given systemically as single agents in phase II clinical trials in patients with advanced bladder cancer.     

Anti-EGF receptor therapy

The epidermal growth factor receptor (EGFR) signalling pathway contributes to a number of processes important to tumour progression, including cell proliferation, apoptosis, angiogenesis and metastatic spread. EGFR signalling is thought to be an important cell survival mechanism in hormone-resistant prostate cancer. ZD1839 ('Iressa') is an orally active, selective EGFR-tyrosine kinase inhibitor (EGFR-TKI) which blocks signal transduction pathways implicated in promoting cancer growth. In preclinical studies, ZD1839 alone, and in combination with cytotoxic agents, produced reversible growth inhibition and growth delay in a wide range of tumour cell lines and human tumour xenografts. Preliminary results from phase I trials in patients with advanced disease suggest that ZD1839 has an acceptable tolerability profile and promising clinical efficacy in patients with a variety of tumour types, including hormone-resistant prostate cancer, where new treatment strategies are needed. Prostate Cancer and Prostatic Diseases (2000) 3, 296-302     

Emerging perspectives in epidermal growth factor receptor targeting in head and neck cancer

The epidermal growth factor receptor (EGFR) has been shown to be a promising therapeutic target in head and neck cancer. Cetuximab, a monoclonal antibody against EGFR, has been approved in the United States for use with radiotherapy for head and neck squamous cell carcinoma. However, the role of EGFR targeting agents in other therapeutic modalities, such as combined chemoradiotherapy or induction chemotherapy, remains to be defined. Although results from several clinical trials have demonstrated the therapeutic potentials of EGFR targeting agents in these settings, further studies are necessary before definitive conclusions can be made. The concurrent targeting of EGFR along with other pathways important in carcinogenesis may hold significant therapeutic potential. In particular, several clinical trials are studying the effects of combining agents that target the vascular endothelial growth factor with EGFR inhibitors. Last, studies are ongoing to elucidate the predictive and correlative biomarkers in anti-EGFR therapy to allow for proper patient selection. In the case of cetuximab, these correlative biomarkers may include elements of the immune system in addition to the signal transduction proteins involved in EGFR pathway.     

Epidermal growth factor receptor antagonists: novel therapy for the treatment of high-grade gliomas

Overactivation of epidermal growth factor receptor (EGFR) signaling has been recognized as an important step in the pathogenesis and progression of multiple forms of cancer of epithelial origin. This knowledge has led to a surge of interest in novel anticancer therapies targeting key constituents of the EGFR signal transduction pathway. Several molecular strategies have been developed recently to modulate either EGFR or the downstream signal beyond the cell surface receptor. The important role of aberrant EGFR signaling in the progression of malignant gliomas makes EGFR-targeted therapies of particular interest in this form of cancer. The use of anti-EGFR therapies against malignant brain tumors, although in its infancy, promises to yield exciting results as these new drugs probably will enhance the usefulness of existing therapies.     

Neoadjuvant Treatment of High-Risk,Clinically Localized Prostate Cancer Prior to Radical Prostatectomy

Multimodal strategies combining local and systemic therapy offer the greatest chance of cure for many with men with high-risk prostate cancer who may harbor occult metastatic disease. However, no systemic therapy combined with radical prostatectomy has proven beneficial. This was in part due to a lack of effective systemic agents; however, there have been several advancements in the metastatic and castrate-resistant prostate cancer that might prove beneficial if given earlier in the natural history of the disease. For example, novel hormonal agents have recently been approved for castration-resistant prostate cancer with some early phase II neoadjuvant showing promise. Additionally, combination therapy with docetaxel-based chemohormonal has demonstrated a profound survival benefit in metastatic hormone-naïve patients and might have a role in eliminating pre-existing ADT-resistant tumor cells in the neoadjuvant setting. The Cancer and Leukemia Group B (CALGB)/Alliance 90203 trial has finished accrual and should answer the question as to whether neoadjuvant docetaxel-based chemohormonal therapy provides an advantage over prostatectomy alone. There are also several promising targeted agents and immunotherapies under investigation in phase I/II trials with the potential to provide benefit in the neoadjuvant setting.     

