Nitric oxide-donating aspirin inhibits the growth of pancreatic cancer cells through redox-dependent signaling.
The novel chemopreventive nitric oxide-donating aspirin (NO-ASA) prevents nearly 90% of ductal adenocarcinomas in a animal tumor model. To decipher the mechanism of this effect, we studied in BxPC-3 human pancreatic cancer cells the sequence of signaling events leading from NO-ASA treatment to cell growth inhibition. NO-ASA inhibited the growth of BxPC-3 cells (IC(50) =13 microM), by inhibiting proliferation modestly and inducing apoptosis, necrosis and G(1)/S cell cycle block. At 15 min of treatment with NO-ASA, the intracellular levels of reactive oxygen species (ROS) began increasing (peak at 8h, baseline levels by 24h). ROS activated almost immediately in a time- and concentration-dependent manner the MAPK pathways p38, ERK and JNK (their activation was abrogated by the antioxidant N-acetylcysteine). MAPK activation induced p21(cip-1), which suppressed the levels of cyclin D1 that controls the G(1)/S cell cycle transition. NO-ASA induced COX-2 expression starting 90 min after p21(cip-1) was induced. When COX-2 expression was knocked down using siRNA against cox-2, the expression of p21(cip-1) was induced by NO-ASA, regardless of the level of expression of COX-2, suggesting a marginal, if any, role for COX-2 in the growth inhibitory effect of NO-ASA. These findings along with the temporal sequence of individual changes indicate a signaling sequence that involves ROS-->MAPKs-->p21(cip-1)-->cyclin D1-->cell death. Our findings establish the critical role of ROS as proximal signaling molecules in the action of anticancer compounds and may be useful in designing mechanism-driven approaches to cancer control.
Zhou
Hui
H
Division of Cancer Prevention, Stony Brook University, Life Sciences Building, Room 006, Stony Brook, NY 11794-5200, USA.
Huang
Liqun
L
Sun
Yu
Y
Rigas
Basil
B
D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D017209:Apoptosis; D001241:Aspirin / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D019938:Cyclin D1 / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D009336:Necrosis; D009569:Nitric Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species; D015398:Signal Transduction
D000894:Anti-Inflammatory Agents, Non-Steroidal; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D019938:Cyclin D1; D009569:Nitric Oxide; D001241:Aspirin