Use of bacterial chassis for the intratumoral delivery of a super-interferon gamma in a breast cancer model 2306491

Abstract Introduction Gamma interferon (IFNγ) is a key cytokine during in inflammation and cancer. In fact, studies showed an increased survival rates in those patients with high levels of tumor-infiltrating IFNγ. However, its high aggregation when produced recombinantly, as well as its short half-life, requires of high administration doses, resulting in toxicity and limiting its clinical use. In our lab, we generated a super-human IFNγ by introducing point mutations which showed an enhance biological activity. Furthermore, we used an attenuated bacterial chassis developed in our lab to locally deliver this IFNγ directly intratumorally in a rodent breast cancer model. Methods Computational tools (FoldX and ModelX) were used to predict mutations with increased stability and receptor binding. All variants were secreted by our chassis, and its activity was tested using HEK-Blue IFNγ reporter cells. Inflammatory and anti-tumor effects were evaluated in THP1 monocytes and MDA231/MCF7 tumor cell lines. In vivo studies were performed in WT and NOD-scid mice after mammary tumor inoculation followed by intratumoral treatment with IFNγ-secreting chassis. Results We generated a human IFNγ mutant with a 10-fold higher activity and 7-fold improved production by our chassis. The variant showed greater thermal stability and stronger inflammatory and anti-proliferative effects in cell lines. In vivo, it significantly increased immune-cell recruitment and boosted inflammatory gene signatures within the tumor environment. Conclusion Our chassis can efficiently secrete functional IFNγ, and computationally predicted mutations resulted in a super-IFNγ with enhanced stability, production, and activity. Super-IFNγ intratumoral delivery resulted in enhanced immune cell infiltration and an increased inflammatory genes expression in vivo. Future work with in vivo models will extend tumor environment effects and currently, we are evaluating the possibility to combine IFNγ with other immunotherapies such as cancer vaccinology. Funding Source ERC grant Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)