Summary
Urokinase-type plasminogen activator receptor (uPAR) and Epidermal Growth Factor Receptor
(EGFR) are ubiquitous receptors involved in the control of a variety of cellular processes
frequently found altered in cancer cells. The EGFR has been recently described to
play a transduction role of uPAR stimuli, mediating uPA-induced proliferation in highly
malignant cells that overexpress uPAR. We compared the uPA production, the presence
of uPAR, AR, EGFR and Her2 with the chemotaxis and the Matrigel invasion in ten human
PCa cell lines and observed that: (1) the levels of Her2, but not of EGFR, as well
as the uPA secretion, cell motility and Matrigel invasion were statistically higher
in AR negative than in AR positive PCa cells; (2) the uPA secretion and uPAR expression
were positively related to Matri-gel invasion; (3) the EGF was able to stimulate chemotaxis
and Matrigel invasion in a dose-dependent manner; (4) the EGF-induced cell migration
was statistically higher in AR negative than in AR positive cells with a similar increase
with respect to basal value (about 2.6 fold); (5) the Matrigel invasion was statistically
higher in AR negative than in AR positive PCa cells also if the increment of Matrigel
invasion after EGF treatment was statis-
tically higher in AR positive respect to AR negative cells; (6) the EGF induced uPA
secretion and its membrane uptake through the increment of uPAR; and (7) these effects
were blocked by EGFR/Her2 tyrosine kinase inhibitors with IC50 lower than those needed to inhibit cell proliferation and required PI3K/Akt,
MAPK and PI-PLC activities as verified by inhibition experiments. These enzymatic
activities were regulated in different manners in PTEN positive and negative cells.
In fact, the inhibition of PI3K blocked the EGF-induced invasiveness in PTEN positive
cells but not in PTEN negative cells, in which PI3K activity was not influenced by
EGFR/Her2 activation, whereas the inhibition of MAPK was able to block the invasive
phenomena in both cell types. Taken together, our data suggest that the blockade of
EGFR could attenuate the invasive potential of PCa cells. In addition, considering
that the EGFR expression is related to higher Gleason grade of PCa and that EGFR levels
are increased after anti androgenic therapy, this therapeutic approach could slow
down the metastasis formation which represents the most dramatic event of PCa progression.
Keywords
Prostatic carcinoma - EGFR - uPA - tyrosine kinase inhibitors