Dual inhibition of MYC and SLC39A10 by a novel natural product STAT3 inhibitor derived from Chaetomium globosum suppresses tumor growth and metastasis in gastric cancer.

Gastric cancer remains one of the most common deadly diseases and lacks effective targeted therapies. In the present study, we confirmed that the signal transducer and activator of transcription 3 (STAT3) is highly expressed and associated with a poor prognosis in gastric cancer. We further identified a novel natural product inhibitor of STAT3, termed XYA-2, which interacts specifically with the SH2 domain of STAT3 (Kd= 3.29 µM) and inhibits IL-6-induced STAT3 phosphorylation at Tyr705 and nuclear translocation. XYA-2 inhibited the viability of seven human gastric cancer cell lines with 72-h IC50 values ranging from 0.5 to 0.7 µΜ. XYA-2 at 1 µΜ inhibited the colony formation and migration ability of MGC803 (72.6% and 67.6%, respectively) and MKN28 (78.5% and 96.6%, respectively) cells. In the in vivo studies, intraperitoneal administration of XYA-2 (10 mg/kg/day, 7 days/week) significantly suppressed 59.8% and 88.8% tumor growth in the MKN28-derived xenograft mouse model and MGC803-derived orthotopic mouse model, respectively. Similar results were obtained in a patient-derived xenograft (PDX) mouse model. Moreover, XYA-2 treatment extended the survival of mice bearing PDX tumors. The molecular mechanism studies based on transcriptomics and proteomics analyses indicated that XYA-2 might exert its anticancer activity by synergistically inhibiting the expression of MYC and SLC39A10, two downstream genes of STAT3 in vitro and in vivo. Together, these findings suggested that XYA-2 may be a potent STAT3 inhibitor for treating gastric cancer, and dual inhibition of MYC and SLC39A10 may be an effective therapeutic strategy for STAT3-activated cancer.

Design and synthesis of proteolysis-targeting chimeras (PROTACs) as degraders of glutathione peroxidase 4.

Ferroptosis is a new type of regulated, non-apoptotic cell death driven by iron-dependent phospholipid peroxidation. Inducing cell ferroptosis by inactivating glutathione peroxidase 4 (GPX4) has been considered as an effective cancer treatment strategy, but only few GPX4 inhibitors have been reported to date. Targeted protein degradation is receiving increasing attention in the discovery and development of therapeutic modality, particularly proteolysis targeting chimeras (PROTACs). Herein, we reported the design, synthesis, and evaluation of different types of GPX4-targeting PROTACs using ML162 derivatives and ligands for CRBN/VHL E3 ligases. Among them, CRBN-based PROTAC GDC-11 showed a relatively balanced biological profile in GPX4 degradation (degradation rate of 33% at 10 µM), cytotoxicity (IC50 = 11.69 µM), and lipid peroxides accumulation (2-foldincreaserelatedtoDMSO), suggesting a typical characteristic of ferroptosis. In silico docking and quantum chemistry theoretical calculations provided a plausible explanation for the moderate degrading effect of these synthesized PROTACs. Overall, this work lays the foundation for subsequent studies of GPX4-targeting PROTACs, and further design and synthesis of GPX4-targeting degrader are currently in progress in our group, which will be reported in due course.

Design, Synthesis and In Vivo Fluorescence Imaging Study of a Cytochrome P450 1B1 Targeted NIR Probe Containing a Chelator Moiety.

Cytochrome P450 (CYP) 1B1 has been found to be overexpressed specifically in tumor tissues at an early stage, which makes it a potential cancer biomarker for molecular imaging. Multimodal imaging combines different imaging modalities and offers more comprehensive information. Thus, imaging probes bearing more than one kind of signal fragment have been extensively explored and display great promise. Herein, we developed a near infrared (NIR) probe with a chelator moiety targeting CYP1B1 by conjugating α-naphthoflavone (ANF) derivatives with both an NIR dye and a chelator for potential application in bimodal imaging. Enzymatic inhibitory studies demonstrated inhibitory activity against CYP1B1 and selectivity among CYP1 were successfully retained after chemical modification. Cell-based saturation studies indicated nanomolar range binding affinity between the probe and CYP1B1 overexpressed cancer cells. In vitro competitive binding assays monitored by confocal microscopy revealed that the probe could specifically accumulate in tumor cells. In vivo and ex vivo imaging studies demonstrated that the probe could effectively light-up the tumor tissues as early as 2 hours post-injection. In addition, the fluorescence was significantly blocked by co-injection of CYP1B1 inhibitor, which indicated the probe accumulation in tumor sites was due to specific binding to CYP1B1.

