Mitotic catastrophe induced in HeLa cells by photodynamic treatment with Zn(II)-phthalocyanine.

Photodynamic therapy (PDT) is a tool against neoplastic and non-neoplastic diseases. PDT is capable to induce different cell death mechanisms in vitro, triggered in a dose-dependent manner. Relationships between PDT and apoptosis or necrosis induction are well-known, but other cell death mechanisms triggered after PDT are less understood. Here we present our results in p53-deficient human cervix carcinoma HeLa cells subjected to sublethal PDT treatments (mortality about 40%) using Zn(II)-phthalocyanine (ZnPc) incorporated into liposomes. We obtained a rapid metaphase blockage of cells that also showed clearly altered configurations of the mitotic spindle. Cell cycle arrest was followed by aneuploidisation and cell death with apoptotic morphology. Apoptosis was also confirmed by occurrence of PARP cleavage and Bax translocation to mitochondria. These features are components of the cell death mechanism known as mitotic catastrophe and represent, to our knowledge, the first description of this cell death modality after PDT with ZnPc.