Schedule-Dependent Interaction between the Proteosome Inhibitor Bortezomib and the EGFR-TK Inhibitor Erlotinib in Human Non-small Cell Lung Cancer Cell Lines

INTRODUCTION

Both erlotinib (E) and bortezomib (B) have shown single-agent activity in patients with non-small cell lung cancer. We studied the combination of these two novel biologic agents in vitro using a panel of non-small cell lung cancer cell lines.

METHODS

The growth inhibitory effect of E and B were determined by MTT assay on seven non-small cell lung cancer cell lines. The data obtained from the growth inhibition assay in response to the combination of E and B were subject to isobologram analysis. The effects of each individual drug as well as combination in different sequences on cell cycle and apoptosis were determined by flow cytometry.

RESULTS

Two of seven cell lines are sensitive to E. However, B has narrower range of cytotoxicity. The combination is neither synergistic nor additive in two of four cell lines tested. In H358 bronchoalveolar cell lines, the combination is more active than either agent alone. E causes G1 cell cycle arrest and B causes G2/M cell cycle arrest. In sequential studies, 24-hour previous exposure to E causes G1 arrest and abrogates the cytotoxic effect of B. This is observed in both E-sensitive as well as E-resistant cells and is accompanied by an increase in cell survival and a decrease in apoptosis.

CONCLUSIONS

The combination of E and B is neither additive nor synergistic in two of four cell lines tested. In H358 bronchoalveolar cell, the combination is more active than either agent alone. The schedule-dependent antagonistic effect of E pre-exposure was observed. E pre-exposure causes G1 cell cycle arrest and abrogates the activity of B. Further in vivo studies of this combination are warranted.

Bortezomib, but not cisplatin, induces mitochondria-dependent apoptosis accompanied by up-regulation of noxa in the non-small cell lung cancer cell line NCI-H460

Defects in the apoptotic machinery may contribute to chemoresistance of non-small cell lung cancer (NSCLC) cells. We have previously showed a deficiency in mitochondria-dependent caspase-9 activation in NSCLC H460 cells after exposure to cisplatin, a drug widely used to treat NSCLC. Here we show that, unlike cisplatin, the novel anticancer agent bortezomib efficiently induces caspase-9 activation and apoptosis in H460 cells. A comparative analysis of molecular events underlying cell death in bortezomib-treated versus cisplatin-treated H460 cells revealed that bortezomib, but not cisplatin, caused a rapid and abundant release of cytochrome c and Smac/DIABLO from mitochondria. This was associated with a marked increase in levels of the BH3-only proapoptotic protein Noxa and the antiapoptotic protein Mcl-1. Taken together, our data show that bortezomib, by promoting a proapoptotic shift in the levels of proteins involved in mitochondrial outer-membrane permeabilization, is a potent activator of the mitochondrial pathway of apoptosis in NSCLC cells. Our preclinical results support further investigation of bortezomib-based therapies as a possible new treatment modality for NSCLC.

The emerging role of targeted therapy for hematologic malignancies: update on bortezomib and tipifarnib

As therapy for hematologic malignancy evolves, new regimens and novel agents that target specific cellular processes allow a more optimistic prognosis for many patients. Bortezomib and tipifarnib are two new, targeted treatments for hematologic malignancies. Bortezomib, a proteasome inhibitor, has shown impressive efficacy in patients with relapsed multiple myeloma and as initial treatment, including before autologous stem cell transplantation. It has been studied as monotherapy and in combination with standard treatments such as dexamethasone, and with newer agents such as the immunomodulators thalidomide and lenalidomide; response is encouraging, even in patients who have relapsed after previously receiving components of a regimen as single agents. Bortezomib is generally well tolerated, including in combination with novel and conventional agents. Tipifarnib is a specific inhibitor of farnesyltransferase. Clinical trials in patients with high-risk acute leukemias and myelodysplastic syndromes have demonstrated good efficacy with tipifarnib. Continued investigation with these new, targeted treatments will further define their use as treatment options in patients with hematologic cancer.

Recent advances in targeted therapy for non-small cell lung cancer

Non-small-cell lung cancer (NSCLC) is characterized by wide molecular heterogeneity. In recent years, novel agents that target specific, aberrant molecular pathways in NSCLC have been under rigorous evaluation. Erlotinib, an inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase, improves survival for advanced NSCLC patients who progressed following one or two prior chemotherapy regimens. Novel molecular predictive markers, such as EGFR mutations and gene amplification, are at present under evaluation to select patients for therapy with erlotinib. Another area of progress is the recent demonstration that bevacizumab, a monoclonal antibody against the vascular endothelial growth factor (VEGF), extended survival when administered in combination with chemotherapy for patients with non-squamous NSCLC. Promising anticancer activity has also been noted with agents that inhibit the VEGF receptor tyrosine kinase in patients with advanced NSCLC. Inhibitors of the proteosomal complex, histone deacetylase, mammalian target of rapamycin pathway, and other growth factor receptor-mediated signaling are under investigation for treatment of NSCLC. These developments have paved the way for a new era of tailor-made therapies based on clinical or molecular/genetic profiles in the treatment of NSCLC. This article reviews the recent advances in targeted therapy of advanced NSCLC.

