Targeting MPS1 Enhances Radiosensitization of Human Glioblastoma by Modulating DNA Repair Proteins.
To ensure faithful chromosome segregation, cells use the spindle assembly checkpoint (SAC), which can be activated in aneuploid cancer cells. Targeting the components of SAC machinery required for the growth of aneuploid cells may offer a cancer cell-specific therapeutic approach. In this study, the effects of inhibiting Monopolar spindle 1, MPS1 (TTK), an essential SAC kinase, on the radiosensitization of glioblastoma (GBM) cells were analyzed. Clonogenic survival was used to determine the effects of the MPS1 inhibitor NMS-P715 on radiosensitivity in multiple model systems, including GBM cell lines, a normal astrocyte, and a normal fibroblast cell line. DNA double-strand breaks (DSB) were evaluated using γH2AX foci, and cell death was measured by mitotic catastrophe evaluation. Transcriptome analysis was performed via unbiased microarray expression profiling. Tumor xenografts grown from GBM cells were used in tumor growth delay studies. Inhibition of MPS1 activity resulted in reduced GBM cell proliferation. Furthermore, NMS-P715 enhanced the radiosensitivity of GBM cells by decreased repair of DSBs and induction of postradiation mitotic catastrophe. NMS-P715 in combination with fractionated doses of radiation significantly enhanced the tumor growth delay. Molecular profiling of MPS1-silenced GBM cells showed an altered expression of transcripts associated with DNA damage, repair, and replication, including the DNA-dependent protein kinase (PRKDC/DNAPK). Next, inhibition of MPS1 blocked two important DNA repair pathways. In conclusion, these results not only highlight a role for MPS1 kinase in DNA repair and as prognostic marker but also indicate it as a viable option in glioblastoma therapy.


CONCLUSIONS
Inhibition of MPS1 kinase in combination with radiation represents a promising new approach for glioblastoma and for other cancer therapies.
Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland.
Uday Bhanu
UB
Maachani
Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland.
Tamalee
T
Kramp
Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland.
Ryan
R
Hanson
Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland.
Shuping
S
Zhao
Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland.
Orieta
O
Celiku
Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland.
Uma
U
Shankavaram
Nerviano Medical Sciences srl, Oncology, Nerviano, Italy.
Riccardo
R
Colombo
Genetics Branch, National Cancer Institute, NIH, Bethesda, Maryland.
Natasha J
NJ
Caplen
Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland.
Kevin
K
Camphausen
Radiation Oncology Branch, National Cancer Institute, NIH, Bethesda, Maryland. tandlea@mail.nih.gov.
Anita
A
Tandle
D000818:Animals; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D001932:Brain Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000532:radiotherapy*; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair / Q000528:radiation effects*; D005260:Female; D005909:Glioblastoma / Q000201:enzymology / Q000235:genetics* / Q000532:radiotherapy*; D006801:Humans; D008819:Mice, Nude; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance; D011897:Random Allocation; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
D018797:Cell Cycle Proteins; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human