Mapping lung squamous cell carcinoma pathogenesis through in vitro and in vivo models

Abstract

Lung cancer is the main cause of cancer death worldwide, with lung squamous cell carcinoma (LUSC) being the second most frequent subtype. Preclinical LUSC models recapitulating human disease pathogenesis are key for the development of early intervention approaches and improved therapies. Here, we review advances and challenges in the generation of LUSC models, from 2D and 3D cultures, to murine models. We discuss how molecular profiling of premalignant lesions and invasive LUSC has contributed to the refinement of in vitro and in vivo models, and in turn, how these systems have increased our understanding of LUSC biology and therapeutic vulnerabilities.

Fig. 1. In vitro models of lung cancer and their application in in vivo studies.

Establishment of air−liquid-interface (ALI) and organoid cultures from human or mouse airway epithelial cells and LUSC tissue. Following ALI or 3D culture, normal airway epithelial basal cells produce pseudostratified epithelial sheets or hollow organoids containing differentiated cells, respectively. In contrast, LUSC cells give rise to epithelial sheets with features of dysplasia and more solid, disorganised organoids. Cultured cells may be subjected to genetic and pharmacological manipulation to investigate the phenotypic consequences of molecular alterations recurrently identified in LUSC samples. Organoids can be used in in vitro drug screenings and may be implanted into mice to evaluate their ability to give rise to tumours in vivo and response to therapies. ECM extracellular matrix.

Fig. 2. Interaction of signalling pathways demonstrated in in vivo and in vitro models of LUSC.

SOX2, ECT2, PKCι (encoded by PRKCI), and PI3K signalling cooperate to promote a neoplastic cell fate in LUSC models. AKT is a downstream effector of stimulated p110α. Full AKT activation is achieved when phosphorylated at both positions S473 and T308. High levels of SOX2 have been correlated with upregulated phospho-AKT. PKCι phosphorylates and directly interacts with ECT2 to promote anchorage-independent growth and invasion through downstream targets. PKCι phosphorylates SOX2 favouring squamous cell fate and decreased differentiation. Loss of p53, PTEN, and KEAP1 have been used to model LUSC phenotypes both in vitro and in vivo. Simultaneous loss of p53 and KEAP1 has shown synergistic effects, inducing increased proliferation, metastatic potential, and resistance to oxidative stress. p53 activity can inhibit PI3K signalling through PTEN-dependent and potentially-independent mechanisms in squamous cell carcinomas. Additional interactions between depicted proteins have been described in other cellular contexts.

Fig. 3. Genetic alterations used in the generation of in vitro and in vivo models of LUSC.

Oncoprint showing frequency of genetic and transcriptional changes in the indicated genes across 469 lung squamous cell carcinoma samples from human donors included in The Cancer Genome Atlas (TCGA) PanCancer Atlas dataset. Normal adjacent tissue samples in the cohort were used as a reference for gene expression changes (z-score threshold ± 2.0) (downloaded from https://www.cbioportal.org/).