The treatment of limited small cell lung cancer: a report of the progress made and future prospects

Multi-functional self-assembled nanoparticles for pVEGF-shRNA loading and anti-tumor targeted therapy

Although RNA interference (RNAi) technology shows great potential in cancer treatment, the tumor target delivery and sufficient cytosolic transport of RNAi agents are still the main obstacles for its clinical applications. Herein, we report a functional supramolecular self-assembled nanoparticle vector for RNAi agent loading and tumor target therapy. Molecular block adamantane-grafted poly(ethylene glycol) (Ad-PEG) was modified with epidermal growth factor receptor (EGFR)-specific binding ligand GE11 or pH-sensitive fusogenic peptide GALA and then used for self-assembly with cyclodextrin-grafted branched polyethylenimine (CD-PEI), adamantane-grafted polyamidoamine dendrimer (Ad-PAMAM), and plasmid DNA containing a small hairpin RNA expression cassette against vascular endothelial growth factor (VEGF) into functional DNA-loaded supramolecular nanoparticles (GE11&GALA-pshVEGF@SNPs) based on molecular recognition and charge interaction. These functional peptides facilitated the target cell binding, internalization, and endosomal escape of GE11&GALA-pshVEGF@SNPs, resulting in increased reporter gene expression and efficient targeted gene silencing. The systemic delivery of the GE11&GALA-pshVEGF@SNPs can efficiently downregulate the intratumoral VEGF protein levels, reduce blood vessel formation, and significantly inhibit A549 xenograft tumor growth. These results reveal the potential of these multifunctional self-assembled nanoparticles as a nucleic acid drug delivery system for the treatment of lung cancer.

Current and future therapeutic approaches for the treatment of small cell lung cancer

INTRODUCTION

Small-cell lung cancer (SCLC) is a very aggressive disease characterized by a high response rate to first-line chemotherapy, but most patients relapse within 1 year with disappointing results to second-line treatments. Chemotherapy has reached a plateau of effectiveness and new therapeutic strategies are needed to change the natural history of SCLC. Areas covered: This review will focus on the current results and the future development of the therapeutic approaches for the treatment of SCLC. Expert commentary: Immunotherapy is becoming a new frontier for the management of SCLC with preliminary interesting results. To date, no targeted drugs have been approved for clinical practice but several novel agents are in an advanced stage of clinical development in SCLC.

Anti-tumoral effect of desmethylclomipramine in lung cancer stem cells

Lung cancer is the most feared of all cancers because of its heterogeneity and resistance to available treatments. Cancer stem cells (CSCs) are the cell population responsible for lung cancer chemoresistance and are a very good model for testing new targeted therapies. Clomipramine is an FDA-approved antidepressant drug, able to inhibit in vitro the E3 ubiquitin ligase Itch and potentiate the pro-apoptotic effects of DNA damaging induced agents in several cancer cell lines. Here, we investigated the potential therapeutic effect of desmethylclomipramine (DCMI), the active metabolite of Clomipramine, on the CSCs homeostasis. We show that DCMI inhibits lung CSCs growth, decreases their stemness potential and increases the cytotoxic effect of conventional chemotherapeutic drugs. Being DCMI an inhibitor of the E3 ubiquitin ligase Itch, we also verified the effect of Itch deregulation on CSCs survival. We found that the siRNA-mediated depletion of Itch induces similar anti-proliferative effects on lung CSCs, suggesting that DCMI might exert its effect, at least in part, by inhibiting Itch. Notably, Itch expression is a negative prognostic factor in two primary lung tumors datasets, supporting the potential clinical relevance of Itch inhibition to circumvent drug resistance in the treatment of lung cancer.

