Phase Separation of Disease-Associated SHP2 Mutants Underlies MAPK Hyperactivation.

The non-receptor protein tyrosine phosphatase (PTP) SHP2, encoded by PTPN11, plays an essential role in RAS-mitogen-activated protein kinase (MAPK) signaling during normal development. It has been perplexing as to why both enzymatically activating and inactivating mutations in PTPN11 result in human developmental disorders with overlapping clinical manifestations. Here, we uncover a common liquid-liquid phase separation (LLPS) behavior shared by these disease-associated SHP2 mutants. SHP2 LLPS is mediated by the conserved well-folded PTP domain through multivalent electrostatic interactions and regulated by an intrinsic autoinhibitory mechanism through conformational changes. SHP2 allosteric inhibitors can attenuate LLPS of SHP2 mutants, which boosts SHP2 PTP activity. Moreover, disease-associated SHP2 mutants can recruit and activate wild-type (WT) SHP2 in LLPS to promote MAPK activation. These results not only suggest that LLPS serves as a gain-of-function mechanism involved in the pathogenesis of SHP2-associated human diseases but also provide evidence that PTP may be regulated by LLPS that can be therapeutically targeted.

Phase separation underlies signaling activation of oncogenic NTRK fusions.

NTRK (neurotrophic tyrosine receptor kinase) gene fusions that encode chimeric proteins exhibiting constitutive activity of tropomyosin receptor kinases (TRK), are oncogenic drivers in multiple cancer types. However, the underlying mechanisms in oncogenesis that involve various N-terminal fusion partners of NTRK fusions remain elusive. Here, we show that NTRK fusion proteins form liquid-like condensates driven by their N-terminal fusion partners. The kinase reactions are accelerated in these condensates where the complexes for downstream signaling activation are also concentrated. Our work demonstrates that the phase separation driven by NTRK fusions is not only critical for TRK activation, but the condensates formed through phase separation serve as organizational hubs for oncogenic signaling.

Targeting androgen receptor phase separation to overcome antiandrogen resistance.

Patients with castration-resistant prostate cancer inevitably acquire resistance to antiandrogen therapies in part because of androgen receptor (AR) mutations or splice variants enabling restored AR signaling. Here we show that ligand-activated AR can form transcriptionally active condensates. Both structured and unstructured regions of AR contribute to the effective phase separation of AR and disordered N-terminal domain plays a predominant role. AR liquid-liquid phase separation behaviors faithfully report transcriptional activity and antiandrogen efficacy. Antiandrogens can promote phase separation and transcriptional activity of AR-resistant mutants in a ligand-independent manner. We conducted a phase-separation-based phenotypic screen and identified ET516 that specifically disrupts AR condensates, effectively suppresses AR transcriptional activity and inhibits the proliferation and tumor growth of prostate cancer cells expressing AR-resistant mutants. Our results demonstrate liquid-liquid phase separation as an emerging mechanism underlying drug resistance and show that targeting phase separation may provide a feasible approach for drug discovery.

A novel partially open state of SHP2 points to a "multiple gear" regulation mechanism.

The protein tyrosine phosphatase SHP2 mediates multiple signal transductions in various cellular pathways, controlled by a variety of upstream inputs. SHP2 dysregulation is causative of different types of cancers and developmental disorders, making it a promising drug target. However, how SHP2 is modulated by its different regulators remains largely unknown. Here, we use single-molecule fluorescence resonance energy transfer and molecular dynamics simulations to investigate this question. We identify a partially open, semiactive conformation of SHP2 that is intermediate between the known open and closed states. We further demonstrate a "multiple gear" regulatory mechanism, in which different activators (e.g., insulin receptor substrate-1 and CagA), oncogenic mutations (e.g., E76A), and allosteric inhibitors (e.g., SHP099) can shift the equilibrium of the three conformational states and regulate SHP2 activity to different levels. Our work reveals the essential role of the intermediate state in fine-tuning the activity of SHP2, which may provide new opportunities for drug development for relevant cancers.

Phase separation ability and phosphatase activity of the SHP1-R360E mutant.

SHP1 is a non-receptor protein tyrosine phosphatase that is widely expressed in hematopoietic cells such as white blood cells, neutrophils, and immune cells. SHP1 can regulate the occurrence and differentiation of immune cells and plays an important role as a tumor suppressor. Previous studies have suggested that SHP2, the homologous protein of phosphatase SHP1, can undergo liquid-liquid phase separation (LLPS). Therefore, in this study, we investigated if SHP1 is also capable of LLPS. To the best of our knowledge, our study is the first to reveal that SHP1 has the ability to undergo LLPS. In addition, we identified an important residue, SHP1-R360E, that can completely inhibit the LLPS ability of SHP1, but this mutation has no remarkable effect on SHP1's enzymatic activity. This allows us to explore the phosphatase activity and phase separation ability of SHP1 separately, providing a basis for future exploration of the phase separation mechanism of phosphatases.

