Novel p97/VCP inhibitor induces endoplasmic reticulum stress and apoptosis in both bortezomib-sensitive and -resistant multiple myeloma cells

Identification of Omaveloxolone as An Endoplasmic Reticulum Associated Degradation Inhibitor That Induces Early Apoptotic Signaling in Multiple Myeloma

Endoplasmic reticulum-associated degradation (ERAD) is essential for maintaining protein homeostasis, yet its regulatory mechanisms remain poorly understood. A major challenge in studying ERAD is the lack of specific inhibitors targeting the ERAD complex. To address this, we conducted a cell-based high-throughput screen using the FDA-repurposing library and identified omaveloxolone (RTA408) as a potent ERAD inhibitor that selectively impairs the degradation of ER luminal and membrane substrates. Beyond its utility in identifying ERAD substrates, RTA408 exhibits strong cytotoxic effects in multiple myeloma (MM), an incurable plasma cell malignancy. RTA408 inhibits ERAD activity and rapidly induces apoptotic signaling via caspase 8 and the death-inducing signaling complex (DISC). Notably, RTA408 is cytotoxic to malignant plasma cells, including those resistant to proteasome inhibitors, and demonstrates in vivo anti-myeloma activity. Our findings establish ERAD inhibitors as valuable tools for dissecting ERAD regulation while also highlighting their potential as therapeutic agents for MM.

Highlights

We developed a cell-based screening approach to identify novel modulators of endoplasmic reticulum associated degradation (ERAD), with implications in studying ERAD biology and targeting plasma cell neoplasms.Screening of the FDA-repurposing library identified Omaveloxolone (RTA408) as an inhibitor of luminal and membrane ERAD substrate degradation, which can be leveraged to identify ERAD substrates.maveloxolone treatment rapidly induces the unfolded protein response and apoptosis that is dependent on caspase 8 and death-inducing signaling complex (DISC) in multiple myeloma cells. maveloxolone exhibits cytotoxic effects against multiple myeloma cells in vitro and in vivo and induces apoptosis in primary plasma cells from patients with relapsed/refractory myeloma.

Targeting p97/Valosin-Containing Protein Promotes Hepatic Stellate Cell Senescence and Mitigates Liver Fibrosis

Liver fibrosis, one of the main histological determinants of various chronic liver diseases, currently lacks effective treatment. Hepatic stellate cells (HSCs) are pivotal in the production of extracellular matrix and amplify the fibrogenic response. Inhibiting the activation of HSCs or promoting the senescence of activated HSCs is crucial for the regression of liver fibrosis. The ATPase p97, also known as valosin-containing protein (VCP), is a central component of the ubiquitin-proteasome system, and it regulates numerous cellular processes by influencing protein homeostasis. In this study, we observed an upregulation of p97 expression around regions exhibiting fibrosis in a diet- and chemical-induced nonalcoholic steatohepatitis and fibrosis murine model. Intervention with the p97 antagonist CB-5083 or the knockdown of p97 reduced the expression of alpha-smooth muscle actin and collagen-I in both mouse or human HSCs. The administration of CB-5083 induced HSC senescence and resulted in the upregulation of senescence markers, including p21, p53, GPX4, and senescence-associated β-galactosidase. Furthermore, CB-5083 treatment also inhibited the expression of Yes-associated protein (YAP), which is also a senescence-related regulatory protein and has a profibrotic function. We used CB-5083 to treat fibrotic mice and found that the activation of HSCs was inhibited, and the liver fibrosis was attenuated. In addition, in vivo experiments confirmed that CB-5083 facilitated HSC senescence and reduced YAP expression. These findings underscore the potential of pharmacological targeting p97/VCP to induce HSC senescence and alleviate liver fibrosis.

Selective delivery of imaging probes and therapeutics to the endoplasmic reticulum or Golgi apparatus: Current strategies and beyond

To maximize therapeutic effects and minimize unwanted effects, the interest in drug targeting to the endoplasmic reticulum (ER) or Golgi apparatus (GA) has been recently growing because two organelles are distributing hubs of cellular building/signaling components (e.g., proteins, lipids, Ca2+) to other organelles and the plasma membrane. Their structural or functional damages induce organelle stress (i.e., ER or GA stress), and their aggravation is strongly related to diseases (e.g., cancers, liver diseases, brain diseases). Many efforts have been developed to image (patho)physiological functions (e.g., oxidative stress, protein/lipid-related processing) and characteristics (e.g., pH, temperature, biothiols, reactive oxygen species) in the target organelles and to deliver drugs for organelle disruption using organelle-targeting moieties. Therefore, this review will overview the structure, (patho)physiological functions/characteristics, and related diseases of the organelles of interest. Future direction on ER or GA targeting will be discussed by understanding current strategies and investigations on targeting, imaging/sensing, and therapeutic systems.

Proteomics analysis of serum and urine identifies VCP and CTSA as potential biomarkers associated with multiple myeloma

AIMS

We analyzed the differentially expressed proteins (DEPs) in serum and urine in order to provide new potential biomarkers for MM.

