Low doses of Peg IFN-α 2a and Nutlin-3 activate p53 pathway through different mechanisms. (A) Peg IFN-α 2a, but not Nutlin-3, increased p-STAT1 in CD34⁺ cells. Treatment with Nutlin-3 or Peg IFN-α 2a alone for 48 hours led to increased cytoplasmic p21, PUMA, and Bak protein levels; treatment with the 2 drugs in combination led to an even greater increase in p21, PUMA and Bak levels. (B) The quantification of cytoplasmic levels of p21, PUMA, and Bak was determined densitometrically and normalized to GAPDH.