title: Targeting cancer stem cell propagation with palbociclib, a CDK4/6 inhibitor: Telomerase drives tumor cell heterogeneity.
abstract: In this report, we systematically examined the role of telomerase activity in lung and ovarian cancer stem cell (CSC) propagation. For this purpose, we indirectly gauged telomerase activity, by linking the hTERT-promoter to eGFP. Using lung (A549) and ovarian (SKOV3) cancer cells, transduced with the hTERT-GFP reporter, we then employed GFP-expression levels to fractionate these cell lines into GFP-high and GFP-low populations. We functionally compared the phenotype of these GFP-high and GFP-low populations. More specifically, we now show that the cancer cells with higher telomerase activity (GFP-high) are more energetically activated, with increased mitochondrial mass and function, as well as increased glycolytic activity. This was further validated and confirmed by unbiased proteomics analysis. Cells with high telomerase activity also showed an increased capacity for stem cell activity (as measured using the 3D-spheroid assay) and cell migration (as measured using a Boyden chamber approach). These enhanced biological phenotypes were effectively inhibited by classical modulators of energy metabolism, which target either i) mitochondrial metabolism (i.e., oligomycin) or ii) glycolysis (i.e., 2-deoxy-glucose), or iii) by using the FDA-approved antibiotic doxycycline, which inhibits mitochondrial biogenesis. Finally, the level of telomerase activity also determined the ability of hTERT-high cells to proliferate, as assessed by measuring DNA synthesis via EdU incorporation. Consistent with these observations, treatment with an FDA-approved CDK4/6 inhibitor (PD-0332991/palbociclib) specifically blocked the propagation of both lung and ovarian CSCs. Virtually identical results were obtained with breast CSCs, which were also highly sensitive to palbociclib at concentrations in the nanomolar range. In summary, CSCs with high telomerase activity are among the most energetically activated, migratory and proliferative cell sub-populations. These observations may provide a mechanistic explanation for tumor metabolic heterogeneity, based on telomerase activity. FDA-approved drugs, such as doxycycline and palbociclib, were both effective at curtailing CSC propagation. Thus, these FDA-approved drugs could be used to target telomerase-high proliferative CSCs, in multiple cancer types. Finally, our experiments also allowed us to distinguish two different cellular populations of hTERT-high cells, one that was proliferative (i.e., replicative immortality) and the other that was non-proliferative (i.e., quiescent). We speculate that the non-proliferative population of hTERT-high cells that we identified could be mechanistically involved in tumor dormancy.
authors.affiliation: Paterson Building, University of Manchester, Manchester M20 4BX, United Kingdom.
authors.forename: Gloria
authors.initials: G
authors.lastname: Bonuccelli
authors.affiliation: Paterson Building, University of Manchester, Manchester M20 4BX, United Kingdom.
authors.forename: Maria
authors.initials: M
authors.lastname: Peiris-Pages
authors.affiliation: Paterson Building, University of Manchester, Manchester M20 4BX, United Kingdom.
authors.forename: Bela
authors.initials: B
authors.lastname: Ozsvari
authors.affiliation: The Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: Ubaldo E
authors.initials: UE
authors.lastname: Martinez-Outschoorn
authors.affiliation: Translational Medicine, School of Environment and Life Sciences, Biomedical Research Centre (BRC), University of Salford, Greater Manchester, M5 4WT, United Kingdom.
authors.forename: Federica
authors.initials: F
authors.lastname: Sotgia
authors.affiliation: Translational Medicine, School of Environment and Life Sciences, Biomedical Research Centre (BRC), University of Salford, Greater Manchester, M5 4WT, United Kingdom.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Lisanti
mesh_terms: D000072283:A549 Cells; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D051358:Cyclin-Dependent Kinase 4 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051361:Cyclin-Dependent Kinase 6 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D010641:Phenotype; D010879:Piperazines / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D040901:Proteomics / Q000379:methods; D011725:Pyridines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014161:Transduction, Genetic
chemical_list: D000970:Antineoplastic Agents; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011725:Pyridines; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; C509186:TERT protein, human; D019098:Telomerase; C500026:palbociclib
keywords: cancer stem-like cells (CSCs); doxycycline; mitochondria; palbociclib; telomerase; tumor dormancy