Deciphering the immune contexture of premalignancy in a murine model of lung squamous cell carcinoma
Embargo Date
2027-09-03
OA Version
Citation
Abstract
Lung cancer (LC) remains the leading cause of cancer death worldwide, taking more lives annually than breast, colon, and prostate cancer combined. Despite the strong association of LC with smoking, not all smokers will develop lung cancer. Expansions of large-scale screening programs and improvements in early detection driven by research programs have increased detection of patients with both early-stage cancer and the premalignant lesions (PMLs) that precede it. However, clinical tools to identify which PMLs will progress to invasive carcinoma to stratify at-risk patients for intervention and prevention strategies are still lacking, and implementation of these strategies remains an urgent need to address LC mortality. Therefore, a greater understanding of the factors contributing to lung cancer tumorigenesis is critical. The PMLs that precede lung squamous cell carcinoma (LUSC), the second most common LC subtype accounting for 20-30% of LC cases, arise within the airway field of injury caused by smoking. Our group and others have established focused efforts defining the molecular alterations that drive progression of these precursor lesions and have found that these changes can identify patients at risk for progression. Among these alterations are downregulation of immune pathways such as antigen processing/presentation, suggesting a defect in immunosurveillance of developing PMLs may play a role in preinvasive disease progression. However, a mechanistic understanding of the precise immune contribution to lesion progression is still lacking, and robust model systems are needed to address this gap.
To identify the mechanisms underlying progression, we conducted bulk RNA sequencing (RNAseq) transcriptomic profiling of the carcinogen-induced N-Nitrosotris-2(-chloroethyl)urea (NTCU) murine model of LUSC and found several patterns of gene expression in the NTCU mouse model were significantly associated with those found in human PMLs. Using cell type deconvolution and highly multiplexed imaging mass cytometry (IMC), we observed a reduction in several T cell populations as well as an increase in myeloid populations with increasing PML histological severity, aligning with findings from human preinvasive disease. The parallels in transcriptomic and cell-level alterations between NTCU-induced mouse and human premalignancy suggest that changes in immune response to developing PMLs may drive progression in both settings, making the NTCU model an appropriate representation of human preinvasive disease.
A challenge in establishing clinical intervention strategies for squamous PMLs is that many of these lesions regress without intervention. NTCU-induced premalignancy in different inbred laboratory mouse strains reflects this phenotype, as there exists a spectrum of differential sensitivity to NTCU. To further establish how strain differences may reflect progression and regression of squamous PMLs, we used the carcinogen-sensitive A/J and carcinogen-resistant C57BL/6J mouse strains to represent progressive and regressive preinvasive disease, respectively, and conducted a large multimodal profiling study. Using multiplexed IMC and single cell RNAseq we identified an expansion of the Keratin 5+ basal cell population, which had significant copy number variations (CNVs) and may recruit inflammatory myeloid populations to the lesion microenvironment. We also found a reduction in cytotoxic T lymphocytes (CTLs) as well as an increase in FoxP3+ regulatory T cells (Treg cells), macrophage, and neutrophil populations, aligning with our previous studies as well as findings in the human context that suggest an immunosuppressive and inflammatory microenvironment is established early during lesion development. Lastly, we examined the impact of immunomodulation on PML progression in the NTCU-sensitive mouse by inhibiting IL-1β following carcinogen exposure. While IL-1β inhibition did somewhat mitigate tumor progression following treatment cessation, it did not prevent invasive LUSC tumor formation, likely due to preexisting defects in immunosurveillance capacity in the A/J mouse impacting early tumor control.
Taken together, this work not only validates the preclinical utility of the NTCU mouse model by demonstrating key similarities to transcriptomic alterations in immune function pathways that may underpin PML progression in the human, but also identifies several immune populations that may contribute to a microenvironment permissive of lesion progression. By increasing our mechanistic understanding of the contribution of the immune system to early LUSC tumorigenesis, this work will support the development of immunomodulatory-based cancer interception strategies, and the rationale for deployment of those interventions during lung squamous precancer.
Description
2024