Inhibition of Chk1 by CEP-3891 accelerates mitotic nuclear fragmentation in response to ionizing Radiation.

TY - JOUR

T1 - Inhibition of Chk1 by CEP-3891 accelerates mitotic nuclear fragmentation in response to ionizing Radiation.

AU - Syljuåsen, Randi G

AU - Sørensen, Claus Storgaard

AU - Nylandsted, Jesper

AU - Lukas, Claudia

AU - Lukas, Jiri

AU - Bartek, Jiri

N1 - Keywords: Apoptosis; Bone Neoplasms; Cell Line, Tumor; Cell Nucleus; Cell Survival; G2 Phase; Humans; Mitosis; Osteosarcoma; Protein Kinase Inhibitors; Protein Kinases; Radiation-Sensitizing Agents; S Phase

PY - 2004

Y1 - 2004

N2 - The human checkpoint kinase Chk1 has been suggested as a target for cancer treatment. Here, we show that a new inhibitor of Chk1 kinase, CEP-3891, efficiently abrogates both the ionizing radiation (IR)-induced S and G(2) checkpoints. When the checkpoints were abrogated by CEP-3891, the majority (64%) of cells showed fragmented nuclei at 24 hours after IR (6 Gy). The formation of nuclear fragmentation in IR-treated human cancer cells was directly visualized by time-lapse video microscopy of U2-OS cells expressing a green fluorescent protein-tagged histone H2B protein. Nuclear fragmentation occurred as a result of defective chromosome segregation when irradiated cells entered their first mitosis, either prematurely without S and G(2) checkpoint arrest in the presence of CEP-3891 or after a prolonged S and G(2) checkpoint arrest in the absence of CEP-3891. The nuclear fragmentation was clearly distinguishable from apoptosis because caspase activity and nuclear condensation were not induced. Finally, CEP-3891 not only accelerated IR-induced nuclear fragmentation, it also increased the overall cell killing after IR as measured in clonogenic survival assays. These results demonstrate that transient Chk1 inhibition by CEP-3891 allows premature mitotic entry of irradiated cells, thereby leading to accelerated onset of mitotic nuclear fragmentation and increased cell death.

AB - The human checkpoint kinase Chk1 has been suggested as a target for cancer treatment. Here, we show that a new inhibitor of Chk1 kinase, CEP-3891, efficiently abrogates both the ionizing radiation (IR)-induced S and G(2) checkpoints. When the checkpoints were abrogated by CEP-3891, the majority (64%) of cells showed fragmented nuclei at 24 hours after IR (6 Gy). The formation of nuclear fragmentation in IR-treated human cancer cells was directly visualized by time-lapse video microscopy of U2-OS cells expressing a green fluorescent protein-tagged histone H2B protein. Nuclear fragmentation occurred as a result of defective chromosome segregation when irradiated cells entered their first mitosis, either prematurely without S and G(2) checkpoint arrest in the presence of CEP-3891 or after a prolonged S and G(2) checkpoint arrest in the absence of CEP-3891. The nuclear fragmentation was clearly distinguishable from apoptosis because caspase activity and nuclear condensation were not induced. Finally, CEP-3891 not only accelerated IR-induced nuclear fragmentation, it also increased the overall cell killing after IR as measured in clonogenic survival assays. These results demonstrate that transient Chk1 inhibition by CEP-3891 allows premature mitotic entry of irradiated cells, thereby leading to accelerated onset of mitotic nuclear fragmentation and increased cell death.

U2 - 10.1158/0008-5472.CAN-04-2434

DO - 10.1158/0008-5472.CAN-04-2434

M3 - Journal article

C2 - 15604269

SN - 0008-5472

VL - 64

SP - 9035

EP - 9040

JO - Cancer Research

JF - Cancer Research

IS - 24

ER -