Inhibition of NADPH oxidase 4 activates apoptosis via the AKT/apoptosis signal-regulating kinase 1 pathway in pancreatic cancer PANC-1 cells

Abstract

Pancreatic adenocarcinoma is an aggressive human malignancy and is characterized by resistance to apoptosis. Recently, NADPH oxidase (Nox) 4-mediated generation of intracellular reactive oxygen species (ROS) was proposed to confer antiapoptotic activity and thus a growth advantage to pancreatic cancer cells. The signaling mechanism by which Nox4 transmits cell survival signals remains unclear. Here, we show that both a flavoprotein inhibitor, diphenylene iodonium (DPI), and small interfering RNAs designed to target Nox4 mRNA (siNox4R-NAs) inhibited superoxide production in PANC-1 pancreatic cancer cells, and depletion of ROS by DPI or siNox4RNAs induced apoptosis. Parallely, DPI treatment and siNox4RNA transfection blocked activation of the cell survival kinase AKT by attenuating phosphorylation of AKT. Furthermore, AKT phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) on Ser-83 was reduced by DPI and siNox4RNAs. When ASK1Ser83Ala (an AKT phosphorylation-defective ASK1 mutant) was introduced into PANC-1 cells, this mutant alone induced apoptosis. But, addition of DPI or co-transfection of siNox4RNA had no additive effect, indicating that the mutant can substitute for these reagents in apoptosis induction. Taken together, these findings suggest that ROS generated by Nox4, at least in part, transmit cell survival signals through the AKT-ASK1 pathway in pancreatic cancer cells and their depletion leads to apoptosis.

NADPH oxidase-4 mediates protection against chronic load-induced stress in mouse hearts by enhancing angiogenesis

“…Additionally, Nox4 reportedly has prosurvival effects in certain tumors and is thought to be a suitable therapeutic target (37,38). Our results suggest, however, that caution should be exercised in using Nox4-targeted cancer therapy in patients with cardiac overload (e.g., hypertension) to avoid cardiotoxicity.…”

Nox enzymes, ROS, and chronic disease: An example of antagonistic pleiotropy

“…In pancreatic cancer cells, depletion of Nox4 or ROS triggered apopotosis [142] predicting a therapeutic effect of Nox inhibition in treating this type of cancer. Cell survival involved activation of NF kappa-B- [136] and Akt- [142] dependent pro-survival pathways.…”

Reactive Oxygen Generated by NADPH Oxidase 1 (Nox1) Contributes to Cell Invasion by Regulating Matrix Metalloprotease-9 Production and Cell Migration

“…Rabbit anti-Nox1 antibodies were used as described previously (4). pSilencer-human Nox1 siRNAs were constructed as described previously (4).…”

“…Overproduction of intracellular ROS has been considered as a risk factor in cancer development. In this context it should be noted that aberrant activation of the Nox activity benefits transformation phenotypes of a subset of cancer cells (2); that is, Nox1 in Rastransformed cells (3), Nox4 in pancreatic cancer (4) and melanoma cells (5), and Nox5 in esophageal adenocarcinoma cells (6). With regard to Nox1, Ras oncogene up-regulated the Nox1 expression by activating GATA-6 through mitogen-activated extracellular signal-regulated kinase (MEK)-extracellular signal-regulated kinase (ERK)-dependent phosphorylation (7).…”