Stimulation of ultraviolet-induced carcinogenesis by 1,3-Bis(2-chloroethyl)-1-nitrosourea.

The influence of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) on ultraviolet-induced carcinogenesis was examined in hairless mouse skin in vivo. Noncarcinogenic amounts of topically applied BCNU and carcinogenic levels of UVB energy were utilized in the study. The applications of BCNU significantly accelerated the appearance and growth of the cutaneous tumors in this study. Thus, the BCNU acted as either a promoting or a cocarcinogenic agent for ultraviolet-induced cancer formation. Although the mechanism of this effect has not been established, avoidance of extensive sun exposure would probably be prudent when topical BCNU is being utilized therapeutically.