A robust innate immune response is essential in combating viral pathogens. However, it is equally critical to quell overzealous immune signaling to limit collateral damage and enable inflammation resolution. Pattern recognition receptors are critical regulators of these processes. The cytosolic nucleotide‐binding domain leucine‐rich repeat (NLR; NOD‐like receptor) family of pattern recognition receptors plays essential roles in the sensing of viral pathogen‐associated molecular patterns and is best characterized for itsr pro‐inflammatory biological functions. Specifically, these include the formation of multi‐protein complexes, defined as inflammasomes or NODosomes that regulate the production of IL‐1beta, IL‐18, and pyroptosis, or the induction of NF‐ΚB signaling. While these biological effects are inherently pro‐inflammatory, it is also important to recognize that other NLR family members conversely function to negatively regulate inflammation through modulating signaling initiated by other families of pattern recognition receptors. Mechanistically, these unique NLRs also form multiprotein complexes that act to attenuate a variety of biological signaling pathways, such as the inhibition of NF‐ΚB. This inhibition facilitates inflammation resolution and functions to restore cellular homeostasis. Despite extensive characterization of individual NLR family members, the mechanisms of immune system regulation are highly nuanced and remain enigmatic. This is especially true for non‐inflammasome‐forming, regulatory NLRs. Here, we discuss recent findings associated with NLR family members that play essential roles in the host immune response to viruses and mechanisms by which these pattern recognition receptors may function to regulate antiviral immunity.

Prior studies have defined multiple, but inconsistent, roles for the enigmatic pattern recognition receptor NLRX1 in regulating several cancer-associated biological functions. In this study, we explore the role of NLRX1 in the highly metastatic murine 4T1 mammary tumor model. We describe a functional dichotomy of NLRX1 between two different cellular contexts: expression in healthy host cells versus expression in the 4T1 tumor cells. Using Nlrx1−/− mice engrafted with 4T1 tumors, we demonstrate that NLRX1 functions as a tumor suppressor when expressed in the host cells. Specifically, NLRX1 in healthy host cells attenuates tumor growth and lung metastasis through suppressing characteristics of epithelial–mesenchymal transition and the lung metastatic niche. Conversely, we demonstrate that NLRX1 functions as a tumor promoter when expressed in 4T1 tumor cells using gain- and loss-of-function studies both in vitro and in vivo. Mechanistically, NLRX1 in the tumor cells augments 4T1 aggressiveness and metastasis through regulating epithelial–mesenchymal transition hallmarks, cell death, proliferation, migration, reactive oxygen species levels, and mitochondrial respiration. Collectively, we provide critical insight into NLRX1 function and establish a dichotomous role of NLRX1 in the 4T1 murine mammary carcinoma model that is dictated by cellular context.

Background: Liver cancers are a major cause of morbidity and mortality in patients where effective, non-invasive treatment options remain limited. Objective: Histotripsy is a non-invasive, non-thermal, image-guided focused ultrasound method of ablation that mechanically disrupts cells and offers a range of potential advantages over other ablation modalities. The lack of physiologically and anatomically relevant animal models of human liver cancer has significantly hindered biomedical device development, including histotripsy. Methods: To address these limitations, we developed a clinically relevant large animal orthotopic, dual-tumor model of human liver cancer and utilized these unique animals to evaluate the safety and efficacy of histotripsy. Here, we utilized immunocompromised pigs with genetic modifications in their IL-2RG and RAG2 genes and orthotopically engrafted human hepatocellular carcinoma (HepG2/C3A) and pancreatic adenocarcinoma (Panc-1) cells within the liver. The models were designed to recapitulate primary and metastatic liver tumor phenotypes. Results: Histotripsy enabled real-time visualization of the treatment by the formation of bubble clouds and accurate targeting of the lesions. Histological analysis confirmed the engraftment of tumor cells and the ablation of targeted tissue. Serum biomarkers demonstrated no significant differences in bilirubin, ALT, ALKP, or CK post-treatment, suggesting that histotripsy treatment was well tolerated with minimal hepatic dysfunction or hepatocellular injury. Conclusions: These findings establish a novel, clinically relevant porcine model of primary and metastatic liver tumors and demonstrate the safety and feasibility of using this model for evaluating histotripsy as a noninvasive modality for precise tumor ablation.