MicroRNAs (
miRNAs) are a class of important non-coding RNAs, which play important roles in
tumorigenesis and development by targeting oncogenes or tumor suppressor genes. One
miRNA can regulate multiple genes, and one gene can be regulated by multiple
miRNAs. To promote the clinical application of
miRNAs, two fundamental questions should be answered: what's the regulatory mechanism of a
miRNA to a gene, and which
miRNAs are important for a specific type of
cancer. In this study, we propose a
miRNA influence capturing (miRNAInf) to decipher regulation relations of
miRNAs on target genes and identify critical
miRNAs in
cancers in a systematic approach. With the pair-wise
miRNA/gene expression profiles data, we consider the assigning problem of a
miRNA on target genes and determine the regulatory mechanisms by computing the Pearson correlation coefficient between the expression changes of a
miRNA and that of its target gene. Furthermore, we compute the relative local influence strength of a
miRNA on its target gene. Finally, integrate the local influence strength and target gene's importance to determine the critical
miRNAs involved in specific
cancer. Results on breast, liver and
prostate cancers show that positive regulations are as common as negative regulations. The top-ranked
miRNAs show great potential as therapeutic targets driving
cancer to a normal state, and they are demonstrated to be closely related to
cancers based on biological functional analysis, drug sensitivity/resistance analysis and survival analysis. This study will be helpful for the discovery of critical
miRNAs and development of
miRNAs-based clinical
therapeutics.