METHODS

Data-Independent Acquisition-based proteomics of serum and urine was performed to identify potential biomarkers for MM patients. Then we performed Western Blotting (WB), ELISA along with their ROC curve analysis to confirm DEPs.

RESULTS

A total of 1653 proteins in serum and 4519 proteins in urine were identified using Data-Dependent Acquisition method. VCP was the only protein that showed significant differences in different comparison groups in both serum and urine. Pathway analysis revealed that protein processing in the endoplasmic reticulum was the most relevant pathway associated with MM. Furthermore, the increased expression of HSP90B1, VCP, CTSA, HYOU1, PDIA4, and RAB7A was detected by WB. The results of ELISA indicated that a combination of VCP and CTSA provided a high area under curve (AUC) value of 0.883 (95 % CI, 0.769-0.997, p < 0.001) to diagnose NDMM. The combination of VCP, CTSA, ALB, and HGB exhibited better performance (AUC = 0.981), with 100 % specificity and 86.7 % sensitivity.

CONCLUSION

These findings suggest VCP and CTSA exhibit potential as biomarkers for MM, which may be helpful in the molecular mechanisms and pathogenesis upon further investigation.

The NRF2-p97-NRF2 negative feedback loop

p97 is a ubiquitin-targeted ATP-dependent segregase that regulates proteostasis, in addition to a variety of other cellular functions. Previously, we demonstrated that p97 negatively regulates NRF2 by extracting ubiquitylated NRF2 from the KEAP1-CUL3-RBX1 E3 ubiquitin ligase complex, facilitating proteasomal destruction. In the current study, we identified p97 as an NRF2-target gene that contains a functional ARE, indicating the presence of an NRF2-p97-NRF2 negative feedback loop that maintains redox homeostasis. Using CRISPR/Cas9 genome editing, we generated endogenous p97 ARE-mutated BEAS-2B cell lines. These p97 ARE-mutated cell lines exhibit altered expression of p97 and NRF2, as well as a compromised response to NRF2 inducers. Importantly, we also found a positive correlation between NRF2 activation and p97 expression in human cancer patients. Finally, using chronic arsenic-transformed cell lines, we demonstrated a synergistic effect of NRF2 and p97 inhibition in killing cancer cells with high NRF2 and p97 expression. Our study suggests dual upregulation of NRF2 and p97 occurs in certain types of cancers, suggesting that inhibition of both NRF2 and p97 could be a promising treatment strategy for stratified cancer patients.

Inhibition of VCP modulates NF-κB signaling pathway to suppress multiple myeloma cell proliferation and osteoclast differentiation

Multiple myeloma (MM) is the second most common hematological malignancy, in which the dysfunction of the ubiquitin-proteasome pathway is associated with the pathogenesis. The valosin containing protein (VCP)/p97, a member of the AAA+ ATPase family, possesses multiple functions to regulate the protein quality control including ubiquitin-proteasome system and molecular chaperone. VCP is involved in the occurrence and development of various tumors while still elusive in MM. VCP inhibitors have gradually shown great potential for cancer treatment. This study aims to identify if VCP is a therapeutic target in MM and confirm the effect of a novel inhibitor of VCP (VCP20) on MM. We found that VCP was elevated in MM patients and correlated with shorter survival in clinical TT2 cohort. Silencing VCP using siRNA resulted in decreased MM cell proliferation via NF-κB signaling pathway. VCP20 evidently inhibited MM cell proliferation and osteoclast differentiation. Moreover, exosomes containing VCP derived from MM cells partially alleviated the inhibitory effect of VCP20 on cell proliferation and osteoclast differentiation. Mechanism study revealed that VCP20 inactivated the NF-κB signaling pathway by inhibiting ubiquitination degradation of IκBα. Furthermore, VCP20 suppressed MM cell proliferation, prolonged the survival of MM model mice and improved bone destruction in vivo. Collectively, our findings suggest that VCP is a novel target in MM progression. Targeting VCP with VCP20 suppresses malignancy progression of MM via inhibition of NF-κB signaling pathway.

VCP/p97, a pleiotropic protein regulator of the DNA damage response and proteostasis, is a potential therapeutic target in KRAS-mutant pancreatic cancer

We and others have recently shown that proteins involved in the DNA damage response (DDR) are critical for KRAS-mutant pancreatic ductal adenocarcinoma (PDAC) cell growth in vitro. However, the CRISPR-Cas9 library that enabled us to identify these key proteins had limited representation of DDR-related genes. To further investigate the DDR in this context, we performed a comprehensive, DDR-focused CRISPR-Cas9 loss-of-function screen. This screen identified valosin-containing protein (VCP) as an essential gene in KRAS-mutant PDAC cell lines. We observed that genetic and pharmacologic inhibition of VCP limited cell growth and induced apoptotic death. Addressing the basis for VCP-dependent growth, we first evaluated the contribution of VCP to the DDR and found that loss of VCP resulted in accumulation of DNA double-strand breaks. We next addressed its role in proteostasis and found that loss of VCP caused accumulation of polyubiquitinated proteins. We also found that loss of VCP increased autophagy. Therefore, we reasoned that inhibiting both VCP and autophagy could be an effective combination. Accordingly, we found that VCP inhibition synergized with the autophagy inhibitor chloroquine. We conclude that concurrent targeting of autophagy can enhance the efficacy of VCP inhibitors in KRAS-mutant PDAC.

