Resistance to phorbol ester-induced differentiation in human myeloid leukemia cells: A hypothetic role for the mRNA stabilization process

UM384 cells, derived from the human myeloid leukemia U937 cell line, fail to differentiate in response to 12-O-tetradecanoylphorbol-13-acetate (TPA). Using cDNA microarray and real-time quantitative PCR (RT-QPCR) approaches, we observed a difference in the response to TPA treatment: all the genes from U937 cells were continuously modulated from 2 to 24 h. In UM384 cells, 60% of the genes were transiently modulated at 2 h, then returned to control levels at 24 h. Moreover, HuR, an AU-rich element-binding protein (ARE-BP), was differentially located in the two cell lines. Therefore, a defect of mRNA stabilization could be responsible for the resistance of UM384 cells to TPA-induced differentiation, suggesting a possible role for the post-transcriptional regulation in the leukemogenesis.