Inhibitors of MEK1/2 interact with UCN-01 to induce apoptosis and reduce colony formation in mammary and prostate carcinoma cells.
Recent studies have suggested that inhibition of the mitogen activated protein kinase (MAPK) pathway as well as abrogation of cell cycle check-point control can potentiate the lethal actions of chemotherapeutic drugs and radiation. We therefore investigated the impact of combined exposure to the check-point abrogator (UCN-01) in conjunction with MEK1/2 inhibitors upon survival of breast and prostate carcinoma cells. Treatment of cells with UCN-01 alone resulted in prolonged activation of the MAPK pathway. Inhibition of MEK1/2 caused modest reductions in basal MAPK activity and transiently suppressed UCN-01-stimulated MAPK activity below that of MEK1/2 inhibitor alone. Significantly, combined, but not individual, exposure of cells to UCN-01 and MEK1/2 inhibitors enhanced BAX association with mitochondria and triggered release of cytochrome c into the cytosol, accompanied by activation of effector pro-caspases, resulting in a greater than additive potentiation of apoptosis within 1 8-24h. Radiation exposure of drug treated cells did not further enhance apoptosis. Treatment of cells with both caspase 9 and caspase 8 inhibitors was required to completely inhibit apoptosis in carcinoma cells. Overexpression of Bcl-(xL) blocked cytochrome c release and cell killing induced by the drug combination. Colony forming assays demonstrated that cells exposed to both agents exhibited a substantial reduction in clonogenic survival compared to either drug alone; moreover, radiation further reduced clonogenic survival despite failing to promote additional apoptosis. Collectively, these data demonstrate that combined exposure of carcinoma cells to UCN-01 and MEK1/2 inhibitors induces apoptosis and interacts with radiation to further reduce clonogenic survival.
McKinstry
Robert
R
Department of Radiation Oncology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
Qiao
Liang
L
Yacoub
Adly
A
Dai
Yun
Y
Decker
Roy
R
Holt
Shawn
S
Hagan
Michael P
MP
Grant
Steven
S
Dent
Paul
P
D000470:Alkaloids / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D001943:Breast Neoplasms / Q000201:enzymology / Q000473:pathology*; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D002455:Cell Division / Q000187:drug effects / Q000528:radiation effects; D003114:Colony-Forming Units Assay; D003574:Cytochrome c Group / Q000378:metabolism; D004357:Drug Synergism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020287:In Situ Nick-End Labeling; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000528:radiation effects; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000528:radiation effects; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D019311:Staurosporine / Q000031:analogs & derivatives; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D014407:Tumor Cells, Cultured
D000470:Alkaloids; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D005419:Flavonoids; C054852:7-hydroxystaurosporine; C482128:MAP2K2 protein, human; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D020169:Caspases; D019311:Staurosporine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one