Preference of mitochondrial respiration over the Warbürg effect in breast tumor initiating cells in conditions of oxygen and glucose deprivation.
ABSTRACT: Background: cancer cells rely on glycolysis as main ATP source (Warbürg effect). Tumor-initiating cells (TICs) are the fraction of cells that give raise and repopulate tumors. TICs are exposed to prolonged periods of oxygen and glucose deprivation (OGD), as they live in a hypoxic niche and they withstand prolonged lack of blood vessels during initial tumorigenesis or metastasis formation (avascular phase). Warbürg effect is energetically inefficient; we hypothesize that TICs might have differential metabolic features. Tumor eradication requires killing TICS; finding such features would have therapeutic implications. Methodology/principal findings: 106 MDA-MB-231 breast-cancer cells (hereafter Wt) were exposed for 5 weeks to 0.2% oxygen and 0.1g/l glucose, recovering 9 clones. Both flow-cytometry (50-fold enrichment in the CD24-/CD44+/CD133+ population) and xenografts in NOD/SCID mice using 100 cells (75% vs. 16% engraftment) suggest that OGD-resistant clones are true TICs (hereafter “TIC clones”). TIC clones showed a 30-fold higher replication and viability (BRDU incorporation, colony assay) than Wt. When exposed to OGD, ATP-production dropped 5-fold in WT, but was maintained in TIC clones by increasing 5-fold the fatty acid and oxygen consumption. These properties were explained by lack of upregulation of HIF-1 alpha and PDK1, as well as an increase in ATP-synthase. Analysis with metabolic inhibitors (2-deoxyglucose, antimycin-A) confirmed glycolysis and mitochondrial respiration as main routes of metabolism for Wt and TIC clones respectively. Metabolomics revealed that glutamine catabolism generated the NADPH required to quench reactive oxygen species generated during mitochondrial respiration in TIC clones. Glutamine deprivation or mitochondrial blockers were able to abrogate the viability of TIC clones. Conclusions/significance: the TIC-fraction of a cancer cell population withstands prolonged OGD by switching from the Warbürg effect to mitochondrial respiration. Targeting this metabolic feature abrogates the survival of TICs. Overall design: Mitochondrial metabolism in cancer-stem cells.
INSTRUMENT(S): [HuEx-1_0-st] Affymetrix Human Exon 1.0 ST Array [transcript (gene) version]
Project description:The cancer stem cell model maintains that tumors are organized in a hierarchy driven by tumor initiating cells (TICs), and that patient survival inversely correlates with TIC gene expression. Here we generated a prognostic signature for HER2+ breast cancer from TICs purified from MMTV-Her2/Neu mammary tumors. TICs from this model, identified as Lin-:CD24+:JAG1- at a frequency of 2-5% by serial and single cell transplantation assays, showed elevated expression of proliferation genes and low expression of differentiation genes (compared to non-TIC fraction CD24- of the same tumor). We used microarrays to detect differentially expressed genes in the TIC fraction compared to the non-TIC fraction of the same tumor Cells from each primary tumor were separated by FACS into TIC and non-TIC fractions and total RNA was extracted and hybridized on Affymetrix microarrays.
Project description:RNA-seq analysis was performed on TICs and the parental counterparts of 4 LSCC cell lines. In addition, PRKCI knock down (KD) variants of these cells were sequenced. Subsequent analysis revealed that activation of HH signaling, a known driver of the TIC phenotype, is dependent on PRKCI expression. Examination of TICS, parental cells, parental PRKCI KD cells, and TIC PRKCI KD cells
Project description:Undifferentiated pleomorphic sarcomas (UPS) are thought to harbor a small population of cells with unique capability of tumor initiation and maintenance. These tumor initiating cells (TICs) are regarded as the drivers of cancer progression. However, the evidence for this tumor initiating cell (TIC) concept is based on the xenotransplantation assays in mice and the clinical relevance of the TIC concept remains unclear in UPS. We hypothesized that the distinct properties of the TICs would be reflected in the clinical outcome if the TIC concept is relevant in UPS. Here we performed global gene expression profiling of TIC-enriched side population (SP) fractions and non-SP fractions sorted from 15 UPS primary samples. Ninety-three genes were differentially expressed in between SP fractions and non-SP fractions. The UPS TIC gene expression signature score summarizing expression of these genes was calculated for a gene expression data and was correlated with clinical outcome. In the 15 samples used to generate the signature, patients with high scores in the SP fractions were associated with worse survival. We then tested the two independent published datasets with gene expression data on bulk unsorted samples, assuming that the TIC gene expression would persist in the non-TICs. Patients with high scores had significantly worse metastasis-free survival in both datasets. The significance of the score remained significant even considering for the known prognostic factor of UPS. Thus, gene expression signature derived from UPS TICs predicts clinical outcome, suggesting the clinical relevance of the TIC concept in UPS. Overall design: Fifteen human UPS samples were obtained at the Mount Sinai Hospital between February of 2008 and January of 2011, according to an approved protocol of the institutional review board.
