Experimental study on synergistic pulses improving the tumor microenvironment and assisting immunotherapy

The development and metastasis of tumors depend on the highly complex and heterogeneous tumor microenvironment (TME). Synergistic pulsed electric fields refer to a sequential combination of high-voltage nanosecond pulses and low-voltage microsecond pulses. No systematic research has been reported on the ameliorative effect of this field on the TME and the related mechanisms. This study used tumor-bearing models established with male Balb/c nude mice and male C57BL/6 mice as research subjects. At the molecular, cellular, and tissue levels, this study employed Masson staining, immunofluorescence staining, immunohistochemical staining, and <i>in vivo</i> small animal imaging technology. This study multi-angle analyzed the effect of synergistic pulse treatment on key physical and chemical indicators of the tumor microenvironment (TME) for the first time. It also explored the effect of its combined application with exogenously injected natural killer (NK) cell therapy. Experimental results showed that synergistic pulse treatment could effectively improve the physical properties of the TME. It reduced tumor stiffness and density, and alleviated the hypoxic state. Meanwhile, it could stimulate the body's anti-tumor immune response and promote the infiltration of cytotoxic immune cells into tumors. Furthermore, this pulse could significantly promote the enrichment and intratumoral penetration of exogenously injected NK cells at tumors, thereby boosting cellular immunotherapy efficacy. This study demonstrated that synergistic pulsed electric fields can potentially remodel the TME and enhance immune cells' anti-tumor effect for tumor ablation. It provides a new technical direction for inhibiting tumor recurrence and metastasis and demonstrates potential for clinical translation.