Aims : The cellular response to hypoxia includes the hypoxia inducible factor (HIF)‐induced transcription of genes involved in diverse processes such as glycolysis, angiogenesis and the growth of experimental tumours. Regulation of the level of hypoxia inducible factors 1α and 2α (HIF‐1α and HIF‐2α) is a primary determinant of HIF activity. Recent biochemical and candidate gene approach studies have led to the discovery of three HIF‐regulatory prolyl hydroxylases, PHD‐1, ‐2 and ‐3 and an asparaginyl hydroxylase, also known as FIH (factor inhibiting HIF). In this study, we raised and characterized monoclonal antibodies against PHD‐1, PHD‐2, PHD‐3 and FIH.

Methods and results : Immunohistochemistry of normal tissues with these monoclonal antibodies demonstrated a wide distribution in epithelial cells, stromal cells and leucocytes, with cytoplasmic staining predominating over nuclear staining. A preliminary study of tumours showed variable staining in tumour, stromal and inflammatory cells. While all tumour types showed some positive staining with each antibody, the overall pattern suggested a slight decrease in the amount of staining seen with PHD‐1, ‐2 and ‐3 and an increase in FIH staining in neoplasia compared with corresponding normal tissues.

Conclusions : These monoclonal antibodies will allow further larger scale studies to determine the significance of PHD and FIH expression in neoplasia.