Vascular endothelial growth factor family members are differentially regulated by c-erbB signaling in head and neck squamous carcinoma cells

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 vascu lar 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 o f 15 HNSCC cell lines which over-express one or more c-erbB receptors. We t hen explored the regulatory roles of three major ligands with different sel ectivity of binding to c-erbB receptors (namely transforming growth factor- alpha (TGF-alpha), betacellulin (BTC) and heregulin-beta1 (HRG-beta1)) on V EGF-A, B, C and D expression in selected HNSCC lines. Using semi-quantitati ve reverse transcription-PCR, we showed that all three c-erbB ligands up-re gulated VEGF-A mRNA (all isoforms) and VEGF-C (BTC max at 1-10 nM; TGF-alph a and HRG-beta1 max at 10-100 nM) but had no effect on VEGF-B. Interestingl y, 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 dete ctable effects on VEGF-B and increased VEGF-D. ICR62 also reversed the effe cts of all three erbB ligands (TGF-alpha, BTC and HRG-beta1) on VEGF-A, VEG F-C and VEGF-D expression. An anti-c-erbB-2 mAb (ICR12) showed similar effe cts on basal or ligand-modulated expression of VEGF in these cell lines, al though to a lesser extent. Our results reveal that the four VEGF genes are regulated by c-erbB signaling pathways in a strikingly different manner, su ggesting that they serve distinct, although perhaps complimentary (VEGF-A a nd VEGF-C) or antagonistic (VEGF-D) functions. The EGFR and c-erbB-2 signal ing pathway(s) plays a role in VEGF regulation in HNSCC, although EGFR woul d appear to be dominant in this cell type.