Abstract 2264: RNA sequencing based analysis of transposon-induced tumors reveals novel insights into cancer pathogenesis and progression
Authors: Camilleri Emily T. , Beckmann Pauli J. , Larson Jon D. , Kurata Morito , Shu Jingmin , Pope Emily , Hudson Wendy A. , Temiz Nuri A. , Rathe Susan K. , LaRue Rebecca S. , Sarver Anne E. , Scott Milcah C. , Varshney Jyotika , Modiano Jaime F. , Moriarity Branden S. , Sarver Aaron L. , Seshagiri Somasekar , Largaespada David A. 
Published: August 2018

Current challenges in oncology include the discovery of drivers suitable for targeting using small molecules or antibodies and predictive animal models. We're addressing these challenges in several ways. We have developed mouse models using the Sleeping Beauty (SB) transposon system to perform unbiased, forward genetic screens to define strong candidate cancer genes. Further, our studies and others have utilized transposon mutagenesis to derive cancers from all three germ layers including carcinomas, sarcomas, neuroectodermal tumors, and hematopoietic malignancies. We hypothesize that data from these screens will help to identify genetic drivers of human cancer that are altered at the gene copy number or epigenetic levels. Our T2/Onc SB transposons create fusions with endogenous gene transcripts and RNA sequencing (RNA-seq) reveals the genes targeted in the tumor. From these results, correlations can be drawn between the alteration of specific genes and changes in tumor gene expression patterns. Thus, the goals of our recent research have been to discover novel associations between SB-induced tumor phenotypes and specific driver gene alterations (i.e. the tumor genotype). Moreover, RNA-seq has also revealed tumor molecular subtypes, in many cases with correlating transposon insertion mutations. Several examples will be described: mammary tumors, osteosarcoma (OS), medulloblastoma and central nervous system primitive neuro-ectodermal tumors. In each case, RNA-seq has revealed novel genotype-phenotype correlations including drivers of high cell cycle activity, metastasis, white blood cell exclusion from the tumor, SHH pathway activation, and hormone receptor signaling. These models provide a source of genetically heterogenous tumors with the same initiating mutation useful for identifying cooperating pathways and drivers of specific tumor phenotypes. Secondly, we are using SB transposon mutagenesis to understand the genetic basis of chemotherapy resistance in cancer including OS. In our OS model, SB mutagenesis is an ongoing process due to the constitutive expression of SB transposase, which permits the continued mobilization of transposons. We hypothesize that in vivo treatment with chemotherapy agents will allow tumor cells that contain transposon mutations in chemoresistance genes to persist. Preliminary studies with primary tumor cells derived from SB-enhanced OS tumors demonstrate resistance to combination chemotherapy treatment in vivo. Further analysis to identify candidate chemotherapy resistance genes are currently underway.

Citation Format: Emily T. Camilleri, Pauli J. Beckmann, Jon D. Larson, Morito Kurata, Jingmin Shu, Emily Pope, Wendy A. Hudson, Nuri A. Temiz, Susan K. Rathe, Rebecca S. LaRue, Anne E. Sarver, Milcah C. Scott, Jyotika Varshney, Jaime F. Modiano, Branden S. Moriarity, Aaron L. Sarver, Somasekar Seshagiri, David A. Largaespada. RNA sequencing based analysis of transposon-induced tumors reveals novel insights into cancer pathogenesis and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2264.