Live-Cell Imaging Visualizes Frequent Mitotic Skipping During Senescence-Like Growth Arrest in Mammary Carcinoma Cells Exposed to Ionizing Radiation

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• 作者：Masatoshi Suzuki ; Ph.D. ; ^{msuzuki@nagasaki-u.ac.jp} ; Motohiro Yamauchi ; Ph.D. ; Yasuyoshi Oka ; M.S. ; Keiji Suzuki ; Ph.D. ; Shunichi Yamashita ; M.D. ; Ph.D.
• 关键词：Fluorescent ubiquitination-based cell cycle indicator ; Live-cell imaging ; Mammary carcinoma ; Mitotic skipping ; Senescence-like growth arrest
• 刊名：International Journal of Radiation Oncology*Biology*Physics
• 出版年：2012
• 期刊代码：136_03603016
• 类别：med
• 出版时间：1 June, 2012
• 卷：83
• 期：2
• 页码：e241-e250
• 文件大小：2108 K

摘要

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Purpose

Senescence-like growth arrest in human solid carcinomas is now recognized as the major outcome of radiotherapy. This study was designed to analyze cell cycle during the process of senescence-like growth arrest in mammary carcinoma cells exposed to X-rays.

Methods and Materials

Fluorescent ubiquitination-based cell cycle indicators were introduced into the human mammary carcinoma cell line MCF-7. Cell cycle was sequentially monitored by live-cell imaging for up to 5 days after exposure to 10 Gy of X-rays.

Results

Live-cell imaging revealed that cell cycle transition from G2 to G1 phase without mitosis, so-called mitotic skipping, was observed in 17.1%and 69.8%of G1- and G2-irradiated cells, respectively. Entry to G1 phase was confirmed by the nuclear accumulation of mKO₂-hCdt1 as well as cyclin E, which was inversely correlated to the accumulation of G2-specific markers such as mAG-hGeminin and CENP-F. More than 90%of cells skipping mitosis were persistently arrested in G1 phase and showed positive staining for the senescent biochemical marker, which is senescence-associated 脽-galactosidase, indicating induction of senescence-like growth arrest accompanied by mitotic skipping. While G2 irradiation with higher doses of X-rays induced mitotic skipping in approximately 80%of cells, transduction of short hairpin RNA (shRNA) for p53 significantly suppressed mitotic skipping, suggesting that ionizing radiation-induced mitotic skipping is associated with p53 function.

Conclusions

The present study found the pathway of senescence-like growth arrest in G1 phase without mitotic entry following G2-irradiation.