Antitumor Indolequinones Induced Apoptosis in Human Pancreatic Cancer Cells via Inhibition of Thioredoxin Reductase and Activation of Redox Signaling

Abstract

Indolequinones (IQs) were developed as potential antitumor agents against human pancreatic cancer. IQs exhibited potent antitumor activity against the human pancreatic cancer cell line MIA PaCa-2 with growth inhibitory IC 50 values in the low nanomolar range. IQs were found to induce time-and concentrationdependent apoptosis and to be potent inhibitors of thioredoxin reductase 1 (TR1) in MIA PaCa-2 cells at concentrations equivalent to those inducing growth-inhibitory effects. The mechanism of inhibition of TR1 by the IQs was studied in detail in cell-free systems using purified enzyme. The C-terminal selenocysteine of TR1 was characterized as the primary adduction site of the IQ-derived reactive iminium using liquid chromatography-tandem mass spectrometry analysis. Inhibition of TR1 by IQs in MIA PaCa-2 cells resulted in a shift of thioredoxin-1 redox state to the oxidized form and activation of the p38/c-Jun NH 2 -terminal kinase (JNK) mitogen-activated protein kinase (MAPK) signaling pathway. Oxidized thioredoxin is known to activate apoptosis signal-regulating kinase 1, an upstream activator of p38/JNK in the MAPK signaling cascade and this was confirmed in our study providing a potential mechanism for IQ-induced apoptosis. These data describe the redox and signaling events involved in the mechanism of growth inhibition induced by novel inhibitors of TR1 in human pancreatic cancer cells.

Thioredoxin-1/peroxiredoxin-1 as sensors of oxidative stress mediated by NADPH oxidase activity in atherosclerosis

“…In the intracellular compartment, TRX-1 was mainly present as nonfully oxidized forms in basal conditions. In this respect, there have been previous papers showing only the reduced form of TRX-1 in basal conditions [24,[42][43][44][45], while others also ͳͳ showed the two bands observed in the present paper [46,47]. Technical questions and/or culture conditions could account for these potential discrepancies since it has been demonstrated that proliferative status [48] or ion composition [49] could modify TRX-1 oxidative status.…”

Keap1–Nrf2 signalling in pancreatic cancer

“…Finally, the thioredoxin antioxidant system, which is also under Nrf2/ARE regulation, has an important role in maintaining redox state of thiols in cellular proteins (Arnér and Holmgren, 2006). Thioredoxin is overexpressed in human pancreatic cancer specimens and PDAC cell lines (Arnold et al, 2004;Yi and Oh, 2015), and reduced thioredoxin (through thioredoxin reductase) is known to promote proliferation, inhibit apoptosis, and protect cells from oxidative stress (Powis and Montfort, 2001;Arnold et al, 2004;Yan et al, 2012). In PDAC cell lines (i.e.…”

“…In PDAC cell lines (i.e. MiaPaca-2, Panc-1 and BxPC-3) treatment with selective thioredoxin reductase 1 (TrxR1) inhibitors induces apoptosis (Yan et al, 2012). To the best of our knowledge, no combination studies with TrxR1 inhibitors and standard chemotherapy agents have been reported using PDAC cell lines.…”

Antitumour indolequinones: synthesis and activity against human pancreatic cancer cells

“…18 Inhibition of thioredoxin reductase leads to oxidation of thioredoxin, dissociation of free ASK1, phosphorylation of JNK and p38 and subsequent apoptosis. 18 …”