Development of small RNA delivery systems for lung cancer therapy

RNA interference (RNAi) has emerged as a powerful tool for studying target identification and holds promise for the development of therapeutic gene silencing. Recent advances in RNAi delivery and target selection provide remarkable opportunities for translational medical research. The induction of RNAi relies on small silencing RNAs, which affect specific messenger RNA (mRNA) degradation. Two types of small RNA molecules, small interfering RNAs (siRNAs) and microRNAs (miRNAs), have a central function in RNAi technology. The success of RNAi-based therapeutic delivery may be dependent upon uncovering a delivery route, sophisticated delivery carriers, and nucleic acid modifications. Lung cancer is still the leading cause of cancer death worldwide, for which novel therapeutic strategies are critically needed. Recently, we have reported a novel platform (PnkRNA™ and nkRNA^®) to promote naked RNAi approaches through inhalation without delivery vehicles in lung cancer xenograft models. We suggest that a new class of RNAi therapeutic agent and local drug delivery system could also offer a promising RNAi-based strategy for clinical applications in cancer therapy. In this article, we show recent strategies for an RNAi delivery system and suggest the possible clinical usefulness of RNAi-based therapeutics for lung cancer treatment.

Lung cancer-initiating cells: a novel target for cancer therapy

Lung cancer is a major public health problem causing more deaths than any other cancer. A better understanding of the biology of this disease and improvements in treatment are greatly needed. Increasing evidence supports the concept that a rare and specialized population of cancer cells, so-called cancer-initiating cells with stem cell-like characteristics, is responsible for tumor growth, maintenance, and recurrence. Cancer-initiating cells also exhibit characteristics that render them resistant to both radiation and chemotherapy, and therefore they are believed to play a role in treatment failure. This has led to the hypothesis that traditional therapies that indiscriminately kill tumor cells will not be as effective as therapies that selectively target cancer-initiating cells. Investigating putative cancer-initiating cells in lung cancer will greatly benefit the understanding of the origins of this disease and may lead to novel approaches to therapy by suggesting markers for use in either further isolating this population for study or for selectively targeting these cells. This review will discuss (1) lung cancer, (2) stem cells, and the role of cancer-initiating cells in tumorigenesis; (3) markers and functional characteristics associated with lung cancer-initiating cells; and (4) the potential to selectively target this subpopulation of tumor cells.

Earlier detection of tumor treatment response using magnetic resonance diffusion imaging with oscillating gradients

An improved method for detecting early changes in tumors in response to treatment, based on a modification of diffusion-weighted magnetic resonance imaging, has been demonstrated in an animal model. Early detection of therapeutic response in tumors is important both clinically and in pre-clinical assessments of novel treatments. Noninvasive imaging methods that can detect and assess tumor response early in the course of treatment, and before frank changes in tumor morphology are evident, are of considerable interest as potential biomarkers of treatment efficacy. Diffusion-weighted magnetic resonance imaging is sensitive to changes in water diffusion rates in tissues that result from structural variations in the local cellular environment, but conventional methods mainly reflect changes in tissue cellularity and do not convey information specific to microstructural variations at sub-cellular scales. We implemented a modified imaging technique using oscillating gradients of the magnetic field for evaluating water diffusion rates over very short spatial scales that are more specific for detecting changes in intracellular structure that may precede changes in cellularity. Results from a study of orthotopic 9L gliomas in rat brains indicate that this method can detect changes as early as 24 h following treatment with 1,3-bis(2-chloroethyl)-1-nitrosourea, when conventional approaches do not find significant effects. These studies suggest that diffusion imaging using oscillating gradients may be used to obtain an earlier indication of treatment efficacy than previous magnetic resonance imaging methods.

Evidence for self-renewing lung cancer stem cells and their implications in tumor initiation, progression, and targeted therapy

The discovery of rare tumor cells with stem cell features first in leukemia and later in solid tumors has emerged as an important area in cancer research. It has been determined that these stem-like tumor cells, termed cancer stem cells, are the primary cellular component within a tumor that drives disease progression and metastasis. In addition to their stem-like ability to self-renew and differentiate, cancer stem cells are also enriched in cells resistant to conventional radiation therapy and to chemotherapy. The immediate implications of this new tumor growth paradigm not only require a re-evaluation of how tumors are initiated, but also on how tumors should be monitored and treated. However, despite the relatively rapid pace of cancer stem cell research in solid tumors such as breast, brain, and colon cancers, similar progress in lung cancer remains hampered in part due to an incomplete understanding of lung epithelial stem cell hierarchy and the complex heterogeneity of the disease. In this review, we provide a critical summary of what is known about the role of normal and malignant lung stem cells in tumor development, the progress in characterizing lung cancer stem cells and the potential for therapeutically targeting pathways of lung cancer stem cell self-renewal.

