Pathogenesis Of Small Cell Lung Cancer Research Articles

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.

Causal influence of gut microbiota on small cell lung cancer: a Mendelian randomization study.

Previous studies have hinted at a significant link between lung cancer and the gut microbiome, yet their causal relationship remains to be elucidated. GWAS data for small cell lung cancer (SCLC) was extracted from the FinnGen consortium, comprising 179 cases and 218 613 controls. Genetic variation data for 211 gut microbiota were obtained as instrumental variables from MiBioGen. Mendelian randomization (MR) was employed to determine the causal relationship between the two, with inverse variance weighting (IVW) being the primary method for causal analysis. The MR results were validated through several sensitivity analyses. The study identified a protective effect against SCLC for the genus Eubacterium ruminantium group (OR = 0.413, 95% CI: 0.223-0.767, p = 0.00513), genus Barnesiella (OR = 0.208, 95% CI: 0.0640-0.678, p = 0.00919), family Lachnospiraceae (OR = 0.319, 95% CI: 0.107-0.948, p = 0.03979), and genus Butyricimonas (OR = 0.376, 95% CI: 0.144-0.984, p = 0.04634). Conversely, genus Intestinibacter (OR = 3.214, 95% CI: 1.303-7.926, p = 0.01125), genus Eubacterium oxidoreducens group (OR = 3.391, 95% CI: 1.215-9.467, p = 0.01973), genus Bilophila (OR = 3.547, 95% CI: 1.106-11.371, p = 0.03315), and order Bacillales (OR = 1.860, 95% CI: 1.034-3.347, p = 0.03842) were found to potentially promote the onset of SCLC. We identified potential causal relationships between certain gut microbiota and SCLC, offering new insights into microbiome-mediated mechanisms of SCLC pathogenesis, resistance, mutations, and more.

Genetically-engineered mouse models of small cell lung cancer: the next generation.

Small cell lung cancer (SCLC) remains the most fatal form of lung cancer, with patients in dire need of new and effective therapeutic approaches. Modeling SCLC in an immunocompetent host is essential for understanding SCLC pathogenesis and ultimately discovering and testing new experimental therapeutic strategies. Human SCLC is characterized by near universal genetic loss of the RB1 and TP53 tumor suppressor genes. Twenty years ago, the first genetically-engineered mouse model (GEMM) of SCLC was generated using conditional deletion of both Rb1 and Trp53 in the lungs of adult mice. Since then, several other GEMMs of SCLC have been developed coupling genomic alterations found in human SCLC with Rb1 and Trp53 deletion. Here we summarize how GEMMs of SCLC have contributed significantly to our understanding of the disease in the past two decades. We also review recent advances in modeling SCLC in mice that allow investigators to bypass limitations of the previous generation of GEMMs while studying new genes of interest in SCLC. In particular, CRISPR/Cas9-mediated somatic gene editing can accelerate how new genes of interest are functionally interrogated in SCLC tumorigenesis. Notably, the development of allograft models and precancerous precursor models from SCLC GEMMs provides complementary approaches to GEMMs to study tumor cell-immune microenvironment interactions and test new therapeutic strategies to enhance response to immunotherapy. Ultimately, the new generation of SCLC models can accelerate research and help develop new therapeutic strategies for SCLC.

Biological Effects of CRISPR/Cas9-mediated Knockout of RAB27A in SCLC

Small cell lung cancer (SCLC) is characterized by rapid growth and early metastasis. Identifying new molecular targets are important in the pathogenesis of SCLC in order to develop new treatment strategies. RAB27A is the critical protein for intracellular exosome trafficking and is a driver of tumour progression. However, demonstrating the potential impact of suppressing RAB27A in SCLC as therapeutic approach is an important deficiency. RAB27A gene knockout SCLC cell lines were generated using a CRISPR/cas9 system. qRT-PCR, Western blotting and Sanger sequencing were performed to confirm RAB27A knockout in SCLC cells. TEM and EXOCET assays were used to detect the alteration of exosomes. Proliferation and colony formation were detected by MTT and microscopy. Subsequently, we intrapulmonally injected N417 and H524 SCLC cells(control and RAB27A knockout for each cell) into SCID mice. The effects of RAB27A knockout on mouse tumor model were analysed using 18F-FDG PET/CT scans.Knocking out RAB27A significantly decreased the expression of CD9, CD63, Tsg101, exosome secretion and exosomal protein in SCLC(p

A 15-Gene-Based Risk Signature for Predicting Overall Survival in SCLC Patients Who Have Undergone Surgical Resection.

