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Background - SCLC is the most aggressive lung cancer type and with the worst prognosis. There are four molecular subtypes based on the high expression of distinct transcription factors and with different therapeutic vulnerabilities. However, all share transcriptional addiction as pathogenic mechanism. Lurbinectedin is a novel oncogenic transcription inhibitor, approved in the United States and other countries for the treatment of adult patients with metastatic SCLC with disease progression on or after platinum-based chemotherapy. The aim of this study was to analyze the activity of lurbinectedin in the different SCLC molecular subtypes and to investigate new biomarkers of response. Methods and Results - We have characterized a panel of 20 SCLC human cell lines based on the expression of ASCL1, NEUROD1, YAP1 and POU2F3, where lurbinectedin yielded a mean IC50 value of 6.52 nM, which is considerable greater than the activity exerted by topotecan, irinotecan, carboplatin, etoposide, olaparib, alisertib and navitoclax (IC50 100 µM-100 nM). Lurbinectedin potency is high in the four molecular subtypes, with IC50 values of 4.1, 14.9, 7.2, and 0.2 nM for SCLC-A, -N, -I and -P, respectively. However, high expression of POU2F3 correlated with better responses. In fact, mean IC50 was 0.28 nM for POU2F3high cells versus 12.1 nM for all POU2F3low cells (p=0.0443). Additionally, basal SLFN11 levels were evaluated, observing that SLFN11high cells responded better to lurbinectedin, with IC50 values of 1.1 nM versus 11.8 nM for SLFN11low (p=0.05). Likewise, lurbinectedin treatment induced greater antitumor activity in SLFN11high tumor-bearing mice (H526: T/C, 18% on day 11) than in SLFN11low tumor-bearing mice (H82: T/C, 65% on day 7) after intravenous treatment at 0.18 mg/kg (on days 0, 7 and 14). Finally, SLFN11 expression was evaluated by IHC in FFPE tumor samples from SCLC patients participating in a multicenter phase II clinical trial in advanced solid tumors (NCT02454972), which allowed lurbinectedin accelerated approval in this indication by FDA. Patients with higher expression of SLFN11 had a slightly better overall survival (OS at 6 months: 68.4% ( Conclusions - Lurbinectedin is highly effective in all molecular subtypes of SCLC in vitro and in vivo, with IC50 values at least two logs more potent than for other antitumoral agents and its activity is even greater in tumors with high POU2F3 expression and/or high SLFN11 expression. Citation Format: Marta Martínez Diez, Gema Santamaría Nuñez, María José Guillén, Daniel Rueda, Eva Maria Garrido-Martin, Pablo Avilés, Carmen Cuevas. Lurbinectedin shows potent activity in all four molecular subtypes of small cell lung cancer (SCLC) and POU2F3 and SLFN11 are biomarkers for a better response. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6247.

Immunotherapy based on Immune Checkpoint blockade (ICB) has become a significant therapeutic option for advanced Non Small Cell Lung Cancer (NSCLC) patients. However, there is an urgent need to find novel biomarkers that to reliably stratify good responders to immunotherapy. Currently, the available biomarkers are not specific enough. Exosomes are small membrane vesicles with sizes of 30-100 nm secreted by most cell types including cancer cells. Exosomes operate as an intercellular communication system by sending proteins, mRNA and miRNAs among other relevant RNA molecules. Exosomes enriched with miRNAS are involved in proliferation, differentiation, maduration and immune cell activation. Moreover, in cancer cells miRNA and other small RNA molecule expressions are dysregulated. Exosomes produced from cancer patient's plasma have been shown to be accurate diagnostic tools for the disease. In this study we profiled miRNAs and other small RNA cargo by exosome of plasma samples from 77 Non Small Cell Lung Cancer (NSCLC) metastatic patients before and after the first cycle of immunotherapy to evaluate the potentiality of predicting response to immunotherapy. We perform exosomes together with RNA isolation and small RNAseq sequencing from plasma samples before and after the first ICB cycle. Two independent softwares were used to identify small RNAs (RNAtoolbox and mirMaster). Prior ICB treatment we did not find differentially expressed miRNAs or other small RNA between good and bad responders. Interestingly we identified 12 exosomal miRNA differentially expressed between good and bad responders after the first cycle of ICB. Intriguingly, levels of miR-134-5p, miR-142-3p, miR-143-3p among others previously associated with NSCLC were found to be considerably higher in the good responder group than the bad responder group. Regarding other smallRNA molecules we observed a great variety and variability of piRNA, rRNA, scaRNA, lncRNA, snoRNA, snRNA, miscRNA and circRNA. To address the function of miRNA and other differentially expressed RNA molecules, we consulted KEGG, GO and Reactome for gene regulatory networks. Interestingly, KEGG results show pathways in cancer as top hit and Reactome highlight Immune System and cancer hits. In conclusion, we observed that patients that have favorable response to ICB have distinctive plasma exosomal miRNA patterns that could be used as possible biomarkers for predicting the effectiveness of immunotherapy in advanced NSCLC patients Citation Format: Maria Garrido-Barros, Javier Oliver, Juan Luis Onieva, Beatriz Martinez-Galvez, Jaime Duddelman, Antonio Rueda, Elisabeth Perez, Emilio Alba, Inmaculada Ramos, Juan Zafra, Manuel Cobo, Isabel Barragán. Dynamic characterization of small RNAs in non small cell lung cancer exosomes under immune-checkpoint inhibitor treatments. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3746.

