Inhibition of the kinase Wee1 - Cytotoxic mechanisms and autoprotection by the tumor suppressor p53
von Yizhu Li
Datum der mündl. Prüfung:2017-11-22
Erschienen:2017-10-27
Betreuer:Prof. Dr. Matthias Dobbelstein
Gutachter:Prof. Dr. Holger Reichardt
Gutachter:Prof. Dr. Blanche Schwappach
Gutachter:Prof. Dr. Margarete Schön
Dateien
Name:DissertationYizhuLi2017.pdf
Size:3.89Mb
Format:PDF
Zusammenfassung
Englisch
The combination of the Wee1 inhibitor MK-1775 and gemcitabine is highly efficient in killing cancer cells in vitro and in mouse xenograft experiments, but the complete molecular mechanism of this potent sensitizing effect remains unknown. We found that MK-1775 does not only block Wee1 activity in gemcitabine treated cells, but also reduces the activation of the ATR/Chk1 pathway in a Cyclin-dependent kinase 1 (Cdk1) dependent manner. These findings suggest that Wee1 inhibitors do not only interfere with cell cycle checkpoints to force cell cycle progression, but also to enhance replicative stress and intensify chemosensitivity towards nucleoside analogues through Chk1 inhibition and replicative stress, making them interesting therapeutic agent candidates for clinical oncology. However, considerable MK-1775 toxicities have been observed in preclinical as well as in clinical trials. Over 50% of all cancers carry a mutation in the TP53 gene. Using the MDM2-antagonist Nutlin-3a, we provide a selective protection of p53-proficient cells against the cytotoxic effects of Wee1 inhibitors. Pretreatment of p53 wildtype cells with Nutlin-3a results in a transient cell cycle arrest, which effectively benefits cell survival upon subsequent treatment with the combination of the Wee1 inhibitor MK-1775 and gemcitabine. Nutlin-3a pretreatment reduced both the DNA damage response, as well as caspase activation in a p53-dependent manner. MDM2 antagonists might therefore selectively protect p53-proficient cells against the cytotoxic effects of Wee1 inhibitors, especially when combined with an S-phase specific drug, such as the nucleoside analogue gemcitabine. This approach might help to avoid toxic side effects of Wee1 inhibitors in anticipated clinical applications.
Keywords: Wee1 kinase; p53 tumor suppressor; cell cycle; chemotherapy