title: microRNA-504 inhibits cancer cell proliferation via targeting CDK6 in hypopharyngeal squamous cell carcinoma.
abstract: Our recent study of the microRNA (miRNA) expression signature of hypopharyngeal squamous cell carcinoma (HSCC) revealed that microRNA-504 (miR-504) is significantly downregulated in HSCC tissues, suggesting that this miRNA is a candidate tumor suppressor. However, several previous reports indicated that miR-504 has an oncogenic function through targeting TP53. The aim of this study was to investigate the functional significance of miR-504 in cancer cells and to identify novel targets regulated by this miRNA in HSCC cells. First, we confirmed the downregulation of miR-504 in HSCC clinical specimens (P<0.0001) by qPCR. Using two sources of miR-504 to restore function, we observed significant inhibition of cancer cell proliferation in head and neck SCC (HNSCC) cell lines (FaDu, SAS and HSC3) and HCT116 colon carcinoma cells (p53+/+ and p53-/-). In HNSCC cells, induction of cell cycle arrest was observed by miR-504 transfection. To identify the molecular targets of miR-504, we performed gene expression analysis of miR-504 transfectants and in silico database analyses. Our data showed that cell cycle-related genes (RB1, CDK6, CDC23 and CCND1) were candidate target genes of miR-504. In HSCC clinical specimens, the expression of cyclin-dependent kinase 6 (CDK6) was significantly higher in cancer tissues compared to non-cancer tissues (P=0.0004). A significant inverse correlation between CDK6 and miR-504 expression was found (r=-0.43, P=0.0039). Expression of miR-504 inhibited CDK6 expression in HNSCC cells. Loss of tumor-suppressive miR-504 enhanced HSCC cell proliferation through targeting CDK6. The identification of novel tumor-suppressive miR-504-mediated molecular pathways and targets provide new insights into HSCC oncogenesis.
authors.affiliation: Department of Functional Genomics, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Kikkawa
authors.affiliation: Department of Functional Genomics, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kinoshita
authors.affiliation: Department of Functional Genomics, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Nijiro
authors.initials: N
authors.lastname: Nohata
authors.affiliation: Department of Otorhinolaryngology/Head and Neck Surgery, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Toyoyuki
authors.initials: T
authors.lastname: Hanazawa
authors.affiliation: Department of Functional Genomics, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Yamamoto
authors.affiliation: Department of Functional Genomics, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Fukumoto
authors.affiliation: Department of Urology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Chiyomaru
authors.affiliation: Department of Urology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Enokida
authors.affiliation: Department of Urology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nakagawa
authors.affiliation: Department of Otorhinolaryngology/Head and Neck Surgery, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Okamoto
authors.affiliation: Department of Functional Genomics, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Naohiko
authors.initials: N
authors.lastname: Seki
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D051361:Cyclin-Dependent Kinase 6 / Q000235:genetics* / Q000378:metabolism*; D030541:Databases, Genetic; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006258:Head and Neck Neoplasms / Q000235:genetics / Q000473:pathology*; D006801:Humans; D007012:Hypopharyngeal Neoplasms / Q000235:genetics / Q000473:pathology*; D008297:Male; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D000077195:Squamous Cell Carcinoma of Head and Neck; D014162:Transfection
chemical_list: C550379:MIRN504 microRNA, human; D035683:MicroRNAs; C495911:CDK6 protein, human; D051361:Cyclin-Dependent Kinase 6