SPAG5 upregulation predicts poor prognosis in cervical cancer patients and alters sensitivity to taxol treatment via the mTOR signaling pathway

L-J Yuan,M Zheng,J-P Yun,J-H Wang,R-Z Luo,Y Zhou,W-H Jia,T Wan,H Tu,L Zhang,J-D Li

doi:10.1038/cddis.2014.222

Abstract

Previously, we found that sperm-associated antigen 5 (SPAG5) was upregulated in pelvic lymph node metastasis–positive cervical cancer. The aim of this study is to examine the role of SPAG5 in the proliferation and tumorigenicity of cervical cancer and its clinical significance in tumor progression. In our study, SPAG5 expression in cervical cancer patients was detected using quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry; cervical cancer cell function with downregulated SPAG5 in vitro was explored using tetrazolium assay, flow cytometry, and colony formation and Transwell assays. SPAG5 was upregulated in tumor tissue compared with paired adjacent noncancerous tissues; SPAG5 upregulation in tumor tissues indicated poor disease-free survival, which was also an independent prognostic indicator for cervical cancer patients. In vitro study demonstrated that SPAG5 downregulation inhibited cell proliferation and growth significantly by G2/M arrest and induction of apoptosis, and hindered cell migration and invasion. Under SPAG5 downregulation, the sensitivity of cervical cancer cells differed according to taxol dose, which correlated with mammalian target of rapamycin (mTOR) signaling pathway activity. In general, SPAG5 upregulation relates to poor prognosis in cervical cancer patients, and SPAG5 is a regulator of mTOR activity during taxol treatment in cervical cancer.

Highlights

Cervical cancer ranks the third frequently diagnosed cancer in women worldwide
To gain insight into the clinical roles and biological functions of SPAG5, we investigated its expression in cervical cancer specimens using quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry (IHC), and the effects of SPAG5-targeting small interfering RNA on cervical cancer cell line behaviors by 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide (MTT) assay, flow cytometry, colony formation assay, and Transwell assay
Via gene profiling using a customized oligonucleotide microarray, we previously reported that SPAG5 was upregulated in Pelvic lymph node metastasis (PLNM)-positive cervical cancer tissues compared with PLNM-negative tissues.[2]

Summary

Introduction

Cervical cancer ranks the third frequently diagnosed cancer in women worldwide. the morbidity rate has declined slightly over the past decade, cervical cancer remains the second most frequent cause of cancer-related death in women in developing countries.[1]. SPAG5 is upregulated in M-phase cells and binds to microtubules as a regulator of the timing of spindle organization and separation of sister chromatids.[3,5] the specific SPAG5 mechanisms involved in cell cycle regulation are unclear, several cell cyclerelated proteins, for example, p29, Aurora-A, and SNM1B, bind to SPAG5 and have a role in DNA damage recovery.[4,6,7]. The localization of SPAG5 to the centrosome is vital to its function.[8] It has been demonstrated that SPAG5 can be phosphorylated by glycogen synthase kinase-3b and polo-like kinase 1, which are important for SPAG5 activity.[9,10,11,12]

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