GLI1, a novel target of the ER stress regulator p97/VCP, promotes ATF6f-mediated activation of XBP1

Upon accumulation of improperly folded proteins in the Endoplasmic Reticulum (ER), the Unfolded Protein Response (UPR) is triggered to restore ER homeostasis. The induction of stress genes is a sine qua non condition for effective adaptive UPR. Although this requirement has been extensively described, the mechanisms underlying this process remain in part uncharacterized. Here, we show that p97/VCP, an AAA+ ATPase known to contribute to ER stress-induced gene expression, regulates the transcription factor GLI1, a primary effector of Hedgehog (Hh) signaling. Under basal (non-ER stress) conditions, GLI1 is repressed by a p97/VCP-HDAC1 complex while upon ER stress GLI1 is induced through a mechanism requiring both USF2 binding and increase histone acetylation at its promoter. Interestingly, the induction of GLI1 was independent of ligand-regulated Hh signaling. Further analysis showed that GLI1 cooperates with ATF6f to induce promoter activity and expression of XBP1, a key transcription factor driving UPR. Overall, our work demonstrates a novel role for GLI1 in the regulation of ER stress gene expression and defines the interplay between p97/VCP, HDAC1 and USF2 as essential players in this process.

New Insights into the Structural Requirements of Isatin-Derived Pro-Apoptotic Agents against Acute Myeloid Leukemia

Searching for bioactive compounds within the huge chemical space is like trying to find a needle in a haystack. Isatin is a unique natural compound which is endowed with different bio-pertinent activities, especially in cancer therapy. Herein, we envisaged that adopting a hybrid strategy of isatin and α,β-unsaturated ketone would afford new chemical entities with strong chemotherapeutic potential. Of interest, compounds 5b and 5g demonstrated significant antiproliferative activities against different cancer genotypes according to NCI-60 screening. Concomitantly, their IC₅₀ against HL-60 cells were 0.38 ± 0.08 and 0.57 ± 0.05 µM, respectively, demonstrating remarkable apoptosis and moderate cell cycle arrest at G1 phase. Intriguingly, an impressive safety profile for 5b was reflected by a 37.2 times selectivity against HL-60 over PBMC from a healthy donor. This provoked us to further explore their mechanism of action by in vitro and in silico tools. Conclusively, 5b and 5g stand out as strong chemotherapeutic agents that hold clinical promise against acute myeloid leukemia.

In Vitro and In Silico Study to Assess Toxic Mechanisms of Hybrid Molecules of Quinone-Benzocaine as Plastoquinone Analogues in Breast Cancer Cells

We managed to obtain three different series of 2,3-dimethyl-1,4-benzoquinones, named nonhalogenated and halogenated (brominated and chlorinated) PQ analogues, via the molecular hybridization strategy. Sixteen of eighteen hybrid molecules were selected by the National Cancer Institute (NCI) of Bethesda for their in vitro antiproliferative potential against the full NCI 60 cell line panel. The hybrid molecules (BrPQ5, CIPQ1, and CIPQ3) showed good growth inhibition at 10 μM concentration, particularly against breast cancer cell lines. As per the results obtained from in vitro antiproliferative evaluation, cytotoxic activities of the hybrid molecules (BrPQ5, CIPQ1, and CIPQ3) were evaluated with an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in T47D and MCF7 breast cancer and human umbilical vein endothelial (HUVEC) cells. Molecules exhibited cytotoxic activity, and especially, CIPQ1 showed remarkable cytotoxic activity and good selectivity on T47D and MCF7 cells. Furthermore, CIPQ1 could inhibit cell proliferation, cause apoptotic cell death and disturb the cell cycle in T47D and MCF7 cells. Additionally, CIPQ1 caused oxidative stress induction in both cells, more so in T47D. In vitro study results indicated that the anticancer activity of CIPQ1 was more prominent in T47D cells than in MCF7 cells. The compound CIPQ1 showed a prominent binding with JNK3 in silico. Thus, the obtained hybrid molecules via the molecular hybridization strategy of two important pharmacophores could be useful in the discovery of novel antiproliferative agents, and CIPQ1 could be considered a promising drug candidate.

