Randomized phase II Study of carboplatin and etoposide with or without the bcl-2 antisense oligonucleotide oblimersen for extensive-stage small-cell lung cancer: CALGB 30103

Targeted therapies in small cell lung cancer: a review

Small cell lung cancer (SCLC) is an aggressive form of lung cancer that is characterized by a rapid doubling time, early onset of dissemination and high sensitivity to chemotherapy. Despite the potential for cure in patients with limited disease with concurrent chemoradiation and an initial good response to chemotherapy in extensive disease, there is a high chance of disease relapse with an overall poor median survival for both stages. With increasing translational research and a better understanding of the molecular basis of cancer, a number of molecular targets have been identified in various preclinical studies. This review summarizes potentially viable targets and new agents that have been developed and employed in recent, ongoing and future clinical trials to attempt to improve clinical outcomes in this disease.

The molecular and cellular biology of lung cancer: identifying novel therapeutic strategies

INTRODUCTION

Lung cancer is the commonest fatal malignancy in the developed world. Survival rates for lung cancer have not changed significantly over the past 30 years. Sources of data This report is a systematic review of the literature on our current understanding of lung cancer biology. Searches were carried out using PUBMED. 1990-2010.

AREAS OF AGREEMENT

A concerted effort to reduce cigarette smoking and nicotine addiction is required. A better understanding of the biology of lung cancer will lead to the identification of earlier diagnostic markers and improved therapy.

AREAS OF CONTROVERSY

How chronic inflammatory disorders such as COPD and lung fibrosis contribute to lung cancer development is incompletely understood.

GROWING POINTS

Developing novel biological agents to target lung cancer. New microarray-based technologies provide new methods for predicting prognosis and response to treatment.

AREAS TIMELY FOR DEVELOPING RESEARCH

Developing strategies to target lung cancer stem cells may provide a novel approach for treating drug resistant disease.

New advances in the second-line treatment of small cell lung cancer

Lung cancer is the leading cause of cancer-related death in the U.K., with small cell histology accounting for 15%-20% of cases. Small cell lung cancer (SCLC) is initially a chemosensitive disease, but relapse is common, and in this group of patients it remains a rapidly lethal disease with a particularly poor prognosis. The choice of second-line chemotherapy for patients with relapsed SCLC has been an area of difficulty for oncologists, and until recently there was no randomized evidence for its use over best supportive care (BSC). Topotecan is currently the only drug licensed in Europe and the U.S. for this indication, having been shown in a phase III trial to lead to longer overall survival and better quality of life than with BSC. In this article, we review the current evidence for the use of second-line cytotoxic therapy and also the emerging role of novel agents and targeted therapies in this setting. In particular, we explore the role of the Bcl-2 protein family, which are key regulators of mitochondrial apoptosis and are implicated in resistance to anticancer therapies. SCLC overexpresses antiapoptotic members of the Bcl-2 family in approximately 80% of cases. Several Bcl-2 inhibitors, including obatoclax, are currently entering clinical trials in SCLC and are an exciting area of drug development in the relapsed setting.

Signalling pathways in prostate carcinogenesis: potentials for molecular-targeted therapy

Prostate cancer represents a major health issue and its incidence is rising globally. In developed countries, prostate cancer is the most frequently diagnosed cancer and the second most common cause of death from cancer in men. Androgen deprivation reduces tumour activity in approx. 80% of patients with advanced disease, but most tumours relapse within 2 years to an incurable hormone-resistant state. Even for patients with early disease at the time of diagnosis, a proportion of patients will unfortunately develop relapsed disease following radical therapy. Treatment options for patients with hormone-resistant prostate cancer are very limited and, even with toxic therapy, such as docetaxel, the life expectancy is only improved by a median of 2 months. Advances in molecular oncology have identified key signalling pathways that are considered to be driving events in prostate carcinogenesis. The activation of multiple signalling pathways increases further the possibility of cross-talk among 'linear' signalling cascades. Hence signalling networks that may incorporate distinct pathways in prostate cancer, particularly in hormone-resistant disease, are increasingly appreciated in drug development programmes. With the development of potent small-molecule inhibitors capable of specifically suppressing the activities of individual 'linear' cascades, it may be that, by combining these agents as guided by the molecular signature of prostate cancer, a more efficient therapeutic regime may be developed. Therefore the present review focuses on evidence of abnormal signalling in prostate cancer and the potential of these targets in drug development, and incorporates key findings of relevant clinical trials to date.

