miR-21 downregulates the tumor suppressor P12CDK2AP1 and Stimulates Cell Proliferation and Invasion

The present study was undertaken to investigate the regulation of P12CDK2AP1 by miRNAs. A conserved target site for miR‐21 within the CDK2AP1‐3′‐UTR at nt 349–370 was predicted by bioinformatics software and an inverse correlation of miR‐21 and CDK2AP1 protein was observed. Highly specific amplification and quantification of miR‐21 was achieved using real‐time RT‐PCR. Transfection of HaCaT cells with pre‐miR‐21 significantly suppressed a luciferase reporter including the CDK2AP1‐3′‐UTR, whereas transfection of Tca8113 with anti‐miR‐21 increased activity of this reporter. This was abolished when a construct mutated at the miR‐21/nt 349–370 target site was used instead. Anti‐miR‐21‐transfected Tca8113 cells showed an increase of CDK2AP1 protein and reduced proliferation and invasion. Resected primary tumors and tumor‐free surgical margins of 18 patients with head and neck squamous cell carcinomas demonstrated an inverse correlation between miR‐21 and P12CDK2AP1. This study shows that P12CDK2AP1 is downregulated by miR‐21 and that miR‐21 promotes proliferation and invasion in cultured cells. J. Cell. Biochem. 112: 872–880, 2011. © 2010 Wiley‐Liss, Inc.