Small cell lung cancer (SCLC) is a malignancy with a poor prognosis whose treatment has not progressed for decades. The survival benefit of surgery and the selection of surgical candidates are still controversial in SCLC. This study is the first report to identify transcriptomic alterations associated with prognosis and propose a gene expression-based risk signature that can be used to predict overall survival (OS) in SCLC patients who have undergone potentially curative surgery. An integrative transcriptome analysis of three gene expression datasets (GSE30219, GSE43346, and GSE149507) revealed 1734 up-regulated and 2907 down-regulated genes. Cox-Mantel test, Cox regression, and Lasso regression analyses were used to identify genes to be included in the risk signature. EGAD00001001244 and GSE60052-cohorts were used for internal and external validation, respectively. Overall survival was significantly poorer in patients with high-risk scores compared to the low-risk group. The discriminatory performance of the risk signature was superior to other parameters. Multivariate analysis showed that the risk signature has the potential to be an independent predictor of prognosis. The prognostic genes were enriched in pathways including regulation of transcription, cell cycle, cell metabolism, and angiogenesis. Determining the roles of the identified prognostic genes in the pathogenesis of SCLC may contribute to the development of new treatment strategies. The risk signature needs to be validated in a larger cohort of patients to test its usefulness in clinical decision-making.

Abstract 289: B7-H3 mediated metabolic reprogramming promotes small cell lung cancer progression

Abstract Lung cancer is the leading cause of cancer-related deaths worldwide. Small cell lung cancer (SCLC) is an aggressive subtype of lung cancer. The overall survival rate of SCLC is dismal owing to early metastasis, chemoresistance, higher rate of recurrence, and lack of available treatment options. Although some immunotherapeutic drugs have been approved for SCLC, they are effective only in a small fraction of the patient population. This necessitates the quest to find promising vulnerabilities against SCLC. Bioinformatic analysis on SCLC data set in the backdrop of various immune checkpoint regulators revealed B7-H3 as a promising target. The bioinformatics data was recapitulated in SCLC cell lines and human SCLC tissues. To delineate the effects of B7-H3 targeting, we performed CRISPR-Cas9 mediated B7-H3 knockout in SCLC cell lines. B7-H3 knockout in SCLC cells showed a decrease in colony formation, migration, and wound healing properties. Our results suggest that deletion of B7-H3 decrease the functional activities and activation of oncogenic signaling pathways, such as Erk, Akt, and Stat3. Further, we assessed if B7-H3 regulates SCLC metabolism. Preliminary data showed that B7-H3 knockout in SCLC cells inhibits glucose uptake, extracellular acidification rate (ECAR), and oxygen consumption rate (OCR), suggesting its role in SCLC metabolic reprogramming. Altogether, our data indicate that B7-H3 plays a crucial role in SCLC pathogenesis and could serve as a potential therapeutic target for SCLC. Citation Format: Mahek Fatima, Parvez Khan, Asad Ur Rehman, Md Arafat Khan, Shailendra Kumar Maurya, Aatiya Ahmad, Mohd Ali Zaidi, Shailendra Gautam, Subodh Lele, Surinder Kumar Batra, Mohd Wasim Nasser. B7-H3 mediated metabolic reprogramming promotes small cell lung cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 289.

NEMO- and RelA-dependent NF-κB signaling promotes small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive type of lung cancer driven by combined loss of the tumor suppressors RB1 and TP53. SCLC is highly metastatic and despite good initial response to chemotherapy patients usually relapse, resulting in poor survival. Therefore, better understanding of the mechanisms driving SCLC pathogenesis is required to identify new therapeutic targets. Here we identified a critical role of the IKK/NF-κB signaling pathway in SCLC development. Using a relevant mouse model of SCLC, we found that ablation of NEMO/IKKγ, the regulatory subunit of the IKK complex that is essential for activation of canonical NF-κB signaling, strongly delayed the onset and growth of SCLC resulting in considerably prolonged survival. In addition, ablation of the main NF-κB family member p65/RelA also delayed the onset and growth of SCLC and prolonged survival, albeit to a lesser extent than NEMO. Interestingly, constitutive activation of IKK/NF-κB signaling within the tumor cells did not exacerbate the pathogenesis of SCLC, suggesting that endogenous NF-κB levels are sufficient to fully support tumor development. Moreover, TNFR1 deficiency did not affect the development of SCLC, showing that TNF signaling does not play an important role in this tumor type. Taken together, our results revealed that IKK/NF-κB signaling plays an important role in promoting SCLC, identifying the IKK/NF-κB pathway as a promising therapeutic target.

