The actual mechanisms by which
carcinoma cells metastasize to lymph nodes are still unclear, and there is a need to establish in vivo experimental models suitable for the investigation of
lymph node metastasis. For the purpose, we established a highly lymph node-metastasizing line, designated AZL5G, derived from a human
gastric cancer cell line, AZ521, which had low capacity for
lymph node metastasis. AZL5G cells transplanted orthotopically in the nude mouse stomach metastasize predominantly to the regional lymph nodes, showing little potential for hematogenous
metastasis. AZL5G
tumors developing in the stomach and regional lymph nodes showed poorly differentiated
adenocarcinoma with medullary growth, and their histologic appearance strongly resembled that of parental AZ521. The growth activities in vitro of low-metastatic AZ521 and high-metastatic AZL5G were almost the same, but the tumorigenicity in vivo of AZL5G was significantly higher than that of AZ521. AZL5G cells also showed clearly higher abilities of cell locomotion and adhesion to
type IV collagen and
fibronectin in vitro as compared with AZ521 cells. Flow cytometric analysis demonstrated that the expression of
integrin beta1 subfamily except for
alpha6 integrin was generally increased in AZL5G cells than in AZ521 cells. Especially, the expression of alpha1 and alpha2
integrins in AZL5G cells was clearly higher than in AZ521, while alpha(v)
beta3 integrin,
E-cadherin,
ICAM-1 and CD44H were not expressed by either cell line. The cell adhesion blocking assay showed that DGEA-containing
peptide, which is composed of
alpha2 integrin recognition sequence, significantly reduced the adhesiveness of AZL5G cells to
type IV collagen as well as to
type I collagen and
laminin. Furthermore, the administration of anti-alpha2
integrin mAb or
DGEA peptide in AZL5G-transplanted nude mice produced a significant reduction in the number of
lymph node metastases. These data suggest that the up-regulation of
alpha2 integrin expression by
gastric cancer cells may play a critical role in the process of
lymph node metastasis through the increased adhesiveness to
type IV collagen. In conclusion, we established a
gastric cancer cell line, AZL5G, with a highly metastatic potential to lymph nodes. This well-characterized line and its in vivo experimental model should be useful for investigation of the mechanisms of
lymph node metastasis and for establishment of a new therapeutic approach for human
gastric cancer.