ABSTRACT
Small cell lung cancer (SCLC) is a rapidly growing, highly metastatic, and relatively immune-cold lung cancer subtype. Historically viewed in the laboratory and clinic as a single disease, new discoveries suggest that SCLC comprises multiple molecular subsets. Expression of MYC family members and lineage-related transcription factors ASCL1, NEUROD1, and POU2F3 (and, in some studies, YAP1) define unique molecular states that have been associated with distinct responses to a variety of therapies. However, SCLC tumors exhibit a high degree of intratumoral heterogeneity, with recent studies suggesting the existence of tumor cell plasticity and phenotypic switching between subtype states. While SCLC plasticity is correlated with, and likely drives, therapeutic resistance, the mechanisms underlying this plasticity are still largely unknown. Subtype states are also associated with immune-related gene expression, which likely impacts response to immune checkpoint blockade and may reveal novel targets for alternative immunotherapeutic approaches. In this review, we synthesize recent discoveries on the mechanisms of SCLC plasticity and how these processes may impinge on antitumor immunity.
Subject(s)
Lung Neoplasms , Small Cell Lung Carcinoma , Cell Line, Tumor , Gene Expression Regulation, Neoplastic , Humans , Lung Neoplasms/drug therapy , Lung Neoplasms/therapy , Small Cell Lung Carcinoma/genetics , Transcription Factors/metabolismABSTRACT
Neutrophil extracellular traps (NETs) can promote tumor growth and metastases, but whether NETs impact the tumor immune microenvironment remains underexplored. In this issue of Immunity, Teijeira et al. discover that NETs shield tumor cells from cytotoxic immune cells, resulting in impaired tumor clearance.
Subject(s)
Extracellular Traps , Neoplasms , Chemokines , Humans , Neutrophils , Tumor MicroenvironmentABSTRACT
ASCL1 is a neuroendocrine lineage-specific oncogenic driver of small cell lung cancer (SCLC), highly expressed in a significant fraction of tumors. However, â¼25% of human SCLC are ASCL1-low and associated with low neuroendocrine fate and high MYC expression. Using genetically engineered mouse models (GEMMs), we show that alterations in Rb1/Trp53/Myc in the mouse lung induce an ASCL1+ state of SCLC in multiple cells of origin. Genetic depletion of ASCL1 in MYC-driven SCLC dramatically inhibits tumor initiation and progression to the NEUROD1+ subtype of SCLC. Surprisingly, ASCL1 loss promotes a SOX9+ mesenchymal/neural crest stem-like state and the emergence of osteosarcoma and chondroid tumors, whose propensity is impacted by cell of origin. ASCL1 is critical for expression of key lineage-related transcription factors NKX2-1, FOXA2, and INSM1 and represses genes involved in the Hippo/Wnt/Notch developmental pathways in vivo. Importantly, ASCL1 represses a SOX9/RUNX1/RUNX2 program in vivo and SOX9 expression in human SCLC cells, suggesting a conserved function for ASCL1. Together, in a MYC-driven SCLC model, ASCL1 promotes neuroendocrine fate and represses the emergence of a SOX9+ nonendodermal stem-like fate that resembles neural crest.
Subject(s)
Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , SOX9 Transcription Factor/genetics , Small Cell Lung Carcinoma/genetics , Animals , Animals, Genetically Modified , Disease Models, Animal , Gene Expression Regulation, Neoplastic/genetics , Humans , Mice , Neural Crest/cytology , Small Cell Lung Carcinoma/physiopathology , Stem Cells/cytologyABSTRACT
The olfactory epithelium undergoes neuronal regeneration from basal stem cells and is susceptible to olfactory neuroblastoma (ONB), a rare tumor of unclear origins. Employing alterations in Rb1/Trp53/Myc (RPM), we establish a genetically engineered mouse model of high-grade metastatic ONB exhibiting a NEUROD1+ immature neuronal phenotype. We demonstrate that globose basal cells (GBCs) are a permissive cell of origin for ONB and that ONBs exhibit cell fate heterogeneity that mimics normal GBC developmental trajectories. ASCL1 loss in RPM ONB leads to emergence of non-neuronal histopathologies, including a POU2F3+ microvillar-like state. Similar to small-cell lung cancer (SCLC), mouse and human ONBs exhibit mutually exclusive NEUROD1 and POU2F3-like states, an immune-cold tumor microenvironment, intratumoral cell fate heterogeneity comprising neuronal and non-neuronal lineages, and cell fate plasticity-evidenced by barcode-based lineage tracing and single-cell transcriptomics. Collectively, our findings highlight conserved similarities between ONB and neuroendocrine tumors with significant implications for ONB classification and treatment.