S3I-201 derivative incorporating naphthoquinone unit as effective STAT3 inhibitors: Design, synthesis and anti-gastric cancer evaluation.

Signal transducer and activator of transcription 3 (STAT3) is a key regulator of many human cancers and has been widely recognized as a promising target for cancer therapy. A variety of small-molecule inhibitors have been developed for targeting STAT3, and some of them are now undergoing clinical trials. S3I-201, a known STAT3 inhibitor, may block STAT3 function in cancer cells by binding to the STAT3 SH2 domain to disrupt STAT3 protein complex formation. Using S3I-201 as a starting point for drug development, we synthesized a series of new STAT3 inhibitors 9a-x in this study by introducing naphthoquinone unit, a privileged fragment in STAT3 inhibitors. Most of the compounds exhibited strong anti-proliferation activity of gastric cancer cells (MGC803, MKN28, MNK1, and AGS). The representative compound 9n (SIL-14) could effectively inhibit the colony formation and migration of gastric cancer cells MGC803, arrest the cell cycle and induce MGC803 cell apoptosis at low micromolar concentrations in vitro. In addition, SIL-14 can also inhibit the phosphorylation of STAT3 protein and significantly decrease the expression of total STAT3, suggesting that it may exert anticancer effects by blocking the STAT3 signaling pathway. These results support that SIL-14 may be a promising STAT3 inhibitor for the further development of potential anti-gastric cancer candidates.

Discovery of benzochalcone derivative as a potential antigastric cancer agent targeting signal transducer and activator of transcription 3 (STAT3).

Gastric cancer remains a significant health burden worldwide. In continuation of our previous study and development of effective small molecules against gastric cancer, a series of benzochalcone analogues involving heterocyclic molecules were synthesised and biologically evaluated in vitro and in vivo. Among them, the quinolin-6-yl substituted derivative KL-6 inhibited the growth of gastric cancer cells (HGC27, MKN28, AZ521, AGS, and MKN1) with a submicromolar to micromolar range of IC50, being the most potent one in this series. Additionally, KL-6 significantly inhibited the colony formation, migration and invasion, and effectively induced apoptosis of MKN1 cells in a concentration-dependent manner. The mechanistic study revealed that KL-6 could concentration-dependently suppress STAT3 phosphorylation, which may partly contribute to its anticancer activity. Furthermore, in vivo antitumour study on the MKN1 orthotopic tumour model showed that KL-6 effectively inhibited tumour growth (TGI of 78%) and metastasis without obvious toxicity. Collectively, compound KL-6 may support the further development of candidates for gastric cancer treatment.

Medicinal chemistry strategies to discover P-glycoprotein inhibitors: An update.

The presence of multidrug resistance (MDR) in malignant tumors is one of the primary causes of treatment failure in cancer chemotherapy. The overexpression of the ATP binding cassette (ABC) transporter, P-glycoprotein (P-gp), which significantly increases the efflux of certain anticancer drugs from tumor cells, produces MDR. Therefore, inhibition of P-gp may represent a viable therapeutic strategy to overcome cancer MDR. Over the past 4 decades, many compounds with P-gp inhibitory efficacy (referred to as first- and second-generation P-gp inhibitors) have been identified or synthesized. However, these compounds were not successful in clinical trials due to a lack of efficacy and/or untoward toxicity. Subsequently, third- and fourth-generation P-gp inhibitors were developed but dedicated clinical trials did not indicate a significant therapeutic effect. In recent years, an extraordinary array of highly potent, selective, and low-toxicity P-gp inhibitors have been reported. Herein, we provide a comprehensive review of the synthetic and natural products that have specific inhibitory activity on P-gp drug efflux as well as promising chemosensitizing efficacy in MDR cancer cells. The present review focuses primarily on the structural features, design strategies, and structure-activity relationships (SAR) of these compounds.

DMAKO-20 as a New Multitarget Anticancer Prodrug Activated by the Tumor Specific CYP1B1 Enzyme.

