ASCL1 is a lineage oncogene providing therapeutic targets for high-grade neuroendocrine lung cancers

An organoid library unveils subtype-specific IGF-1 dependency via a YAP-AP1 axis in human small cell lung cancer

Small cell lung cancer (SCLC) is a devastating disease with limited therapeutic advancements. Although SCLC has recently been classified into four molecular subtypes, subtype-specific therapies are still lacking. Here, we established 40 patient-derived SCLC organoid lines with predominant TP53 and RB1 alterations and rare targetable genetic lesions. Transcriptome profiling divided the SCLC organoids into neuroendocrine (NE)-type SCLC and non-NE-type SCLC, with the latter characterized by YAP1 or POU2F3 expression. NE-type SCLC organoids grew independent of alveolar niche factors, whereas non-NE-type SCLC organoids relied on insulin-like growth factor (IGF)-1-driven YAP1 and AP1 activation. Therapeutic targeting of IGF-1, YAP1 and AP1 effectively suppressed the growth of non-NE-type organoids. Co-knockout of TP53 and RB1 in human alveolar cells altered their lineage toward the airway epithelium-like fate and conferred IGF-1 dependency, validating the subtype-phenotype connection. Our SCLC organoid library represents a valuable resource for developing biology-based therapies and has the potential to reshape the drug discovery landscape.

Functional characterization of the ATOH1 molecular subtype indicates a pro-metastatic role in small cell lung cancer

Molecular subtypes of small cell lung cancer (SCLC) have been described based on differential expression of the transcription factors (TFs) ASCL1, NEUROD1, and POU2F3 and immune-related genes. We previously reported an additional subtype based on expression of the neurogenic TF ATOH1 within our SCLC circulating tumor cell-derived explant (CDX) model biobank. Here, we show that ATOH1 protein is detected in 7 of 81 preclinical models and 16 of 102 clinical samples of SCLC. In CDX models, ATOH1 directly regulates neurogenesis and differentiation programs, consistent with roles in normal tissues. In ex vivo cultures of ATOH1+ CDXs, ATOH1 is required for cell survival. In vivo, ATOH1 depletion slows tumor growth and suppresses liver metastasis. Our data validate ATOH1 as a bona fide lineage-defining TF of SCLC with cell survival and pro-metastatic functions. Further investigation exploring ATOH1-driven vulnerabilities for targeted treatment with predictive biomarkers is warranted.

Circular RMST cooperates with lineage-driving transcription factors to govern neuroendocrine transdifferentiation

Circular RNA (circRNA) is a class of noncoding RNA with regulatory potentials. Its role in the transdifferentiation of prostate and lung adenocarcinoma into neuroendocrine prostate cancer (NEPC) and small cell lung cancer (SCLC) remains unexplored. Here, we identified circRMST as an exceptionally abundant circRNA predominantly expressed in NEPC and SCLC, with strong conservation between humans and mice. Functional studies using shRNA, siRNA, CRISPR-Cas13, and Cas9 consistently demonstrate that circRMST is essential for tumor growth and the expression of ASCL1, a master regulator of neuroendocrine fate. Genetic knockout of Rmst in NEPC genetic engineered mouse models prevents neuroendocrine transdifferentiation, maintaining tumors in an adenocarcinoma state. Mechanistically, circRMST physically interacts with lineage transcription factors NKX2-1 and SOX2. Loss of circRMST induces NKX2-1 protein degradation through autophagy-lysosomal pathway and alters the genomic binding of SOX2, collectively leading to the loss of ASCL1 transcription.

Challenges of small cell lung cancer heterogeneity and phenotypic plasticity

Small cell lung cancer (SCLC) is an aggressive neuroendocrine malignancy with ~7% 5-year overall survival reflecting early metastasis and rapid acquired chemoresistance. Immunotherapy briefly extends overall survival in ~15% cases, yet predictive biomarkers are lacking. Targeted therapies are beginning to show promise, with a recently approved delta-like ligand 3 (DLL3)-targeted therapy impacting the treatment landscape. The increased availability of patient-faithful models, accumulating human tumour biobanks and numerous comprehensive molecular profiling studies have collectively facilitated the mapping and understanding of substantial intertumoural and intratumoural heterogeneity. Beyond the almost ubiquitous loss of wild-type p53 and RB1, SCLC is characterized by heterogeneously mis-regulated expression of MYC family members, yes-associated protein 1 (YAP1), NOTCH pathway signalling, anti-apoptotic BCL2 and epigenetic regulators. Molecular subtypes are based on the neurogenic transcription factors achaete-scute homologue 1 (ASCL1) and neurogenic differentiation factor 1 (NEUROD1), the rarer non-neuroendocrine transcription factor POU class 2 homeobox 3 (POU2F3), and immune- and inflammation-related signatures. Furthermore, SCLC shows phenotypic plasticity, including neuroendocrine-to-non-neuroendocrine transition driven by NOTCH signalling, which is associated with disease progression, chemoresistance and immune modulation and, in mouse models, with metastasis. Although these features pose substantial challenges, understanding the molecular vulnerabilities of transcription factor subtypes, the functional relevance of plasticity and cell cooperation offer opportunities for personalized therapies informed by liquid and tissue biomarkers.

The role of transcription factors in prostate cancer progression

Prostate cancer is one of the most common malignancies in men, with most cases initially responding to androgen deprivation therapy. However, a significant number of patients eventually develop castration-resistant prostate cancer, an aggressive form of the disease. Although androgen receptor (AR) pathway inhibitors target AR signaling, and have extended survival in patients with castration-resistant prostate cancer, prolonged treatment can lead to the emergence of neuroendocrine prostate cancer (NEPC), a lethal subtype characterized by the expression of neuroendocrine markers and reduced AR activity. The transition from adenocarcinoma to NEPC is driven by lineage plasticity, wherein cancer cells adopt a neuroendocrine phenotype to evade treatment. Consequently, NEPC patients face poor clinical outcomes and limited effective treatment options. To improve outcomes, it is crucial to understand the molecular mechanisms driving NEPC development. In this review, we highlight the role of transcription factors in this process and explore their potential as therapeutic targets.

Lethal co-expression intolerance underlies the mutually exclusive expression of ASCL1 and NEUROD1 in SCLC cells

Small cell lung cancer (SCLC) subtypes, defined by the expression of lineage-specific transcription factors (TFs), are thought to be mutually exclusive, with intra-tumoral heterogeneities. This study investigated the mechanism underlying this phenomenon with the aim of identifying a novel vulnerability of SCLC. We profiled the expression status of ASCL1, NEUROD1, POU2F3, and YAP1 in 151 surgically obtained human SCLC samples. On subtyping, a high degree of mutual exclusivity was observed between ASCL1 and NEUROD1 expression at the cell, but not tissue, level. Inducible co-expression models of all combinations of ASCL1, NEUROD1, POU2F3, YAP1, and ATOH1 using SCLC cell lines showed that some expression combinations, such as ASCL1 and NEUROD1, exhibited mutual repression and caused growth inhibition and apoptosis. Gene expression and ATAC-seq analyses of the ASCL1 and NEUROD1 co-expression models revealed that co-expression of ASCL1 in NEUROD1-driven cells, and of NEUROD1 in ASCL1-driven cells, both (although more efficiently by the former) reprogrammed the cell lineage to favor the ectopically expressed factor, with rewiring of chromatin accessibility. Mechanistically, co-expressed NEUROD1 in ASCL1-driven SCLC cells caused apoptosis by downregulating BCL2, likely in a MYC-independent manner. In conclusion, lethal co-expression intolerance underlies the mutual exclusivity between these pioneer TFs, ASCL1 and NEUROD1, in an SCLC cell. Further investigation is warranted to enable therapeutic targeting of this vulnerability.

Defined cellular reprogramming of androgen receptor-active prostate cancer to neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC) arises primarily through neuroendocrine transdifferentiation (NEtD) as an adaptive mechanism of therapeutic resistance. Models to define the functional effects of putative drivers of this process on androgen receptor (AR) signaling and NE cancer lineage programs are lacking. We adapted a genetically defined strategy from the field of cellular reprogramming to directly convert AR-active prostate cancer (ARPC) to AR-independent NEPC using candidate factors. We delineated critical roles of the pioneer factors ASCL1 and NeuroD1 in NEtD and uncovered their abilities to silence AR expression and signaling by remodeling chromatin at the somatically acquired AR enhancer and global AR binding sites with enhancer activity. We also elucidated the dynamic temporal changes in the transcriptomic and epigenomic landscapes of cells undergoing acute lineage conversion from ARPC to NEPC which should inform future therapeutic development. Further, we distinguished the activities of ASCL1 and NeuroD1 from the inactivation of RE-1 silencing transcription factor (REST), a master suppressor of a major neuronal gene program, in establishing a NEPC lineage state and in modulating the expression of genes associated with major histocompatibility complex class I (MHC I) antigen processing and presentation. These findings provide important, clinically relevant insights into the biological processes driving NEtD of prostate cancer.

