A phase II study of obatoclax mesylate, a Bcl-2 antagonist, plus topotecan in relapsed small cell lung cancer

Emerging advances in defining the molecular and therapeutic landscape of small-cell lung cancer

Small-cell lung cancer (SCLC) has traditionally been considered a recalcitrant cancer with a dismal prognosis, with only modest advances in therapeutic strategies over the past several decades. Comprehensive genomic assessments of SCLC have revealed that most of these tumours harbour deletions of the tumour-suppressor genes TP53 and RB1 but, in contrast to non-small-cell lung cancer, have failed to identify targetable alterations. The expression status of four transcription factors with key roles in SCLC pathogenesis defines distinct molecular subtypes of the disease, potentially enabling specific therapeutic approaches. Overexpression and amplification of MYC paralogues also affect the biology and therapeutic vulnerabilities of SCLC. Several other attractive targets have emerged in the past few years, including inhibitors of DNA-damage-response pathways, epigenetic modifiers, antibody-drug conjugates and chimeric antigen receptor T cells. However, the rapid development of therapeutic resistance and lack of biomarkers for effective selection of patients with SCLC are ongoing challenges. Emerging single-cell RNA sequencing data are providing insights into the plasticity and intratumoural and intertumoural heterogeneity of SCLC that might be associated with therapeutic resistance. In this Review, we provide a comprehensive overview of the latest advances in genomic and transcriptomic characterization of SCLC with a particular focus on opportunities for translation into new therapeutic approaches to improve patient outcomes.

Topotecan in a Real-World Small-Cell Lung Cancer Cohort: Prognostic Biomarkers Improve Selection of Patients for Second-Line Treatment

BACKGROUND

Small-cell lung cancer (SCLC) is a highly aggressive tumor, and overall survival (OS) remains poor despite intensive efforts to develop new treatment strategies. In second line, topotecan is the only approved drug, with a median OS of 5.9 months. However, real-world SCLC patients are often in worse condition and harbor more comorbidities than study populations. Therefore, the real-world performance of topotecan may differ from that seen in studies. Here, we analyzed outcomes of SCLC patients receiving topotecan and identified predictive and prognostic markers.

PATIENTS AND METHODS

We retrospectively analyzed 44 consecutive SCLC patients receiving topotecan between 2015 and 2022. We analyzed baseline characteristics (age, ECOG-PS, topotecan cycles, and dosage) and pre-treatment blood values (LDH, CRP, sodium) as well as prognostic scores (neutrophil/lymphocyte ratio (NLR), thrombocyte/lymphocyte ratio (TLR), Glasgow Prognostic Score, prognostic nutritional score, systemic inflammation index (SII), and the prognostic index) extracted from electronic patients' charts to identify predictive and prognostic markers.

RESULTS

In our cohort, mPFS and mOS were only 1.9 and 5.6 months, respectively. Gender, ECOG-PS, active brain metastases, NLR, GPS, PNI, and SII significantly influenced PFS and OS in univariate analysis. ECOG-PS (p > 0.001), active brain metastases (p = 0.001), and SII (p = 0.008) were significant independent prognostic variables in a multivariate COX regression model. Selecting patients by these three markers achieved an mPFS of 5.7 months and thus increased the mPFS three-fold. Patients not meeting all criteria had an mPFS of 1.8 months (p = 0.006). Patients identified by prognostic markers had an mOS of 9.1 months (p = 0.002).

CONCLUSIONS

The efficacy of topotecan in SCLC real-world patients is poor, indicating that many patients were treated without any benefit. Easy-to-obtain markers can predict response and treatment efficacy and should therefore be validated in larger cohorts to identify patients who are more likely to benefit from topotecan.

Comprehensive review of Bcl-2 family proteins in cancer apoptosis: Therapeutic strategies and promising updates of natural bioactive compounds and small molecules

Cancer has a considerably higher fatality rate than other diseases globally and is one of the most lethal and profoundly disruptive ailments. The increasing incidence of cancer among humans is one of the greatest challenges in the field of healthcare. A significant factor in the initiation and progression of tumorigenesis is the dysregulation of physiological processes governing cell death, which results in the survival of cancerous cells. B-cell lymphoma 2 (Bcl-2) family members play important roles in several cancer-related processes. Drug research and development have identified various promising natural compounds that demonstrate potent anticancer effects by specifically targeting Bcl-2 family proteins and their associated signaling pathways. This comprehensive review highlights the substantial roles of Bcl-2 family proteins in regulating apoptosis, including the intricate signaling pathways governing the activity of these proteins, the impact of reactive oxygen species, and the crucial involvement of proteasome degradation and the stress response. Furthermore, this review discusses advances in the exploration and potential therapeutic applications of natural compounds and small molecules targeting Bcl-2 family proteins and thus provides substantial scientific information and therapeutic strategies for cancer management.

Recent trends and advances in novel formulations as an armament in Bcl-2/Bax targeted breast cancer

Breast cancer (BC) remains a significant health burden worldwide, necessitating the development of innovative therapeutic strategies. The B-cell lymphoma 2 (Bcl-2) family proteins, Bcl-2 and Bax, play a crucial role in regulating apoptosis and thus are promising targets for BC therapy. We focus on the recent advancements in novel formulations that specifically target Bcl-2/Bax pathway to combat BC. It provides an overview on biological functions of Bcl-2/Bax in apoptosis regulation, emphasizing their significance in pathogenesis and progression of the disease while covering the numerous therapeutic approaches aimed at modulating the Bcl-2/Bax pathway, including small-molecule inhibitors, peptides, gene-based therapies and other repurposed drugs harboured onto cutting-edge technologies and nanocarrier systems employed to enhance the targeted delivery of Bcl-2/Bax inhibitors tumor cells. These advanced formulations aim to improve therapeutic efficacy, minimize off-target effects, and overcome drug resistance, offering promising prospects in its treatment. In conclusion, it illuminates the diverse and evolving landscape of novel formulations as an essential armament in targeting these proteins while bridging and unravelling the obscurity of Bcl-2/Bax pathway-targeted drug delivery systems which are presently in their nascent stages of exploration for BC therapy which can benefit researchers, clinicians, and pharmaceutical scientists.

Novel therapeutic strategies for recurrent SCLC

Therapeutic options for patients with relapsed SCLC are limited, and the prognosis in this setting remains poor. While clinical outcomes for frontline treatment have modestly improved with the introduction of immunotherapy, treatment in the second-line setting persists almost unchanged. In this review, current treatment options and recent advances in molecular biology are described. Emerging therapeutic options in this setting and potential strategies to improve clinical outcomes of these patients are also addressed.

Bcl-2 pathway inhibition in solid tumors: a review of clinical trials

Due to their key role in the pathogenesis of cancer through the regulation of apoptosis, the B-cell leukemia/lymphoma-2 (BCL-2) family proteins have been an attractive target for cancer therapy for the past decades. Throughout the years, many Bcl-2 family inhibitors have been developed, with Venetoclax being now successfully used in treating hematological malignancies. Although their effectiveness in the treatment of solid tumors is yet to be established, some preclinical evidence indicates their possible clinical application. This review aims to summarize current data from completed clinical trials that used Bcl-2 protein family inhibitors as monotherapy or in combination with other agents for the treatment of solid malignancies. We managed to include clinical trials of various phases which analyze the pharmacokinetics and pharmacodynamics of the drugs, as well as the effectiveness and adverse effects. Active and recruiting clinical trials are also briefly presented and future prospects and challenges are discussed.

Small-Cell Lung Cancer Long-Term Survivor Patients: How to Find a Needle in a Haystack?