Mechanisms of disease: the role of heat-shock protein 90 in genitourinary malignancy

Insight into the molecular biology of cancer has allowed the development of novel therapeutic strategies that target specific oncogenic pathways. Molecular therapeutic strategies are now part of the armamentarium available against urologic malignancy. Among the many targets of interest in urologic cancer, heat-shock protein 90 (HSP90) shows great promise. This molecule has a major role in prostate as well as in renal malignancy. In contrast to other targets, where cancer might escape inhibition via alternative pathways, HSP90 operates at multiple checkpoints in a cancer cell. Its inhibition could, therefore, prove more difficult for neoplastic cells to overcome. Inhibitors of HSP90, such as geldanamycin and its derivatives (17-allylamino-17-demethoxygeldanamycin and 17-dimethylaminoethylamino-17-demethoxygeldanamycin, known as 17AAG and 17DMAG, respectively) are available and have shown activity both in vivo and in vitro. 17AAG is currently being tested for efficacy in humans after having completed phase I trials, while 17DMAG is still in phase I evaluation. Phase II trials of HSP90 inhibitors in urologic malignancy are being conducted in kidney and advanced prostate cancer. Beyond monotherapy, HSP90 inhibitors might also prove to be beneficial in combination therapy with other chemotherapeutic agents in advanced disease. Studies being conducted in prostate cancer will hopefully help to define this potential application better.     

Antibodies and vaccines--hope or illusion?

The search for target molecules on tumor cells eliciting strong immune responses in cancer patients has been pursued over decades. Growth factors and their respective receptors were discovered as suitable targets for passive or active immunotherapy approaches. Monoclonal antibodies directed against some of these targets like the proto-oncogene HER2/neu have become an accepted standard of therapy in the clinical management of subgroups of HER2/neu overexpressing breast cancer patients and in other malignancies. Antibodies against multiple other target molecules like epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), etc., are explored in ongoing trials in order to enter clinical practice in the near future. More recently, potent techniques have been developed to identify cancer antigens eliciting spontaneous immune responses in cancer patients. Cancer vaccination strategies targeting some of these cancer antigens have also been developed, and are maturing for clinical application. With reliable immunomonitoring techniques in place it has been shown that vaccination with some of these cancer antigens may induce strong integrated (humoral and cellular) immune responses in antigen-positive cancer patients. A prominent example is the cancer testis (CT-) antigen NY-ESO-1, which is expressed in 30% of all breast cancers. NY-ESO-1 is one of the most immunogenic human cancer antigens known to date. The aim of ongoing clinical trials is to induce or augment preexisting immune responses in cancer patients with strong NY-ESO-1 positive disease. There is preliminary evidence that patients with strong NY-ESO-1-specific immune responses have more favorable courses of disease. In several clinical phase I trials targeting HER2/neu it was shown that antigen-specific T cell responses could be induced. Another new cancer antigen explored for cancer vaccination is the breast differentiation antigen NY-BR-1, expressed in 70% of all tested primary breast cancers. Although this cancer antigen is still in preclinical testing, its strong and restricted pattern of expression in breast cancer makes it a promising target for clinical development. For all cancer vaccines there is mounting evidence that the stage of disease to be targeted is minimal residual disease or in adjuvant settings.     

Antibodies and vaccines–hope or illusion?

The search for target molecules on tumor cells eliciting strong immune responses in cancer patients has been pursued over decades. Growth factors and their respective receptors were discovered as suitable targets for passive or active immunotherapy approaches. Monoclonal antibodies directed against some of these targets like the proto-oncogene HER2/neu have become an accepted standard of therapy in the clinical management of subgroups of HER2/neu overexpressing breast cancer patients and in other malignancies. Antibodies against multiple other target molecules like epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), etc., are explored in ongoing trials in order to enter clinical practice in the near future. More recently, potent techniques have been developed to identify cancer antigens eliciting spontaneous immune responses in cancer patients. Cancer vaccination strategies targeting some of these cancer antigens have also been developed, and are maturing for clinical application. With reliable immunomonitoring techniques in place it has been shown that vaccination with some of these cancer antigens may induce strong integrated (humoral and cellular) immune responses in antigen-positive cancer patients. A prominent example is the cancer testis (CT-) antigen NY-ESO-1, which is expressed in 30% of all breast cancers. NY-ESO-1 is one of the most immunogenic human cancer antigens known to date. The aim of ongoing clinical trials is to induce or augment preexisting immune responses in cancer patients with strong NY-ESO-1 positive disease. There is preliminary evidence that patients with strong NY-ESO-1-specific immune responses have more favorable courses of disease. In several clinical phase I trials targeting HER2/neu it was shown that antigen-specific T cell responses could be induced. Another new cancer antigen explored for cancer vaccination is the breast differentiation antigen NY-BR-1, expressed in 70% of all tested primary breast cancers. Although this cancer antigen is still in preclinical testing, its strong and restricted pattern of expression in breast cancer makes it a promising target for clinical development. For all cancer vaccines there is mounting evidence that the stage of disease to be targeted is minimal residual disease or in adjuvant settings.     