Background: Microtubule targeting agents have demonstrated to be very effective antitumoral drugs. The development of novel anti-tubulin agents with more efficient mechanisms of action presents several challenges due to their poor solubility, troublesome synthesis or purification, and toxicities. In this work, we present the novel anti-tubulin agent PM534, a synthetic small molecule that shows efficient antitumoral and antiangiogenic properties in vitro and in vivo. Methods and Results: PM534 exhibits a potent antitumor activity in vitro with a mean GI50 value in the low nanomolar range in several different human cancer cell lines. Washout in vitro experiments show irreversible cellular effects after 1h in contact with the compound, compelling the cells to apoptotic cell death likely due to PM534 induced disorganization of the tubulin cytoskeleton. PM534 inhibits migration and invasion of tumor cells in vitro, and arrests the cell cycle in the G2/M phase, forcing them to apoptosis. In addition, PM534 presents potent antiangiogenic effects in vitro, robustly inhibiting endothelial cells proliferation and migration, and the formation of angiotubes. The in vivo antitumor activity of PM534 was characterized in human-derived tumors xenografted in athymic nu/nu mice, namely breast (MDA-MB-231), and pancreas (Mia-Paca-2). PM534 was intravenously administered once per week for three consecutive weeks at 5.0 mg/kg. In vivo PM534-induced antitumor activity (vs. placebo) was seen in MDA-MB-231 (T/C, 0.3% on Day 28; TV, p Conclusions: Based on in vitro activity against different human tumor cell lines, in vivo activity in xenografted human tumors, as well as on its anti-angiogenic properties, the safety, pharmacology and preliminary antitumor activity of PM534 will be evaluated in a first-in-human clinical trial to be conducted in patients with advanced solid tumors. Citation Format: Marta Martínez Diez, María José Muñoz-Alonso, Gema Santamaría Nuñez, María José Guillén, María Ángela Oliva, Eva Maria Garrido-Martin, Pablo Avilés, J. Fernando Díaz, Carmen Cuevas. The novel antitubulin agent PM534 exhibits potent antitumoral and antiangiogenic properties in vitro and in vivo. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6243.

The irruption of the immunotherapy for the treatment of non-small cell lung cancer (NSCLC) based on Immune Checkpoint Inhibitors (ICI) PD-1 and PD-L1 inhibitors is considered a treatment revolution. However, only a small percentage of patients benefit with ICI treatment over the long term, and precise biomarkers that can recognize these individuals before or early during treatment have so far eluded. PD-L1 expression and tumor mutational burden (TMB) are the most well studied biomarkers for predicting response to PD- (L)1 blockade-based ICI prior to treatment. TMB is still being clinically assessed whereas PD-L1 has several drawbacks for prediction of persistent benefit. Our aim is to evaluate the basal state and dynamic changes of cell-free DNA (cfDNA) concentration to predict and monitor response in NSCLC patients starting ICI. A total of 248 cfDNA concentration measurements were performed from 87 NSCLC patients. The quantification was done before the start of the treatment, at the second ICI cycle, after 6 and 12 months in treatment, and at progression if it was within the first 12 months. Quality and quantity of the cfDNA was assessed using Qubit High Sensitivity and Bioanalyzer 2100. We first explored the association with response of the basal cell-free DNA concentration using Mann-Whitney-Wilcoxon test. The longitudinal analysis between different time points was tested with Wilcoxon signed-rank tests. Response was ascertained using RECIST parameters at 3, 6, and 12 months. We evaluated the utility of the cfDNA concentration as a prognostic factor using Mantel-Cox test. The response association results indicate that early and long-term response is associated with lower levels of basal cfDNA (p Citation Format: Isabel Barragan, Elisabeth Perez-Ruiz, Juan Luis Onieva, Maria Garrido-Ramos, Beatriz Martinez-Galvez, Jaime Dubbelman, Emilio Alba, Juan Zafra, Manuel Cobo, Javier Oliver, Antonio Rueda-Dominguez. Cell-free DNA concentration as a prognostic biomarker in patients with non-small cell lung cancer under immunotherapy treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1044.

