title: Protoporphyrin IX interacts with wild-type p53 protein in vitro and induces cell death of human colon cancer cells in a p53-dependent and -independent manner.
abstract: Photodynamic therapy (PDT) of cancer is an alternative treatment for tumors resistant to chemo- and radiotherapy. It induces cancer cell death mainly through generation of reactive oxygen species by a laser light-activated photosensitizer. It has been suggested that the p53 tumor suppressor protein sensitizes some human cancer cells to PDT. However, there is still no direct evidence for this. We have demonstrated here for the first time that the photosensitizer protoporphyrin IX (PpIX) binds to p53 and disrupts the interaction between p53 tumor suppressor protein and its negative regulator HDM2 in vitro and in cells. Moreover, HCT116 colon cancer cells exhibited a p53-dependent sensitivity to PpIX in a dose-dependent manner, as was demonstrated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and fluorescence-activated cell sorter (FACS) analysis of cell cycle profiles. We have also observed induction of p53 target pro-apoptotic genes, e.g. puma (p53-up-regulated modulator of apoptosis), and bak in PpIX-treated cells. In addition, p53-independent growth suppression by PpIX was detected in p53-negative cells. PDT treatment (2 J/cm2) of HCT116 cells induced p53-dependent activation of pro-apoptotic gene expression followed by growth suppression and induction of apoptosis.
authors.affiliation: Department of Biotechnology, Division of Molecular Diagnostics, Intercollegiate Faculty of Biotechnology, University of Gdansk, Kladki 24, 80-822 Poland. jzawacka@biotech.ug.gda.pl
authors.forename: Joanna
authors.initials: J
authors.lastname: Zawacka-Pankau
authors.forename: Natalia
authors.initials: N
authors.lastname: Issaeva
authors.forename: Shakil
authors.initials: S
authors.lastname: Hossain
authors.forename: Aladdin
authors.initials: A
authors.lastname: Pramanik
authors.forename: Galina
authors.initials: G
authors.lastname: Selivanova
authors.forename: Anna J
authors.initials: AJ
authors.lastname: Podhajska
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis / Q000235:genetics; D016923:Cell Death; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D011524:Protoporphyrins / Q000378:metabolism / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000096:biosynthesis / Q000235:genetics
chemical_list: D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D017319:Photosensitizing Agents; D011518:Proto-Oncogene Proteins; D011524:Protoporphyrins; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; C028025:protoporphyrin IX