title: Dissecting tumor metabolic heterogeneity: Telomerase and large cell size metabolically define a sub-population of stem-like, mitochondrial-rich, cancer cells.
abstract: Tumor cell metabolic heterogeneity is thought to contribute to tumor recurrence, distant metastasis and chemo-resistance in cancer patients, driving poor clinical outcome. To better understand tumor metabolic heterogeneity, here we used the MCF7 breast cancer line as a model system to metabolically fractionate a cancer cell population. First, MCF7 cells were stably transfected with an hTERT-promoter construct driving GFP expression, as a surrogate marker of telomerase transcriptional activity. To enrich for immortal stem-like cancer cells, MCF7 cells expressing the highest levels of GFP (top 5%) were then isolated by FACS analysis. Notably, hTERT-GFP(+) MCF7 cells were significantly more efficient at forming mammospheres (i.e., stem cell activity) and showed increased mitochondrial mass and mitochondrial functional activity, all relative to hTERT-GFP(-) cells. Unbiased proteomics analysis of hTERT-GFP(+) MCF7 cells directly demonstrated the over-expression of 33 key mitochondrial proteins, 17 glycolytic enzymes, 34 ribosome-related proteins and 17 EMT markers, consistent with an anabolic cancer stem-like phenotype. Interestingly, MT-CO2 (cytochrome c oxidase subunit 2; Complex IV) expression was increased by >20-fold. As MT-CO2 is encoded by mt-DNA, this finding is indicative of increased mitochondrial biogenesis in hTERT-GFP(+) MCF7 cells. Importantly, most of these candidate biomarkers were transcriptionally over-expressed in human breast cancer epithelial cells in vivo. Similar results were obtained using cell size (forward/side scatter) to fractionate MCF7 cells. Larger stem-like cells also showed increased hTERT-GFP levels, as well as increased mitochondrial mass and function. Thus, this simple and rapid approach for the enrichment of immortal anabolic stem-like cancer cells will allow us and others to develop new prognostic biomarkers and novel anti-cancer therapies, by specifically and selectively targeting this metabolic sub-population of aggressive cancer cells. Based on our proteomics and functional analysis, FDA-approved inhibitors of protein synthesis and/or mitochondrial biogenesis, may represent novel treatment options for targeting these anabolic stem-like cancer cells.
authors: The Breast Cancer Now Research Unit, Institute of Cancer Sciences, University of Manchester, Manchester, UK.|The Manchester Centre for Cellular Metabolism (MCCM), Institute of Cancer Sciences, University of Manchester, Manchester, UK.
authors: Rebecca
authors: R
authors: Lamb
authors: The Breast Cancer Now Research Unit, Institute of Cancer Sciences, University of Manchester, Manchester, UK.|The Manchester Centre for Cellular Metabolism (MCCM), Institute of Cancer Sciences, University of Manchester, Manchester, UK.
authors: Bela
authors: B
authors: Ozsvari
authors: The Breast Cancer Now Research Unit, Institute of Cancer Sciences, University of Manchester, Manchester, UK.|The Manchester Centre for Cellular Metabolism (MCCM), Institute of Cancer Sciences, University of Manchester, Manchester, UK.
authors: Gloria
authors: G
authors: Bonuccelli
authors: The Cancer Research UK Manchester Institute, University of Manchester, Manchester, UK.
authors: Duncan L
authors: DL
authors: Smith
authors: The Sidney Kimmel Cancer Center, Philadelphia, PA, USA.
authors: Richard G
authors: RG
authors: Pestell
authors: The Sidney Kimmel Cancer Center, Philadelphia, PA, USA.
authors: Ubaldo E
authors: UE
authors: Martinez-Outschoorn
authors: The Breast Cancer Now Research Unit, Institute of Cancer Sciences, University of Manchester, Manchester, UK.
authors: Robert B
authors: RB
authors: Clarke
authors: The Breast Cancer Now Research Unit, Institute of Cancer Sciences, University of Manchester, Manchester, UK.|The Manchester Centre for Cellular Metabolism (MCCM), Institute of Cancer Sciences, University of Manchester, Manchester, UK.
authors: Federica
authors: F
authors: Sotgia
authors: The Breast Cancer Now Research Unit, Institute of Cancer Sciences, University of Manchester, Manchester, UK.|The Manchester Centre for Cellular Metabolism (MCCM), Institute of Cancer Sciences, University of Manchester, Manchester, UK.
authors: Michael P
authors: MP
authors: Lisanti
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology*; D040901:Proteomics / Q000379:methods; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D014408:Biomarkers, Tumor; C509186:TERT protein, human; D019098:Telomerase
keywords: cancer stem cells; cell size; hTERT; mitochondrial biogenesis; proteomic analysis; telomerase; tumor metabolism