Role of the CXCL12/CXCR4 axis in milky spots of rats bearing ascitic-type hepatoma

Rat ascitic-type hepatoma AH7974 cells express CXCR4 mRNA and protein at high levels and also show vigorous migratory responses to its ligand CXCL12. We have shown that AMD3100 (a specific CXCR4 antagonist) effectively reduced tumor invasion into the milky spot in Sprague-Dawley rats inoculated with AH7974 cells. A histological analysis revealed that the milky spots from AMD3100-treated rats were both smaller and consisted of fewer constituent cells and blood vessels than those from the AH7974 inoculated rats. Alkaline phosphatase staining also showed a statistically significant reduction in the area of the milky spots in the AMD3100-treated rats in comparison to the AH7974 inoculated rats (P < 0.0001). Green fluorescence protein (GFP)-tagged AH7974 cells were constructed to detect the localization of the tumor cells in the milky spots. There were fewer GFP-tagged AH7974 cells in the AMD3100-treated rats than in the AH7974 inoculated rats. The number of eosinophils and mast cells increased in the milky spots of AH7974-inoculated rats, and angiogenesis was also seen. In comparison, both cell proliferation and angiogenesis were inhibited in the milky spots of the AMD3100-treated rats. Collectively, our results strongly suggest that the CXCR4/CXCL12 axis plays an important role in the development of peritoneal carcinomatosis. As such, CXCR4 may be a potential therapeutic target for peritoneal carcinomatosis.