An integrative analysis of ASCL1 in breast cancer and inhibition of ASCL1 increases paclitaxel sensitivity by activating ferroptosis via the CREB1/GPX4 axis

Objective

Our previous study found that Achaete-scute complex homolog 1 (ASCL1) is involved in classifying BC subtypes with different prognostic and pathological characteristics. However, the biological role of ASCL1 in BC still remains largely unexplored. This study aims to elucidate the function of ASCL1 in BC using bioinformatics analyses, as well as in vitro and in vivo experimental approaches.

Methods

Data from the TCGA, GEO, and Human Protein Atlas databases were utilized to evaluate ASCL1 expression in BC and its association with patient prognosis. Genetic alterations in ASCL1 were assessed through the COSMIC and cBioPortal databases, while the TIMER2.0 database provided insights into the relationship between ASCL1 expression and key gene mutations in BC. The GDSC database was used to examine correlations between ASCL1 levels and sensitivity to standard chemotherapeutic agents. Associations between ASCL1 expression and cytokines, immunomodulatory factors, MHC molecules, and receptors were analyzed using Pearson and Spearman correlation methods. The TIP database was employed to investigate the connection between ASCL1 expression and immunoreactivity scores, and six computational approaches were applied to evaluate immune cell infiltration. Functional assays were conducted on BC cell lines MCF-7 and MDA-MB-231, and nude mouse models were used for in vivo studies.

Results

ASCL1 was found to be upregulated in BC and correlated with unfavorable prognosis and mutations in key oncogenes. Its expression was linked to immunomodulatory factors, immune cell infiltration, and immunoreactivity scores in the tumor microenvironment. Additionally, ASCL1 influenced tumor immune dynamics and chemosensitivity in BC. Overexpression of ASCL1 enhanced BC cell proliferation, migration and invasion, while its knockdown had the opposite effect. Notably, inhibition of ASCL1 increased BC cell sensitivity to paclitaxel both in vitro and in vivo. In addition, inhibition of ASCL1 activated ferroptosis in BC, including altered mitochondrial morphology, increased MDA and ROS levels, decreased GSH levels and reduced GSH/GSSG ratio. Mechanistically, inhibition of ASCL1 decreases the phosphorylation of CREB1, thus reducing the expression of GPX4. In summary, inhibition of ASCL1 increases paclitaxel sensitivity by activating ferroptosis via the CREB1/GPX4 axis.

Conclusions

ASCL1 exerts oncogenic effects in BC and represents a potential therapeutic target for intervention.

Practical management of adverse events in patients receiving tarlatamab, a delta-like ligand 3-targeted bispecific T-cell engager immunotherapy, for previously treated small cell lung cancer

Tarlatamab is a bispecific T-cell engager immunotherapy targeting delta-like ligand 3 (DLL3) and the cluster of differentiation 3 (CD3) molecule. In the phase 2 DeLLphi-301 trial of tarlatamab for patients with previously treated small cell lung cancer, tarlatamab 10 mg every 2 weeks achieved durable responses and encouraging survival outcomes. Analyses of updated safety data from the DeLLphi-301 trial demonstrated that the most common treatment-emergent adverse events were cytokine release syndrome (53%), pyrexia (38%), decreased appetite (36%), dysgeusia (32%), and an emia (30%). Cytokine release syndrome was mostly grade 1 or 2 in severity, occurred primarily after the first or second tarlatamab dose, and was managed with supportive care, which included the administration of antipyretics (e.g., acetaminophen), intravenous hydration, and/or glucocorticoids. Other treatment-emergent adverse effects of interest included neutropenia (16%) and immune effector cell-associated neurotoxicity syndrome and associated neurologic events (10%). Given that tarlatamab is the first T-cell engager approved for the treatment of small cell lung cancer, raising awareness with regard to the monitoring and management of tarlatamab-associated adverse events is essential. Here, the authors describe the timing, occurrence, and duration of these adverse events and review the management and risk-mitigation strategies used by clinical investigators during the DeLLphi-301 trial.

Expression Patterns of DLL3 across Neuroendocrine and Non-neuroendocrine Neoplasms Reveal Broad Opportunities for Therapeutic Targeting

SIGNIFICANCE

DLL3-targeted therapies have recently shown robust clinical efficacy in aggressive neuroendocrine cancers, positioning them to fulfill a great unmet need in these settings. Here, we examine the clinical and biological correlates of DLL3 expression in both neuroendocrine and non-neuroendocrine cancers. Our findings may stimulate the development and application of DLL3-targeted therapies, as well as other precision therapies, in neuroendocrine cancers and beyond.

Auranofin inhibition of thioredoxin reductase sensitizes lung neuroendocrine tumor cells (NETs) and small cell lung cancer (SCLC) cells to sorafenib as well as inhibiting SCLC xenograft growth

Thioredoxin Reductase (TrxR) functions to recycle thioredoxin (Trx) during hydroperoxide metabolism mediated by peroxiredoxins and is currently being targeted using the FDA-approved anti-rheumatic drug, auranofin (AF), to selectively sensitize cancer cells to therapy. AF treatment decreased TrxR activity and clonogenic survival in small cell lung cancer (SCLC) cell lines (DMS273 and DMS53) as well as the H727 atypical lung carcinoid cell line. AF treatment also significantly sensitized DMS273 and H727 cell lines in vitro to sorafenib, an FDA-approved multi-kinase inhibitor that depleted intracellular glutathione (GSH). The pharmacokinetic, pharmacodynamic, and safety profile of AF was examined in nude mice with DMS273 xenografts administered AF intraperitoneally at 2 mg/kg or 4 mg/kg (IP) once (QD) or twice daily (BID) for 1-5 d. Plasma levels of AF were 10-20 μM (determined by mass spectrometry of gold), and the optimal inhibition of TrxR activity was obtained at 4 mg/kg once daily, with no effect on glutathione peroxidase 1 activity. This AF treatment extended for 14 d, inhibited TrxR (>75%), and resulted in a significant prolongation of median overall survival from 19 to 23 d (p = .04, N = 30 controls, 28 AF). In this experiment, there were no observed changes in animal bodyweight, complete blood counts (CBCs), bone marrow toxicity, blood urea nitrogen, or creatinine. These results support the hypothesis that AF effectively inhibits TrxR both in vitro and in vivo in SCLC, sensitizes NETs and SCLC to sorafenib, and could be repurposed as an adjuvant therapy with targeted agents that induce disruptions in thiol metabolism.

Proteomic profiling reveals the significance of lipid metabolism in small cell lung cancer recurrence and metastasis

BACKGROUND

Small cell lung cancer (SCLC) is a lethal and recalcitrant malignancy with early metastases. However, the molecular and cellular mechanisms underlying its aggressive characteristics remain relatively elusive.

METHODS

In this study, we conducted a comprehensive proteomic analysis of 90 primary tumors, 15 patient-matched lymph node metastatic tumors, and 15 brain metastatic tumors derived from a cohort of 105 SCLC patients. The potential mechanism for SCLC metastasis was investigated based on the variety of protein expression profiles.

RESULTS

Primary tumors were divided into two categories according to the their different protein expression profiles, using metastatic tumors as reference. Proteomic comparisons across different groups revealed that lipid metabolism, especially phospholipid metabolism, and immune response had a critical role in SCLC metastasis. Additionally, it was shown that high- and low-density lipoprotein cholesterol were both independent prognostic factors for disease free survival of SCLC patients. To identify critical regulators of metastasis in SCLC, support vector machine was adopted to generate a biomarker combination of ten proteins, all of which significantly correlated with the infiltration of immune cells. Furthermore, it was demonstrated that high expression of phospholipase A2 group IIA in stroma was associated with delayed disease recurrence in limited stage SCLC.

CONCLUSIONS

This study highlighted the critical significance of lipid metabolism, especially phospholipid metabolism in the disease recurrence and metastasis of SCLC.

