title: Transient exposure of carcinoma cells to RAS/MEK inhibitors and UCN-01 causes cell death in vitro and in vivo.
abstract: The present studies were initiated to determine in greater molecular detail how MEK1/2 inhibitors [PD184352 and AZD6244 (ARRY-142886)] interact with UCN-01 (7-hydroxystaurosporine) to kill mammary carcinoma cells in vitro and radiosensitize mammary tumors in vitro and in vivo and whether farnesyl transferase inhibitors interact with UCN-01 to kill mammary carcinoma cells in vitro and in vivo. Expression of constitutively activated MEK1 EE or molecular suppression of JNK and p38 pathway signaling blocked MEK1/2 inhibitor and UCN-01 lethality, effects dependent on the expression of BAX, BAK, and, to a lesser extent, BIM and BID. In vitro colony formation studies showed that UCN-01 interacted synergistically with the MEK1/2 inhibitors PD184352 or AZD6244 and the farnesyl transferase inhibitors FTI277 and R115,777 to kill human mammary carcinoma cells. Athymic mice carrying approximately 100 mm(3) MDA-MB-231 cell tumors were subjected to a 2-day exposure of either vehicle, R115,777 (100 mg/kg), the MEK1/2 inhibitor PD184352 (25 mg/kg), UCN-01 (0.2 mg/kg), or either of the drugs in combination with UCN-01. Transient exposure of tumors to R115,777, PD184352, or UCN-01 did not significantly alter tumor growth rate or the mean tumor volume in vivo approximately 15 to 30 days after drug administration. In contrast, combined treatment with R115,777 and UCN-01 or with PD184352 and UCN-01 significantly reduced tumor growth. Tumor cells isolated after combined drug exposure exhibited a significantly greater reduction in plating efficiency using ex vivo colony formation assays than tumor cells that were exposed to either drug individually. Irradiation of mammary tumors after drug treatment, but not before or during treatment, significantly enhanced the lethal effects of UCN-01 and MEK1/2 inhibitor treatment. These findings argue that UCN-01 and multiple inhibitors of the RAS-MEK pathway have the potential to suppress mammary tumor growth, and to interact with radiation, in vitro and in vivo.
authors.affiliation: Department of Biochemistry, Virginia Commonwealth University, Richmond VA 23298-0035, USA.
authors.forename: Hossein
authors.initials: H
authors.lastname: Hamed
authors.forename: William
authors.initials: W
authors.lastname: Hawkins
authors.forename: Clint
authors.initials: C
authors.lastname: Mitchell
authors.forename: Donna
authors.initials: D
authors.lastname: Gilfor
authors.forename: Guo
authors.initials: G
authors.lastname: Zhang
authors.forename: Xin-Yan
authors.initials: XY
authors.lastname: Pei
authors.forename: Yun
authors.initials: Y
authors.lastname: Dai
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hagan
authors.forename: John D
authors.initials: JD
authors.lastname: Roberts
authors.forename: Adly
authors.initials: A
authors.lastname: Yacoub
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
mesh_terms: D015153:Blotting, Western; D016923:Cell Death / Q000187:drug effects*; D045744:Cell Line, Tumor; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007150:Immunohistochemistry; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D019311:Staurosporine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D047428:Protein Kinase Inhibitors; C054852:7-hydroxystaurosporine; D048369:MAP Kinase Kinase 1; D019311:Staurosporine