Project description:Most solid tumors seem to be organized in a hierarchy in which only a fraction of cells, termed tumor-initiating cells (TICs), is capable of disseminating new tumors after transplantation into recipient mice. However, whether a single TIC can induce a tumor or whether it requires additional TICs or non-TICs for tumor initiation is not known. Here we show that injections of single CD24+:Jag1- cells from Her2/Neu+ mammary tumors into recipient mammary glands induced tumors at a frequency of 1/22. Single cell-derived secondary tumors exhibited histology, flow cytometry and global expression profiles that were indistinguishable from primary tumors. Thus, a single TIC can act cell autonomously to induce a tumor and therefore complete eradication of all TICs would be required to cure cancer. Total RNA obtained from primary MMTV-Neu tumors, secondary tumors generated by lin- cell transplantation, and secondary tumors generated by a single TIC, were used for microarray analysis to determine differentially regulated genes in the secondary tumors. Cluster analysis based on gene expression were then performed to assess tumor similarity
Project description:The tumor-initiating cell (TIC) model accounts for the phenotypic and functional heterogeneity among cancer cells found within human cancers. MicroRNAs (miRNAs) are key regulatory molecules frequently aberrantly expressed in tumors, and may play important roles in contributing towards tumor heterogeneity and TIC behavior. More recent efforts have focused on miRNAs for diagnosis and as targets for novel therapies. In this study, we identified the miRNAs, miR-1246 and miR-1290, which are crucial for the function of TICs, thereby driving cancer progression in human non-small cell lung cancer (NSCLC). These miRNAs are restricted to patient-derived tumorspheres and CD166+ primary tumor cells, both enriched for TICs. Loss of either miRNA impacted the tumorigenic potential of TICs and their ability to metastasize. Interestingly, longitudinal analyses of serum miR-1246 and miR-1290 levels correlated circulating levels of either miRNA to the clinical response seen in lung cancer patients to epidermal growth factor receptor (EGFR) tyrosine kinase inhibition, chemotherapy and radiotherapy. Functionally, direct inhibition of miR-1246 or miR-1290 with locked nucleic acid (LNA) administered systemically, could arrest the growth of established patient-derived tumors xenografted in immunocompromised mice, thus indicating these miRNAs are clinically useful as biomarkers for tracking disease progression and as therapeutic targets. Overall design: We first identified miRNAs which are enriched in CD166+ TICs relative to CD166- non-TICs (n = 3 patients), and intersected these with miRNAs enriched in patient-derived tumorspheres relative to normal NHBE and SAEC. This method, utilizing two distinct manners of purifying for TICs, enabled us to robustly identify a conserved set of miRNAs which were exclusive to TICs but not non-TICs.