Advances in DLL3-targeted therapies for small cell lung cancer: challenges, opportunities, and future directions

Small cell lung cancer (SCLC) remains one of the most aggressive and challenging malignancies to treat, with limited therapeutic options and poor outcomes. Recent advances in understanding SCLC biology have identified Delta-like ligand 3 (DLL3) as a promising target for novel therapies. This review explores the evolving landscape of DLL3-targeted therapies in SCLC, examining their mechanistic basis, preclinical promise, and clinical development. We discuss various therapeutic modalities, including antibody-drug conjugates (ADCs), bispecific T-cell engagers (BiTEs), chimeric antigen receptor T-cell (CAR-T) therapies, and emerging approaches such as near-infrared photoimmunotherapy (NIR-PIT) and radiopharmaceutical therapy (RPT). The review highlights the challenges encountered in translating these promising approaches into clinical practice, including the setbacks faced by early DLL3-targeted therapies like Rovalpituzumab Tesirine (Rova-T). We also explore potential strategies to overcome these obstacles, emphasizing the need for a more nuanced understanding of DLL3 biology and its role in SCLC pathogenesis. The integration of cutting-edge technologies and interdisciplinary collaboration is proposed as a path forward to optimize DLL3-targeted therapies and improve outcomes for SCLC patients. This comprehensive overview provides insights into the current state and future directions of DLL3-targeted therapies, underscoring their potential to revolutionize SCLC treatment paradigms.

ASCL1 Restrains ERK1/2 to Promote Survival of a Subset of Neuroendocrine Lung Cancers

The transcription factor achaete-scute complexhomolog 1 (ASCL1) is a lineage oncogene that is central in growth and survival of the majority of small cell lung cancers and neuroendocrine (NE) non-small cell lung cancers (NSCLC) that express it. Targeting ASCL1, or its downstream pathways, remains a challenge. Small cell lung cancers and NSCLC-NE that express ASCL1 exhibit relatively low ERK1/2 activity, in dramatic contrast to NSCLCs in which the ERK pathway plays a major role in pathogenesis. ERK1/2 inhibition in ASCL1-expressing lung tumor cells revealed downregulation of ERK1/2 pathway suppressors SPRY4, SPRED1, DUSP6, and the transcription factor ETV5, which regulates DUSP6. Chromatin immunoprecipitation sequencing demonstrated that these genes are bound by ASCL1. Availability of a pharmacologic inhibitor directed mechanistic studies toward DUSP6, an ERK1/2-selective phosphatase, in a subset of ASCL1-high NE lung tumors. Inhibition of DUSP6 increased active ERK1/2, which accumulated in the nucleus. Pharmacologic and genetic inhibition of DUSP6 reduced proliferation and survival of these cancers. Resistance developed in DUSP6-knockout cells, indicating a bypass mechanism. Although targeting ASCL1 remains a challenge, our findings suggest that expression of ASCL1, DUSP6, and low phospho-ERK1/2 identifies NE lung cancers for which DUSP6 may be a therapeutic target.

DLL3 as a potential diagnostic and therapeutic target in neuroendocrine neoplasms: A narrative review

Neuroendocrine neoplasms (NENs) represent a diagnostic and therapeutic challenge, due to their heterogeneity and limited treatment options. Conventional imaging techniques and therapeutic strategies may become unreliable during follow-up, due to the tendency of these neoplasms to dedifferentiate over time. Therefore, novel diagnostic and therapeutic options are required for the management of NEN patients. Delta-like ligand 3 (DLL3), an inhibitory ligand of Notch receptor, has emerged as a potential target for novel diagnostic and therapeutic strategies in NENs, since overexpression of DLL3 has been associated with tumor progression, poor prognosis and dedifferentiation in several NENs. This narrative review examines the current evidence about DLL3, its structure, function and association with tumorigenesis in NENs. Ongoing studies exploring the role of DLL3 as an emerging diagnostic marker are reviewed. Promising therapeutic options, such as antibody-conjugated drugs, CAR-T cells and radioimmunoconjugates, are also discussed.

Novel Immunohistochemical Profiling of Small-Cell Lung Cancer: Correlations Between Tumor Subtypes and Immune Microenvironment

BACKGROUND/OBJECTIVES

Small-cell lung cancer (SCLC) is a highly aggressive malignancy with an emerging molecular classification based on the expression of the transcription factors ASCL1, NEUROD1, and POU2F3. This study aimed to explore the relationship between these novel subtypes and the tumor immune microenvironment (TIME), particularly CD8+ and CD4+ tumor-infiltrating lymphocytes (TILs).

METHODS

In 51 cases of patients with SCLC, immunohistochemical (IHC) stains for ASCL1, NEUROD1, POU2F3, CD56, Ki67, CD8, and CD4 were performed. H-scores for the novel transcription factors were calculated to determine tumor subtype. CD8+ and CD4+ TIL counts were averaged across 10 high-power fields. The Kruskal-Wallis test and subsequent post hoc Dunn tests were used to determine the differences in transcription factor expression and TILs across subtypes.

RESULTS

In our cohort, 68.62% of our cases were SCLC-A, 9.80% were SCLC-N, 7.84% were SCLC-P, and 13.72% were SCLC-I. Significant differences were observed in the expression of ASCL1, NEUROD1, and POU2F3 across subtypes. CD8+ TILs were more abundant in SCLC-P and SCLC-I. CD8+ TILs were negatively correlated with ASCL1 expression (p < 0.05) and positively correlated with POU2F3 expression (p < 0.005).

CONCLUSIONS

This study highlights the need to integrate the novel SCLC classification with data regarding the TIME to better inform patient prognosis and treatment.

Characterization of cell states in biliary tract cancers identifies mechanisms of therapeutic resistance in a phase II trial of DKN-01/nivolumab

Biliary tract cancers demonstrate profound therapeutic resistance, and broadly effective therapies for refractory disease are lacking. We conducted a single-arm, second-line phase II trial combining DKN-01, a humanized monoclonal antibody targeting Dickkopf-1 (DKK-1), and nivolumab to treat patients with advanced biliary tract cancer (NCT04057365). No objective responses were seen. To identify mechanisms of treatment failure, we analyzed paired pre-treatment and on-treatment biopsies using scRNA-seq and constructed a detailed molecular classification of malignant and immune cells. We annotated five biliary tract cancer malignant cell states: classical, basal, mesenchymal, neural-like, and endothelial-like. Neural-like and endothelial-like states, which drive therapeutic resistance in other cancers, have not previously been described in BTC. Malignant cell states co-varied with distinct immune cell states, revealing diverse mechanisms of myeloid and T-cell mediated immune suppression, including M2 myeloid and terminally exhausted T cell programs that were induced by DKN-01/nivolumab. Here, we provide the first systematic classification of functionally annotated cell states in biliary tract cancer and provide new insight into resistance mechanisms to an immunotherapy combination that can inform the next generation of trials.

Small cell lung cancer profiling: an updated synthesis of subtypes, vulnerabilities, and plasticity

Small cell lung cancer (SCLC) is a devastating disease with high proliferative and metastatic capacity. SCLC has been classified into molecular subtypes based on differential expression of lineage-defining transcription factors. Recent studies have proposed new subtypes that are based on both tumor-intrinsic and -extrinsic factors. SCLC demonstrates substantial intratumoral subtype heterogeneity characterized by highly plastic transcriptional states, indicating that the initially dominant subtype can shift during disease progression and in association with resistance to therapy. Strategies to promote or constrain plasticity and cell fate transitions have nominated novel targets that could prompt the development of more durably effective therapies for patients with SCLC. In this review, we describe the latest advances in SCLC subtype classification and their biological and clinical implications.

BCL2 expression is enriched in advanced prostate cancer with features of lineage plasticity

The widespread use of potent androgen receptor signaling inhibitors (ARSIs) has led to an increasing emergence of AR-independent castration-resistant prostate cancer (CRPC), typically driven by loss of AR expression, lineage plasticity, and transformation to prostate cancers (PCs) that exhibit phenotypes of neuroendocrine or basal-like cells. The anti-apoptotic protein BCL2 is upregulated in neuroendocrine cancers and may be a therapeutic target for this aggressive PC disease subset. There is an unmet clinical need, therefore, to clinically characterize BCL2 expression in metastatic CRPC (mCRPC), determine its association with AR expression, uncover its mechanisms of regulation, and evaluate BCL2 as a therapeutic target and/or biomarker with clinical utility. Here, using multiple PC biopsy cohorts and models, we demonstrate that BCL2 expression is enriched in AR-negative mCRPC, associating with shorter overall survival and resistance to ARSIs. Moreover, high BCL2 expression associates with lineage plasticity features and neuroendocrine marker positivity. We provide evidence that BCL2 expression is regulated by DNA methylation, associated with epithelial-mesenchymal transition, and increased by the neuronal transcription factor ASCL1. Finally, BCL2 inhibition had antitumor activity in some, but not all, BCL2-positive PC models, highlighting the need for combination strategies to enhance tumor cell apoptosis and enrich response.