Integrative epigenomic analyses of small cell lung cancer cells demonstrates the clinical translational relevance of gene body methylation

DNA methylation is a key regulator of gene expression and a clinical therapeutic predictor. We examined global DNA methylation beyond the generally used promoter areas in human small cell lung cancer (SCLC) and find that gene body methylation is a robust positive predictor of gene expression. Combining promoter and gene body methylation better predicts gene expression than promoter methylation alone including genes involved in the neuroendocrine classification of SCLC and the expression of therapeutically relevant genes including MGMT, SLFN11, and DLL3. Importantly, for super-enhancer (SE) covered genes such as NEUROD1 or MYC, using H3K27ac and NEUROD1, ASCL1, and POU2F3 ChIP-seq data, we show that genic methylation is inversely proportional to expression, thus providing a new approach to identify potential SE regulated genes involved in SCLC pathogenesis. To advance SCLC transitional research, these data are integrated into our web portal (https://discover.nci.nih.gov/SclcCellMinerCDB/) for open and easy access to basic and clinical investigators.

ASCL1 regulates super-enhancer-associated miRNAs to define molecular subtypes of small cell lung cancer.

Small cell lung cancer (SCLC) is a highly aggressive neuroendocrine tumor with dismal prognosis. Recently, molecular subtypes of SCLC have been defined by the expression status of ASCL1, NEUROD1, YAP1, and POU2F3 transcription regulators. ASCL1 is essential for neuroendocrine differentiation and is expressed in the majority of SCLC. Although previous studies investigated ASCL1 target genes in SCLC cells, ASCL1-mediated regulation of miRNAs and its relationship to molecular subtypes remain poorly explored. Here, we performed genome-wide profiling of chromatin modifications (H3K27me3, H3K4me3, and H3K27ac) by CUT&Tag assay and ASCL1 knockdown followed by RNA sequencing and miRNA array analyses in SCLC cells. ASCL1 could preferentially regulate genes associated with super-enhancers (SEs) defined by enrichment of H3K27ac marking. Moreover, ASCL1 positively regulated several SE-associated miRNAs, such as miR-7, miR-375, miR-200b-3p, and miR-429, leading to repression of their targets, whereas ASCL1 suppressed miR-455-3p, an abundant miRNA in other molecular subtypes. We further elucidated unique patterns of SE-associated miRNAs in different SCLC molecular subtypes, highlighting subtype-specific miRNA networks with functional relevance. Notably, we found apparent de-repression of common target genes of different miRNAs following ASCL1 knockdown, suggesting combinatorial action of multiple miRNAs underlying molecular heterogeneity of SCLC (e.g., co-targeting of YAP1 by miR-9 and miR-375). Our comprehensive analyses provide novel insights into SCLC pathogenesis and a clue to understanding subtype-dependent phenotypic differences.

Potential of Stem Cells and CART as a Potential Polytherapy for Small Cell Lung Cancer.

Despite the increasing urgency of the problem of treating small cell lung cancer (SCLC), information on the causes of its development is fragmentary. There is no complete understanding of the features of antitumor immunity and the role of the microenvironment in the development of SCLC resistance. This impedes the development of new methods for the diagnosis and treatment of SCLC. Lung cancer and chronic obstructive pulmonary disease (COPD) have common pathogenetic factors. COPD is a risk factor for lung cancer including SCLC. Therefore, the search for effective approaches to prevention, diagnosis, and treatment of SCLC in patients with COPD is an urgent task. This review provides information on the etiology and pathogenesis of SCLC, analyses the effectiveness of current treatment options, and critically evaluates the potential of chimeric antigen receptor T cells therapy (CART therapy) in SCLC. Moreover, we discuss potential links between lung cancer and COPD and the role of endothelium in the development of COPD. Finally, we propose a new approach for increasing the efficacy of CART therapy in SCLC.

Update 2021: Management of Small Cell Lung Cancer.

