Subject(s)
Cell Hypoxia , Neoplasms/metabolism , Signal Transduction , Glucose/metabolism , Glutamine/metabolism , Humans , Neoplasms/pathologyABSTRACT
It has become increasing clear that alterations in cellular metabolism have a key role in the generation and maintenance of cancer. Some of the metabolic changes can be attributed to the activation of oncogenes or loss of tumor suppressors. Here, we show that the mitochondrial sirtuin, SirT3, acts as a tumor suppressor via its ability to suppress reactive oxygen species (ROS) and regulate hypoxia inducible factor 1α (HIF-1α). Primary mouse embryo fibroblasts (MEFs) or tumor cell lines expressing SirT3 short-hairpin RNA exhibit a greater potential to proliferate, and augmented HIF-1α protein stabilization and transcriptional activity in hypoxic conditions. SirT3 knockdown increases tumorigenesis in xenograft models, and this is abolished by giving mice the anti-oxidant N-acetyl cysteine. Moreover, overexpression of SirT3 inhibits stabilization of HIF-1α protein in hypoxia and attenuates increases in HIF-1α transcriptional activity. Critically, overexpression of SirT3 decreases tumorigenesis in xenografts, even when induction of the sirtuin occurs after tumor initiation. These data suggest that SirT3 acts to suppress the growth of tumors, at least in part through its ability to suppress ROS and HIF-1α.
Subject(s)
Cell Proliferation , Hypoxia-Inducible Factor 1, alpha Subunit/genetics , Mitochondria/metabolism , Neoplasms/pathology , Reactive Oxygen Species/metabolism , Sirtuin 3/physiology , Animals , Cell Proliferation/drug effects , Cells, Cultured , Down-Regulation/genetics , Embryo, Mammalian , Gene Expression Regulation, Neoplastic , HCT116 Cells , Humans , Hypoxia-Inducible Factor 1, alpha Subunit/metabolism , Mice , Mice, Nude , Mitochondria/drug effects , Neoplasms/genetics , Neoplasms/metabolism , RNA, Small Interfering/pharmacology , Sirtuin 3/antagonists & inhibitors , Sirtuin 3/genetics , Sirtuin 3/metabolism , Xenograft Model Antitumor AssaysABSTRACT
Monosomy 7 and deletion of 7q are recurring abnormalities in malignant myeloid diseases. Here we extensively characterize an approximately 2-Mb commonly deleted segment (CDS) of 7q22 bounded by D7S1503 and D7S1841. Approximately 1.8 Mb of sequence have been generated from this interval, facilitating the construction of a transcript map that includes large numbers of genes and ESTs. The intron/exon organization of seven genes and expression patterns of three genes were determined, and leukemia samples were screened for mutations in five genes. We have used polymorphic markers from this region to examine leukemia cells for allelic loss within 7q22. Finally, we isolated mouse genomic clones orthologous to several of the characterized human genes. Fluorescence in situ hybridization studies using these clones indicate that a region of orthologous synteny lies on proximal mouse chromosome 5. These resources should greatly accelerate the pace of candidate gene discovery in this region.
