Small Cell Lung Cancer Tumors Research Articles

Platinum-Based Chemotherapy ‘Rechallenge’ in Advanced Non-ovarian Solid Malignancies

Platinum-based chemotherapy forms the backbone of treatment for many solid cancers. However, resistance inevitably develops in those with advanced disease. Platinum rechallenge is a well-established concept in the management of ovarian cancer, small cell lung cancer and germ cell tumours. In other solid malignancies there is a lack of quality evidence to support platinum rechallenge, yet it is a widely adopted strategy. Often, patients are within the last year of life, making questions of efficacy, treatment-related toxicity and quality of life critical factors for treatment recommendations. In this overview we appraise the available evidence for platinum rechallenge and strategies being developed to attempt resensitisation of tumours to platinum-based chemotherapy.

Precision Medicine in Inflammatory Bowel Diseases: Challenges and Considerations for the Path Forward

Precision Medicine in Inflammatory Bowel Diseases: Challenges and Considerations for the Path Forward

Killing SCLC: insights into how to target a shapeshifting tumor.

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.

Therapeutic targeting of BAP1/ASXL3 sub-complex in ASCL1-dependent small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive disease, with patients diagnosed with either early-stage, limited stage, or extensive stage of SCLC tumor progression. Discovering and targeting the functional biomarkers for SCLC will be crucial in understanding the molecular basis underlying SCLC tumorigenesis to better assist in improving clinical treatment. Emerging studies have demonstrated that dysregulations in BAP1 histone H2A deubiquitinase complex are collectively associated with pathogenesis in human SCLC. Here, we investigated the function of the oncogenic BAP1/ASXL3/BRD4 epigenetic axis in SCLC by developing a next-generation BAP1 inhibitor, iBAP-II, and focusing on the epigenetic balance established between BAP1 and non-canonical PRC1 complexes in regulating SCLC-specific transcriptional programming. We further demonstrated that pharmacologic inhibition of BAP1’s catalytic activity disrupted BAP1/ASXL3/BRD4 epigenetic axis by inducing protein degradation of the ASXL3 scaffold protein, which bridges BRD4 and BAP1 at active enhancers. Furthermore, treatment of iBAP-II represses neuroendocrine lineage-specific ASCL1/MYCL/E2F signaling in SCLC cell lines, and dramatically inhibits SCLC cell viability and tumor growth in vivo. In summary, this study has provided mechanistic insight into the oncogenic function of BAP1 in SCLC and highlighted the potential of targeting BAP1’s activity as a novel SCLC therapy.

The Change of Soluble Programmed Death Ligand 1 (sPD-L1) in Plasma of Small Cell Lung Cancer and Its Clinical Significance.

Background soluble programmed death-ligand 1 (sPD-L1) expression in lung squamous cell carcinoma and lung adenocarcinoma is associated with disease progression, and sPD-L1 expression in small cell lung cancer (SCLC) may have similar manifestations and become a potential marker for treatment. The purpose of this study was to observe the changes of plasma sPD-L1 expression in SCLC patients. Methods. 90 patients diagnosed with SCLC from January 2019 to November 2020 were selected as the test group, including 72 males and 18 women, 58.7 ± 6.6 years; 30 healthy subjects were selected from the physical examination center, including 18 males, 12 females, and 60.3 ± 7.0 years. There were no statistical difference in sex and age factors between the trial and control groups (p > 0.05). Selected SCLC used chemotherapy regimen: cisplatin + etoposide (EP), carboplatin + etoposide (CE), and SCLC group were divided into three subgroups of disease progression group, partial remission group, and disease stability group according to the treatment effect. Comparison of the differences in sPD-L1 expression content between the experimental and control populations. Plasma sPD-L1 levels were dynamically monitored pre- and posttreatment in 90 patients with small-cell lung cancer and were associated with efficacy among subgroups. Meanwhile, the risk factors for patient sPD-L1 expression content were analyzed by logistic regression. Results. Plasma sPD-L1 levels were higher in the SCLC group than in the healthy people group (t = 7.40, p < 0.01). In the disease progression group of the SCLC group, sPD-L1 levels were decreased in the SCLC group, sPD-L1 in some remission group was increased after treatment, and sPD-L1 levels in the disease-stable group (p > 0.05). Multivariate logistic regression analysis showed that factors promoting increased sPD-L1 expression in SCLC patients included increased smoking, brain metastasis, and ProGRP expression (both p values < 0.05). Conclusion. (1) Higher peripheral sPD-L1 expression in SCLC patients than in healthy patients, and the expression levels were closely related to efficacy. (2) Dynamic changes in s PD-L1 were correlated with clinical efficacy. (3) The progression of sPD-L1 and ProGRP in SCLC patients showed the same extent during remission and stabilization, suggesting the effect of s PD-L1 in the evaluation of SCLC tumors and the reflection of the tumor marker ProGRP.