Targeting MLL1 H3K4 methyltransferase activity in mixed-lineage leukemia.

Here we report a comprehensive characterization of our recently developed inhibitor MM-401 that targets the MLL1 H3K4 methyltransferase activity. MM-401 is able to specifically inhibit MLL1 activity by blocking MLL1-WDR5 interaction and thus the complex assembly. This targeting strategy does not affect other mixed-lineage leukemia (MLL) family histone methyltransferases (HMTs), revealing a unique regulatory feature for the MLL1 complex. Using MM-401 and its enantiomer control MM-NC-401, we show that inhibiting MLL1 methyltransferase activity specifically blocks proliferation of MLL cells by inducing cell-cycle arrest, apoptosis, and myeloid differentiation without general toxicity to normal bone marrow cells or non-MLL cells. More importantly, transcriptome analyses show that MM-401 induces changes in gene expression similar to those of MLL1 deletion, supporting a predominant role of MLL1 activity in regulating MLL1-dependent leukemia transcription program. We envision broad applications for MM-401 in basic and translational research.

Inhibition of cIAP1 as a strategy for targeting c-MYC-driven oncogenic activity.

Protooncogene c-MYC, a master transcription factor, is a major driver of human tumorigenesis. Development of pharmacological agents for inhibiting c-MYC as an anticancer therapy has been a longstanding but elusive goal in the cancer field. E3 ubiquitin ligase cIAP1 has been shown to mediate the activation of c-MYC by destabilizing MAD1, a key antagonist of c-MYC. Here we developed a high-throughput assay for cIAP1 ubiquitination and identified D19, a small-molecule inhibitor of E3 ligase activity of cIAP1. We show that D19 binds to the RING domain of cIAP1 and inhibits the E3 ligase activity of cIAP1 by interfering with the dynamics of its interaction with E2. Blocking cIAP1 with D19 antagonizes c-MYC by stabilizing MAD1 protein in cells. Furthermore, we show that D19 and an improved analog (D19-14) promote c-MYC degradation and inhibit the oncogenic function of c-MYC in cells and xenograft animal models. In contrast, we show that activating E3 ubiquitin ligase activity of cIAP1 by Smac mimetics destabilizes MAD1, the antagonist of MYC, and increases the protein levels of c-MYC. Our study provides an interesting example using chemical biological approaches for determining distinct biological consequences from inhibiting vs. activating an E3 ubiquitin ligase and suggests a potential broad therapeutic strategy for targeting c-MYC in cancer treatment by pharmacologically modulating cIAP1 E3 ligase activity.

Radical-induced metal-free alkynylation of aldehydes by direct C-H activation.

A direct C(sp(2) )H alkynylation of aldehyde C(O)H bonds with hypervalent iodine alkynylation reagents provides ynones under metal-free conditions. In this method, 1-[(triisopropylsilyl)ethynyl]-1,2-benziodoxol-3(1H)-one (TIPS-EBX) constitutes an efficient alkynylation reagent for the introduction of the triple bond. The substrate scope is extended to a variety of (hetero)aromatic, aliphatic, and α,ß-unsaturated aldehydes.

Fluorination of 2-substituted benzo[b]furans with Selectfluor™.

An efficient protocol was developed to access 3-fluoro-2-hydroxy-2-substituted benzo[b]furans with Selectfluor™ as the fluorinating reagent in MeCN and water. By utilizing SOCl2/Py as the dehydrating agent, the compounds above were readily converted to 3-fluorinated, 2-substituted benzo[b]furans in high yields.

Discovery and Optimization of WDR5 Inhibitors via Cascade Deoxyribonucleic Acid-Encoded Library Selection Approach.

The DNA-encoded library (DEL) is a powerful hit generation tool for chemical biology and drug discovery; however, the optimization of DEL hits remained a daunting challenge for the medicinal chemistry community. In this study, hit compounds targeting the WIN binding domain of WDR5 were discovered by the initial three-cycle linear DEL selection, and their potency was further enhanced by a cascade DEL selection from the focused DEL designed based on the original first run DEL hits. As expected, these new compounds from the second run of focused DEL were more potent WDR5 inhibitors in the protein binding assay confirmed by the off-DNA synthesis. Interestingly, selected inhibitors exhibited good antiproliferative activity in two human acute leukemia cell lines. Taken together, this new cascade DEL selection strategy may have tremendous potential for finding high-affinity leads against WDR5 and provide opportunities to explore and optimize inhibitors for other targets.

