To unveil the underlying mechanism for ALS-induced cell cycle arrest, we further dissected the expression of key cell cycle regulating proteins, including CDK1/CDC2, p-CDC2 (Tyr15), cyclin B1, p-cyclin B1 (Ser133), p-CDC25C (Ser216), PLK1, p53, and p21/Waf1 in HT29 and Caco-2 cells using Western blotting assay. This evidence concerns the gene PLK1 and amyotrophic lateral sclerosis.