The palmitoyltransferase ZDHHC21 regulates oxidative phosphorylation to induce differentiation block and stemness in AML.

Acute myeloid leukemia (AML) is an aggressive hematological malignancy. Nearly 50% of patients who receive the most intensive treatment inevitably experience disease relapse, likely resulting from the persistence of drug-resistant leukemia stem cells (LSCs). AML cells, especially LSCs, are highly dependent on mitochondrial oxidative phosphorylation (OXPHOS) for survival, but the mechanism involved in OXPHOS hyperactivity is unclear, and a noncytotoxic strategy to inhibit OXPHOS is lacking. To our knowledge, this study is the first to demonstrate that ZDHHC21 palmitoyltransferase serves as a key regulator of OXPHOS hyperactivity in AML cells. The depletion/inhibition of ZDHHC21 effectively induced myeloid differentiation and weakened stemness potential by inhibiting OXPHOS in AML cells. Interestingly, FMS-like tyrosine kinase-3 internal tandem duplication (FLT3-ITD)-mutated AML cells expressed significantly higher levels of ZDHHC21 and exhibited better sensitivity to ZDHHC21 inhibition. Mechanistically, ZDHHC21 specifically catalyzed the palmitoylation of mitochondrial adenylate kinase 2 (AK2) and further activated OXPHOS in leukemic blasts. Inhibition of ZDHHC21 arrested the in vivo growth of AML cells and extended the survival of mice inoculated with AML cell lines and patient derived xenograft AML blasts. Moreover, targeting ZDHHC21 to suppress OXPHOS markedly eradicated AML blasts and enhanced chemotherapy efficacy in relapsed/refractory leukemia. Together, these findings not only uncover a new biological function of palmitoyltransferase ZDHHC21 in regulating AML OXPHOS but also indicate that ZDHHC21 inhibition is a promising therapeutic regimen for patients with AML, especially relapsed/refractory leukemia.

Discovery of a first-in-class CDK2 selective degrader for AML differentiation therapy.

The discovery of effective therapeutic treatments for cancer via cell differentiation instead of antiproliferation remains a great challenge. Cyclin-dependent kinase 2 (CDK2) inactivation, which overcomes the differentiation arrest of acute myeloid leukemia (AML) cells, may be a promising method for AML treatment. However, there is no available selective CDK2 inhibitor. More importantly, the inhibition of only the enzymatic function of CDK2 would be insufficient to promote notable AML differentiation. To further validate the role and druggability of CDK2 involved in AML differentiation, a suitable chemical tool is needed. Therefore, we developed first-in-class CDK2-targeted proteolysis-targeting chimeras (PROTACs), which promoted rapid and potent CDK2 degradation in different cell lines without comparable degradation of other targets, and induced remarkable differentiation of AML cell lines and primary patient cells. These data clearly demonstrated the practicality and importance of PROTACs as alternative tools for verifying CDK2 protein functions.

CDK2 suppression synergizes with all-trans-retinoic acid to overcome the myeloid differentiation blockade of AML cells.

A characteristic feature of leukemia cells is a blockade of differentiation in cellular maturation. All-trans-retinoic acid (ATRA) has been successfully applied for the treatment of M3-type AML (APL, 10 %), but it fails to demonstrate a significant efficacy on the remaining patients with non-APL AML (90 %). Therefore, the research for strategies to extend the efficacy of ATRA-based therapy to non-APL AML is a key avenue of investigation. Here, we evaluate the synergetic effect of CDK2 inhibition and ATRA in AML both in vitro and in vivo. We have determined that both the CDK2 depletion and pharmacological inhibitor of CDK2 significantly sensitize three subtypes of AML cells (including two non-APL cells) to ATRA-induced cell differentiation. RNA-sequence results indicate that transcription activation of differentiation and maturation pathways plays an important role in this synergetic effect. Furthermore, the down-regulation of CDK2 sensitized AML cells to ATRA-induced engraftment prevention of leukemia cells in NOD-SCID mice and promotes the primary AML blasts differentiation when combined with ATRA. Thus, our work not only provides relevant experimental evidence for further validating CDK2 as a target for differentiation therapy, but also uncovers the future clinical application of CDK2 inhibitors in ATRA-based differentiation therapeutics for AML.

