Abstract: m microRNAs (miRNAs) are a class of 18~26nt small non-coding single strand RNA molecules, which negatively regulate the expression of a variety of genes at post-transcriptional level by binding to complementary sites on target mRNA. mutation，deletion or high expression of miRNA was found to correlate with various human cancers. miRNAs involved in tumor cell proliferation, differentiation and apoptosis processes as function as oncogenes or tumor supressors It is predictable that microRNA might be useful in the diagnosis and treatment of malignant tumors.

Key words: microRNA, tumorigenesis, diagnosis, gene therapy