Investigation of the Effective Dose of Agonistic 4-1Bb Monoclonal Antibody in A Murine Colon Cancer Metastasis Model

Purpose: The aim of this study was to find the dose of agonistic 4-1BB monoclonal antibody (mAb) that results in optimal T cell activation.Methods: Cancer was induced in mice by an intrahepatic parenchymal injection of 1x10(5) cells of CT26 cells. Cancer-carrying mice (n=84) were divided into seven groups and treated with either rat IgG or agonistic 4-1BB monoclonal antibody (mAb) (5 mu g, 10 mu g, 20 mu g, 100 mu g, 200 mu g, or 300 mu g). All treatments were administered intraperitoneally on days 7, 9, and 11. Mice from each group were sacrificed oil days 14, 28, and 42. Hanested livers were weighed and the numbers of T cells in the splenocytes were analyzed with a FACS Vantage flow cytometer.Results: Liver weights increased when 5 mu g of agonistic 4-1BB mAb was administered, but showed no additional weight increase for closes greater than 10 mu g. The absolute numbers of CD4+ and CD8+ T cells increased in groups treated with low doses of agoniistic 4-1BB mAb (5 mu g, 10 mu g, or 20 mu g), but did not increase in the groups treated with high doses of mAb (100 mu g, 200 mu g, or 300 mu g). The levels of CD4/annexin V and CD8/annexin V increased as the dose increased, and the absolute cell numbers of CD4/annexin V were greater than those of CD8/annexin V.Conclusion: Liver weight, including the cancer mass, failed to increase at agonistic 4-1BB mAb doses greater than 10 mu g. A high dose (>= 100 mu g) of agonistic 4-1BB mAb resulted in lower Counts of absolute T cells. This study suggests that a low close (20 mu g) of agonistic 4-1BB mAb can be used for optimal T cell activation in combination with other anti-cancer treatments. (J Korean Surg Soc 2010;78:7-16)