Carrier-Free, Pure Nanodrug Formed by the Self-Assembly of an Anticancer Drug for Cancer Immune Therapy.

Ursolic acid (UA) is a food-plant-derived natural product which has good anticancer activities and low toxicity. However, the poor water solubility of UA limits its application in clinic. To address this issue, we developed a carrier-free nanodrug by self-assembly of UA. Here, we showed that UA nanoparticles (NPs) have a near-spherical shape with a diameter of ∼150 nm. UA NPs exhibited higher antiproliferative activity; significantly caused apoptosis; decreased the expression of COX-2/VEGFR2/VEGFA; and increased the immunostimulatory activity of TNF-α, IL-6, and IFN-ß and decreased the activity of STAT-3 in A549 cells in vitro. Furthermore, UA NPs could inhibit tumor growth and have the ability of liver protection in vivo. More importantly, UA NPs could significantly improve the activation of CD4+ T-cells, which indicated that UA NPs have the potential for immunotherapy. Overall, a carrier-free UA nanodrug may be a promising drug to further enhance their anticancer efficacy and immune function.

AKT inhibitor Hu7691 induces differentiation of neuroblastoma cells.

While neuroblastoma accounts for 15% of childhood tumor-related deaths, treatments against neuroblastoma remain scarce and mainly consist of cytotoxic chemotherapeutic drugs. Currently, maintenance therapy of differentiation induction is the standard of care for neuroblastoma patients in clinical, especially high-risk patients. However, differentiation therapy is not used as a first-line treatment for neuroblastoma due to low efficacy, unclear mechanism, and few drug options. Through compound library screening, we accidently found the potential differentiation-inducing effect of AKT inhibitor Hu7691. The protein kinase B (AKT) pathway is an important signaling pathway for regulating tumorigenesis and neural differentiation, yet the relation between the AKT pathway and neuroblastoma differentiation remains unclear. Here, we reveal the anti-proliferation and neurogenesis effect of Hu7691 on multiple neuroblastoma cell lines. Further evidence including neurites outgrowth, cell cycle arrest, and differentiation mRNA marker clarified the differentiation-inducing effect of Hu7691. Meanwhile, with the introduction of other AKT inhibitors, it is now clear that multiple AKT inhibitors can induce neuroblastoma differentiation. Furthermore, silencing AKT was found to have the effect of inducing neuroblastoma differentiation. Finally, confirmation of the therapeutic effects of Hu7691 is dependent on inducing differentiation in vivo, suggesting that Hu7691 is a potential molecule against neuroblastoma. Through this study, we not only define the key role of AKT in the progression of neuroblastoma differentiation but also provide potential drugs and key targets for the application of differentiation therapies for neuroblastoma clinically.

Deneddylation of PML/RARα reconstructs functional PML nuclear bodies via orchestrating phase separation to eradicate APL.

Acute promyelocytic leukemia (APL) is driven by the oncoprotein PML/RARα, which destroys the architecture of PML nuclear bodies (NBs). PML NBs are critical to tumor suppression, and their disruption mediated by PML/RARα accelerates APL pathogenesis. However, the mechanisms of PML NB disruption remain elusive. Here, we reveal that the failure of NB assembly in APL results from neddylation-induced aberrant phase separation of PML/RARα. Mechanistically, PML/RARα is neddylated in the RARα moiety, and this neddylation enhances its DNA-binding ability and further impedes the phase separation of the PML moiety, consequently disrupting PML NB construction. Accordingly, deneddylation of PML/RARα restores its phase separation process to reconstruct functional NBs and activates RARα signaling, thereby suppressing PML/RARα-driven leukemogenesis. Pharmacological inhibition of neddylation by MLN4924 eradicates APL cells both in vitro and in vivo. Our work elucidates the neddylation-destroyed phase separation mechanism for PML/RARα-driven NB disruption and highlights targeting neddylation for APL eradication.

The role of autophagy in targeted therapy for acute myeloid leukemia.