Infiltrating T lymphocytes in the tumor microenvironment of small cell lung cancer: a state of knowledge review.

Immune checkpoint inhibitors (ICIs) have brought new hope for the treatment of patients with small cell lung cancer (SCLC) over the past decades. However, the overall response rate is limited, and is lower than that in non-small cell lung cancer (NSCLC). This is in part because of the lack of pre-existing tumor-infiltrating T lymphocytes (TITLs), especially cytotoxic T cells (CTLs), in the SCLC tumor microenvironment (TME), resulting in insufficient anti-tumor immune response. To unleash the full potential of ICIs, the trafficking and infiltration of TITLs to the tumor is necessary and tightly regulated, the highly immunosuppressive tumor microenvironment blunts the infiltration and function of TITLs that reach the tumor in SCLC. Here, we review the characteristics of TITLs, the effects of various factors on T cell infiltration, and possible strategies to restore or promote T cell infiltration in the TME of SCLC.

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

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

Abstract P079: The impact of BCL2 expression on sensitivity to the novel Aurora kinase B inhibitor AZD2811 in small cell lung cancer

Abstract Purpose: Small cell lung cancer (SCLC) is a highly lethal malignancy, with rapidly-acquired therapeutic resistance. In contrast to non-SCLC, treatment strategies based on molecular subtypes have not been well established. Aurora kinase family proteins (AURKA and AURKB) are essential for cell division, regulating chromosomal segregation during mitosis, and are upregulated in cancer. Our group has demonstrated that cMYC-driven SCLC tumors were susceptible to an AURKA inhibitor, alisertib, making AURK proteins an attractive targeted therapeutic approach. A novel AURKB inhibitor, AZD2811NP (nanoparticle), is now being investigated in relapsed SCLC patients (NCT02579226), but molecular mechanisms of resistance have not yet been identified. Here, we hypothesize that targeting predictive markers related to the effect of AZD2811 may reinforce susceptibility to AURKB inhibition. Experimental Design: We evaluated susceptibility to AZD2811 in 63 human-derived SCLC cell lines using 96-hour proliferation assays. To identify translatable biomarkers of response, we correlated AZD2811 IC50 values with genomic (whole exome sequencing, WES), transcriptomic (RNASeq), and proteomic profiling (Reverse Phase Protein Array, RPPA) data. We validated changes in apoptosis and DNA damage markers induced by AZD2811 in SCLC cells infected with the lentivirus vectors expressing BCL-2 and shRNA against BCL-2 using western blot. We used SCLC patient-derived xenograft (PDX) models with distinct BCL-2 profiles to evaluate in vivo antitumor effect. Results: In the SCLC cells treated with AZD2811, 15/63 (24%) and 10/63 (16%) cell lines showed high sensitivity (IC50&amp;lt;30 nM, Cmax) and intermediate sensitivity (IC50=30-100nM). Comparing protein expression, we found that cMYC (Fold change, FC:2.5; P = 0.015) were a positive biomarker of sensitivity, while high BCL-2 (FC:1.86; P = 0.032) associated with resistance. cMYC-high SCLC cell lines that were susceptible to AZD2811 became resistant when BCL-2 was overexpressed. Conversely, BCL-2 knock-down enhanced response to AZD2811, inducing apoptosis and DNA damage, in BCL-2-high cells that were originally resistant to single-agent AZD2811. Similar to Bcl-2 knock-down, treatment with venetoclax (a BCL-2 inhibitor routinely used in other cancers) enhanced apoptosis and DNA damage induction in combination with AZD2811 in cells overexpressing BCL-2. In PDX models with high BCL-2, combination of AZD2811 and venetoclax prominently induced tumor regression and apoptosis compared with each monotherapy, while there was no significant difference in PDX models with low BCL-2 between the combination and the monotherapy. Conclusions: Our preclinical results indicate that high BCL-2 expression reduced the efficacy of AZD2811 in SCLC models, but that Bcl2-driven resistance could be overcome with the combined use of BCL-2 and AURKB inhibitors. Findings support a promising rational combination therapy for BCL-2-high SCLC to enhance response to aurora kinase B inhibition. Citation Format: Azusa Tanimoto, Carminia M. Della Corte, Kavya Ramkumar, Robert J. Cardnell, Allison C. Stewart, Carl M. Gay, Lauren Averett Byers, Qi Wang, Li Shen, Jing Wang, Jon Travers. The impact of BCL2 expression on sensitivity to the novel Aurora kinase B inhibitor AZD2811 in small cell lung cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P079.

