Tazawa Hiroshi, Tsuchiya Naoto, Izumiya Masashi, Nakagama Hitoshi
Biochemistry Division, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
Proc Natl Acad Sci U S A. 2007 Sep 25;104(39):15472-7. doi: 10.1073/pnas.0707351104. Epub 2007 Sep 17.
Accumulating evidence suggests a role for microRNAs in human carcinogenesis as novel types of tumor suppressors or oncogenes. However, their precise biological role remains largely elusive. In the present study, we aimed to identify microRNA species involved in the regulation of cell proliferation. Using quantitative RT-PCR analysis, we demonstrated that miR-34a was highly up-regulated in a human colon cancer cell line, HCT 116, treated with a DNA-damaging agent, adriamycin. Transient introduction of miR-34a into two human colon cancer cell lines, HCT 116 and RKO, caused complete suppression of cell proliferation and induced senescence-like phenotypes. Moreover, miR-34a also suppressed in vivo growth of HCT 116 and RKO cells in tumors in mice when complexed and administered with atelocollagen for drug delivery. Gene-expression microarray and immunoblot analyses revealed down-regulation of the E2F pathway by miR-34a introduction. Up-regulation of the p53 pathway was also observed. Furthermore, 9 of 25 human colon cancers (36%) showed decreased expression of miR-34a compared with counterpart normal tissues. Our results provide evidence that miR-34a functions as a potent suppressor of cell proliferation through modulation of the E2F signaling pathway. Abrogation of miR-34a function could contribute to aberrant cell proliferation, leading to colon cancer development.
越来越多的证据表明，微小RNA作为新型的肿瘤抑制因子或癌基因，在人类致癌过程中发挥作用。然而，它们确切的生物学作用在很大程度上仍不清楚。在本研究中，我们旨在鉴定参与细胞增殖调控的微小RNA种类。通过定量逆转录-聚合酶链反应分析，我们证明在用DNA损伤剂阿霉素处理的人结肠癌细胞系HCT 116中，miR-34a高度上调。将miR-34a瞬时导入两个人结肠癌细胞系HCT 116和RKO中，导致细胞增殖完全受到抑制，并诱导出类似衰老的表型。此外，当与去端肽胶原蛋白复合并用于药物递送时，miR-34a也抑制了HCT 116和RKO细胞在小鼠肿瘤中的体内生长。基因表达微阵列和免疫印迹分析显示，导入miR-34a后E2F通路下调。还观察到p53通路上调。此外，25例人类结肠癌中有9例（36%）与相应的正常组织相比，miR-34a表达降低。我们的结果提供了证据，证明miR-34a通过调节E2F信号通路，作为细胞增殖的有效抑制因子发挥作用。miR-34a功能的丧失可能导致异常的细胞增殖，从而导致结肠癌的发生。
