Studies On Invasion And Metastasis Associated Functional Genes In Gastric Carcinoma

Gastric cancer is one of the most common solid tumors worldwide.There were approximate 900 thousand new increasing cases and 700 thousand death cases all over the world.China is one of the highest countries of gastric cancer's incidence and mortality.Gastric cancer is characterized by rapid clinical progression and poor prognosis due to adjacent tissue invasion and distant organs metastasis at a very early stage.Therefore,searching for and study on invasion and metastasis associated functional genes in gastric carcinoma is essential to develop effective treatment and longer the survival time of gastric cancer,at the same time,searching for invasion and metastasis related genes may help us get some biomarkers that are useful in predicting survival of patients and informing treatment decisions.To this end,we used the Transwell system to select two highly invasive subcell lines SNU5-P3 and PAMC82-P3 from minimally invasive parent cells,and compared gene expression in paired cell lines with high and low invasive potentials.38 genes were commonly upregulated in the two highly invasive subcell lines.By this screen, LOXL2 was identified as a candidate promoter for gastric carcinoma cell invasion and metastasis.Western blotting revealed that LOXL2 was overexpression in gastric carcinoma cell lines with high-invasive potential.Immunohistochemical analysis on tissue microarray showed LOXL2 was overexpressed in gastric cancer,and gradient upregulated in lymph node metastasis.The overexpressed LOXL2 was a valuable prognostic factor independent of lymph node metastasis or local invasion. RNAi-mediated knockdown and ectopic expression of LOXL2 showed that LOXL2 promoted tumor cell invasion in vitro and increased gastric carcinoma metastasis in vivo.Subsequent mechanistic studies showed that LOXL2 could activate both the Snail/E-cadherin and Src/FAK pathways.However,secreted LOXL2 induced gastric tumor cell invasion and metastasis exclusively via the Src/FAK pathway.Expression correlation analysis in gastric carcinoma tissues also revealed that LOXL2 promoted invasion via the Src/FAK pathway but not the Snail/E-cadherin pathway.We then evaluated secreted LOXL2 as a target for gastric carcinoma treatment,and found that an antibody against LOXL2 significantly inhibited tumor growth and metastasis. Overall,our data revealed that LOXL2 overexpression,a frequent event in gastric carcinoma progression,contributes to tumor cell invasion and metastasis,and LOXL2 may be a therapeutic target for preventing and treating metastases.Searching for invasion and metastasis related gene also is helpful to get some biomarkers that are useful in predicting survival of patients and informing treatment decisions.By gene microarray analysis,we also identified CAPG,S100A14, LGALS1,and IEX-1 were overexpressed in the highly invasive subcell lines. Immunohistochemical analysis on tissue microarray showed S100A14 and LGASL1 were overexpressed in gastric cancer,and those overexpression in primary tumor were significantly associated with depth of tumor invasion,lymph node metastasis,and poorer overall survival.Logistic regression revealed that S100A14,LGASL1,and T stage of gastric cancer had predictive value for recurrence of pN0 patients.Using the leave-one-out cross-validation,the two markers,when combined with clinicopathological features,achieved 85.7%sensitivity and 84.3%specificity for recurrence of pN0 patients in the training group.These data suggested a promising clinical use of the two biological markers in the recurrence and metastasis prediction of gastric cancer and might be helpful for treatment design of gastric cancer.