Tetraspanin TM4SF5 mediates loss of contact inhibition through epithelial-mesenchymal transition in human hepatocarcinoma
Sin-Ae Lee, … , Ki Hun Park, Jung Weon Lee
Sin-Ae Lee, … , Ki Hun Park, Jung Weon Lee
Published March 20, 2008
Citation Information: J Clin Invest. 2008;118(4):1354-1366. https://doi.org/10.1172/JCI33768.
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Research Article

Tetraspanin TM4SF5 mediates loss of contact inhibition through epithelial-mesenchymal transition in human hepatocarcinoma

Abstract

The growth of normal cells is arrested when they come in contact with each other, a process known as contact inhibition. Contact inhibition is lost during tumorigenesis, resulting in uncontrolled cell growth. Here, we investigated the role of the tetraspanin transmembrane 4 superfamily member 5 (TM4SF5) in contact inhibition and tumorigenesis. We found that TM4SF5 was overexpressed in human hepatocarcinoma tissue. TM4SF5 expression in clinical samples and in human hepatocellular carcinoma cell lines correlated with enhanced p27Kip1 expression and cytosolic stabilization as well as morphological elongation mediated by RhoA inactivation. These TM4SF5-mediated effects resulted in epithelial-mesenchymal transition (EMT) via loss of E-cadherin expression. The consequence of this was aberrant cell growth, as assessed by S-phase transition in confluent conditions, anchorage-independent growth, and tumor formation in nude mice. The TM4SF5-mediated effects were abolished by suppressing the expression of either TM4SF5 or cytosolic p27Kip1, as well as by reconstituting the expression of E-cadherin. Our observations have revealed a role for TM4SF5 in causing uncontrolled growth of human hepatocarcinoma cells through EMT.

Authors

Sin-Ae Lee, Sung-Yul Lee, Ik-Hyun Cho, Min-A Oh, Eun-Sil Kang, Yong-Bae Kim, Woo Duck Seo, Suyong Choi, Ju-Ock Nam, Mimi Tamamori-Adachi, Shigetaka Kitajima, Sang-Kyu Ye, Semi Kim, Yoon-Jin Hwang, In-San Kim, Ki Hun Park, Jung Weon Lee

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Figure 4

Effects of TM4SF5 suppression on cellular morphology and cytosolic p27Kip1 stabilization.

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Effects of TM4SF5 suppression on cellular morphology and cytosolic p27Ki...
(A) SNU449Tp cells were cotransfected with pEGFP and shTM4SF5. After 24 hours, cells were replated on coverslips for an additional 24 hours. Cells were then double-stained for p27Kip1 and DAPI. (B) Lysates prepared in Figure 2B were immunoblotted. (C) Huh7, SNU601, and HepG2 cells with endogenous TM4SF5 were transiently transfected with scrambled or shTM4SF5, 48 hours before immunoblots. SNU449Cp and SNU449Tp cells were blotted in parallel for comparison of TM4SF5 expression. (D) Huh7 cells with endogenous TM4SF5 were transiently cotransfected with pEGFP and scrambled sequence or shTM4SF5, 48 hours before immunoblot analysis or immunostaining. Note that shTM4SF5-transfected cells have a lower cytosolic p27Kip1 level, leading to a lower ratio of cytosolic to nucleic p27Kip1 levels. (E) Huh7 cells stably transfected with shTM4SF5 (Huh7-shTM4SF5, Figure 2J) were transiently cotransfected with pEGFP and pcDNA3-TM4SF5. Two days later, the cells were immunostained for p27Kip1 and DAPI. Original magnification, ×400. Data shown represent 3 isolated experiments. Scale bars: 20 μm.