Nuclear Factor-κB Signaling in Murine Models of Malignant Pleural Mesothelioma

Background: Malignant pleural mesothelioma (MPM) is an aggressive asbestos-associated cancer in which inflammatory pathways may contribute to tumor behavior. NF-κB signaling is a central mediator of inflammation and cell survival, but the relative contributions of its associated enzymes, IKKα- and IKKβ, in MPM models remain incompletely understood. Methods: We characterized the involvement of IKKα- and IKKβ in tumor formation using several in vitro approaches and the intrapleural or subcutaneous delivery of three murine MPM cell models (AB2, AE17 and KPM1). The experimental approaches included shRNA silencing of Chuk and Ikbkb—the genes encoding the activity of IKKα- and IKKβ—and tumor growth, apoptosis and colony formation measurements. Exploratory pathway and transcriptional analyses were carried out following RNA-sequencing of our murine cell lines and a publicly available human gene expression dataset was also analyzed to provide complementary evidence. Results: Activation of the IKKα- and IKKβ was confirmed in the AB2, AE17 and KPM1 cell lines. Silencing both Chuk and Ikbkb decreased target and cross-target transcripts and metabolic growth. Importantly, Chuk silencing was associated with increased early apoptotic staining in AE17 and KPM1 cells, increased late apoptotic staining in AE17 cells and reduced colony formation in all cell models. Furthermore, Chuk-associated effects on tumor burden and activity were more notable than Ikbkb-associated effects in both intrapleural and subcutaneous tumor formation parameters. Finally, while canonical NF-κB gene-set clustering in both human and murine tumor samples identified specific and shared pathways and transcriptional profiles supporting the in vitro murine assay findings, the analyses remained exploratory and did not specifically establish target dependency. Conclusions: Our data support the involvement of IKK/NF-κB-associated signaling in cell survival, clonogenicity and tumor growth in several MPM murine cell models and identify Chuk-related signaling as a promising target in future studies.