Small Cell Lung Cancer Neuronal Features and Their Implications for Tumor Progression, Metastasis, and Therapy

Small cell lung cancer (SCLC) is an epithelial neuroendocrine form of lung cancer for which survival rates remain dismal and new therapeutic approaches are greatly needed. Key biological features of SCLC tumors include fast growth and widespread metastasis, as well as rapid resistance to treatment. Similar to pulmonary neuroendocrine cells, SCLC cells have traits of both hormone-producing cells and neurons. In this study, we specifically discuss the neuronal features of SCLC. We consider how neuronal G protein-coupled receptors and other neuronal molecules on the surface of SCLC cells can contribute to the growth of SCLC tumors and serve as therapeutic targets in SCLC. We also review recent evidence for the role of neuronal programs expressed by SCLC cells in the fast proliferation, migration, and metastasis of these cells. We further highlight how these neuronal programs may be particularly relevant for the development of brain metastases and how they can assist SCLC cells to functionally interact with neurons and astrocytes. A greater understanding of the molecular and cellular neuronal features of SCLC is likely to uncover new vulnerabilities in SCLC cells, which may help develop novel therapeutic approaches. More generally, the epithelial-to-neuronal transition observed during tumor progression in SCLC and other cancer types can contribute significantly to tumor development and response to therapy.

DB-1314, a novel DLL3-targeting ADC with DNA topoisomerase I inhibitor, exhibits promising safety profile and therapeutic efficacy in preclinical small cell lung cancer models

BACKGROUND

Delta-like ligand 3 (DLL3) is highly expressed on the cell surface of small cell lung cancer (SCLC), one of the most lethal malignancies, but minimally or not in normal tissues, making it an attractive target for SCLC. However, none of the DLL3-targeting antibody-drug conjugates (ADCs) have been approved for SCLC therapy yet. We developed DB-1314, the new anti-DLL3 ADC composed of a novel humanized anti-DLL3 monoclonal antibody (DB131401) conjugated with eight molecules of P1021 (topoisomerase I inhibitor), and described its preclinical profiles.

METHODS

The binding epitope for DB131401 and Rovalpituzumab was tested by biolayer interferometry. The binding affinity and specificity of DB-1314 to DLL3 and other homologous proteins were respectively measured by surface plasmon resonance and enzyme-linked immunosorbent assay. Internalization, bystander effects, and antibody-dependent cell-mediated cytotoxicity (ADCC) were assessed by respective assay. DLL3 was quantified by antibodies bound per cell assay and immunohistochemistry. In vitro and in vivo growth inhibition studies were evaluated in SCLC cell lines, and cell line/patient-derived xenograft models. The safety profile was measured in cynomolgus monkeys.

RESULTS

DB-1314 induces potent, durable, and dose-dependent antitumor effects in cells in vitro and in cell/patient-derived xenograft models in vivo. The killing activity of DB-1314 mechanically arises from P1021-induced DNA damage, whereby P1021 is delivered and released within tumor cells through DLL3-specific binding and efficient internalization. Bystander effects and ADCC also contribute to the antitumor activity of DB-1314. DB-1314 displays favorable pharmacokinetic and toxicokinetic profiles in rats and cynomolgus monkeys; besides, DB-1314 is well-tolerated at a dose of up to 60 mg/kg in monkeys.

CONCLUSIONS

These results suggest that DB-1314 may be a candidate ADC targeting DLL3 for the treatment of DLL3-positive SCLC, supporting further evaluation in the clinical setting.

Mammalian SWI/SNF complex activity regulates POU2F3 and constitutes a targetable dependency in small cell lung cancer

Small cell lung cancers (SCLCs) are composed of heterogeneous subtypes marked by lineage-specific transcription factors, including ASCL1, NEUROD1, and POU2F3. POU2F3-positive SCLCs, ∼12% of all cases, are uniquely dependent on POU2F3 itself; as such, approaches to attenuate POU2F3 expression may represent new therapeutic opportunities. Here using genome-scale screens for regulators of POU2F3 expression and SCLC proliferation, we define mSWI/SNF complexes as top dependencies specific to POU2F3-positive SCLC. Notably, chemical disruption of mSWI/SNF ATPase activity attenuates proliferation of all POU2F3-positive SCLCs, while disruption of non-canonical BAF (ncBAF) via BRD9 degradation is effective in pure non-neuroendocrine POU2F3-SCLCs. mSWI/SNF targets to and maintains accessibility over gene loci central to POU2F3-mediated gene regulatory networks. Finally, clinical-grade pharmacologic disruption of SMARCA4/2 ATPases and BRD9 decreases POU2F3-SCLC tumor growth and increases survival in vivo. These results demonstrate mSWI/SNF-mediated governance of the POU2F3 oncogenic program and suggest mSWI/SNF inhibition as a therapeutic strategy for POU2F3-positive SCLCs.

PGC-1α drives small cell neuroendocrine cancer progression towards an ASCL1-expressing subtype with increased mitochondrial capacity

Adenocarcinomas from multiple tissues can evolve into lethal, treatment-resistant small cell neuroendocrine (SCN) cancers comprising multiple subtypes with poorly defined metabolic characteristics. The role of metabolism in directly driving subtype determination remains unclear. Through bioinformatics analyses of thousands of patient tumors, we identified enhanced PGC-1α-a potent regulator of oxidative phosphorylation (OXPHOS)-in various SCN cancers (SCNCs), closely linked with neuroendocrine differentiation. In a patient-derived prostate tissue SCNC transformation system, the ASCL1-expressing neuroendocrine subtype showed elevated PGC-1α expression and increased OXPHOS activity. Inhibition of PGC-1α and OXPHOS reduced the proliferation of SCN lung and prostate cancer cell lines and blocked SCN prostate tumor formation. Conversely, enhancing PGC- 1α and OXPHOS, validated by small-animal Positron Emission Tomography mitochondrial imaging, tripled the SCN prostate tumor formation rate and promoted commitment to the ASCL1 lineage. These results establish PGC-1α as a driver of SCNC progression and subtype determination, highlighting novel metabolic vulnerabilities in SCNCs across different tissues.

STATEMENT OF SIGNIFICANCE

Our study provides functional evidence that metabolic reprogramming can directly impact cancer phenotypes and establishes PGC-1α-induced mitochondrial metabolism as a driver of SCNC progression and lineage determination. These mechanistic insights reveal common metabolic vulnerabilities across SCNCs originating from multiple tissues, opening new avenues for pan-SCN cancer therapeutic strategies.

Notch signaling suppresses neuroendocrine differentiation and alters the immune microenvironment in advanced prostate cancer

Notch signaling can have either an oncogenic or tumor-suppressive function in cancer depending on the cancer type and cellular context. While Notch can be oncogenic in early prostate cancer, we identified significant downregulation of the Notch pathway during prostate cancer progression from adenocarcinoma to neuroendocrine (NE) prostate cancer, where it functions as a tumor suppressor. Activation of Notch in NE and Rb1/Trp53-deficient prostate cancer models led to phenotypic conversion toward a more indolent, non-NE state with glandular features and expression of luminal lineage markers. This was accompanied by upregulation of MHC and type I IFN and immune cell infiltration. Overall, these data support Notch signaling as a suppressor of NE differentiation in advanced prostate cancer and provide insights into how Notch signaling influences lineage plasticity and the tumor microenvironment (TME).

Facts and Hopes on Cancer Immunotherapy for Small Cell Lung Cancer

Platinum-based chemotherapy plus PD1 axis blockade is the standard of care in the first-line treatment of extensive-stage small cell lung cancer (SCLC). Despite the robust and consistent increase in long-term survival with PD1 axis inhibition, the magnitude of the benefit from immunotherapy seems lower than that for other solid tumors. Several immune evasive mechanisms have been shown to be prominently altered in human SCLC, including T-cell exclusion, downregulation of components of the MHC class I antigen processing and presentation machinery, or upregulation of macrophage inhibitory checkpoints, among others. New immunotherapies aiming to target some of these dominant immune suppressive features are being intensively evaluated preclinically and clinically in SCLC. They include strategies to enhance the efficacy and/or reverse features that promote intrinsic resistance to PD1 axis inhibition (e.g., restoring MHC class I deficiency and targeting DNA damage response) and novel immunomodulatory agents beyond T-cell checkpoint blockers (e.g., T cell-redirecting strategies, antibody-drug conjugates, or macrophage checkpoint blockers). Among them, delta-like ligand 3-targeted bispecific T-cell engagers have shown the most compelling preliminary evidence of clinical efficacy and hold promise as therapies that might contribute to further improve patient outcomes in this disease. In this study, we first provide a brief overview of key tumor microenvironment features of human SCLC. Then, we update the current clinical evidence with immune checkpoint blockade and review other emerging immunotherapy strategies that are gaining increasing attention in SCLC. We finally summarize our future perspective on immunotherapy and precision oncology for this disease.

