For shRNA knockdown, MRC-5 cells were transduced with pLKO-based lentivirus expressing shRNA against the targeted gene for 48 hours. The shRNA sequence for Cdh1 knockdown was 59CCAGTCAGAACCGGAAAGCCA39 and the shRNA sequence for APC8 knockdown was 59GCAGGAGGTAA-TATGCTATAA39. All pLKO-based shRNA lentiviral vectors were purchased from the Washington University Children's Discovery Institute/Genome Center.