Subject(s)
Cell Lineage , Esthesioneuroblastoma, Olfactory , Lung Neoplasms , Small Cell Lung Carcinoma , Animals , Mice , Small Cell Lung Carcinoma/genetics , Small Cell Lung Carcinoma/pathology , Small Cell Lung Carcinoma/metabolism , Humans , Esthesioneuroblastoma, Olfactory/genetics , Esthesioneuroblastoma, Olfactory/pathology , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Tumor Microenvironment , Nose Neoplasms/genetics , Nose Neoplasms/pathology , Olfactory Mucosa/pathology , Olfactory Mucosa/metabolism , Disease Models, Animal , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolismABSTRACT
Small cell lung cancer (SCLC) tumors comprise heterogeneous mixtures of cell states, categorized into neuroendocrine (NE) and non-neuroendocrine (non-NE) transcriptional subtypes. NE to non-NE state transitions, fueled by plasticity, likely underlie adaptability to treatment and dismal survival rates. Here, we apply an archetypal analysis to model plasticity by recasting SCLC phenotypic heterogeneity through multi-task evolutionary theory. Cell line and tumor transcriptomics data fit well in a five-dimensional convex polytope whose vertices optimize tasks reminiscent of pulmonary NE cells, the SCLC normal counterparts. These tasks, supported by knowledge and experimental data, include proliferation, slithering, metabolism, secretion, and injury repair, reflecting cancer hallmarks. SCLC subtypes, either at the population or single-cell level, can be positioned in archetypal space by bulk or single-cell transcriptomics, respectively, and characterized as task specialists or multi-task generalists by the distance from archetype vertex signatures. In the archetype space, modeling single-cell plasticity as a Markovian process along an underlying state manifold indicates that task trade-offs, in response to microenvironmental perturbations or treatment, may drive cell plasticity. Stifling phenotypic transitions and plasticity may provide new targets for much-needed translational advances in SCLC. A record of this paper's Transparent Peer Review process is included in the supplemental information.
Subject(s)
Lung Neoplasms , Small Cell Lung Carcinoma , Cell Plasticity , Humans , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Small Cell Lung Carcinoma/genetics , Small Cell Lung Carcinoma/metabolism , Small Cell Lung Carcinoma/pathologyABSTRACT
MYC stimulates both metabolism and protein synthesis, but how cells coordinate these complementary programs is unknown. Previous work reported that, in a subset of small-cell lung cancer (SCLC) cell lines, MYC activates guanosine triphosphate (GTP) synthesis and results in sensitivity to inhibitors of the GTP synthesis enzyme inosine monophosphate dehydrogenase (IMPDH). Here, we demonstrated that primary MYChi human SCLC tumors also contained abundant guanosine nucleotides. We also found that elevated MYC in SCLCs with acquired chemoresistance rendered these otherwise recalcitrant tumors dependent on IMPDH. Unexpectedly, our data indicated that IMPDH linked the metabolic and protein synthesis outputs of oncogenic MYC. Coexpression analysis placed IMPDH within the MYC-driven ribosome program, and GTP depletion prevented RNA polymerase I (Pol I) from localizing to ribosomal DNA. Furthermore, the GTPases GPN1 and GPN3 were upregulated by MYC and directed Pol I to ribosomal DNA. Constitutively GTP-bound GPN1/3 mutants mitigated the effect of GTP depletion on Pol I, protecting chemoresistant SCLC cells from IMPDH inhibition. GTP therefore functioned as a metabolic gate tethering MYC-dependent ribosome biogenesis to nucleotide sufficiency through GPN1 and GPN3. IMPDH dependence is a targetable vulnerability in chemoresistant MYChi SCLC.
Subject(s)
Guanosine Triphosphate/metabolism , Lung Neoplasms/metabolism , Proto-Oncogene Proteins c-myc/metabolism , Ribosomes/metabolism , Small Cell Lung Carcinoma/metabolism , Animals , Cell Line, Tumor , GTP Phosphohydrolases/genetics , GTP Phosphohydrolases/metabolism , GTP-Binding Proteins/genetics , GTP-Binding Proteins/metabolism , Guanosine Triphosphate/genetics , Humans , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Mice , Mutation , Proto-Oncogene Proteins c-myc/genetics , RNA Polymerase I/genetics , RNA Polymerase I/metabolism , Ribosomes/genetics , Ribosomes/pathology , Small Cell Lung Carcinoma/genetics , Small Cell Lung Carcinoma/pathologyABSTRACT
Small cell lung cancer (SCLC) is a neuroendocrine tumor treated clinically as a single disease with poor outcomes. Distinct SCLC molecular subtypes have been defined based on expression of ASCL1, NEUROD1, POU2F3, or YAP1. Here, we use mouse and human models with a time-series single-cell transcriptome analysis to reveal that MYC drives dynamic evolution of SCLC subtypes. In neuroendocrine cells, MYC activates Notch to dedifferentiate tumor cells, promoting a temporal shift in SCLC from ASCL1+ to NEUROD1+ to YAP1+ states. MYC alternatively promotes POU2F3+ tumors from a distinct cell type. Human SCLC exhibits intratumoral subtype heterogeneity, suggesting that this dynamic evolution occurs in patient tumors. These findings suggest that genetics, cell of origin, and tumor cell plasticity determine SCLC subtype.