Distinct Regulation of ASCL1 by the Cell Cycle and Chemotherapy in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an aggressive and lethal malignancy. Achaete-scute homolog 1 (ASCL1) is essential for the initiation of SCLC in mice and the development of pulmonary neuroendocrine cells (PNEC), which are the major cells of origin for SCLC. However, the regulatory mechanism of ASCL1 in SCLC remains elusive. Here, we found that ASCL1 expression gradually increases as the tumors grow in a mouse SCLC model, and is regulated by the cell cycle. Mechanistically, CDK2-CyclinA2 complex phosphorylates ASCL1, which results in increased proteasome-mediated ASCL1 protein degradation by E3 ubiquitin ligase HUWE1 during mitosis. TCF3 promotes the multisite phosphorylation of ASCL1 through the CDK2-CyclinA2 complex and the interaction between ASCL1 and TCF3 protects ASCL1 from degradation. The dissociation of TCF3 from ASCL1 during mitosis accelerates the degradation of ASCL1. In addition, chemotherapy drugs greatly reduce the transcription of ASCL1 in SCLC cells. Depletion of ASCL1 sensitizes SCLC cells to chemotherapy drugs. Together, our study demonstrates that ASCL1 is a cell-cycle-regulated protein and provides a theoretical basis for applying cell-cycle-related antitumor drugs in SCLC treatment. Implications:Our study revealed a novel regulatory mechanism of ASCL1 by cell cycle and chemotherapy drugs in SCLC. Treating patients with SCLC with a combination of ASCL1-targeting therapy and chemotherapy drugs could potentially be beneficial.

Oncogenic functions and therapeutic potentials of targeted inhibition of SMARCAL1 in small cell lung cancer

Small cell lung cancer (SCLC) is a recalcitrant cancer characterized by high frequency loss-of-function mutations in tumor suppressors with a lack of targeted therapy due to absence of high frequency gain-of-function abnormalities in oncogenes. SMARCAL1 is a member of the ATP-dependent chromatin remodeling protein SNF2 family that plays critical roles in DNA damage repair and genome stability maintenance. Here, we showed that SMARCAL1 was overexpressed in SCLC patient samples and was inversely associated with overall survival of the patients. SMARCAL1 was required for SCLC cell proliferation and genome integrity. Mass spectrometry revealed that PAR6B was a downstream SMARCAL1 signal molecule which rescued inhibitory effects caused by silencing of SMARCAL1. By screening of 36 FDA-approved clinically available agents related to DNA damage repair, we found that an aza-anthracenedione, pixantrone, was a potent SMARCAL1 inhibitor which suppressed the expression of SMARCAL1 and PAR6B at protein level. Pixantrone caused DNA damage and exhibited inhibitory effects on SCLC cells in vitro and in a patient-derived xenograft mouse model. These results indicated that SMARCAL1 functions as an oncogene in SCLC, and pixantrone as a SMARCAL1 inhibitor bears therapeutic potentials in this deadly disease.

Co-targeting BET, CBP, and p300 inhibits neuroendocrine signalling in androgen receptor-null prostate cancer

There are diverse phenotypes of castration-resistant prostate cancer, including neuroendocrine disease, that vary in their sensitivity to drug treatment. The efficacy of BET and CBP/p300 inhibitors in prostate cancer is attributed, at least in part, to their ability to decrease androgen receptor (AR) signalling. However, the activity of BET and CBP/p300 inhibitors in prostate cancers that lack the AR is unclear. In this study, we showed that BRD4, CBP, and p300 were co-expressed in AR-positive and AR-null prostate cancer. A combined inhibitor of these three proteins, NEO2734, reduced the growth of both AR-positive and AR-null organoids, as measured by changes in viability, size, and composition. NEO2734 treatment caused consistent transcriptional downregulation of cell cycle pathways. In neuroendocrine models, NEO2734 treatment reduced ASCL1 levels and other neuroendocrine markers, and reduced tumour growth in vivo. Collectively, these results show that epigenome-targeted inhibitors cause decreased growth and phenotype-dependent disruption of lineage regulators in neuroendocrine prostate cancer, warranting further development of compounds with this activity in the clinic. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Cuproptosis-related gene LIPT1 as a prognostic indicator in non-small cell lung cancer: Functional involvement and regulation of ATOX1 expression

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related deaths, necessitating a deeper understanding of novel cell death pathways like cuproptosis. This study explored the relevance of cuproptosis-related genes in NSCLC and their potential prognostic significance. We analyzed the expression of 16 cuproptosis-related genes in 1017 NSCLC tumors and 578 Genotype-Tissue Expression (GTEx) normal samples from The Cancer Genome Atlas (TCGA) to identify significant genes. A risk model and prognostic nomogram were employed to identify the pivotal prognostic gene. Further in vitro experiments were conducted to investigate the functions of the identified genes in NSCLC cell lines. LIPT1, a gene for lipoate-protein ligase 1 enzyme, emerged as the central prognostic gene with decreased expression in NSCLC. Importantly, elevated LIPT1 levels were associated with a favorable prognosis for NSCLC patients. Overexpression of LIPT1 inhibited cell growth and enhanced apoptosis in NSCLC. We confirmed that LIPT1 downregulates the copper chaperone gene antioxidant 1 (ATOX1), thereby impeding NSCLC progression. Our study identified LIPT1 as a valuable prognostic biomarker in NSCLC as it elucidates its tumor-inhibitory role through the modulation of ATOX1. These findings offered insights into the potential therapeutic targeting of LIPT1 in NSCLC, contributing to a deeper understanding of this deadly disease.

Molecular pathology of small cell lung cancer: Overview from studies on neuroendocrine differentiation regulated by ASCL1 and Notch signaling

Pulmonary neuroendocrine (NE) cells are rare airway epithelial cells. The balance between Achaete-scute complex homolog 1 (ASCL1) and hairy and enhancer of split 1, one of the target molecules of the Notch signaling pathway, is crucial for NE differentiation. Small cell lung cancer (SCLC) is a highly aggressive lung tumor, characterized by rapid cell proliferation, a high metastatic potential, and the acquisition of resistance to treatment. The subtypes of SCLC are defined by the expression status of NE cell-lineage transcription factors, such as ASCL1, which roles are supported by SRY-box 2, insulinoma-associated protein 1, NK2 homeobox 1, and wingless-related integration site signaling. This network reinforces NE differentiation and may induce the characteristic morphology and chemosensitivity of SCLC. Notch signaling mediates cell-fate decisions, resulting in an NE to non-NE fate switch. The suppression of NE differentiation may change the histological type of SCLC to a non-SCLC morphology. In SCLC with NE differentiation, Notch signaling is typically inactive and genetically or epigenetically regulated. However, Notch signaling may be activated after chemotherapy, and, in concert with Yes-associated protein signaling and RE1-silencing transcription factor, suppresses NE differentiation, producing intratumor heterogeneity and chemoresistance. Accumulated information on the molecular mechanisms of SCLC will contribute to further advances in the control of this recalcitrant cancer.

Patient-derived tumoroid models of pulmonary large-cell neuroendocrine carcinoma: a promising tool for personalized medicine and developing novel therapeutic strategies

Pulmonary large-cell neuroendocrine carcinoma (LCNEC), a disease with poor prognosis, is classified as pulmonary high-grade neuroendocrine carcinoma, along with small-cell lung cancer. However, given its infrequent occurrence, only a limited number of preclinical models have been established. Here, we established three LCNEC tumoroids for long-term culture. Whole-exome sequencing revealed that these tumoroids inherited genetic mutations from their parental tumors; two were classified as small-cell carcinoma (S-LCNEC) and one as non-small cell carcinoma (N-LCNEC). Xenografts from these tumoroids in immunodeficient mice mimicked the pathology of the parent LCNEC, and one reproduced the mixed-tissue types of combined LCNEC with a component of adenocarcinoma. Drug sensitivity tests using these LCNEC tumoroids enabled the evaluation of therapeutic agent efficacy. Based on translational research, we found that a CDK4/6 inhibitor might be effective for N-LCNEC and that Aurora A kinase inhibitors might be suitable for S-LCNEC or LCNEC with MYC amplification. These results highlight the value of preclinical tumoroid models in understanding the pathogenesis of rare cancers and developing treatments. LCNEC showed a high success rate in tumoroid establishment, indicating its potential application in personalized medicine.

