Analysis of induction of senescence-like growth arrest in glioblastoma cells by irradiation or arsenite.

Abstract

[Purpose] Gliomblastoma is one of the most common tumor types resistant to radiation. Arsenite was reported to show synergistic radiosensitization effect in vitro and in vivo. But, the mechanism of radiosensitization is not well understood. Last year, we showed the difference of mechanism of SLGA between radiation and arsenite. This year, we have studied heterochomatin formation by treatment of arsenite associated with senescence-like growth arrest (SLGA).
[Results] We performed analysis using glioblastoma U87MG cells treated by arsenite. Formation of γH2AX foci observed after 6 hours. The results indicated DNA damaged by arsenite is indirectly. Double staining using antibody of histone H3 phospholylated or methylated with γH2AX foci shows the modification of histone H3 is on the cells with γH2AX. Thus, we thought the heterochromatin formation induced by DNA damage. Next, we performed about p53 dependency of heterochromatin formation. The results show γH2AX formation and phosphorylation of histone H3 observed, but methylation of histone H3 dose not observed at p53 deficient cells.