RNA-Guided DNA Transposition in Corynebacterium glutamicum and Bacillus subtilis.

Recently discovered CRISPR-associated transposases (CASTs) have been implemented as useful multiplexed genome editing tools, albeit only in a small group of bacteria. We demonstrated that the type I-F CAST from Vibrio cholerae could induce RNA-guided transposition in Bacillus subtilis and Corynebacterium glutamicum with efficiencies of 0.00018% and 0.027%, respectively. Lowering the culturing temperature to 16 °C in rich media increased the insertion efficiency to 3.64% in B. subtilis. By adding a positive selection against spectinomycin in the cargo DNA, up to 9 kb of the DNA fragment could be integrated at the target site with a 13.4% efficiency in C. glutamicum, which was difficult using the conventional approach. The successful implementation of CAST in these two academically important and industrial-relevant Firmicutes shows its great potential in a wide variety of bacteria and could be further optimized for multiplexed genome editing.

Contribution of Somatic Ras/Raf/Mitogen-Activated Protein Kinase Variants in the Hippocampus in Drug-Resistant Mesial Temporal Lobe Epilepsy.

Importance: Mesial temporal lobe epilepsy (MTLE) is the most common focal epilepsy subtype and is often refractory to antiseizure medications. While most patients with MTLE do not have pathogenic germline genetic variants, the contribution of postzygotic (ie, somatic) variants in the brain is unknown. Objective: To test the association between pathogenic somatic variants in the hippocampus and MTLE. Design, Setting, and Participants: This case-control genetic association study analyzed the DNA derived from hippocampal tissue of neurosurgically treated patients with MTLE and age-matched and sex-matched neurotypical controls. Participants treated at level 4 epilepsy centers were enrolled from 1988 through 2019, and clinical data were collected retrospectively. Whole-exome and gene-panel sequencing (each genomic region sequenced more than 500 times on average) were used to identify candidate pathogenic somatic variants. A subset of novel variants was functionally evaluated using cellular and molecular assays. Patients with nonlesional and lesional (mesial temporal sclerosis, focal cortical dysplasia, and low-grade epilepsy-associated tumors) drug-resistant MTLE who underwent anterior medial temporal lobectomy were eligible. All patients with available frozen tissue and appropriate consents were included. Control brain tissue was obtained from neurotypical donors at brain banks. Data were analyzed from June 2020 to August 2022. Exposures: Drug-resistant MTLE. Main Outcomes and Measures: Presence and abundance of pathogenic somatic variants in the hippocampus vs the unaffected temporal neocortex. Results: Of 105 included patients with MTLE, 53 (50.5%) were female, and the median (IQR) age was 32 (26-44) years; of 30 neurotypical controls, 11 (36.7%) were female, and the median (IQR) age was 37 (18-53) years. Eleven pathogenic somatic variants enriched in the hippocampus relative to the unaffected temporal neocortex (median [IQR] variant allele frequency, 1.92 [1.5-2.7] vs 0.3 [0-0.9]; P = .01) were detected in patients with MTLE but not in controls. Ten of these variants were in PTPN11, SOS1, KRAS, BRAF, and NF1, all predicted to constitutively activate Ras/Raf/mitogen-activated protein kinase (MAPK) signaling. Immunohistochemical studies of variant-positive hippocampal tissue demonstrated increased Erk1/2 phosphorylation, indicative of Ras/Raf/MAPK activation, predominantly in glial cells. Molecular assays showed abnormal liquid-liquid phase separation for the PTPN11 variants as a possible dominant gain-of-function mechanism. Conclusions and Relevance: Hippocampal somatic variants, particularly those activating Ras/Raf/MAPK signaling, may contribute to the pathogenesis of sporadic, drug-resistant MTLE. These findings may provide a novel genetic mechanism and highlight new therapeutic targets for this common indication for epilepsy surgery.

Structure of human SMYD2 protein reveals the basis of p53 tumor suppressor methylation.

