FOXO/TXNIP pathway is involved in the suppression of hepatocellular carcinoma growth by glutamate antagonist MK-801

Abstract

BackgroundAccumulating evidence has suggested the importance of glutamate signaling in cancer growth, yet the signaling pathway has not been fully elucidated. N-methyl-D-aspartic acid (NMDA) receptor activates intracellular signaling pathways such as the extracellular-signal-regulated kinase (ERK) and forkhead box, class O (FOXO). Suppression of lung carcinoma growth by NMDA receptor antagonists via the ERK pathway has been reported. However, series of evidences suggested the importance of FOXO pathways for the regulation of normal and cancer cell growth. In the liver, FOXO1 play important roles for the cell proliferation such as hepatic stellate cells as well as liver metabolism. Our aim was to investigate the involvement of the FOXO pathway and the target genes in the growth inhibitory effects of NMDA receptor antagonist MK-801 in human hepatocellular carcinoma.MethodsExpression of NMDAR1 in cancer cell lines from different tissues was examined by Western blot. NMDA receptor subunits in HepG2, HuH-7, and HLF were examined by reverse transcriptase polymerase chain reaction (RT-PCR), and growth inhibition by MK-801 and NBQX was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The effects of MK-801 on the cell cycle were examined by flow cytometry and Western blot analysis. Expression of thioredoxin-interacting protein (TXNIP) and p27 was determined by real-time PCR and Western blotting. Activation of the FOXO pathway and TXNIP induction were examined by Western blotting, fluorescence microscopy, Chromatin immunoprecipitation (ChIP) assay, and reporter gene assay. The effects of TXNIP on growth inhibition were examined using the gene silencing technique.ResultsNMDA receptor subunits were expressed in all cell lines examined, and MK-801, but not NBQX, inhibited cell growth of hepatocellular carcinomas. Cell cycle analysis showed that MK-801 induced G1 cell cycle arrest by down-regulating cyclin D1 and up-regulating p27. MK-801 dephosphorylated Thr24 in FOXO1 and induced its nuclear translocation, thus increasing transcription of TXNIP, a tumor suppressor gene. Knock-down of TXNIP ameliorated the growth inhibitory effects of MK-801.ConclusionsOur results indicate that functional NMDA receptors are expressed in hepatocellular carcinomas and that the FOXO pathway is involved in the growth inhibitory effects of MK-801. This mechanism could be common in hepatocellular carcinomas examined, but other mechanisms such as ERK pathway could exist in other cancer cells as reported in lung carcinoma cells. Altered expression levels of FOXO target genes including cyclin D1 and p27 may contribute to the inhibition of G1/S cell cycle transition. Induction of the tumor suppressor gene TXNIP plays an important role in the growth inhibition by MK-801. Our report provides new evidence that FOXO-TXNIP pathway play a role in the inhibition of the hepatocellular carcinoma growth by MK-801.

Epigenetic bivalent marking is permissive to the synergy of HDAC and PARP inhibitors on TXNIP expression in breast cancer cells

“…By contrast, MDA468 cells were not responsive to the SAHA-PJ34 cocktail, both in terms of TXNIP expression and cell proliferation parameters. These findings are consistent with those of previous studies, in which a correlation between TXNIP expression increment, growth inhibition and induction of apoptosis has been shown (19,22). Moreover, Jasek et al have recently shown that the combined treatment of SAHA and PJ34 on leukemic cell lines has a synergistic effect on proliferation inhibition and an increase in apoptosis (28).…”

“…In various tumor tissues, the increase of TXNIP expression was correlated with growth inhibition and induction of apoptosis (19,22). Therefore, we examined whether such a correlation is present in our experimental system.…”

Fenofibrate suppressed proliferation and migration of human neuroblastoma cells via oxidative stress dependent of TXNIP upregulation

“…So, TXNIP is a negative regulator of intracellular ROS. Furthermore, TXNIP inhibits cell invasion and metastasis, and promotes cell apoptosis [23]. It has shown that TXNIP is a tumor suppressor in cancer [17].…”

The pleiotropic effects of fisetin and hesperetin on human acute promyelocytic leukemia cells are mediated through apoptosis, cell cycle arrest, and alterations in signaling networks

“…For instance, TXNIP or thioredoxin-interacting protein plays a crucial role in apoptosis. Its expression was found to be downregulated in many tumor cells [28], and overexpression of TXNIP inhibits cancer cell growth [29].…”