OVER-EXPRESSION OF UROKINASE RECEPTOR IN HUMAN EPIDERMOID-CARCINOMA CELL-LINE (HEP3) INCREASES TUMORIGENICITY ON CHORIOALLANTOIC MEMBRANE AND IN SEVERE-COMBINED-IMMUNODEFICIENT MICE

Using chorio-allantoic membranes (CAMs) of chick embryos and severe-co mbined-immunodeficient (SCID) mice, we investigated the effects of uro kinase-type plasminogen-activator receptor (u-PAR) over-expression on the process of invasion and tumorigenicity. By the transfection of u-P AR cDNA, 3 u-PAR-over-expressing clones expressing 1.6- to 4.6-fold mo re u-PAR mRNA than parent cells were obtained from a human epidermoid- carcinoma cell line, HEp3, that expresses urokinase-type plasminogen a ctivator (U-PA) and u-PAR. All the u-PAR-over-expressing clones showed greater invasiveness (13 to 29%) than that of parent HEp3 cells on CA Ms. Immunohistochemistry revealed densely stained u-PAR-positive cells near the margin of the tumor, where a u-PAR-over-expressing clone, de signated SM-3, was invading thickened fibrous tissue on CAMs. Three u- PAR-overexpressing clones formed larger tumors (>40 mm(3)) than did pa rent HEp3 cells on CAMs. Moreover, when the u-PAR-overexpressing clone (SM-3) was injected s.c. into the back of the SCID mice it produced a larger tumor volume than the control(HEp3) and down-regulated (AS-2) clones and significantly shortened the survival of SCID mice. These re sults demonstrate that increased u-PAR expression is an important fact or in determining the malignant phenotype that makes cancer cells more invasive and tumorigenic. (C) 1998 Wiley-Liss, Inc.