PLK1 and breast cancer: Interestingly, PLK1 overexpression was enriched in TNBC tumors as compared with luminal BC (43.8% vs 25.4%, p < 0.0001), proposing that PLK1 plays a more important role in Middle Eastern TNBC and functions as an oncogene in TNBC, which is supported in several previous studies (59, 60).