The Effects Of Osteopontin In The Lympho Node Metastasis Of Gastric Cancer

Objective(1) To examine the expression of osteopontin(OPN) in gastric cancer tissues and investigate the relationship between OPN and lymphangiogenesis as well as lympho node metastasis of gastric cancer.(2) To examine the expression of osteopontin in some gastric cancer cell lines and further explore the molecular mechanism of the relationship between OPN and lymphangiogenesis-related factors[vascular endothelial growth factor-C(VEGF-C), cyclooxygenase-2(COX-2)]in the lympho node metastasis of gastric cancer.Methods(1) Ninety-three samples of primary gastric cancer were immunohistochemically examined for OPN,VEGF-C and lymphatic endothelial cell specific marker-lymphatic vessel endothelial hyaluronan receptor(LYVE-1) was used to evaluate lymphangiogenesis in gastric cancer.(2) RT-PCR and Western bloting were used to examine the expression of OPN in Gastric cancer cell line MKN28,SGC7901 and BGC823.The cell line MKN28 was chosed to transfect with the chemically synthesized small interfering RNA(siRNA) formulated by lipofectamine 2000.RT-PCR was performed to examine the mRNA expression of OPN,VEGF-C and COX-2 before and after interference.Western blotting was performed to examine the change of OPN and COX-2 as well.ELISA was used to detect the level of VEGF-C in the supernatant of the control gastric cancer cells and the interfered ones.Results(1) The positive expression of OPN and VEGF-C in the primary tumor were 64.5% (60/93) and 69.9%(65/90),respectively.LYVE-1 was positive in 19 cases(20.4%). Significant correlation was found between the expression of OPN and VEGF-C,and both were also correlated to serosa invasion,TNM stage and lymph node metastasis(p＜0.05) while there was no significant correlation to lymphangiogenesis(p＞0.05). Moreover,the expression of OPN and VEGF-C were not related to the prognosis of patients(p＞0.05).(2) RT-PCR and Western bloting showed OPN was expressed in gastric cancer cell lines MKN28 and SGC7901 while which was not seen in the BGC line. Sequence-specific siRNAs targeting OPN in MKN28 suppressed the expression of OPN and COX-2 at the levels of protein and mRNA.The same result was observed in the expression of VEGF-C using the methods of RT-PCR and ELISA.Conclusions(1) Our data suggest that OPN is expressed in gastric cancer tissue and some cell lines. The expression of OPN correlates with VEGF-C expression and both of them correlate with the presence of lympho node metastasis in gastric cancer.(2) OPN siRNA can decease the expression of COX-2 and VEGF-C,suggesting OPN may up-regulate the expression of VEGF-C and COX-2 in the lympho node metastasis of gastric cancer via lymphangiogenesis pathway.