Small-cell lung cancer (SCLC) is an aggressive malignancy characterized by a rapid progression and a high resistance to treatments. Unlike other solid tumors, there has been a scarce improvement in emerging treatments and survival during the last years. A better understanding of SCLC biology has allowed for the establishment of a molecular classification based on four transcription factors, and certain therapeutic vulnerabilities have been proposed. The universal inactivation of TP53 and RB1, along with the absence of mutations in known targetable oncogenes, has hampered the development of targeted therapies. On the other hand, the immunosuppressive microenvironment makes the success of immune checkpoint inhibitors (ICIs), which have achieved a modest improvement in overall survival in patients with extensive disease, difficult. Currently, atezolizumab or durvalumab, in combination with platinum–etoposide chemotherapy, is the standard of care in first-line setting. However, the magnitude of the benefit is scarce and no predictive biomarkers of response have yet been established. In this review, we describe SCLC biology and molecular classification, examine the SCLC tumor microenvironment and the challenges of predictive biomarkers of response to new treatments, and, finally, assess clinical and molecular characteristics of long-term survivor patients in order to identify possible prognostic factors and treatment vulnerabilities.

BH3-mimetics: recent developments in cancer therapy

The hopeful outcomes from 30 years of research in BH3-mimetics have indeed served a number of solid paradigms for targeting intermediates from the apoptosis pathway in a variety of diseased states. Not only have such rational approaches in drug design yielded several key therapeutics, such outputs have also offered insights into the integrated mechanistic aspects of basic and clinical research at the genetics level for the future. In no other area of medical research have the effects of such work been felt, than in cancer research, through targeting the BAX-Bcl-2 protein-protein interactions. With these promising outputs in mind, several mimetics, and their potential therapeutic applications, have also been developed for several other pathological conditions, such as cardiovascular disease and tissue fibrosis, thus highlighting the universal importance of the intrinsic arm of the apoptosis pathway and its input to general tissue homeostasis. Considering such recent developments, and in a field that has generated so much scientific interest, we take stock of how the broadening area of BH3-mimetics has developed and diversified, with a focus on their uses in single and combined cancer treatment regimens and recently explored therapeutic delivery methods that may aid the development of future therapeutics of this nature.

Therapeutic potential of indole alkaloids in respiratory diseases: A comprehensive review

BACKGROUND

Indole alkaloids are very promising for potential therapeutic purposes and appear to be particularly effective against respiratory diseases. Several experimental studies have been performed, both in vivo and in vitro, to evaluate the effectiveness of indole alkaloids for the management of respiratory disorders, including asthma, emphysema, tuberculosis, cancer, and pulmonary fibrosis.

PURPOSE

The fundamental objective of this review was to summarize the in-depth therapeutic potential of indole alkaloids against various respiratory disorders.

STUDY DESIGN

In addition to describing the therapeutic potential, this review also evaluates the toxicity of these alkaloids, which have been utilized for therapeutic benefits but have demonstrated toxic consequences. Some indole alkaloids, including scholaricine, 19-epischolaricine, vallesamine, and picrinine, which are derived from the plant Alstonia scholaris, have shown toxic effects in non-rodent models.

METHODS

This review also discusses clinical studies exploring the therapeutic efficacy of indole alkaloids, which have confirmed the promising benefits observed in vivo and in vitro.

RESULTS

The indole alkaloidal compounds have shown efficacy in subjects with respiratory diseases.

CONCLUSION

The available data established both preclinical and clinical studies confirm the potential of indole alkaloids to treat the respiratory disorders.

Patterns of transcription factor programs and immune pathway activation define four major subtypes of SCLC with distinct therapeutic vulnerabilities

Despite molecular and clinical heterogeneity, small cell lung cancer (SCLC) is treated as a single entity with predictably poor results. Using tumor expression data and non-negative matrix factorization, we identify four SCLC subtypes defined largely by differential expression of transcription factors ASCL1, NEUROD1, and POU2F3 or low expression of all three transcription factor signatures accompanied by an Inflamed gene signature (SCLC-A, N, P, and I, respectively). SCLC-I experiences the greatest benefit from the addition of immunotherapy to chemotherapy, while the other subtypes each have distinct vulnerabilities, including to inhibitors of PARP, Aurora kinases, or BCL-2. Cisplatin treatment of SCLC-A patient-derived xenografts induces intratumoral shifts toward SCLC-I, supporting subtype switching as a mechanism of acquired platinum resistance. We propose that matching baseline tumor subtype to therapy, as well as manipulating subtype switching on therapy, may enhance depth and duration of response for SCLC patients.

Design, Synthesis, Anticancer Activity, and Solid Lipid Nanoparticle Formulation of Indole- and Benzimidazole-Based Compounds as Pro-Apoptotic Agents Targeting Bcl-2 Protein

Cancer is a multifactorial disease necessitating identification of novel targets for its treatment. Inhibition of Bcl-2 for triggered pro-apoptotic signaling is considered a promising strategy for cancer treatment. Within the current work, we aimed to design and synthesize a new series of benzimidazole- and indole-based derivatives as inhibitors of Bcl-2 protein. The market pan-Bcl-2 inhibitor, obatoclax, was the lead framework compound for adopted structural modifications. The obatoclax’s pyrrolylmethine linker was replaced with straight alkylamine or carboxyhydrazine methylene linkers providing the new compounds. This strategy permitted improved structural flexibility of synthesized compounds adopting favored maneuvers for better fitting at the Bcl-2 major hydrophobic pocket. Anti-cancer activity of the synthesized compounds was further investigated through MTT-cytotoxic assay, cell cycle analysis, RT-PCR, ELISA and DNA fragmentation. Cytotoxic results showed compounds 8a, 8b and 8c with promising cytotoxicity against MDA-MB-231/breast cancer cells (IC₅₀ = 12.69 ± 0.84 to 12.83 ± 3.50 µM), while 8a and 8c depicted noticeable activities against A549/lung adenocarcinoma cells (IC₅₀ = 23.05 ± 1.45 and 11.63 ± 2.57 µM, respectively). The signaling Bcl-2 inhibition pathway was confirmed by molecular docking where significant docking energies and interactions with key Bcl-2 pocket residues were depicted. Moreover, the top active compound, 8b, showed significant upregulated expression levels of pro-apoptotic/anti-apoptotic of genes; Bax, Bcl-2, caspase-3, -8, and -9 through RT-PCR assay. Improving the compound’s pharmaceutical profile was undertaken by introducing 8b within drug-solid/lipid nanoparticle formulation prepared by hot melting homogenization technique and evaluated for encapsulation efficiency, particle size, and zeta potential. Significant improvement was seen at the compound’s cytotoxic activity. In conclusion, 8b is introduced as a promising anti-cancer lead candidate that worth future fine-tuned lead optimization and development studies while exploring its potentiality through in-vivo preclinical investigation.

Mcl-1 as a "barrier" in cancer treatment: Can we target it now?

During the last two decades, the study of Mcl-1, an anti-apoptotic member of the Bcl-2 family, attracted researchers due to its important role in cancer cell survival and tumor development. The significance of Mcl-1 protein in resistance to chemotherapeutics makes it an attractive target in cancer therapy. Here, we discuss the diverse possibilities for indirect Mcl-1 inhibition through its downregulation, for example, via targeting for proteasomal degradation or blockage of translation and transcription. We also provide an overview of the direct blocking of protein-protein interactions with pro-apoptotic Bcl-2 family proteins, including examples of the most promising regulators of Mcl-1 and selective BH3-mimetics, which at present are under clinical evaluation. Moreover, several approaches for the co-targeting of Mcl-1 and other proteins (e.g., CDKs) are also presented. In addition, we highlight the broad spectrum of problems that accompanied the discovery and development of effective Mcl-1 inhibitors.

