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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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 7

TM4SF5-mediated cytosolic p27Kip1 and EMT caused loss of contact inhibition.

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TM4SF5-mediated cytosolic p27Kip1 and EMT caused loss of contact inhibit...
(A) Confluent SNU449Cp and SNU449Tp cells on coverslips under normal serum–containing condition were stained with DAPI. Arrows indicate cells in the middle of cell division; arrowheads indicate nuclei overlapped, indicating pile-up of dividing SNU449Tp cells even at confluent conditions. Growth rates of SNU449Cp and SNU449Tp cells were measured by counting viable cells. Each time point represents mean ± SD of an experiment performed in triplicate. (B) Subconfluent SNU449Cp and SNU449Tp cells as in A were double-stained for DNA and actin and visualized by a confocal microscope. Arrows indicate superimposed nuclei in the middle of cell division even in a subconfluent condition. S-phase populations of SNU449Cp and diverse TM4SF5-expressing cell lines (T7, T16, and T3) (C) or SNU449Cp and SNU449Tp cells transfected with scrambled or shTM4SF5 (D) were stained with propidium iodide before DNA content analyses using flow cytometry. SNU449Cp and SNU449Tp cells (E), SNU449Tp cells infected with scrambled (Ad-Scr) or p27Kip1 (Ad-sip27Kip1) siRNA adenovirus (F), or SNU449T16 cells reconstituted without (SNU449T16) or with E-cadherin (SNU449T16m) (G) were analyzed for S-phase progression via BrdU incorporation assay. Values in graphs represent mean ± SD. Original magnification, ×400. (H) Confluent SNU449T16 (T16) and SNU449T16m (T16m) cells on coverslips were immunostained. Data represent 3 independent experiments. Scale bars: 20 μm.