The dual role of BI 2536, a small-molecule inhibitor that targets PLK1, in induction of apoptosis and attenuation of autophagy in neuroblastoma cells

Comprehensive quantifications of tumour microenvironment to predict the responsiveness to immunotherapy and prognosis for paediatric neuroblastomas

Treatment strategies for paediatric neuroblastoma as well as many other cancers are limited by the unfavourable tumour microenvironment (TME). In this study, the TMEs of neuroblastoma were grouped by their genetic signatures into four distinct subtypes: immune enriched, immune desert, non-proliferative and fibrotic. An Immune Score and a Proliferation Score were constructed based on the molecular features of the subtypes to quantify the immune microenvironment or malignancy degree of cancer cells in neuroblastoma, respectively. The Immune Score correlated with a patient's response to immunotherapy; the Proliferation Score was an independent prognostic biomarker for neuroblastoma and proved to be more accurate than the existing clinical predictors. This double scoring system was further validated and the conserved molecular pattern associated with immune landscape and malignancy degree was confirmed. Axitinib and BI-2536 were confirmed as candidate drugs for neuroblastoma by the double scoring system. Both in vivo and in vitro experiments demonstrated that axitinib-induced pyroptosis of neuroblastoma cells activated anti-tumour immunity and inhibited tumour growth; BI-2536 induced cell cycle arrest at the S phase in neuroblastoma cells. The comprehensive double scoring system of neuroblastoma may predict prognosis and screen for therapeutic strategies which could provide personalized treatments.

Identification of naphthalimide-derivatives as novel PBD-targeted polo-like kinase 1 inhibitors with efficacy in drug-resistant lung cancer cells

Targeting polo-box domain (PBD) small molecule for polo-like kinase 1 (PLK1) inhibition is a viable alternative to target kinase domain (KD), which could avoid pan-selectivity and dose-limiting toxicity of ATP-competitive inhibitors. However, their efficacy in these settings is still low and inaccessible to clinical requirement. Herein, we utilized a structure-based high-throughput virtual screen to find novel chemical scaffold capable of inhibiting PLK1 via targeting PBD and identified an initial hit molecule compound 1a. Based on the lead compound 1a, a structural optimization approach was carried out and several series of derivatives with naphthalimide structural motif were synthesized. Compound 4Bb was identified as a new potent PLK1 inhibitor with a KD value of 0.29 μM. 4Bb could target PLK1 PBD to inhibit PLK1 activity and subsequently suppress the interaction of PLK1 with protein regulator of cytokinesis 1 (PRC1), finally leading to mitotic catastrophe in drug-resistant lung cancer cells. Furthermore, 4Bb could undergo nucleophilic substitution with the thiol group of glutathione (GSH) to disturb the redox homeostasis through exhausting GSH. By regulating cell cycle machinery and increasing cellular oxidative stress, 4Bb exhibited potent cytotoxicity to multiple cancer cells and drug-resistant cancer cells. Subcutaneous and oral administration of 4Bb could effectively inhibit the growth of drug-resistant tumors in vivo, doubling the survival time of tumor bearing mice without side effects in normal tissues. Thus, our study offers an orally-available, structurally-novel PLK1 inhibitor for drug-resistant lung cancer therapy.

A machine learning and live-cell imaging tool kit uncovers small molecules induced phospholipidosis

Drug-induced phospholipidosis (DIPL), characterized by excessive accumulation of phospholipids in lysosomes, can lead to clinical adverse effects. It may also alter phenotypic responses in functional studies using chemical probes. Therefore, robust methods are needed to predict and quantify phospholipidosis (PL) early in drug discovery and in chemical probe characterization. Here, we present a versatile high-content live-cell imaging approach, which was used to evaluate a chemogenomic and a lysosomal modulation library. We trained and evaluated several machine learning models using the most comprehensive set of publicly available compounds and interpreted the best model using SHapley Additive exPlanations (SHAP). Analysis of high-quality chemical probes extracted from the Chemical Probes Portal using our algorithm revealed that closely related molecules, such as chemical probes and their matched negative controls can differ in their ability to induce PL, highlighting the importance of identifying PL for robust target validation in chemical biology.