Therapeutic options for hormone-refractory prostate cancer in 2007

Prostate cancer is the most commonly diagnosed cancer in American men and a major health problem. While localized disease has an excellent chance for cure, metastatic disease leads to androgen-independent progression and death within a few years. Although docetaxel represents an important therapeutic milestone and is the current standard of care for metastatic hormone-refractory prostate cancer (HRPC), most patients eventually progress because of clonal selection of therapy-resistant cells or the development of cells with a drug-resistant phenotype. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy, the rational design of targeted therapeutics is possible. Over the last few years, many gene targets that regulate apoptosis, proliferation, and cell signalling have been identified, and numerous novel compounds have entered clinical trials either as single agents or in combination with cytotoxic chemotherapy. Neoadjuvant trials in particular must be further encouraged since they allow detection of biological activity in the prostatectomy specimen. This article reviews new treatment options available for men with advanced prostate cancer. Even though HRPC remains incurable, it is not untreatable. Recent findings are very promising, but challenges remain in demonstrating effective anti-tumor activity and showing a clinically relevant survival benefit in Phase III trials.     

Gene-modified cellular vaccines: technologic aspects and clinical problems

Activity in the cancer vaccine sector has quadrupled in the last decade. A number of therapeutic cancer vaccines are reaching the market. The huge number of clinical trials in progress is expected to undergo evaluation shortly. Whole cell tumor vaccines or gene-modified whole cells are being intensively tested in clinical trials. However, the specificity of the product makes the drug development process, including clinical trials, a considerable challenge. Their complex nature, standardization of manufacturing, and characterization often pose problems. Accordingly, to develop a well characterized controlled vaccine, more than a few factors need to be established. The final cell vaccine formulation must be characterized for product identity, purity, impurities, sterility, potency, cell viability, and total cell number. Therapeutic cancer vaccines show different clinical characteristics than cytotoxic anticancer agents. Unfortunately, the rules of clinical trial design for active immunotherapy have been adapted from the designs for examination of cancer chemotherapy. Accordingly, many research groups and clinical consortia have postulated modifications and unifications of existing clinical trial designs. A clinical development model has suggested that cancer vaccines be investigated in 2 categories of clinical trials: proof-of- principle and efficacy. Moreover, it is becoming clear that no drug demonstrates anticancer activity in all patients. Thus, intensive studies have been performed to seek specific biomarkers which could help stratify patients who are likely to respond to a particular treatment. This presents a big challenge beyond the analysis of the immune system status necessary to assess the effects of active immunotherapy.     

Novel targets and approaches in advanced prostate cancer

PURPOSE OF REVIEW: The development of therapeutic resistance is the underlying cause for most cancer deaths. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in prostate cancer, the rational design of targeted therapeutics is possible. We review new treatment options for men with advanced prostate cancer. RECENT FINDINGS: Although the taxanes currently represent the most active chemotherapeutic agents and standard of care for first-line treatment of metastatic hormone-refractory prostate cancer, most patients eventually progress because of intrinsic or acquired drug resistance. In recent years, increased knowledge of cancer progression and therapeutic resistance has identified many gene targets that regulate apoptosis, proliferation, and cell signalling. To date, numerous novel compounds have entered clinical trials as either single agents or in combination with cytotoxic chemotherapy. SUMMARY: Even though hormone-refractory prostate cancer is still incurable, it is not untreatable. As cancer cells are proficient at adapting to therapeutic stressors, a combination regimen with drugs that target crucial cellular networks like the apoptotic rheostat may be more promising than treatment with highly selective single-target agents. Recent findings are very hopeful, but challenges remain to demonstrate effective antitumour activity in phase III trials with survival as the principal endpoint.     

Clinical trials in triple negative breast cancer

Triple negative breast cancer (TNBC) is an aggressive subtype of the disease against which targeted therapies that significantly improve the prognosis for hormone receptor-positive and HER2-overexpressing breast cancers are ineffective. This article summarizes our current understanding of the biology of TNBC as it relates to the efficacy of standard and investigational therapies. It reviews promising preliminary results that have been achieved with chemotherapeutic agents including the platinum analogs and agents that inhibit DNA repair by targeting poly ADP-ribose polymerase (PARP), while anti-angiogenic therapies and those that target the epidermal growth factor receptor (EGFR) have had more limited success. Agents that target a number of other pathways which appear to influence the biologic aggressiveness of TNBC, including src and PI3K, are in early stage clinical trials. As we learn more about TNBC, and which of its characteristics determine treatment response and resistance, we should become better able to select appropriate therapies for biologically defined patient subgroups, and reduce the clinical burden of this disease.     

