The tumor suppressor p21 inhibits cell proliferation during the stress response. However, p21 can also directly regulate gene expression by repressing specific transcription factors. Here, we identified p21-regulated miRNAs by sequencing small RNAs from HCT116-p21+/+ and HCT116-p21-/- cells. Three abundant clusters, miR-200b-200a-429, miR-200c-141 and miR-183-96-182 were down-regulated in p21-depleted HCT116 and MCF10A cells. Loss of p21 induced epithelial-mesenchymal transition (EMT) and enhanced migration and invasion in multiple model systems. Identification of genome-wide targets of the miR-183-96-182 cluster indicated that miR-183 and miR-96 repressed common targets, including SLUG, ZEB1, ITGB1 and KLF4, to inhibit EMT, migration and invasion. In turn, elevated ZEB1 levels in HCT116-p21-/- cells directly repressed miR-183-96-182 cluster transcription, revealing a feedback loop. Re-introduction of miR-200, miR-183 or miR-96 in HCT116-p21-/- cells inhibited migration and invasion. These novel findings suggest that coordinated down-regulation of three miRNA clusters upon loss of p21 in unstressed cells promotes EMT, migration and invasion.

Citation Format: Xiao L. Li, Toshifumi Hara, Youngeun Choi, Murugan Subramanian, Princy Francis, Sven Bilke, Robert L. Walker, Marbin Pineda, Yu-an Yang, Ji Luo, Lalage M. Wakefield, Ben H. Park, Thomas Brabletz, Dipanjan Chowdhury, Paul S. Meltzer, Ashish Lal. A novel function of p21 in inhibition of epithelial-mesenchymal transition through microRNAs. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5331. doi:10.1158/1538-7445.AM2013-5331