CDKN1A and glioma: P21, as a cyclin-dependent kinase inhibitor encoded by the CDKN1A gene, inhibits the formation of the CDK2-CDK1 complex and mediates the G1 phase arrest of p53- dependent cell cycle. Numerous studies have shown that lncRNAs regulated the cell cycle by affecting the expression of p21 protein, leading to the proliferation of glioma cells.