Novel targeted therapies for non-small cell lung cancer

Targeted therapies will advance the treatment of NSCLC as we improve our understanding of the underlying biology of NSCLC and enhance our ability to clinically target the optimal therapy to an individual's cancer. Ongoing translational research including tissue arrays, genomic, and proteomic studies will help to identify clinically useful biomarkers that will allow further classification of NSCLC and may allow accurate prediction of response to specific chemotherapeutic regimens. Advances in targeted therapy in NSCLC are already yielding exciting results, and promises to become an increasingly important adjunct to surgical management of NSCLC.

The proteasome inhibitor bortezomib acts differently in combination with p53 gene transfer or cytotoxic chemotherapy on NSCLC cells

In this report, the effects of a combined treatment with the proteasome inhibitor bortezomib and either a recombinant adeno-associated virus type 2 (rAAV-2)-mediated p53 gene transfer or chemotherapeutic agents, docetaxel and pemetrexed, were tested on p53 positive and p53negative non-small cell lung cancer (NSCLC) cell lines. The combination of bortezomib and rAAV-p53 led to a significant synergistic inhibition of cell growth between 62-82% depending on the p53 status of the cell line and drug concentration. Surviving cells of the combined treatment showed a significant reduced ability to form colonies. Enhanced cell toxicity was associated with a 5.3-14.4-fold increase of the apoptotic rate and intracellular p53 level up to 50.4% following vector-mediated p53 restoration and bortezomib treatment. In contrast, an antagonistic effect on tumor cell growth and colony formation was observed for the combination of bortezomib and docetaxel or pemetrexed as a reduction of cell growth between 31 and 48% was found in comparison to 50% using the single agents. Lower cytotoxic effects were associated with significantly reduced apoptosis and an increase of clonogenic growth. The observed antagonistic effects between bortezomib and docetaxel or pemetrexed might influence clinical trials using these compounds. Conversely, p53 restoration and bortezomib treatment led to enhanced, synergistic tumor cell toxicity.

Recent developments in the chemotherapeutic options for nonsmall cell lung cancer

Lung cancer is one of the leading causes of cancer deaths in the developed world. It is grossly divided into small cell and nonsmall cell types. Depending on the stage at diagnosis, the principal means of treating nonsmall cell lung cancer are surgery, chemotherapy and/or radiotherapy. However, even when it is diagnosed at an early stage, the progression-free and overall survival rates have been disappointing compared with other cancers. In recent years, there have been a number of developments in the chemotherapeutic options for nonsmall cell lung cancer. The aim of this review is to summarize these developments, in a stage-specific manner, with respect to both standard chemotherapy and also the newer targeted therapies.

Bortezomib for multiple myeloma

The ubquitin-proteasome pathway is a key regulator of homeostasis within cells, degrading misfolded or redundant proteins, and also those involved in mediating transcription, cell-cycle progression and apoptosis. Inhibition of the 26S proteasome results in accumulation of such proteins and ultimately leads to cell death. Malignant cells are more susceptible to proteasome inhibition due to their higher proliferation rates, protein production and their dependence on anti-apoptotic molecules for cell survival. Bortezomib has recently gained European Commission approval for the treatment of relapsed multiple myeloma on the basis of clinical trials demonstrating its efficacy, tolerability and superiority to high-dose dexamethasone. Preclinical data demonstrates the ability to synergise with other chemotherapeutic agents and overcome drug resistance, and hence combination studies are underway. This review describes the pharmacology, toxicity, preclinical and clinical activity of bortezomib, predominantly in the setting of multiple myeloma.

The second annual symposium on the future of lung cancer: a translational focus

Lung cancer continues to be a leading cause of death in the US, and in its most advanced stages remains incurable. Cytotoxic chemotherapies have been the standard of care for the treatment of unresectable disease. However, recent advances in the development of epidermal growth factor receptor (EGFR) inhibitors have led the way to a new generation of targeted biological agents. During the second annual symposium entitled 'the future of lung cancer: a translational focus', which was sponsored by the Physician s Education Resource, new strategies for the treatment of lung cancer were discussed. Besides the role of EGFR inhibitors, potential targets include the angiogenesis pathway; other growth factor pathways, such as phosphoinositol-3 kinase/Akt and Raf-MEK; the 26S proteasome, the histone deacetylase mechanism; and the TNF-related apoptosis-inducing factor receptors. Agents that are directed against these targets are all in varying stages of clinical development. As more is learned about their mechanisms of action and clinical spectrum of activity, the author anticipates their incorporation into novel regimens with enhanced activity against lung cancer.