NMS-873 Leads to Dysfunctional Glycometabolism in A p97-Independent Manner in HCT116 Colon Cancer Cells

Adenosine triphosphate (ATP)–competitive p97 inhibitor CB-5339, the successor of CB-5083, is being evaluated in Phase 1 clinical trials for anti-cancer therapy. Different modes-of-action p97 inhibitors such as allosteric inhibitors are useful to overcome drug-induced resistance, one of the major problems of targeted therapy. We previously demonstrated that allosteric p97 inhibitor NMS-873 can overcome CB-5083-induced resistance in HCT116. Here we employed chemical proteomics and drug-induced thermal proteome changes to identify drug targets, in combination with drug-resistant cell lines to dissect on- and off-target effects. We found that NMS-873 but not CB-5083 affected glycometabolism. By establishing NMS-873-resistant HCT116 cell lines and performing both cell-based and proteomic analysis, we confirmed that NMS-873 dysregulates glycometabolism in a p97-independent manner. We then used proteome integral solubility alteration with a temperature-based method (PISA T) to identify NDUFAF5 as one of the potential targets of NMS-873 in the mitochondrial complex I. We also demonstrated that glycolysis inhibitor 2-DG enhanced the anti-proliferative effect of NMS-873. The polypharmacology of NMS-873 can be advantageous for anti-cancer therapy for colon cancer.

The spectrum of neurodevelopmental, neuromuscular and neurodegenerative disorders due to defective autophagy

Primary dysfunction of autophagy due to Mendelian defects affecting core components of the autophagy machinery or closely related proteins have recently emerged as an important cause of genetic disease. This novel group of human disorders may present throughout life and comprises severe early-onset neurodevelopmental and more common adult-onset neurodegenerative disorders. Early-onset (or congenital) disorders of autophagy often share a recognizable "clinical signature," including variable combinations of neurological, neuromuscular and multisystem manifestations. Structural CNS abnormalities, cerebellar involvement, spasticity and peripheral nerve pathology are prominent neurological features, indicating a specific vulnerability of certain neuronal populations to autophagic disturbance. A typically biphasic disease course of late-onset neurodegeneration occurring on the background of a neurodevelopmental disorder further supports a role of autophagy in both neuronal development and maintenance. Additionally, an associated myopathy has been characterized in several conditions. The differential diagnosis comprises a wide range of other multisystem disorders, including mitochondrial, glycogen and lysosomal storage disorders, as well as ciliopathies, glycosylation and vesicular trafficking defects. The clinical overlap between the congenital disorders of autophagy and these conditions reflects the multiple roles of the proteins and/or emerging molecular connections between the pathways implicated and suggests an exciting area for future research. Therapy development for congenital disorders of autophagy is still in its infancy but may result in the identification of molecules that target autophagy more specifically than currently available compounds. The close connection with adult-onset neurodegenerative disorders highlights the relevance of research into rare early-onset neurodevelopmental conditions for much more common, age-related human diseases.Abbreviations: AC: anterior commissure; AD: Alzheimer disease; ALR: autophagic lysosomal reformation; ALS: amyotrophic lateral sclerosis; AMBRA1: autophagy and beclin 1 regulator 1; AMPK: AMP-activated protein kinase; ASD: autism spectrum disorder; ATG: autophagy related; BIN1: bridging integrator 1; BPAN: beta-propeller protein associated neurodegeneration; CC: corpus callosum; CHMP2B: charged multivesicular body protein 2B; CHS: Chediak-Higashi syndrome; CMA: chaperone-mediated autophagy; CMT: Charcot-Marie-Tooth disease; CNM: centronuclear myopathy; CNS: central nervous system; DNM2: dynamin 2; DPR: dipeptide repeat protein; DVL3: disheveled segment polarity protein 3; EPG5: ectopic P-granules autophagy protein 5 homolog; ER: endoplasmic reticulum; ESCRT: homotypic fusion and protein sorting complex; FIG4: FIG4 phosphoinositide 5-phosphatase; FTD: frontotemporal dementia; GBA: glucocerebrosidase; GD: Gaucher disease; GRN: progranulin; GSD: glycogen storage disorder; HC: hippocampal commissure; HD: Huntington disease; HOPS: homotypic fusion and protein sorting complex; HSPP: hereditary spastic paraparesis; LAMP2A: lysosomal associated membrane protein 2A; MEAX: X-linked myopathy with excessive autophagy; mHTT: mutant huntingtin; MSS: Marinesco-Sjoegren syndrome; MTM1: myotubularin 1; MTOR: mechanistic target of rapamycin kinase; NBIA: neurodegeneration with brain iron accumulation; NCL: neuronal ceroid lipofuscinosis; NPC1: Niemann-Pick disease type 1; PD: Parkinson disease; PtdIns3P: phosphatidylinositol-3-phosphate; RAB3GAP1: RAB3 GTPase activating protein catalytic subunit 1; RAB3GAP2: RAB3 GTPase activating non-catalytic protein subunit 2; RB1: RB1-inducible coiled-coil protein 1; RHEB: ras homolog, mTORC1 binding; SCAR20: SNX14-related ataxia; SENDA: static encephalopathy of childhood with neurodegeneration in adulthood; SNX14: sorting nexin 14; SPG11: SPG11 vesicle trafficking associated, spatacsin; SQSTM1: sequestosome 1; TBC1D20: TBC1 domain family member 20; TECPR2: tectonin beta-propeller repeat containing 2; TSC1: TSC complex subunit 1; TSC2: TSC complex subunit 2; UBQLN2: ubiquilin 2; VCP: valosin-containing protein; VMA21: vacuolar ATPase assembly factor VMA21; WDFY3/ALFY: WD repeat and FYVE domain containing protein 3; WDR45: WD repeat domain 45; WDR47: WD repeat domain 47; WMS: Warburg Micro syndrome; XLMTM: X-linked myotubular myopathy; ZFYVE26: zinc finger FYVE-type containing 26.

