Tumor initiation in mouse skin by cutting oils.

In order to study the skin tumor-initiating potential for fresh and used cutting oils, a chronic animal bioassay following an initiation-promotion protocol was performed. Tumor initiation was performed by topical application of a single dose of neat fresh/used cutting oil on the mouse skin. After a week, these animals were treated topically with 12-O-tetradecanoylphorbol 13-acetate (TPA), a potent skin tumor promoter. Repeated application of TPA resulted in the appearance of tumors almost at the same time (6-8 weeks) in the groups initiated with fresh or used cutting oil. After a prolonged application of TPA, for 28 weeks, it was observed that the cumulative number of tumors and tumor-bearing animals in the used oil initiated group was slightly less compared to that exposed to a fresh variety of oil. Histopathological examination of the tumors could not show any qualitative differences in the nature of tumors developed in both groups. It seems that both fresh and used cutting oils act as potent skin tumor initiators.