MCM4 and infection: Given the down-regulation of hub gene CDK1, CCNB2, and MCM4 in the NN1172-infected thymus, along with the down-regulation of pathways related to mismatch repair, DNA replication, base excision repair, and nucleotide excision repair, we speculate that NN1172 infection may induce incomplete genome replication and insufficient cyclin B1-CDK1 complex activity, leading to G2 arrest and prevents entry into mitosis.