Wild-type p53-triggered apoptosis is inhibited by bcl-2 in a v-myc-induced T-cell lymphoma line.

Using a temperature sensitive p53 construct (ts p53), we have earlier shown that expression of wild-type (wt) p53 triggers apoptosis in a v-myc-induced T-cell lymphoma line that lacks endogenous p53, and in a Burkitt lymphoma line that carries mutant p53. We have suggested that apoptosis is elicited by the contradictory signals emanating from the constitutively activated myc gene and the growth arresting signal of wt p53 (Ramqvist et al., 1993; Wang et al., 1993). Work in other laboratories has shown that constitutive c-myc expression can induce apoptosis when cell proliferation is inhibited due to the lack of growth stimulating factors. Expression of bcl-2 could inhibit apoptosis. In order to test whether p53-induced apoptosis can be prevented by bcl-2, we have introduced a retrovirally driven bcl-2 construct into our v-myc-induced murine T-cell lymphoma line, previously transfected with ts p53. About 90% of the parental ts p53 transfected cells died of apoptosis within 3 days after induction of wt p53 expression at 32 degrees C. Two clones of ts p53/bcl-2 double transfectants that expressed high levels of bcl-2 from the introduced construct were completely protected from apoptosis, following transfer of the cells to 32 degrees C. One clone that expressed the exogenous bcl-2 only at a low level was partially protected from wt p53-induced apoptosis. Clones of the parental ts p53 carrying cells transfected with the puromycin resistance gene vector, without the bcl-2 gene underwent 90% apoptosis. These results suggest that bcl-2 may prevent apoptosis in cells simultaneously exposed to the proliferation-stimulating effect of activated myc and the growth arresting signal of wt p53.