Ultrasound-guided activation of the stimulator of interferon genes pathway for cancer immunotherapy

Recent studies have shown that the activation of the innate immune sensor cyclic GMP–AMP synthase–stimulator of interferon genes (cGAS-STING) promotes antigen presentation and T-cell activation, thus transforming cold tumors to immunologically responsive tumors. However, because STING is a cytosolic protein and a key mediator of inflammation, activation of STING needs to be specific to antigen-presenting cells (APCs) in tumor tissues. To address this technical challenge and meet the clinical need, we developed a technology termed MUSIC (Microbubble-assisted Ultrasound-guided Immunotherapy of Cancer) that utilizes gas-filled microbubbles (MBs) conjugated with APC-targeting antibodies, and loaded with the STING activator cGAMP. Our results show that, upon exposure to US, MUSIC produces robust STING activation and type I interferon responses in APCs and more efficiently primes antigen-specific CD4+ and CD8+ T cells in vitro. These immune stimulatory effects of MUSIC directly translated into antitumor responses in vivo, where we showed that the MUSIC was able to generate antitumor effects against syngeneic orthotopic primary (EO771) and metastatic (4T1) murine breast cancer models as well as against two syngeneic murine melanoma models (B16-F10 and D4M). We also confirmed the establishment of systemic immune memory following MUSIC treatments as mice rejected tumor cells upon re-challenge.