Project description:Tumor initiating cells (TIC) have been identified and functionally characterized in hematological malignancies as well as in solid tumors such as breast cancer. In addition to their high tumor-initiating potency, TICs are important for metastasis formation and involved in chemotherapy resistance. Here we explored the molecular pathways that enable the tumor initiating potential of a cancer cell subset of the transgenic MMTV-PyMT mouse model for metastasizing breast cancer. The cell population, characterized by the marker profile CD24+CD90+CD45-, revealed a high tumorigenicity compared to CD24-CD90- cancer cells in colony formation assays as well as upon orthotopic transplantation into the mammary fad pad of mice. In addition, these orthotropically grown CD24+CD90+ TICs metastasized to the lungs. Upon cell sorting from primary tumors the transcriptome of TICs was compared with that of CD24-CD90- cancer cells by RNAseq. In addition to more established TIC signatures, such as epithelial-to-mesenchymal transition or mitogen signaling, an upregulated gene set comprising several classes of proteolytic enzymes was uncovered in CD24+CD90+TICs. Accordingly, TICs showed a high intra- and extracellular proteolytic activity. Application of a broad range of protease inhibitors to TICs in a colony formation assay reduced anchorage independent growth and had an impact on the colony morphology in 3D cell culture assays. Proteases have been frequently implicated in tumor growth and progression by shaping the extracellular environment and liberating growth factors, cytokines and chemokines. We conclude that CD24+CD90+ cells of the MMTV- PyMT mouse model possess an upregulated proteolytic signature that is likely to represent a functional hallmark of metastatic TICs of mammary carcinomas. Overall design: The transcriptome of TICs was compared with that of CD24-CD90- cancer cells by RNAseq.
Project description:Tumor cells without mitochondrial DNA (mtDNA) reconstitute oxidative phosphorylation (OXPHOS) by acquiring host mitochondria from stromal cells, but the reasons why functional respiration is crucial for tumorigenesis remain unclear. To address this issue, we used time-resolved analysis of the initial stages of tumor formation by cells devoid of mtDNA and genetic manipulations of components of OXPHOS. We show that pyrimidine biosynthesis, supported by respiration-linked dihydroorotate dehydrogenase (DHODH), is strictly required to overcome cell cycle arrest, while mitochondrial ATP generation is dispensable for tumorigenesis.
Project description:Low-oxygen stress associated with natural phenomena such as waterlogging, results in widespread transcriptome changes and a metabolic switch from aerobic respiration to anaerobic fermentation. High-throughput sequencing of small RNA libraries obtained from low-oxygen stressed and control root tissue identified a total of 65 unique microRNA (miRNA) sequences from 46 families, and 14 trans-acting small interfering RNA (tasiRNA) from 3 families. Low-oxygen stress resulted in changes to the abundance of 46 miRNAs from 19 families, and all 3 tasiRNA families. Chemical inhibition of mitochondrial respiration caused similar changes in expression in a majority of the low-oxygen responsive small RNAs analysed. Our data indicate that miRNAs and tasiRNAs play a role in gene regulation and possibly developmental responses to low oxygen, and that a major signal for these responses is likely to be dependent on mitochondrial function. Keywords: Small RNA transcriptome analysis Examination of root tissue under 2 different environments, control and low oxygen
Project description:Low-oxygen stress associated with natural phenomena such as waterlogging, results in widespread transcriptome changes and a metabolic switch from aerobic respiration to anaerobic fermentation. High-throughput sequencing of small RNA libraries obtained from low-oxygen stressed and control root tissue identified a total of 65 unique microRNA (miRNA) sequences from 46 families, and 14 trans-acting small interfering RNA (tasiRNA) from 3 families. Low-oxygen stress resulted in changes to the abundance of 46 miRNAs from 19 families, and all 3 tasiRNA families. Chemical inhibition of mitochondrial respiration caused similar changes in expression in a majority of the low-oxygen responsive small RNAs analysed. Our data indicate that miRNAs and tasiRNAs play a role in gene regulation and possibly developmental responses to low oxygen, and that a major signal for these responses is likely to be dependent on mitochondrial function. Keywords: Small RNA transcriptome analysis Overall design: Examination of root tissue under 2 different environments, control and low oxygen
Project description:To identify the regulatory mechanisms and signalling pathways involved in colorectal cancer (CRC) development, we compared the transcriptome of patient-derived tumor-initiating cells (TICs) with their normal stem cell counterparts of the same patient. This study demonstrates the relevance of AKT-signalling in colonic TIC proliferation and survival. Functional testing uncovered the selective AKT-inhibitor MK-2206 as a potential therapeutic for TIC-directed therapy in CRC. Gene expression profiling of tumor and normal tissues from 5 patients.