Abstract P082: Distinct and significant anti-cancer efficacy of plinabulin in patient derived small cell lung cancer (SCLC) 3D soft agar clonogenic assays

Abstract Plinabulin (Plin) is a new chemical entity and a selective immunomodulating microtubule-targeting agent (SIMBA), which exerts immune-enhancing effects through increasing dendritic cell (DC) maturation and DC-dependent antigen presentation to CD4+ and CD8+ T-Cells. Here we evaluated whether Plin also exerts direct anti-cancer effects against approximately 80 patient derived (PDX) models. Plin was characterized for its ability to inhibit anchorage independent growth and ex vivo colony formation of PDX tumor cells in semi-solid medium. The compound was investigated in PDX models of various cancer types, using a 3D clonogenic assay in a 96-well format. Briefly, tumor cell suspensions were prepared from subcutaneous xenografts in NMRI nu/nu mice and seeded into 96 well ultra-low attachment plates within a layer of semi-solid medium. Plin was added to the assay plate at either day 2 or day 7 and tested at 9 concentrations in half-log increments up to a concentration of 3 µM. Supernatant was exchanged 24 h after dosing and cells were further incubated at 37°C and 7.5 % CO2 up to a total assay time of 8 or 13 days. Colony counts based on image analysis were utilized to evaluate efficacy. Plin inhibited tumor colony formation in a concentration-dependent manner. With Plin treatment beginning 2 days after PDX cell seeding, the most sensitive cancer types were small cell lung cancer (mean absolute IC70 = 0.035 μM; n = 7), bladder cancer (mean absolute IC70 = 0.038 μM; n = 9), and soft tissue sarcoma (mean absolute IC70 = 0.057 μM; n = 10). Melanoma models were observed to be the least sensitive to Plin monotherapy, with a mean absolute IC70 of 1.105 μM (n = 19). With Plin treatment beginning 7 days after PDX cell seeding, based on absolute IC70 values, 9 out of 68 tumor models were sensitive towards plinabulin. The most sensitive histotypes were gastric cancer (Asian, mean abs. IC70 = 0.319 µM, n = 3), small cell lung cancer (mean abs. IC70 = 0.385 µM, n = 7; 3 below 50 nM), osteosarcoma (mean abs. IC70 = 0.624 µM, n = 3), and central nervous system cancer (mean abs. IC70 = 1.521 µM, n = 6). Overall, the most responsive models based on IC70 were the small cell lung cancer models 2156 (abs. IC70 = 0.015 µM), 1129 (abs. IC70 = 0.032 µM) and 650 (abs. IC70 = 0.032 µM), and the osteosarcoma model 1186 (abs. IC70 = 0.027 µM). Soft tissue sarcoma models (n = 8), Her2-enriched breast cancer models (n = 6), melanoma models (n = 9), bladder cancer models (n = 6), and gastric cancer models (Caucasian, n = 3) were observed to be the least sensitive cancer types with a mean IC70 value &amp;gt; 3 µM. In conclusion, using patient-derived tumor models in a 3D clonogenic assay, SCLC tumor types were the most sensitive to Plin. These results provide mechanistic support for the preliminary positive results recently reported with Plin in combination with Nivolumab and Ipilimumab in SCLC patients (Malhotra ASCO 2021). Citation Format: George K. Lloyd, James Tonra, Claudia Goettlich, Tobias Deigner, Ramon Mohanlal, Lan Huang. Distinct and significant anti-cancer efficacy of plinabulin in patient derived small cell lung cancer (SCLC) 3D soft agar clonogenic assays [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P082.

