MicroRNAs (miRNAs) are noncoding small nucleic acids that contain ~22 nucleotides and are considered to promote the degradation or inhibit the translation of mRNA by targeting its 3\'‑untranslated region. However, growing evidence has revealed that nuclear miRNAs, combined with gene promoters or enhancers, are able to directly mediate gene transcription. These miRNAs exert a critical influence on cancer progression by affecting cell growth, migration and invasion. In this review, the direct regulation of gene expression by nuclear miRNAs at the transcriptional level was discussed and summarized, and their mechanisms of action in cancers were highlighted with reference to the various body systems.