SEPT9_i1 regulates human breast cancer cell motility through cytoskeletal and RhoA/FAK signaling pathway regulation

Yongqiu Zeng,Ting Zhang,Lifan Xiao,Yang Cao,Hong Yu,Qiang Tian,Lan Liu,Shaokun Chen,Jiao Zhao,Yansen Cai,Man Jia

doi:10.1038/s41419-019-1947-9

Yongqiu Zeng, Ting Zhang + Show 9 more

Open Access

https://doi.org/10.1038/s41419-019-1947-9

Copy DOI

Abstract

Increasing cell mobility is the basis of tumor invasion and metastasis, and is therefore a therapeutic target for preventing the spread of many types of cancer. Septins are a family of cytoskeletal proteins with GTPase activity, and play a role in many important cellular functions, including cell migration. SEPT9 isoform 1 protein (SEPT9_i1) has been associated with breast tumor development and the enhancement of cell migration; however, the exact mechanism of how SEPT9_i1 might affect breast cancer progression remains to be elucidated. Here, we report that the expression of SEPT9_i1 positively correlated with paxillin, and both were significantly upregulated in invasive breast cancer tissues of patients with lymph node metastases. Lentivirus-mediated shRNA knockdown of SEPT9 in MCF-7 cells diminished tumor cell migration, focal adhesion (FA) maturation and the expression of β-actin, β-tubulin, Cdc42, RhoA, and Rac, whereas overexpression of SEPT9_i1 in SEPT9-knockdown MCF-7 cells promoted cell migration, FA maturation and relevant protein expression. Furthermore, overexpression of SEPT9_i1 in MCF-7 cells markedly increased FAK/Src/paxillin signaling, at least in part through RhoA/ROCK1 upstream activation. Transcriptome profiling suggested that SEPT9_i1 may directly affect “Focal adhesion” and “Regulation of actin cytoskeleton” signaling mechanisms. Finally, overexpression of SEPT9_i1 markedly enhanced lung metastases in vivo 6 weeks after tumor inoculation. These findings suggest that a mechanism of Septin-9-induced aberrant cancer cell migration is through cytoskeletal regulation and FA modulation, and encourages the use of SEPT9 as novel therapeutic target in the prevention of tumor metastasis.

Highlights

Distant metastasis of a primary tumor is the major cause of mortality in patients with breast cancer[1]
Our results showed that SEPT9 and paxillin were overexpressed in 74.5% (41/55) and 54.5% (30/55) of the primary breast cancer clinical samples, respectively (Table 1)
The expression levels of SEPT9 and paxillin were significantly increased in the lymph node metastasis group compared to the non-lymph node metastasis group (Fig. 1), and SEPT9 expression was positively correlated with lymph node metastasis (γ = 0.367, P = 0.006)

Summary

Introduction

Distant metastasis of a primary tumor is the major cause of mortality in patients with breast cancer[1]. Zeng et al Cell Death and Disease (2019)10:720 key residues determine protein recruitment, subcellular localization, and catalytic activity of FAK5. FAK can regulate cytoskeletal dynamics and cell motility by influencing actin polymerization and FA turnover[6,7]. Studies have shown that increased FAK expression and activity in many cancers is often associated with metastasis and poor clinical outcome, highlighting FAK as a potential determinant of tumor development and cancer progression[8,9]. SEPT9, one of the 13 members of septins, located at the Chr. 17q25 locus and is directly implicated in actin dynamics, angiogenesis, bacterial autophagy, cell motility, cell proliferation, cell shape, cytokinesis, microtubule regulation, vesicle targeting, and exocytosis[11,12,13,14,15]. SEPT9_i1, one of the largest isoforms, has already been involved in ovarian cancer[18], head and neck cancers[19], and breast cancer progression[14,20]

Methods

Results

Conclusion