LEUKEMOGENIC ACTION OF PHORBOL IN INTACT AND THYMECTOMIZED MICE OF DIFFERENT STRAINS

Phorbol, the unesterified parent alcohol of the skin promoter TPA [12-0-tetradecanoyl-phorbol-13-acetate] was administered i.p., twice weekly, throughout the lifetime of mice of 7 inbred strains: males and females of AKR/J, C3Heb and BALB/c, and females of SJL/J, DBA/2, SWR and C57BL. A striking difference in strain response was observed, with a pronounced leukemogenic effect in SWR, a significant shortening of the latent period for spontaneous reticulum cell sarcomas (RCNB) in SJL/J and no demonstrable effect in the other strains. When mice of 3 of the above mentioned strains (SWR, SJL/J and AKR/J) were thymectomized prior to the beginning of phorbol treatment, different patterns of response were again observed. Thymectomy did not influence the leukemia incidence in SWR mice, slightly inhibited RCNB development in SJL/J mice and converted phorbol into a leukemogenic agent for AKR/J mice.