Use of IC tags in short-term carcinogenicity study on CB6F1 TGrasH2 mice.

We studied the effect of IC tags, subcutaneously implanted animal identification tools, on rasH2 mice. A 26-week short-term carcinogenicity study was performed on a total of 299 mice including 75 male and female rasH2 mice each, and 74 male and 75 female non-Tg mice from the same litter as the rasH2 mice divided into a non-IC tag group, the IC-tag group, acetone group, TPA group and MNU group (all of the animals except for those in the non-IC tag group) had IC tags implanted subcutaneously in their backs. The administration methods of the positive control drugs TPA (2.5 micro g/kg, 3 times/week, percutaneously) and MNU (75 mg/kg, single intraperitoneal injection) were based on the protocol of the ILSI/HESI international collaborative study. The results showed no differences in the tumorigenic incidence and organs developing tumors between the IC tag and non-IC tag groups in both rasH2 and non-Tg mice. In the positive control MNU group, the tumorigenic incidence and organs developing tumors were the same as the background data and no promotion of carcinogenesis was observed. In all IC tag groups including the TPA group and MNU group, a fibrous capsule was formed around the IC tags subcutaneously, but no inflammatory changes or neoplastic changes were observed. From these findings, it was concluded that the IC tag has no effect on a 26-week carcinogenicity test of rasH2 mice under the conditions of the present study.