Timing of chest radiotherapy in patients with limited stage small cell lung cancer: a systematic review and meta-analysis of randomised controlled trials

BACKGROUND

We undertook a systematic review and literature-based meta-analysis to determine whether the timing of chest radiotherapy may influence the survival of patients with limited stage small cell lung cancer (LS-SCLC).

OBJECTIVES

To establish the most effective way of combining chest radiotherapy with chemotherapy for patients with limited-stage small cell lung cancer in order to improve long-term survival.

MATERIALS

Eligible studies were identified according to the Cochrane Collaboration Guidelines and were randomised controlled clinical trials comparing different timing of chest radiotherapy in patients with LS-SCLC. Early chest irradiation was defined as beginning within 30 days after the start of chemotherapy.

RESULTS

Seven randomised trials were eligible. The overall survival at 2 years or at 5 years was not significantly different between early or late chest radiotherapy. When only trials were considered that used platinum chemotherapy concurrent with chest radiotherapy, significantly higher 2 and 5-year survival rates were observed when chest radiotherapy (RT) was started within 30 days after the start of chemotherapy (2-year survival: HR: 0.73, 95% CI 0.57-0.94, p=0.01; 5-year survival: HR: 0.65, 95% CI 0.45-0.93, p=0.02). This was even more pronounced when the overall treatment time of chest radiotherapy was less than 30 days. In studies that did not show a survival advantage by early chest radiation, a lower dose-intensity of chemotherapy in the early vs. late arm was observed.

CONCLUSIONS

When platinum-based chemotherapy concurrently with chest RT is used, the 2- and 5-year survival rates of patients with LS-SCLC may be in favour of early chest radiotherapy, with a significant difference if the overall treatment time of chest radiation is less than 30 days.

Variation in the use of chemotherapy in lung cancer

Factors influencing the use of chemotherapy for the initial (6 months) treatment of lung cancer in South East England were investigated. The variables explored as possibly influencing the use of chemotherapy were sex, age, the year of diagnosis, the type of lung cancer, the stage, the index of multiple deprivation and the cancer network of residence. Chi2 analysis and multivariate logistic regression models were used to examine the effect of each of the variables on the use of chemotherapy. The results showed a highly significant trend in use of chemotherapy over time; the adjusted proportion of patients receiving chemotherapy increasing from 13.6% in 1994 to 29.3% in 2003. However, age, cancer network and type of lung cancer had the strongest influence on the use of chemotherapy. This finding is important when we consider that the NHS Cancer Plan aims at improving inequalities in cancer care in the UK.

Negligible influence of comorbidity on prognosis of patients with small cell lung cancer: a population-based study in the Netherlands

Management of small cell lung cancer (SCLC) among elderly is complex because of decreased organ functions and interactions with comorbidity. Since elderly patients are often excluded from clinical trials, little is known about the way they are treated and outcome. We evaluated the prognostic effects of rising age and comorbidity in unselected Dutch SCLC patients (Eindhoven Cancer Registry). Elderly patients received chemotherapy less often and the dose was also reduced more often. Cardiovascular diseases, hypertension or diabetes lowered the proportion receiving combined chemotherapy and radiotherapy among patients with limited disease. About 80% of the patients receiving chemotherapy suffered from a side effect, which was not related to age. After adjustment for age, gender, stage and treatment modality, comorbidity had a negligible prognostic effect. Chemotherapy (in combination with radiotherapy) seemed to improve survival, however, toxicity and quality of life in these patients should be evaluated thoroughly in future randomized studies.

