Fig. 1

Effect of l-arginine and arginase activity on the metastatic colonization of colon cancer cells. GFP-transfected CT26 murine colon cancer cells (2 × 10⁵) were intrasplenically inoculated into wild-type BALB/c mice (day 0). Then, nor-NOHA (20 mg/kg) was injected intraperitoneally on days 5, 7, 9, 11, and 13. A Experimental schemes are shown. B Metastatic colonization in liver tissue was evaluated using an in vivo imaging system on day 14. Representative images of normal liver and GFP-expressing CT26 cell-bearing livers are shown. C HE staining of liver tissues was performed, and representative images are shown. D The sera were collected from normal and liver metastatic colonization model mice on day 14. Serum-free amino acid levels were evaluated by HPLC. The mean values and SDs (n = 4–5, three independent experiments) are shown. E Serum arginase activities of normal and liver metastasis model mice were determined by EIA. The mean values and SDs (n = 4) are shown. F Serum arginase activities of liver metastasis model mice injected with DMSO or nor-NOHA (20 mg/kg) were determined by EIA. The mean values and SDs (n = 4) are shown. G Metastatic colonization in liver tissue of mice injected with DMSO or nor-NOHA (20 mg/kg) was evaluated using an in vivo imaging system on day 14. Representative images of normal liver and GFP-expressing CT26 cell-bearing livers are shown. Photon flux ratios were determined from images of liver metastatic colonization model mice (n = 4, three independent experiments). *P < 0.05 by Student’s t-test. H HE staining of liver tissue was performed 14 days after inoculation. Bars in the images represent 500 μm. Ratios of the tumor area relative to the total liver tissue area were calculated by the ImageJ software. The mean values and SDs from four independent mice are shown. *P < 0.05 by Student’s t-test