Background - Ecubectedin (PM14) is a novel transcriptional inhibitor related to ecteinascidins family. In this work, we present its antiproliferative activity and mechanism of action. The in vitro antitumor activity obtained in cellular models has been also demonstrated in in vivo models. Methods and results - The antineoplastic activity of ecubectedin was evaluated in a panel of cell lines representative of different solid human cancers, by MTT assays. Ecubectedin exhibits potent antitumor in vitro activity with mean GI50 values in the very low nanomolar range. Electrophoretic Mobility Shift assays demonstrate that ecubectedin binds to DNA and experiments of 3H-uridine incorporation show that the drug efficiently inhibits mRNA synthesis (85% reduction after 90 min). Moreover, ecubectedin specifically inhibits transactivated transcription, as evaluated in a reporter system of the transcriptional activity mediated by NF-κB after activation with TNFα. In the presence of ecubectedin, transactivation was almost completely abolished. The mechanism of transcriptional inhibition involves the stalling and irreversible proteasomal degradation of elongating RNA Pol II. As a final event, ecubectedin induces double strand breaks in the DNA, inducing cell cycle arrest in the S-phase that can be followed through flow cytometry and triggers apoptotic death of the tumor cell as seen through Annexin V flow cytometry assays. The in vivo antitumor activity of ecubectedin was characterized in xenografted tumors of human origin in athymic nu/nu mice, namely breast (MDA-MB-231), soft tissue sarcoma (HT-1080), SCLC (H526 and H82) and prostate (22Rv1). Ecubectedin was intravenously administered (at 1.25 mg/kg) on days 0, 7 and 14. Compared to placebo, ecubectedin treatment of mice bearing xenografts resulted in a statistically significant reduction of volume in MDA-MB-231 (p≤0.0005 on days 7-35), HT-1080 (p≤0.0004 on days 2-14), H82 (p≤0.0001 on days 5-14), H526 (p≤0.0001 from day 4 to the end of the experimental period), and 22Rv1 (p≤0.0001 on days 3-14) tumors. In mice bearing MDA-MB-231, H526 and 22Rv1 tumors, complete tumor remissions were seen in 1/10 (lasting 103 days), 9/10 (lasting 220 days) and 7/10 (lasting 13 days) ecubectedin-treated animals, respectively. Conclusions - Ecubectedin is a novel transcriptional inhibitor that displays potent antiproliferative activity in different human solid cancer models in vitro and in vivo. The drug is currently in clinical development in Phase II trials. Citation Format: Gema Santamaría Nuñez, Marta Martínez Diez, María José Guillén, Eva Maria Garrido-Martin, Pablo Avilés, Carmen Cuevas. Ecubectedin is a novel transcriptional inhibitor that displays potent antitumor effects in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1622.

Cutaneous melanoma (CM) is an aggressive malignant tumor of epidermal melanocytes for which treatment options and survival chances decrease dramatically when metastatic. To date, immunotherapy is becoming a new standard treatment for CM although less than 30% of the patients´ response positively. Therefore, there is a strong interest to identify response predictors and molecular pathways that might lead to therapy failure. Two novel biomarker sources are LncRNA and CircRNA which can function as natural sponges of miRNA as competitive endogenous RNAs (ceRNA) or can associate to RNA-Binding Proteins (RBP) to regulate gene expression. Moreover, several studies have revealed that ceRNA networks are implicated in tumorigenic processes. Considering this, we set to interrogate the role of the ceRNA in the prediction of response to CM immunotherapy. In this pilot study, differential expression was quantified by RNA-seq in 16 FFPE pre-treatment metastatic samples from CM patients treated with Nivolumab. Total RNA isolation was performed from 10 µm slides (4) with RNAeasy FFPE kit. Total RNAseq was done with Truseq Stranded RNA gold kit, and libraries were sequenced on Illumina Nextseq 550. LncRNA were obtained by STARs alignment and explored on LncATLAS. To assess the presence of high confident cirRNA we used 5 different pipelines with a minimum filtering cut-off of 2 junction reads in at least 2 samples and with at least 3 software. Deseq2 pipeline of total mapped reads was used to perform differential expression. We identified 23 circRNA and 74 lncRNA differentially expressed (DE) with a fold change of 1.5 and a p value < 0,01. Ingenuity pathway analysis was carried out to generate DE ceRNA-mRNA networks and associated RBP networks. Interestingly, in the DE ceRNA-mRNA networks, most of the 47 significant canonical pathways comprised immunological pathways such the antigen presentation