A novel Bcl-2 inhibitor, BM-1197, induces apoptosis in malignant lymphoma cells through the endogenous apoptotic pathway

Background

Bcl-2 family members play an important role in the development of malignant lymphoma and can induce drug resistance in anticancer treatment. The development of small molecules targeting Bcl-2 family proteins may be a new strategy for the treatment of malignant lymphoma. In this study, we investigate the antitumor effect and cellular mechanism of a novel Bcl-2/Bcl-xL dual inhibitor, BM-1197, in DCBCL and Burkitt lymphoma cells.

Methods

The CCK-8 assay was used to detect cell viability. Apoptosis was determined by Hoechst 33258 staining and flow cytometry. The activity of caspase-3/caspase-9 was determined using a caspase-3/caspase-9 activity kit. Western blotting analysis was performed to evaluate the changes in protein expression. Functional analysis was performed via immunoprecipitation and siRNA interference. Human malignant lymphoma xenograft models in nude mice were established for in vivo efficacy detection.

Results

We find that BM-1197 exerts potent growth-inhibitory activity against lymphoma cells that harbor high expression of Bcl-2 and Bcl-xL in vitro and has a synergistic effect with chemotherapeutic drugs. Mechanistically, we see that the intrinsic apoptosis pathway is activated upon BM-1197 treatment. BM-1197 affects the protein interactions of Bak/Bcl-xl, Bim/Bcl-2, Bim/Bcl-xl, and PUMA/Bcl-2 and induces conformational changes in the Bax protein, which result in the activation of Bax and release of cytochrome c, activate caspase − 9, − 3, and − 7 and finally induce cell apoptosis. Furthermore, our data demonstrate that BM-1197 exhibits strong anti-tumor effects against established human malignant lymphoma xenograft models.

Conclusions

Our study demonstrated BM-1197 exerts potent antitumor effects both in vitro and in vivo and provides promising preclinical data for the further development of BM-1197 in malignant lymphoma.

Understanding Apoptosis and Apoptotic Pathways Targeted Cancer Therapeutics

Various physiological processes involve appropriate tissue developmental process and homeostasis - the pathogenesis of several diseases connected with deregulatory apoptosis process. Apoptosis plays a crucial role in maintaining a balance between cell death and division, evasion of apoptosis results in the uncontrolled multiplication of cells leading to different diseases such as cancer. Currently, the development of apoptosis targeting anticancer drugs has gained much interest since cell death induced by apoptosis causes minimal inflammation. The understanding of complexities of apoptosis mechanism and how apoptosis is evolved by tumor cells to oppose cell death has focused research into the new strategies designed to induce apoptosis in cancer cells. This review focused on the underlying mechanism of apoptosis and the dysregulation of apoptosis modulators involved in the extrinsic and intrinsic apoptotic pathway, which include death receptors (DRs) proteins, cellular FLICE inhibitory proteins (c-FLIP), anti-apoptotic Bcl-2 proteins, inhibitors of apoptosis proteins (IAPs), tumor suppressor (p53) in cancer cells along with various current clinical approaches aimed to selectively induce apoptosis in cancer cells.

Stapled Peptides Inhibitors: A New Window for Target Drug Discovery

Protein-protein interaction (PPI) is a hot topic in clinical research as protein networking has a major impact in human disease. Such PPIs are potential drugs targets, leading to the need to inhibit/block specific PPIs. While small molecule inhibitors have had some success and reached clinical trials, they have generally failed to address the flat and large nature of PPI surfaces. As a result, larger biologics were developed for PPI surfaces and they have successfully targeted PPIs located outside the cell. However, biologics have low bioavailability and cannot reach intracellular targets. A novel class -hydrocarbon-stapled α-helical peptides that are synthetic mini-proteins locked into their bioactive structure through site-specific introduction of a chemical linker- has shown promise. Stapled peptides show an ability to inhibit intracellular PPIs that previously have been intractable with traditional small molecule or biologics, suggesting that they offer a novel therapeutic modality. In this review, we highlight what stapling adds to natural-mimicking peptides, describe the revolution of synthetic chemistry techniques and how current drug discovery approaches have been adapted to stabilize active peptide conformations, including ring-closing metathesis (RCM), lactamisation, cycloadditions and reversible reactions. We provide an overview on the available stapled peptide high-resolution structures in the protein data bank, with four selected structures discussed in details due to remarkable interactions of their staple with the target surface. We believe that stapled peptides are promising drug candidates and open the doors for peptide therapeutics to reach currently "undruggable" space.

Plumbagin induces autophagy and apoptosis of SMMC-7721 cells in vitro and in vivo

Plumbagin (PL), an active naphthoquinone compound, has been demonstrated to be a potential anticancer agent. However, the underlying anticancer mechanism is not fully understood. In this study, the human hepatocellular carcinoma (HCC) SMMC-7721 cell line was studied in an in vitro model. The cell proliferation was inhibited by PL in a dose- and time-dependent manner. Electron microscopy, acridine orange staining, and immunofluorescence were used to evaluate autophagosome formation and LC3 protein expression in PL-treated SMMC-7721 cells. Real-time polymerase chain reaction and Western blot showed that PL treatment suppressed the expression of apoptosis and autophagy factors (LC3, Beclin1, Atg7, and Atg5), which are associated with tumor apoptosis and autophagy in SMMC-7721 cells. In the study of in vitro tumor nude mouse models, PL can inhibit tumor growth. Cell apoptosis and autophagy of the transplanted tumors were evaluated by hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining, and Western blot. In addition, in the in vivo studies of HCC cells, we found that pretreatment with the autophagy inhibitor 3-methyladenine blocked the formation of apoptosis induced by PL. In contrast, administration of the apoptosis inhibitor Z-VAD did not affect PL-induced autophagy. Taken together, our findings strongly suggest that PL is a promising drug with significant antitumor activity in HCC.

Cross Talk Between Cellular Redox State and the Antiapoptotic Protein Bcl-2

SIGNIFICANCE

B cell lymphoma-2 (Bcl-2) was discovered over three decades ago and is the prototype antiapoptotic member of the Bcl-2 family that comprises proteins with contrasting effects on cell fate. First identified as a consequence of chromosomal translocation (t 14:18) in human lymphoma, subsequent studies have revealed mutations and/or gene copy number alterations as well as post-translational modifications of Bcl-2 in a variety of human cancers. The canonical function of Bcl-2 is linked to its ability to inhibit mitochondrial membrane permeabilization, thereby regulating apoptosome assembly and activation by blocking the cytosolic translocation of death amplification factors. Of note, the identification of specific domains within the Bcl-2 family of proteins (Bcl-2 homology domains; BH domains) has not only provided a mechanistic insight into the various interactions between the member proteins but has also been the impetus behind the design and development of small molecule inhibitors and BH3 mimetics for clinical use. Recent Advances: Aside from its role in maintaining mitochondrial integrity, recent evidence provides testimony to a novel facet in the biology of Bcl-2 that involves an intricate cross talk with cellular redox state. Bcl-2 overexpression modulates mitochondrial redox metabolism to create a "pro-oxidant" milieu, conducive for cell survival. However, under states of oxidative stress, overexpression of Bcl-2 functions as a redox sink to prevent excessive buildup of reactive oxygen species, thereby inhibiting execution signals. Emerging evidence indicates various redox-dependent transcriptional changes and post-translational modifications with different functional outcomes.

