title: let-7 microRNA functions as a potential growth suppressor in human colon cancer cells.
abstract: MicroRNAs (miRNAs) are endogenously expressed RNAs, 18-25 nucleotides in length, that repress protein translation through binding to target mRNAs. miRNAs have been implicated in many cellular processes including cell proliferation, differentiation, and death. Recently, let-7 miRNAs were found to regulate human RAS oncogene expression and to be often down-regulated in human lung tumors. In this study, we examined the expression of let-7 miRNAs in human colon cancer tumors and cell lines, with the result that 2 of 6 cases and 1 of 3 cell lines showed reduced expression of let-7. When let-7 low-expressing DLD-1 human colon cancer cells were transfected with let-7a-1 precursor miRNA, which is located at chromosome 9q22.3, the cells underwent significant growth suppression. At that time, the levels of RAS and c-myc proteins were lowered after the transfection, whereas the levels of both of their mRNAs remained almost unchanged. These findings suggest the involvement of let-7 miRNA in the growth of colon cancer cells. Thus, miRNAs might provide a basis for novel RNA anti-cancer agents.
authors.affiliation: Department of Genetic Diagnosis, Gifu International Institute of Biotechnology, Kakamigahara, Japan. yakao@giib.or.jp
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Akao
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Nakagawa
authors.forename: Tomoki
authors.initials: T
authors.lastname: Naoe
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000096:biosynthesis* / Q000235:genetics; D008875:Middle Aged; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D035683:MicroRNAs; D012334:RNA, Neoplasm; C487931:mirnlet7 microRNA, human