MTE01.01 GEMM of Lung Cancer

Abstract

The primary induction of lung cancer is difficult to study in humans because patients often present very late in the course of their disease. Genetically engineered mouse models (GEMMs) have therefore emerged as crucial bridging strategies between understanding pathogenic mechanisms and clinical translation. Importantly, they reveal insights on the events and processes underlying tumor initiation and progression, studies which are not possible when employing transplantation or chemically-induced model systems. The recent advent of next-generation sequencing technologies has provided us with an in-depth characterization of the cancer genome of lung adenocarcinoma (LUAD) (1), squamous cell carcinoma (LUSC) (2) and small cell lung cancer (SCLC) (3). While these studies have highlighted the genetic complexities of lung cancers, attention is now focused on elucidating “driver” mutations that confer a growth advantage, from “passenger” mutations that have little impact on malignant transformation. Investigating the loss or gain-of-function of individual genes, alone or in combination, can be directly addressed using GEMM systems. The “gold-standard” lung cancer models are based on Cre-LoxP recombination technology that enable the formation of autochthonous tumors from a limited number of somatic cells in a spatial and temporal fashion. Critically, tumors arise sporadically within the lung, in the setting of an intact immune microenvironment. GEMMs are designed to harbor genetic mutations frequently identified in human lung cancer. Cre-inducible alleles are engineered to disrupt tumor suppressor genes (LoxP sites flanking key exons (floxed), that are removed upon recombination) and/or activate oncogenes (LoxP-flanked stop codons (lox-stop-lox) that result in gene expression upon recombination). Cre-recombinase is delivered to the lung via inhalation or intra-tracheal injection of a recombinant adenovirus (Ad5) expressing Cre-recombinase under the control of a ubiquitous cytomegalovirus (CMV) promoter. Expression of Cre-recombinase directs the recombination of floxed alleles in a variety of epithelial cell types in the adult mouse lung (4,5). Utilizing this approach enabled investigators to interrogate the functional consequences of genetic alterations found in human lung cancer through the generation of models of LUAD, SCLC and more recently lung LUSC (6). Moreover, the recent advent of CRISPR-Cas9 gene-editing technology now enables us to interrogate the functional interaction between multiple genetic alterations in a high-throughput setting (7). Furthermore, the generation of cell type specific Ad5-Cre viruses, that restrict Cre expression, and thus recombination, to alveolar type II (ATII) (Ad5-SPC-Cre), club (Ad5-CC10-Cre), neuroendocrine (Ad5-CGRP-Cre) and basal (Ad5-K5-Cre, Ad5-K14-Cre) (8) cells, have provided insights into the cellular origins of different subtypes of lung cancer (9,10). Critically, unlike patient-derived xenograft (PDX) models, one additional advantage of GEMMs is the ability to interrogate the interplay between tumor cells and immune cells present in the tumor microenvironment. Such studies are crucial given the success of immune checkpoint inhibitors in lung cancer patients. This presentation will outline lung cancer GEMMs commonly used in the field and how these models can be utilized to identify cancer initiating cells, understand the molecular pathways underlying tumorigenesis, the immune microenvironment of lung cancer, and importantly to identify vulnerabilities that can be exploited for the design of improved treatment modalities for patients. 1. The Cancer Genome Atlas Research Network, Comprehensive molecular profiling of lung adenocarcinoma (2014) Nature, 511 (7511) 543-550. 2. The Cancer Genome Atlas Research Network, Comprehensive genomic characterization of squamous cell lung cancers (2012) Nature, 489 (7417) 519-525. 3. George et al., Comprehensive genomic profiles of small cell lung cancer (2015) Nature, 524 (7563) 47-53. 4. Best et al., Combining cell type-restricted adenoviral targeting with immunostaining and flow cytometry to identify cells-of-origin of lung cancer (2018) Methods in Molecular Biology, 1725 15-29. 5. DuPage et al., Conditional mouse lung cancer models using adenoviral or lentiviral delivery of Cre recombinase (2009) Nature Protocols, 4 (7) 1064-1072. 6. Farago et al., SnapShot: Lung cancer models (2012) Cell, 149 (1) 246-246e1. 7.Rogers et al., A quantitative and multiplexed approach to uncover the fitness landscape of tumor suppression in vivo (2017) Nature Methods, 14 (7) 737-742. 8. Ferone et al., SOX2 is the determining oncogenic switch in promoting lung squamous cell carcinoma from different cells of origin (2016) Cancer Cell, 30 (4) 519-532. 9. Sutherland et al., Cell of origin of small cell lung cancer: inactivation of Trp53 and Rb1 in distinct cell types of adult mouse lung (2011) Cancer Cell, 19 (6) 754-764. 10. Sutherland et al., Multiple cells-of-origin of mutant K-Ras-induced mouse lung adenocarcinoma (2014) Proc. Natl. Acad. Sci. USA, 111 (13) 4952-2957. cell-of-origin, GEMM, tumor development