title: Reduced expression of Rho guanine nucleotide dissociation inhibitor-alpha modulates the cytotoxic effect of busulfan in HEK293 cells.
abstract: High-dose busulfan is an important component in many conditioning protocols for hematopoietic stem cell or bone marrow transplantation. Treatment with busulfan results in the inhibition of cell cycle progression and apoptosis of tumor cells. As Rho GTPases are involved in cell cycle regulation, we investigated the influence of modified Rho guanine nucleotide dissociation inhibitor-alpha (GDI), a physiological inhibitor of Rho GTPases, on busulfan activity in cancer cells. RhoGDIalpha has been shown to be overexpressed in multiple types of tumors such as ovarian and breast cancer. To investigate the role of RhoGDIalpha, we established a RhoGDIalpha knockdown by the transient transfection of HEK293 cells with specific small interfering RNA resulting in strongly reduced RhoGDIalpha mRNA and protein expression. Other members of the RhoGDI family such as RhoGDIbeta and RhoGDIgamma were not affected. In RhoGDIalpha knockdown cells, cell cycle regulation was not altered by the downregulation of RhoGDIalpha; however, the rate of apoptotic cells increased when compared with the control small interfering RNA-transfected cells. In addition, treatment of cells with busulfan resulted in a further increased apoptotic rate, as determined by fluorescence-activated cell sorter analysis and caspase-3 activation. Such a sensitization of RhoGDIalpha small interfering RNA transfected cells was also found upon treatment with doxorubicin and taxol. In summary, we could demonstrate that the expression of RhoGDIalpha influences the sensitivity of cells toward busulfan-induced cytotoxicity.
authors.affiliation: Department of Pharmacology, Research Center of Pharmacology and Experimental Therapeutics, Ernst Moritz Arndt University, Greifswald, Germany.
authors.forename: Janka
authors.initials: J
authors.lastname: Reimer
authors.forename: Sandra
authors.initials: S
authors.lastname: Bien
authors.forename: Jürgen
authors.initials: J
authors.lastname: Sonnemann
authors.forename: James F
authors.initials: JF
authors.lastname: Beck
authors.forename: Thomas
authors.initials: T
authors.lastname: Wieland
authors.forename: Heyo K
authors.initials: HK
authors.lastname: Kroemer
authors.forename: Christoph A
authors.initials: CA
authors.lastname: Ritter
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D015153:Blotting, Western; D002066:Busulfan / Q000494:pharmacology*; D053148:Caspase 3 / Q000096:biosynthesis; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D004790:Enzyme Induction / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000096:biosynthesis*; D006801:Humans; D012334:RNA, Neoplasm / Q000096:biosynthesis; D034741:RNA, Small Interfering; D013050:Spectrometry, Fluorescence; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: C569638:ARHGDIA protein, human; D018906:Antineoplastic Agents, Alkylating; D020730:Guanine Nucleotide Dissociation Inhibitors; D012334:RNA, Neoplasm; D034741:RNA, Small Interfering; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D053148:Caspase 3; D020741:rho GTP-Binding Proteins; D002066:Busulfan