MicroRNAs are small non-coding RNAs that regulate gene expression at the 
transcriptional or posttranscriptional level. They are involved in cellular 
development, differentiation, proliferation and apoptosis and play a significant 
role in cancer. Examination of tumor-specific microRNA expression profiles has 
revealed widespread deregulation of these molecules in diverse cancers. Several 
studies have shown that microRNAs function either as tumor suppressor genes or 
oncogenes, whose loss or overexpression respectively has diagnostic and 
prognostic significance. It seems that microRNAs act as major regulators of gene 
expression. In this review, we discuss microRNAs' role in cancer and how 
microRNAs exert their functions through regulation of their gene targets. 
Bioinformatic analysis of putative miRNA binding sites has indicated several 
novel potential gene targets involved in apoptosis, angiogenesis and metastatic 
mechanisms. Matching computational prediction analysis together with microarray 
data seems the best method for microRNA gene target identification. MicroRNAs 
together with transcription factors generate a complex combinatorial code 
regulating gene expression. Thus, manipulation of microRNA-transcription factor 
gene networks may be provides a novel approach for developing cancer therapies.