Accounting for 14% of lung cancer, small cell lung cancer (SCLC) is a highly aggressive neuroendocrine malignancy with rapid proliferation, early spread, and poor survival. We provide an overview of recent advances regarding SCLC pathogenesis, subtypes, and treatment development through literature review of key trials. There are no validated biomarkers or approved targeted treatments for this overly heterogeneous disease, but recent analyses have identified some promising targets and four major subtypes which may carry unique therapeutic vulnerabilities in SCLC. Treatment wise, only a third of patients present with limited stage SCLC, which can be managed with a combined modality approach with curative intent (usually chemo-radiotherapy, but in some eligible patients, surgery followed by systemic treatment). For advanced or extensive stage SCLC, combined chemotherapy (platinum-etoposide) and immunotherapy (atezolizumab or durvalumab during and after chemotherapy) has become the new standard front-line treatment, with modest improvement in overall survival. In the second-line setting, for disease relapse ≤ 6 months, topotecan, lurbinectedin, and clinical trials are reasonable treatment options; for disease relapse>6 months, original regimen, topotecan or lurbinectedin can be considered. Moreover, Trilaciclib, a CD4/CD6 inhibitor, was recently FDA-approved to decrease the incidence of chemotherapy-related myelosuppression in SCLC patients. While modest improvements in survival have been made especially in the metastatic setting with chemo-immunotherapy, further research in understanding the biology of SCLC is warranted to develop biomarker-driven therapeutic strategies and combinational approaches for this aggressive disease.

A Call to Action: Dismantling Racial Injustices in Preclinical Research and Clinical Care of Black Patients Living with Small Cell Lung Cancer.

Small cell lung cancer (SCLC) is an aggressive disease with dismal survival rates and limited therapeutic options. SCLC development is strongly associated with exposure to tobacco carcinogens. However, additional genetic and environmental risk factors that contribute to SCLC pathogenesis are beginning to emerge. Here, we specifically assess disparities pertaining to SCLC in Black populations. In contrast to non-small cell lung cancer, preliminary data suggest that Black individuals may actually be at a lower risk of developing SCLC relative to white individuals. This difference remains unexplained but urgently needs to be verified in larger data sets, because it could provide important new insights and approaches to understanding this recalcitrant tumor. Importantly, little biological information exists on SCLC in Black individuals, and few patient-derived preclinical SCLC models from diverse ancestries are available in the laboratory. Unfortunately, we note strikingly low numbers of Black participants in clinical trials testing new treatments for SCLC. Evidence further indicates that care for patients with SCLC may vary between communities with a large fraction of Black patients and those without. Together, these observations underscore the need to better investigate genetic, environmental, and socioeconomic factors associated with SCLC development, preclinical research, clinical care, and outcomes.

Small cell lung cancer (SCLC) incidence and trends vary by gender, geography, age, and subcategory based on population and hospital cancer registries in Hebei, China (2008–2017)

BackgroundLung cancer is the leading cause of morbidity and mortality worldwide. Small cell lung cancer (SCLC) has been determined to be the most lethal lung malignancy. Few studies have previously analyzed the epidemiological characteristics of SCLC in China. This study analyzed the epidemiological characteristics of SCLC aiming to provide a reference for the prevention of SCLC in Hebei Province.MethodsThe epidemiological characteristics of SCLC using lung cancer data based on population and hospital cancer registries in Hebei Province between 2008 and 2017 were analyzed.ResultsThe proportion of both population‐ and hospital‐based SCLC cases displayed a significant increasing trend. Moreover, the proportion of males was higher than that for female based on population‐ and hospital‐based cases. The proportion of hospital‐based SCLC cases in counties was higher than that in cities, whereas there were no significant regional differences between cities and counties based on population. The proportion of both population‐ and hospital‐based SCLC cases decreased consistently with increasing age. There was a difference between population‐ and hospital‐based distribution of subcategories of SCLC.ConclusionsSignificant increases in the proportion of both population‐ and hospital‐based SCLC cases over recent years, particularly in males and in patients aged over 55 years, were observed. Research on the pathogenesis of SCLC in these patients and prevention is urgently required.

