New Insights on the Roles of miR-21 in Cancer Development and Proliferation

MicroRNAs (miRNAs) are small noncoding RNAs strongly implicated in the control of gene expression post-transcriptionally. They account for a wide range of functions recognized as characteristic cancer signatures, including apoptosis, invasion, metastasis, and proliferation. MicroRNA-21 (miR-21) is well-recognized for its crucial role in various solid tumors, such as glioblastoma, ovarian cancer, non-small cell lung cancer, and many others. In numerous malignancies, miR-21 selectively targets multiple key components and influences a broad spectrum of cellular processes, including cancer stemness and cell death. The miR-21 gene exhibits both cancer-promoting and cancer-suppressing properties, though most research highlights its facilitative role in cancer development. MiR-21 mediates PTEN reduction to enhance PI3K/Akt signaling in cancer progression. Its overexpression inhibits apoptosis and significantly promotes pro-survival autophagy. The notable upregulation of miR-21 in cancerous tissues positions it as a promising cancer biomarker with considerable diagnostic and prognostic potential. This study aims to define the functional roles of miR-21 as a crucial regulator in various cancers and its potential as a therapeutic target.