Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis

• Published in: British journal of cancer 2011-03, Vol.104 (7), p.1151-1159
• Main Authors: Khan, M N, Bhattacharyya, T, Andrikopoulos, P, Esteban, M A, Barod, R, Connor, T, Ashcroft, M, Maxwell, P H, Kiriakidis, S
• Format: Article
• Language: English
• Subjects: 631/337; 631/92/555; 692/699/1585/1588/1351; Amino Acids, Dicarboxylic - pharmacology; Apoptosis; Basic Helix-Loop-Helix Transcription Factors - physiology; Biomedical and Life Sciences; Biomedicine; Cancer Research; Cell Line, Tumor; Cell Survival; Cytoprotection; Drug Resistance; Epidemiology; Humans; Hypoxia-Inducible Factor 1, alpha Subunit - physiology; Kidney Neoplasms - pathology; Mixed Function Oxygenases; Molecular Diagnostics; Molecular Medicine; Oncology; Repressor Proteins - physiology; Von Hippel-Lindau Tumor Suppressor Protein - physiology
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/bjc.2011.73

Background: Clear cell renal cell carcinoma (CCRCC) is the commonest form of kidney cancer. Up to 91% have biallelic inactivation of VHL, resulting in stabilisation of HIF- α subunits. Factor inhibiting HIF-1 is an enzyme that hydroxylates HIF- α subunits and prevents recruitment of the co-activator CBP/P300. An important question is whether FIH-1 controls HIF activity in CCRCC. Methods: Human VHL defective CCRCC lines RCC10, RCC4 and 786–O were used to determine the role of FIH-1 in modulating HIF activity, using small interfering RNA knockdown, retroviral gene expression, quantitative RT–PCR, western blot analysis, Annexin V and propidium iodide labelling. Results: Although it was previously suggested that FIH-1 is suppressed in CCRCC, we found that FIH-1 mRNA and protein are actually present at similar levels in CCRCC and normal kidney. The FIH-1 inhibition or knockdown in the VHL defective CCRCC lines RCC10 and RCC4 (which express both HIF-1 α and HIF-2 α ) resulted in increased expression of HIF target genes. In the 786-O CCRCC cell line, which expresses only HIF-2 α , FIH-1 attenuation showed no significant effect on expression of these genes; introduction of HIF-1 α resulted in sensitivity of HIF targets to FIH-1 knockdown. In RCC4 and RCC10, knockdown of FIH-1 increased apoptosis. Suppressing HIF-1 α expression in RCC10 prevented FIH-1 knockdown from increasing apoptosis. Conclusion: Our results support a unifying model in which HIF-1 α has a tumour suppressor action in CCRCC, held in check by FIH-1. Inhibiting FIH-1 in CCRCC could be used to bias the HIF response towards HIF-1 α and decrease tumour cell viability.