SMYD2 belongs to a subfamily of histone lysine methyltransferase and was recently identified to methylate tumor suppressor p53 and Rb. Here we report that SMYD2 prefers to methylate p53 Lys-370 over histone substrates in vitro. Consistently, the level of endogenous p53 Lys-370 monomethylation is significantly elevated when SMYD2 is overexpressed in vivo. We have solved the high resolution crystal structures of the full-length SMYD2 protein in binary complex with its cofactor S-adenosylmethionine and in ternary complex with cofactor product S-adenosylhomocysteine and p53 substrate peptide (residues 368-375), respectively. p53 peptide binds to a deep pocket of the interface between catalytic SET(1-282) and C-terminal domain (CTD) with an unprecedented U-shaped conformation. Subtle conformational change exists around the p53 binding site between the binary and ternary structures, in particular the tetratricopeptide repeat motif of the CTD. In addition, a unique EDEE motif between the loop of anti-parallel ß7 and ß8 sheets of the SET core not only interacts with p53 substrate but also forms a hydrogen bond network with residues from CTD. These observations suggest that the tetratricopeptide repeat and EDEE motif may play an important role in determining p53 substrate binding specificity. This is further verified by the findings that deletion of the CTD domain drastically reduces the methylation activity of SMYD2 to p53 protein. Meanwhile, mutation of EDEE residues impairs both the binding and the enzymatic activity of SMYD2 to p53 Lys-370. These data together reveal the molecular basis of SMYD2 in specifically recognizing and regulating functions of p53 tumor suppressor through Lys-370 monomethylation.

Activation of PI3K/Akt and MAPK pathways regulates Myc-mediated transcription by phosphorylating and promoting the degradation of Mad1.

Mad1, a member of the Myc/Max/Mad family, suppresses Myc-mediated transcriptional activity by competing with Myc for heterodimerization with its obligatory partner, Max. The expression of Mad1 suppresses Myc-mediated cell proliferation and transformation. The levels of Mad1 protein are generally low in many human cancers, and Mad1 protein has a very short half-life. However, the mechanism that regulates the turnover of Mad1 protein is poorly understood. In this study, we showed that Mad1 is a substrate of p90 ribosomal kinase (RSK) and p70 S6 kinase (S6K). Both RSK and S6K phosphorylate serine 145 of Mad1 upon serum or insulin stimulation. Ser-145 phosphorylation of Mad1 accelerates the ubiquitination and degradation of Mad1 through the 26S proteasome pathway, which in turn promotes the transcriptional activity of Myc. Our study provides a direct link between the growth factor signaling pathways regulated by PI3 kinase/Akt and MAP kinases with Myc-mediated transcription.

Screening inhibitors for blocking UHRF1-methylated DNA interaction with capillary electrophoresis.

Epigenetic inheritance in mammals relies in part on propagation of DNA methylation patterns throughout development. UHRF1 (ubiquitin-like containing PHD and RING finger domains 1) is required for maintenance the methylation pattern. It was reported that UHRF1 is overexpressed in a number of cancer types, and its depletion has been established to inhibit growth and invasion of cancer cells. It has been considered as a new therapeutic target for cancer. In the present work, we described a method for screening inhibitors for blocking the formation of UHRF1-methylated DNA (mDNA) complex by using nonequilibrium capillary electrophoresis of the equilibrium mixture (NECEEM). A recombinant UHRF1 with the SRA domain (residues 408-643), a fluorescently labeled double strand mDNA (12 mer) and a known inhibitor mitoxantrone were employed for proof of concept. The method allows to measure the dissociation constant (Kd) of the UHRF1-mDNA complex as well as the rate kinetic constant for complex formation (kon) and dissociation (koff). A small chemical library composed of 60 natural compounds were used to validate the method. Sample pooling strategy was employed to improve the screening throughput. The merit of the method was confirmed by the discovery of two natural products proanthocyanidins and baicalein as the new inhibitors for blocking the formation of UHRF1-mDNA complex. Our work demonstrated that CE represents a straightforward and robust technique for studying UHRF1-mDNA interaction and screening of the inhibitors.

Rational design of a potent macrocyclic peptide inhibitor targeting the PD-1/PD-L1 protein-protein interaction.

We report optimization by rational design of JMPDP-027, a potent cyclic peptide that interferes with the PD-1/PD-L1 protein-protein interaction. JMPDP-027 shows a potent restoring ability towards T-cells with an EC50 of 5.9 nM that is comparable to that of the anti-PD-1 monoclonal antibody pembrolizumab. In addition, JMPDP-027 shows not only high resistance to enzymatic hydrolysis in human serum but also no observable toxicity and potent in vivo anticancer activity comparable to that of the mouse PD-L1 antibody in a colon carcinoma (CT26) model. Cyclic peptide antagonists of this sort may provide novel drug candidates for cancer immunotherapy.

