Abstract
It has recently been shown that gamma irradiation of tumor cells induces centrosome amplification. However, the precise mechanism of radiation-induced centrosome amplification is not yet fully understood.
In the present study, CCD32SK diploid normal human fibroblasts were transiently transfected with short interfering RNA (siRNA) specific for human p53 (CCD/p53i). There was a small increase in the frequency of centrosome amplification in CCD/p53i cells (4.0%) without irradiation. In contrast, CCD/p53i cells after 5-Gy irradiation showed a marked increase in abnormal nuclear shapes and pronounced amplification of centrosomes (46.0%). At 12 h after irradiation, irradiated CCD/p53i cells were arrested in G2 phase. On laser scanning cytometry, abnormal mitosis with amplified centrosomes was frequently observed in the accumulating G2/M population at 48 h after irradiation.
In the present study, we found that siRNA-mediated silencing of p53 in normal human fibroblasts, together with DNA damage by irradiation, efficiently induces centrosome amplification and nuclear fragmentation, but these phenomena were not observed with either siRNA-mediated silencing of p53 or irradiation alone.