Clinical significance of arginase in colorectal cancer.

Arginase, a potent immune inhibitor, existed in much greater abundance in the cytoplasm of cancer cells than in normal cells. Serum arginase levels from 31 patients with colorectal adenocarcinoma were determined by using enzyme immunoassay (mean +/- standard error = 18.96 +/- 4.83 ng/ml) and showed to be significantly higher than levels from control subjects (n = 115, 3.09 +/- 0.22 ng/ml) (P less than 0.005). Surgical samples of 15 patients were individually homogenized and assayed by the same method and revealed that the arginase level in tissues with colorectal cancer was two times greater than the level found in normal mucosal tissues (1.74 +/- 0.31 micrograms/g tissue versus 0.77 +/- 0.09 micrograms/g tissue, P less than 0.005). However, the serum arginase levels in patients with colorectal cancer were independent of their carcinoembryonic antigen (CEA) levels (n = 27, arginase 11.81 +/- 1.88 ng/ml, CEA 17.31 +/- 4.24 ng/ml, r = 0.084, P = 0.666). The results suggested that serum arginase level can be a valuable criterion for preoperative evaluation and possibly postoperative follow-up study. It can also combine with CEA determination to intensify the clinical assessment for colorectal cancer.