Abstract A38: A critical role of Wnt5a-Axin2 axis in small-cell lung cancer development

Abstract The paucity of readily actionable alterations in the small-cell lung cancer (SCLC) genome necessitates exploration of alternative targets for clinical intervention, including reactivated developmental signaling pathways. Despite the widespread implication of deregulated WNT signaling in cancer, its role in the pathogenesis of SCLC remains unknown. In this study, we observe selective induction of Axin2, a target of WNT pathway, and its genetic reporter in the lung tumors developed in genetically engineered mouse models (GEMM) of SCLC. Intriguingly, however, other transcription targets of b-catenin-dependent “canonical” pathway are downregulated in tumors relative to normal lung, and knockout of Ctnnb1 encoding b-catenin does not affect tumor development in the GEMM. On the other hand, Axin2 knockout, which enhances b-catenin level, suppresses the tumor development. These findings suggest not only the dispensability of b-catenin-dependent pathway but also the significant role of Axin2 in SCLC. Meanwhile, we observe that tumors and cell lines express significantly higher levels of ligands for b-catenin-independent “noncanonical” pathway, including Wnt5a, than precancerous cells (preSC) as well as whole lung. Ectopic Wnt5a in preSC enhances cell proliferation in culture and tumorigenic capacity in athymic nude mice while increasing Axin2 expression. Depletion of Wnt5a suppresses cell proliferation and tumor development. Taken together, these results suggest a critical role of the Wnt5a-Axin2 axis in SCLC development. Citation Format: Kee-Beom Kim, Dong-Wook Kim, Youngchul Kim, Jae-Il Park, Kwon-Sik Park. A critical role of Wnt5a-Axin2 axis in small-cell lung cancer development [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr A38.

Identification of alternative splicing and lncRNA genes in pathogenesis of small cell lung cancer based on their RNA sequencing

The molecular mechanisms involved in small-cell lung cancer (SCLC) are largely unknown. Recent studies have suggested that long non-coding RNAs (lncRNAs) are likely to play a critical role. There is an urgent need for suitable molecular biomarkers for SCLC diagnosis and for assessing patient prognosis. In this study, we used public databases to identify mRNA-like candidate lncRNAs. A multi-step computational approach was used to construct a functional SCLC lncRNAs-mediated competing with endogenous RNA (ceRNA) network (LMCN) by integrating genome-wide lncRNAs and mRNA expression profiles, miRNA-target interactions, functional analyses, and clinical survival analyses. The results revealed the significance of lncRNAs interactions with ceRNAs in SCLC, indicating that integration of expression profiles and alternative splicing could be used to identify biomarkers and the underlying pathological changes. The following genes: EPB41L4A-AS1, HOXA-AS2, XIST, DLEU2, FGD5-AS1, ALMS1-IT1, SNHG12, MIR17HG, MIR4720, and SCARNA10 in cluster, as well as shared alternative splicing events, were considered to be critical genes. Olfactory transduction and endocytosis were the top-enriched pathways in SCLC. The selected cluster, including critical genes, might also be a potential pathway of SCLC pathogenesis. As a result, this research provides the perspective information to explore the potential critical genes and its pathways in SCLC therapy.

Identification of candidate genes associated with the pathogenesis of small cell lung cancer via integrated bioinformatics analysis.

The pathogenesis of small cell lung cancer (SCLC), a highly metastatic malignant tumor, remains unclear. In the present study, important genes and pathways that are involved in the pathogenesis of SCLC were identified. The following four datasets were downloaded from the Gene Expression Omnibus: GSE60052, GSE43346, GSE15240 and GSE6044. The differentially expressed genes (DEGs) between the SCLC samples and the normal samples were analyzed using R software. The limma package was used for every dataset. The RobustRankAggreg package was used to integrate the DEGs from the four datasets. Functional and pathway enrichment analyses were conducted using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases with FunRich software and R software, respectively. In addition, the protein-protein interaction (PPI) network of the DEGs was constructed using the STRING database and Cytoscape software. Hub genes and significant modules were identified using Molecular Complex Detection in Cytoscape software. Finally, the expression values of hub genes were determined using the Oncomine online database. In total, 412 DEGs were identified following the integration of the four datasets, with 146 upregulated genes and 266 downregulated genes. The upregulated DEGs were primarily enriched in the cell cycle, cell division and microtubule binding. The downregulated DEGs were primarily enriched in the complement and coagulation cascades, the cytokine-mediated signaling pathway and protein binding. Eight hub genes and 1 significant module correlated to the cell cycle pathway were identified based on a subset of the PPI network. Finally, five hub genes were identified as highly expressed in SCLC tissue compared with normal tissue. The cell cycle pathway may be the pathway most closely associated with the pathogenesis of SCLC. NDC80, BUB1B, PLK1, CDC20 and MAD2L1 should be the focus of follow-up studies regarding the diagnosis and treatment of SCLC.