Phenotype of VCP Mutations in Chinese Amyotrophic Lateral Sclerosis Patients

Mutations in the valosin-containing protein (VCP) gene have been linked to amyotrophic lateral sclerosis (ALS) in the Caucasian populations. However, the phenotype of VCP mutations in Chinese patients with (ALS) remains unclear. Targeted next-generation sequencing covered 28 ALS-related genes including the VCP gene was undertaken to screen in a Chinese cohort of 275 sporadic ALS cases and 15 familial ALS pedigrees. An extensive literature review was performed to identify all patients with ALS carrying VCP mutations previously reported. The clinical characteristics and genetic features of ALS patients with VCP mutations were reviewed. One known p.R155C mutation in the VCP gene was detected in two siblings from a familial ALS pedigree and two sporadic individuals. In addition, the same VCP p.R155C mutation was detected in an additional patient with ALS referred in 2021. Three patients with VCP p.R155C mutation presented with muscular weakness starting from proximal extremities to distal extremities. The other patient developed a phenotype of Paget's disease of bone in addition to the progressive muscular atrophy. We reported the first VCP mutation carrier manifesting ALS with Paget's disease of bone in the Chinese population. Our findings expand the phenotypic spectrum of the VCP mutations in Chinese patients with ALS and suggest that ALS patients with VCP p.R155C mutations tend to present with relatively young onset, symmetrical involvement of proximal muscles weakness of arms or legs, and then progressed to distal muscles of limbs.

Valosin-Containing Protein (VCP)/p97: A Prognostic Biomarker and Therapeutic Target in Cancer

Valosin-containing protein (VCP)/p97, a member of the AAA+ ATPase family, is a molecular chaperone recruited to the endoplasmic reticulum (ER) membrane by binding to membrane adapters (nuclear protein localization protein 4 (NPL4), p47 and ubiquitin regulatory X (UBX) domain-containing protein 1 (UBXD1)), where it is involved in ER-associated protein degradation (ERAD). However, VCP/p97 interacts with many cofactors to participate in different cellular processes that are critical for cancer cell survival and aggressiveness. Indeed, VCP/p97 is reported to be overexpressed in many cancer types and is considered a potential cancer biomarker and therapeutic target. This review summarizes the role of VCP/p97 in different cancers and the advances in the discovery of small-molecule inhibitors with therapeutic potential, focusing on the challenges associated with cancer-related VCP mutations in the mechanisms of resistance to inhibitors.

A New Series of Antileukemic Agents: Design, Synthesis, In Vitro and In Silico Evaluation of Thiazole-Based ABL1 Kinase Inhibitors

BACKGROUND

After the approval of imatinib, more than 25 antitumor agents targeting kinases have been approved, and several promising candidates are at various stages of clinical evaluation.

OBJECTIVES

Due to the importance of the thiazole scaffold in targeted anticancer drug discovery, the goal of this work is to identify new thiazolyl hydrazones as potent ABL1 kinase inhibitors for the management of Chronic Myeloid Leukemia (CML).

METHODS

New thiazolyl hydrazones (2a-p) were synthesized and investigated for their cytotoxic effects on the K562 CML cell line. Compounds 2h, 2j and 2l showed potent anticancer activity against K562 cell line. The cytotoxic effects of these compounds on other leukemia (HL-60, MT-2 and Jurkat) and HeLa human cervical carcinoma cell lines were also investigated. Furthermore, their cytotoxic effects on Mitogen-Activated Peripheral Blood Mononuclear Cells (MA-PBMCs) were evaluated to determine their selectivity. Due to its selective and potent anticancer activity, compound 2j was benchmarked for its apoptosis-inducing potential on K562 cell line and inhibitory effects on eight different Tyrosine Kinases (TKs), including ABL1 kinase. In order to investigate the binding mode of compound 2j into the ATP binding site of ABL1 kinase (PDB: 1IEP), a molecular docking study was conducted using MOE 2018.01 program. The QikProp module of Schrödinger's Molecular modelling package was used to predict the pharmacokinetic properties of compounds 2a-p.

RESULTS

4-(4-(Methylsulfonyl)phenyl)-2-[2-((1,3-benzodioxol-4-yl)methylene)hydrazinyl]thiazole (2j) showed antiproliferative activity against K562 cell line with an IC₅₀ value of 8.87±1.93 μM similar to imatinib (IC50= 6.84±1.11μM). Compound 2j was found to be more effective than imatinib on HL-60, Jurkat and MT-2 cells. Compound 2j also showed cytotoxic activity against HeLa cell line similar to imatinib. The higher selectivity index value of compound 2j than imatinib indicated that its antiproliferative activity was selective. Compound 2j also induced apoptosis in K562 cell line more than imatinib. Among eight TKs, compound 2j showed the strongest inhibitory activity against ABL1 kinase enzyme (IC₅₀= 5.37±1.17μM). According to molecular docking studies, compound 2j exhibited high affinity to the ATP binding site of ABL1 kinase, forming significant intermolecular interactions. On the basis of in silico studies, this compound did not violate Lipinski's rule of five and Jorgensen's rule of three.

