INTERACTION OF TISSUE-PLASMINOGEN ACTIVATOR INHIBITOR WITH CELL-SURFACE GUANIDINOBENZOATASE AND UROKINASE PLASMINOGEN-ACTIVATOR

This study employs fluorescent inhibitor molecules to detect both cell surface proteases and their receptor sites on colonic carcinoma cells . Present studies are concerned with the interactions of the tumour as sociated proteases, guanidinobenzoatase (GB) and plasminogen activator s (PAs) with PAs inhibitor type 1 (PAI-1). The active enzymes on the c ell surfaces in frozen sections of human colonic carcinoma tissue were located by staining with two active site directed fluorescent inhibit ors, 9-aminoacridine (9-AA) and Rhodamine labelled PAI-1 (Rh-PAI-1), f ollowed by fluorescence microscopy. Fibrin treated sections, which now lack GB but have receptor proteins for GB, fail to bind 9-AA and Rh-P AI-1. When these fibrin-treated sections were incubated with purified colonic carcinoma GB and u-PA, both enzymes were bound to the tumour c ells in these sections and subsequent challenging with fluorescent pro bes for GB resulted in bright fluorescence under appropriate microscop ic conditions. On the other hand when fibrin treated sections were inc ubated with t-PA, followed by challenging with Rh-PAI-1, no red fluore scence was observed. It is suggested that the GB and u-PA have similar specific binding sites which can recognise and bind to the receptors on tumour cells in fibrin-treated sections, but t-PA has no such bindi ng site and fails to recognise the cell surface receptors for GB. Thes e GB-receptors may have a possible role in the regulation of GB and u- PA activity during tumour cell invasion and metastasis.