To reduce the pervasive toxicity of natural shikonin, alkannin, and their synthetic analogues and to enhance the selectivity of these chemotherapeutics toward cancer cells, a novel 5,8-dimethyl alkannin oxime derivative (DMAKO-20) was designed, synthesized, and evaluated for its strong antitumor activity both in vitro and in vivo. It showed potent growth inhibitory effects against HCT-15, HCT-116, and K562 cells (IC50 < 1 µM), moderate antiproliferative activity toward MDA-MB-231, HepG2, PANC, Bel7402, and MGC803 cancer cells (IC50 < 10 µM), and was nontoxic to the human normal VEC and HSF cells. In vivo efficacy studies demonstrated that DMAKO-20 (10 mg/kg, i.v. on every the other day, 8 times in 14 days) resulted in 59.3% reduction in HCT-15 xenograft volume. It was as effective as the toxic antimetabolite 5-FU but revealed neither toxicity nor death in mice. The mechanistic investigations indicated that DMAKO-20 underwent the tumor-specific CYP1B1-catalyzed bioactivation to afford nitric oxide and active naphthoquinone mono-oximes, which exhibited combined anticancer effects. It was defined as a representative of the "Multi-target Anticancer Prodrugs Activated by Specific Enzymes in cancer cells". The produced active metabolites exerted anticancer effects by the direct nucleophilic alkylation and the induction of the apoptosis of cancer cells through activation of the mitochondrial pathway. The discovery of DMAKO-20 and the illustration of its molecular mechanisms may provide a new strategy to overcome the nonselective toxicity of the current chemotherapeutics.

Cytotoxicity of Synthesized 1,4-Naphthoquinone Oxime Derivatives on Selected Human Cancer Cell Lines.

In an effort to develop potent and selective antitumor agents, a series of 1,4-naphthoquinone oxime derivatives were designed and synthesized. The cytotoxicity of these compounds were evaluated against five human cancer cell lines (colorectal cancer cell: HCT-15, breast cancer cell: MDA-MB-231, liver cancer cell: BEL-7402, colorectal cancer cell: HCT-116 and ovarian cancer cell: A2780) in vitro. Among them, compound 14 was found to be the most potent cytotoxic compound against three cell lines (MDA-MB-231, BEL-7402 and A2780) with IC50 values of 0.66±0.05, 5.11±0.12 and 8.26±0.22 µM, respectively. Additionally, the length of the side chains and the position of the substituent may also affect the cytotoxic activity of the naphthoquinone oxime derivatives. In general, compound 14 effectively inhibited breast cancer cell proliferation and may become a promising anticancer agent.

Expanding the structural diversity of Bcr-Abl inhibitors: Hybrid molecules based on GNF-2 and Imatinib.

In order to expand the structural diversity of Bcr-Abl inhibitors, twenty hybrids (series E and P) have been synthesized and characterized based on Imatinib and GNF-2. Their biological activities were evaluated in vitro against human leukemia cells. Most compounds exhibited potent antiproliferative activity against K562 cells, especially for compounds E4, E5 and E7. Furthermore, these new hybrids were also screened for Abl kinase inhibitory activity, and some of them inhibited Abl kinase with low micromolar IC50 values. In particular, compound P3 displayed the most potent activity with IC50 value of 0.017 µM comparable with that of Imatinib. Molecular docking studies indicated that these novel hybrids fitted well with the active site of Bcr-Abl. These results suggested the great potential of these compounds as novel Bcr-Abl inhibitors.

Discovery of novel Bcr-Abl inhibitors with diacylated piperazine as the flexible linker.

Forty-two compounds (series 8, 9 and 10) incorporated with diacylated piperazine have been synthesized and evaluated as novel Bcr-Abl inhibitors based on 'six-atom linker'. Five of them, 8d, 8h, 8l, 10m and 10p, displayed potent Bcr-Abl inhibitory activity comparable with Imatinib. Moreover, compounds 8e, 10q, 10s, and 10u were potent Bcr-Abl inhibitors with IC50 values at the sub-micromolecular level. Most compounds exhibited moderate to high antiproliferative activity against K562 cells. In particular, compound 9e was the most promising Bcr-Abl inhibitor. Docking studies revealed that the binding modes of these compounds were similar with Imatinib. These compounds could be considered as promising lead compounds for further optimization.

Biphenyl derivatives incorporating urea unit as novel VEGFR-2 inhibitors: design, synthesis and biological evaluation.

