title: Suppression of RAD21 gene expression decreases cell growth and enhances cytotoxicity of etoposide and bleomycin in human breast cancer cells.
abstract: A genome-wide case-control association study done in our laboratory has identified a single nucleotide polymorphism located in RAD21 as being significantly associated with breast cancer susceptibility. RAD21 is believed to function in sister chromatid alignment as part of the cohesin complex and also in double-strand break (DSB) repair. Following our initial finding, expression studies revealed a 1.25- to 2.5-fold increased expression of this gene in several human breast cancer cell lines as compared with normal breast tissue. To determine whether suppression of RAD21 expression influences cellular proliferation, RNA interference technology was used in breast cancer cell lines MCF-7 and T-47D. Proliferation of cells treated with RAD21-specific small inhibitory RNA (siRNA) was significantly reduced as compared with mock-transfected cells and cells transfected with a control siRNA (Lamin A/C). This inhibition of proliferation correlated with a significant reduction in the expression of RAD21 mRNA and with an increased level of apoptosis. Moreover, MCF-7 cell sensitivity to two DNA-damaging chemotherapeutic agents, etoposide and bleomycin, was increased after inhibition of RAD21 expression with a dose reduction factor 50 (DRF50) of 1.42 and 3.71, respectively. At the highest concentrations of etoposide and bleomycin administered, cells transfected with a single siRNA duplex targeted against RAD21 showed 57% and 60% survival as compared with control cells, respectively. Based on these findings, we conclude that RAD21 is a novel target for developing cancer therapeutics that can potentially enhance the antitumor activity of chemotherapeutic agents acting via induction of DNA damage.
authors.affiliation: Sequenom, Inc., 3595 John Hopkins Court, San Diego, CA 92121, USA.
authors.forename: Josephine M
authors.initials: JM
authors.lastname: Atienza
authors.forename: Richard B
authors.initials: RB
authors.lastname: Roth
authors.forename: Caridad
authors.initials: C
authors.lastname: Rosette
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Smylie
authors.forename: Stefan
authors.initials: S
authors.lastname: Kammerer
authors.forename: Joachim
authors.initials: J
authors.lastname: Rehbock
authors.forename: Jonas
authors.initials: J
authors.lastname: Ekblom
authors.forename: Mikhail F
authors.initials: MF
authors.lastname: Denissenko
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D001761:Bleomycin / Q000494:pharmacology*; D001940:Breast / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D004249:DNA Damage; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005047:Etoposide / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D020022:Genetic Predisposition to Disease; D016678:Genome; D006801:Humans; D009369:Neoplasms / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection
chemical_list: D000964:Antimetabolites, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; C429022:RAD21 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D001761:Bleomycin; D005047:Etoposide