CONCLUSION

Compound 2j stands out as a potential orally bioavailable ABL1 kinase inhibitor for the treatment of CML.

Ubiquitin proteasome system and autophagy associated proteins in human testicular tumors

Ubiquitin proteasome sytem (UPS) and autophagy govern protein quality control by degradation and clearance of damaged proteins. Many proteins working in these pathways such as p97/VCP, Ubiquitin (Ub), Jab1/CSN5, p62, LC3B and Beclin 1 are known to be essential for different pathological conditions, especially in cancer, but their expression in human testicular tumors has not been characterized yet. In the present study, we aimed to investigate the expression of UPS (p97/VCP, Ubiquitin, Jab1/CSN5) and autophagic (p62, LC3B, Beclin 1) proteins in human testicular tumors and cancer adjacent normal testicular tissues. We used an immunohistochemical staining technique. 120 cases of testicular germ and non-germ cell tumors, which are 42 seminomas, 31 embryonal carcinomas, 11 yolk sac tumors, 25 intratubular germ cell neoplasms, 6 Leydig cell tumors, 5 Sertoli cell tumors, were collected and evaluated on tissue microarray. For the first time, the expression of p97/VCP, Ub, Jab1/CSN5, p62, LC3B and Beclin 1 in different type of human testicular tumors has been confirmed. We found that p97/VCP, Ub and Jab1/CSN5 were frequently expressed at higher levels in testicular tumours. In contrast to UPS markers, p62, LC3B and Beclin 1 showed significantly diminished expressions in testicular tumors. Accordingly, a negative correlation between p97/VCP and autophagic markers (p62 and LC3B) was found, suggesting a relationship between UPS and autophagy in different type of testicular tumors. The current results displayed elevated level of p97/VCP, Ub and Jab1/CSN5 expressions in contrast to the diminished expression of p62, LC3B and Beclin 1 in human testicular tumors, thereby supporting a correlation between p97/VCP and autophagic markers in testicular tumors.

Disruption of p97/VCP induces autophagosome accumulation, cell cycle arrest and apoptosis in human choriocarcinoma cells

Gestational choriocarcinoma is aggressive trophoblastic disease. The development, progression and the cure of this disease is not well-established. p97/Valosin containing protein has been shown to play critical roles in many cellular processes. In various cancers, higher expression of p97/VCP has been reported and targeting of p97/VCP with its spesific inhibitors or siRNA's (siVCP) in cancer therapy was suggested. However, no study is avaible about the expression and function of p97/VCP in gestational choriocarcinoma. Hence, the aim of the study was to evaluate effects of p97/VCP inhibitor, DBeQ and siVCP on choriocarcinoma cells. We use human placental choriocarcinoma cell line (Jeg3) as model to find out the effects of DBeQ and VCP siRNA's (siVCP) on apoptotic and autophagic pathway by immunflouroscence staining, Western blotting, qPCR and flow-cytometry. p97/VCP siRNA's and DBeQ induced accumulation of autophagic proteins, LC3II and p62 in the cytoplasm of Jeg3 cells detected. Concurrently, Jeg3 cells treated with DBeQ and siVCP demonstrated G0/G1 cell cycle arrest, accompanied by accumulation of poly-ubiquitinated proteins. Moreover, disruption of p97/VCP by siRNA and DBeQ inhibited cancer cell growth managing the caspases-3 and -7. Our results show that inhibition of p97/VCP activity with DBeQ and depletion of p97/VCP expression with siRNA in Jeg3 cells induce caspase activation, inhibits cell proliferation and leads to a defect in autophagosome maturation, thus providing potential target for the prevention and treatment of choriocarcinoma.

A covalent p97/VCP ATPase inhibitor can overcome resistance to CB-5083 and NMS-873 in colorectal cancer cells

