Sequence of events leading to apoptosis in long term cultured HeLa cells

Claudia Negri, Rosa Bernardi, Maddalena Donzelli, Ennio Prosperi, A. Ivana Scovassi

Research output: Contribution to journalArticlepeer-review


We have maintained HeLa cells in culture in the original medium for increasing times to induce growth arrest. Cell viability was evaluated by trypan blue dye exclusion assay. We observed that when cells are maintained in culture for several days, morphological hallmarks of apoptosis become evident. DNA synthesis rate, followed by 3H-thymidine incorporation slowed down in long term cultured cells. This evidence was supported by the analysis of cell cycle progression determined by proliferating cell nuclear antigen (PCNA) immunostaining. Apoptotic cells have been characterized with respect to the sequential appearance of high molecular weight and internucleosomal DNA fragmentation. We have provided evidence that in this experimental model the first step in DNA degradation is represented by the formation of high molecular weight fragments, whereas nucleosomal DNA ladder is visible later on. The activation of the enzyme poly(ADP-ribose)polymerase, considered a marker of apoptotic death, has been observed. The results suggest that long term culture conditions activate the apoptotic programme.

Original languageEnglish
Pages (from-to)425-430
Number of pages6
JournalCell Death and Differentiation
Issue number4
Publication statusPublished - 1996


  • Apoptosis
  • Death commitment
  • DNA degradation
  • PCNA
  • Poly(ADP-ribosylation)

ASJC Scopus subject areas

  • Cell Biology


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