Salvage Therapy for Advanced Non‐Small Cell Lung Cancer: Factors Influencing Treatment Selection

Novel chemotherapies and molecularly targeted agents have improved outcomes for patients with advanced non-small cell lung cancer (NSCLC). Several efficacious regimens are available, which allows for selection of therapy based on factors such as schedule, toxicity profile, patient-specific needs, and individual preferences of the patient. Treatment guidelines recommend platinum-based chemotherapy first line for patients with a good performance status. These regimens offer a modest survival advantage over best supportive care. The role of targeted biologic agents in this setting is being assessed in phase II trials. Results to date show promising activity and tolerability. Erlotinib, docetaxel, and pemetrexed are all approved for patients who progress following one prior regimen for advanced NSCLC. These agents have different tolerability profiles and routes of administration but appear to have similar effects on tumor response and survival, though comparative trials are required to confirm this. Based on the results of a phase III trial, erlotinib is also recommended for third-line use in patients with NSCLC. Identifying predictive markers of clinical response to therapy may provide an opportunity to better select patient subsets appropriate for specific treatment. Recent data have linked various clinical characteristics and biologic markers with outcome to HER-1/EGFR-targeted agents. However, many of these studies are retrospective and based on small patient numbers, and there is evidence of broad benefit across diverse patient subgroups with erlotinib. Prospective, randomized trials are required to validate potential predictive markers fully before they are applied to clinical practice.

Second- and third-line treatments in non-small cell lung cancer

Slow but steady progress has been made in the treatment of advanced non-small cell lung cancer. For first-line therapy, multiple chemotherapy combination therapies can extend survival and improve quality of life. And recently, for the first time ever, a noncytotoxic agent, the antivascular endothelial growth factor antibody bevacizumab, has been shown to improve survival when added to chemotherapy. Striking improvements have also been made in second-line treatment. In August 2004, only one agent was US Food and Drug Administration (FDA) approved in this setting, docetaxel, but by the beginning of 2005, two more were available, pemetrexed and erlotinib. All three of these drugs can significantly benefit patients, with 1-year survival in excess of 30%. Choosing between the three agents can be challenging, and this review focuses on the toxicity differences and predictors of response that can help guide this decision. Docetaxel and pemetrexed, both traditional intravenous cytotoxins, are excellent options for patients who have shown some response to first-line chemotherapy, but at this time, no other means exist to determine likelihood of response. When choosing between the two, pemetrexed causes significantly less neutropenia than does docetaxel, at least on the standard every-3-week regimen. With erlotinib, an oral epidermal growth factor receptor (EGFR) inhibitor, there are factors that can predict for response, including little or no smoking history, and adenocarcinoma histology. Therefore, patients who fit these characteristics are good candidates for second-line erlotinib. However, the relationship between response to erlotinib and improved survival remains unclear, and several laboratory analyses that may help further, such as evaluation of EGFR gene copy number, are still under development. Although erlotinib is the only FDA-approved option currently available for third-line therapy, many patients with good performance status may benefit from third-line therapy and beyond. In addition to the approved second-line options, other single-agent chemotherapies to consider for treatment beyond second-line are gemcitabine, irinotecan, and oral topotecan. Many new drugs, including bevacizumab, ZD6474 (AstraZeneca, Wilmington, DE), sorafenib, cetuximab, paclitaxel poliglumex, epothilones, and others, alone or in combination with traditional agents, are currently undergoing investigation and hold great promise.

Novel Combinations with Docetaxel in the Treatment of Non–Small-Cell Lung Cancer

The treatment of advanced-stage lung cancer continues to be challenging. Cytotoxic chemotherapy doublets have modestly improved survival and have emphasized more quality of life issues. Many novel targeted agents are in clinical development and could have potential to treat patients with lung cancer whose tumors are refractory to standard cytotoxic regimens. Targeting the epidermal growth factor receptor as well as the vascular endothelial growth factor pathways appears promising. Combining these targeted agents with chemotherapy might help improve overall efficacy. Docetaxel is an active chemotherapeutic agent that has been studied in combination with multiple biologic agents. With continued study, optimizing these combinations for specific patient populations will be the key to improving overall efficacy.

American Society of Clinical Oncology 41st annual meeting

For many years the annual meeting of the American Society of Clinical Oncology (ASCO) has been the premier meeting in clinical oncology, and one that is closely scrutinised by Wall Street and international investors because of the economic significance of cancer therapies to the pharmaceutical and biotechnology industries. The area of biologicals and targeted therapies exploded in the late 1990s after the blockbuster results with the monoclonal antibody rituximab in the treatment of lymphoma. Although historically a somewhat conservative organisation that is still closely tied to classical cytotoxic chemotherapy, ASCO has been able to integrate various areas of biological therapy into its scope of clinical activity. Although ASCO still has 'American' in its title, it is really the 'International' Society of Clinical Oncology, as reflected by the attendance at this year's meeting by approximately 30,000, with approximately two-thirds attending from outside the US. There were 9708 abstracts published in conjunction with the meeting, 86 of which are referenced in this review. There were 10 papers chosen for plenary presentations and many other key papers were presented at other oral abstract sessions and poster discussion session that were organised by tumour type. In addition to key papers submitted by specific tumour type, for this year's meeting there were 103 abstracts published in the session entitled 'Developmental Therapeutics: Immunotherapy', and 218 in the session entitled Developmental Therapeutics: Molecular Targets', for a total of 321 biological therapy abstracts compared with only 125 abstracts for the session entitled 'Developmental Therapeutics: Cytotoxic Therapy'. This meeting review is organised by biotherapy modality rather than tumour type.