During the past ten years, microRNAs (miRNAs) have been shown to play a more 
significant role in the formation and progression of cancer diseases than 
previously thought. With an increase in reports about the dysregulation of 
miRNAs in diverse tumor types, it becomes more obvious that classic 
tumor-suppressive molecules enter deep into the world of miRNAs. Recently, it 
has been demonstrated that a typical tumor suppressor p53, known as the guardian 
of the genome, regulates some kinds of miRNAs to contribute to tumor suppression 
by the induction of cell-cycle arrest and apoptosis. Meanwhile, miRNAs 
directly/indirectly control the expression level and activity of p53 to 
fine-tune its functions or to render p53 inactive, indicating that the interplay 
between p53 and miRNA is overly complicated. The findings, along with current 
studies, will underline the continuing importance of understanding this 
interlocking control system for future therapeutic strategies in cancer 
treatment and prevention.