PHD3 regulates differentiation, tumour growth and angiogenesis in pancreatic cancer

Purpose: Tumour hypoxia activates hypoxia-inducible factor-1 (HIF-1) and indluences angiogenesis, cell survival and invasion. Prolyl hydroxylase-3 (PHD3) regulates degradation of HIF-1α. The effects of PHD3 in tumour growth are largely unknown.

Experimental design: PHD3 expression was analysed in human pancreatic Cancer tissues and Cancer cell lines by real-time quantitative PCR and immunohistochemistry. PHD3 overexpression was established by stable transfection and downregulation by short interfering RNA technology. VEGF was quantified by enzyme-linked immunosorbent assay. Matrigel invasion assays were performed to examine tumour cell invasion. Apoptosis was measured by annexin-V staining and Caspase-3 assays. The effect of PHD3 on tumour growth in vivo was evaluated in an established orthotopic murine model.

Results: PHD3 was upregulated in well-differentiated human tumours and cell lines, and regulated hypoxic VEGF secretion. PHD3 overexpression mediated tumour cell growth and invasion by induction of Apoptosis in a nerve growth factor-dependent manner by the activation of Caspase-3 and phosphorylation of focal adhesion kinase HIF-1 independently. In vivo, PHD3 inhibited tumour growth by abrogation of tumour angiogenesis.

Conclusion: Our results indicate essential functions of PHD3 in tumour growth, Apoptosis and angiogenesis and through HIF-1-dependent and HIF-1-independent pathways.