Hyperthermia-Induced NDRG2 Upregulation Inhibits the Invasion of Human Hepatocellular Carcinoma via Suppressing ERK1/2 Signaling Pathway

Yan Guo,Ji Ma,Libo Yao,Jing Zhang,Xia Li,Qianrong Wang,Jian Zhang,Yuan Zhang,Lin Wu,Wenchao Liu,Xiaoming Li,Xin-Yuan Guan

doi:10.1371/journal.pone.0061079

Yan Guo, Ji Ma + Show 10 more

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https://doi.org/10.1371/journal.pone.0061079

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Journal: PloS one	Publication Date: Apr 22, 2013
Citations: 23	License type: CC BY 4.0

Affiliation: Xijing Hospital, Air Force Medical University

Abstract

Hyperthermia (HT) has been proven to be able to alter the invasion capacity of cancer cells. However, the detailed mechanisms responsible for the anti-metastasis effects of HT have not been elucidated. N-myc downstream-regulated gene 2 (NDRG2), as a member of the NDRG family, has been suggested to be highly responsive to various stresses and is associated with tumor suppression. The present study aimed to investigate the biological role of NDRG2 in the invasion of human hepatocellular carcinoma (HCC) cells exposed to HT. We found that NDRG2 could be induced by HT at 45°C. In addition, NDRG2 overexpression inhibited the expression of matrix metallo proteinases-2 (MMP-2) and MMP-9 as well as the invasion of HCC cells, whereas knockingdown NDRG2 reversed the anti-invasion effect of HT in vivo. Further investigation revealed that the phosphorylation level of ERK1/2, but not that of JNK and p38MAPK, was reduced in NDRG2 overexpressing cells. Moreover, the knockdown of NDRG2 expression resulted in increased cell invasion, which was rescued by treating the HepG2 cells with the ERK1/2 inhibitor PD98059, but not with the p38MAPK inhibitor SB203580 or the JNK inhibitor SP600125. Finally, the synergistic cooperation of HT at 43°C and NDRG2 expression effectively reduced cytotoxicity and promoted the anti-invasion effect of HT at 45°C. Taken together, these data suggest that NDRG2 can be induced by HT and that it mediates the HT-caused inhibition of invasion in HCC cells by suppressing the ERK1/2 signaling pathway. The combined application of constitutive NDRG2 expression with HT may yield an optimized therapeutic benefit.

Highlights

Hepatocellular carcinoma (HCC) is one of the most frequent malignancies worldwide, accounting for 85% to 90% of primary liver cancers [1,2]
To further confirm the anti-invasion effect of HT, we examined the expression of matrix metallo proteinases-2 (MMP-2) and MMP-9 in both HCC cell lines
Western blot showed that the expression of N-myc downstream-regulated gene 2 (NDRG2) was increased by heat shock at 45uC in both HepG2 and Huh7 cells, which was negatively correlated with the down-regulation of MMP-2 and MMP-9

Summary

Introduction

Hepatocellular carcinoma (HCC) is one of the most frequent malignancies worldwide, accounting for 85% to 90% of primary liver cancers [1,2]. The inhibition of invasion and metastasis has been the key factor for the successful treatment of HCC. Hyperthermia, a minimally invasive treatment with few side effects, has recently been used for cancer therapy. A number of clinical and animal experiments have shown that HT exerts therapeutic effects by delaying tumor growth and by inhibiting lymph node metastasis [5,6,7]. In vitro research has been carried out to understand the underlying mechanism for this effect. Most of these investigations have focused altering metastasis-related genes, such as vascular endothelial growth factor (VEGF) [9], urokinase type plasminogen activator receptor (uPAR) [10] and MMPs [11,12]. Some progress has been made in terms of assessing the biological effect of HT, the molecular mechanism that mediates the anti-metastatic effect of HT has not been elucidated

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