title: Inhibitors of MEK1/2 interact with UCN-01 to induce apoptosis and reduce colony formation in mammary and prostate carcinoma cells.
abstract: 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.
authors.affiliation: Department of Radiation Oncology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: McKinstry
authors.forename: Liang
authors.initials: L
authors.lastname: Qiao
authors.forename: Adly
authors.initials: A
authors.lastname: Yacoub
authors.forename: Yun
authors.initials: Y
authors.lastname: Dai
authors.forename: Roy
authors.initials: R
authors.lastname: Decker
authors.forename: Shawn
authors.initials: S
authors.lastname: Holt
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hagan
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
mesh_terms: 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
chemical_list: 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