microRNAs and RNA-binding proteins: a complex network of interactions and reciprocal regulations in cancer

In the last decade, an ever-growing number of connections between microRNAs (miRNAs) and RNA-binding proteins (RBPs) have uncovered a new level of complexity of gene expression regulation in cancer. In this review, we examine several aspects of the functional interactions between miRNAs and RBPs in cancer models. We will provide examples of reciprocal regulation: miRNAs regulating the expression of RBPs, or the converse, where an RNA-binding protein specifically regulates the expression of a specific miRNA, or when an RBP can exert a widespread effect on miRNAs via the modulation of a key protein for miRNA production or function. Moreover, we will focus on the ever-growing number of functional interactions that have been discovered in the last few years: RBPs that were shown to cooperate with microRNAs in the downregulation of shared target mRNAs or, on the contrary, that inhibit microRNA action, thus resulting in a protection of the specific target mRNAs. We surely need to obtain a deeper comprehension of such intricate networks to have a chance of understanding and, thus, fighting cancer.