Therefore, we first determined whether UBE2C knockdown would affect the levels of these substrates, including PLK1, cyclin B1, and securin, and found a minor, if any, effect in 4 lung cancer cell lines harboring mutant Kras (Supplemental Figure 3A), suggesting that these substrates are not actively involved in growth suppression induced by UBE2C knockdown. This evidence concerns the gene PTTG1 and lung cancer.