Cell signaling molecules as drug targets in lung cancer: an overview

PURPOSE OF REVIEW

Lung being one of the vital and essential organs in the body, lung cancer is a major cause of mortality in the modern human society. Lung cancer can be broadly subdivided into nonsmall cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Although NSCLC is sometimes treated with surgery, the advanced and metastatic NSCLC and SCLC usually respond better to chemotherapy and radiation. The most important targets of these chemotherapeutic agents are various intracellular signaling molecules. The primary focus of this review article is to summarize the description of various cell signaling molecules involved in lung cancer development and their regulation by chemotherapeutic agents.

RECENT FINDINGS

Extensive research work in recent years has identified several cellular signaling molecules that may be intricately involved in the complexity of lung cancer. Some of these cell signaling molecules are epidermal growth factor receptors, vascular endothelial growth factor receptors, mammalian target of rapamycin, mitogen-activated protein kinase phosphatase-1, peroxisome proliferator-activated receptor-gamma, matrix metalloproteinases and receptor for advanced glycation end-products.

SUMMARY

The present review will strengthen our current knowledge regarding the efficacy of the above-mentioned cell signaling molecules as potential beneficial drug targets against lung cancer.

Optimization of dosing for EGFR-mutant non-small cell lung cancer with evolutionary cancer modeling

Non-small cell lung cancers (NSCLCs) that harbor mutations within the epidermal growth factor receptor (EGFR) gene are sensitive to the tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib. Unfortunately, all patients treated with these drugs will acquire resistance, most commonly as a result of a secondary mutation within EGFR (T790M). Because both drugs were developed to target wild-type EGFR, we hypothesized that current dosing schedules were not optimized for mutant EGFR or to prevent resistance. To investigate this further, we developed isogenic TKI-sensitive and TKI-resistant pairs of cell lines that mimic the behavior of human tumors. We determined that the drug-sensitive and drug-resistant EGFR-mutant cells exhibited differential growth kinetics, with the drug-resistant cells showing slower growth. We incorporated these data into evolutionary mathematical cancer models with constraints derived from clinical data sets. This modeling predicted alternative therapeutic strategies that could prolong the clinical benefit of TKIs against EGFR-mutant NSCLCs by delaying the development of resistance.

Maintenance therapy in advanced non-small cell lung cancer: evolution, tolerability and outcomes

Non-small cell lung cancer (NSCLC) is the leading cause of cancer death in the industrialized world. Despite significant progress in early stage disease, survival rates for advanced disease remain low. Maintenance therapy is a treatment strategy that has been investigated extensively in NSCLC and has been the subject of considerable recent debate. Options for maintenance include continuing the initial combination chemotherapy regimen, continuing only single agent chemotherapy ('continuation maintenance') or introducing a new agent ('switch' maintenance therapy). Therapies that have been studied in this setting in randomized trials to date include chemotherapy, molecularly targeted agents and immunotherapy approaches. Following the development of multiple new agents that show activity in NSCLC, and have a tolerable side-effect profile, there has been increasing interest in utilizing them to maintain response to initial therapy after treatment with platinum-based doublets. Despite considerable controversy, it has become an acceptable treatment paradigm. Here, we briefly outline the evolution of this treatment paradigm and examine which subgroups of patients are most likely to benefit.

Bevacizumab: current updates in treatment

PURPOSE OF REVIEW

Drugs targeting angiogenesis are rapidly being incorporated into cancer treatment regimens. Bevacizumab was the first antiangiogenesis agent to gain approval by the Food and Drug Administration and is now approved for use in five tumor types. This brief review highlights important recent advances in our understanding of bevacizumab and the patient populations in whom it may be most beneficial.

RECENT FINDINGS

Results from early studies that led to approval of bevacizumab for use in metastatic colorectal cancer and metastatic lung cancer have been confirmed. Although bevacizumab does not appear to prolong disease-free survival in the adjuvant treatment of colorectal cancer, phase II results in the neoadjuvant treatment of colorectal cancer and breast cancer are encouraging. It may also have a role in maintenance therapy of colorectal cancer and nonsmall cell lung cancer. Bevacizumab is an important agent in the treatment of recurrent glioma. Although the safety profile of bevacizumab in combination with cytotoxic agents has not changed significantly, there may be excess risk associated with combined angiogenesis blockade.

SUMMARY

Bevacizumab has efficacy in a wide variety of cancers and fairly predictable toxicities. In addition to further exploration of the benefits of bevacizumab in other tumor types, future research should focus on integration of biomarkers into patient selection and treatment.

Maintenance and consolidation therapy in patients with unresectable stage III/IV non-small cell lung cancer

Lung cancer remains the most common cancer and the leading cause of cancer-related mortality. Despite continuing improvements in chemoradiotherapy regimens and the recent clinical validation of particular agents as maintenance treatments in advanced disease, there remains an unmet need for new therapies with clinically proven value in the treatment of unresectable stage III NSCLC. Studies are under way to determine whether the use of anticancer vaccines may be an effective strategy in the treatment of NSCLC.

