PLK1 and prostate cancer: Moreover, CCND1/CDK4/PLK1/CD44 oncogenic signaling-correlated gene clusters affected 10 pathways, which were significantly associated with serveral functions, as shown in the KEGG pathways (Figure 5D. Pathways in cancer, the PI3K-AKT signaling pathway, and prostate cancer were the most significant pathways associated with CCND1/CDK4/PLK1/CD44 siganling.