title: Antitumor activity of TMPyP4 interacting G-quadruplex in retinoblastoma cell lines.
abstract: To investigate the molecular mechanism of the antitumor activity of the cationic porphyrin 5, 10, 15, 20-tetra-(N-methyl-4-pyridyl)porphyrin (TMPyP4) in retinoblastoma cell lines, Y79 and WERI-Rb1 cells were treated with TMPyP4 for 0-72 h, after which growth inhibition, modulation of the cell cycle and the induction of apoptosis were examined. In addition, the effect of TMPyP4 on the susceptibility to irradiation was evaluated in Y79 and WERI-Rb1 cells. In vitro telomeric repeat amplification protocol assay showed TMPyP4 (10-100 microM) directly blocked telomerase elongation, suggesting that TMPyP4 can form stable guanine (G)-quadruplexes in extending telomere repeats in substrate oligonucleotides. The antiproliferative activities of TMPyP4 assessed with the MTS assay and expressed in terms of IC(50): Y79 cells, 60 microM; WERI-Rb1 cells, 45 microM. Treatment with TMPyP4 at doses of 10, 20, 50 or 100 microM for 48 or 72 h significantly inhibited the growth of Y79 and WERI-Rb1 cells. Apoptosis, as assessed with CaspACE FITC-VAD-FMK, was induced by TMPyP4 in a dose-dependent manner. Induction of apoptosis by TMPyP4 was associated with increased expression of phosphorylated DNA damage response factor H2AX (Ser139), phosphorylated p53 (Ser46) protein and activation of mitogen-activated protein kinases in Y79 and WERI-Rb1 cells. Moreover, TMPyP4 significantly enhanced the susceptibility to irradiation in both cell lines. This study provides insight into the molecular mechanism of the antitumor effects of TMPyP4. G-quadruplex structure may be a potential therapeutic target in retinoblastoma.
authors.affiliation: Department of Pediatrics, Jikei University School of Medicine, Tokyo 105-8461, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mikami-Terao
authors.forename: Masaharu
authors.initials: M
authors.lastname: Akiyama
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yuza
authors.forename: Takaaki
authors.initials: T
authors.lastname: Yanagisawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Yamada
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawano
authors.forename: Miyuki
authors.initials: M
authors.lastname: Agawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ida
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yamada