[Proteasome inhibitor bortezomib sensitizes Hep-2 human laryngeal squamous cell carcinoma cells to ionizing radiation in vitro and in vivo].
OBJECTIVE
To determine if proteasome inhibitor bortezomib leads to enhanced radiation sensitivity of Hep-2 human laryngeal cancer cells and the relative mechanisms.


METHODS
Hep-2 cells with or without bortezomib were irradiated at 0, 2, 4, 6, 8, and 10 Gy. Growth and clonogenic survival data were obtained to assess effects of treatment on radiosensitization. In vitro results were tested in vivo using a Hep-2 xenograft model. Nuclear factor-kappaB (NF-kappaB) activation was determined by Trans AM NF-kappaB P65 kit. The distribution of cell cycle and apoptosis were evaluated by flow cytometry. Morphological evidence of apoptotic cells were observed with Hochest 33342.


RESULTS
It decreased cell growth and clonogenic survival. A 34% increase in radiosensitivity was observed for cells treated with bortezomib and radiation. Enhancement factor (EF) was 1.46 in Hep-2 xenografts receiving radiation and bortezomib. NF-kappaB activation was induced by radiation and inhibited by pretreatment with bortezomib, and was in a dose-dependent manner (r = 0.989, P < 0.05). Hep-2 cells treated with 100 nmol/L Bortezomib were arrested at G2-M phase (t = 22.31, P = 0.000) and resulted in all increased apoptosis with and without irradiation (P < 0.01). Morphological evidence of apoptotic cells could be distinguished under the fluorescence microscope after staining with Hochest 33342. Many nuclear fragments were observed in Hep-2 cells with bortezomib.


CONCLUSIONS
Bortezomib could enhanced the radiosensitivity of Hep-2 laryngeal cancer cells by regulation of the distribution of cell cycle.
Wang
Qing-Wei
QW
Department of Radiotherapy, Cancer Research Center, Qilu Hospital of Shandong University, Jinan 250012, China.
Liu
Hong
H
Liang
Ye-Min
YM
Wang
Tao
T
Zhu
Xu-Dong
XD
D000818:Animals; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D007822:Laryngeal Neoplasms / Q000532:radiotherapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D011719:Pyrazines / Q000494:pharmacology*; D011836:Radiation Tolerance / Q000187:drug effects*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*
D001897:Boronic Acids; D004791:Enzyme Inhibitors; D011719:Pyrazines; D011838:Radiation-Sensitizing Agents; D000069286:Bortezomib