ASCL1 Drives Tolerance to Osimertinib in EGFR Mutant Lung Cancer in Permissive Cellular Contexts

The majority of EGFR mutant lung adenocarcinomas respond well to EGFR tyrosine kinase inhibitors (TKI). However, most of these responses are partial, with drug-tolerant residual disease remaining even at the time of maximal response. This residual disease can ultimately lead to relapses, which eventually develop in most patients. To investigate the cellular and molecular properties of residual tumor cells in vivo, we leveraged patient-derived xenograft (PDX) models of EGFR mutant lung cancer. Subcutaneous EGFR mutant PDXs were treated with the third-generation TKI osimertinib until maximal tumor regression. Residual tissue inevitably harbored tumor cells that were transcriptionally distinct from bulk pretreatment tumor. Single-cell transcriptional profiling provided evidence of cells matching the profiles of drug-tolerant cells present in the pretreatment tumor. In one of the PDXs analyzed, osimertinib treatment caused dramatic transcriptomic changes that featured upregulation of the neuroendocrine lineage transcription factor ASCL1. Mechanistically, ASCL1 conferred drug tolerance by initiating an epithelial-to-mesenchymal gene-expression program in permissive cellular contexts. This study reveals fundamental insights into the biology of drug tolerance, the plasticity of cells through TKI treatment, and why specific phenotypes are observed only in certain tumors.

SIGNIFICANCE

Analysis of residual disease following tyrosine kinase inhibitor treatment identified heterogeneous and context-specific mechanisms of drug tolerance in lung cancer that could lead to the development of strategies to forestall drug resistance. See related commentary by Rumde and Burns, p. 1188.

Multifaced roles of the long non-coding RNA DRAIC in cancer progression

Long non-coding RNAs (lncRNA) are functional RNAs, with over 200 nucleotides in length and lacking protein-coding potential. Studies have indicated that lncRNAs are important gene regulators under physiological conditions. Aberrant lncRNA expression is associated with the initiation and progression of various diseases, including cancers. High-throughput transcriptome analyses have revealed thousands of lncRNAs as putative tumor suppressors or promoters in various cancers, but the detailed molecular mechanisms of each lncRNA remain unclear. Downregulated RNA In Cancer, inhibitor of cell invasion and migration (DRAIC) (also known as LOC145837 and RP11-279F6.1) is a lncRNA that inhibits or promotes cancer progression with several modes of action. DRAIC was originally identified as a tumor-suppressive lncRNA in prostate adenocarcinoma. Subsequent studies also revealed that it has an anti-tumor role in glioblastoma, triple-negative breast cancer, and stomach adenocarcinoma. However, DRAIC exhibits oncogenic functions in other malignancies, such as lung adenocarcinoma and esophageal carcinoma, indicating its highly context-dependent effects on cancer progression and clinical outcomes. DRAIC and its associated pathways regulate various biological processes, including proliferation, invasion, metastasis, autophagy, and neuroendocrine function. This review introduces the multifaceted roles of DRAIC, particularly in cancer progression, and discusses its biological significance and clinical implications.

PROTAC-Mediated Dual Degradation of BCL-xL and BCL-2 Is a Highly Effective Therapeutic Strategy in Small-Cell Lung Cancer

BCL-xL and BCL-2 are validated therapeutic targets in small-cell lung cancer (SCLC). Targeting these proteins with navitoclax (formerly ABT263, a dual BCL-xL/2 inhibitor) induces dose-limiting thrombocytopenia through on-target BCL-xL inhibition in platelets. Therefore, platelet toxicity poses a barrier in advancing the clinical translation of navitoclax. We have developed a strategy to selectively target BCL-xL in tumors, while sparing platelets, by utilizing proteolysis-targeting chimeras (PROTACs) that hijack the cellular ubiquitin proteasome system for target ubiquitination and subsequent degradation. In our previous study, the first-in-class BCL-xL PROTAC, called DT2216, was shown to have synergistic antitumor activities when combined with venetoclax (formerly ABT199, BCL-2-selective inhibitor) in a BCL-xL/2 co-dependent SCLC cell line, NCI-H146 (hereafter referred to as H146), in vitro and in a xenograft model. Guided by these findings, we evaluated our newly developed BCL-xL/2 dual degrader, called 753b, in three BCL-xL/2 co-dependent SCLC cell lines and the H146 xenograft models. 753b was found to degrade both BCL-xL and BCL-2 in these cell lines. Importantly, it was considerably more potent than DT2216, navitoclax, or DT2216 + venetoclax in reducing the viability of BCL-xL/2 co-dependent SCLC cell lines in cell culture. In vivo, 5 mg/kg weekly dosing of 753b was found to lead to significant tumor growth delay, similar to the DT2216 + venetoclax combination in H146 xenografts, by degrading both BCL-xL and BCL-2. Additionally, 753b administration at 5 mg/kg every four days induced tumor regressions. At this dosage, 753b was well tolerated in mice, without observable induction of severe thrombocytopenia as seen with navitoclax, and no evidence of significant changes in mouse body weights. These results suggest that the BCL-xL/2 dual degrader could be an effective and safe therapeutic for a subset of SCLC patients, warranting clinical trials in future.

Treatment-related Neuroendocrine Prostate Carcinoma-Diagnostic and Molecular Correlates

Treatment-related neuroendocrine prostate cancer is a distinctive category of prostate cancer that arises after intensive suppression of the androgen receptor by next-generation therapeutic inhibition of androgen receptor signaling. The biological processes that set in motion the series of events resulting in transformation of adenocarcinoma to neuroendocrine carcinoma include genomic (loss of tumor suppressors TP53 and RB1, amplification of oncogenes N-MYC and Aurora Kinase A, dysregulation of transcription factors SOX2, achaete-scute-homolog 1, and others) as well as epigenomic (DNA methylation, EZH2 overexpression, and others). Pathologic diagnosis is key to effective therapy for this disease, and this is aided by localizing metastatic lesions for biopsy using radioligand imaging in the appropriate clinical context. As our understanding of biology evolves, there has been increased morphologic recognition and characterization of tumor phenotypes that are present in this advanced post-treatment setting. New and promising biomarkers (delta-like ligand 3 and others) have been discovered, which opens up novel therapeutic avenues including immunotherapy and antibody-drug conjugates for this lethal disease with currently limited treatment options.

Small cells - big issues: biological implications and preclinical advancements in small cell lung cancer

Current treatment guidelines refer to small cell lung cancer (SCLC), one of the deadliest human malignancies, as a homogeneous disease. Accordingly, SCLC therapy comprises chemoradiation with or without immunotherapy. Meanwhile, recent studies have made significant advances in subclassifying SCLC based on the elevated expression of the transcription factors ASCL1, NEUROD1, and POU2F3, as well as on certain inflammatory characteristics. The role of the transcription regulator YAP1 in defining a unique SCLC subset remains to be established. Although preclinical analyses have described numerous subtype-specific characteristics and vulnerabilities, the so far non-existing clinical subtype distinction may be a contributor to negative clinical trial outcomes. This comprehensive review aims to provide a framework for the development of novel personalized therapeutic approaches by compiling the most recent discoveries achieved by preclinical SCLC research. We highlight the challenges faced due to limited access to patient material as well as the advances accomplished by implementing state-of-the-art models and methodologies.

Functional Characterisation of the ATOH1 Molecular Subtype Indicates a Pro-Metastatic Role in Small Cell Lung Cancer

Molecular subtypes of Small Cell Lung Cancer (SCLC) have been described based on differential expression of transcription factors (TFs) ASCL1, NEUROD1, POU2F3 and immune-related genes. We previously reported an additional subtype based on expression of the neurogenic TF ATOH1 within our SCLC Circulating tumour cell-Derived eXplant (CDX) model biobank. Here we show that ATOH1 protein was detected in 7/81 preclinical models and 16/102 clinical samples of SCLC. In CDX models, ATOH1 directly regulated neurogenesis and differentiation programs consistent with roles in normal tissues. In ex vivo cultures of ATOH1-positive CDX, ATOH1 was required for cell survival. In vivo, ATOH1 depletion slowed tumour growth and suppressed liver metastasis. Our data validate ATOH1 as a bona fide oncogenic driver of SCLC with tumour cell survival and pro-metastatic functions. Further investigation to explore ATOH1 driven vulnerabilities for targeted treatment with predictive biomarkers is warranted.

