RESUMO
MicroRNAs (miRNAs) are short non-coding RNAs that regulate many metabolic and signal transduction pathways. The role of miRNAs, usually found in the cytoplasm, in regulating gene expression and cancer progression has been extensively studied in the last few decades. However, very recently, miRNAs were found to localize in the mitochondria. MiRNAs that specifically localize in the mitochondria and the cytoplasmic miRNAs associated with mitochondria that directly or indirectly modulate specific mitochondrial functions are termed as "mitomiRs". Although it is not clear about the origin of mitomiRs that are situated within mitochondria (nuclear or mitochondrial origin), it is evident that they have specific functions in modulating gene expression and regulating important mitochondrial metabolic pathways. Through this review, we aim to delineate the mechanisms by which mitomiRs alter mitochondrial metabolic pathways and influence the initiation and progression of cancer. We further discuss the functions of particular mitomiRs, which have been widely studied in the context of mitochondrial metabolism and oncogenic signaling pathways. Based on the current knowledge, we can conclude that mitomiRs contribute significantly to mitochondrial function and metabolic regulation, and that dysregulation of mitomiRs can aid the proliferation of cancer cells. Therefore, the less explored area of mitomiRs' biology can be an important topic of research investigation in the future for targeting cancer cells.