The HDAC inhibitor panobinostat (LBH589) inhibits mesothelioma and lung cancer cells in vitro and in vivo with particular efficacy for small cell lung cancer

Lung cancer is the leading cause of cancer deaths in the United States. Current therapies are inadequate. Histone deacetylase inhibitors (HDACi) are a recently developed class of anticancer agents that cause increased acetylation of core histones and nonhistone proteins leading to modulation of gene expression and protein activity involved in cancer cell growth and survival pathways. We examined the efficacy of the HDACi panobinostat (LBH589) in a wide range of lung cancers and mesotheliomas. Panobinostat was cytotoxic in almost all 37 cancer cell lines tested. IC(50) and LD(50) values were in the low nmol/L range (4-470 nmol/L; median, 20 nmol/L). Small cell lung cancer (SCLC) cell lines were among the most sensitive lines, with LD(50) values consistently <25 nmol/L. In lung cancer and mesothelioma animal models, panobinostat significantly decreased tumor growth by an average of 62% when compared with vehicle control. Panobinostat was equally effective in immunocompetent and severe combined immunodeficiency mice, indicating that the inhibition of tumor growth by panobinostat was not due to direct immunologic effects. Panobinostat was, however, particularly effective in SCLC xenografts, and the addition of the chemotherapy agent etoposide augmented antitumor effects. Protein analysis of treated tumor biopsies revealed elevated amounts of cell cycle regulators such as p21 and proapoptosis factors, such as caspase 3 and 7 and cleaved poly[ADP-ribose] polymerase, coupled with decreased levels of antiapoptotic factors such as Bcl-2 and Bcl-X(L). These studies together suggest that panobinostat may be a useful adjunct in the treatment of thoracic malignancies, especially SCLC.

Bcl-2 inhibitors: targeting mitochondrial apoptotic pathways in cancer therapy

Defects in apoptotic pathways can promote cancer cell survival and also confer resistance to antineoplastic drugs. One pathway being targeted for antineoplastic therapy is the anti-apoptotic B-cell lymphoma-2 (Bcl-2) family of proteins (Bcl-2, Bcl-XL, Bcl-w, Mcl-1, Bfl1/A-1, and Bcl-B) that bind to and inactivate BH3-domain pro-apoptotic proteins. Signals transmitted by cellular damage (including antineoplastic drugs) or cytokine deprivation can initiate apoptosis via the intrinsic apoptotic pathway. It is controversial whether some BH3-domain proteins (Bim or tBid) directly activate multidomain pro-apoptotic proteins (e.g., Bax and Bak) or act via inhibition of those anti-apoptotic Bcl-2 proteins (Bcl-2, Bcl-XL, Bcl-w, Mcl-1, Bfl1/A-1, and Bcl-B) that stabilize pro-apoptotic proteins. Overexpression of anti-apoptotic Bcl-2 family members has been associated with chemotherapy resistance in various human cancers, and preclinical studies have shown that agents targeting anti-apoptotic Bcl-2 family members have preclinical activity as single agents and in combination with other antineoplastic agents. Clinical trials of several investigational drugs targeting the Bcl-2 family (oblimersen sodium, AT-101, ABT-263, GX15-070) are ongoing. Here, we review the role of the Bcl-2 family in apoptotic pathways and those agents that are known and/or designed to inhibit the anti-apoptotic Bcl-2 family of proteins.

Phase I/II study of G3139 (Bcl-2 antisense oligonucleotide) in combination with doxorubicin and docetaxel in breast cancer

PURPOSE

Preclinical data showed enhancement of breast cancer cell death when G3139 was combined with anthracyclines and taxanes. We evaluated the efficacy and safety of a Bcl-2 antisense oligonucleotide, G3139, in combination with doxorubicin (A) and docetaxel (T) in patients with locally advanced breast cancer (LABC).