Small-molecule inhibitors of p97 are useful tools to study p97 function. Human p97 is an important AAA ATPase due to its diverse cellular functions and implication in mediating the turnover of proteins involved in tumorigenesis and virus infections. Multiple p97 inhibitors identified from previous high-throughput screening studies are thiol-reactive compounds targeting Cys522 in the D2 ATP-binding domain. Thus, these findings suggest a potential strategy to develop covalent p97 inhibitors. We first used purified p97 to assay several known covalent kinase inhibitors to determine if they can inhibit ATPase activity. We evaluated their selectivity using our dual reporter cells that can distinguish p97 dependent and independent degradation. We selected a β-nitrostyrene scaffold to further study the structure-activity relationship. In addition, we used p97 structures to design and synthesize analogues of pyrazolo[3,4-d]pyrimidine (PP). We incorporated electrophiles into a PP-like compound 17 (4-amino-1-tert-butyl-3-phenyl pyrazolo[3,4-d]pyrimidine) to generate eight compounds. A selective compound 18 (N-(1-(tert-butyl)-3-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4-yl)acrylamide, PPA) exhibited excellent selectivity in an in vitro ATPase activity assay: IC₅₀ of 0.6 μM, 300 μM, and 100 μM for wild type p97, yeast Cdc48, and N-ethylmaleimide sensitive factor (NSF), respectively. To further examine the importance of Cys522 on the active site pocket during PPA inhibition, C522A and C522T mutants of p97 were purified and shown to increase IC₅₀ values by 100-fold, whereas replacement of Thr532 of yeast Cdc48 with Cysteine decreased the IC₅₀ by 10-fold. The molecular modeling suggested the hydrogen bonds and hydrophobic interactions in addition to the covalent bonding at Cys522 between WT-p97 and PPA. Furthermore, tandem mass spectrometry confirmed formation of a covalent bond between Cys522 and PPA. An anti-proliferation assay indicated that the proliferation of HCT116, HeLa, and RPMI8226 was inhibited by PPA with IC₅₀ of 2.7 μM, 6.1 μM, and 3.4 μM, respectively. In addition, PPA is able to inhibit proliferation of two HCT116 cell lines that are resistant to CB-5083 and NMS-873, respectively. Proteomic analysis of PPA-treated HCT116 revealed Gene Ontology enrichment of known p97 functional pathways such as the protein ubiquitination and the ER to Golgi transport vesicle membrane. In conclusion, we have identified and characterized PPA as a selective covalent p97 inhibitor, which will allow future exploration to improve the potency of p97 inhibitors with different mechanisms of action.

Interplay between endoplasmic reticulum stress and non-coding RNAs in cancer

To survive, cancer cells are subjected to various internal and external adverse factors, including genetic mutations, hypoxia, nutritional deficiencies, and drug toxicity. All of these factors result in the accumulation of unfolded proteins in the endoplasmic reticulum, which leads to a condition termed endoplasmic reticulum stress (ER stress) and triggers the unfolded protein response (UPR). UPR downstream components strictly control transcription and translation reprogramming to ensure selective gene expression, including that of non-coding RNA (ncRNAs), to adapt to adverse environments. NcRNAs, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), play important roles in regulating target gene expression and protein translation, and their aberrant expression is related to tumor development. Dysregulation of ncRNAs is involved in the regulation of various cellular characteristics of cancer cells, including growth, apoptosis, metastasis, angiogenesis, drug sensitivity, and tumor stem cell properties. Notably, ncRNAs and ER stress can regulate each other and collaborate to determine the fate of tumor cells. Therefore, investigating the interaction between ER stress and ncRNAs is crucial for developing effective cancer treatment and prevention strategies. In this review, we summarize the ER stress-triggered UPR signaling pathways involved in carcinogenesis followed by the mutual regulation of ER stress and ncRNAs in cancer, which provide further insights into the understanding of tumorigenesis and therapeutic strategies.

Structure activity study of S-trityl-cysteamine dimethylaminopyridine derivatives as SIRT2 inhibitors: Improvement of SIRT2 binding and inhibition

Sirtuin proteins are a highly conserved class of nicotinamide adenine dinucleotide (NAD+)-dependent lysine deacylases. The pleiotropic human isoform 2 of Sirtuins (SIRT2) has been engaged in the pathogenesis of cancer in a plethora of reports around the globe. Thus, SIRT2 modulation is deemed as a promising approach for pharmaceutical intervention. Previously, we reported S-Trityl-l-Cysteine (STLC)-ornamented dimethylaminopyridine chemical entity named STC4 with a significant SIRT2 inhibitory capacity; this was separate from the conventional application of STLC scaffold as a kinesin-5 inhibitor. An interactive molecular docking study of SIRT2 and STC4 showed interaction between Asn168 of SIRT2 and the methyl ester of STC4, that appears to hinder STC4 to reach the selective pocket of the protein unlike strong SIRT2 inhibitor SirReal2. To improve its activity, herein, we utilized S-trityl cysteamine pharmacophore lacking the methyl ester. Nine compounds were synthesized and assayed affording three biopertinent SIRT2 inhibitors, and two of them, STCY1 and STCY6 showed higher inhibitory activity than STC4. These compounds have pronounced anti-proliferative activities against different cancer cell lines. A molecular docking study was executed to shed light on the supposed binding mode of the lead compound, STCY1, into the selective pocket of SIRT2 by interaction of the nitrogen of pyridine ring of the compound and Ala135 of the protein. The outcome of the study exposes that the active compounds are effective intermediates to construct more potent biological agents.