Subject(s)
Gene Expression Regulation, Neoplastic , Lung Neoplasms/genetics , Neuroendocrine Tumors/genetics , Proto-Oncogene Proteins c-myc/genetics , Small Cell Lung Carcinoma/genetics , Animals , Cell Line, Tumor , Disease Models, Animal , Gene Expression Profiling/methods , Genetic Heterogeneity , Humans , Lung Neoplasms/metabolism , Mice, Knockout , Neuroendocrine Tumors/metabolism , Proto-Oncogene Proteins c-myc/metabolism , Receptors, Notch/genetics , Receptors, Notch/metabolism , Signal Transduction/genetics , Single-Cell Analysis , Small Cell Lung Carcinoma/metabolismABSTRACT
PURPOSE: Small-cell lung cancer (SCLC) has been treated clinically as a homogeneous disease, but recent discoveries suggest that SCLC is heterogeneous. Whether metabolic differences exist among SCLC subtypes is largely unexplored. In this study, we aimed to determine whether metabolic vulnerabilities exist between SCLC subtypes that can be therapeutically exploited. EXPERIMENTAL DESIGN: We performed steady state metabolomics on tumors isolated from distinct genetically engineered mouse models (GEMM) representing the MYC- and MYCL-driven subtypes of SCLC. Using genetic and pharmacologic approaches, we validated our findings in chemo-naïve and -resistant human SCLC cell lines, multiple GEMMs, four human cell line xenografts, and four newly derived PDX models. RESULTS: We discover that SCLC subtypes driven by different MYC family members have distinct metabolic profiles. MYC-driven SCLC preferentially depends on arginine-regulated pathways including polyamine biosynthesis and mTOR pathway activation. Chemo-resistant SCLC cells exhibit increased MYC expression and similar metabolic liabilities as chemo-naïve MYC-driven cells. Arginine depletion with pegylated arginine deiminase (ADI-PEG 20) dramatically suppresses tumor growth and promotes survival of mice specifically with MYC-driven tumors, including in GEMMs, human cell line xenografts, and a patient-derived xenograft from a relapsed patient. Finally, ADI-PEG 20 is significantly more effective than the standard-of-care chemotherapy. CONCLUSIONS: These data identify metabolic heterogeneity within SCLC and suggest arginine deprivation as a subtype-specific therapeutic vulnerability for MYC-driven SCLC.
Subject(s)
Arginine/metabolism , Energy Metabolism , Lung Neoplasms/genetics , Lung Neoplasms/metabolism , Proto-Oncogene Proteins c-myc/genetics , Small Cell Lung Carcinoma/genetics , Small Cell Lung Carcinoma/metabolism , Animals , Cell Line, Tumor , Disease Models, Animal , Humans , Lung Neoplasms/diagnostic imaging , Lung Neoplasms/pathology , Metabolic Networks and Pathways , Mice , Mice, Transgenic , Models, Biological , Signal Transduction , Small Cell Lung Carcinoma/diagnostic imaging , Small Cell Lung Carcinoma/pathology , TOR Serine-Threonine Kinases/metabolism , Xenograft Model Antitumor AssaysABSTRACT
MYC paralogs are frequently activated in small cell lung cancer (SCLC) but represent poor drug targets. Thus, a detailed mapping of MYC-paralog-specific vulnerabilities may help to develop effective therapies for SCLC patients. Using a unique cellular CRISPR activation model, we uncover that, in contrast to MYCN and MYCL, MYC represses BCL2 transcription via interaction with MIZ1 and DNMT3a. The resulting lack of BCL2 expression promotes sensitivity to cell cycle control inhibition and dependency on MCL1. Furthermore, MYC activation leads to heightened apoptotic priming, intrinsic genotoxic stress and susceptibility to DNA damage checkpoint inhibitors. Finally, combined AURK and CHK1 inhibition substantially prolongs the survival of mice bearing MYC-driven SCLC beyond that of combination chemotherapy. These analyses uncover MYC-paralog-specific regulation of the apoptotic machinery with implications for genotype-based selection of targeted therapeutics in SCLC patients.