EXPERIMENTAL DESIGN

Following a brief phase I to determine the phase II dose, patients with locally advanced breast cancer received G3139 administered by continuous i.v. infusion for 5 to 7 days with bolus A (50 mg/m2) and T (75 mg/m2) administered on either day 3 or 6 of therapy with G3139. Cycles were repeated every 21 days x 6 in the neoadjuvant setting. Serial plasma samples were obtained for pharmacokinetic analysis. Tissue samples were obtained before and after therapy for pharmacodynamic analysis of Bcl-2 expression.

RESULTS

Thirty patients (median age, 49 years; range, 24-71 years) received 160 cycles. During the phase I portion of the trial, the dose of G3139 was escalated from 3 to 7 mg/kg/d (i.v. for 5 days) in combination with AT. During the phase II portion of the trial, several doses and schedules of G3139 were evaluated. There were no pathologic complete responses. Pharmacodynamic studies showed limited Bcl-2 down-regulation in the primary tumors.

CONCLUSIONS

G3139 in combination with doxorubicin and docetaxel is well tolerated. No pathologic complete response was seen and pharmacodynamic studies showed very little down-regulation of Bcl-2 in primary tumors, perhaps related to issues with insufficient drug delivery to the intact tumor.

MRP- and BCL-2-mediated drug resistance in human SCLC: effects of apoptotic sphingolipids in vitro

Multidrug-resistance-associated protein (MRP) and BCL-2 contribute to drug resistance expressed in SCLC. To establish whether MRP-mediated drug resistance affects sphingolipid (SL)-induced apoptosis in SCLC, we first examined the human SCLC cell line, UMCC-1, and its MRP over-expressing, drug-resistant subline, UMCC-1/VP. Despite significantly decreased sensitivity to doxorubicin (Dox) and to the etoposide, VP-16, the drug-selected line was essentially equally as sensitive to treatment with exogenous ceramide (Cer), sphingosine (Sp) or dimethyl-sphingosine (DMSP) as the parental line. Next, we observed that high BCL-2-expressing human H69 SCLC cells, that were approximately 160-fold more sensitive to Dox than their combined BCL-2 and MRP-over-expressing (H69AR) counterparts, were only approximately 5-fold more resistant to DMSP. Time-lapse fluorescence microscopy of either UMCC cell line treated with DMSP-Coumarin revealed comparable extents and kinetics of SL uptake, further ruling out MRP-mediated effects on drug uptake. DMSP potentiated the cytotoxic activity of VP-16 and Taxol, but not Dox, in drug-resistant UMCC-1/VP cells. However, this sensitization did not appear to involve DMSP-mediated effects on the function of MRP in drug export; nor did DMSP strongly shift the balance of pro-apoptotic Sps and anti-apoptotic Sp-1-Ps in these cells. We conclude that SL-induced apoptosis markedly overcomes or bypasses MRP-mediated drug resistance relevant to SCLC and may suggest a novel therapeutic approach to chemotherapy for these tumors.

Genetic changes in small cell lung carcinoma

Small cell lung carcinoma (SCLC) accounts for approximately 15% of all lung cancer cases. Despite a frequently good response to first-line treatment with chemotherapy and/or radiotherapy, early relapse occurs in the majority of patients and 5-year survival is only about 5%. Therefore, there is a need to develop novel treatments to improve the outcome of patients with SCLC. To fulfil this need, it is critical to gain further understanding on the molecular basis of SCLC and specifically to identify novel therapeutic targets. Clinical trials with molecularly targeted agents have been performed with little success in the past, but recently many promising oncogenic pathways have been discovered and novel targeted therapies are under evaluation. In this review, we summarise the most relevant genetic and signalling pathway alterations reported to date in SCLC and discuss the potential therapeutic implications of such events.

Targeted manipulation of apoptosis in cancer treatment

Apoptosis is a fundamental process in the development and maintenance of multicellular organisms and its regulation is commonly disrupted in human cancers. In vitro and in vivo, effective treatment of cancer with radiotherapy or anticancer drugs (or both) is frequently associated with increased markers of apoptosis. However, clinical resistance to treatment is common in many tumours, particularly with increasing lines of therapy. Diminished ability to undergo apoptosis might cause extensive therapeutic cross-resistance in cancer cells. With increased understanding of the regulatory and effector molecules of apoptosis new drugs have been developed that might manipulate the apoptotic balance in cancer cells in favour of cell death. This Review summarises the rationale for direct manipulation of various elements of apoptosis and describes agents that are currently under investigation in early-phase clinical trials in many different cancer types.

