Noninvasive focused ultrasound non-specifically activating spleen immunological function to suppress tumor proliferation: a new strategy for cancer immunotherapy

Abstract Splenic immunomodulation triggered by ultrasound shows a significant anti-inflammatory effect against various inflammatory diseases, whose mechanism is mainly attributable to the activation of cholinergic anti-inflammatory pathway (CAP). However, the potential role and underlying mechanism of splenic ultrasound stimulation in cancer management have been rarely reported and superficially defined. This study first assessed the universal therapeutic effect of focused ultrasound precisely stimulating spleen (FUS sti. spleen) on various tumors under specific ultrasonic dose. It fully demonstrated that FUS directly stimulated splenic immune cell proliferation and activation (especially NK and CD8 T cells) rather than CAP excitation to modulate splenic immune function. Particularly, NK cells are much more indispensable and important in responding to FUS stimulation for cancer suppression than CD8 T cells. RNA sequencing of NK and CD8 T cells, as well as in vitro experiments revealed that FUS firstly regulated calcium-related signaling pathways to further modulate other signaling pathways, such as ECM-receptor interaction, PI3K-AKT signaling pathway, Rap1 signaling pathway and Hippo signaling pathway to promote immune cell proliferation, migration and activation to suppress cancer cell deterioration. Particularly, FUS sti. spleen and FUS intervention on the tumor synergistically induced the best tumor suppression than each of the two taken individually.