CRITICAL ISSUES

Understanding the complex interplay between Bcl-2 and the cellular redox milieu from the standpoint of cell fate signaling remains vital for a better understanding of pathological states associated with altered redox metabolism and/or aberrant Bcl-2 expression.

FUTURE DIRECTIONS

Based on its canonical functions, Bcl-2 has emerged as a potential druggable target. Small molecule inhibitors of Bcl-2 and/or other family members with similar function, as well as BH3 mimetics, are showing promise in the clinic. The emerging evidence for the noncanonical activity linked to cellular redox metabolism provides a novel avenue for the design and development of diagnostic and therapeutic strategies against cancers refractory to conventional chemotherapy by the overexpression of this prosurvival protein.

Ionophores: Potential Use as Anticancer Drugs and Chemosensitizers

Ion homeostasis is extremely important for the survival of both normal as well as neoplastic cells. The altered ion homeostasis found in cancer cells prompted the investigation of several ionophores as potential anticancer agents. Few ionophores, such as Salinomycin, Nigericin and Obatoclax, have demonstrated potent anticancer activities against cancer stem-like cells that are considered highly resistant to chemotherapy and responsible for tumor relapse. The preclinical success of these compounds in in vitro and in vivo models have not been translated into clinical trials. At present, phase I/II clinical trials demonstrated limited benefit of Obatoclax alone or in combination with other anticancer drugs. However, future development in targeted drug delivery may be useful to improve the efficacy of these compounds. Alternatively, these compounds may be used as leading molecules for the development of less toxic derivatives.

Decoding the antineoplastic efficacy of Aplysin targeting Bcl-2: A de novo perspective

The B-cell lymphoma-2 (Bcl-2) family proteins have been attributed to be the key regulators in programmed cell death and apoptosis with a prominent role in human cancer. Understanding the fundamental principles of cell survival and death have been the main cornerstone in cancer drug discovery for identification of novel anticancer agents. In this context the Bcl-2 family of anti-and pro-apoptotic proteins provide an excellent opportunity for development of anticancer agents, as blocking the Bcl-2 or Bcl-XL functionally promotes apoptosis in tumor cells and also sensitize them to chemo- and radiotherapies. The present study reports the identification of novel Aplysin analogs as BCL-2 inhibitors from a sequential virtual screening approach using drug-like, ADMET, docking, pharmacophore filters and molecular dynamics simulation. We identified promising Aplysin analogs that have a potential to be Bcl-2 inhibitors just like the standard drug Obatoclax. One of the compound analog 11 was identified to be a promising inhibitor of Bcl-2 in the docking, pharmacophore and simulation based models.The molecular modeling information provided here can be vital in designing of the novel Bcl-2 inhibitors.

Bcl-2 expression in circulating tumor cells (CTCs) of patients with small cell lung cancer (SCLC) receiving front-line treatment

INTRODUCTION

To investigate the presence of Bcl-2⁺CTCs in chemotherapy-naïve SCLC patients and their clinical relevance during front-line treatment.

METHODS

Peripheral blood was obtained from 66 consecutive-patients before chemotherapy administration, after one-cycle and at relapse. CTCs were detected by CellSearch and immunofluorescence using anti-Bcl-2, anti-M30, anti-cytokeratins(CK), anti-CD45 and anti-vimentin(Vim) antibodies.

RESULTS

Before treatment, CTCs were detected in 62.1% and 72.7% of patients using the CellSearch and immunofluorescence (Bcl-2⁺/CD45^-), respectively. One-treatment cycle significantly decreased both CTCs' detection rate(p < 0.001) and their absolute number (p < 0.001). On relapse, both the number of positive-patients and the absolute number of CTC subpopulations were significantly increased, compared to post-1st cycle (CellSearch: p = 0.002 and immunofluorescence: p < 0.001). Immunofluorescence revealed an important CTC heterogeneity (Bcl2⁺/Vim⁺, Bcl2⁺/Vim^-, Bcl2⁺/CK⁺, Bcl2⁺/CK^- and Bcl2⁺/M30^- CTCs). Moreover, 50.0% of patients without detectable CTCs by CellSearch had detectable Bcl-2⁺/CD45^- cells. Multivariate analysis revealed a significant association between Bcl-2⁺/CD45^-cells at baseline and PFS (HR = 4.5;p = 0.005) and OS (HR: 4.3; p = 0.001). Bcl-2⁺/CD45^-cells after one-treatment cycle were significantly associated with shorter OS (HR: 13.9; p = 0.007).

CONCLUSIONS

These results demonstrate an important phenotypic CTCs heterogeneity based on the co-expression of Bcl-2, CK, Vim and M30 in SCLC patients. The changes of Bcl-2⁺/CD45^- CTCs during treatment seem to be a dynamic biomarker associated with treatment efficacy and patients' clinical outcome.

Advanced small cell lung cancer (SCLC): new challenges and new expectations

Small cell lung cancer (SCLC) remains one of the most lethal malignancies and a major health riddle. The therapeutic options are limited. The combination of etoposide or irinotecan with platinum chemotherapy is the standard of care at any stage. The last decade systemic efforts have been done to reveal specific therapeutic targets for small cell lung carcinomas. In this review, we focus on the new therapeutic strategies of SCLC, including immune-related treatment that may change the prognosis of the disease. The main genetic mutations observed in SCLC are TP53 and RB1 mutations; however, it is well known that these molecules are not yet targetable. In recent years, research has revealed other frequent genetic alterations and activated signaling pathways that might be an effective treatment target. Loss of PTEN, activating PI3K mutations, inhibition of NOTCH pathway and aurora kinase activation are among them. Moreover, FDGFR1 amplification, activation of the Hedgehog pathway and repair-protein PARP1 seem to participate in SCLC tumorigenesis. These new findings have identified some interesting targets. Moreover, immunotherapy tries to find its place in the treatment of SCLC. Immune checkpoint inhibitors are under investigation in phase I to III clinical trials. We hope that in next years the treatment of SCLC patients will be improved with the administration of targeting therapy and the introduction of immunotherapy.

Transcriptomic-metabolomic reprogramming in EGFR-mutant NSCLC early adaptive drug escape linking TGFβ2-bioenergetics-mitochondrial priming

The impact of EGFR-mutant NSCLC precision therapy is limited by acquired resistance despite initial excellent response. Classic studies of EGFR-mutant clinical resistance to precision therapy were based on tumor rebiopsies late during clinical tumor progression on therapy. Here, we characterized a novel non-mutational early adaptive drug-escape in EGFR-mutant lung tumor cells only days after therapy initiation, that is MET-independent. The drug-escape cell states were analyzed by integrated transcriptomic and metabolomics profiling uncovering a central role for autocrine TGFβ2 in mediating cellular plasticity through profound cellular adaptive Omics reprogramming, with common mechanistic link to prosurvival mitochondrial priming. Cells undergoing early adaptive drug escape are in proliferative-metabolic quiescent, with enhanced EMT-ness and stem cell signaling, exhibiting global bioenergetics suppression including reverse Warburg, and are susceptible to glutamine deprivation and TGFβ2 inhibition. Our study further supports a preemptive therapeutic targeting of bioenergetics and mitochondrial priming to impact early drug-escape emergence using EGFR precision inhibitor combined with broad BH3-mimetic to interrupt BCL-2/BCL-xL together, but not BCL-2 alone.

Why do BCL-2 inhibitors work and where should we use them in the clinic?