Subject(s)
Apoptosis/genetics , Gene Expression Regulation, Neoplastic/genetics , Lung Neoplasms/genetics , Proto-Oncogene Proteins c-myc/metabolism , Small Cell Lung Carcinoma/genetics , Animals , Antineoplastic Agents/pharmacology , Antineoplastic Agents/therapeutic use , Apoptosis/drug effects , CRISPR-Cas Systems/genetics , Cell Line, Tumor , DNA Damage/drug effects , DNA Damage/genetics , Disease Models, Animal , Gene Expression Regulation, Neoplastic/drug effects , HEK293 Cells , Humans , Lung Neoplasms/drug therapy , Mice , Molecular Targeted Therapy/methods , Proto-Oncogene Proteins c-myc/genetics , RNA, Small Interfering/metabolism , Small Cell Lung Carcinoma/drug therapyABSTRACT
Small cell lung cancer (SCLC) is a rapidly lethal disease with few therapeutic options. We studied metabolic heterogeneity in SCLC to identify subtype-selective vulnerabilities. Metabolomics in SCLC cell lines identified two groups correlating with high or low expression of the Achaete-scute homolog-1 (ASCL1) transcription factor (ASCL1High and ASCL1Low), a lineage oncogene. Guanosine nucleotides were elevated in ASCL1Low cells and tumors from genetically engineered mice. ASCL1Low tumors abundantly express the guanosine biosynthetic enzymes inosine monophosphate dehydrogenase-1 and -2 (IMPDH1 and IMPDH2). These enzymes are transcriptional targets of MYC, which is selectively overexpressed in ASCL1Low SCLC. IMPDH inhibition reduced RNA polymerase I-dependent expression of pre-ribosomal RNA and potently suppressed ASCL1Low cell growth in culture, selectively reduced growth of ASCL1Low xenografts, and combined with chemotherapy to improve survival in genetic mouse models of ASCL1Low/MYCHigh SCLC. The data define an SCLC subtype-selective vulnerability related to dependence on de novo guanosine nucleotide synthesis.
Subject(s)
Basic Helix-Loop-Helix Transcription Factors/physiology , Guanosine/metabolism , IMP Dehydrogenase/physiology , Lung Neoplasms/enzymology , Small Cell Lung Carcinoma/enzymology , Animals , Basic Helix-Loop-Helix Transcription Factors/genetics , Cell Line, Tumor , Heterografts , Humans , IMP Dehydrogenase/antagonists & inhibitors , Mice , Mice, KnockoutABSTRACT
Small cell lung cancer (SCLC) is a recalcitrant cancer for which no new treatments have been approved in over 30 years. While molecular subtyping now guides treatment selection for patients with non-small cell lung cancer and other cancers, SCLC is still treated as a single disease entity. Using model-based clustering, we found two major proteomic subtypes of SCLC characterized by either high thyroid transcription factor-1 (TTF1)/low cMYC protein expression or high cMYC/low TTF1. Applying "drug target constellation" (DTECT) mapping, we further show that protein levels of TTF1 and cMYC predict response to targeted therapies including aurora kinase, Bcl2, and HSP90 inhibitors. Levels of TTF1 and DLL3 were also highly correlated in preclinical models and patient tumors. TTF1 (used in the diagnosis lung cancer) could therefore be used as a surrogate of DLL3 expression to identify patients who may respond to the DLL3 antibody-drug conjugate rovalpituzumab tesirine. These findings suggest that TTF1, cMYC or other protein markers identified here could be used to identify subgroups of SCLC patients who may respond preferentially to several emerging targeted therapies.
ABSTRACT
Loss of the tumor suppressors RB1 and TP53 and MYC amplification are frequent oncogenic events in small cell lung cancer (SCLC). We show that Myc expression cooperates with Rb1 and Trp53 loss in the mouse lung to promote aggressive, highly metastatic tumors, that are initially sensitive to chemotherapy followed by relapse, similar to human SCLC. Importantly, MYC drives a neuroendocrine-low "variant" subset of SCLC with high NEUROD1 expression corresponding to transcriptional profiles of human SCLC. Targeted drug screening reveals that SCLC with high MYC expression is vulnerable to Aurora kinase inhibition, which, combined with chemotherapy, strongly suppresses tumor progression and increases survival. These data identify molecular features for patient stratification and uncover a potential targeted treatment approach for MYC-driven SCLC.