Since the successful exfoliation of graphene from graphite in 2004, graphene and graphene oxide (GO) have been considered the most promising two-dimensional (2D) nanomaterials with distinguished physical and chemical characteristics and have attracted great attention in many different fields. Graphene oxide is well-known for its distinct physiochemical properties and shows only minimal cytotoxicity compared to carbon nanotubes. Until now, only limited efforts have been invested in utilizing GO for gene therapy in pancreatic cancer treatments. In this study, we utilized multi-functionalized monolayer GO as a gene delivery system to efficiently co-deliver HDAC1 and K-Ras siRNAs (small interfering RNAs targeting the HDAC1 gene and the G12C mutant K-Ras gene, respectively) to specifically target pancreatic cancer cells MIA PaCa-2. The systematic mechanistic elucidation of the dual gene silencing effects indicated the inactivation of both the HDAC1 and the K-Ras gene, thereby causing apoptosis, proliferation inhibition and cell cycle arrest in treated MIA PaCa-2 cells. The synergistic combination of gene silencing and NIR light thermotherapy showed significant anticancer efficacy, inhibiting in vivo tumor volume growth by >80%. Furthermore, GO can be metabolized in the mouse model within a reasonable period of time without obvious side effects. Based on preliminary in vivo application, this study for the first time indicates the promising potential of functionalized GO as a vehicle for gene therapy delivery with low toxicity for the treatment of pancreatic adenocarcinoma.

In this work, we report the engineering of polyelectrolyte polymers coated Gold nanorods (AuNRs)-based nanocarriers that are capable of co-delivering small interfering RNA (siRNA) and an anticancer drug doxorubicin (DOX) to Panc-1 cancer cells for combination of both chemo- and siRNA-mediated mutant K-Ras gene silencing therapy. Superior anticancer efficacy was observed through synergistic combination of promoted siRNA and DOX release upon irradiating the nanoplex formulation with 665 nm light. Our antitumor study shows that the synergistic effect of AuNRs nanoplex formulation with 665 nm light treatment is able to inhibit the in vivo tumor volume growth rate by 90%. The antitumor effect is contributed from the inactivation of K-Ras gene and thereby causing a profound synthesis (S) phase arrest in treated Panc-1 cells. Our study shows that the percentage of Panc-1 cells treated by nanoplex formulation with S phase is determined to be 35% and it is 17% much higher than that of Panc-1 cells without any treatments. The developed nanotherapy formulation here, that combines chemotherapy, RNA silencing and NIR window light-mediated therapy, will be seen to be the next natural step to be taken in the clinical research for improving the therapeutic outcomes of the pancreatic adenocarcinoma treatment.

LSD1 is essential for the maintenance of pluripotency of embryonic stem (ES) or embryonic carcinoma/teratocarcinoma (EC) cells. We have previously developed novel LSD1 inhibitors that selectively inhibit ES/EC cells. However, the critical targets of LSD1 remain unclear. Here, we found that LSD1 interacts with histone deacetylase 1 (HDAC1) to regulate the proliferation of ES/EC cells through acetylation of histone H4 at lysine 16 (H4K16), which we show is a critical substrate of HDAC1. The LSD1 demethylase and HDAC1 deacetylase activities were both inactivated if one of them in the complex was chemically inhibited in ES/EC cells or in reconstituted protein complexes. Loss of HDAC1 phenocopied the selective growth-inhibitory effects and increased the levels of H3K4 methylation and H4K16 acetylation of LSD1 inactivation on ES/EC cells. Reduction of acetylated H4K16 by ablation of the acetyltransferase males absent on the first (MOF) is sufficient to rescue the growth inhibition induced by LSD1 inactivation. While LSD1 or HDAC1 inactivation caused the downregulation of Sox2 and Oct4 and induction of differentiation genes, such as FOXA2 or BMP2, depletion of MOF restored the levels of Sox2, Oct4, and FoxA2 in LSD1-deficient cells. Our studies reveal a novel mechanism by which LSD1 acts through the HDAC1- and MOF-mediated regulation of H4K16 acetylation to maintain the pluripotency of ES/EC cells.

Many non-histone proteins are lysine methylated and a novel function of this modification is to trigger the proteolysis of methylated proteins. Here, we report that the methylated lysine 142 of DNMT1, a major DNA methyltransferase that preserves epigenetic inheritance of DNA methylation patterns during DNA replication, is demethylated by LSD1. A novel methyl-binding protein, L3MBTL3, binds the K142-methylated DNMT1 and recruits a novel CRL4^DCAF5 ubiquitin ligase to degrade DNMT1. Both LSD1 and PHF20L1 act primarily in S phase to prevent DNMT1 degradation by L3MBTL3-CRL4^DCAF5. Mouse L3MBTL3/MBT-1 deletion causes accumulation of DNMT1 protein, increased genomic DNA methylation, and late embryonic lethality. DNMT1 contains a consensus methylation motif shared by many non-histone proteins including E2F1, a key transcription factor for S phase. We show that the methylation-dependent E2F1 degradation is also controlled by L3MBTL3-CRL4^DCAF5. Our studies elucidate for the first time a novel mechanism by which the stability of many methylated non-histone proteins are regulated.

SOX2 is a dose-dependent master stem cell protein that controls the self-renewal and pluripotency or multipotency of embryonic stem (ES) cells and many adult stem cells. We have previously found that SOX2 protein is monomethylated at lysine residues 42 (K42) and 117 (K117) by SET7 methyltransferase to promote SOX2 proteolysis, whereas LSD1 and PHF20L1 act on both methylated K42 and K117 to prevent SOX2 proteolysis. However, the mechanism by which the methylated SOX2 protein is degraded remains unclear. Here, we report that L3MBTL3, a protein with the MBT methylation binding domain, is required for SOX2 proteolysis. Our studies showed that L3MBTL3 preferentially binds to the methylated K42 in SOX2, although mutation of K117 also partially reduces the interaction between SOX2 and L3MBTL3. The direct binding of L3MBTL3 to the methylated SOX2 protein leads to the recruitment of the CRL4-DCAF5 ubiquitin E3 ligase to target SOX2 protein for ubiquitin-dependent proteolysis. While loss of either LSD1 or PHF20L1 destabilizes SOX2 protein and impairs the self-renewal and pluripotency of mouse ES cells, knockdown of L3MBTL3 or DCAF5 is sufficient to restore the protein levels of SOX2 and rescue the defects of mouse ES cells caused by LSD1 or PHF20L1 deficiency. We also found that retinoic acid-induced differentiation of mouse ES cells is accompanied with the enhanced degradation of the methylated SOX2 protein at both K42 and K117. Our studies provide novel insights into the mechanism by which the methylation-dependent degradation of SOX2 protein is controlled by the L3MBTL3-CRL4-DCAF5 ubiquitin ligase complex.