Adenoviral vectors transduce alveolar macrophages in lung cancer models

Abstract

Adenoviral vectors expressing Cre recombinase are commonly used to initiate tumor formation in murine lung cancer models. While these vectors are designed to target genetic recombination to lung epithelial cells, adenoviruses can infect additional cell types that potentially influence tumor development. Our goal was to explore the consequences of adenoviral-mediated alveolar macrophage (AM) transduction in a Kras-initiated lung tumor model. As expected, treatment of animals harboring the KrasLSL-G12D allele and an inducible green fluorescence protein (GFP) tracking allele with an adenoviral vector expressing Cre recombinase under the control of the cytomegalovirus (CMV) promoter (Ad5-CMV-Cre), caused GFP-positive lung adenocarcinomas. Surprisingly, however, up to 70% of the total GFP+ cells were AM, and GFP+ AM could be detected 6 months after tumor initiation, and transduced AM demonstrated Kras activation and increased proliferation. In contrast, recombination was not detected in other immune cell populations and AM recombination could be eliminated by tumor initiation with an adenovirus expressing Cre recombinase under the control of the surfactant protein C (SPC) promoter. In addition, AM isolated from KrasLSL-G12D animals and transduced by Ad5-CMV-Cre ex vivo displayed prolonged survival in vitro and increased the growth of murine lung adenocarcinoma CMT/167 cells when co-injected in an orthotopic flank model. Given the importance of the immune system in tumor development and progression, inadvertent AM transduction by Ad5-CMV-Cre merits careful consideration during lung cancer model selection particularly if studies evaluating the tumor-immune interactions are planned.

Phagocytosis increases an oxidative metabolic and immune suppressive signature in tumor macrophages

“…Importantly, the slower growth of these tumors allows the microenvironment to develop over time, which more closely resembles the long-term tumor residency of macrophages in human tumors. Previous viral-Cre–induced lung cancer models have documented transduction of lung-resident AMs and consequently modification of conditional allele by Cre recombinase in AMs ( Tippimanchai et al, 2018 ). Thus, we developed a novel model that specifically induces tdTomato protein expression and oncogenic alterations in neoplastic cells to enable tracking of phagocytic activity ( Fig.…”

Effects of Dexmedetomidine on Immune Cells: A Narrative Review

“… Wu R. S. et al (2015) found that DEX could enhance the phagocytic activity of macrophages in mice with endotoxemia. Tippimanchai et al (2018) suggested that DEX could reduce the number of alveolar macrophages and inhibit their phagocytosis in septic mice. García et al (2003) suggest that α 2 -AR controls phagocytosis and chemotaxis in primary cultured rat peritoneal macrophages, maintaining phagocytosis at optimal levels.…”

Developmental Insights into Lung Cancer

“…Beyond these two important effects, mutation induction in bystander cells may also substantially influence epithelial cell response. For instance, one study found when using Ad5-Cre to induce oncogenic Kras that 70% of the recombined cells were alveolar macrophages that exhibited a phenotype and persisted in the lungs for up to 6 months, thus significantly altering the immune environment (Tippimanchai et al 2018). While the coadministration of immunosuppressive medications and use of cell type-specific promoters may mitigate some of these concerns, it should be noted that promoter element-driven constructs may not faithfully recapitulate the endogenous levels and patterns of gene expression in vivo since they lack long-range regulatory elements (Schoenfelder & Fraser 2019).…”