title: Identification of miR-30e* regulation of Bmi1 expression mediated by tumor-associated macrophages in gastrointestinal cancer.
abstract: Bmi1 is overexpressed in a variety of human cancers including gastrointestinal cancer. The high expression level of Bmi1 protein is associated with poor prognosis of gastrointestinal cancer patients. On the other hand, tumor-associated macrophages (TAMs) contribute to tumor growth, invasion, and metastasis by producing various mediators in the tumor microenvironment. The aim of this study was to investigate TAM-mediated regulation of Bmi1 expression in gastrointestinal cancer. The relationship between TAMs and Bmi1 expression was analyzed by immunohistochemistry and quantitative real-time PCR (qRT-PCR), and results showed a positive correlation with tumor-infiltrating macrophages (CD68 and CD163) and Bmi1 expression in cancer cells. Co-culture with TAMs triggered Bmi1 expression in cancer cell lines and enhanced sphere formation ability. miRNA microarray analysis of a gastric cancer cell line co-cultured with macrophages was conducted, and using in silico methods to analyze the results, we identified miR-30e* as a potential regulator of Bmi1 expression. Luciferase assays using miR-30e* mimic revealed that Bmi1 was a direct target for miR-30e* by interactions with the putative miR-30e* binding sites in the Bmi1 3' untranslated region. qRT-PCR analysis of resected cancer specimens showed that miR-30e* expression was downregulated in tumor regions compared with non-tumor regions, and Bmi1 expression was inversely correlated with miR-30e* expression in gastric cancer tissues, but not in colon cancer tissues. Our findings suggest that TAMs may cause increased Bmi1 expression through miR-30e* suppression, leading to tumor progression. The suppression of Bmi1 expression mediated by TAMs may thus represent a possible strategy as the treatment of gastrointestinal cancer.
authors: Department of Gastroenterological Surgery, Graduate School of Medical Science, Kumamoto University, Kumamoto, Japan.
authors: Hidetaka
authors: H
authors: Sugihara
authors: Takatsugu
authors: T
authors: Ishimoto
authors: Masayuki
authors: M
authors: Watanabe
authors: Hiroshi
authors: H
authors: Sawayama
authors: Masaaki
authors: M
authors: Iwatsuki
authors: Yoshifumi
authors: Y
authors: Baba
authors: Yoshihiro
authors: Y
authors: Komohara
authors: Motohiro
authors: M
authors: Takeya
authors: Hideo
authors: H
authors: Baba
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D005770:Gastrointestinal Neoplasms / Q000235:genetics* / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D008264:Macrophages / Q000378:metabolism*; D035683:MicroRNAs / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D063150:Polycomb Repressive Complex 1 / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C069077:BMI1 protein, human; C546086:MIRN30b microRNA, human; D035683:MicroRNAs; D063150:Polycomb Repressive Complex 1