The c-Met receptor tyrosine kinase inhibitor MP470 radiosensitizes glioblastoma cells.
OBJECTIVE
Glioblastoma multiforme (GBM) is resistant to current cytotoxic therapies, in part because of enhanced DNA repair. Activation of the receptor tyrosine kinase c-Met has been shown to protect cancer cells from DNA damage. We hypothesized that inhibiting c-Met would decrease this protection and thus sensitize resistant tumor cells to the effects of radiation therapy.


METHODS
Eight human GBM cell lines were screened for radiosensitivity to the small-molecule c-Met inhibitor MP470 with colony-count assays. Double-strand (ds) DNA breaks was quantified by using antibodies to gamma H2AX. Western blotting demonstrate expression of RAD51, glycogen synthase kinase (GSK)-3beta, and other proteins. A murine xenograft tumor flank model was used for in vivo radiosensitization studies.


RESULTS
MP470 reduced c-Met phosphorylation and enhanced radiation-induced cell kill by 0.4 logs in SF767 cells. Cells pretreated with MP470 had more ds DNA damage than cells treated with radiation alone. Mechanistically, MP470 was shown to inhibit dsDNA break repair and increase apoptosis. MP470 influences various survival and DNA repair related proteins such as pAKT, RAD51 and GSK3beta. In vivo, the addition of MP470 to radiation resulted in a tumor-growth-delay enhancement ratio of 2.9 over radiation alone and extended survival time.


CONCLUSIONS
GBM is a disease site where radiation is often used to address both macroscopic and microscopic disease. Despite attempts at dose escalation outcomes remain poor. MP470, a potent small-molecule tyrosine kinase inhibitor of c-Met, radiosensitized several GBM cell lines both in vitro and in vivo, and may help to improve outcomes for patients with GBM.
Welsh
James W
JW
Departmentr of Radiation Oncology, The University of Texas M, D, Anderson Cancer Center, 1515 Holcombe Blvd,, Houston, TX, USA. jwelsh@mdanderson.org
Mahadevan
Daruka
D
Ellsworth
Ron
R
Cooke
Laurence
L
Bearss
David
D
Stea
Baldassarre
B
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D020552:Comet Assay; D053903:DNA Breaks, Double-Stranded; D005909:Glioblastoma / Q000378:metabolism*; D006801:Humans; D051379:Mice; D010879:Piperazines; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors; D011743:Pyrimidines / Q000494:pharmacology*; D034741:RNA, Small Interfering; D011836:Radiation Tolerance / Q000187:drug effects*; D013890:Thiourea; D023041:Xenograft Model Antitumor Assays
D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D034741:RNA, Small Interfering; D019859:Proto-Oncogene Proteins c-met; D013890:Thiourea; C521047:amuvatinib