Novel therapeutics for the management of castration-resistant prostate cancer (CRPC)

Androgen-deprivation therapy is the initial treatment for metastatic prostate cancer. Although highly effective, all men who live long enough will eventually experience disease progression and develop castration resistance. Patients who have castration-resistant prostate cancer (CRPC) have a median survival of ≈1-3 years. When evaluating novel therapies for CRPC, one must consider the endpoints measured for determination of response. We will discuss PSA, circulating tumour cells, progression-free survival, overall survival, and other endpoints used in clinical trials. Docetaxel and sipuleucel-T are currently the preferred first-line treatment options for patients with CRPC; cabazitaxel is a new option for patients after docetaxel failure. Patients with CRPC historically have very poor survival, underscoring the unmet need for novel therapeutics. Although many agents appear promising, well-designed randomized phase III trials are necessary to establish their impact on survival and health-related quality of life. Promising new therapies include hormonal agents, such as abiraterone and MDV3100, as well as other novel immunotherapeutics and anti-prostate-specific membrane antigen therapies. In the future, we anticipate therapies tailored to individual patients' malignancies using various molecular analyses.     

Clinical endpoints for drug development in prostate cancer

PURPOSE OF REVIEW: Overall survival remains the benchmark in phase III settings of novel agents in castration-resistant metastatic prostate cancer. This review highlights many of the current potential early measures of response and clinical benefit that are worthy of future study and validation in this disease. RECENT FINDINGS: The clinical evaluation of novel agents in advanced prostate cancer remains challenging for several reasons. Men with metastatic prostate cancer often have bone-only disease in which formal radiologic response and progression criteria may not apply. Declines in serum prostate-specific antigen levels may be modest surrogates of response to cytotoxic agents such as docetaxel, but have not been validated for agents with novel mechanisms of action, such as antiangiogenic, immunologic, or cytostatic drugs. Novel radiologic imaging techniques such as PET scans are not yet validated for use in monitoring or staging advanced prostate cancer. Measures of delay, control, and palliation of metastatic disease such as pain response, time to progression and progression-free survival, while appealing endpoints that may highlight the clinical benefit of novel agents, have been difficult to define rigorously and have not yet demonstrated adequate surrogacy for overall survival. SUMMARY: The measures of response highlighted in this review, if validated, may improve the current evaluation of novel agents in phase II settings and the potential accelerated approval of these agents.     

Advances in the management of recurrent or metastatic squamous cell carcinoma of the head and neck

Most patients with locally advanced squamous cell carcinoma of the head and neck (SCCHN) undergo definitive therapy, yet locoregional recurrence and metastasis are common. Most patients ultimately require systemic treatment. Platinum/5‐fluorouracil (5‐FU) has been the standard of care for patients with good performance status (median survival, 6–8 months). Cetuximab, a monoclonal antibody against epidermal growth factor receptor (EGFR), significantly improved median survival in combination with platinum/5‐FU compared with chemotherapy alone, establishing it as a new standard for patients with recurrent or metastatic disease. Cetuximab is also active in platinum‐refractory disease. Ongoing trials are exploring other EGFR inhibitors as well as the use of biologic agents in combination (eg, cetuximab + bevacizumab). Predictive biomarkers may help personalize therapy for SCCHN, and it is unclear whether the favorable prognostic effect of p16 or human papillomavirus in locally advanced oropharyngeal cancer is relevant for advanced disease. Head Neck, 2013     

Drug insight: Use of docetaxel in prostate and urothelial cancers

Taxanes have emerged as a potent class of chemotherapeutic agents in many malignancies, with two taxanes now in clinical use. Their mechanism of action against tumor cells is by alteration of microtubule dynamics, which causes cell-cycle arrest during mitosis. Docetaxel binds to the microtubules with a higher affinity than paclitaxel, and over a broader range of cell-cycle activities. It has also been shown to promote apoptosis via BCL2 phosphorylation. In hormone-refractory prostate cancer, docetaxel has been studied as both a single agent and in combination with estramustine, and in different treatment schedules, with demonstrated efficacy. Two phase III trials have confirmed a survival benefit, making docetaxel the first chemotherapy agent with proven efficacy against prostate cancer. In urothelial cancer, docetaxel has demonstrated activity and has been investigated as a single agent and in combination regimens. A phase III trial comparing docetaxel and cisplatin to methotrexate, vinblastine, doxorubicin, and cisplatin was inferior when evaluating response rates and overall survival. More recent phase II trials combining docetaxel with two additional agents have shown promise, but confirmatory trials are needed.     