Hedgehog signaling in small-cell lung cancer: frequent in vivo but a rare event in vitro

The hedgehog (HH) signaling pathway plays multiple roles during embryonic development and increasing evidence suggests that this embryonic pathway is involved in development and progression of several human cancers including those of the brain, skin, lung and gastrointestinal tract. To investigate HH signaling activity in small-cell lung cancer (SCLC), we have performed gene expression analysis on members of the HH pathway on a panel of 20 SCLC cell lines. Sonic hedgehog (SHH) expression was detected in only DMS79 and GLC16 and only DMS114 expressed detectable protein levels of GLI1, one of the key transcription factors of the pathway. Involvement of HH signaling in SCLC proliferation was investigated in a subset of cell lines using the HH signaling inhibitor cyclopamine or small interfering RNA (siRNA) against GLI1. Cells expressing GLI1 responded only weakly to both cyclopamine and RNA interference, suggesting that HH signaling plays only a minor role in the growth of SCLC cell lines. To investigate HH pathway activity in vivo, GLI1 immunohistochemistry was performed on SCLC tumors. Interestingly, GLI1 was expressed in most SCLC tumors studied, indicating that HH signaling is important for in vivo growth of SCLC but establishment of cell lines from SCLC tumors may lead to loss of expression of key HH pathway members. Thus, the data support the idea that the HH pathway may be a therapeutic target in SCLC. However, the data also suggest that the SCLC cells can circumvent the apparent in vivo requirement of HH signaling.

Thoracic radiation therapy for limited-stage small-cell lung cancer: unanswered questions

The role of thoracic radiation therapy (RT; TRT) is now established in the management of limited-stage small-cell lung cancer (SCLC). There is increasing evidence in the literature in favor of early concurrent chemoradiation therapy, and a gold standard of care for patients with a good performance status is twice-daily TRT (45 Gy in 3 weeks) with concurrent cisplatin/etoposide. Five-year survival rates > 20% can be expected with this combined-modality approach. Although current clinical trials are exploring the efficacy of new chemotherapeutic strategies for the disease, essential questions related to the optimization of TRT remain unanswered. In particular, the optimal RT dose, fractionation, and treatment volume have not been defined. This review highlights the need for well-designed multinational trials aimed at the optimization and standardization of RT for limited-stage SCLC. These trials should integrate translational research studies to investigate the molecular basis of RT resistance and to develop biomarker profiles of prognosis.

Thoracic Radiotherapy for Limited-stage Small-cell Lung Cancer: Controversies and Future developments

Thoracic radiotherapy has an established role in the management of limited-disease small-cell lung cancer (LD SCLC). However, essential questions relating to the optimisation of thoracic radiotherapy remain unanswered, including volume of irradiation, optimal total dose, fractionation, timing and sequencing of radiation. This review highlights the need for well-designed multi-national trials aimed at the optimisation and standardisation of radiotherapy for LD SCLC.

The insulinoma-associated 1: a novel promoter for targeted cancer gene therapy for small-cell lung cancer

The insulinoma-associated 1 (INSM1) gene is expressed exclusively during early embryonal development, but has been found re-expressed at high levels in neuroendocrine tumors. The regulatory region of the INSM1 gene is therefore a potential candidate for regulating expression of a therapeutic gene in transcriptionally targeted cancer gene therapy against neuroendocrine tumors. We analyzed expression of a reporter gene from a 1.7 kb region of the INSM1 promoter in a large number of small-cell lung cancer (SCLC) cell lines. This INSM1 promoter region showed very high levels of expression in most of the SCLC cell lines and expression was absent in cell lines of non-neuroendocrine origin. Inclusion of the general transcriptional enhancer from SV40 compromised the specificity of the promoter and did not enhance transcription in most of the SCLC cell lines. For comparison, the region of the gastrin releasing peptide (GRP) previously suggested for SCLC gene therapy was analyzed in a similar manner. High expression was observed for a number of cell lines, but unlike for the INSM1 promoter, reporter gene expression from the GRP promoter did not correlate to the relative GRP mRNA levels, demonstrating that this region may not contain all necessary regulatory elements. Expression of the suicide gene herpes simplex virus thymidine kinase (HSV-TK) from the INSM1 promoter in combination with treatment with the prodrug ganciclovir (GCV) caused a significant increase in GCV sensitivity specifically in INSM1-expressing cell lines. The INSM1 promoter is therefore a potential novel tool for transcriptionally targeted gene therapy for neuroendocrine tumors.