Cold and heterogeneous T cell repertoire is associated with copy number aberrations and loss of immune genes in small-cell lung cancer

Small-cell lung cancer (SCLC) is speculated to harbor complex genomic intratumor heterogeneity (ITH) associated with high recurrence rate and suboptimal response to immunotherapy. Here, using multi-region whole exome/T cell receptor (TCR) sequencing as well as immunohistochemistry, we reveal a rather homogeneous mutational landscape but extremely cold and heterogeneous TCR repertoire in limited-stage SCLC tumors (LS-SCLCs). Compared to localized non-small cell lung cancers, LS-SCLCs have similar predicted neoantigen burden and genomic ITH, but significantly colder and more heterogeneous TCR repertoire associated with higher chromosomal copy number aberration (CNA) burden. Furthermore, copy number loss of IFN-γ pathway genes is frequently observed and positively correlates with CNA burden. Higher mutational burden, higher T cell infiltration and positive PD-L1 expression are associated with longer overall survival (OS), while higher CNA burden is associated with shorter OS in patients with LS-SCLC.

Signatures of plasticity, metastasis, and immunosuppression in an atlas of human small cell lung cancer.

Small cell lung cancer (SCLC) is an aggressive malignancy that includes subtypes defined by differential expression of ASCL1, NEUROD1, and POU2F3 (SCLC-A, -N, and -P, respectively). To define the heterogeneity of tumors and their associated microenvironments across subtypes, we sequenced 155,098 transcriptomes from 21 human biospecimens, including 54,523 SCLC transcriptomes. We observe greater tumor diversity in SCLC than lung adenocarcinoma, driven by canonical, intermediate, and admixed subtypes. We discover a PLCG2-high SCLC phenotype with stem-like, pro-metastatic features that recurs across subtypes and predicts worse overall survival. SCLC exhibits greater immune sequestration and less immune infiltration than lung adenocarcinoma, and SCLC-N shows less immune infiltrate and greater Tcell dysfunction than SCLC-A. We identify a profibrotic, immunosuppressive monocyte/macrophage population in SCLC tumors that is particularly associated with the recurrent, PLCG2-high subpopulation.

TIAM1-RAC1 promote small-cell lung cancer cell survival through antagonizing Nur77-induced BCL2 conformational change.

