Aberrant expression of
tyrosine kinases such as c-erbB and EGFR contributes to the progression of
head and neck squamous cell carcinomas (HNSCCs). One mechanism may be potentiation of angiogenesis, since upregulation of
vascular endothelial growth factor (
VEGF) expression by activation of
epidermal growth factor receptor (EGFR) and/or c-erbB-2 has been described. Firstly, we demonstrated expression of all 4 members of the
VEGF family in a panel of 15
HNSCC cell lines which over-express one or more c-
erbB receptors. We then explored the regulatory roles of three major
ligands with different selectivity of binding to c-
erbB receptors (namely
transforming growth factor-alpha (
TGF-alpha),
betacellulin (BTC) and
heregulin-beta1 (
HRG-beta1)) on
VEGF-A, B, C and D expression in selected
HNSCC lines. Using semi-quantitative reverse transcription-PCR, we showed that all three c-erbB
ligands up-regulated
VEGF-A mRNA (all
isoforms) and
VEGF-C (BTC max at 1-10 nM;
TGF-alpha and
HRG-beta1 max
at 10-100 nM) but had no effect on
VEGF-B. Interestingly, all
ligands simultaneously down-regulated the expression of
VEGF-D mRNA. A
monoclonal antibody (mAb) which blocks EGFR
ligand binding (ICR62) down-regulated the basal levels of
VEGF-A (all
isoforms) and
VEGF-C, had no detectable effects on
VEGF-B and increased
VEGF-D. ICR62 also reversed the effects of all three erbB
ligands (
TGF-alpha, BTC and
HRG-beta1) on
VEGF-A,
VEGF-C and
VEGF-D expression. An anti-c-erbB-2 mAb (ICR12) showed similar effects on basal or
ligand-modulated expression of
VEGF in these cell lines, although to a lesser extent. Our results reveal that the four
VEGF genes are regulated by c-erbB signaling pathways in a strikingly different manner, suggesting that they serve distinct, although perhaps complimentary (
VEGF-A and
VEGF-C) or antagonistic (
VEGF-D) functions. The EGFR and c-erbB-2 signaling pathway(s) plays a role in
VEGF regulation in
HNSCC, although EGFR would appear to be dominant in this cell type.