Adenoid cystic carcinoma (AdCC) is characterized by frequent recurrence and distant metastasis. Although lung metastasis in AdCC is very common, the mechanism by which this occurs is uncertain. When five AdCC cell lines (ACCS, ACCT, ACCH, Acc-3, and Acc-M) were screened for metastatic ability by injecting tumor cells into nude mice via the tail vein, lung metastases were found in mice injected with Acc-M (15/16 mice) but not in mice injected with any of the other four cell lines (0/10 mice with each line). To determine why Acc-M metastasizes to the lung but the others do not, we examined the biological characteristics of Acc-M and compared them with those of the other lines.Nuclear factor-κB (NF-κB) may play a key role in malignant tumor behaviors such as invasion and metastasis. Thus, we examined these cell lines for response to tumor necrosis factor (TNF-α), one of the typical stimulators of NF-κB. Although treatment with TNF-α stimulated matrix metalloprotease 9 (MMP-9) expression in all cell lines, the response to TNF-α varied between cell lines; the greatest stimulation was observed in Acc-M. Acc-M expressed higher levels of TNF receptors (both TNF-R1 and TNF-R2) than did the other AdCC lines. Judging from inhibitor-κBα degradation and nuclear translocation and DNA binding by NF-κB, the degree of activation of NF-κB in response to TNF-α in Acc-M cell lines was very high compared to the other lines. Moreover, the ability of Acc-M cells to adhere to endothelial cells, which was greater than that of the other cell lines, was further enhanced by pretreatment with TNF-α. Acc-M cells also expressed higher levels of sialyl Lewis^x than did the other AdCC cell lines. These findings suggest that lung metastasis is mediated by tumor-endothelial cell interaction, which is probably associated with the NF-κB activation pathway. Further experiments are required to identify the molecules that mediate both lung metastasis and NF-κB activation.

We investigated whether the expression levels of urokinase-type plasminogen activator (uPA), uPA receptor (uPAR), and plasminogen activator inhibitor-1 (PAI-1) correlate with clinicopathological features of oral squamous cell carcinoma (SCC). We immunohistochemically examined the expression levels of uPA, uPAR, and PAI-1 in 160 biopsy specimens of oral SCC. Positive stainings for uPA, uPAR, and PAI-1 were observed mainly in SCC cells, and their intensity and number of positive cells were related to lymph node involvement (p < 0.001, p < 0.001, and p < 0.001, respectively). The expression levels of uPA and uPAR were also related to the pattern of invasion (p < 0.05 and p < 0.001, respectively), while both were associated with tumor size (p < 0.05). Moreover, a poor survival rate was related to the expression of uPAR (p < 0.01) and PAI-1 (p < 0.05). These findings suggest that the uPA system may regulate the invasion and metastasis of oral SCC cells.