Nonpathogenic E. coli displaying decoy-resistant IL18 mutein enhance the efficacy of cancer immunotherapies
The tumor microenvironment can inhibit the efficacy of cancer therapies through mechanisms such as poor trafficking and exhaustion of immune cells. To address this challenge, we exploited the safety, tumor tropism, and ease of genetic manipulation of non-pathogenic Escherichia coli (E. coli) to deliver key immune-activating cytokines to tumors via surface display on the outer membrane of E. coli K-12 DH5a. Non-pathogenic E.coli  expressing murine decoy-resistant IL18 mutein (DR18) induced robust CD8+ T and NK cell-dependent immune responses and suppressed tumor progression in immune-competent colorectal carcinoma and melanoma mouse models. E. coli K-12 DH5a engineered to display human DR18 potently activated mesothelin-targeting CAR NK cells and enhance their trafficking into tumors, which extended survival in an NK cell treatment-resistant mesothelioma xenograft model by enhancing TNFa signaling and upregulating NK activation markers. Our live bacteria-based immunotherapeutic system safely and effectively induces potent anti-tumor responses in treatment-resistant solid tumors, motivating further evaluation of this approach in the clinic. Overall design: To investigate the effect of human DR18 displaying E.coli on MSLN-CAR NK cells, NK cells isolated from 4 donors were treated for 3 hours with YiaT232-hDR18, E. coli (MOI = 1000), YiaT232, E. coli (MOI = 1000), hDR18 (no bacteria, 100ng/ml) and PBS. We then performed gene expression analysis using RNAseq (2 replicates per RNAseq run).