SummarySmall-cell lung cancer (SCLC), an aggressive neuroendocrine malignancy, has limited treatment options beyond platinum-based chemotherapy, whereafter acquired resistance is rapid and common. By analyzing expression data from SCLC tumors, patient-derived models, and established cell lines, we show that the expression of TIAM1, an activator of the small GTPase RAC1, is associated with a neuroendocrine gene program. TIAM1 depletion or RAC1 inhibition reduces viability and tumorigenicity of SCLC cells by increasing apoptosis associated with conversion of BCL2 from its pro-survival to pro-apoptotic function via BH3 domain exposure. This conversion is dependent upon cytoplasmic translocation of Nur77, an orphan nuclear receptor. TIAM1 interacts with and sequesters Nur77 in SCLC cell nuclei and TIAM1 depletion or RAC1 inhibition promotes Nur77 translocation to the cytoplasm. Mutant TIAM1 with reduced Nur77 binding fails to suppress apoptosis triggered by TIAM1 depletion. In conclusion, TIAM1-RAC1 signaling promotes SCLC cell survival via Nur77 nuclear sequestration.

A Novel Strategy for the Diagnosis of Pulmonary High-Grade Neuroendocrine Tumor.

Correctly diagnosing a histologic type of lung cancer is important for selecting the appropriate treatment because the aggressiveness, chemotherapy regimen, surgical approach, and prognosis vary significantly among histologic types. Pulmonary NETs, which are characterized by neuroendocrine morphologies, represent approximately 20% of all lung cancers. In particular, high-grade neuroendocrine tumors (small cell lung cancer and large cell neuroendocrine tumor) are highly proliferative cancers that have a poorer prognosis than other non-small cell lung cancers. The combination of hematoxylin and eosin staining, Ki-67, and immunostaining of classic neuroendocrine markers, such as chromogranin A, CD56, and synaptophysin, are normally used to diagnose high-grade neuroendocrine tumors; however, they are frequently heterogeneous. This article reviews the diagnostic methods of lung cancer diagnosis focused on immunostaining. In particular, we describe the usefulness of immunostaining by Stathmin-1, which is a cytosolic phosphoprotein and a key regulator of cell division due to its microtubule depolymerization in a phosphorylation-dependent manner, for the diagnosis of high-grade neuroendocrine tumors.

Delta-Like Protein 3 Expression in Paired Chemonaive and Chemorelapsed Small Cell Lung Cancer Samples.

Rovalpituzumab tesirine (Rova-T), an antibody-drug conjugate directed against Delta-like protein 3 (DLL3), is under development for patients with small cell lung cancer (SCLC). DLL3 is expressed on the majority of SCLC samples. Because SCLC is rarely biopsied in the course of disease, data regarding DLL3 expression in relapses is not available. The aim of this study was to investigate the expression of DLL3 in chemorelapsed (but untreated with Rova-T) SCLC samples and compare the results with chemonaive counterparts. Two evaluation methods to assess DLL3 expression were explored. Additionally, we assessed if DLL3 expression of chemorelapsed and/or chemonaive samples has prognostic impact and if it correlates with other clinicopathological data. The study included 30 paired SCLC samples, which were stained with an anti DLL3 antibody. DLL3 expression was assessed using tumor proportion score (TPS) and H-score and was categorized as DLL3 low (TPS < 50%, H-score ≤ 150) and DLL3 high (TPS ≥ 50%, H-score > 150). Expression data were correlated with clinicopathological characteristics. Kaplan–Meier curves were used to illustrate overall survival (OS) depending on DLL3 expression in chemonaive and chemorelapsed samples, respectively, and depending on dynamics of expression during course of therapy. DLL3 was expressed in 86.6% chemonaive and 80% chemorelapsed SCLC samples without significant differences between the two groups. However, the extent of expression varied in a substantial proportion of pairs (36.6% with TPS, 43.3% with H-score), defined as a shift from low to high or high to low expression. TPS and H-score provided comparable results. There were no profound correlations with clinicopathological data. Survival analysis revealed a trend toward a more favorable OS in DLL low-expressing chemonaive SCLC (p = 0.57) and, in turn, in DLL3 high-expressing chemorelapsed SCLC (p = 0.42) as well as in SCLC demonstrating a shift from low to high expression (p = 0.56) without being statistically significant. This is the first study to investigate DLL3 expression in a large cohort of rare paired chemonaive-chemorelapsed SCLC specimens. Comparative analysis revealed that DLL3 expression was not stable during the course of therapy, suggesting therapy-based alterations. Unlike in chemonaive samples, a high DLL3 expression in chemorelapsed samples indicated a trend for a more favorable prognosis. Our results highlight the importance to investigate DLL3 in latest chemorelapsed SCLC tumor tissue.

