Expression of sushi domain containing two reflects the malignant potential of gastric cancer

Abstract

Hepatic recurrence of gastric cancer (GC) is uncontrollable. Discovery of causative oncogenes and the development of sensitive biomarkers to predict hepatic recurrence are required to improve patients' outcomes. In this study, recurrence pattern-specific transcriptome analysis of 57 749 genes was conducted to identify mRNAs specifically associated with hepatic metastasis of patients with stage III GC who underwent curative resection. GC cell lines were subjected to mRNA expression analysis, PCR array analysis, and siRNA-mediated knockdown. The expression levels of primary cancer tissues from 154 patients with resectable GC were determined and correlated with clinicopathological variables. Among 21 genes significantly overexpressed specifically in patients with hepatic recurrence, Sushi domain containing 2 (SUSD2) was selected as a promising target. PCR array analysis revealed that SUSD2 mRNA levels positively correlated with those of FZD7, CDH2, TGFB1, SPARC, ITGA5, and ZEB1. Functional analysis revealed that knockdown of SUSD2 significantly reduced the proliferation, migration, and invasiveness GC cell lines. Patients with high SUSD2 expression were more likely to experience shorter disease-free and overall survival. Analysis of the relation between disease recurrence pattern and SUSD2 levels revealed that significantly more patients with hepatic metastases expressed higher levels of SUSD2 mRNA. The cumulative incidence of hepatic recurrence was greater in patients with high SUSD2 expression. In conclusion, SUSD2 likely contributes to the malignant potential of GC and may serve as a novel biomarker that predicts hepatic recurrence after curative resection.

Keywords: SUSD2; expression; gastric cancer; hepatic recurrence; prognosis.

Figure 1

Analysis of SUSD2 mRNA levels of gastric cancer (GC) cell lines, cancer‐related genes expressed cooperatively with SUSD2, and knockdown efficacy. A, SUSD2 mRNA levels in GC cell lines. B, SUSD2 mRNA and mRNAs of genes expressed at similar differential levels were identified using PCR array analysis. Spearman's rank correlation coefficient between the mRNA expression levels of SUSD2 and those of FZD7, CDH2, TGFB1, SPARC, ITGA5, and ZEB1 are shown. C, siRNA‐mediated SUSD2‐knockdown efficacy in MKN1 and AGS cell lines was determined using qRT‐PCR analysis. D, SUSD2‐knockdown efficacy was also determined using Western blotting analysis

Figure 2

Cell proliferation and invasion assays. A, Cell proliferation assay. Inhibition of SUSD2 expression significantly decreased the proliferation of MKN1and AGS cells. *P < 0.05. B, Cell invasion assays. The number of invading cells was significantly lower in cells transfected with the SUSD2‐siRNA

Figure 3

Cell migration assay. The migration of MKN1 and AGS cells transfected with the SUSD2‐sRNA was significantly decreased vs control cells. *P < 0.05

Figure 4

Prognostic implications of SUSD2 mRNA expression in patients with GC after curative resection. A, Kaplan‐Meyer analysis of disease‐free survival and overall survival. B, Kaplan‐Meyer analysis of disease‐free survival and overall survival of patients in the external‐validation cohort

Figure 5

Analysis of recurrence patterns. A, Numbers of sites of initial recurrence in the high and low expression groups. B, Cumulative incidence of hepatic and peritoneal recurrence