K. Kariko et al., OVEREXPRESSION OF UROKINASE RECEPTOR INCREASES MATRIX INVASION WITHOUT ALTERING CELL-MIGRATION IN A HUMAN OSTEOSARCOMA CELL-LINE, Cancer research, 53(13), 1993, pp. 3109-3117
Proteolysis triggered by receptor-bound urokinase-type plasminogen act
ivator (uPA) involves a cascade of species-specific molecular interact
ions. To study the role of the uPA receptor (uPAR) in such interaction
s, a human osteosarcoma cell line (HOS), which normally expresses low
levels of uPAR, was transfected with human uPAR complementary DNA. One
of several stably transformed clonal cells lines, designated 2A2, was
characterized and compared to the parental HOS, revealing the followi
ng: (a) stable incorporation of uPAR complementary DNA into the genome
demonstrated by Southern blot analysis; (b) a 10-fold increase in ste
ady state mRNA levels of uPAR assessed by Northern blot analysis; (c)
a 2-fold increase in the surface expression of glycosylphosphatidvlino
sitol anchored uPAR protein determined by enzyme-linked immunosorbent
assay and by the specific binding of radiolabeled single chain uPA; (d
) a 2-fold increase in internalization and degradation of radiolabeled
uPA/PAI-1 complexes; and (e) a 2-fold increase in receptor-bound uPA-
mediated plasmin generation measured by the cleavage of a chromogenic
substrate and degradation of I-125-I-labeled laminin. The involvement
of uPAR in cellular processes was determined by comparing 2A2 and HOS
cells in in vitro migration and invasion assays. The migration of 2A2
cells were slower on fibronectin-coated surfaces in a linear under-aga
rose assay, but both cell lines migrated at the same rate on uncoated
polycarbonate filters in Boyden chamber assays. In the invasion experi
ments, 4 times more 2A2 than HOS cells penetrated through the barrier
of reconstituted basement membrane Matrigel. These data suggest that u
PAR does not potentiate random cell migration but facilitates matrix d
egradation and subsequent cell invasion.