The role of wild-type p53 in the differentiation of primary hemopoietic and muscle cells.

Experiments previously performed on 32D and C2C12 cell lines indicated that wild type p53 (wtp53) protein has a role in granulocyte and myotube differentiation. Since these are immortal cells, we asked whether the inhibition of differentiation induced by the expression of dominant-negative p53 (dnp53) proteins was dependent on the immortalization-determined microenvironment. Thus, we evaluated the effects produced by interfering with the endogenous p53 gene in murine primary hemopoietic and muscle cells. Expression of dnp53 protein reduced the differentiation of bone marrow cells into granulocytes and macrophages. Moreover, p53 activation was measurable during the differentiation process of primary myoblasts, while interference with this activation led to a consistent slow down of terminal differentiation. Since the impairment of the differentiation was not accompanied by alterations in the cell cycle withdrawal and in the rate of apoptosis which are coupled with these types of differentiation, the data here reported support a specific role for p53 in the differentiation process. However, the difference in the intensity of inhibition between immortal and primary cells, i. e., complete versus slow down, respectively, suggests that the immortalization process might render the cells more sensitive to the loss of wtp53 activity for the differentiation process.