MiRNAs are 21-25 nucleotide RNAs that negatively regulate gene expression through translational repression or cleavage of a target mRNA. They are transcribed as precursors that are processed by the nucleases Drosha and Dicer.

Small molecules targeting the secondary structure of precursor miRNAs can be more selective modulators of function than oligonucleotides that target RNA sequence.

MicroRNAs (miRNAs) and promoter hypermethylation are vital epigenetic mechanisms for transcriptional inactivation of tumor suppressor.