Globally, lung cancer is the leading cause of cancer-related mortality. Current chemotherapy combinations for the first-line treatment of advanced disease (stage IIIB with malignant pleural effusion/stage IV) and chemoradiotherapy regimens for the treatment of unresectable locally advanced disease (stage IIIA and IIIB without malignant pleural effusion) appear to have reached an efficacy plateau. The addition of new compounds including targeted agents to standard first-line cytotoxic doublets, administered concurrently and/or as maintenance therapy in patients who have not experienced disease progression after such treatment, has been shown to improve efficacy beyond this plateau in patients with advanced disease. However, to date, such approaches have been less successful in the treatment of patients with unresectable locally advanced stage III disease. The purpose of this review is to summarize the data from recent randomized phase III studies involving agents administered as maintenance or consolidation therapy in the treatment of unresectable stage III/IV non-small cell lung cancer (NSCLC). A possible alternative approach to the use of cytotoxic or molecularly targeted agents in this setting is the administration of therapeutic anticancer vaccines, which are designed to stimulate a host immunological response against the tumor. Current data in relation to the potential of vaccine therapy for NSCLC are therefore also reviewed, with a particular focus on belagenpumatucel-L and L-BLP25 vaccines, which are currently undergoing phase III evaluation as maintenance therapies in patients with unresectable stage III/IV NSCLC who have tumor control following first-line therapy.

First-line erlotinib and bevacizumab in patients with locally advanced and/or metastatic non-small-cell lung cancer: a phase II study including molecular imaging

BACKGROUND

Both bevacizumab and erlotinib have clinical activity in non-small-cell lung cancer (NSCLC). Preclinical data suggest synergistic activity.

PATIENTS AND METHODS

Chemonaive patients with stage IIIb or IV non-squamous NSCLC were treated with bevacizumab 15 mg/kg every 3 weeks and erlotinib 150 mg daily until progression. Primary end point was non-progression rate (NPR) at 6 weeks. Tumor response was measured with computed tomography, 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG-PET) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). KRAS and EGFR mutations were assessed in tumor samples.

RESULTS

Forty-seven patients were included. Median follow-up was 15.2 months. NPR at 6 weeks was 75%. Median progression-free survival (PFS) was 3.8 [95% confidence interval (CI) 2.3-5.4] months and median overall survival (OS) was 6.9 (95% CI 5.5-8.4) months. Toxicity was mainly mild. The presence of KRAS (n = 10) or EGFR mutations (n = 5) did not influence outcome. After 3 weeks of treatment, >20% decrease in standard uptake value as measured with positron emission tomography predicted for longer PFS (9.7 versus 2.8 months; P = 0.01) and >40% decrease in K(trans) as assessed by DCE-MRI did not predict for longer PFS.

CONCLUSIONS

First-line treatment with bevacizumab and erlotinib in stage IIIb/IV NSCLC resulted in an NPR of 75%. OS was however disappointing. Early response evaluation with FDG-PET is the best predictive test for PFS.

Targeted therapy in non-small-cell lung cancer--is it becoming a reality?

Treatment outcomes in advanced or metastatic non-small-cell lung cancer (NSCLC) remain unsatisfactory, with low long-term survival rates. Palliative chemotherapy offers a median survival not exceeding 1 year. To date, various combinations of cytotoxic drugs have not improved treatment results beyond what has been observed with platinum doublets. By contrast, molecular targeted drugs may block important pathways that drive cancer progression and achieve long-term disease control. Conflicting results have demonstrated marginal benefit with EGFR inhibitors, anti-EGFR monoclonal antibodies and antiangiogenic strategies in unselected populations of patients with advanced NSCLC. However, patients with an EGFR mutation are likely to respond to agents that target this gene. Novel targeted therapies that interfere with insulin-like growth factor 1 receptor, or the EML4-ALK fusion protein have shown promising activity. Aberrations in other key signaling pathways and molecules, such as RAS/RAF/MEK, PI3K/AKT/mTOR, or MET kinase, have been identified as crucial targets, especially in resistant patients. Novel drugs aimed at these abnormalities are already in the clinic. This Review outlines the current state-of-the-art research for targeted therapy in NSCLC.

Targeting angiogenesis with multitargeted tyrosine kinase inhibitors in the treatment of non-small cell lung cancer

It has been >35 years since the link between angiogenesis and the growth of tumors was first reported. Targeting angiogenesis became feasible with the availability of bevacizumab, an anti-vascular endothelial growth factor monoclonal antibody. Initial studies revealed that the combination of bevacizumab and chemotherapy led to longer overall survival times than with chemotherapy alone in patients with advanced colorectal cancer. Since then, drug development strategies have added small molecule tyrosine kinase inhibitors to the panel of antiangiogenic agents under evaluation; data from numerous trials are now available. The challenge now is to identify the optimal antiangiogenic agent for specific patient groups and to understand not only the mechanistic differences between agents, but also the variability in their antitumor activity across different tumor types and their differing side-effect profiles. As in other solid tumors, angiogenesis contributes to the development of non-small cell lung cancer (NSCLC), and this review summarizes the role of angiogenesis in this disease. We review the current developmental status of antiangiogenic tyrosine kinase inhibitors (including vandetanib, sunitinib, axitinib, sorafenib, vatalanib, and pazopanib) in NSCLC and conclude by briefly discussing the need for optimal patient selection and potential future directions.