Urokinase-type plasminogen activator expression and proliferation stimulation in head and neck squamous cell carcinoma in vitro and in situ

Background: Stimulation of proliferative activity by urokinase-type plasmin ogen activator (uPA) has been demonstrated in vitro for cultured primary an d carcinoma cells. Objective: To examine the effect of uPA stimulation on cultured squamous ce ll carcinoma cell lines of the head and neck in vitro and to compare the re sults with the situation in tumor tissue specimens. Design: The uPA-mediated growth stimulation of 2 head and neck squamous cel l carcinoma cell lines after suppression of endogenous uPA production was m onitored by measuring H-3-thymidine uptake into cellular DNA. Alternatively , applications of antibodies against the uPA-binding domain of the urokinas e receptor were used to suppress autostimulation. To analyze the situation in situ we performed Western blot and zymographic studies on tissue homogen ates of 25 squamous cell carcinoma specimens. We tested the expression of p roliferating cell nuclear antigen (PCNA), a marker for proliferative activi ty, and uPA in tissue lysates and correlated uPA and PCNA expression by reg ression analysis. Results: High-molecular-weight urokinase had a proliferation stimulative ef fect on both cell lines in vitro. The uPA autostimulation was decreased by blocking the uPA-binding domain of urokinase receptor with antibodies. Regr ession analysis of zymographic and Western blot data of tumor tissue lysate s revealed no significant coherency between PCNA and uPA expression. Immuno histochemical stainings frequently showed different sublocalization of uPA and PCNA within tumors. Conclusion: In vitro uPA-mediated growth stimulation is not necessarily tra nsferable to the in situ situation.