Targeting cancer stem cell propagation with palbociclib, a CDK4/6 inhibitor: Telomerase drives tumor cell heterogeneity

Bonuccelli, G; Peires-Pages, M; Ozsvari, B; Martinez- Outschoorn, U; Sotgia, F; Lisanti, MP

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 GFPhigh
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-deoxyglucose),
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 FDAapproved
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 FDAapproved
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.

Citation

Bonuccelli, G., Peires-Pages, M., Ozsvari, B., Martinez- Outschoorn, U., Sotgia, F., & Lisanti, M. (2017). Targeting cancer stem cell propagation with palbociclib, a CDK4/6 inhibitor: Telomerase drives tumor cell heterogeneity. Oncotarget, 8(6), 9868-9884. https://doi.org/10.18632/oncotarget.14196

• Journal Article Type: Article
• Acceptance Date: Nov 16, 2016
• Online Publication Date: Dec 25, 2016
• Publication Date: Feb 7, 2017
• Deposit Date: Mar 31, 2017
• Publicly Available Date: Mar 31, 2017
• Journal: Oncotarget
• Publisher: Impact Journals
• Volume: 8
• Issue: 6
• Pages: 9868-9884
• DOI: https://doi.org/10.18632/oncotarget.14196
• Publisher URL: http://dx.doi.org/10.18632/oncotarget.14196
• Related Public URLs: http://www.impactjournals.com/oncotarget/index.php?journal=oncotarget