Involvement of wild-type p53 in pre-B-cell differentiation in vitro.

Wild-type p53 protein is a growth modulator whose inactivation has been found to be a key event in malignant transformation. Reconstitution of wild-type p53 in the p53-nonproducer, Abelson murine leukemia virus-transformed pre-B-cell line L12 gave rise to stably growing clones. Wild-type p53-producer derived cell lines exhibit an altered cell cycle, however. More cells with an extended G0/G1 phase were found than in the p53-nonproducer parental cell line. Furthermore, when injected into syngeneic mice, these cells induced a lower incidence of tumors and these tumors were less aggressive. Analysis of immunoglobulin expression revealed that wild-type p53 induced the expression of cytoplasmic immunoglobulin mu heavy chain. In addition, these derived cells lines exhibited increased levels of a B-cell-specific surface marker, B220. These results suggest that wild-type p53 may function as a cell differentiation factor that can induce development of pre-B cells into a more advanced stage in the pathway of B-cell maturation. In these pre-B cells, wild-type p53 may induce cell differentiation without terminal growth arrest of the cell population.