Variations in c‐Myc and p21WAF1 expression protect normal peripheral blood lymphocytes against BimEL‐mediated cell death

We have examined the effect of suberoylanilide hydroxamic acid (SAHA, Vorinostat, Zolinza) on the viability of normal peripheral blood lymphocytes (PBLs) in vitro and on the expression of 20 apoptosis‐related genes. RT‐PCR, western blots and flow cytometry were performed to reveal the proteins of apoptosis machinery that were affected to cause cell death. Our data suggest that PBL markedly resisted for approximately 24 h the destructive activity of the agent, but eventually 60% of cells treated with 4 µmol/L SAHA died within 72 h through mitochondrial way of apoptosis. While the expression of the majority of genes remained indifferent against 4 µmol/L SAHA, the cellular levels of BimEL, Bmf‐2, Bcl‐w and survivin mRNA varied, confirming the pro‐apoptotic response of SAHA treated PBL. In addition, the expression of multifunctional proteins c‐Myc and p21(WAF1) changed profoundly with the time of SAHA treatment. The Bax activator BimEL increased rapidly, driving cells towards apoptosis likely controlled by c‐Myc and p21(WAF1) activities. We suggest that variations in c‐Myc and p21(WAF1) expression decelerate the apoptosis in the early period and increase the resistance of resting PBL against SAHA. Copyright © 2009 John Wiley & Sons, Ltd.