MicroRNA-Induced Regulation of the IGF-1 System in Various Types of Cancer.

Insulin-like growth factor 1 (IGF-1) is an important endocrine and autocrine/paracrine factor that regulates various cellular responses in multiple biological systems. Its actions are mediated mainly via its binding to the type 1 IGF receptor (IGF-1R), while its bioactivity is also modulated by the IGF-binding proteins (IGFBPs). The IGF-1 system regulates cell growth, differentiation and energy metabolism and thus plays a crucial role in the modulation of key aspects of cancer biology, such as cancer cell growth, survival, transformation and invasion. The synthesis of IGF-1 is regulated, among other factors, by microRNAs (miRNAs), and it has been shown that the miRNA-induced regulation of IGF-1 is implicated in various stages of tumor development and/or progression in different types of cancer. The aim of this review was to identify and characterize the miRNA-induced regulation of the IGF-1 system in various types of cancer. It was revealed that many miRNAs can be used as potential biomarkers, while others may contribute to metastasis regulation, targeting components of the IGF-1 bioregulation system and being implicated in cancer staging and/or progression. Additional miRNAs and their role in IGF-1's effects on other types of cancer have also been identified. Nevertheless, future studies are needed to expand the current knowledge on the role of miRNAs in the regulation of other components of the IGF-1 bioregulation system and in various types of cancer, contributing further to the characterization of the role of miRNAs and their target genes as pathogenic, therapeutic and diagnostic molecules for cancer in clinical practice.