Recent strategies for the use of paclitaxel in the treatment of urological malignancies

Paclitaxel, a natural anticancer drug, has gained widespread acceptance as an active broad-spectrum antitumor agent, including its use in urological malignancies, particularly urothelial tract cancer and testicular cancer. The mechanism of action, based on the premature stabilization of the microtubule assembly with disruption of the cytoskeletal framework, is completely different from those of DNA-damaging agents, e.g., cisplatin and ifosfamide. As a single agent, paclitaxel is one of the most active drugs in metastatic bladder cancer, with an overall response rate of 40–50% being obtained in previously untreated patients. These promising single-agent results have prompted the use of combination regimens including, in particular, cisplatin and paclitaxel. A high degree of activity for the cisplatin-paclitaxel combination as reflected by responses in 50–80% of patients, including a substantial number of complete responses (>30%), has been identified. The role of other agents such as vinorelbine, methotrexate, 5-fluorouracil, or ifosfamide as additions to this two-drug combination currently remains open. The combination of paclitaxel plus ifosfamide or vinorelbine in the absence of a platinum derivative has yielded rather disappointing results. Of particular interest may be the combination of paclitaxel and carboplatin. Both drugs can be given to patients with impaired renal function. Overall response rates of 45–60% have been reported in phase II studies. The so-called platelet-sparing effect of paclitaxel given in combination with carboplatin has resulted in a surprisingly low frequency of myelotoxicity, particularly thrombocytopenia. The combination of paclitaxel with carboplatin is being compared in an ongoing trial against the current standard MVAC regimen (methotrexate/vinblastine/Adriamycin/cisplatin) in patients with metastatic disease. Furthermore, the activity of paclitaxel-based combinations is currently being explored in the neoadjuvant setting in phase II studies, and the potential for the combination with the other new promising agent – gemcitabine – will be evalutated in a phase I setting. In prostate cancer, estramustine phosphate is widely used as palliative treatment for patients with hormone-refractory disease. In vitro synergistic activity has been observed between estramustine and paclitaxel in prostate-cancer cell lines, although paclitaxel has not demonstrated single-agent activity in patients with hormone-refractory prostate cancer. In clinical trials the combination of the two agents was associated with increased gastrointestinal toxicity. The addition of etoposide as a third drug has yielded prostate-specific antigen (PSA)-response rates of >50%, but data on quality of life and survival time have not been reported for these combinations. A true clinical role for paclitaxel in prostate cancer has therefore not been established. Paclitaxel has finally demonstrated single-agent activity in relapsed and/or cisplatin-refractory testicular cancer in recent phase II trials, indicating different mechanisms of resistance to cisplatin and paclitaxel. These results have formed the rationale for the introduction of paclitaxel as part of combination chemotherapy regimens in patients with relapsed but chemosensitive testicular cancer. Preliminary results demonstrate that paclitaxel can be safely included into these conventional-dose combination regimens. When it is used prior to high-dose chemotherapy, sufficient numbers of peripheral blood stem cells (PBSCs) for high-dose therapy can be collected. The final role of paclitaxel in risk-adapted chemotherapeutic strategies in testicular cancer is not defined, but it appears that paclitaxel-based combinations can achieve a substantial response rate in patients with relapsed disease.     

Dendritic cell vaccines for the treatment of prostate cancer

Advanced prostate cancer remains a disease with few options beyond palliation. Over the past few decades, our understanding of immunology has led to the development of novel therapies for the treatment of many malignancies, including prostate cancer. These generally aim to induce T-cell responses against tumor specific antigens to both reduce tumor mass and potentially avoid relapse. One promising technique is to use autologous dendritic cells, the most potent antigen presenting cell. These can be loaded ex vivo with a given antigen and subsequently injected back into the patient to stimulate the desired effect. Recent trials using these techniques have shown promise in extending survival in patients with prostate cancer. This review will discuss relevant biology behind dendritic cell therapy and highlight the key trials found in the literature.     

Extracellular matrix degradation enzymes: important factors in liver metastasis of colorectal cancer and good targets for anticancer metastatic therapy

Extracellular matrix (ECM) degradation enzymes, such as matrix metalloproteinases (MMPs) and plasminogen activators, are important factors in cancer invasion and metastasis, because invasion and metastasis of cancer cells require destruction of mesenchymal collagen or the endothelial basement membrane. Moreover, recent studies have shown that ECM degradation enzymes play important roles in cancer cell proliferation, cancer escape from the immune system, and tumor angiogenesis. ECM degradation enzymes, especially some MMPs, are good targets for anticancer metastatic therapy. Numerous anti-MMP agents have been developed and phase III clinical trials in advanced cancers ongoing. Successful control of MMPs induced by cancer cells will prevent liver metastasis of colorectal cancer.