SOX2 inhibits metastasis in gastric cancer

Abstract

Purpose: To investigate the potential role of SOX2 in gastric cancer (GC) metastasis.

Methods: The SOX2 expression was detected using immunohistochemistry on a GC tissue microarray. The correlations of SOX2 expression with clinicopathological factors and 5-year survival were evaluated. To test the role of SOX2 in inhibiting GC metastasis, the cell transwell assay was performed. Real-time PCR and Western blot were used to explore the possible mechanism that SOX2 inhibits GC metastasis.

Results: In the present study, SOX2 expression was downregulated in GC tissues when compared to matching normal tissues. Moreover, patients with high SOX2 expression in cancerous tissues had less lymph node metastasis and better treatment outcome. At the subcellular level, SOX2 inhibited the GC cell migration and invasion by upregulating p21 expression. Moreover, SOX2 was determined to associate with the nuclear p21 expression. GC patients with high SOX2 and nuclear p21 expression had synergistically less lymph node metastasis and the better overall survival.

Conclusion: Our results suggest that SOX2 is a promising and favorable metastatic biomarker for GC.

Keywords: Gastric cancer; Metastasis; Prognosis; SOX2; p21.

Fig. 1

SOX2 expression is reduced in GC. The expression of SOX2 in GC tissues and the paired normal gastric tissues was detected by Western blot (a) and real-time PCR (b), respectively. Representative images of SOX2 IHC staining in TMA (c). Note top panel, ×100 magnification; below panel, ×200 magnification. The distribution of SOX2 staining in GC relative to that in paired normal tissues (d). Note GC, gastric cancer; N, normal gastric tissues; C, GC cancer tissues; *P < 0.05, **P < 0.001

Fig. 2

SOX2 is significantly associated with GC metastasis and prognosis. The GC patients with low SOX2 expression have a higher frequency of lymph node metastasis than those with high SOX2 expression (a). Kaplan–Meier curves show that GC patients with low SOX2 have a worse 5-year survival than those with high expression (b). Note *P < 0.05, **P < 0.001

Fig. 3

SOX2 overexpression reduces cell migration and invasion in GC cells in vitro. Real-time PCR and Western blot were used to test whether SOX2 is overexpressed in the BCG823 and AGS cells, respectively (a, b). Representative migration and invasion images of BGC823 and AGS cells with different SOX2 expression levels, and the relative ratios of GC cell migration and invasion were counted in five random fields (n = 3/group) (c, d). All data are expressed as the mean ± SD, *P < 0.05, **P < 0.001; Student’s t test. Note CON, pcDNA3.3-control; SOX2, pcDNA3.3-SOX2

Fig. 4

SOX2 suppresses GC migration and invasion by upregulating p21 expression. SOX2 regulates p21 mRNA and protein expressions in the BCG823 and AGS cells, respectively (a, b). Western blot was used to validate the expression levels of SOX2 and p21 after the AGS cells overexpressed SOX2, while p21 was knocked down (c). The representative migration and invasion images of AGS cells after SOX2 was overexpressed and p21 was knocked down (c); the relative ratios of AGS cell migration and invasion were counted in five random fields (n = 3/group) (d). Data are expressed as the mean ± SD, *P < 0.05, **P < 0.001; Student’s t test. Note CON, pcDNA3.3-control; SOX2, pcDNA3.3-SOX2

Fig. 5

Combination of SOX2 and nuclear p21 expression as a more effective biomarker for GC lymph node metastasis and the 5-year survival of GC patients. In GC TMA, SOX2 is positively associated with nuclear p21 expression (a). The groups with low SOX2 and low nuclear p21 expression show the highest frequency for lymph node metastasis (b). Kaplan–Meier curves show that the GC patients with low SOX2 and low nuclear p21 expression have the worst 5-year survival rate (c). Note *P < 0.05, **P < 0.001