Design, synthesis, and biological evaluation of novel dihydropteridone derivatives possessing oxadiazoles moiety as potent inhibitors of PLK1

Polo like kinase 1 (PLK1) is a serine/threonine kinase that is widely distributed in eukaryotic cells and plays an important role in multiple phases of the cell cycle. Its importance in tumorigenesis has been increasingly recognized in recent years. Herein, we describe the optimization of a series of novel dihydropteridone derivatives (13a-13v and 21g-21l) possessing oxadiazoles moiety as potent inhibitors of PLK1. Compound 21g exhibited improved PLK1 inhibitory capability with an IC₅₀ value of 0.45 nM and significant anti-proliferative activities against four tumor-derived cell lines (MCF-7 IC₅₀ = 8.64 nM, HCT-116 IC₅₀ = 26.0 nM, MDA-MB-231 IC₅₀ = 14.8 nM and MV4-11 IC₅₀ = 47.4 nM) with better pharmacokinetic characteristics than BI2536 in mice (AUC_0-t = 11 227 ng h mL^-1vs 556 ng h mL^-1). Moreover, 21g exhibited moderate liver microsomal stability and excellent pharmacokinetic profile (AUC_0-t = 11227 ng h mL^-1, oral bioavailability of 77.4%) in Balb/c mice, acceptable PPB, improved PLK1 inhibitory selectivity, and no apparent toxicity was observed in the acute toxicity assay (20 mg/kg). Further investigation showed that 21 g could arrest HCT-116 cells in G2 phase and induce apoptosis in a dose-dependent manner. These results indicate that 21g is a promising PLK1 inhibitor.

PLK1 inhibition promotes apoptosis and DNA damage in glioma stem cells by regulating the nuclear translocation of YBX1

Glioma stem cells (GSCs) are the important cause of tumorigenesis, recurrence, and chemo(radio)resistance in glioma. Targeting GSCs helps improve the outcomes of glioma treatment. Polo-like kinase 1 (PLK1) is a member of the serine/threonine protein kinase family, which is highly conserved. In recent years, it has been suggested that increased levels of PLK1 and its activity are associated with tumor progression and poor prognosis. We aimed to identify whether PLK1 plays a critical role in stemness maintenance and apoptosis regulation in GSCs. Here we identify that PLK1 inhibition can induce apoptosis and DNA damage of GSCs, we have also delineat the possible underlying molecular mechanisms: PLK1 interacts with YBX1 and directly phosphorylates serine 174 and serine 176 of YBX1. Inhibition of PLK1 reduces the phosphorylation level of YBX1, and decreased phosphorylation of YBX1 prevents its nuclear translocation, thereby inducing apoptosis and DNA damage of GSCs. We confirmed that YBX1 knockdown resulted in the apoptosis and DNA damage of GSCs. These findings uncover that PLK1 inhibition induces cell apoptosis and DNA damage in GSCs through YBX1 phosphorylation, providing new insights into the mechanism by which PLK1 inhibition contributes to the apoptosis of and DNA damage in gliomas.

Drugging Hijacked Kinase Pathways in Pediatric Oncology: Opportunities and Current Scenario

Childhood cancer is considered rare, corresponding to ~3% of all malignant neoplasms in the human population. The World Health Organization (WHO) reports a universal occurrence of more than 15 cases per 100,000 inhabitants around the globe, and despite improvements in diagnosis, treatment and supportive care, one child dies of cancer every 3 min. Consequently, more efficient, selective and affordable therapeutics are still needed in order to improve outcomes and avoid long-term sequelae. Alterations in kinases' functionality is a trademark of cancer and the concept of exploiting them as drug targets has burgeoned in academia and in the pharmaceutical industry of the 21st century. Consequently, an increasing plethora of inhibitors has emerged. In the present study, the expression patterns of a selected group of kinases (including tyrosine receptors, members of the PI3K/AKT/mTOR and MAPK pathways, coordinators of cell cycle progression, and chromosome segregation) and their correlation with clinical outcomes in pediatric solid tumors were accessed through the R2: Genomics Analysis and Visualization Platform and by a thorough search of published literature. To further illustrate the importance of kinase dysregulation in the pathophysiology of pediatric cancer, we analyzed the vulnerability of different cancer cell lines against their inhibition through the Cancer Dependency Map portal, and performed a search for kinase-targeted compounds with approval and clinical applicability through the CanSAR knowledgebase. Finally, we provide a detailed literature review of a considerable set of small molecules that mitigate kinase activity under experimental testing and clinical trials for the treatment of pediatric tumors, while discuss critical challenges that must be overcome before translation into clinical options, including the absence of compounds designed specifically for childhood tumors which often show differential mutational burdens, intrinsic and acquired resistance, lack of selectivity and adverse effects on a growing organism.