A meta-analysis of the timing of chest irradiation in the combined modality treatment of limited-stage small cell lung cancer

The objective of this study was to determine whether initial combined chemoradiation results in superior 1-, 2-, and 3-year survivals in the treatment of limited-stage small cell lung cancer versus sequential or split-course therapy. Using a prospective meta-analysis protocol outlining study inclusion criteria, literature search strategy, and statistical procedures, data from all available randomized controlled trials addressing the above-noted objective were pooled using a fixed effects model (Peto). Results were expressed as summary odds ratios (ORp), and statistical tests for data heterogeneity were performed prior to calculation of ORps. Odds ratios greater than 1.0 favored the experimental arm versus control (i.e., early chest irradiation). If statistical heterogeneity was demonstrated, sensitivity analyses were performed by previously described methods to evaluate possible sources of heterogeneity across the included studies. Pooling data from eight randomized controlled trials enrolling over 1,500 patients showed that early integration of chest radiotherapy with systemic chemotherapy increases overall survival by 34%-216%, depending on the end point of interest. Etoposide (E) plus cisplatin (P) in conjunction with chest irradiation appears to offer the greatest increase in survival versus delayed or split-course radiation therapy and non-EP-containing drug schedules. The available randomized trial data support early concurrent chest radiotherapy and systemic chemotherapy in the form of E and P in the management of limited-stage small cell lung cancer.

Early versus late chest radiotherapy for limited stage small cell lung cancer

BACKGROUND

It is standard clinical practice to combine chemotherapy and chest radiotherapy in treating patients with limited-stage small cell lung cancer. However, the best way to integrate both modalities is unclear.

OBJECTIVES

To establish the most effective way of combining chest radiotherapy with chemotherapy for patients with limited-stage small cell lung cancer in order to improve long-term survival.

SEARCH STRATEGY

The electronic databases MEDLINE, EMBASE, Cancerlit and the Cochrane Central Register of Controlled Trials (CENTRAL), reference lists, handsearching of journals and conference proceedings, and discussion with experts were used to identify potentially eligible trials, published and unpublished.

SELECTION CRITERIA

Randomised controlled clinical trials comparing different timing of chest radiotherapy in patients with limited-stage small cell lung cancer.

DATA COLLECTION AND ANALYSIS

Seven randomised trials were reviewed. There were differences in the timing and the overall treatment time of chest radiotherapy, the overall treatment time of , and the type of chemotherapy used.

MAIN RESULTS

No significant differences in the 2-year and the 5-year survival were found, whether chest radiotherapy was delivered within 30 days after the start of chemotherapy or later. When the only study that delivered chest radiotherapy during cycles of non-platinum chemotherapy was excluded, a trend for the 5-year survival was observed (RR:0.93, p=0.07) in favour of early radiation, but not for the 2-year survival. Survival at 5 years, but not at 2 years, was significantly better for those having early chest radiotherapy delivered in an overall treatment time of less than 30 days compared with a longer treatment time (RR: 0.90, p=0.006). These results, however, should be interpreted with caution because the largest trial has follow-up data at three years, but not later. It remains to be seen what the effect of longer follow up will be for 5-year survival rates. Local tumour control was not significantly different between early and late chest radiotherapy. The incidence of severe pneumonitis or severe oesophagitis was not significantly different for early versus late thoracic radiotherapy. However, a trend for a higher chance to develop pneumonitis when early chest radiotherapy was delivered during non-platinum based chemotherapy was observed.

AUTHORS' CONCLUSIONS

At present, it is uncertain whether the timing of chest radiotherapy as such is important for survival. The optimal integration of chemotherapy and chest radiotherapy in patients with limited-stage small cell lung cancer is unknown. Therefore, further research is needed to establish the most effective combination of radiotherapy and chemotherapy in this disease.

Phase I Study of Tirapazamine Plus Cisplatin/Etoposide and Concurrent Thoracic Radiotherapy in Limited-Stage Small Cell Lung Cancer (S0004)

PURPOSE

To determine the feasibility and a recommended phase II dose of tirapazamine when combined with chemoradiotherapy in limited-stage small cell lung cancer (LSCLC).

