title: Decreased levels of miR-224 and the passenger strand of miR-221 increase MBD2, suppressing maspin and promoting colorectal tumor growth and metastasis in mice.
abstract: OBJECTIVE
  Little is known about functions of microRNA (miR) passenger strands (miR*) or their roles in tumor development or progression. We screened for miRs and miR* with levels that were altered in metastatic colorectal cancer (CRC) cells and human tumor samples and investigated their targets and effects on cell function and tumor progression in mice.
  
  
  METHODS
  We performed array-based profile analysis to identify miRs with levels that were increased more than 2-fold in metastatic (SW620) CRC cells compared with nonmetastatic (SW480) cells. Quantitative polymerase chain reaction and in situ hybridization analyses were used to measure miRNA levels in CRC cell lines and human tumor samples. We used miRNA duplex mimics or inhibitors to increase and decrease levels of miRNA in CRC cells and assessed their activities and ability to form metastatic xenograft tumors in nude mice.
  
  
  RESULTS
  Levels of miR-221* and miR-224 were reduced in metastatic compared with nonmetastatic CRC cells; levels in human tumor samples correlated inversely with tumor stage and metastasis to lymph nodes as well as patient survival times. SW480 cells transfected with miR-221* or miR-224 inhibitors had increased motility in vitro compared with SW480 control cells and formed larger, more metastatic tumors when injected into mice. SW620 cells transfected with miR-221* or miR-224 mimics had reduced migration and motility in vitro and formed smaller tumors with fewer metastases in mice compared with control SW620 cells. We identified the 3' untranslated region of MBD2 messenger RNA as a target of miR-221* and miR-224. MBD2 silences the gene encoding maspin, a suppressor of metastasis. In CRC cells, we found that miR-221* and miR-224 increase the expression of maspin through MBD2 down-regulation.
  
  
  CONCLUSIONS
  In metastatic CRC cells, reduced levels of miR-221* and miR-224 increase levels of MBD2, thereby decreasing expression of the metastasis suppressor maspin. Increased activities of miR-221* and miR-224 reduce growth and metastasis of CRC xenograft tumors in mice; these miRs might be developed as therapeutic reagents or biomarkers of CRC progression.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of North Dakota, Grand Forks, North Dakota; The State Key Laboratory for Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Kefei
authors.initials: K
authors.lastname: Yuan
authors.forename: Ke
authors.initials: K
authors.lastname: Xie
authors.forename: John
authors.initials: J
authors.lastname: Fox
authors.forename: Huawei
authors.initials: H
authors.lastname: Zeng
authors.forename: Hongwei
authors.initials: H
authors.lastname: Gao
authors.forename: Canhua
authors.initials: C
authors.lastname: Huang
authors.forename: Min
authors.initials: M
authors.lastname: Wu
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000235:genetics / Q000401:mortality / Q000473:pathology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D056284:Histone Deacetylase 1 / Q000502:physiology; D006801:Humans; D051379:Mice; D035683:MicroRNAs / Q000502:physiology*; D011379:Prognosis; D015843:Serpins / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D056284:Histone Deacetylase 1; D035683:MicroRNAs; D015843:Serpins; C115368:MBD2 protein; C525709:MIR221, human; C546122:MIRN221 microRNA, mouse; C546140:MIRN224 microRNA, human; C584584:MIRN224 microRNA, mouse; C085344:SERPIN-B5; C110550:HDAC1 protein, human
keywords: 5-aza-2′-deoxycytidine; CRC; Colon Cancer Progression; DAC; DFS; LNM; Metastases; Mouse Model; OS; Prognostic Factor; ROC; RT-PCR; TSA; UTR; colorectal cancer; disease-free survival; lymph node metastasis; mRNA; messenger RNA; miRNA; microRNA; overall survival; receiver operating characteristic; reverse-transcription polymerase chain reaction; trichostatin A; untranslated region