BRD4 PROTAC degrader MZ1 exerts anticancer effects in acute myeloid leukemia by targeting c-Myc and ANP32B genes

Acute myeloid leukemia (AML) is a highly cancerous and aggressive hematologic disease with elevated levels of drug resistance and relapse resulting in high mortality. Recently, bromodomains and extra-terminal (BET) protein inhibitors have been extensively researched in hematological tumors as potential anticancer agents. MZ1 is a novel BET inhibitor that mediates selective proteins degradation and suppression of tumor growth through proteolysis-targeting chimeras (PROTAC) technology. Accordingly, this study aimed to investigate the role and therapeutic potential of MZ1 in AML. In this study, we first identified that AML patients with high BRD4 expression had poor overall survival than those with low expression group. MZ1 inhibited AML cell growth and induced apoptosis and cycle arrest in vitro. MZ1 induced degradation of BRD4, BRD3 and BRD2 in AML cell strains. Additionally, MZ1 also initiated the cleavage of poly-ADP-ribose polymerase (PARP), which showed cytotoxic effects on NB4 (PML-RARa), K562 (BCR-ABL), Kasumi-1 (AML1-ETO), and MV4-11 (MLL-AF4) cell lines representing different molecular subtypes of AML. In AML mouse leukemia model, MZ1 significantly decreased leukemia cell growth and increased the mouse survival time. According to the RNA-sequencing analysis, MZ1 led to c-Myc and ANP32B genes significant downregulation in AML cell lines. Knockdown of ANP32B promoted AML cell apoptosis and inhibited cell growth. Overall, our data indicated that MZ1 had broad anti-cancer effects on AML cell lines with different molecular lesions, which might be exploited as a novel therapeutic strategy for AML patients.

HN1L/AP-2γ/PLK1 signaling drives tumor progression and chemotherapy resistance in esophageal squamous cell carcinoma

Hematological and neurological expressed 1 like (HN1L) is a newly identified oncogene in lung cancer and hepatocellular carcinoma recently identified by our team, but its roles in the development and treatment of esophageal squamous cell carcinoma (ESCC) remain incompletely cataloged. Here, using ESCC tissue array and public database analysis, we demonstrated that HN1L was highly expressed in ESCC tissues, which was associated with tumor tissue invasion, poor clinical stage and short survival for ESCC patients. Loss- and gain-of-function studies in ESCC cells revealed that HN1L enhances ESCC cell metastasis and proliferation in vitro and in mice models. Moreover, high level of HN1L reduces the sensibility of ESCC cells to chemotherapeutic drugs, such as Docetaxel. Mechanism studies revealed that HN1L activated the transcription of polo-like kinase 1 (PLK1) by interacting with transcription factor AP-2γ, which increased the expression of malignancy related proteins Cyclin D1 and Slug in ESCC cells. Blocking PLK1 with inhibitor BI-2356 abrogated the oncogenic function of HN1L and significantly suppressed ESCC progression by combining with chemotherapy. Therefore, this study demonstrates the vital pro-tumor role of HN1L/AP-2γ/PLK1 signaling axis in ESCC, offering a potential therapeutic strategy for ESCC patients with high HN1L by blocking PLK1.

Construction of a Prognostic Nomogram Based on Autophagy-Related Genes for Children With Neuroblastoma

