Urokinase (u-PA) and the u-PA Receptor
Urokinase (u-PA) and the u-PA receptor (u-PAR) influence tumor invasion and metastasis.
The purpose of this study is to determine whether u-PAR display in 4 human bladder cancer cell lines (RT4, 253J, EJ and T24) can be modulated with substances including phorbol 12-myristate 13-acetate, interferon gamma, epidermal growth factor, and transforming growth factor beta and to correlate changes with u-PAR expression with the ability of these cells to invade artificial basement membrane (Matrigel).
u-PAR display was determined using flow cytometry and immunohistochemical staining with an anti-u-PAR monoclonal antibody (Mab3936). Matrigel invasion chamber assays were used to assess the invasive capacity of the cell lines.
The T24, EJ and 253J cells expressed the u-PAR while the RT4 cells did not. The EJ cells (expressing the highest u-PA antigen levels and the u-PAR) invaded Matrigel. The T24 cells, which expressed the u-PAR but do not produce u-PA, invaded Matrigel only when pretreated with high molecular weight urokinase (HMW u-PA). HMW u-PA pretreatment of EJ and 253J cells also enhanced their invasive potential. Blocking u-PA/u-PAR attachment with an anti-u-PAR monoclonal antibody (Mab3936) inhibited invasion. Modulation of u-PAR expression on cell lines displaying the u-PAR directly affected in vitro invasiveness of the cell lines. The RT4 cells which lack the u-PAR were not invasive under conditions tested. Thus, bladder cancer cell lines require both u-PA and the u-PAR to invade Matrigel and modulation of u-PAR display directly affects their in vitro invasive capacity.
This study shows that bladder tumor cells produce u-PA and express the u-PAR and require both for in vitro invasion to occur. When bladder cancer cells express the u-PAR, invasiveness can be enhanced by exogenous u-PA and inhibited by anti-u-PAR antibodies. Modulation of u-PAR expression on the cell surface of bladder cancer cells can also affect their ability to invade Matrigel.
Histologically similar bladder tumors show differences in their propensity to invade locally or metastasize. Intrinsic differences in the tumor cells such as the production of u-PA antigen and u-PA receptor on the cell surface and extrinsic differences in the tumor cell environment such as substances influencing u-PAR display or antibodies blocking the u-PAR may affect the biological potential of human bladder cancers and offer one explanation for the aggressive or indolent tumor behavior observed in individual patients.
KeywordsMicrowave Heparin Sarcoma Interferon Glutamine
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