MicroRNA (miRNA) is an extremely short chain of RNA, containing approximately twenty-two basepairs and a prominent characteristic of hairpin structure. miRNA also plays an essential role in the process of gene transcription into protein. Meanwhile, it is generally accepted that, during the development of tumor, miRNA functions in a similar way to oncogene or Tumor Suppressor Gene (TSG). Certain viruses able to induce cancer encode miRNA, and accordingly have an impact on host cells and behave as gene regulator. This research mainly aims at identifying miRNAs targeting regions ,in which their gene expression levels is down-regulated according to three selected primary breast tumor microarray experiments. These results propose that these miRNAs can possibly suppress the expression level of these breast cancer related genes. The possibility of these miRNA genes in the role of the tumor suppressor genes is further nvestigated by retrieving their biological functions and disease nformation from the HPRD and OMIM databases.
