The study found that a gene called KiSS-1, which makes the peptide kisspeptin, is less active in liver cancer that spreads into the portal vein, while an enzyme called MMP‑9 is more active. Lower KiSS‑1 levels were linked to higher MMP‑9, suggesting KiSS‑1 might help keep cancer from spreading by keeping MMP‑9 low.

Tumor metastasis-suppressor gene KiSS-1 is related to the metastasis of malignancies. However, its correlation to the metastasis, especially the formation of portal vein tumor thrombus (PVTT), of hepatocellular carcinoma (HCC) has seldom been reported. This study was to investigate the function of KiSS-1 gene in the formation of PVTT of HCC, and explore the machanism. The expression of KiSS-1 and matrix metalloproteinase-9 (MMP-9) in 50 specimens of HCC (31 cases with PVTT and 19 cases without PVTT) and 11 specimens of PVTT was detected by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). The positive rates of KiSS-1 mRNA and protein were significantly lower in PVTT group and HCC with PVTT group than in HCC without PVTT group (18.2% and 16.1 % vs. 63.2%, 0% and 12.9% vs. 47.4%, P < 0.05)û the positive rates of MMP-9 mRNA and protein were significantly higher in PVTT group and HCC with PVTT group than in HCC without PVTT group (72.7% and 77.4% vs. 31.6%, 81.8% and 83.9% vs. 42.1%, P < 0.05). There was no significant difference between PVTT group and HCC with PVTT group (P > 0.05). KiSS-1 expression was negatively related to MMP-9 expression (r=-0.362 for mRNA, and r=-0.473 for protein, each P < 0.05). KiSS-1 and MMP-9 are closely related to the formation of PVTT. KiSS-1 gene might suppress the formation of PVTT by suppressing MMP-9 synthesis.