Neuroblastoma (NB) is the most common solid malignancy in children. MYCN gene amplification is the most relevant genetic alteration in patients with NB and is associated with poor prognosis. Autophagy plays specific roles in the occurrence, development, and progression of NB. Here, we aimed to identify and assess the prognostic effects of autophagy-related genes (ARGs) in patients with NB and MYCN gene amplification. Differentially expressed ARGs were identified in patients with NB with and without MYCN gene amplification, and the ARG expression patterns and related clinical data from the Therapeutically Applicable Research to Generate Effective Treatments database were used as the training cohort. Least absolute shrinkage and selection operator analyses were used to identify prognostic ARGs associated with event-free survival (EFS), and a prognostic risk score model was developed. Model performance was assessed using the Kaplan–Meier method and receiver operating characteristic (ROC) curves. The prognostic ARG mode l was verified using the validation cohort dataset, GSE49710. Finally, a nomogram was constructed by combining the ARGbased risk score with clinicopathological factors. Three ARGs (GABARAPL1, NBR1, and PINK1) were selected to build a prognostic risk score model. The EFS in the low-risk group was significantly better than that in the high-risk group in both the training and validation cohorts. A nomogram incorporating the prognostic risk score, age, and International Neuroblastoma Staging System stage showed a favorable predictive ability for EFS rates according to the area under the ROC curve at 3 years (AUC = 0.787) and 5 years (AUC = 0.787). The nomogram demonstrated good discrimination and calibration. Our risk score model for the 3 ARGs can be used as an independent prognostic factor in patients with NB and MYCN gene amplification. The model can accurately predict the 3- and 5-year survival rates.

Polo-like Kinase 1 Inhibitors in Human Cancer Therapy: Development and Therapeutic Potential

Polo-like kinase 1 (PLK1) plays an important role in a variety of cellular functions, including the regulation of mitosis, DNA replication, autophagy, and the epithelial-mesenchymal transition (EMT). PLK1 overexpression is often associated with cell proliferation and poor prognosis in cancer patients, making it a promising antitumor target. To date, at least 10 PLK1 inhibitors (PLK1i) have been entered into clinical trials, among which the typical kinase domain (KD) inhibitor BI 6727 (volasertib) was granted "breakthrough therapy designation" by the FDA in 2013. Unfortunately, many other KD inhibitors showed poor specificity, resulting in dose-limiting toxicity, which has greatly impeded their development. Researchers recently discovered many PLK1i with higher selectivity, stronger potency, and better absorption, distribution, metabolism, and elimination (ADME) characteristics. In this review, we emphasize the structure-activity relationships (SARs) of PLK1i, providing insights into new drugs targeting PLK1 for antitumor clinical practice.

Mechanisms of carcinogenic activity triggered by lysine-specific demethylase 1A

Epigenetics has emerged as a prime focus area in the field of cancer research. Lysine-specific demethylase 1A (LSD1), the first discovered histone demethylase, is mainly responsible for catalysing demethylation of histone 3 lysine 4 (H3K4) and H3K9 to activate or inhibit gene transcription. LSD1 is abnormally expressed in various cancers and participates in cancer proliferation, apoptosis, metastasis, invasion, drug resistance and other processes by interacting with regulatory factors. Therefore, it may serve as a potential therapeutic target for cancer. This review summarises the major oncogenic mechanisms mediated by LSD1 and provides a reference for developing novel and efficient anticancer strategies targeting LSD1.

A Novel BRD Family PROTAC Inhibitor dBET1 Exerts Great Anti-Cancer Effects by Targeting c-MYC in Acute Myeloid Leukemia Cells

Acute myeloid leukemia (AML) represents an aggressive hematopoietic malignancy with a prognosis inferior to that of other leukemias. Recent targeted therapies offer new opportunities to achieve better treatment outcomes. However, due to the complex heterogeneity of AML, its prognosis remains dismal. In this study, we first identified the correlation between high expression of BRD4 and overall survival of patients with AML. Targeted degradation of BRD2, BRD3, and BRD4 proteins by dBET1, a proteolysis-targeting chimera (PROTAC) against the bromodomain and extra-terminal domain (BET) family members, showed cytotoxic effects on Kasumi (AML1-ETO), NB4 (PML-RARa), THP-1 (MLL-AF9), and MV4-11 (MLL-AF4) AML cell lines representing different molecular subtypes of AML. Furthermore, we determined that dBET1 treatment arrested cell cycling and enhanced apoptosis and c-MYC was identified as the downstream target. Collectively, our results indicated that dBET1 had broad anti-cancer effects on AML cell lines with different molecular lesions and provided more benefits to patients with AML.

