Abstract
Aminoflavone (5‐amino‐2‐(4‐amino‐3‐fluorophenyl)‐6,8‐difluoro‐7‐methylchromen‐4‐one; AF; NSC 686288), a novel anticancer candidate agent, is undergoing clinical evaluation. AF induces DNA‐protein cross‐links (DPCs), γ‐H2AX phosphorylation, aryl hydrocarbon receptor (AhR) signaling, apoptosis and its own metabolism via cytochrome P4501A1 and 1A2 (CYP1A1/1A2) activation in sensitive estrogen receptor positive (ER+) MCF7 breast cancer cells. Estrogen receptor negative (ER−) breast cancer is typically more aggressive with a poorer prognosis. In this investigation, we evaluated the ability of AF to induce reactive oxygen species (ROS) formation, oxidative DNA damage and apoptosis in ER− MDA‐MB‐468 breast cancer cells. The antioxidant, N‐acetyl‐L‐cysteine (NAC), attenuated the cytotoxic effects of AF in MDA‐MB‐468 cells; an effect is also observed in ER+ T47D breast cancer cells. Nonmalignant MCF10A breast epithelial cells were resistant to the cytotoxic effects of AF. AF increased intracellular ROS, an effect blocked by NAC and the CYP1A1/1A2 inhibitor, α‐Naphthoflavone (α‐NF). AF induced oxidative DNA damage as evidenced by increased 8‐oxo‐7,8‐dihydroguanine (8‐oxodG) levels and DPC formation in these cells. AF caused S‐phase arrest corresponding to an increase in p21^(waf1/cip1)^ protein expression. AF induced caspase 3, 8 and 9 activation, caspase‐dependent apoptotic body formation and poly [ADP‐ribose] polymerase (PARP) cleavage. Pretreatment with the pan‐caspase inhibitor, benzyloxycarbonyl‐Val‐Ala‐DL‐Asp(OMe)‐fluoromethylketone inhibited apoptosis and partially inhibited ROS formation and oxidative DNA damage. Pretreatment with NAC attenuated AF‐induced apoptotic body formation and caspase 3 activation. These studies suggest AF inhibits the growth of breast cancer cells in part, by inducing ROS production, oxidative DNA damage and apoptosis and has the potential to treat hormone‐independent breast cancer. © 2007 Wiley‐Liss, Inc.