Intrinsic apoptosis is controlled by the BCL-2 family of proteins but the complexity of intra-family interactions makes it challenging to predict cell fate via standard molecular biology techniques. We discuss BCL-2 family regulation and how to determine cells’ readiness for apoptosis and anti-apoptotic dependence. Cancer cells often adopt anti-apoptotic defense mechanisms in response to oncogenic stress or anti-cancer therapy. However, by determining their anti-apoptotic addiction, we can use novel BH3 mimetics to overwhelm this apoptotic blockade. We outline the development and uses of these unique anti-apoptotic inhibitors and how to possibly combine them with other anti-cancer agents using dynamic BH3 profiling (DBP) to improve personalized cancer treatment.

Implications of Bcl-2 and its interplay with other molecules and signaling pathways in prostate cancer progression

INTRODUCTION

Among several genetic alterations involved in the progression of prostate cancer, B cell lymphoma gene number 2 (BCL-2) is an important target molecule in the progression of androgen-independent prostate cancer (AIPC) after androgen ablation or castration. Nevertheless, the molecular mechanism of BCL-2 in prostate cancer progression remains elusive and controversial. In the current review, we discuss the critical role of BCL-2 in the carcinogenesis of prostate cancer with experimental evidences on the BCL-2 molecular networks in AIPC and androgen-dependent prostate cancer (ADPC) and subsequently suggest perspective research targeting BCL-2. Areas covered: This review focused on the molecular implications of BCL-2 in association with other molecules and signaling pathways involved in the progression and carcinogenesis of prostate cancer. Expert opinion: BCL-2 plays a pivotal role in the progression of AIPC than in ADPC since androgen represses BCL-2. BCL-2 acts as a pro-survival molecule in association with androgen-related signaling in the progression of ADPC, while BCL-2 upregulation, PTEN loss, PI3K/AKT phosphorylation and receptor tyrosine kinase (RTK) activation are primarily involved in AIPC. To identify more effective prostate cancer therapy, further mechanistic studies are required with BCL-2 inhibitors in AIPC and ADPC, considering a multi-target therapy against BCL-2 and its related signaling.

Small molecule inhibitor TW-37 is tolerable and synergistic with chemotherapy in nasopharyngeal carcinoma

Chemotherapy is a crucial adjuvant therapy of advanced nasopharyngeal carcinoma (NPC). However, enhancing sensitivity and tolerance of chemotherapeutics in NPC treatment have been challenging. Both Bcl-2 and Mcl-1, 2 pro-survival proteins of Bcl-2 family, play essential roles on the chemotherapy tolerance of numerous cancers. In the present study, we explored the influences of TW-37, a small molecule inhibitor of Bcl-2 and Mcl-1, on the efficiency of chemotherapy for NPC. Oncomine cancer database shows that NPC tissues have higher expression of Bcl-2 and Mcl-1 than those of normal nasopharyngeal epithelial (NPE) tissues. And our results reveal that chemotherapeutics, Cisplatin (CDDP) and 5-Fluoracil (5-FU), result in the greater decrease of protein level of Bcl-2 and Mcl-1 in NPC cells than those in NPE cells. TW-37 does not have significant impact on the chemotherapeutics-treated NPE cell viability at a dosage that efficiently reduces chemotherapeutics-treated NPC cell viability. Moreover, impacts of TW-37 on the cell viability of chemotherapeutics-treated NPC cells are dependent on the expression of Bcl-2 and Mcl-1 in NPC cells. Further explorations suggest that TW-37 prominently promotes apoptosis in NPC cells under chemotherapeutics treatments but not in NPE cells. Meanwhile, TW-37 also remarkably reduces colony formation ability of chemotherapeutics-treated NPC cells. Importantly, in vivo models, TW-37 observably increases chemosensitivity of NPC tumors but has not markedly influence on the normal tissues in mice. In conclusion, our results point to TW-37 as a promising ancillary drug for the chemotherapy of NPC.

BCL-2: Long and winding path from discovery to therapeutic target

In 1988, the BCL-2 protein was found to promote cancer by limiting cell death rather than enhancing proliferation. This discovery set the wheels in motion for an almost 30 year journey involving many international research teams that has recently culminated in the approval for a drug, ABT-199/venetoclax/Venclexta that targets this protein in the treatment of cancer. This review will describe the long and winding path from the discovery of this protein and understanding the fundamental process of apoptosis that BCL-2 and its numerous homologues control, through to its exploitation as a drug target that is set to have significant benefit for cancer patients.

How to unleash mitochondrial apoptotic blockades to kill cancers?

Apoptosis, especially the intrinsic mitochondrial cell death pathway, is regulated by the BCL-2 family of proteins. Defects in apoptotic machinery are one of the main mechanisms that cells employ to evade cell death and become cancerous. Targeting the apoptotic defects, either by direct inhibition of BCL-2 family proteins or through modulation of regulatory pathways, can restore cell sensitivity to cell death. This review will focus on the aspects of BCL-2 family proteins, their interactions with kinase pathways, and how novel targeted agents can help overcome the apoptotic blockades. Furthermore, functional assays, such as BH3 profiling, may help in predicting responses to chemotherapies and aid in the selection of combination therapies by determining the mitochondrial threshold for initiating cell death.

Combined inhibition of Bcl-2/Bcl-xL and Usp9X/Bag3 overcomes apoptotic resistance in glioblastoma in vitro and in vivo

Despite great efforts taken to advance therapeutic measures for patients with glioblastoma, the clinical prognosis remains grim. The antiapoptotic Bcl-2 family protein Mcl-1 is overexpressed in glioblastoma and represents an important resistance factor to the BH-3 mimetic ABT263.

In this study, we show that combined treatment with ABT263 and GX15-070 overcomes apoptotic resistance in established glioblastoma cell lines, glioma stem-like cells and primary cultures. Moreover, this treatment regimen also proves to be advantageous in vivo. On the molecular level, GX15-070 enhanced apoptosis by posttranslational down-regulation of the deubiquitinase, Usp9X, and the chaperone Bag3, leading to a sustained depletion of Mcl-1 protein levels. Moreover, knock-down of Usp9X or Bag3 depleted endogenous Mcl-1 protein levels and in turn enhanced apoptosis induced through Bcl-2/Bcl-xL inhibition.

In conclusion, combined treatment with ABT263 and GX15-070 results in a significantly enhanced anti-cancer activity in vitro as well as in vivo in the setting of glioblastoma. Both drugs, ABT263 and GX15-070 have been evaluated in clinical studies which facilitates the translational aspect of taking this combinatorial approach to the clinical setting. Furthermore we present a novel mechanism by which GX15-070 counteracts Mcl-1 expression which may lay a foundation for a novel target in cancer therapy.

Targeted drugs in small-cell lung cancer

In contrast to non-small-cell lung cancer (NSCLC), few advances have been made in systemic treatment of small-cell lung cancer (SCLC) in recent years. Most patients are diagnosed with extensive stage disease and are commonly treated with platinum-based chemotherapy which, although attaining high initial objective responses, has a limited impact on survival. Due to the dismal prognosis of SCLC, novel and more effective treatment strategies are urgently needed. A deeper characterization of the genomic landscape of SCLC has led to the development of rational and promising targeted agents. However, despite a large number of clinical trials, results have been disappointing and there are still no approved targeted drugs for SCLC. Recent comprehensive genomic studies suggest SCLC is a heterogeneous disease, characterized by genomic alterations targeting a broad variety of genes, including those involved in transcription regulation and chromatin modification which seem to be a hallmark of this specific lung cancer subtype. Current research efforts are focusing on further understanding of the cellular and molecular abnormalities underlying SCLC development, progression and resistance to chemotherapy. Unraveling the genomic complexity of SCLC could be the key to optimize existing treatments, including chemotherapy and radiotherapy, and for identifying those patients most likely to benefit from selected targeted therapeutic approaches.

