The nucleus is a satisfactory place for complete gene silencing, because the cellular genetic information and transcription machinery reside there.15 Once the siRNAs loaded by the nanocarrier are introduced into the nucleus, the siRNAs are capable of targeting the promoter of Thymidine Kinase 1 (TK1), which is closely associated with cell division and is considered to be an important marker for tumor growth.28,29 RNA-directed DNA methylation can be initiated, which could induce long-term transcriptional silencing of homologous promoters.5 The details of this approach are shown in Scheme 1. Here, TK1 is linked to neoplasm.