MicroRNAs (
miRNAs) function as regulatory molecules of gene expression with multifaceted activities that exhibit direct or indirect oncogenic properties, which promote cell proliferation, differentiation, and the development of different types of
cancers. Because of their extensive functional involvement in many cellular processes, under both normal and pathological conditions such as various
cancers, this class of molecules holds particular interest for
cancer research.
MiRNAs possess the ability to act as
tumor suppressors or oncogenes by regulating the expression of different apoptotic
proteins,
kinases, oncogenes, and other molecular mechanisms that can cause the onset of
tumor development. In contrast to current
cancer medicines,
miRNA-based
therapies function by subtle repression of gene expression on a large number of oncogenic factors, and therefore are anticipated to be highly efficacious. Given their unique mechanism of action,
miRNAs are likely to yield a new class of targeted
therapeutics for a variety of
cancers. More than thousand
miRNAs have been identified to date, and their molecular mechanisms and functions are well studied. Furthermore, they are established as compelling therapeutic targets in a variety of cellular complications. However, the notion of using them as therapeutic tool was proposed only recently, given that modern imaging methods are just beginning to be deployed for
miRNA research. In this review, we present a summary of various molecular imaging methods, which are instrumental in revealing the therapeutic potential of
miRNAs, especially in various
cancers. Imaging methods have recently been developed for monitoring the expression levels of
miRNAs and their target genes by fluorescence-, bioluminescence- and chemiluminescence-based imaging techniques. Mature
miRNAs bind to the
untranslated regions (
UTRs) of the target mRNAs and regulate target genes expressions. This concept has been used for the development of fluorescent reporter-based imaging strategies to monitor the functional status of endogenous
miRNAs, or the respective
miRNAs transiently co-expressed in cells. Bioluminescence-based imaging strategies have been used to investigate various stages of
miRNA processing and its involvement in different cellular processes. Similarly, chemiluminsecence methods were developed for in vitro
miRNA imaging such as monitoring their therapeutic roles in various
cancer cell lines.