Synthetic Heterocyclic Derivatives as Kinase Inhibitors Tested for the Treatment of Neuroblastoma

In the last few years, small molecules endowed with different heterocyclic scaffolds have been developed as kinase inhibitors. Some of them are being tested at preclinical or clinical levels for the potential treatment of neuroblastoma (NB). This disease is the most common extracranial solid tumor in childhood and is responsible for 10% to 15% of pediatric cancer deaths. Despite the availability of some treatments, including the use of very toxic cytotoxic chemotherapeutic agents, high-risk (HR)-NB patients still have a poor prognosis and a survival rate below 50%. For these reasons, new pharmacological options are urgently needed. This review focuses on synthetic heterocyclic compounds published in the last five years, which showed at least some activity on this severe disease and act as kinase inhibitors. The specific mechanism of action, selectivity, and biological activity of these drug candidates are described, when established. Moreover, the most remarkable clinical trials are reported. Importantly, kinase inhibitors approved for other diseases have shown to be active and endowed with lower toxicity compared to conventional cytotoxic agents. The data collected in this article can be particularly useful for the researchers working in this area.

ARV-825 Demonstrates Antitumor Activity in Gastric Cancer via MYC-Targets and G2M-Checkpoint Signaling Pathways

Objective

Suppression of bromodomain and extra terminal (BET) proteins has a bright prospect to treat MYC-driven tumors. Bromodomain containing 4 (BRD4) is one of the BET proteins. ARV-825, consisting of a BRD4 inhibitor conjugated with a cereblon ligand using proteolysis-targeting chimera (PROTAC) technology, was proven to decrease the tumor growth effectively and continuously. Nevertheless, the efficacy and mechanisms of ARV-825 in gastric cancer are still poorly understood.

Methods

Cell counting kit 8 assay, lentivirus infection, Western blotting analysis, Annexin V/propidium iodide (PI) staining, RNA sequencing, a xenograft model, and immunohistochemistry were used to assess the efficacy of ARV-825 in cell level and animal model.

Results

The messenger RNA (mRNA) expression of BRD4 in gastric cancer raised significantly than those in normal tissues, which suggested poor outcome of patients with gastric cancer. ARV-825 displayed higher anticancer efficiency in gastric cancer cells than OTX015 and JQ1. ARV-825 could inhibit cell growth, inducing cell cycle block and apoptosis in vitro. ARV-825 induced degradation of BRD4, BRD2, BRD3, c-MYC, and polo-like kinase 1 (PLK1) proteins in four gastric cancer cell lines. In addition, cleavage of caspase 3 and poly-ADP-ribose polymerase (PARP) was elevated. Knockdown or overexpression CRBN could increase or decrease, respectively, the ARV-825 IC50 of gastric cancer cells. ARV-825 reduced MYC and PLK1 expression in gastric cancer cells. ARV-825 treatment significantly reduced tumor growth without toxic side effects and downregulated the expression of BRD4 in vivo.

Conclusions

High mRNA expression of BRD4 in gastric cancer indicated poor prognosis. ARV-825, a BRD4 inhibitor, could effectively suppress the growth and elevate the apoptosis of gastric cancer cells via transcription downregulation of c-MYC and PLK1. These results implied that ARV-825 could be a good therapeutic strategy to treat gastric cancer.

Modelling the Functions of Polo-Like Kinases in Mice and Their Applications as Cancer Targets with a Special Focus on Ovarian Cancer

Polo-like kinases (PLKs) belong to a five-membered family of highly conserved serine/threonine kinases (PLK1-5) that play differentiated and essential roles as key mitotic kinases and cell cycle regulators and with this in proliferation and cellular growth. Besides, evidence is accumulating for complex and vital non-mitotic functions of PLKs. Dysregulation of PLKs is widely associated with tumorigenesis and by this, PLKs have gained increasing significance as attractive targets in cancer with diagnostic, prognostic and therapeutic potential. PLK1 has proved to have strong clinical relevance as it was found to be over-expressed in different cancer types and linked to poor patient prognosis. Targeting the diverse functions of PLKs (tumor suppressor, oncogenic) are currently at the center of numerous investigations in particular with the inhibition of PLK1 and PLK4, respectively in multiple cancer trials. Functions of PLKs and the effects of their inhibition have been extensively studied in cancer cell culture models but information is rare on how these drugs affect benign tissues and organs. As a step further towards clinical application as cancer targets, mouse models therefore play a central role. Modelling PLK function in animal models, e.g., by gene disruption or by treatment with small molecule PLK inhibitors offers promising possibilities to unveil the biological significance of PLKs in cancer maintenance and progression and give important information on PLKs' applicability as cancer targets. In this review we aim at summarizing the approaches of modelling PLK function in mice so far with a special glimpse on the significance of PLKs in ovarian cancer and of orthotopic cancer models used in this fatal malignancy.

