The metastasis suppressor SOX11 is an independent prognostic factor for improved survival in gastric cancer

Abstract

SOX11 is involved in gastrulation and in malignant diseases. The aim of this study was to investigate the role of SOX11 in gastric cancer and its expression pattern and clinical significance. SOX11 overexpression cell model was used to examine in vitro and in vivo the role of SOX11 in cell growth and metastasis. Cell cycle analysis and Annexin V/PI double staining were used to investigate the effect of SOX11 on cell cycle progression and apoptosis. The expression of SOX11 in human gastric cancer was examined by immunohistochemistry. The correlation of SOX11 expression with clinicopathological characteristics and survival of patients was analyzed by Pearson's χ(2) and Kaplan-Meier analyses, respectively. Cox's proportional hazard model was employed in multivariate analysis. SOX11 overexpression did not inhibit cell growth but strongly suppressed cell migration/invasion in vitro and in vivo. We found a significant correlation between high SOX11 protein levels and Lauren's classification (intestinal type), differentiation status (high and medium), and early TNM stage. SOX11 is an independent prognostic factor for improved survival in gastric cancer patients. SOX11 was a potential tumor-suppressor and an independent positive prognostic factor in gastric cancer patients with less advanced clinicopathological features.

Figure 1.

Expression of SOX11 mRNA levels in human gastric cancers using the Oncomine database. Analysis of SOX11 mRNA levels in human gastric cancer tissues compared with gastric normal tissues. The mRNA levels of SOX11 in human gastric cancers and normal gastric tissues in Cho (A), Wang (B) and D’Errico (C) datasets from the Oncomine database are shown. (D) Analysis of SOX11 mRNA levels in gastric cancer tissues with Lauren’s classification. D’Errico and Ooi datasets from the Oncomine database are shown.

Figure 2.

Expression of SOX11 in gastric cancer cell lines. (A) SOX11 mRNA and protein levels in ten gastric cancer cell lines and immortalized normal gastric epithelial cell line GES-1. Data represent mean ± SD of three independent experiments in column plot. (B) Immunoblotting analysis of SOX11 levels in SOX11-overexpressing and vector control cells using whole cell, cytoplasm and nuclear fraction. GAPDH was used as a loading control for whole and cytoplasm extracts. Histone H3 was used as a loading for nuclear extract. (C) Immunofluorescence staining of SOX11 in SOX11-overexpressing and vector-control cells. Bar, 200 μm.

Figure 3.

SOX11 overexpression did not affect gastric cancer cell growth in vitro and in vivo. Overexpression of SOX11 in SGC-7901 gastric cancer cells did not inhibit growth under monolayer (A) or in soft agar/Matrigel culture (B). (C) Cell cycle and apoptosis analysis using SOX11-overexpressing and vector-only SGC-7901 cells. (D) Growth curves of tumors after injection of control and SOX11-overexpressing SGC-7901 cells in nude mice. Data are shown as the mean ± SD (n=8). Representative images show tumors at the day of scarifice. Immunohistochemistry staining was used to examine the SOX11 expression in tumors from SOX11-overexpressing and vector-only SGC-7901 cells.

Figure 4.

SOX11 overexpression suppressed gastric cancer cell metastasis in vitro and in vivo. (A) SOX11 overexpression suppressed SGC-7901 cell migration and invasion. Representative images of migrated/invaded cells are shown (left, original magnification, ×200). Number of migrated/invaded cells is plotted (right). (B) Effects of SOX11 overexpression on suppressing peritoneal spreading and metastasis. Metastatic nodules are obvious in the control group. The numbers (mean ± SD) of metastatic nodules in control and SOX11-overexpression group are plotted (n=10).

Figure 5.

Survival analysis of SOX11 in gastric cancer. Kaplan-Meier analysis and the log-rank test identified SOX11 as significantly associated with cancer specific survival in high grade tumors.

Figure 6.

Survival analysis of SOX11 in gastric cancer stratified by stage. (A) Kaplan-Meier survival curves in gastric patients stratified by AJCC staging. (B) Kaplan-Meier survival curves in gastric patients stratified by N stage. (C) Kaplan-Meier survival curves in gastric patients stratified by T stage. The patients were classified into two groups based on SOX11 expression.