Investigating Ionic Liquid Chemical Structures for Applications in Whole Tumor Cell Vaccine Immunotherapy

Abstract

Whole tumor cell vaccines are an emerging immunotherapy strategy whereby tumor cells are inactivated and modulated ex vivo prior to injection back into a patient to deliver a library of antigens for the body’s immune system to recognize and target. Currently, irradiation is the most common method of ex vivo induction of cell death in tumor cell vaccines. However, irradiation has limitations, especially insufficient tumor immunogenicity. In this study, we explored ionic liquids (ILs) as alternatives in the preparation of whole tumor cell vaccines. Here, we aimed to create a tunable library of ILs for whole tumor cell vaccines by determining the impact of IL anion length, branching, and unsaturation on 4T1 murine mammary cancer cells. We examined the impact of IL anion structure on cell cytotoxicity, cell death pathways, immunogenicity of cell death, and autophagy activation. We determined that IL-induced cytotoxicity increases with anion carbon chain length and with concentration, and decreases by adding branched methyl, ethyl groups, and double bonds (with constant carbon chain length) in the anion structure. Among all ILs, apoptosis appeared as the primary mechanism of cell death, though the stage of apoptotic activity was tunable. Furthermore, anion branching and unsaturation decreases exposure of calreticulin. ILs were shown to induce ATP release in a concentration-dependent manner, though autophagy was not observed to be induced significantly. This work has provided further characterization of the biological interface of ILs in activating whole tumor cell vaccines and has demonstrated their tunable ability to induce immunogenic activity in cancer.