EPAS1 and hereditary leiomyomatosis and renal cell cancer: Isaacs et al (2005) also examined HIF-1α expression in kidney tumours from patients with HLRCC. Interestingly, six of the seven tumours were from patients less than 40 years of age. HIF expression, evaluated by immunohistochemisty, was determined in cancerous tissues in relation to normal, matched renal parenchyma from the same patient. Both HIF-1α and HIF-2α were found to be significantly overexpressed in HLRCC renal tumours, but HIF-1α expression seemed to be preferentially increased compared to HIF-2α.