Although molecular targeted therapies have recently displayed therapeutic effects in acute myeloid leukemia (AML), limited response and acquired resistance remain common problems. Numerous studies have associated autophagy, an essential degradation process involved in the cellular response to stress, with the development and therapeutic response of cancers including AML. Thus, we review studies on the role of autophagy in AML development and summarize the linkage between autophagy and several recurrent genetic abnormalities in AML, highlighting the potential of capitalizing on autophagy modulation in targeted therapy for AML.Abbreviations: AML: acute myeloid leukemia; AMPK: AMP-activated protein kinase; APL: acute promyelocytic leukemia; ATG: autophagy related; ATM: ATM serine/threonine kinase; ATO: arsenic trioxide; ATRA: all trans retinoic acid; BCL2: BCL2 apoptosis regulator; BECN1: beclin 1; BET proteins, bromodomain and extra-terminal domain family; CMA: chaperone-mediated autophagy; CQ: chloroquine; DNMT, DNA methyltransferase; DOT1L: DOT1 like histone lysine methyltransferase; FLT3: fms related receptor tyrosine kinase 3; FIS1: fission, mitochondrial 1; HCQ: hydroxychloroquine; HSC: hematopoietic stem cell; IDH: isocitrate dehydrogenase; ITD: internal tandem duplication; KMT2A/MLL: lysine methyltransferase 2A; LSC: leukemia stem cell; MDS: myelodysplastic syndromes; MTORC1: mechanistic target of rapamycin kinase complex 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; NPM1: nucleophosmin 1; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PML: PML nuclear body scaffold; ROS: reactive oxygen species; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SAHA: vorinostat; SQSTM1: sequestosome 1; TET2: tet methylcytosine dioxygenase 2; TKD: tyrosine kinase domain; TKI: tyrosine kinase inhibitor; TP53/p53: tumor protein p53; ULK1: unc-51 like autophagy activating kinase 1; VPA: valproic acid; WDFY3/ALFY: WD repeat and FYVE domain containing 3.

Protein phase separation: A novel therapy for cancer?

In recent years, phase separation has been increasingly reported to play a pivotal role in a wide range of biological processes. Due to the close relationships between cancer and disorders in intracellular physiological function, the identification of new mechanisms involved in intracellular regulation has been regarded as a new direction for cancer therapy. Introducing the concept of phase separation into complex descriptions of disease mechanisms may provide many different insights. Here, we review the recent findings on the phase separation of cancer-related proteins, describing the possible relationships between phase separation and key proteins associated with cancer and indicate possible regulatory modalities, especially drug candidates for phase separation, which may provide more effective strategies for cancer therapy.

Post-translational modification of retinoic acid receptor alpha and its roles in tumor cell differentiation.

Retinoic acid (RA) is a well-known differentiation inducer that exerts its effects by binding to nuclear RA receptors. Retinoic acid receptor α (RARα), as an important nuclear RA receptor, is activated upon RA binding and facilitates the transcription of target genes related to differentiation, which ultimately initiates cell differentiation. Previous studies have found that the transcriptional activity of RARα is regulated by various post-translational modifications, which influence its DNA binding efficiency, transactivation ability and even lead to degradation. Post-translational modifications of RARα, as a consequence, play an important role in the RA-induced differentiation process. Therefore, in this review, we focus on recent advances in the understanding of how these modifications affect the activity of RARα as well as strategies to increase the differentiation effect of RA treatment in cancer cells based on RARα modifications, which may promote the development of novel effective differentiation therapies for cancer treatment.

Co-delivery of sorafenib and siVEGF based on mesoporous silica nanoparticles for ASGPR mediated targeted HCC therapy.

Combination with chemotherapeutic drug and gene therapy has been proven highly effective in suppressing tumor progression. Hence, an asialoglycoprotein receptor (ASGPR)-targeting nanodrug delivery system based on mesoporous silica (MSN) nanocarrier for co-delivery of sorafenib (SO) and vascular endothelial growth factor (VEGF) targeted siRNA (siVEGF) to hepatocellular carcinoma (HCC) was successfully designed and synthesized. The structure of nanoparticles was characterized by IR, particle size, zeta potential and N2 adsorption-desorption. The nanoparticles were further evaluated for drug release, cellular uptake, transfection, cell cytotoxicity and cell cycle against HepG2 and Huh7 cells. In vitro testing demonstrated that MSN-LA delivery system could not only induce S cell cycle arrest, enhance the cytotoxicity and improve the tumor target of SO and siVEGF, but also enhance the siVEGF transfection efficiency in ASGPR-overexpressing Huh7 cells. Overall, the MSN-LA delivery system can be a promising drug carrier which could further enhance the anti-cancer efficacy of SO and siVEGF via the active targeting property of LA.

