A conditional mouse mutant in the tumor suppressor SdhD gene unveils a link between p21(WAF1/Cip1) induction and mitochondrial dysfunction.
Mutations in mitochondrial complex II (MCII; succinate dehydrogenase, Sdh) genes cause familiar pheochromocytoma/paraganglioma tumors. Several mechanisms have been proposed to account for Sdh-mutation-induced tumorigenesis, the most accepted of which is based on the constitutive expression of the hypoxia-inducible factor 1α (Hif1α) at normal oxygen tension, a theory referred to as "pseudo-hypoxic drive". Other molecular processes, such as oxidative stress, apoptosis, or chromatin remodeling have been also proposed to play a causative role. Nevertheless, the actual contribution of each of these mechanisms has not been definitively established. Moreover, the biological factors that determine the tissue-specificity of these tumors have not been identified. In this work, we made use of the inducible SDHD-ESR mouse, a conditional mutant in the SdhD gene, which encodes the small subunit of MCII, and that acts as a tumor suppressor gene in humans. The analysis of the Hif1α pathway in SDHD-ESR tissues and in two newly derived cell lines after complete SdhD loss -a requirement for hereditary paraganglioma type-1 tumor formation in humans- partially recapitulated the "pseudo-hypoxic" response and rendered inconsistent results. Therefore, we performed microarray analysis of adrenal medulla and kidney in order to identify other early gene expression changes elicited by SdhD deletion. Our results revealed that each mutant tissue displayed different variations in their gene expression profiles affecting to different biological processes. However, we found that the Cdkn1a gene was up-regulated in both tissues. This gene encodes the cyclin-dependent kinase inhibitor p21(WAF1/Cip1), a factor implicated in cell cycle, senescence, and cancer. The two SDHD-ESR cell lines also showed accumulation of this protein. This new and unprecedented evidence for a link between SdhD dysfunction and p21(WAF1/Cip1) will open new avenues for the study of the mechanisms that cause tumors in Sdh mutants. Finally, we discuss the actual role of Hif1α in tumorigenesis.
Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla. Seville, Spain ; Departamento de Hematología. Hospital Universitario Virgen del Rocío. Seville, Spain.
Africa
A
Millán-Uclés
Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla. Seville, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.
Blanca
B
Díaz-Castro
Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla. Seville, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.
Paula
P
García-Flores
Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla. Seville, Spain ; Departamento de Hematología. Hospital Universitario Virgen del Rocío. Seville, Spain.
Alicia
A
Báez
Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla. Seville, Spain ; Departamento de Hematología. Hospital Universitario Virgen del Rocío. Seville, Spain.
José Antonio
JA
Pérez-Simón
Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla. Seville, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.
José
J
López-Barneo
Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla. Seville, Spain ; Departamento de Hematología. Hospital Universitario Virgen del Rocío. Seville, Spain.
José I
JI
Piruat
D000310:Adrenal Gland Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000311:Adrenal Glands / Q000378:metabolism / Q000473:pathology; D000818:Animals; D063646:Carcinogenesis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics* / Q000378:metabolism; D042963:Electron Transport Complex II / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010235:Paraganglioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010673:Pheochromocytoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D013385:Succinate Dehydrogenase; D015854:Up-Regulation
C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008565:Membrane Proteins; D042963:Electron Transport Complex II; C574938:SDHD protein, mouse; D013385:Succinate Dehydrogenase