Nanosecond pulsed electric field ablation-induced modulation of sphingolipid metabolism is associated with Ly6c2 + mononuclear phagocyte differentiation in liver cancer.

Preclinical studies have proven that nanosecond pulsed electric field (nsPEF) ablation can be a safe and effective treatment for humans with unresectable liver cancer that are ineligible for thermal ablation. The concomitant activation of anti-tumor immunity by nsPEF can also potentially prevent tumor recurrence. However, whether nsPEF exhibits similar efficacy in a clinical setting remains to be investigated. A prospective clinical trial (clinicaltrials.gov identifier: NCT04039747) was conducted to evaluate the safety and efficacy of ultrasound (US)-guided nsPEF ablation in 15 patients with unresectable liver cancer that were ineligible for thermal ablation. We found that nsPEF ablation was safe and produced a 12-month recurrence-free survival (RFS) and local RFS of 60% (9/15) and 86.7% (13/15), respectively, in the enrolled patients. Integrative proteomic and metabolomic analysis showed that sphingolipid metabolism was the most significantly enriched pathway in patient sera after nsPEF without recurrence within 8 months. A similar upregulation of sphingolipid metabolism was observed in the intratumoral mononuclear phagocytes (MNPs), rather than other immune and nonimmune cells, of an nsPEF-treated mouse model. We then demonstrated that lymphocyte antigen 6 complex, locus C2-positive (Ly6c2 + ) monocytes first differentiated into Ly6c2 + monocyte-derived macrophages (MDMs) with an increase in sphingolipid metabolic activity, and subsequently into Ly6c2 + dendritic cells (DCs). Ly6c2 + DCs communicated with CD8 + T cells and increased the proportions of IFN-γ + CD8 + memory T cells after nsPEF, and this finding was subsequently confirmed by depletion of liver Ly6c2 + MNPs. In conclusion, nsPEF was a safe and effective treatment for liver cancer. The alteration of sphingolipid metabolism induced by nsPEF was associated with the differentiation of Ly6c2 + MNPs, and subsequently induced the formation of memory CD8 + T cells with potent anti-tumor effect.