MA16.03 CRISPR Screen Reveals XPO1 as a Therapeutic Target Strongly Sensitizing to First and Second Line Therapy in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an exceptionally aggressive disease comprising 13% of all lung cancer cases. With limited treatment options that typically result in transient responses, SCLC is responsible for approximately 250,000 deaths globally per year. The recent addition of immunotherapy to first-line platinum-based doublet chemotherapy appears to benefit only a small subset of patients, resulting in a 2-month increase in median overall survival. Major hurdles to improving SCLC treatment include development of rapid chemoresistance and ineffective second line therapies. The identification of more durably effective therapeutic strategies is a major unmet clinical need. We performed an in vitro CRISPR screen in seven SCLC cell lines, including commercially available and short term-cultured cell lines derived from patient-derived-xenografts (PDXs), representing all major SCLC subtypes. We used an in-house druggable genome library including targets for which active inhibitors, either FDA-approved or in clinical development, are available. The screen was performed with two conditions per cell line, untreated and cisplatin-treated, to identify targets whose disruption would specifically sensitize to cisplatin. Candidate targets of interest were validated genetically with independent sgRNAs in Cas9-expressing in vitro and in vivo models (pSpCTRE-PDXs) and pharmacologically, with in vitro synergy assays and PDX treatments. Signaling pathways were studied by western blot, and toxicity studies were performed in vivo, to assess the safety of the agents at pharmacologically effective doses. We performed immunohistochemistry (IHC) to assess expression of candidate targets in SCLC tissue microarrays (TMAs). Our CRISPR screen approach revealed XPO1 (Exportin 1) as a candidate that may contribute to cisplatin resistance across all SCLC subtypes. Combination of Exportin 1 inhibitors with cisplatin demonstrated synergy in vitro, and use of cisplatin with the Exportin 1 inhibitor selinexor showed combinatorial efficacy in vivo in chemonäive SCLC PDXs representing all SCLC subtypes. This efficacy was associated with increased DNA damage and apoptosis. The combination was well tolerated in mice at the drug concentrations tested. Exportin 1 inhibition also exhibited combinatorial synergy with irinotecan, a standard agent use for recurrent SCLC, and combination of selinexor with irinotecan demonstrated substantial efficacy in SCLC PDXs derived from chemorelapsed tumors including models for all SCLC subtypes, again with manageable toxicity profiles. We found SCLC to have the highest XPO1 mRNA expression among a diverse array of tumor histologies. High XPO1 expression was confirmed at the protein level in a SCLC tissue microarray, independent of SCLC subtype. Exportin 1 is highly expressed in SCLC tumors, independent of their subtype, and its inhibition enhances sensitivity to the chemotherapeutic drugs used in first line and second line treatment of SCLC tumors. Our results provide preclinical rationale for the combination of selinexor with cisplatin or with irinotecan as first or second line treatment, respectively, of SCLC.

YAP drives fate conversion and chemoresistance of small cell lung cancer.