GluN2A-selective positive allosteric modulator-nalmefene-flumazenil reverses ketamine-fentanyl-dexmedetomidine-induced anesthesia and analgesia in rats.

Anesthetics are used to produce hypnosis and analgesic effects during surgery, but anesthesia for a long time after the operation is not conducive to the recovery of animals or patients. Therefore, finding appropriate treatments to counter the effects of anesthetics could enhance postoperative recovery. In the current study, we discovered the novel role of a GluN2A-selective positive allosteric modulator (PAM) in ketamine-induced anesthesia and investigated the effects of the PAM combined with nalmefene and flumazenil (PNF) in reversing the actions of an anesthetic combination (ketamine-fentanyl-dexmedetomidine, KFD). PAM treatment dose-dependently decreased the duration of the ketamine-induced loss of righting reflex (LORR). Compared with those in the KFD group, the duration of LORR and the analgesic effect of the KFD + PNF group were obviously decreased. Meanwhile, successive administration of PNF and KFD had no adverse effects on the cardiovascular and respiratory systems. Both the KFD group and the KFD + PNF group showed no changes in hepatic and renal function or cognitive function in rats. Moreover, the recovery of motor coordination of the KFD + PNF group was faster than that of the KFD group. In summary, our results suggest the potential application of the PNF combination as an antagonistic treatment strategy for anesthesia.

Modeling tumor development and metastasis using paired organoids derived from patients with colorectal cancer liver metastases.

Tumor metastasis accounts for the majority of cancer-related deaths; it is therefore important to develop preclinical models that faithfully recapitulate disease progression. Here, we generated paired organoids derived from primary tumors and matched liver metastases in the same colorectal cancer (CRC) patients. Despite the fact that paired organoids exhibit comparable gene expression and cell morphology, organoids from metastatic lesions demonstrate more aggressive phenotypes, tumorigenesis, and metastatic capacity than those from primary lesions. Transcriptional analyses of the paired organoids reveal signature genes and pathways altered during the progression of CRC, including SOX2. Further study shows that inducible knockdown of SOX2 attenuated invasion, proliferation, and liver metastasis outgrowth. Taken together, we use patient-derived paired primary and metastatic cancer organoids to model CRC metastasis and illustrate that SOX2 is associated with CRC progression and may serve as a potential prognostic biomarker and therapeutic target of CRC.

Discovery of new small molecule inhibitors targeting isocitrate dehydrogenase 1 (IDH1) with blood-brain barrier penetration.

Isocitrate dehydrogenase 1 (IDH1), which catalyzes the conversion of isocitrate to α-ketoglutarate, is one of key enzymes in the tricarboxylic acid cycle (TCA). Hotspot mutation at Arg132 in IDH1 that alters the function of IDH1 by further converting the α-ketoglutarate(α-KG) to 2-hydroxyglutarate (2-HG) have been identified in a variety of cancers. Because the IDH1 mutations occur in a significant portion of gliomas and glioblastomas, it is important that IDH1 inhibitors have to be brain penetrant to treat IDH1-mutant brain tumors. Here we report the efforts to design and synthesize a novel serial of mutant IDH1 inhibitors with improved activity and the blood-brain barrier (BBB) penetration. We show that compound 5 exhibits good brain exposure and potent 2-HG inhibition in a HT1080-derived mouse xenograft model, which makes it a potential preclinical candidate to treat IDH1-mutant brain tumors.

Novel Triapine Derivative Induces Copper-Dependent Cell Death in Hematopoietic Cancers.

Triapine, an iron chelator that inhibits ribonucleotide reductase, has been evaluated in clinical trials for cancer treatment. Triapine in combination with other chemotherapeutic agents shows promising efficacy in certain hematologic malignancies; however, it is less effective against many advanced solid tumors, probably due to the unsatisfactory potency and pharmacokinetic properties. In this report, we developed a triapine derivative IC25 (10) with potent antitumor activity. 10 Preferentially inhibited the proliferation of hematopoietic cancers by inducing mitochondria reactive oxygen species production and mitochondrial dysfunction. Unlike triapine, 10 executed cytotoxic action in a copper-dependent manner. 10-Induced up-expression of thioredoxin-interacting protein resulted in decreased thioredoxin activity to permit c-Jun N-terminal kinase and p38 activation and ultimately led to the execution of the cell death program. Remarkedly, 10 showed good bioavailability and inhibited tumor growth in mouse xenograft models. Taken together, our study identifies compound 10 as a copper-dependent antitumor agent, which may be applied to the treatment of hematopoietic cancers.