Multiple studies have highlighted the abundance of NETs within tumor metastatic foci.26 Excessive formation of NETs promotes tumor progression and metastasis by exacerbating inflammation.27–29 Consistently, we found significant increases in the serum levels of NETs formation markers (MPO) in mice transplanted with the gut microbiota of patients with intrahepatic metastatic HCC. The gene discussed is MPO; the disease is hepatocellular carcinoma.