title: Tumor suppressive microRNA-1 mediated novel apoptosis pathways through direct inhibition of splicing factor serine/arginine-rich 9 (SRSF9/SRp30c) in bladder cancer.
abstract: We have previously found that restoration of tumor suppressive microRNA-1 (miR-1), induced cell apoptosis in bladder cancer (BC) cell lines. However, the apoptosis mechanism induced by miR-1 was not fully elucidated. Alternative splicing of mRNA precursors provides cancer cells with opportunities to translate many oncogenic protein variants, which promote cell proliferation and survival under unpreferable condition for cancer development. Serine/arginine-rich (SR) protein family, which involved in alternative pre-mRNA splicing, plays a critical role for regulating apoptosis by splicing apoptosis-related genes. However, transcriptional regulation of SR proteins, themselves, has not been elucidated. In this study, we focused on splicing factor serine/arginine-rich 9 (SRSF9/SRp30c) on the basis of our previous genome-wide gene expression analysis using miR-1-transfected BC cell lines because putative target sites of miR-1 are existed in 3'-untranslated region (UTR) of SRSF9 mRNA. The expression levels of mRNA of SRSF9 were extremely reduced in the miR-1 transfectants. A luciferase activity significantly decreased in the transfectants suggesting that actual binding occurred between miR-1 and 3'UTR of SRSF9 mRNA. Loss-of-function assays demonstrated that significant inhibitions of cell proliferation, migration, and invasion were observed in the si-SRSF9 transfectants. Apoptosis assays demonstrated that cell apoptosis fraction increased and that caspase-3/7 was activated in the si-SRSF9 transfectants. Our data indicated that tumor suppressive miR-1 induces apoptosis through direct inhibition of SRSF9 in BC. The identification of molecular mechanisms between miRNAs and SR proteins could provide novel apoptosis pathways and their epigenetic regulations and offer new strategies for BC treatment.
authors.affiliation: Department of Urology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yoshino
authors.forename: Hideki
authors.initials: H
authors.lastname: Enokida
authors.forename: Takeshi
authors.initials: T
authors.lastname: Chiyomaru
authors.forename: Shuichi
authors.initials: S
authors.lastname: Tatarano
authors.forename: Hideo
authors.initials: H
authors.lastname: Hidaka
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamasaki
authors.forename: Takenari
authors.initials: T
authors.lastname: Gotannda
authors.forename: Tokushi
authors.initials: T
authors.lastname: Tachiwada
authors.forename: Nijiro
authors.initials: N
authors.lastname: Nohata
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamane
authors.forename: Naohiko
authors.initials: N
authors.lastname: Seki
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nakagawa
mesh_terms: D017209:Apoptosis; D053148:Caspase 3 / Q000096:biosynthesis; D053179:Caspase 7 / Q000096:biosynthesis; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D016147:Genes, Tumor Suppressor; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D000068103:Serine-Arginine Splicing Factors; D001749:Urinary Bladder Neoplasms / Q000378:metabolism* / Q000473:pathology*
chemical_list: C544547:MIRN1 microRNA, human; D035683:MicroRNAs; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors; D053148:Caspase 3; D053179:Caspase 7