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Research Article

Senescent Cells in Growing Tumors: Population Dynamics and Cancer Stem Cells

  • Caterina A. M. La Porta,

    Affiliation: Department of Biomolecular Science and Biotechnology, University of Milano, Milano, Italy

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  • Stefano Zapperi mail,

    stefano.zapperi@cnr.it

    Affiliations: CNR-IENI, Milano, Italy, ISI Foundation, Torino, Italy

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  • James P. Sethna

    Affiliation: LASSP, Department of Physics, Cornell University, Ithaca, New York, United States of America

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  • Published: January 19, 2012
  • DOI: 10.1371/journal.pcbi.1002316

Reader Comments (1)

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Senescence reversion

Posted by gulenz on 07 Aug 2012 at 18:08 GMT

The term senescence reversion should be used with care, since it might erroneously indicate that a cell after reaching senescence, returned to a proliferating state. This, to my knowledge, was never shown and would require single cell analysis. Populational "reversion" of senescence, in which a large number of cells has a high level of senescence and after a treatment the level is reduced is most likely due to the elimination of the senescent cells and the domination of the population by the proliferating cells. This, in my oppinion, should not be called reversion, but rather referred to as reduction in or blockage of senescence induction.

No competing interests declared.

RE: Senescence reversion

zapperi replied to gulenz on 22 Aug 2012 at 15:41 GMT

We thank Dr. Lenz for his comment. We agree with him that we did not demonstrate the reversal of senescence in a single senescent cell but have only studied the effect of Survivin on cell populations. This is a meaningful remark since very often in the literature properties of single cells are inferred from population effects. A recent example is the claim, based on population dynamics, that cancer cells undergo phenotypic switching into cancer stem cells. We have challenged this claim based on similar arguments and therefore welcome the present comment.

We claimed that senescent cells could be reversed because when we overexpressed Survivin in a population with few senescent cells we saw no effect in terms of growth with respect to the GFP control. This could imply that Survivin only acts when senescent cells are present suggesting that it is the senescent cells that start to grow again. From this indirect evidence, we concluded that overexpression of Survivin is able to reverse senescence. We agree, however, that to really prove this point one should analyze single cells. We are now working to clarify this issue.

No competing interests declared.