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Identification of differentially expressed miRNAs in hypoxic tumor-initiating cell (TIC) cultures

ABSTRACT: Patient-derived TIC cultures T6 and T18 were used to study the effect of normoxic vs. hypoxic culture conditions The main focus of the study was the identification and validation of new hypoxia-responsive miRNAs and target genes in such colon TICs

ORGANISM(S): synthetic construct Homo sapiens

PROVIDER: GSE120424 | GEO | 2019/09/17

REPOSITORIES: GEO

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Project description: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.

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Identification of differentially expressed miRNAs in hypoxic tumor-initiating cell (TIC) cultures

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