Inhibition of platelet-derived growth factor-mediated signal transduction and tumor growth by N-[4-(trifluoromethyl)-phenyl]5-methylisoxazole-4-carboxamide
Many reports have cited coexpression of platelet-derived growth factor (PDGF) and its receptors by tumor cells or cells supporting tumor growth, suggesting both autocrine and paracrine mechanisms for PDGF-mediated tumor growth. We found that a small organic molecule, N-[4-(trifluoromethyl)phenyl] 5-...
Saved in:
Published in | Clinical cancer research Vol. 3; no. 7; pp. 1167 - 1177 |
---|---|
Main Authors | , , , , , , , , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Philadelphia, PA
American Association for Cancer Research
01.07.1997
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | Many reports have cited coexpression of platelet-derived growth factor (PDGF) and its receptors by tumor cells or cells supporting
tumor growth, suggesting both autocrine and paracrine mechanisms for PDGF-mediated tumor growth. We found that a small organic
molecule, N-[4-(trifluoromethyl)phenyl] 5-methylisoxazole-4-carboxamide (SU101, leflunomide), inhibited PDGF-mediated signaling
events, including receptor tyrosine phosphorylation, DNA synthesis, cell cycle progression, and cell proliferation. SU101
inhibited PDGF-stimulated tyrosine phosphorylation of PDGF receptor (PDGFR) beta in C6 (rat glioma) and NIH3T3 cells engineered
to overexpress human PDGFRbeta (3T3-PDGFRbeta). SU101 blocked both PDGF- and epidermal growth factor (EGF)-stimulated DNA
synthesis. Previously, this compound was shown to inhibit pyrimidine biosynthesis by interfering with the enzymatic activity
of dihydroorotate dehydrogenase. In the current study, EGF-stimulated DNA synthesis was restored by the addition of saturating
quantities of uridine, whereas PDGF-induced DNA synthesis was not, suggesting that the compound demonstrated some selectivity
for the PDGFR pathway that was independent of pyrimidine biosynthesis. Selectivity was further demonstrated by the ability
of the compound to block the entry of PDGF-stimulated cells into the S phase of the cell cycle, without affecting cell cycle
progression of EGF-stimulated cells. In cell growth assays, SU101 selectively inhibited the growth of PDGFRbeta-expressing
cell lines more efficiently than it inhibited the growth of PDGFRbeta-negative cell lines. SU101 inhibited the s.c., i.p.,
and intracerebral growth of a panel of cell lines including cells from glioma, ovarian, and prostate origin. In contrast,
SU101 failed to inhibit the in vitro or s.c. growth of A431 and KB tumor cells, both of which express EGF receptor but not
PDGFRbeta. SU101 also inhibited the growth of D1B and L1210 (murine leukemia) cells in syngeneic immunocompetent mice, without
causing adverse effects on the immune response of the animals. In an i.p. model of tumor growth in syngeneic immunocompetent
mice, SU101 prevented tumor growth and induced long-term survivors in animals implanted with 7TD1 (murine B-cell hybridoma)
tumor cells. Because PDGFRbeta was detected on most of the tumor cell lines in which in vivo growth was inhibited by SU101,
these data suggest that SU101 is an effective inhibitor of PDGF-driven tumor growth in vivo. |
---|---|
ISSN: | 1078-0432 1557-3265 |