Neuroendocrine and squamous cell phenotypes of NUT carcinoma are potential diagnostic pitfalls that discriminating it from mimickers, such as small cell and squamous cell carcinoma

INTRODUCTION

NUT carcinoma is a rare cancer associated with a poor prognosis. Because of its rarity, its diagnosis is challenging and is usually made by excluding other diagnoses. Immunohistochemical analysis is a reliable technique that contributes to a correct diagnosis, but overestimating the expression of neuroendocrine (NE) markers may result in an incorrect diagnosis. In this study, we established the immunohistochemical phenotypes of NUT carcinoma compared with tumors that mimic its phenotype to identify potential diagnostic pitfalls.

METHODS

Eight cases of NUT carcinoma were examined along with eight basaloid squamous cell carcinomas and thirteen cases of small cell carcinoma using an immunohistochemical panel consisting of various antibodies.

RESULTS

Of the eight NUT carcinomas, three patients had a smoking history. All the cases examined for INSM1 were positive (6/6, 100%), although the staining was somewhat weak. Among the NE markers, synaptophysin was variably positive in two NUT carcinomas (2/6, 33%); however, all cases were negative for ASCL1, chromogranin A, and CD56. Moreover, the squamous cell markers, p40 and CK5/6, were weakly expressed in 4/6 (67%) and 3/6 (50%) of the NUT carcinomas, respectively.

CONCLUSIONS

For tumors with an ambiguous morphology, applying the neuroendocrine phenotype of NUT carcinoma may be misleading; particularly, when distinguishing it from small-cell carcinoma. Similarly, null or weak expression of squamous cell markers may be observed in NUT carcinoma, but this differs from squamous cell carcinoma, which consistently demonstrates strong positivity for squamous cell markers.

Top IHC/ISH Hacks for and Molecular Surrogates of Poorly Differentiated Sinonasal Small Round Cell Tumors

BACKGROUND

Poorly differentiated sinonasal small round cell tumors (SRCTs) are rare and heterogeneous, posing challenges in diagnosis and treatment.

METHODS

Recent advances in molecular findings and diagnostic refinement have promoted better understanding and management of these tumors.

RESULTS

The newly defined and emerging sinonasal entities demonstrate diverse morphologies, specific genomic signatures, and clinical behavior from conventional counterparts. In this review of SRCTs, emphasis is placed on the diagnostic approach with the employment of a pertinent panel of immunohistochemistry studies and/or molecular tests, fine-tuned to the latest WHO 5 classification of sinonasal/paranasal tumors and personalized treatment.

CONCLUSION

Specifically, this review focuses on tumors with epithelial and neuroectodermal derivation.

Mammalian SWI/SNF complex activity regulates POU2F3 and constitutes a targetable dependency in small cell lung cancer

Small cell lung cancers (SCLC) are comprised of heterogeneous subtypes marked by lineage-specific transcription factors, including ASCL1, NEUROD1, and POU2F3. POU2F3-positive SCLC, ∼12% of all cases, are uniquely dependent on POU2F3 itself; as such, approaches to attenuate POU2F3 expression may represent new therapeutic opportunities. Here using genome-scale screens for regulators of POU2F3 expression and SCLC proliferation, we define mSWI/SNF complexes, including non-canonical BAF (ncBAF) complexes, as top dependencies specific to POU2F3-positive SCLC. Notably, clinical-grade pharmacologic mSWI/SNF inhibition attenuates proliferation of all POU2F3-positive SCLCs, while disruption of ncBAF via BRD9 degradation is uniquely effective in pure non-neuroendocrine POU2F3-SCLCs. mSWI/SNF maintains accessibility over gene loci central to POU2F3-mediated gene regulatory networks. Finally, chemical targeting of SMARCA4/2 mSWI/SNF ATPases and BRD9 decrease POU2F3-SCLC tumor growth and increase survival in vivo . Taken together, these results characterize mSWI/SNF-mediated global governance of the POU2F3 oncogenic program and suggest mSWI/SNF inhibition as a therapeutic strategy for SCLC.

Molecular classification of small cell lung cancer subtypes: Characteristics, prognostic factors, and clinical translation

ABSTRACT

Small cell lung cancer (SCLC) is a highly malignant tumor with a very poor prognosis; therefore, more effective treatments are urgently needed for patients afflicted with the disease. In recent years, emerging molecular classifications based on key transcription factors of SCLC have provided more information on the tumor pathophysiology, metastasis, immune microenvironment, and acquired therapeutic resistance and reflected the intertumoral heterogeneity of the various SCLC phenotypes. Additionally, advances in genomics and single-cell sequencing analysis have further revealed the high intratumoral heterogeneity and plasticity of the disease. Herein, we review and summarize these recent lines of evidence and discuss the possible pathogenesis of SCLC.

Induced degradation of lineage-specific oncoproteins drives the therapeutic vulnerability of small cell lung cancer to PARP inhibitors

Although BRCA1/2 mutations are not commonly found in small cell lung cancer (SCLC), a substantial fraction of SCLC shows clinically relevant response to PARP inhibitors (PARPis). However, the underlying mechanism(s) of PARPi sensitivity in SCLC is poorly understood. We performed quantitative proteomic analyses and identified proteomic changes that signify PARPi responses in SCLC cells. We found that the vulnerability of SCLC to PARPi could be explained by the degradation of lineage-specific oncoproteins (e.g., ASCL1). PARPi-induced activation of the E3 ligase HUWE1 mediated the ubiquitin-proteasome system (UPS)-dependent ASCL1 degradation. Although PARPi induced a general DNA damage response in SCLC cells, this signal generated a cell-specific response in ASCL1 degradation, leading to the identification of HUWE1 expression as a predictive biomarker for PARPi. Combining PARPi with agents targeting these pathways markedly improved therapeutic response in SCLC. The degradation of lineage-specific oncoproteins therefore represents a previously unidentified mechanism for PARPi efficacy in SCLC.

Distinct microRNA Signature and Suppression of ZFP36L1 Define ASCL1-Positive Lung Adenocarcinoma

Achaete-scute family bHLH transcription factor 1 (ASCL1) is a master transcription factor involved in neuroendocrine differentiation. ASCL1 is expressed in approximately 10% of lung adenocarcinomas (LUAD) and exerts tumor-promoting effects. Here, we explored miRNA profiles in ASCL1-positive LUADs and identified several miRNAs closely associated with ASCL1 expression, including miR-375, miR-95-3p/miR-95-5p, miR-124-3p, and members of the miR-17∼92 family. Similar to small cell lung cancer, Yes1 associated transcriptional regulator (YAP1), a representative miR-375 target gene, was suppressed in ASCL1-positive LUADs. ASCL1 knockdown followed by miRNA profiling in a cell culture model further revealed that ASCL1 positively regulates miR-124-3p and members of the miR-17∼92 family. Integrative transcriptomic analyses identified ZFP36 ring finger protein like 1 (ZFP36L1) as a target gene of miR-124-3p, and IHC studies demonstrated that ASCL1-positive LUADs are associated with low ZFP36L1 protein levels. Cell culture studies showed that ectopic ZFP36L1 expression inhibits cell proliferation, survival, and cell-cycle progression. Moreover, ZFP36L1 negatively regulated several genes including E2F transcription factor 1 (E2F1) and snail family transcriptional repressor 1 (SNAI1). In conclusion, our study revealed that suppression of ZFP36L1 via ASCL1-regulated miR-124-3p could modulate gene expression, providing evidence that ASCL1-mediated regulation of miRNAs shapes molecular features of ASCL1-positive LUADs.

IMPLICATIONS

Our study revealed unique miRNA profiles of ASCL1-positive LUADs and identified ASCL1-regulated miRNAs with functional relevance.

