Existed an intrinsic balance between the two isoforms, when the expression of one isoform elevated, the other decreased. The elevation of the gelatinolytic abilities of CD97/EGF1,2,5 kd clones was considered due to the alternation of activity of MMPs. Galle J reported HT1080 cells which over-expressing CD97 small isoform possessed the highest activity of matrix metalloproteinases MMP-2 and MMP-9, but HT1080 cells over-expressing CD97 full length isoform responded with almost unaltered or even decreased levels of MMPs as compared with wild-type or empty plasmid cells. Although multivariate analysis reported no significant relations between CD97 expression and lymph node metastasis, results in this study showed noticeably retarded primary tumor growth as well as fewer metastatic tumor cells in regional lymph nodes in CD97/EGF1,2,5 kd group of the orthotopically transplanted metastatic mouse model of gastric carcinoma. But how can CD97 small isoform facilitate lymph node metastasis? In recent years, developed evidence based on Stephen Paget’s “seed and soil” hypothesis has emerged. Growth factors secreted by the primary tumor prime certain tissues for tumor cell engraftment. In response to these soluble factors, tumor associated cells such as macrophages and haematopoietic progenitor cells cluster at some functional microenvironment, which is also known as “metastatic niches” that supports metastatic tumor cell maintenance and actively regulates cell proliferation and invasion. This microenvironment is considered to comprise supportive stromal cells, soluble factors, vascular networks, nutrients and metabolic components, and the structural extracellular matrix Tasocitinib in vivo architecture. VEGF, critical regulator of tumor angiogenesis, is thought to mobilize the bone marrow derived cells, which may subsequently be recruited and facilitate tumor growth and metastasis 888. It was reported that BMDCs express VEGFR localized to pre-metastatic sites before the arrival of tumor cells, and inhibition of VEGFR1 could prevent the BMDCs infiltration and “metastatic niche” formation in lungs. CD44 is also known to be essential for the homing and engraftment of the cancer stem cells. It was reported after knocking down of CD44v6, it failed to assemble a soluble matrix in pre-metastatic organ, which allows a highly metastatic pancreatic cell line ASML embedding and growth. It strongly indicated both VEGFR and CD44 were involved in the preparation of metastatic niche. In this study, VEGFR, CD44 along with platelet endothelial cell adhesion molecule were together employed in an early ymph node metastatic model of gastric caner to investigate the possible mechanism of the metastasisfacilitating role of CD97 small isoform. In regional lymph nodes along the lesser gastric curvature prior to metastasis, the control group showed already existed, aggregated, high intensity of CD97 protein expression, as well as the elevated intensity of CD44, VEGF and CD31 expression; while the CD97/EGF1,2,5 kd clones showed comparatively scattered and down regulated transmembrane receptors protein expression, which indicated CD97 small isoform may also contribute.