PLK1 and cancer: MK2 could phosphorylate several important cancer-related proteins, such as cell division cycle 25 (Cdc25B/C) [25], polo-like kinase 1 (Plk1) [26], tuberin (TSC2), and the ARE-binding proteins (AU-rich element RNA-binding protein 1 (AUF1), human antigen R (HuR), TTP), which are responsible in modulating transcript stability of many genes, like TNFα, Cyclin D1, Plk3, c-Fos, c-Myc, and matrix metalloproteinase (MMP) affecting cell metabolism, differentiation, and carcinogenesis [27] (Table 1).