PLK1 and cancer: Among all of the predefined hallmark gene sets, a total of 9 items were most commonly associated with PLK1 overexpression in the TCGA cohort (FDR q-value<0.01), including MTORC1 signaling, E2F targets and the G2M checkpoint, etc. (Figure 16), suggesting that PLK1 may be deeply engaged in GC tumorigenesis and progression through several cancer-associated signaling pathways.