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Open Access Highly Accessed Research article

WEE1 inhibition sensitizes osteosarcoma to radiotherapy

Jantine PosthumaDeBoer1, Thomas Würdinger23, Harm CA Graat1, Victor W van Beusechem4, Marco N Helder15, Barend J van Royen15 and Gertjan JL Kaspers6*

Author Affiliations

1 Department of Orthopaedic Surgery, VU University Medical Center, PO box 7057, 1007 MB Amsterdam, the Netherlands

2 Neuro-oncology Research Group, Departments of Neurosurgery and Paediatric Oncology/Haematology, VU University Medical Center, PO box 7057, 1007 MB Amsterdam, the Netherlands

3 Molecular Neurogenetics Unit, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, 13th Street, Building 149, Charlestown, MA, 02129 USA

4 Department of Medical Oncology, RNA Interference Functional Oncogenomics Laboratory (RIFOL), VU University Medical Center, Amsterdam, the Netherlands

5 Research institute MOVE/Skeletal Tissue Engineering Group Amsterdam (STEGA), PO box 7057, 1007 MB Amsterdam, the Netherlands

6 Paediatric Oncology/Haematology, VU University Medical Center, PO box 7057, 1007 MB Amsterdam, the Netherlands

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BMC Cancer 2011, 11:156  doi:10.1186/1471-2407-11-156

Published: 29 April 2011

Abstract

Background

The use of radiotherapy in osteosarcoma (OS) is controversial due to its radioresistance. OS patients currently treated with radiotherapy generally are inoperable, have painful skeletal metastases, refuse surgery or have undergone an intralesional resection of the primary tumor. After irradiation-induced DNA damage, OS cells sustain a prolonged G2 cell cycle checkpoint arrest allowing DNA repair and evasion of cell death. Inhibition of WEE1 kinase leads to abrogation of the G2 arrest and could sensitize OS cells to irradiation induced cell death.

Methods

WEE1 expression in OS was investigated by gene-expression data analysis and immunohistochemistry of tumor samples. WEE1 expression in OS cell lines and human osteoblasts was investigated by Western blot. The effect of WEE1 inhibition on the radiosensitivity of OS cells was assessed by cell viability and caspase activation analyses after combination treatment. The presence of DNA damage was visualized using immunofluorescence microscopy. Cell cycle effects were investigated by flow cytometry and WEE1 kinase regulation was analyzed by Western blot.

Results

WEE1 expression is found in the majority of tested OS tissue samples. Small molecule drug PD0166285 inhibits WEE1 kinase activity. In the presence of WEE1-inhibitor, irradiated cells fail to repair their damaged DNA, and show higher levels of caspase activation. The inhibition of WEE1 effectively abrogates the irradiation-induced G2 arrest in OS cells, forcing the cells into premature, catastrophic mitosis, thus enhancing cell death after irradiation treatment.

Conclusion

We show that PD0166285, a small molecule WEE1 kinase inhibitor, can abrogate the G2 checkpoint in OS cells, pushing them into mitotic catastrophe and thus sensitizing OS cells to irradiation-induced cell death. This suggests that WEE1 inhibition may be a promising strategy to enhance the radiotherapy effect in patients with OS.