Abstract 3926: Establishment of patient-derived organoids as ex vivo tool to characterize the molecular mechanisms of SCLC chemo-radiation resistance
Authors: Carrieri Francesca A. , Connis Nick , Grasset Eloise M. , Chan Isaac S. , Luidy-Imada Eddie , Lam Christine , Wang Hailun , Ewald Andrew J. , Marchionni Luigi , Hann Christine L. , Tran Phuoc T. 
Published: September 2020

Abstract
Small cell lung cancer (SCLC) is the most aggressive form of lung malignancies and accounts for 15-20% of all lung cancers. It has the tendency to metastasize early, thus limited-stage SCLC patients receive systemic chemo-radiotherapy (XRT) treatments. SCLC is exceptionally sensitive to XRT and exhibits high response rates; however, the recurrence rate is almost 100% and patients relapse with tumors that resist further chemotherapy. Clearly, elucidating the mechanisms of chemo-radiation resistance in SCLC will contribute to understanding how SCLC resists further treatments, to develop improved therapies and positively impact patient outcomes. Significant limitations for SCLC therapeutic development have been the lack of germane reliable and tractable model systems. Recent advances in establishing 3D organotypic culture have shown that this model can preserve the majority of pathways, key genes, histology and behavior of in situ tumors. Furthermore, patient-derived organoids (PDO) represent a powerful preclinical model that enable real-time cellular and molecular analysis of patient-derived xenograft (PDX) behavior ex vivo. Here, we present a novel patient-derived cancer organoid model to study the molecular underpinnings of XRT resistance in SCLC. Classic and variant SCLC PDX tumor tissues were isolated from mice and mechanically dissociated. Derived organoids were cultured in basal organoid medium. PDOs have been characterized using the SCLC molecular subtype classification reported in literature. RNA for transcriptomic analyses has been obtained to further characterize gene expression profiles of primary PDXs and PDOs, and to reconstruct gene regulatory network associated with XRT resistance. A SCLC PDX served as in vivo system to characterize the response to chemo-radiation resistance. Briefly, PDX tumor bearing mice were treated with: 1) vehicle control; 2) Cisplatin 5mg/kg on d1 plus Etoposide 8mg/kg on d1-2 (EP); 3) Radiotherapy 3Gy x1 on d3 (RT); and 4) both EP/RT. Whole transcriptome profiling among all treatments arms reveals molecular pathways and biological processes associated with XRT resistance. Also, by comparing our data with two previous SCLC patient cohort studies, we identified ideal candidates for functional analyses. SCLC XRT resistance candidate genes will be tested by either treating PDOs with small molecule inhibitors or by cDNA/shRNA lentiviral infection. To assess changes in chemo-radiation sensitivity, chemo-radiation protocols have been established and immunofluorescence staining for Ki67, γH2AX and cleaved caspase 3 served as markers for proliferation, DNA damage and apoptosis, respectively. Although further in-depth characterization is required, we aim to utilize our novel SCLC PDO model as a tool to identify candidate biomarkers to be used for developing therapy responses and translational research.
Citation Format: Francesca A. Carrieri, Nick Connis, Eloise M. Grasset, Isaac S. Chan, Eddie Luidy-Imada, Christine Lam, Hailun Wang, Andrew J. Ewald, Luigi Marchionni, Christine L. Hann, Phuoc T. Tran. Establishment of patient-derived organoids as ex vivo tool to characterize the molecular mechanisms of SCLC chemo-radiation resistance [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3926.