Transforming activity of the RL-akt gene, a c-akt gene activated by long terminal repeat insertion in murine leukemia RL male 1 cells

The unique antigen peptide pRL1 on BALB/c radiation-induced leukemia RL(mal e)1 cells is derived from the normally untranslated 5' region of the mouse c-akt gene. Insertion of an endogenous long terminal repeat into the first coding exon of the gene resulted in the enhanced production of an altered a kt protein, RL-akt, and creation of the tumor rejection antigen peptide pRL 1. In this study, we constructed an RL-akt-expressing vector to investigate the transforming ability and anti-apoptotic activity of RK-akt in NIH/3T3 cells. RL-akt-expressing clones formed more colonies than did c-akt-express ing clones in soft agar and exhibited increased saturation density, a lower serum requirement for growth, and tumorigenicity on athymic nude mice. Imm unoblot analysis of subcellular protein distribution showed that a consider able proportion of RL-akt was distributed in the membrane fraction. Thus, R L-akt expressed in NIH/3T3 cells appeared to behave like the v-akt oncoprot ein. Furthermore, the RL-akt gene conferred resistance to the apoptosis ind uced by the calcium ionophore A23187 and by ultraviolet irradiation of NIH/ 3T3 cells. These findings indicate that the RL-akt gene is able to transfor m cells and exerts an anti-apoptotic effect on recipient cells, thereby imp licating the gene in leukemogenesis of RL(male)1 cells. Mol. Carcinog. 26:2 86-297, 1999. (C) 1999 Wiley-Liss, Inc.