Radwan M, E. Ozturk S, Ulusoy NG, Sozer E, E. Ellakwa D, Ocak Z, Can M, F.S. Ali T, I. Abd-Alla H, Yayli N, Tateishi H, Otsuka M, Fujita M. Design, Synthesis and Biological Evaluation of Pentacyclic Triterpene Derivatives: Optimization of Anti-ABL Kinase Activity

Imatinib, an Abelson (ABL) tyrosine kinase inhibitor, is a lead molecular-targeted drug against chronic myelogenous leukemia (CML). To overcome its resistance and adverse effects, new inhibitors of ABL kinase are needed. Our previous study showed that the benzyl ester of gypsogenin (1c), a pentacyclic triterpene, has anti-ABL kinase and a subsequent anti-CML activity. To optimize its activities, benzyl esters of carefully selected triterpenes (PT1-PT6), from different classes comprising oleanane, ursane and lupane, and new substituted benzyl esters of gypsogenin (GP1-GP5) were synthesized. All of the synthesized compounds were purified and charachterized by different spectroscopic methods. Cytotoxicity of the parent triterpenes and the synthesized compounds against CML cell line K562 was examined; revealing three promising compounds PT5, GP2 and GP5 (IC50 5.46, 4.78 and 3.19 μM, respectively). These compounds were shown to inhibit extracellular signal-regulated kinase (ERK) downstream signaling, and induce apoptosis in K562 cells. Among them, PT5 was identified to have in vitro activity (IC50 = 1.44 μM) against ABL1 kinase, about sixfold of 1c, which was justified by molecular docking. The in vitro activities of GP2 and GP5 are less than PT5, hence they were supposed to possess other more mechanisms of cytotoxicity. In general, our design and derivatizations resulted in enhancing the activity against ABL1 kinase and CML cells.

Antiproliferative S-Trityl-l-Cysteine -Derived Compounds as SIRT2 Inhibitors: Repurposing and Solubility Enhancement

S-trityl-l-cysteine (STLC) is a well-recognized lead compound known for its anticancer activity owing to its potent inhibitory effect on human mitotic kinesin Eg5. STLC contains two free terminal amino and carboxyl groups that play pivotal roles in binding to the Eg5 pocket. On the other hand, such a zwitterion structure complicates the clinical development of STLC because of the solubility issues. Masking either of these radicals reduces or abolishes STLC activity against Eg5. We recently identified and characterized a new class of nicotinamide adenine dinucleotide-dependent deacetylase isoform 2 of sirtuin protein (SIRT2) inhibitors that can be utilized as cytotoxic agents based on an S-trityl-l-histidine scaffold. Herein, we propose new STLC-derived compounds that possess pronounced SIRT2 inhibition effects. These derivatives contain modified amino and carboxyl groups, which conferred STLC with SIRT2 bioactivity, representing an explicit repurposing approach. Compounds STC4 and STC11 exhibited half maximal inhibitory concentration values of 10.8 ± 1.9 and 9.5 ± 1.2 μM, respectively, against SIRT2. Additionally, introduction of the derivatizations in this study addressed the solubility limitations of free STLC, presumably due to interruption of the zwitterion structure. Therefore, we could obtain drug-like STLC derivatives that work by a new mechanism of action. The new derivatives were designed, synthesized, and their structure was confirmed using different spectroscopic approaches. In vitro and cellular bioassays with various cancer cell lines and in silico molecular docking and solubility calculations of the synthesized compounds demonstrated that they warrant attention for further refinement of their bioactivity.

Novel p97/VCP inhibitor induces endoplasmic reticulum stress and apoptosis in both bortezomib-sensitive and -resistant multiple myeloma cells

p97/VCP is an endoplasmic reticulum (ER)‐associated protein that belongs to the AAA (ATPases associated with diverse cellular activities) ATPase family. It has a variety of cellular functions including ER‐associated protein degradation, autophagy, and aggresome formation. Recent studies have shown emerging roles of p97/VCP and its potential as a therapeutic target in several cancer subtypes including multiple myeloma (MM). We conducted a cell‐based compound screen to exploit novel small compounds that have cytotoxic activity in myeloma cells. Among approximately 2000 compounds, OSSL_325096 showed relatively strong antiproliferative activity in MM cell lines (IC₅₀, 100‐500 nmol/L). OSSL_325096 induced apoptosis in myeloma cell lines, including a bortezomib‐resistant cell line and primary myeloma cells purified from patients. Accumulation of poly‐ubiquitinated proteins, PERK, CHOP, and IREα, was observed in MM cell lines treated with OSSL_325096, suggesting that it induces ER stress in MM cells. OSSL_325096 has a similar chemical structure to DBeQ, a known p97/VCP inhibitor. Knockdown of the gene encoding p97/VCP induced apoptosis in myeloma cells, accompanied by accumulation of poly‐ubiquitinated protein. IC₅₀ of OSSL_325096 to myeloma cell lines were found to be lower (0.1‐0.8 μmol/L) than those of DBeQ (2‐5 μmol/L). In silico protein–drug‐binding simulation suggested possible binding of OSSL_325096 to the ATP binding site in the D2 domain of p97/VCP. In cell‐free ATPase assays, OSSL_325096 showed dose‐dependent inhibition of p97/VCP ATPase activity. Finally, OSSL_325096 inhibited the growth of subcutaneous myeloma cell tumors in vivo. The present data suggest that OSSL_325096 exerts anti‐myeloma activity, at least in part through p97/VCP inhibition.