Bcl-2 family members as molecular targets in cancer therapy

Escape from apoptosis is often a hallmark of cancer cells, and is associated to chemotherapy resistance or tumor relapse. Proteins from the Bcl-2 family are the key regulators of the intrinsic pathway of apoptosis, controlling the point-of no-return and setting the threshold to engage the death machinery in response to a chemical damage. Therefore, Bcl-2 proteins have emerged as an attractive target to develop novel anticancer drugs. Current pharmacological approaches are focused on the use of peptides, small inhibitory molecules or antisense oligonucleotides to neutralize antiapoptotic Bcl-2 proteins, lowering the threshold and facilitating apoptosis of cancer cells. We discuss here recent advances in the development of Bcl-2 targeted anticancer therapies.

Therapeutic efficacy of ABT-737, a selective inhibitor of BCL-2, in small cell lung cancer

Bcl-2 is a central regulator of cell survival that is overexpressed in the majority of small cell lung cancers (SCLC) and contributes to both malignant transformation and therapeutic resistance. We compared primary SCLC xenografts prepared from de novo human tumors with standard cell line-based xenografts in the evaluation of a novel and highly potent small molecule inhibitor of Bcl-2, ABT-737. ABT-737 induced dramatic regressions in tumors derived from some SCLC cell lines. In contrast, only one of three primary xenograft SCLC tumors showed significant growth inhibition with ABT-737. Explanations for this apparent dichotomy may include relatively low expression of Bcl-2 in the primary xenografts or inherent differences in the model systems. The addition of etoposide to ABT-737 in the primary xenografts resulted in significant decreases in tumor growth, underscoring the clinical potential of ABT-737 in combination therapy. To identify factors that may contribute to resistance to ABT-737 and related inhibitors, we isolated resistant derivatives of an initially sensitive cell line-based xenograft. Acquired resistance in this model was associated with decreases in the expression of the primary target Bcl-2, of proapoptotic partners of Bcl-2 (Bax and Bim), and of Bcl-2:Bim heterodimers. Expression profiling reveals 85 candidate genes demonstrating consistent changes in gene expression with acquired resistance. Taken together, these data have specific implications for the clinical development of Bcl-2 inhibitors for SCLC and broader implications for the testing of novel anticancer strategies in relevant preclinical models.

Novel systemic therapies for small cell lung cancer

A diagnosis of small cell lung cancer (SCLC) today confers essentially the same terrible prognosis that it did 25 years ago, when common use of cisplatin-based chemotherapy began for this disease. In contrast to past decades of research on many other solid tumors, studies of combination chemotherapy using later generation cytotoxics and targeted kinase inhibitors have not had a significant impact on standard care for SCLC. The past few years have seen suggestions of incrementally improved outcomes using standard cytotoxics, including cisplatin-based combination studies of irinotecan and amrubicin by Japanese research consortia. Confirmatory phase III studies of these agents are ongoing in the United States. Antiangiogenic strategies are also of primary interest and are in late-phase testing. Several novel therapeutics, including high-potency small molecule inhibitors of Bcl-2 and the Hedgehog signaling pathway, and a recently discovered replication-competent picornavirus, have shown remarkable activity against SCLC in preclinical models and are currently in simultaneous phase I clinical development. Novel therapeutic approaches based on advances in understanding of the biology of SCLC have the potential to radically change the outlook for patients with this disease.

Fast, hungry and unstable: finding the Achilles' heel of small-cell lung cancer

Over 95% of patients with small-cell lung cancer (SCLC) die within five years of diagnosis. The standard of care and the dismal prognosis for this disease have not changed significantly over the past 25 years. Some of the characteristics of SCLC that have defined it as a particularly virulent form of cancer -- rapid proliferation, excessive metabolic and angiogenic dependence, apoptotic imbalance and genetic instability -- are now being pursued as tumor-specific targets for intervention both in preclinical and early phase clinical studies. Here, we summarize areas of ongoing anti-cancer drug development, including classes of agents that target essential pathways regulating proliferation, angiogenesis, apoptotic resistance, chromosomal and protein stability, and cell-cell and cell-matrix interaction.