MiR-216a-5p inhibits malignant progression in small cell lung cancer: involvement of the Bcl-2 family proteins.

ObjectivemicroRNAs are regulatory molecules regarded as important in the pathogenesis of different types of tumors. microRNA-216a (miR-216a-5p) has been identified as a tumor suppressor in multiple malignancies. However, the role of miR-216a-5p in the pathogenesis of small cell lung cancer (SCLC) remains obscure. The objective of this study was to investigate the role of the miR-216a-5p/Bcl-2 axis in SCLC pathogenesis.Materials and methodsAll the experimental methods used were as follows: microarray analysis, cell culture, transient, and stable gene transfection; real-time fluorescence PCR; Western blot; flow cytometry for cell cycle analysis; in vitro proliferation assay; in vitro wound healing experiment; in vivo xenograft model in nude mice; and dual luciferase reporter assay. All statistical analyses were carried out using GraphPad Prism 7 software. Statistical significance was analyzed by Student’s t-test or one-way ANOVA. P <0.05 (typically compared with the negative control group) was considered as significant and is marked with an asterisk in the figures.ResultsIn this study, we observed that miR-216a-5p is downregulated in SCLC cell lines compared to that in the normal human bronchial epithelial cell line 16-HBE. In vitro and in vivo experiments demonstrate that upregulation of miR-216a-5p significantly decreased cell growth and migration and its downregulation increased SCLC cell proliferation and migration and influenced the cell cycle. Using bioinformatics analyses, we predicted that the important antiapoptotic gene Bcl-2 is targeted by miR-216a-5p, and we identified a functional miR-216a-5p binding site in the 3′-UTR of Bcl-2 using luciferase reporter assay. Furthermore, we determined that suppression of miR-216a-5p modulated the expression of Bcl-2, Bax, and Bad proteins (Bcl-2 family proteins), while Bcl-2 knockdown abrogated the effect of miR-216a-5p downregulation on cell proliferation, cell migration, and the cell cycle.ConclusionTaken together, these findings suggest that miR-216a-5p regulates SCLC biology via Bcl-2 family proteins. Therefore, our study highlights the role of the miR-216a-5p/Bcl-2 axis in SCLC pathogenesis.

P3.12-14 Genomic Profiling of Chinese Small Cell Lung Cancer and the Implications for Therapy

Small cell lung cancer (SCLC) is one of the deadliest malignancies and accounts for nearly 15% of lung cancers. The 5-year survival rate for SCLC is very low. Previous study had revealed the genomic characterization of SCLC in Western patients. However, little is known about that in Chinese SCLC patients. FFPE tumor and matched blood samples of 79 Chinese SCLC patients, including 60 males (median age of 60 years old) and 19 females (median age of 59 years old), were collected for next generation sequencing to detect 450 cancer related genes. All histological diagnoses were confirmed by independent pathologists. Genomic alterations including single nucleotide substitutions (SNV), short and long insertions/deletions (Indel), copy number variations (CNV), and gene rearrangement in selected genes were assessed. The most frequently altered genes in 79 Chinese SCLC patients were TP53 (94.9%), RB1 (83.5%), LRP1B (22.8%), KMT2D (13.9%), NOTCH1 (12.7%), FAM135B (11.4%), FAT1 (11.4%), KDR (11.4%), SPTA1 (10.1%) and STK24 (10.1%). Four of the patients harbored EGFR alterations including one EGFR fusion. Copy number variation analysis revealed that the most frequent variations occurred in the long arm of chromosome 13, including amplifications of STK24, FGF14, IRS2 and TNFSF13B (10.1%, 8/79, located at 13q32∼13q34) and deletion of RB1 and BRCA2 (59.5%, 47/79, located at 13q13∼13q14). Compared to the previously reported 25% mutational frequency in Western cohort reported previously, 31.6% (25/79) of our patients exhibited alterations in NOTCH signaling pathway related genes (NOTCH1, NOTCH2, NOTCH3, NOTCH4, EP300 and CREBBP). Around 15.2% (12/79) patients had PI3K/AKT/mTOR signaling pathway alterations (PIK3CA, MTOR, PTEN, and TSC2). Homologous Recombination Deficiency (HRD) related genes altered in 17.7% (14/79) patients, suggesting the potential clinical benefits from PARP inhibitors. The genomic alterations of FGF family members occurred in 25.3% (20/79) of patients. Other targetable genes included KIT (7.6%, n = 6), PDGFRA (5.1%, n = 4) and DDR2 (2.5%, n = 2). In this study, we characterized the genomic alteration profile of Chinese SCLC patients. Our discovery of CNV in the long arm of chromosome 13 might be helpful in understanding the pathogenesis of SCLC. Consistent with previous report, high mutation rates of TP53 and RB1 are the most important genomic features of SCLC [PMID: 26168399]. In addition, we also found several targetable gene variations including HRD, FGF family, KIT, PDGFRA and DDR2, which might provide potential targeted therapy options for SCLC patients. Further association analyses of these genomic alterations with clinical features in SCLC are still needed.

