TY - JOUR
T1 - A novel Chk inhibitor, XL-844, increases human cancer cell radiosensitivity through promotion of mitotic catastrophe
AU - Riesterer, Oliver
AU - Matsumoto, Fumihiko
AU - Wang, Li
AU - Pickett, Jessica
AU - Molkentine, David
AU - Giri, Uma
AU - Milas, Luka
AU - Raju, Uma
N1 - Funding Information:
Acknowledgements This work was supported partly by Exelixis Inc., CA, USA (PI: U. Raju) and partly by a UICC ACSBI fellowship supplemented by the University of Zurich (O. Riesterer). We thank Peter Lamb Ph.D. (Exelixis Incorporation, San Francisco, CA) for his involvement in designing the experiments.
PY - 2011/6
Y1 - 2011/6
N2 - Check point kinases (Chk) play a major role in facilitating DNA repair upon radiation exposure. We tested the potency of a novel inhibitor of Chk1 and Chk2, XL-844 (provided by Exelixis Inc., CA, USA), to radiosensitize human cancer cells grown in culture and investigated the underlying mechanisms. HT-29 cells (a human colon cancer line) were exposed to XL-844, radiation, or both, and assessed for clonogenic cell survival. Treatment-dependent effects on phosphorylated forms of Chk proteins were assessed by Western blots. Further mechanistic investigations in HT-29 cells included cell cycle analysis by flowcytometry and assessment of DNA repair kinetics by immuno-cytochemistry (ICC) for nuclear appearance of the phosphorylated form of histone 2AX protein (γ-H2AX) staining. Cells undergoing mitotic catastrophe were identified by irregular pattern of mitotic spindle markers α and γ-tubulin staining by ICC. XL-844 enhanced radiosensitivity in a dose and schedule-dependent manner and the enhancement factor was 1.42 at 0.5 survival fraction. Mechanistically XL-844 abrogated radiation-induced Chk2 phosphorylation, induced pan-nuclear γ-H2AX, and prolonged the presence of radiation-induced γ-H2AX foci, and promoted mitotic catastrophe. In conclusion, our data showed that inhibition of Chk2 activity by XL-844 enhanced cancer cell radiosensitivity that was associated with inhibition of DNA repair and induction of mitotic catastrophe.
AB - Check point kinases (Chk) play a major role in facilitating DNA repair upon radiation exposure. We tested the potency of a novel inhibitor of Chk1 and Chk2, XL-844 (provided by Exelixis Inc., CA, USA), to radiosensitize human cancer cells grown in culture and investigated the underlying mechanisms. HT-29 cells (a human colon cancer line) were exposed to XL-844, radiation, or both, and assessed for clonogenic cell survival. Treatment-dependent effects on phosphorylated forms of Chk proteins were assessed by Western blots. Further mechanistic investigations in HT-29 cells included cell cycle analysis by flowcytometry and assessment of DNA repair kinetics by immuno-cytochemistry (ICC) for nuclear appearance of the phosphorylated form of histone 2AX protein (γ-H2AX) staining. Cells undergoing mitotic catastrophe were identified by irregular pattern of mitotic spindle markers α and γ-tubulin staining by ICC. XL-844 enhanced radiosensitivity in a dose and schedule-dependent manner and the enhancement factor was 1.42 at 0.5 survival fraction. Mechanistically XL-844 abrogated radiation-induced Chk2 phosphorylation, induced pan-nuclear γ-H2AX, and prolonged the presence of radiation-induced γ-H2AX foci, and promoted mitotic catastrophe. In conclusion, our data showed that inhibition of Chk2 activity by XL-844 enhanced cancer cell radiosensitivity that was associated with inhibition of DNA repair and induction of mitotic catastrophe.
KW - Inhibitor of Check point kinases
KW - Mitotic catastrophe
KW - Pan-nuclear γ-H2AX
KW - Radiosensitivity
KW - XL-844
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U2 - 10.1007/s10637-009-9361-2
DO - 10.1007/s10637-009-9361-2
M3 - Article
C2 - 20024691
AN - SCOPUS:79955623625
SN - 0167-6997
VL - 29
SP - 514
EP - 522
JO - Investigational New Drugs
JF - Investigational New Drugs
IS - 3
ER -