PLK3 and lung cancer: Whereas, overexpression of PLK3 has been correlated with a non-favorable outcome in ovarian, breast, and prostate cancer (16–18), contradicting evidence exists in hepatocellular carcinoma, in lung cancer, in head and neck squamous cell and in anal squamous cell carcinoma, where PLK3 is considered to be a tumor suppressor and is correlated with an improved tumor control and survival (19–22).