In vitro and in vivo radiosensitization with AZD6244 (ARRY-142886), an inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 kinase.
OBJECTIVE
The mitogen-activated protein (MAP) kinase pathway is important for cell proliferation, survival, and differentiation, and is frequently up-regulated in cancers. The MAP kinase pathway is also activated after exposure to ionizing radiation. We investigated the effects of AZD6244 (ARRY-142886), an inhibitor of MAP kinase/extracellular signal-regulated kinase 1/2, on radiation response.


METHODS
The effects of AZD6244 on the in vitro radiosensitivity of human cancer cell lines (A549, MiaPaCa2, and DU145) were evaluated using clonogenic assays. DNA damage repair was evaluated using gammaH2AX, and mitotic catastrophe was measured using nuclear fragmentation. Cell cycle effects were measured with flow cytometry. Growth delay was used to evaluate the effects of AZD6244 on in vivo tumor radiosensitivity.


RESULTS
Exposure of each cell line to AZD6244 before irradiation resulted in an increase in radiosensitivity with dose enhancement factors at a surviving fraction of 0.1, ranging from 1.16 to 2.0. No effects of AZD6244 on radiation-induced apoptosis or persistence of gammaH2AX foci after irradiation were detected. Cells treated with AZD6244 had an increased mitotic index and decreased Chk1 phosphorylation at 1 and 2 hours after irradiation. Mitotic catastrophe was increased in cells receiving AZD6244 and irradiation compared with the single treatments. In vivo studies revealed that AZD6244 administration to mice bearing A549 tumor xenografts resulted in a greater than additive increase in radiation-induced tumor growth delay (dose enhancement factor of 3.38).


CONCLUSIONS
These results indicate that AZD6244 can enhance tumor cell radiosensitivity in vitro and in vivo and suggest that this effect involves an increase in mitotic catastrophe.
Office of the Director, NIH, Bethesda, MD, USA.
Eun Joo
EJ
Chung
Aaron P
AP
Brown
Hiroaki
H
Asano
Mariana
M
Mandler
William E
WE
Burgan
Donna
D
Carter
Kevin
K
Camphausen
Deborah
D
Citrin
D000230:Adenocarcinoma / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D001562:Benzimidazoles / Q000494:pharmacology*; D015153:Blotting, Western; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D066298:In Vitro Techniques; D008175:Lung Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D008297:Male; D051379:Mice; D008819:Mice, Nude; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D014410:Tumor Stem Cell Assay; D014965:X-Rays; D023041:Xenograft Model Antitumor Assays
C517975:AZD 6244; D001562:Benzimidazoles; D011838:Radiation-Sensitizing Agents; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases