Here, six cancer risk pathways (“APC-C-mediated degradation of cell cycle proteins”, “Cyclin B2 mediated events”, “PLK1 signaling events”, “Mitotic Prometaphase”, “Beta defensins” and “Defensins”) in six human cancers were identified based on p values of Wilcoxon signed-rank test and were evaluated through five-fold cross-validation approach. This evidence concerns the gene PLK1 and cancer.