Dual-Targeting Multifuntional Mesoporous Silica Nanocarrier for Codelivery of siRNA and Ursolic Acid to Folate Receptor Overexpressing Cancer Cells.

A targeting drug delivery system (TDDS) can selectively deliver antitumor drugs to cancerous parts to improve its anticancer efficacy. Hence, a targeted drug delivery system (UA/siVEGF@MSN-FA) coloading ursolic acid (UA) and vascular endothelial growth factor (VEGF) targeted siRNA (siVEGF) based on mesoporous silica (MSN) nanocarrier modified by a folic acid (FA) molecule was designed and synthesized. The MSN-FA nanoparticles were investigated for shape, diameter, and zeta potential and and by infrared (IR) spectroscopy. FR-overexpressing HeLa cells and FR-negative HepG2 cell lines were used to evaluate the in vitro cellular uptake and the cytotoxicity of MSN-FA nanoparticles. The morphology of HeLa cells transfected with siVEGF@MSN-FA was observed using fluorescence microscopy. Our findings demonstrated that UA@MSN-FA nanoparticles were near-spherical, and the particle size was about 209 ± 9.21 nm. The MSN-FA nanocarrier not only could enhance the in vitro transfection efficiency and the stability of siVEGF but also could further improve the targeted anticancer efficacy of UA and siVEGF via the active targeting property of FA. Overall, the MSN-FA drug delivery system could serve as an excellent material in biomedical applications.

Synergistic Chemopreventive and Therapeutic Effects of Co-drug UA-Met: Implication in Tumor Metastasis.

The anticancer properties of ursolic acid (UA) and metformin (Met) have been well demonstrated. However, whether these compounds can act synergistically to prevent and treat cancer is not known. We present in this study, the synergism between UA and Met, and that of a new codrug made of UA and Met (UA-Met) against several cancer cell lines. The combination of high concentration of UA (25, 50, 75, 100 µM) and Met (5, 10, 20, 40 mM) resulted in synergetic cytotoxicity on MDA-MB-231 and MCF-7 cells (CI < 0.8). Molecular and cellular studies showed that codrug UA-Met significantly inhibited the invasion (∼55.3 ± 2.74%) and migration (∼52.4 ± 1.57%) of TGF-ß induced breast cancer MDA-MB-231 and MCF-7 cells in vitro at low concentration of 10 µM. These effects were accompanied by down-regulation of CXCR4, uPA, vimentin, E-cadherin, N-cadherin, and MMP-2/9 proteins expression and regulation of the AMPK/m-TOR signaling pathways as expected from UA and Met. Moreover, UA-Met could reduce the progression of pulmonary metastasis by 4T1 cells (63.4 ± 3.52%) without influencing the glucose blood level in mice. Our study suggests that the codrug UA-Met is safe and effective in preventing cancer metastasis and possibly treatment of cancer.

Metapristone (RU486 metabolite) suppresses NSCLC by targeting EGFR-mediated PI3K/AKT pathway.

Therapies targeting epidermal growth factor receptor (EGFR) can effectively treat with non-small cell lung cancer (NSCLC), but NSCLC's drug resistance makes it intractable. Herein, we showed that RU486 metabolite metapristone inhibited the proliferation of various NSCLC cell lines with either wild (A549, H1299, H520) or mutated EGFR (H1975, HCC827). The suppression was resulted from inhibition by metapristone of EGFR signaling pathways through down-regulating the EGFR, PTEN, as well as AKT and ERK proteins. In addition, metapristone inhibited anti-apoptotic marker Bcl-2, and activated pro-apoptotic key signaling proteins caspase-3, and poly (ADP-ribose) polymerase. Metapristone induced A549 and H1975 cell cycle via arrest at the G0-G1 stage. What's more, metapristone inhibited the growth of NSCLC xenografts in BALB/c nude mice through decreasing the expression of tumor growth biomarkers PCNA and EGFR. Taken together, the present study demonstrated that metapristone suppressed NSCLC proliferation by promoting apoptosis via decrease the cellular EGFR-mediated PI3K/AKT pathways. The results suggest metapristone a new treatment for EGFR-overexpressed NSCLC.