Small cell lung cancer (SCLC) has a high degree of plasticity and is characterized by a remarkable response to chemotherapy followed by the development of resistance. Here, we use a mouse SCLC model to show that intratumoral heterogeneity of SCLC is progressively established during SCLC tumorigenesis. YAP/TAZ and Notch are required for the generation of non-neuroendocrine (Non-NE) SCLC tumor cells, but not for the initiation of SCLC. YAP signals through Notch-dependent and Notch-independent pathways to promote the fate conversion of SCLC from NE to Non-NE tumor cells by inducing Rest expression. In addition, YAP activation enhances the chemoresistance in NE SCLC tumor cells, while the inactivation of YAP in Non-NE SCLC tumor cells switches cell death induced by chemotherapy drugs from apoptosis to pyroptosis. Our study demonstrates that YAP plays critical roles in the establishment of intratumoral heterogeneity and highlights the potential of targeting YAP for chemoresistant SCLC.

P66.02 The Prognostic Implication of hes1 Protein Expression in Resected Small Cell Lung Cancers of 247 Cases

Small cell lung cancer (SCLC) is a highly aggressive malignancy prone to early recurrence and metastasis. Preclinical studies have found that Hes1, as a transcription repressor of the basic helix-loop-helix (BHLH) family, can not only prevent the proliferation and migration of SCLC tumor cells, but also inhibit the neuroendocrine transcription factor ASCL1. However, the prognostic implication of Hes1 protein on surgically resected SCLCs remains unclear. The current study aims to analyze the expression pattern and prognostic value of Hes1 protein in SCLC. Two hundred and forty seven surgically resected pure SCLC specimens were reviewed and included in this study by using tissue microarrays (TMA) for immunohistochemistry（IHC）analysis of Hes1 protein on a fully automatic Roche immunohistochemical instruments . And the corresponding clinicopathological features such as age, lymph node metastasis, major cell shape and tumor infiltrating lymphocytes(TILs), etc were reviewed and collected. Correlation analysis of Hes1 protein with clinic pathological features and survival analysis was performed using SPSS 25.0 and Graphpad Prism 5.0. Among the 247 surgically resected pure SCLC patients, 175 (71%) were male and 202 (82%) were less than 65 years. According to the AJCC Cancer Staging Manual (seventh edition), 78 (31.6%) were stage I, 68 (27.5%) were stage II, and 101 (40.9%) were stage III. Hes1 expression was localized in the nucleus of SCLC tumor cells. A total of 129 of the 247 enrolled SCLC patients showed high expression of Hes1 with a positive rate of 52.2%(129/247), and was found positively correlated with a lower age(≤65 yrs., p=0.014), no lymph node metastasis(P=0.003), main cell morphology of round cells(p=0.002), and TILs≤30% (p=0.010). Univariate survival analysis revealed a favorable survival in high expression group for a significant disease free survival (DFS, HR=1.477,95%CI 1.025-2.129, P=0.036 ) and a positive trend of overall survival (OS, HR=1.181,95%CI 0.778-1.792,P=0.435). In limited stage pure small cell lung cancer, high expression of Hes1 protein is related to age, lymph node metastasis, main cell morphology and TILs , which contributes as a potential biomarker for the prognosis of SCLC patients.

P66.07 ASCL1 and DLL3 Expression and Their Clinicopathological Implications in Surgically Resected Pure Small Cell Lung Cancer

