Harnessing innate anti-tumour immunity using a Klebsiella-derived therapeutic to reduce tumour burden and improve outcomes in mouse models of lung cancer

Abstract Tumour regression and increased survival has been associated with certain acute microbial infections. Immune dysfunction contributes to the development and progression of lung cancer, and therapies that re-constitute anti-tumor immune responses provide an important means to effectively treat malignancies and improve health outcomes. We hypothesized that stimulating the innate immune system with bacterial-derived immunomodulators could induce protective anti-cancer immune responses. A Klebsiella-derived drug product, QBKPN (Qu Biologics), was used to specifically stimulate the innate immune niche in the lungs in established mouse models of lung cancer. Repeated subcutaneous administration with QBKPN significantly reduced lung tumor burden and increased survival. The protective action of QBKPN required prior exposure to Klebsiella through either environmental exposure or lung infection. However, this QBKPN-mediated anti-tumour response was independent of adaptive immunity, as the protective effect remained in RAG2-knockout mice. QBKPN intervention was characterized by a rapid, acute-like systemic immune response, including increased circulatory inflammatory cytokines and innate immune cells, leading to recruitment of immune effector cells into the lung tissue, including macrophages and natural killer (NK) cells. In addition to recruitment of innate immune cells, QBKPN increased markers of classically activated macrophages and increased production of NK cell effector molecules. Together, these data suggest that QBKPN, a Klebsiella-derived immunomodulator, causes activation and recruitment of macrophages and NK cells into the lungs, reducing cancer tumour burden and improving survival outcomes.