Objective: To determine the gene expression profiles of the JAK/STAT pathway members STAT3, STAT5A, STAT5B at both mRNA and protein levels in HL-60 and K-562 leukemia cells that were undergoing apoptosis following high-dose methylprednisolone (MP) treatment.
Methods: HL-60 cells were treated with 0.1 mM MP and K-562 cells were treated with 0.4 mM MP according to their IC(50) values. STAT3, STAT5A, and STAT5B mRNA relative expression levels were determined by qRT-PCR whereas the protein levels were detected via western-blot analysis and apoptosis was evaluated by Annexin V method.
Results: A significant decrease was seen in STAT5A mRNA relative expression level at 48 hours of MP treatment (P < 0.05) both in HL-60 and K-562 cells. Other STATs showed a lower downregulation in their relative expressions at 48 hours at mRNA level for both of the cell lines. STAT proteins showed no expression change in K-562 cells in time course experiments but while STAT5A expression was downregulated; STAT5B showed an increase at 96 hours in HL-60 cells. Apoptosis was triggered by high-dose MP treatment that was evaluated by fluorescent microscopy.
Conclusion: The JAK/STAT pathway components may play an important role in the apoptosis mechanism of leukemic cells under MP treatment in HL-60 and K-562 cells. Other pathways may also be involved with a post-translational modification seen in the HL-60 cell line, with both upregulation and downregulation of protein expression levels of STAT5B and STAT5A, respectively.