Small cell lung cancer (SCLC) is one of the most aggressive malignancies characterized by neuroendocrine (NE) differentiation. Our previous data revealed the achaete-scute homolog 1 (ASCL1) gene was a transcription factor in NE differentiation and highly expressed in SCLC. The Delta-like protein 3 (DLL3), as a direct downstream target of ASCL1, is involved in NE differentiation and carcinogenesis of SCLC. A DLL3-targeted antibody-drug conjugate, rovalpituzumab tesirine (Rova-T) has recently been developed for treatment of SCLC. This study was to investigate the relationship between ASCL1 and DLL3 protein expression and their clinicopathological implications in surgically resected pure SCLC. 247 surgically resected pure SCLC samples with limited clinical stage and follow-up data were retrieved in this retrospective study. ASCL1 and DLL3 protein expression was detected by immunohistochemistry staining in SCLC tissue microarrays. The correlation between ASCL1 and DLL3 protein expression as well as their clinicopathological features were analyzed by chi-square test. Disease-free survival (DFS) and overall survival (OS) in SCLC patients with ASCL1/DLL3 low and high expressions were compared by Kaplan-Meier method and Log-rank test. Among the 247 surgically resected pure SCLC patients, 175 (70.9%) were male and 202 (81.8%) were less than 65 years. According to the AJCC Cancer Staging Manual (seventh edition), 78 (31.6%) were stage I, 68 (27.5%) were stage II, and 101 (40.9%) were stage III. ASCL1 expression was localized in the nucleus of SCLC tumor cells, and 105 (42.5%) patients showed high expression. ASCL1 high expression was associated with clinical stage (p=0.019) and nerve invasion (p=0.030). DLL3 expression was localized in the cytoplasm and membrane of tumor cells, and DLL3 high expression was observed in 188 (72.8%) patients. DLL3 high expression was correlated with vascular invasion (p=0.045). ASCL1 expression was positively associated with DLL3 expression (p=0.030). In addition, DLL3 expression has a strong association with expression of classic NE markers, Synapsin (Syn) and Chromogranin A (CgA). Survival analysis revealed that patients with ASCL1 high expression have a worse OS (p=0.047), whereas further multivariate cox regression analysis showed neither ASCL1 nor DLL3 expression was independent prognostic factors. ASCL1 and DLL3 were highly expressed in pure SCLC tumor cells, and their expression level was positively correlated. The patients with ASCL1 and DLL3 high expression may represent a distinct subgroup of SCLC benefit from targeted therapy. Therefore, ASCL1 and DLL3 could be potential biomarkers served for selection of related patients.

Targeting MYC-enhanced glycolysis for the treatment of small cell lung cancer

IntroductionThe transcription factor MYC is overexpressed in 30% of small cell lung cancer (SCLC) tumors and is known to modulate the balance between two major pathways of metabolism: glycolysis and mitochondrial respiration. This duality of MYC underscores the importance of further investigation into its role in SCLC metabolism and could lead to insights into metabolic targeting approaches.MethodsWe investigated differences in metabolic pathways in transcriptional and metabolomics datasets based on cMYC expression in patient and cell line samples. Metabolic pathway utilization was evaluated by flow cytometry and Seahorse extracellular flux methodology. Glycolysis inhibition was evaluated in vitro and in vivo using PFK158, a small molecular inhibitor of PFKFB3.ResultsMYC-overexpressing SCLC patient samples and cell lines exhibited increased glycolysis gene expression directly mediated by MYC. Further, MYC-overexpressing cell lines displayed enhanced glycolysis consistent with the Warburg effect, while cell lines with low MYC expression appeared more reliant on oxidative metabolism. Inhibition of glycolysis with PFK158 preferentially attenuated glucose uptake, ATP production, and lactate in MYC-overexpressing cell lines. Treatment with PFK158 in xenografts delayed tumor growth and decreased glycolysis gene expression.ConclusionsOur study highlights an in-depth characterization of SCLC metabolic programming and presents glycolysis as a targetable mechanism downstream of MYC that could offer therapeutic benefit in a subset of SCLC patients.

1870TiP Tazemetostat in combination with a PARP Inhibitor or checkpoint inhibitor in patients (Pts) with solid tumors

Overexpression or amplification of enhancer of zeste homolog 2 (EZH2) is described in many tumor types, including small cell lung cancer (SCLC), prostate cancer, and ovarian cancer (OVCA). EZH2 inhibition augmented PARP inhibitor (PARPi) activity in OVCA and metastatic castration-resistant prostate cancer (mCRPC) cell lines and tumors, some of which are resistant to PARPis. EZH2 inhibitor (EZH2i) and PARPi in combination also demonstrated synergy in chemotherapy-resistant SCLC cell lines and tumors.