BRD4 PROTAC degrader ARV-825 inhibits T-cell acute lymphoblastic leukemia by targeting 'Undruggable' Myc-pathway genes

Background

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disease with a high risk of induction failure and poor outcomes, with relapse due to drug resistance. Recent studies show that bromodomains and extra-terminal (BET) protein inhibitors are promising anti-cancer agents. ARV-825, comprising a BET inhibitor conjugated with cereblon ligand, was recently developed to attenuate the growth of multiple tumors in vitro and in vivo. However, the functional and molecular mechanisms of ARV-825 in T-ALL remain unclear. This study aimed to investigate the therapeutic efficacy and potential mechanism of ARV-825 in T-ALL.

Methods

Expression of the BRD4 were determined in pediatric T-ALL samples and differential gene expression after ARV-825 treatment was explored by RNA-seq and quantitative reverse transcription-polymerase chain reaction. T-ALL cell viability was measured by CCK8 assay after ARV-825 administration. Cell cycle was analyzed by propidium iodide (PI) staining and apoptosis was assessed by Annexin V/PI staining. BRD4, BRD3 and BRD2 proteins were detected by western blot in cells treated with ARV-825. The effect of ARV-825 on T-ALL cells was analyzed in vivo. The functional and molecular pathways involved in ARV-825 treatment of T-ALL were verified by western blot and chromatin immunoprecipitation (ChIP).

Results

BRD4 expression was higher in pediatric T-ALL samples compared with T-cells from healthy donors. High BRD4 expression indicated a poor outcome. ARV-825 suppressed cell proliferation in vitro by arresting the cell cycle and inducing apoptosis, with elevated poly-ADP ribose polymerase and cleaved caspase 3. BRD4, BRD3, and BRD2 were degraded in line with reduced cereblon expression in T-ALL cells. ARV-825 had a lower IC50 in T-ALL cells compared with JQ1, dBET1 and OTX015. ARV-825 perturbed the H3K27Ac-Myc pathway and reduced c-Myc protein levels in T-ALL cells according to RNA-seq and ChIP. In the T-ALL xenograft model, ARV-825 significantly reduced tumor growth and led to the dysregulation of Ki67 and cleaved caspase 3. Moreover, ARV-825 inhibited cell proliferation by depleting BET and c-Myc proteins in vitro and in vivo.

Conclusions

BRD4 indicates a poor prognosis in T-ALL. The BRD4 degrader ARV-825 can effectively suppress the proliferation and promote apoptosis of T-ALL cells via BET protein depletion and c-Myc inhibition, thus providing a new strategy for the treatment of T-ALL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-01908-w.

PROTAC Bromodomain Inhibitor ARV-825 Displays Anti-Tumor Activity in Neuroblastoma by Repressing Expression of MYCN or c-Myc

Neuroblastoma (NB) is one of the most common solid tumors in childhood. To date, targeting MYCN, a well-established driver gene in high-risk neuroblastoma, is still challenging. In recent years, inhibition of bromodomain and extra terminal (BET) proteins shows great potential in multiple of Myc-driven tumors. ARV-825 is a novel BET inhibitor using proteolysis-targeting chimera (PROTAC) technology which degrades target proteins by the proteasome. In this study, we investigated the effect of ARV-825 in neuroblastoma in vitro and in vivo. Our results showed that ARV-825 treatment robustly induced proliferative suppression, cell cycle arrest, and apoptosis in NB cells. Moreover, ARV-825 efficiently depleted BET protein expression, subsequently repressing the expression of MYCN or c-Myc. In the NB xenograft model, ARV-825 profoundly reduced tumor growth and led to the downregulation of BRD4 and MYCN expression in mice. Taken together, these findings provide evidence that PROTAC BET inhibitor is an efficient way to achieve MYCN/c-Myc manipulation, and ARV-825 can be used as a potential therapeutic strategy for the treatment of neuroblastoma.