Overexpression of PLK-1 has been found in various types of cancers such as squamous cell carcinomas, non-small cell lung cancer, oropharyngeal cancer, and ovarian and endometrial cancers via the inactivation and/or degradation of the tumour suppressor gene p53 in a G2- and S-phase-expressed state. Here, PLK1 is linked to non-small cell lung carcinoma.