The Role Of SCIN In Self-renewal, Invasion And Metastasis Of Gastric Cancer Stem Cells

Gastric cancer(GC) is the most commen digesitive malignancy with high morbidity and motality, especially in East European, East Asia and South America. According to the tumor-related epidemiology, GC rises as the second leading cause of cancer-related deaths worldwide. Despite evolving novel therapy regimens in the surgery, chemotherapy and biotherapy, patients’ long-term survival rate is still poor. As the major cause of GC-associated mortality is related to invasion and metastasis, it is urgent to identify novel biomarkers predicting aggressive biological behaviour and clarify the undergoing mechanisms.Recently, the cancer stem cells(CSCs) hypothesis provides us a novel insigt into the generation and progression of gastric cancer. Our previous work have established the method to isolate and enrich gastric cancer stem cells(GCSCs) by using the serum-free sphere forming culture. The GCSCs exhibits a more aggressive phenotype, including the self-renewal, high invasion and metastasis, implying that GCSCs plays an important role in the progression of GC. According to the differential gene expression microarray analysis, we previously found that scinderin(SCIN), a protein related to cell morphology and movement, was particularly overexpressed in GSCSs than that in monolayer gastric cancer cells. Then the expression level and clinical significance of SCIN were determined in GC specimens, and the roles of SCIN in self-renewal, invasion and metastasis were explored in GC cell lines. Our work demonstrates that SCIN may be a novel biomarker of predicting poor overall survival, and could be developed as a new theraputic target for patients with GC.Main methods and results:1. The expression and clinical significance of SCIN in GC specimens.(1) One hundred and eighty-eight cases of GC specimens was enrolled in the immunochemistric study to determine the expression level and clinical value of SCIN. One hundred and five patients(56%, 105/188) were found to be SCIN highly expressed. Increased SCIN expression level was correlated with tumor invasive depth(P=0.011) and lymph node metastasis(P=0.024), but not with age(P=0.840), gender(P=0.220) and differentiation(P=0.483).(2) Kaplan-Meier analysis showed that patients with high SCIN expression owned worse outcome than those with low SCIN expression, implying that SCIN might be developed as a prognostic marker for patients with GC.2. Silence of SCIN expression inhibited the self-renewal of GCSCs.(1) The expression level of SCIN in GC cell lines MGC803、SGC7901 and primary cell XN0422 and GCSCs was detected by quantitative Real-time Polymerase Chain Reaction(q RT-PCR) and Western Blot. The MGC803 and primary GC cell XN0422, which presented with high SCIN expression than other cell lines and especially higher in GCSCs, were used to determine the function of SCIN with RNA interference technique.(2) Compared with the mock group, SCIN knockdown group showed impaired colony formation ability, sphere formation ability and tumor formation ability(All P<0.05).3. Silence of SCIN expression impaired the invasive and metastatic ability of gastric cancer cells.(1) asive and metastatic ability were detected by the Live cell Imaging System and transwell-matrigel assay respectively. The SCIN knockdown group possessed significant lower invasive and metastatic ability than the mock group(All P<0.05).(2) Xenograft model and peritoneal metastasis model were applied to detect the invasive and metastatic ability in vivo. Though the two groups both possessed the ability to form xenograft, lighter tumor weight and less tumor volumn were found in the SCIN knockdown group than that in the mock gourp. Moreover, the number of peritoneal metastatic tumor was much less in the SCIN knockdown group than that in the mock gourp(32.67 ± 4.74 vs 15.83 ± 2.00 in XN0422 and 19.67 ± 2.33 vs 10.00 ± 1.29 in MGC803, both P<0.05).Conclusions:The expression level of SCIN is negatively correlated with overall survival time, and can be used as an independent prognostic marker for patients with gastric cancer.Inhibition of SCIN expression impairs the self-renewal of GCSCs.Downregulation of SCIN inhibits the invasive and metastatic ability of gastric cancer cells.