Phosphorylated Heat Shock Protein 20 (HSPB6) Regulates Transforming Growth Factor-α-Induced Migration and Invasion of Hepatocellular Carcinoma Cells

Rie Matsushima-Nishiwaki,Osamu Kozawa,Hidenori Toyoda,Eisuke Yasuda,Seiji Okuda,Tomoaki Nagasawa,Atsuyuki Maeda,Naokazu Chiba,Takashi Kumada,Yuji Kaneoka,Xin-Yuan Guan

doi:10.1371/journal.pone.0151907

Rie Matsushima-Nishiwaki, Osamu Kozawa + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0151907

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Abstract

Human hepatocellular carcinoma (HCC) is one of the major malignancies in the world. Small heat shock proteins (HSPs) are reported to play an important role in the regulation of a variety of cancer cell functions, and the functions of small HSPs are regulated by post-translational modifications such as phosphorylation. We previously reported that protein levels of a small HSP, HSP20 (HSPB6), decrease in vascular invasion positive HCC compared with those in the negative vascular invasion. Therefore, in the present study, we investigated whether HSP20 is implicated in HCC cell migration and the invasion using human HCC-derived HuH7 cells. The transforming growth factor (TGF)-α-induced migration and invasion were suppressed in the wild-type-HSP20 overexpressed cells in which phosphorylated HSP20 was detected. Phospho-mimic-HSP20 overexpression reduced the migration and invasion compared with unphosphorylated HSP20 overexpression. Dibutyryl cAMP, which enhanced the phosphorylation of wild-type-HSP20, significantly reduced the TGF-α-induced cell migration of wild-type HSP20 overexpressed cells. The TGF-α-induced cell migration was inhibited by SP600125, a c-Jun N-terminal kinases (JNK) inhibitor. In phospho-mimic-HSP20 overexpressed HuH7 cells, TGF-α-stimulated JNK phosphorylation was suppressed compared with the unphosphorylated HSP20 overexpressed cells. Moreover, the level of phospho-HSP20 protein in human HCC tissues was significantly correlated with tumor invasion. Taken together, our findings strongly suggest that phosphorylated HSP20 inhibits TGF-α-induced HCC cell migration and invasion via suppression of the JNK signaling pathway.

Highlights

The hepatocellular carcinoma (HCC) is one of the major malignancies in the world, and the third cause of cancer-related death [1,2]
The HSP20 protein expressed in the tumor tissues of human HCC, we previously showed that the HSP20 protein does not express in the HCC cell lines [20,23,24]
We previously demonstrated that the levels of HSP20 in human HCC are inversely correlated with the presence of microvascular invasion [20]

Summary

Introduction

The hepatocellular carcinoma (HCC) is one of the major malignancies in the world, and the third cause of cancer-related death [1,2]. Chronic hepatitis C in combination with alcohol abuse is the primary risk factor of HCC, and NASH is recently emerged as a relevant risk factor in developed countries [1,2]. The five-year survival rate of HCC is 30–40%, and recurrence and metastasis frequently occurs even after surgical resection [3]. Circulating HCC cells are recognized as the cause for recurrence, invasiveness, and metastasis [7,8,9]. Accumulating evidence indicates that transforming growth factor (TGF)-α is implicated in migration and invasion of cancer cells including HCC [10,11,12]. It has been shown that the intracellular signaling of TGF-α through activation of epidermal growth factor (EGFR), a receptor for TGF-α, enhances the movement of HCC cells [12]. The exact mechanism behind TGF-α-effects on HCC metastasis remains to be clarified

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