The Comparative Pathology of Genetically Engineered Mouse Models for Neuroendocrine Carcinomas of the Lung

Abstract

Introduction Because small cell lung carcinomas (SCLC) are seldom resected, human materials for study are limited. Thus, genetically engineered mouse models (GEMMs) for SCLC and other high-grade lung neuroendocrine (NE) carcinomas are crucial for translational research. Methods The pathologies of five GEMMs were studied in detail and consensus diagnoses reached by four lung cancer pathology experts. Hematoxylin and Eosin and immunostained slides of over 100 mice were obtained from the originating and other laboratories and digitalized. The GEMMs included the original Rb/p53 double knockout (Berns laboratory) and triple knockouts from the Sage, MacPherson and Jacks laboratories (double knockout model plus loss of p130 (Sage laboratory) or loss of Pten (MacPherson and Jacks laboratories). In addition, a GEMM with constitutive co-expression of SV40 large T antigen (Tag) and Ascl1 under the Scgb1a1 promoter from the Linnoila laboratory was included. Results The lung tumors in all of the models had common as well as distinct pathological features. All three conditional knockout models resulted in multiple pulmonary tumors arising mainly from the central compartment (large bronchi) with foci of in situ carcinoma and NE cell hyperplasia. They consisted of inter- and intra-tumor mixtures of SCLC and large cell NE cell carcinoma (LCNEC) in varying proportions. Occasional adeno- or large cell carcinomas were also seen. Extensive vascular and lymphatic invasion and metastases to the mediastinum and liver were noted, mainly of SCLC histology. In the Rb/p53/Pten triple knockout model from the MacPherson and Jacks laboratories and in the constitutive SV40/Tag model many peripherally arising NSCLC tumors having varying degrees of NE marker expression were present (NSCLC-NE tumors). The resultant histological phenotypes were influenced by the introduction of specific genetic alterations, by inactivation of one or both alleles of specific genes, by time from Cre activation and by targeting of lung cells or NE cell subpopulations. Conclusion The five GEMM models studied are representative for the entire spectrum of human high-grade NE carcinomas and are also useful for the study of multistage pathogenesis and the metastatic properties of these tumors. They represent one of the most advanced forms of currently available GEMM models for the study of human cancer.

Increased mitochondrial function downstream from KDM5A histone demethylase rescues differentiation in pRB-deficient cells

“…This allows for the development of novel therapeutic approaches that diminish the aggressiveness of RB-deficient tumors by restoring their differentiation potential and could thus be used alongside existing cancer therapies targeting the cell cycle to augment their efficacy. The involvement of KDM5A and/or mitochondrial functions in determining the differentiation status can be further tested in vivo using recently generated mouse models of highly aggressive SCLC (Gazdar et al 2015). Moreover, peculiarities of the mitochondrial response in RB-deficient tumors compared with normal tissue and RB-positive tumors are poorly understood.…”

Genetic requirement for Mycl and efficacy of RNA Pol I inhibition in mouse models of small cell lung cancer

“…To investigate the potential role of these cells in SCLC, we crossed the Chga-GFP mice with Rb lox/lox ; p53 lox/lox ;p130 lox/lox mice and initiated SCLC via intratracheal instillation of Ad-CMV-Cre (Schaffer et al 2010). This Rb/p53/p130-deleted mouse model recapitulates key features of human SCLC, including neuroendocrine characteristics and metastatic spread (Schaffer et al 2010;Gazdar et al 2015). One month after Cre delivery, at which time macroscopic lesions were not yet evident, we isolated a small number of GFP-positive cells from the lungs of Chga-GFP;Rb lox/lox ;p53 lox/lox ;p130 lox/ lox mice using FACS (Fig.…”

“…We conditionally inactivated Mycl at the time of tumor initiation in two different highly penetrant mouse models of SCLC. In the first cross, we used a model in which intratracheal Ad-Cre (Ad-CMV-Cre) drives deletion of Rb lox/lox ;p53 lox/lox ;p130 lox/lox alleles in the lung epithelium, in which SCLC, often with a large cell neuroendocrine component, rapidly arises from expanding neuroendocrine cells (Schaffer et al 2010;Gazdar et al 2015). Human SCLC almost always exhibits RB/P53 deletion and occasionally RBL2/130 deletion (George et al 2015).…”

“…Gazdar) examined all of the scanned images in detail and captured multiple representative images. Terminology for neuroendocrine tumors was as described previously (Gazdar et al 2015).…”

Tumor heterogeneity in small cell lung cancer defined and investigated in pre-clinical mouse models

“…GEMMs for SCLC and their relevance to the human disease have been reviewed in detail elsewhere (9)(10)(11). Briefly, these models are based on the near-ubiquitous inactivation of the RB and p53 tumor suppressors seen in human SCLC (12).…”