REMOVAL OF AFLATOXIN-B1-DNA ADDUCTS AND INVITRO TRANSFORMATION IN MOUSE EMBRYO FIBROBLASTS C3H/1OT1/2

  • 1 January 1983
    • journal article
    • research article
    • Vol. 70  (1) , 135-139
Abstract
The mechanism of in vitro transformation of the mouse embryo fibroblast C3H/10T1/2 clone 8 by aflatoxin B1 (AFB1) was studied in confluent holding (CH) experiments. Confluent cultures of C3H/10T1/2 cells were treated with AFB1 for 16 h, and the DNA adduct composition and concentration were determined by chromatographic procedures after 0, 8, 16 and 40 h of CH when the cells were replated at low density for the expression of their colony-forming ability and the formation of transformed foci. Total adduct concentration and the concentration of the major primary adduct 2,3-dihydro-2-(N7-guanyl)-3-hydroxyaflatoxin B1 (AFB1-N7-Gua) decreased continuously during CH due to spontaneous decomposition and probably also due to enzymatic repair processes. The more chemically stable secondary product 2,3-dihydro-2-(N5-formyl-2'',5'',6''-tramino-4''-oxo-N5-pyrimidyl)-3-hydroxyaflatoxin B1 (AFB1-triamino-Py) accumulated in the DNA and reached its maximum concentration after 16 h of CH. While the loss of total AFB1-DNA adducts during CH was reflected in recovery of viability, the potential to form transformed foci reached a maximum after 16 h of CH and then decreased with continued CH below the initial value. No simple relationship exists between the concentration of the total adducts AFB1-N7-Gua and AFB1-triamino-Py at the time of release from CH and the potential to form transformed foci. DNA lesions or abnormal DNA configurations formed during CH as a consequence of the cellular processing of AFB1-DNA adducts may play a role in the transformation process.