Theranostics 2021; 11(3):996-1015. doi:10.7150/thno.51646 This issue Cite

Research Paper

The 14-3-3σ protein promotes HCC anoikis resistance by inhibiting EGFR degradation and thereby activating the EGFR-dependent ERK1/2 signaling pathway

Jia Song*, Yachong Liu*, Furong Liu, Lu Zhang, Ganxun Li, Chaoyi Yuan, Chengpeng Yu, Xun Lu, Qiumeng Liu, Xiaoping Chen, Huifang Liang, Zeyang Ding, Bixiang Zhang

Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Clinical Medicine Research Center for Hepatic Surgery of Hubei Province, Key Laboratory of Organ Transplantation, Ministry of Education, NHC Key Laboratory of Organ Transplantation, Key Laboratory of Organ Transplantation, Chinese Academy of Medical Sciences, Wuhan, Hubei 430030, People's Republic of China.
*These authors contributed equally to this work.

Citation:
Song J, Liu Y, Liu F, Zhang L, Li G, Yuan C, Yu C, Lu X, Liu Q, Chen X, Liang H, Ding Z, Zhang B. The 14-3-3σ protein promotes HCC anoikis resistance by inhibiting EGFR degradation and thereby activating the EGFR-dependent ERK1/2 signaling pathway. Theranostics 2021; 11(3):996-1015. doi:10.7150/thno.51646. https://www.thno.org/v11p0996.htm
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Abstract

Graphic abstract

Resistance to anoikis, cell death due to matrix detachment, is acquired during tumor progression. The 14-3-3σ protein is implicated in the development of chemo- and radiation resistance, indicating a poor prognosis in multiple human cancers. However, its function in anoikis resistance and metastasis in hepatocellular carcinoma (HCC) is currently unknown.

Methods: Protein expression levels of 14-3-3σ were measured in paired HCC and normal tissue samples using western blot and immunohistochemical (IHC) staining. Statistical analysis was performed to evaluate the clinical correlation between 14-3-3σ expression, clinicopathological features, and overall survival. Artificial modulation of 14-3-3σ (downregulation and overexpression) was performed to explore the role of 14-3-3σ in HCC anoikis resistance and tumor metastasis in vitro and in vivo. Association of 14-3-3σ with epidermal growth factor receptor (EGFR) was assayed by co-immunoprecipitation. Effects of ectopic 14-3-3σ expression or knockdown on EGFR signaling, ligand-induced EGFR degradation and ubiquitination were examined using immunoblotting and co-immunoprecipitation, immunofluorescence staining, and flow cytometry analysis. The levels of EGFR ubiquitination, the interaction between EGFR and 14-3-3σ, and the association of EGFR with c-Cbl after EGF stimulation, in 14-3-3σ overexpressing or knockdown cells were examined to elucidate the mechanism by which 14-3-3σ inhibits EGFR degradation. Using gain-of-function or loss-of-function strategies, we further investigated the role of the EGFR signaling pathway and its downstream target machinery in 14-3-3σ-mediated anoikis resistance of HCC cells.

Results: We demonstrated that 14-3-3σ was upregulated in HCC tissues, whereby its overexpression was correlated with aggressive clinicopathological features and a poor prognosis. In vitro and in vivo experiments indicated that 14-3-3σ promoted anoikis resistance and metastasis of HCC cells. Mechanistically, we show that 14-3-3σ can interact with EGFR and significantly inhibit EGF-induced degradation of EGFR, stabilizing the activated receptor, and therefore prolong the activation of EGFR signaling. We demonstrated that 14-3-3σ downregulated ligand-induced EGFR degradation by inhibiting EGFR-c-Cbl association and subsequent c-Cbl-mediated EGFR ubiquitination. We further verified that activation of the ERK1/2 pathway was responsible for 14-3-3σ-mediated anoikis resistance of HCC cells. Moreover, EGFR inactivation could reverse the 14-3-3σ-mediated effects on ERK1/2 phosphorylation and anoikis resistance. Expression of 14-3-3σ and EGFR were found to be positively correlated in human HCC tissues.

Conclusions: Our results indicate that 14-3-3σ plays a pivotal role in the anoikis resistance and metastasis of HCC cells, presumably by inhibiting EGFR degradation and regulating the activation of the EGFR-dependent ERK1/2 pathway. To our best knowledge, this is the first report of the role of 14-3-3σ in the anoikis resistance of HCC cells, offering new research directions for the treatment of metastatic cancer by targeting 14-3-3σ.

Keywords: HCC, anoikis resistance, 14-3-3σ, EGFR, ERK1/2 pathway


Citation styles

APA
Song, J., Liu, Y., Liu, F., Zhang, L., Li, G., Yuan, C., Yu, C., Lu, X., Liu, Q., Chen, X., Liang, H., Ding, Z., Zhang, B. (2021). The 14-3-3σ protein promotes HCC anoikis resistance by inhibiting EGFR degradation and thereby activating the EGFR-dependent ERK1/2 signaling pathway. Theranostics, 11(3), 996-1015. https://doi.org/10.7150/thno.51646.

ACS
Song, J.; Liu, Y.; Liu, F.; Zhang, L.; Li, G.; Yuan, C.; Yu, C.; Lu, X.; Liu, Q.; Chen, X.; Liang, H.; Ding, Z.; Zhang, B. The 14-3-3σ protein promotes HCC anoikis resistance by inhibiting EGFR degradation and thereby activating the EGFR-dependent ERK1/2 signaling pathway. Theranostics 2021, 11 (3), 996-1015. DOI: 10.7150/thno.51646.

NLM
Song J, Liu Y, Liu F, Zhang L, Li G, Yuan C, Yu C, Lu X, Liu Q, Chen X, Liang H, Ding Z, Zhang B. The 14-3-3σ protein promotes HCC anoikis resistance by inhibiting EGFR degradation and thereby activating the EGFR-dependent ERK1/2 signaling pathway. Theranostics 2021; 11(3):996-1015. doi:10.7150/thno.51646. https://www.thno.org/v11p0996.htm

CSE
Song J, Liu Y, Liu F, Zhang L, Li G, Yuan C, Yu C, Lu X, Liu Q, Chen X, Liang H, Ding Z, Zhang B. 2021. The 14-3-3σ protein promotes HCC anoikis resistance by inhibiting EGFR degradation and thereby activating the EGFR-dependent ERK1/2 signaling pathway. Theranostics. 11(3):996-1015.

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