Small cell lung cancer: will recent progress lead to improved outcomes?

Small cell lung cancer (SCLC) is an aggressive neuroendocrine malignancy with a unique natural history characterized by a short doubling time, high growth fraction, and early development of widespread metastases. Although a chemotherapy- and radiation-sensitive disease, SCLC typically recurs rapidly after primary treatment, with only 6% of patients surviving 5 years from diagnosis. This disease has been notable for the absence of major improvements in its treatment: Nearly four decades after the introduction of a platinum-etoposide doublet, therapeutic options have remained virtually unchanged, with correspondingly little improvement in survival rates. Here, we summarize specific barriers and challenges inherent to SCLC research and care that have limited progress in novel therapeutic development to date. We discuss recent progress in basic and translational research, especially in the development of mouse models, which will provide insights into the patterns of metastasis and resistance in SCLC. Opportunities in clinical research aimed at exploiting SCLC biology are reviewed, with an emphasis on ongoing trials. SCLC has been described as a recalcitrant cancer, for which there is an urgent need for accelerated progress. The NCI convened a panel of laboratory and clinical investigators interested in SCLC with a goal of defining consensus recommendations to accelerate progress in the treatment of SCLC, which we summarize here.

Potential of apoptotic pathway-targeted cancer therapeutic research: Where do we stand?

Underneath the intricacy of every cancer lies mysterious events that impel the tumour cell and its posterity into abnormal growth and tissue invasion. Oncogenic mutations disturb the regulatory circuits responsible for the governance of versatile cellular functions, permitting tumour cells to endure deregulated proliferation, resist to proapoptotic insults, invade and erode normal tissues and above all escape apoptosis. This disruption of apoptosis has been highly implicated in various malignancies and has been exploited as an anticancer strategy. Owing to the fact that apoptosis causes minimal inflammation and damage to the tissue, apoptotic cell death-based therapy has been the centre of attraction for the development of anticancer drugs. Increased understanding of the molecular pathways underlying apoptosis has enabled scientists to establish unique approaches targeting apoptosis pathways in cancer therapeutics. In this review, we reconnoitre the two major pathways (intrinsic and extrinsic) targeted cancer therapeutics, steering toward chief modulators of these pathways, such as B-cell lymphoma 2 protein family members (pro- and antiapoptotic), inhibitor of apoptosis proteins, and the foremost thespian of extrinsic pathway regulator, tumour necrosis factor-related apoptosis-inducing agent. Together, we also will have a look from clinical perspective to address the agents (drugs) and therapeutic strategies adopted to target these specific proteins/pathways that have entered clinical trials.

Personalized Therapy of Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an aggressive, poorly differentiated neuroendocrine carcinoma with distinct clinical, pathological and molecular characteristics. Despite robust responses to initial chemotherapy and radiation, the prognosis of patients with SCLC remains poor with an overall 5-year survival rate of less than 10 %. Despite the fact that numerous molecularly targeted approaches have thus far failed to demonstrate clinical utility in SCLC, further advances will rely on better definition of the biological pathways that drive survival, proliferation and metastasis. Recent next-generation, molecular profiling studies have identified many new therapeutic targets in SCLC, as well as extreme genomic instability which explains the high degree of resistance. A wide variety of anti-angiogenic agents, growth factor inhibitors, pro-apoptotic agents, and epigenetic modulators have been evaluated in SCLC and many studies of these strategies are on-going. Perhaps the most promising approaches involve agents targeting cancer stem cell pathways and immunomodulatory drugs that interfere with the PD1 and CTLA-4 pathways. SCLC offers many barriers to the development of successful therapy, including limited tumor samples, inadequate preclinical models, high mutational burden, and aggressive tumor growth which impairs functional status and hampers enrollment on clinical trials.

Obatoclax induces G1/G0-phase arrest via p38/p21(waf1/Cip1) signaling pathway in human esophageal cancer cells

Pan-Bcl-2 family inhibitor obatoclax has been demonstrated to be effective against various cancers, of which the mechanism of action is not fully understood. In this study, we demonstrate that obatoclax suppressed esophageal cancer cell viability with concomitant G1/G0-phase cell cycle arrest. At the tested concentrations (1/2 IC50 and IC50), obatoclax neither induced PARP cleavage nor increased the Annexin V-positive population, suggesting G1/G0-phase arrest rather than apoptosis accounts for most of the reduction of cell viability produced by obatoclax. Double knockdown of Bak and Bax by small interference RNA failed to block obatoclax-induced G1/G0-phase arrest, implying its role in cell cycle progression is Bak/Bax-independent. The cell cycle arresting effect of obatoclax was associated with up-regulation of p21(waf1/Cip1). Knockdown of p21(waf1/Cip1) significantly attenuated obatoclax-induced G1/G0-phase arrest. Although obatoclax stimulated phosphorylation of Erk, p38, and JNK, pharmacological inhibition of p38 but not Erk or JNK blocked obatoclax-induced G1/G0-phase arrest. Moreover, knockdown of p38 abolished the cell cycle arresting effect of obatoclax. In consistent with this finding, inhibition of p38 blocked obatoclax-induced p21(waf1/Cip1) expression while inhibition of Erk or JNK failed to exert similar effect. To conclude, these findings suggest that obatoclax induced cell cycle arrest via p38/p21(waf1/Cip1) signaling pathway. This study may shed a new light on the anti-cancer activity of obatoclax in relation to cell cycle arrest.

Attacking cancer's Achilles heel: antagonism of anti-apoptotic BCL-2 family members

Malignant cells routinely violate cellular checkpoints that should initiate cell death in normal cells by triggering pro-apoptotic members of the BCL-2 family of proteins. To escape such death inducing signals, cancer cells often select for upregulation of anti-apoptotic BCL-2 family members including BCL-2, BCL-XL , BFL-1, BCL-W and MCL-1. These family members prevent death by sequestering pro-apoptotic molecules. To counter this resistance mechanism, small molecule inhibitors of anti-apoptotic BCL-2 family members have been under development. These molecules have shown promise in pre-clinical and clinical testing to overcome apoptotic resistance, prompting cancer cells to undergo apoptosis. Alternatively, other strategies have taken advantage of the normal regulatory machinery controlling anti-apoptotic molecules and have used inhibitors of signaling pathways to down-modulate the expression of anti-apoptotic molecules, thus tilting the balance in cancer cells to cell death. This review explores recent developments and strategies aimed at antagonizing anti-apoptotic BCL-2 family member action to promote the induction of cell death in cancer therapy.

Why anti-Bcl-2 clinical trials fail: a solution

The alteration in expression of B cell lymphoma-2 (Bcl-2) family of protein members in cancer is involved mainly in the regulation of apoptosis. Bcl-2 family proteins are currently used as major targets in the development of methods to improve treatment outcomes for cancer patients that underwent clinical trials. Although many agents have been developed for targeting Bcl-2 in the past decade, some previous attempts to target Bcl-2 have not resulted in beneficial clinical outcome for reasons unknown. Here, we propose that this was due in part for not considering the cellular level of a different antiapoptotic protein, i.e., galectin-3 (Gal-3). Gal-3 is a member of the β-galactoside binding protein family and a multifunctional oncogenic protein which regulates cell growth, cell adhesion, cell proliferation, angiogenesis, and apoptosis. Gal-3 is the sole protein that contains the NWGR anti-death motif of the Bcl-2 family and inhibits cell apoptosis induced by chemotherapeutic agents through phosphorylation, translocation and regulation of survival signaling pathways. It is now established that Gal-3 is a candidate target protein to suppress antiapoptotic activity and anticancer drug resistance. In this review, we describe the role and relevance of Gal-3 and Bcl-2 protein family in the regulation of apoptosis and propose a novel combination therapy modality. Combination therapy that targets Gal-3 could be essential for improvement of the efficacy of Bcl-2 targeting therapy in cancers and should be studied in future clinical trials. Otherwise, not considering Gal-3 cellular level could lead to trial failure.