EXPERIMENTAL DESIGN

Concurrent chemoradiotherapy consisted of two cycles of cisplatin, etoposide, and once-daily radiation to 61 Gy. Tirapazamine (260 mg/m2) was given 1 h before cisplatin with planned dose escalation to 330 mg/m2 in the absence of dose-limiting toxicity, defined as > or =33% esophagitis (grade 3 or above). Consolidation therapy consisted of two cycles of tirapazamine (330 mg/m2), cisplatin, and etoposide. Complete responders received prophylactic cranial irradiation.

RESULTS

Thirty patients were enrolled at the 260 mg/m2 tirapazamine dose. All had performance status of 0-1. By comparison with S9713, a predecessor Southwest Oncology Group study in LSCLC that used the same concurrent chemoradiotherapy without tirapazamine, the present trial showed a higher rate of grade 3-4 esophagitis (34% versus 22%), vomiting (34% versus 23%), and febrile neutropenia (7% versus 2%). The consolidation phase was relatively well tolerated, with grade 4 neutropenia in 44% and febrile neutropenia in 5% of patients. There were two treatment-related deaths: one from neutropenic fever and one from respiratory infection. The overall response rate was 80%, and the median survival was 22 months.

CONCLUSIONS

Protocol-defined dose-limiting toxicity was observed at the initial tirapazamine dose, precluding dose escalation. Compared with S9713, the addition of tirapazamine increased the incidence of vomiting, neutropenia, and febrile neutropenia, although the overall toxicity profile remained acceptable. In view of the observed favorable survival, further study of tirapazamine in LSCLC is warranted.

Changes in gene expression associated with stable drug and radiation resistance in small cell lung cancer cells are similar to those caused by a single X-ray dose

Small cell lung cancer (SCLC) initially responds well to chemotherapy and fractionated radiotherapy, but resistance to these treatments eventually develops in the vast majority of cases. To understand how resistance develops in the H69 SCLC cell line, we compared the changes in gene expression associated with 37.5 Gy fractionated X-ray treatment that produced the stable radiation- and drug-resistant H69/R38 cell subline to the changes associated with a single 4- or 8-Gy X-ray treatment. Gene expression was determined by suppression subtractive hybridization combined with Northern blot analysis and two-dimensional (2D) protein electrophoresis. Stable radiation and drug resistance was associated with coordinate changes in the expression of genes of the cytoskeleton, protein synthesis, cell cycle, redox/stress and metabolic pathways. The pattern of these changes was remarkably similar to the changes seen 24 h after a single X-ray treatment of the H69 cells but differed from the changes in expression associated with a single X-ray treatment of the resistant H69/ R38 cells. Stable radiation and drug resistance may be caused by the constitutive expression of those genes transiently expressed by sensitive cells in response to a single X-ray dose. The repeated treatments received during fractionated irradiation may promote the change from a transient to a constitutive pattern of gene expression.

Prophylactic cranial irradiation in lung cancer

Patients with locally advanced lung cancer (non-small cell lung cancer or small cell lung cancer ) are threatened by concurrent risks of local, regional, and distant failure. By improving locoregional and systemic control within multimodality protocols, the brain emerges as one of the major relapse sites; therefore, prevention of brain relapse has become a primary focus of attention. Prophylactic cranial irradiation (PCI) has a high potential to reduce the risk of brain metastases. Clear evidence exists from meta-analysis that PCI improves overall and disease-free survival rates for patients with SCLC in complete remission. Long-term toxicities, predominantly neurocognitive impairments, represent potential risks, but within large prospective trials, including adequate control groups, late complications of clinical significance rarely have been observed. PCI is the recommended standard of care for the patients with limited disease SCLC in complete remission. As long as the optimal dose and fractionation remain to be defined in this setting, conventional fractionation with moderate total doses of approximately 30 Gy is preferred. In patients with locally advanced stage III non-small cell lung cancer treated within multimodality protocols, comparable relative risks for cumulative brain relapse have been demonstrated in long-term survivors. Although not the standard of care in this situation, the scientific community should be encouraged to further investigate PCI in these patient subgroups within carefully designed clinical trials, including untreated control arms.