Distinct roles but cooperative effect of TLR3/9 agonists and PD-1 blockade in converting the immunotolerant microenvironment of irreversible electroporation-ablated tumors

• Published in: Cellular & molecular immunology Vol. 18; no. 12; pp. 2632 - 2647
• Main Authors: Babikr, Fatma, Wan, Jiangbo, Xu, Aizhang, Wu, Zhaojia, Ahmed, Shahid, Freywald, Andrew, Chibbar, Rajni, Wu, Yue, Moser, Michael, Groot, Gary, Zhang, Wenjun, Zhang, Bing, Xiang, Jim
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2021; Nature Publishing Group
• Subjects: 631/250/251; 631/67/580; Ablation; Agonists; Animal models; Animals; Antibodies; Biomedical and Life Sciences; Biomedicine; Breast cancer; Cancer; CD8 antigen; CD8-Positive T-Lymphocytes; Cell Line, Tumor; CpG islands; Dendritic cells; Electroporation; Growth inhibition; Immune Tolerance; Immunogenicity; Immunological tolerance; Immunology; Immunoregulation; Lymphocytes; Lymphocytes T; Lymphoma; Macrophages; Medical Microbiology; Metastases; Mice; Mice, Inbred C57BL; Microbiology; Ovalbumin; PD-1 protein; PD-L1 protein; Polyinosinic:polycytidylic acid; Programmed Cell Death 1 Receptor - antagonists & inhibitors; TLR3 protein; Toll-Like Receptor 3 - agonists; Toll-Like Receptor 9 - agonists; Toll-like receptors; Tumor microenvironment; Tumor Microenvironment - immunology; Tumors; Vaccine; PD-1-blockade; antitumor immunity; TLR3/9-agonists; CD8; IRE ablation; T-cell response; CD8+ T-cell response
• ISSN: 1672-7681; 2042-0226
• DOI: 10.1038/s41423-021-00796-4

Irreversible electroporation (IRE) is a new cancer ablation technology, but methods to improve IRE-induced therapeutic immunity are only beginning to be investigated. We developed a mouse model bearing large primary (300 mm 3 ) and medium distant (100 mm 3 ) EG7 lymphomas engineered to express ovalbumin (OVA) as a nominal tumor antigen. We established experimental protocols including IRE alone and IRE combined with Toll-like receptor (TLR)3/9 agonists (poly I:C/CpG) (IRE + pIC/CpG), PD-1 blockade (IRE + PD-1 blockade), or both (IRE + Combo) to investigate therapeutic effects on primary and distant EG7 tumors and conversion-promoting effects on the immunotolerant tumor microenvironment (TME). We demonstrated that IRE alone simulated very weak OVA-specific CD8 + T cell responses and did not inhibit primary tumor growth. IRE + pIC/CpG synergistically stimulated more efficient OVA-specific CD8 + T cell responses and primary tumor growth inhibition than IRE + PD-1 blockade. IRE + pIC/CpG played a major role in the modulation of immune cell profiles but a minor role in the downregulation of PD-L1 expression in the TME and vice versa for IRE + PD-1 blockade. IRE + Combo cooperatively induced potent OVA-specific CD8 + T cell immunity and rescued exhausted intratumoral CD8 + T cells, leading to eradication of not only primary tumors but also untreated concomitant distant tumors and lung metastases. IRE + Combo efficiently modulated immune cell profiles, as evidenced by reductions in immunotolerant type-2 (M2) macrophages, myeloid-derived suppressor-cells, plasmacytoid dendritic cells, and regulatory T cells and by increases in immunogenic M1 macrophages, CD169 + macrophages, type-1 conventional dendritic cells, and CD8 + T cells, leading to conversion of immunotolerance in not only primary TMEs but also untreated distant TMEs. IRE + Combo also showed effective therapeutic effects in two breast cancer models. Therefore, our results suggest that IRE + Combo is a promising strategy to improve IRE ablation therapy in cancer.