pathway, Th1 and Th2 activation pathways and PD1-PDL1 cancer immunotherapy pathways. Regarding the DE ceRNA associated RBP networks, HOTAIR regulatory pathway and senescence as well as G1/S cell cycle checkpoint regulator pathways were enriched. Furthermore, we were able to predict the interaction of the DE ceRNA with the activation of key promoters of the immune response such as IL27 (Interleukin 27), EIB3 (Epstein-Barr Virus Induced 3), IL2 (Interleukin 2) and IFNA2 (Interferon Alpha2), as well as the inhibition of negative immune regulators such as SAFB2 (Distal-Less Homeobox 2) and FOXD1 (Forkhead Box D1). In conclusion, we have evidenced for the first time the potential utility of ceRNA as immunotherapy predictors. We have generated a response signature of ceRNA expression and used network analysis to associate them with specific key modulators of the immune response. This study opens a new venue for the investigation of the role of these regulatory ncRNA in the resistance to immunotherapy in cancer. Citation Format: Javier Oliver, Juan Luis Onieva, Maria Garrido-Barros, Alicia Garrido-Aranda, Vanessa De Luque, Martina Alvarez, Alfonso Sanchez, Elisabeth Perez, Patricia Chaves, Maria Jose Lozano, Miguel Berciano, Manolo Cobo, Emilio Alba, Antonio Rueda, Isabel Barragan. Association of ceRNA dysregulation with clinical Response to Immunotherapy in cutaneous melanoma (CM) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1538.

Lung cancer has the second highest incidence and leads cancer mortality worldwide, being Non-Small Cell Lung Cancer (NSCLC) the most prevalent subtype. Immunotherapy with checkpoint blockers has shown outstanding benefits in a subset of NSCLC patients, which are not accurately identified due to the lack of robust biomarkers of response. We hypothesize that specific molecular alterations of NSCLC tumor cells impact the immune microenvironment. Defining this association could improve the prediction of response to immunotherapy. This work aims to identify a multiparametric biomarker signature. We studied 178 tumor samples from a cohort of early stage NSCLC with complete clinical annotation. We analyzed their molecular aberrations, calculated their Tumor Mutational Burden and described their immune landscape by immunohistochemistry and a dedicated RNAseq panel. We defined novel subgroups of NSCLC tumors with specific immune, molecular and clinical features, showing an association between their molecular genotype and immune phenotype. Based on these data, subgroups were proposed as pro-immunogenic, pro-tumorigenic or mixed. Adenocarcinomas clustered in 4 groups. The pro-tumorigenic group had a significant higher proportion of alterations in ARID1A, FGF10, ROS1, TP53. One pro-immunogenic group had a significant higher proportion of MET alterations and lower proportion of EGFR alterations. An immune mixed group significantly accrued never smokers and had no alterations in FGF10. Squamous cell carcinomas clustered in 4 groups. The pro-tumorigenic group had a significant higher proportion of alterations in CCND1, FGF3, FGF10, FGF19, NOTCH1, PIK3CA, PIK3CB, TFRC. A pro-immunogenic group had a significant higher infiltration of T CD4+, T CD8+ and B cells and a higher overall survival. Another pro-immunogenic group had a significant absence of MYCN and NF1 alterations. Taken together we identified a set of candidate predictive biomarkers of response to immunotherapy in NSCLC. Genes overexpressed in pro-immunogenic tumors are related to adaptive immune response stimulation (CD28, FCRLA, JCHAIN, LY9, MS4A1, SLAMF7, TNFRSF9, TNFRSF17), antigen presentation (CD1C, CD1D, HLA-A), apoptosis (FAS), immune chemotaxis (CCL20, CCR4, CCR6), and immune regulation (CD53, PDCD1, SH2D1A, ZAP70). On the other hand, genes upregulated in pro-tumorigenic tumors are involved in angiogenesis (VEGFA), cell cycle regulation (BUB1, CCNB2, FOXM1, MAD2L1, TOP2A), cell growth/survival (IGF1R), DNA replication/repair (KIAA0101) and iron metabolism (HMBS, TFRC). These findings are being validated by Digital Spatial Profiling in a cohort of patients with advanced stage NSCLC that were treated with checkpoint blockers. If confirmed, these results could remarkably improve patient selection and the benefit upon immunotherapy. Citation Format: Javier Ramos-Paradas, David Gomez-Sanchez, Aranzazu Rosado, Alvaro Conrado Ucero, Nuria Carrizo, Ana Belen Enguita, Maria Teresa Muñoz, Esther Conde, Luis Paz-Ares, Eva Maria Garrido-Martin. Comprehensive analysis of non-small cell lung cancer identifies molecular genotype-immunophenotype associations and candidate biomarkers predictive of response to immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1245.