Inverse Correlation between mRNA Expression of Plasminogen Activator Inhibitor‐2 and Lymph Node Metastasis in Human Breast Cancer

We examined mRNA expressions of urokinase‐type plasminogen activator (u‐PA), its specific receptor (u‐PR), and plasminogen activator inhibitors (PAI‐1 and PAI‐2) in 50 human breast cancers by the reverse transcriptase‐polymerase chain reaction method. The expressions of the genes are discussed in relation to the clinicopathological findings. In the overall population in breast cancers, a low level of PAI‐2 expression was significantly associated with lymph node involvement (P < 0.0001). The u‐PA, u‐PR, and PAI‐1 expressions tended to be at high levels in such metastatic cancers. Also, positive expression of u‐PA, u‐PR, and PAI‐1 was significantly correlated with negative expression of PAI‐2. These results indicate that PAI‐2 may play a critical role in the regulation of extracellular matrix degradation during tumor cell invasion and metastasis, and the expression of PAI‐2 may be useful as a marker to evaluate the prognosis of breast cancers.