MicroRNA-26b suppresses tumorigenicity and promotes apoptosis in small cell lung cancer cells by targeting myeloid cell leukemia 1 protein

The aim of this study was to investigate the role of microRNA-26b (miR-26b) in regulating the proliferation, migration, and apoptosis of small cell lung cancer (SCLC) cells. First, we examined the expression level of miR-26b in human normal fetal lung fibroblasts (NFLFs) and three SCLC cell lines NCI-H466, NCI-H1688, and NCI-H196. In the following experiments, the three SCLC cell lines were transfected with miR-26b mimic and inhibitor. Cell growth and survival, as well as migration and invasion capacities were determined by MTT, colony formation, Transwell migration and invasion, and wound healing assays. Cell apoptosis, production of reactive oxygen species, and mitochondrial membrane potential were also measured in the three cell lines following various treatments. As a result, we found that the level of miR-26b was significantly lower in SCLC cells than in NFLFs. Additionally, transfection with miR-26b mimic could inhibit proliferation, colony formation, and migration, as well as induce apoptosis in these SCLC cell lines; while miR-26b inhibitor showed the opposite effects. Further mechanistic experiment revealed that miR-26b could suppress the expression of myeloid cell leukemia 1 protein (Mcl-1) and the 3′-untranslated region (3′-UTR) of Mcl-1 may be the direct binding site of miR-26b, suggesting that the effect of miR-26b may be mediated by targeting Mcl-1. Collectively, our findings offer a new insight into the role of miR-26b in the pathogenesis of SCLC, and provide primary evidence supporting the potential of miR-26b-based therapy for the treatment of SCLC.

TRP53 Mutants Drive Neuroendocrine Lung Cancer Through Loss-of-Function Mechanisms with Gain-of-Function Effects on Chemotherapy Response.

Lung cancer is the leading cause of cancer-related deaths with small-cell lung cancer (SCLC) as the most aggressive subtype. Preferential occurrence of TP53 missense mutations rather than loss implicates a selective advantage for TP53-mutant expression in SCLC pathogenesis. We show that lung epithelial expression of R270H and R172H (R273H and R175H in humans), common TRP53 mutants in lung cancer, combined with RB1 loss selectively results in two subtypes of neuroendocrine carcinoma, SCLC and large cell neuroendocrine carcinoma (LCNEC). Tumor initiation and progression occur in a remarkably consistent time frame with short latency and uniform progression to lethal metastatic disease by 7 months. R270H or R172H expression and TRP53 loss result in similar phenotypes demonstrating that TRP53 mutants promote lung carcinogenesis through loss-of-function and not gain-of-function mechanisms. Tumor responses to targeted and cytotoxic therapeutics were discordant in mice and corresponding tumor cell cultures demonstrating need to assess therapeutic response at the organismal level. Rapamycin did not have therapeutic efficacy in the mouse model despite inhibiting mTOR signaling and markedly suppressing tumor cell growth in culture. In contrast, cisplatin/etoposide treatment using a patient regimen prolonged survival with development of chemoresistance recapitulating human responses. R270H, but not R172H, expression conferred gain-of-function activity in attenuating chemotherapeutic efficacy. These data demonstrate a causative role for TRP53 mutants in development of chemoresistant lung cancer, and provide tractable preclinical models to test novel therapeutics for refractory disease. Mol Cancer Ther; 16(12); 2913-26. ©2017 AACR.