Overexpression of kinesin family member 20A is associated with unfavorable clinical outcome and tumor progression in epithelial ovarian cancer

Abstract

Background: KIF20A plays an indispensable role in cytokinesis regulation, which is important for tumor proliferation and growth. Recently, the oncogenic role of KIF20A has been well documented in several cancers. However, its clinical role in epithelial ovarian cancer (EOC) remains not reported yet. We investigated its expression and its role in promoting invasion and chemoresistance in EOC cells.

Patients and methods: KIF20A transcription and translation levels were investigated in normal ovarian epithelial cell, ovarian cancer cells, and 10 pairs of fresh EOC tissues and adjacent normal ovarian tissues by real-time quantitative polymerase chain reaction and Western blots. Moreover, KIF20A protein level was also examined by immunohistochemistry in 150 EOC tissues. The correlation between KIF20A expression and clinical variables was analyzed by statistical methods. We also used wound healing assay, transwell assay MTT, and Annexin V/PI to explore KIF20A functions.

Results: KIF20A expression was obviously elevated at both mRNA and protein levels in EOC cell lines and clinical cancer tissues compared with normal ovarian epithelial cell and adjacent normal ovarian tissues. KIF20A protein expression was highly correlated with International Federation of Gynecology and Obstetrics stage (P=0.008), lymph node metastasis (P=0.002), intraperitoneal metastasis (P<0.001), vital status at last follow-up (P<0.001), intraperitoneal recurrence (P=0.030), tumor recurrence (P=0.005), drug resistance (P=0.013), and ascites with tumor cells (P<0.001). KIF20A overexpression was closely related to poorer overall survival and disease progression-free survival. Furthermore, Cox regression analysis revealed that KIF20A can act as an independent hazard indicator for predicting clinical outcomes in EOC patients. Interestingly, KIF20A overexpression promoted invasion and metastasis of EOC cells and also confers resistance to cisplatin.

Conclusion: Our findings indicated that KIF20A overexpression predicts unfavorable clinical outcome, revealing that KIF20A holds a promising potential to serve as a useful prognostic biomarker for EOC patients.

Keywords: KIF20A; clinical prognosis; epithelial ovarian cancer; tumor progression.

Figure 1

KIF20A mRNA and protein were overexpressed in EOC cell lines. Notes: (A, B) Expression of KIF20A mRNA and protein in EOC cell lines (COV644, COV362, OV90, SKOV3, TOV112D, OVCAR4, A2780, COV434, TOV21G) and normal ovarian epithelial cell (HOSEpiC) by real-time PCR (A) and Western blotting (B). Expression levels were normalized to GAPDH expression. Error bars represent standard deviation (SD) of the mean calculated from three parallel experiments. ^*P<0.05. Abbreviations: EOC, epithelial ovarian cancer; PCR, polymerase chain reaction.

Figure 2

Overexpression of KIF20A mRNA and protein in EOC specimens. Notes: (A) The average T/ANT ratios of KIF20A mRNA expression in the ovarian cancer (T) and adjacent noncancerous tissue sections were quantified using real-time PCR and normalized against GAPDH. Error bars represent standard deviation (SD) of the mean calculated from three parallel experiments. (B, C) Western blotting analyses of KIF20A expression in ten pairs of ovarian cancer tissues (T) and ANT. GAPDH was used as the loading control. (D) Immunohistochemical detection of KIF20A protein in ten pairs of matched ovarian cancer tissues. ^*P<0.05. Abbreviations: ANT, adjacent noncancerous tissue; EOC, epithelial ovarian cancer; PCR, polymerase chain reaction.

Figure 3

KIF20A protein expression in paraffin-embedded tissues. Notes: (A) Representative images from immunohistochemical staining of KIF20A protein expression in ovarian cancer tissues at four clinical stages. (B) The average MOD of KIF20A staining in four clinical stages groups ^*P<0.05 (C). Representative images of KIF20A expression in recurrence group and nonrecurrence group. (D) The statistical analyses of the average MOD of KIF20A staining in the recurrence group and nonrecurrence group ^*P<0.05. Abbreviation: MOD, mean optical density.

Figure 4

Kaplan–Meier curves of univariate analysis data (log-rank test). Notes: Survival curves for the patients in select patient subgroups (log-rank test). The OS and DFS of the patients with low KIF20A expression vs high KIF20A expression (A, B). OS rates for patients with tumor recurrence (C), intraperitoneal recurrence (D), aged ≤53 years (E), aged >53 years (F), intestinal metastasis (G), ascites with tumor cells (H), CA125 >35 U/mL (I) at differentiation grades 1 and 2 (J), at differentiation grade 3 (K), without neoadjuvant chemotherapy (L), with neoadjuvant chemotherapy (M), postoperative chemotherapy (N), at stages 1, 2 (O), and at stages 3, 4 (P). Abbreviations: DFS, disease-free survival; OS, overall survival.

Figure 5

Upregulation of KIF20A enhances the invasive and metastatic abilities of EOC cells, while knockdown of KIF20A represses the invasive and metastatic abilities. Notes: (A–C) The invasive and metastatic abilities of EOC cells were assessed by transwell assay. Each bar represents the mean±SD of three parallel experiments. (D, E) Representative images of wound healing assay; mobility of cells was evaluated by wound closure (%) at 0, 12, 24 hours ^*P<0.05. Abbreviation: EOC, epithelial ovarian cancer.

Figure 6

KIF20A confers cisplatin resistance in EOC cells. Notes: (A, B) MTT/IC50 assay evaluates the viability of KIF20A-overexpressed and KIF20A-silenced EOC cells after cisplatin treatment for 48 hours. (C) Apoptosis assay analyzes the percentage of apoptosis cells for KIF20A-overexpressed and KIF20A-silenced EOC cells after cisplatin treatment (5 µM) for 24 hours ^*P<0.05. Abbreviation: EOC, epithelial ovarian cancer.