title: Modulation of gene expression and cell-cycle signaling pathways by the EGFR inhibitor gefitinib (Iressa) in rat urinary bladder cancer.
abstract: The epidermal growth factor receptor inhibitor Iressa has shown strong preventive efficacy in the N-butyl-N-(4-hydroxybutyl)-nitrosamine (OH-BBN) model of bladder cancer in the rat. To explore its antitumor mechanism, we implemented a systems biology approach to characterize gene expression and signaling pathways in rat urinary bladder cancers treated with Iressa. Eleven bladder tumors from control rats, seven tumors from rats treated with Iressa, and seven normal bladder epithelia were profiled by the Affymetrix Rat Exon 1.0 ST Arrays. We identified 713 downregulated and 641 upregulated genes in comparing bladder tumors versus normal bladder epithelia. In addition, 178 genes were downregulated and 96 genes were upregulated when comparing control tumors versus Iressa-treated tumors. Two coexpression modules that were significantly correlated with tumor status and treatment status were identified [r = 0.70, P = 2.80 × 10(-15) (bladder tumor vs. normal bladder epithelium) and r = 0.63, P = 2.00 × 10(-42) (Iressa-treated tumor vs. control tumor), respectively]. Both tumor module and treatment module were enriched for genes involved in cell-cycle processes. Twenty-four and twenty-one highly connected hub genes likely to be key drivers in cell cycle were identified in the tumor module and treatment module, respectively. Analysis of microRNA genes on the array chips showed that tumor module and treatment module were significantly associated with expression levels of let-7c (r = 0.54, P = 3.70 × 10(-8) and r = 0.73, P = 1.50 × 10(-65), respectively). These results suggest that let-7c downregulation and its regulated cell-cycle pathway may play an integral role in governing bladder tumor suppression or collaborative oncogenesis and that Iressa exhibits its preventive efficacy on bladder tumorigenesis by upregulating let-7 and inhibiting the cell cycle. Cell culture study confirmed that the increased expression of let-7c decreases Iressa-treated bladder tumor cell growth. The identified hub genes may also serve as pharmacodynamic or efficacy biomarkers in clinical trials of chemoprevention in human bladder cancer.
authors: Department of Surgery and The Alvin J. Siteman Cancer Center, Washington University School of Medicine, Saint Louis, Missouri, USA. myou@mcw.edu
authors: Yan
authors: Y
authors: Lu
authors: Pengyuan
authors: P
authors: Liu
authors: Francoise
authors: F
authors: Van den Bergh
authors: Victoria
authors: V
authors: Zellmer
authors: Michael
authors: M
authors: James
authors: Weidong
authors: W
authors: Wen
authors: Clinton J
authors: CJ
authors: Grubbs
authors: Ronald A
authors: RA
authors: Lubet
authors: Ming
authors: M
authors: You
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005260:Female; D000077156:Gefitinib; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D035683:MicroRNAs / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D011799:Quinazolines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011916:Rats, Inbred F344; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced / Q000188:drug therapy / Q000235:genetics*
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D035683:MicroRNAs; D011799:Quinazolines; D012333:RNA, Messenger; D066246:ErbB Receptors; D000077156:Gefitinib