Bcl-2 family of proteins as drug targets for cancer chemotherapy: the long way of BH3 mimetics from bench to bedside

Bcl-2 proteins are key determinants in the life-death balance. In recent years, proteins in this family have been identified as drug targets in the design of new anti-tumor therapies. Advances in the knowledge of the mechanism of action of anti-apoptotic and pro-apoptotic members of the Bcl-2 family have enabled the development of the so-called 'BH3 mimetics'. These compounds act by inhibiting anti-apoptotic proteins of the family, imitating the function of the BH3-only subset of pro-apoptotic members. Combinations of BH3-mimetics with anti-tumor drugs are being evaluated in both preclinical models and clinical trials. Recent advances in these approaches will be reviewed.

The BCL2 Family: Key Mediators of the Apoptotic Response to Targeted Anticancer Therapeutics

The ability of cancer cells to suppress apoptosis is critical for carcinogenesis. The BCL2 family proteins comprise the sentinel network that regulates the mitochondrial or intrinsic apoptotic response. Recent advances in our understanding of apoptotic signaling pathways have enabled methods to identify cancers that are "primed" to undergo apoptosis, and have revealed potential biomarkers that may predict which cancers will undergo apoptosis in response to specific therapies. Complementary efforts have focused on developing novel drugs that directly target antiapoptotic BCL2 family proteins. In this review, we summarize the current knowledge of the role of BCL2 family members in cancer development and response to therapy, focusing on targeted therapeutics, recent progress in the development of apoptotic biomarkers, and therapeutic strategies designed to overcome deficiencies in apoptosis.

SIGNIFICANCE

Apoptosis, long known to be important for response to conventional cytotoxic chemotherapy, has more recently been shown to be essential for the efficacy of targeted therapies. Approaches that increase the likelihood of a cancer to undergo apoptosis following therapy may help improve targeted treatment strategies. Cancer Discov; 5(5); 475-87. ©2015 AACR.

Targeted therapies for small cell lung cancer: Where do we stand?

Small cell lung cancer (SCLC) accounts for 15% of lung cancer cases and is associated with a dismal prognosis. Standard therapeutic regimens have been improved over the past decades, but without a major impact on patient survival. The development of targeted therapies based on a better understanding of the molecular basis of the disease is urgently needed. At the genetic level, SCLC appears very heterogenous, although somatic mutations targeting classical oncogenes and tumor suppressors have been reported. SCLC also possesses somatic mutations in many other cancer genes, including transcription factors, enzymes involved in chromatin modification, receptor tyrosine kinases and their downstream signaling components. Several avenues have been explored to develop targeted therapies for SCLC. So far, however, there has been limited success with these targeted approaches in clinical trials. Further progress in the optimization of targeted therapies for SCLC will require the development of more personalized approaches for the patients.

Assessment of ABT-263 activity across a cancer cell line collection leads to a potent combination therapy for small-cell lung cancer

BH3 mimetics such as ABT-263 induce apoptosis in a subset of cancer models. However, these drugs have shown limited clinical efficacy as single agents in small-cell lung cancer (SCLC) and other solid tumor malignancies, and rational combination strategies remain underexplored. To develop a novel therapeutic approach, we examined the efficacy of ABT-263 across >500 cancer cell lines, including 311 for which we had matched expression data for select genes. We found that high expression of the proapoptotic gene Bcl2-interacting mediator of cell death (BIM) predicts sensitivity to ABT-263. In particular, SCLC cell lines possessed greater BIM transcript levels than most other solid tumors and are among the most sensitive to ABT-263. However, a subset of relatively resistant SCLC cell lines has concomitant high expression of the antiapoptotic myeloid cell leukemia 1 (MCL-1). Whereas ABT-263 released BIM from complexes with BCL-2 and BCL-XL, high expression of MCL-1 sequestered BIM released from BCL-2 and BCL-XL, thereby abrogating apoptosis. We found that SCLCs were sensitized to ABT-263 via TORC1/2 inhibition, which led to reduced MCL-1 protein levels, thereby facilitating BIM-mediated apoptosis. AZD8055 and ABT-263 together induced marked apoptosis in vitro, as well as tumor regressions in multiple SCLC xenograft models. In a Tp53; Rb1 deletion genetically engineered mouse model of SCLC, the combination of ABT-263 and AZD8055 significantly repressed tumor growth and induced tumor regressions compared with either drug alone. Furthermore, in a SCLC patient-derived xenograft model that was resistant to ABT-263 alone, the addition of AZD8055 induced potent tumor regression. Therefore, addition of a TORC1/2 inhibitor offers a therapeutic strategy to markedly improve ABT-263 activity in SCLC.

Genomic profiling of small-cell lung cancer: the era of targeted therapies

The molecular profiling of small-cell lung cancer is challenging because of the difficulty in obtaining suitable tumor samples for integrative genomic analysis. While an urgent need exists for well-defined and effective therapeutic targets in small-cell lung cancer, no significant improvement has been made in treating this disease over the past 30 years. Recently, three reports describing comprehensive genomic analyses of small-cell lung cancer have been published. These reports have provided a framework of biologically relevant genes in small-cell lung cancer and have demonstrated that the genomic landscape of small-cell lung cancer was almost equivalent between Asian and Caucasian populations. Of note, these three comprehensive genomic analyses and other molecular analyses of small-cell lung cancer have contributed to the identification of patient populations that may benefit from promising targeted agents, such as those affecting the PI3K/AKT/mTOR pathway, FGFR1, RET or AURORA kinase inhibitors. Targeting small-cell lung cancer cells with tumor suppressor gene alteration based on synthetic lethality is also promising. The present review provides an overview of the biologically relevant genetic alterations and targeted therapies of small-cell lung cancer focusing on recent discoveries that could impact the management of small-cell lung cancer.

A multicenter phase I/II study of obatoclax mesylate administered as a 3- or 24-hour infusion in older patients with previously untreated acute myeloid leukemia

PURPOSE

An open-label phase I/II study of single-agent obatoclax determined a maximum tolerated dose (MTD) and schedule, safety, and efficacy in older patients (≥ 70 yr) with untreated acute myeloid leukemia (AML).

EXPERIMENTAL DESIGN

Phase I evaluated the safety of obatoclax infused for 3 hours on 3 consecutive days (3 h × 3 d) in 2-week cycles. Initial obatoclax dose was 30 mg/day (3 h × 3 d; n = 3). Obatoclax was increased to 45 mg/day (3 h × 3 d) if ≤ 1 patient had a dose-limiting toxicity (DLT) and decreased to 20 mg/day (3 h × 3 d) if DLT occurred in ≥ 2 patients. In the phase II study, 12 patients were randomized to receive obatoclax at the dose identified during phase I (3 h × 3 d) or 60 mg/day administered by continuous infusion over 24 hours for 3 days (24 h × 3 d) to determine the morphologic complete response rate.