Advances in new targets for immunotherapy of small cell lung cancer

Small cell lung cancer (SCLC) is one of the highly aggressive malignancies characterized by rapid growth and early metastasis, but treatment options are limited. For SCLC, carboplatin or cisplatin in combination with etoposide chemotherapy has been considered the only standard of care, but the standard first-line treatment only results in 10-month survival. The majority of patients relapse within a few weeks to months after treatment, despite the relatively sensitive response to chemotherapy. Over the past decade, immunotherapy has made significant progress in the treatment of SCLC patients. However, there have been limited improvements in survival rates for SCLC patients with the current immune checkpoint inhibitors PD-1/PD-L1 and CTLA-4. In the face of high recurrence rates, small beneficiary populations, and low survival benefits, the exploration of new targets for key molecules and signals in SCLC and the development of drugs with novel mechanisms may provide fresh hope for immunotherapy in SCLC. Therefore, the aim of this review was to explore four new targets, DLL3, TIGIT, LAG-3, and GD2, which may play a role in the immunotherapy of SCLC to find useful clues and strategies to improve the outcome for SCLC patients.

Actionable Driver Events in Small Cell Lung Cancer

Small cell lung cancer (SCLC) stands out as the most aggressive form of lung cancer, characterized by an extremely high proliferation rate and a very poor prognosis, with a 5-year survival rate that falls below 7%. Approximately two-thirds of patients receive their diagnosis when the disease has already reached a metastatic or extensive stage, leaving chemotherapy as the remaining first-line treatment option. Other than the recent advances in immunotherapy, which have shown moderate results, SCLC patients cannot yet benefit from any approved targeted therapy, meaning that this cancer remains treated as a uniform entity, disregarding intra- or inter-tumoral heterogeneity. Continuous efforts and technological improvements have enabled the identification of new potential targets that could be used to implement novel therapeutic strategies. In this review, we provide an overview of the most recent approaches for SCLC treatment, providing an extensive compilation of the targeted therapies that are currently under clinical evaluation and inhibitor molecules with promising results in vitro and in vivo.

Tumor microenvironment-mediated immune profiles and efficacy of anti-PD-L1 antibody plus chemotherapy stratified by DLL3 expression in small-cell lung cancer

BACKGROUND

Delta-like ligand 3 (DLL3) is a therapeutic target in small-cell lung cancer (SCLC). However, how DLL3 expression status affects the tumor microenvironment (TME) and clinical outcomes in SCLC remains unclear.

METHODS

This retrospective study included patients with postoperative limited-stage (LS)-SCLC and extensive-stage (ES)-SCLC treated with platinum and etoposide (PE) plus anti-programmed cell death ligand 1 (PD-L1) antibody. We investigated the relationship of DLL3 expression with TME, mutation status, tumor neoantigens, and immunochemotherapy.

RESULTS

In the LS-SCLC cohort (n = 59), whole-exome sequencing revealed that DLL3High cases had significantly more neoantigens (P = 0.004) and a significantly higher rate of the signature SBS4 associated with smoking (P = 0.02) than DLL3Low cases. Transcriptome analysis in the LS-SCLC cohort revealed that DLL3High cases had significantly suppressed immune-related pathways and dendritic cell (DC) function. SCLC with DLL3High had significantly lower proportions of T cells, macrophages, and DCs than those with DLL3Low. In the ES-SCLC cohort (n = 30), the progression-free survival associated with PE plus anti-PD-L1 antibody was significantly worse in DLL3High cases than in DLL3Low cases (4.7 vs. 7.4 months, P = 0.01).

CONCLUSIONS

Although SCLC with DLL3High had a higher neoantigen load, these tumors were resistant to immunochemotherapy due to suppressed tumor immunity by inhibiting antigen-presenting functions.

Clinical insights into small cell lung cancer: Tumor heterogeneity, diagnosis, therapy, and future directions

Small cell lung cancer (SCLC) is characterized by rapid growth and high metastatic capacity. It has strong epidemiologic and biologic links to tobacco carcinogens. Although the majority of SCLCs exhibit neuroendocrine features, an important subset of tumors lacks these properties. Genomic profiling of SCLC reveals genetic instability, almost universal inactivation of the tumor suppressor genes TP53 and RB1, and a high mutation burden. Because of early metastasis, only a small fraction of patients are amenable to curative-intent lung resection, and these individuals require adjuvant platinum-etoposide chemotherapy. Therefore, the vast majority of patients are currently being treated with chemoradiation with or without immunotherapy. In patients with disease confined to the chest, standard therapy includes thoracic radiotherapy and concurrent platinum-etoposide chemotherapy. Patients with metastatic (extensive-stage) disease are treated with a combination of platinum-etoposide chemotherapy plus immunotherapy with an anti-programmed death-ligand 1 monoclonal antibody. Although SCLC is initially very responsive to platinum-based chemotherapy, these responses are transient because of the development of drug resistance. In recent years, the authors have witnessed an accelerating pace of biologic insights into the disease, leading to the redefinition of the SCLC classification scheme. This emerging knowledge of SCLC molecular subtypes has the potential to define unique therapeutic vulnerabilities. Synthesizing these new discoveries with the current knowledge of SCLC biology and clinical management may lead to unprecedented advances in SCLC patient care. Here, the authors present an overview of multimodal clinical approaches in SCLC, with a special focus on illuminating how recent advancements in SCLC research could accelerate clinical development.

Delta-like ligand 3 in small cell lung cancer: Potential mechanism and treatment progress

Small cell lung cancer (SCLC) is one of a pathological type of lung cancer, and it is characterized by invasiveness, high malignancy and refractoriness. The mortality rate of SCLC is significantly higher than other types of lung cancer, and the treatment options for SCLC patients are limited. Delta-like ligand 3 (DLL3) is a Notch signaling ligand that plays a role in regulating the proliferation, development and metastasis of SCLC cells. Mnay studies have shown that DLL3 is overexpressed on the surface of SCLC cells, suggesting that DLL3 is a potential target for SCLC patients. A series of drug trials targeting DLL3 are underway. The Phase III clinical trials of Rova-T, a drug targeting DLL3, have not yielded the expected results. However, other drugs that target DLL3, such as AMG119, AMG757 and DLL3-targeted NIR-PIT, bring new ideas for SCLC treatment. Overall, DLL3 remains a valuable target for SCLC.

Data-driven structural analysis of small cell lung cancer transcription factor network suggests potential subtype regulators and transition pathways

Small cell lung cancer (SCLC) is an aggressive disease and challenging to treat due to its mixture of transcriptional subtypes and subtype transitions. Transcription factor (TF) networks have been the focus of studies to identify SCLC subtype regulators via systems approaches. Yet, their structures, which can provide clues on subtype drivers and transitions, are barely investigated. Here, we analyze the structure of an SCLC TF network by using graph theory concepts and identify its structurally important components responsible for complex signal processing, called hubs. We show that the hubs of the network are regulators of different SCLC subtypes by analyzing first the unbiased network structure and then integrating RNA-seq data as weights assigned to each interaction. Data-driven analysis emphasizes MYC as a hub, consistent with recent reports. Furthermore, we hypothesize that the pathways connecting functionally distinct hubs may control subtype transitions and test this hypothesis via network simulations on a candidate pathway and observe subtype transition. Overall, structural analyses of complex networks can identify their functionally important components and pathways driving the network dynamics. Such analyses can be an initial step for generating hypotheses and can guide the discovery of target pathways whose perturbation may change the network dynamics phenotypically.

A plasma miRNA-based classifier for small cell lung cancer diagnosis

Introduction

Small cell lung cancer (SCLC) is characterized by poor prognosis and challenging diagnosis. Screening in high-risk smokers results in a reduction in lung cancer mortality, however, screening efforts are primarily focused on non-small cell lung cancer (NSCLC). SCLC diagnosis and surveillance remain significant challenges. The aberrant expression of circulating microRNAs (miRNAs/miRs) is reported in many tumors and can provide insights into the pathogenesis of tumor development and progression. Here, we conducted a comprehensive assessment of circulating miRNAs in SCLC with a goal of developing a miRNA-based classifier to assist in SCLC diagnoses.

Methods

We profiled deregulated circulating cell-free miRNAs in the plasma of SCLC patients. We tested selected miRNAs on a training cohort and created a classifier by integrating miRNA expression and patients' clinical data. Finally, we applied the classifier on a validation dataset.

Results

We determined that miR-375-3p can discriminate between SCLC and NSCLC patients, and between SCLC and Squamous Cell Carcinoma patients. Moreover, we found that a model comprising miR-375-3p, miR-320b, and miR-144-3p can be integrated with race and age to distinguish metastatic SCLC from a control group.

Discussion

This study proposes a miRNA-based biomarker classifier for SCLC that considers clinical demographics with specific cut offs to inform SCLC diagnosis.