size and/or centrosome number, which will also lead to improper segregation of chromosomes, aneuploidy, and tumorigenesis. Oncogenic properties of PLK1 are believed to be due to its role in driving cell cycle progression. Supporting evidence comes from the overexpression studies of PLK1 in NIH3T3 cell line. These cells become capable of forming foci and growing in soft agar and more importantly, these cells can form tumors in nude mice due to PLK1 overexpression. PLK1 has also been linked to known pathways that are altered during the neoplastic transformation. Retinoblastoma tumor suppressor (RB) pathway activation results in the repression of PLK1 promoter in a SWI/SNF chromatin remodeling complex dependent manner. In case of RB inactivation, PLK1 expression seems to be deregulated. This new finding suggests that PLK1 may be a target of the retinoblastoma tumor suppressor (RB) pathway. Moreover, PLK1 seems to be involved in the tumor suppressor p53 related pathways. Evidence suggests that PLK1 can inhibit transactivation and pro-apoptotic functions of p53 function by physical interaction and phosphorylation. Clinical significance PLK1 is being studied as a target for cancer drugs. Many colon and lung cancers are caused by K-RAS mutations. These cancers are dependent on PLK1. When PLK1 expression was silenced with RNA interference in cell culture, K-RAS cells were selectively killed, without harming normal cells. PLK1 inhibitor volasertib is being evaluated in clinical trials for use in acute myeloid leukemia (AML). A combination of PLK1 and EGFR inhibition overcomes T790M-mediated drug resistance in vitro and in vivo in non-small cell lung cancer (NSCLC). In HNSCC mutations of the AJUBA mediate sensitivity to treatment with cell-cycle inhibitors including Plk1 inhibitor volasertib. In mesenchymal NSCLC cells, cMet phosphorylation is regulated by Plk1‐mediated vimentin phosphorylation via β1‐integrin. The combination of cMet and Plk1 inhibition led to significant tumor regression in NSCLC in vivo models treated with clinically relevant drugs. Rigosertib is an experimental RAS/PI3K/PLK1 inhibitor. Interactions PLK1 has been shown to interact with: CHEK2, NUDC, PIN1, PSMA3, PSMA5, PSMA6, PSMA7, PSMB3, and TSC1. Vimentin Structural analysis has been used to explain the broad specificity of PLK1. See also Polo-like kinases, the gene family that PLK1 belongs to References EC 2.7.11