RESULTS

In phase I, two of three patients receiving obatoclax 30 mg/day (3 h × 3 d) experienced grade 3 neurologic DLTs (confusion, ataxia, and somnolence). Obatoclax was decreased to 20 mg/day (3 h × 3 d). In phase II, no clinically relevant safety differences were observed between the 20 mg/day (3 h × 3 d; n = 7) and 60 mg/day (24 h × 3 d; n = 5) arms. Neurologic and psychiatric adverse events were most common and were generally transient and reversible. Complete response was not achieved in any patient.

CONCLUSIONS

Obatoclax 20 mg/day was the MTD (3 h × 3 d) in older patients with AML. In the schedules tested, single-agent obatoclax was not associated with an objective response. Evaluation in additional subgroups or in combination with other chemotherapy modalities may be considered for future study.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00684918.

Obatoclax mesylate, a pan-bcl-2 inhibitor, in combination with docetaxel in a phase 1/2 trial in relapsed non-small-cell lung cancer

INTRODUCTION

The proapoptotic small-molecule pan-Bcl-2 inhibitor obatoclax mesylate (GX15-070) may enhance the cytotoxicity of chemotherapy in relapsed/refractory non-small-cell lung cancer (NSCLC).

METHODS

Obatoclax was administered with docetaxel in patients with relapsed or refractory NSCLC- docetaxel as a 1-hour infusion on day 1 and obatoclax as a 24-hour infusion on days 1 and 2-every 3 weeks for up to eight cycles. Four dose levels were evaluated in phase 1 (level 1: docetaxel 55 mg/m × 1 and obatoclax 30 mg × 2; levels 2-4: docetaxel 75 mg/m and obatoclax 30 mg, 45 mg, or 60 mg × 2) to identify dose-limiting toxicity and a phase 2 dose. In phase 2, response and tolerability were evaluated.

RESULTS

Eighteen patients were included in phase 1. Two dose-limiting toxicities occurred during cycle 1: one febrile neutropenia each at dose levels 3 and 4. Maximum tolerated dose was not reached; 32 patients (including 3 from phase 1) were treated in phase 2 with docetaxel 75 mg/m and obatoclax 60 mg (median 2 cycles). Three patients (11%) had partial responses in phase 2; two demonstrated stable disease lasting 12 weeks or more. Median duration of response was 4.8 months. Overall, median progression-free survival was 1.4 months. Neutropenia (31%), febrile neutropenia (16%), and dyspnea (19%) were the most common grade 3/4 adverse events observed.

CONCLUSIONS

Combined obatoclax mesylate plus docetaxel is tolerable in patients with NSCLC, but response was minimal and neutropenia was a common adverse event.

Advances in pharmacotherapy of small cell lung cancer

INTRODUCTION

Small cell lung cancer (SCLC) is an aggressive malignancy characterized by early metastatic dissemination and responsiveness to initial therapy. The incidence of SCLC has been declining over the past two decades. Limited-stage SCLC is a potentially curable disease with long-term survival of ∼ 20% when treated with platinum-based chemotherapy plus concurrent thoracic radiation and prophylactic cranial irradiation. For patients with extensive-stage SCLC, survival can be increased with combination platinum-based chemotherapy, but the disease remains incurable.

AREAS COVERED

This review looks at the current advances in pharmacotherapy for SCLC.

EXPERT OPINION

Many chemotherapeutic strategies and newer cytotoxic agents have been evaluated in SCLC, and some had promising activity in early clinical trials. However, none have demonstrated consistent improvements in outcome over standard platinum-based treatment. Similarly, although many potential molecular targets have been identified in preclinical studies of SCLC, molecularly targeted therapy has yet to demonstrate any substantial activity in clinical trials. Nonetheless, future advances in this disease will undoubtedly depend on improvements in our understanding of the molecular mechanisms that drive the proliferation and survival of SCLC cells.

Interferon alpha plus 13-cis-retinoic acid modulation of BCL-2 plus paclitaxel for recurrent small-cell lung cancer (SCLC): an Eastern Cooperative Oncology Group study (E6501)

BACKGROUND

Patients with recurrent small-cell lung cancer (SCLC) have dismal outcomes. The failure of salvage therapy is due to the possible development of resistance mechanisms, such as the upregulation of the anti-apoptosis protein, Bcl-2. We conducted a phase II study to evaluate if modulation of Bcl-2 with 13-cis-retinoic acid (13-CRA) and interferon alpha could improve response rates when combined with paclitaxel in patients with recurrent SCLC.

METHODS

Patients with recurrent SCLC and measurable disease were treated with interferon alpha at 6 million units/m² subcutaneously and 13-CRA 1 mg/kg orally on days 1 and 2 and paclitaxel 75 mg/m² intravenously on day 2 of each week for 6 weeks of an 8-week treatment cycle. Treatment was continued until disease progression, development of unacceptable toxicity, or withdrawal of consent. The primary endpoint was response rate with secondary endpoints of progression-free survival (PFS) and overall survival (OS). Bcl-2 levels were assessed in peripheral blood mononuclear cells (PBMCs).

RESULTS

Thirty-seven patients were enrolled; 34 were included in the intention-to-treat analysis as 3 patients were ineligible for the study. There were 3 partial responses (9 %), and 5 patients had stable disease (15 %) as best response. The median PFS was 2 months, and median OS was 6.2 months. Although mean Bcl-2 protein levels decreased with therapy in PBMCs, there was no association between Bcl-2 levels and response rate or survival.

CONCLUSION

Despite sound pre-clinical evidence, the addition of 13-CRA and interferon alpha to paclitaxel did not improve outcomes for recurrent SCLC.

Targeting the intrinsic apoptosis pathway as a strategy for melanoma therapy

Melanoma drug resistance is often attributed to abrogation of the intrinsic apoptosis pathway. Targeting regulators of apoptosis is thus considered a promising approach to sensitizing melanomas to treatment. The development of small-molecule inhibitors that mimic natural antagonists of either antiapoptotic members of the BCL-2 family or the inhibitor of apoptosis proteins (IAPs), known as BH3- or SMAC-mimetics, respectively, are helping us to understand the mechanisms behind apoptotic resistance. Studies using BH3-mimetics indicate that the antiapoptotic BCL-2 protein MCL-1 and its antagonist NOXA are particularly important regulators of BCL-2 family signaling, while SMAC-mimetic studies show that both XIAP and the cIAPs must be targeted to effectively induce apoptosis of cancer cells. Although most solid tumors, including melanoma, are insensitive to these mimetic drugs as single agents, combinations with other therapeutics have yielded promising results, and tests combining them with BRAF-inhibitors, which have already revolutionized melanoma treatment, are a clear priority.

Treatment of small cell lung cancer

Treatment of small cell lung cancer (SCLC) remains a significant challenge for the oncologists. Attempts to improve the results of first-line treatment have all failed so far and no real progress has been made in last years, emphasizing the need for novel strategies of treatment and the development of validated biomarkers. Patients with limited disease and good performance status should be considered for concomitant chemoradiotherapy, followed by prophylactic cranial irradiation. Patients with extensive disease should be treated with a platinum-based chemotherapy (cisplatin or carboplatin); chest radiotherapy can be considered in patients achieving extra-thoracic complete response and prophylactic cranial irradiation is recommended for patients responsive to initial chemotherapy. A large number of molecular-targeted drugs and immunomodulators are currently in clinical development: however, only a better understanding of molecular biology of SCLC and the identification of molecular markers predictive of response to targeted agents will lead to advances in the treatment of SCLC.