A series of novel biphenyl urea derivates were synthesized and investigated for their potential to inhibit vascular endothelial growth factor receptor-2 (VEGFR-2). In particular, A7, B3 and B4 displayed significant enzymatic inhibitory activities, with IC50 values of 4.06, 4.55 and 5.26 nM. Compound A7 exhibited potent antiproliferative activity on several cell lines. SAR study suggested that the introduction of methyl at ortho-position of the biphenyl urea and tertiary amine moiety could improve VEGFR-2 inhibitory activity and antitumor effects. Molecular docking indicated that the urea moiety formed four hydrogen bonds with DFG residue. These biphenyl ureas could serve as promising lead compounds for further optimization.

Discovery of novel Bcr-Abl inhibitors targeting myristoyl pocket and ATP site.

Bcr-Abl plays an essential role in the pathogenesis and development of chronic myeloid leukaemia (CML). Inhibition of Bcr-Abl has great potential for therapeutic intervention in CML. In order to obtain novel and potent Bcr-Abl inhibitors, twenty seven 4,6-disubstituted pyrimidines were synthesized and evaluated herein. The biological results indicated that four compounds of them (C4, C5, C16, and C23) were potent Bcr-Abl inhibitors which were comparable to positive control. Moreover, C4 and C5 displayed promising antiproliferative activity against K562 cells. The results suggested that these 4,6-disubstituted pyrimidines could serve as promising leads for further optimization of Bcr-Abl inhibitors.

Search for novel histone deacetylase inhibitors. Part II: design and synthesis of novel isoferulic acid derivatives.

Previously, we described the discovery of potent ferulic acid-based histone deacetylase inhibitors (HDACIs) with halogeno-acetanilide as novel surface recognition moiety (SRM). In order to improve the affinity and activity of these HDACIs, twenty seven isoferulic acid derivatives were described herein. The majority of title compounds displayed potent HDAC inhibitory activity. In particular, IF5 and IF6 exhibited significant enzymatic inhibitory activities, with IC50 values of 0.73 ± 0.08 and 0.57 ± 0.16 µM, respectively. Furthermore, these compounds showed moderate antiproliferative activity against human cancer cells. Especially, IF6 displayed promising profile as an antitumor candidate with IC50 value of 3.91 ± 0.97 µM against HeLa cells. The results indicated that these isoferulic acid derivatives could serve as promising lead compounds for further optimization.

Small molecule inhibitors targeting heat shock protein 90: An updated review.

As a molecular chaperone, heat shock protein 90 (HSP90) plays important roles in the folding, stabilization, activation, and degradation of over 500 client proteins, and is extensively involved in cell signaling, proliferation, and survival. Thus, it has emerged as an important target in a variety of diseases, including cancer, neurodegenerative diseases, and viral infections. Therefore, targeted inhibition of HSP90 provides a valuable and promising therapeutic strategy for the treatment of HSP90-related diseases. This review aims to systematically summarize the progress of research on HSP90 inhibitors in the last five years, focusing on their structural features, design strategies, and biological activities. It will refer to the natural products and their derivatives (including novobiocin derivatives, deguelin derivatives, quinone derivatives, and terpenoid derivatives), and to synthetic small molecules (including resorcinol derivatives, pyrazoles derivatives, triazole derivatives, pyrimidine derivatives, benzamide derivatives, benzothiazole derivatives, and benzofuran derivatives). In addition, the major HSP90 small-molecule inhibitors that have moved into clinical trials to date are also presented here.

Metabolomic screening of radioiodine refractory thyroid cancer patients and the underlying chemical mechanism of iodine resistance.

Radioiodine refractory (RAIR) patients do not benefit from iodine-131 therapy. Thus, timely identification of RAIR patients is critical for avoiding ineffective radioactive iodine therapy. In addition, determining the causes of iodine resistance will facilitate the development of novel treatment strategies. This study was comprised of 20 RAIR and 14 non-radioiodine refractory (non-RAIR) thyroid cancer patients. Liquid chromatography-mass spectrometry was used to identify differences in the serum metabolites of RAIR and non-RAIR patients. In addition, chemical assays were performed to determine the effects of the differential metabolites on iodine uptake. Metabolic pathway enrichment analysis of the differential metabolites revealed significant differences in the phenylalanine and tyrosine metabolic pathways. Notably, quinate and shikimic acid, metabolites of the tyrosine pathway, were significantly increased in the RAIR group. In contrast, the phenylalanine pathway metabolites, hippuric acid and 2-phenylacetamide, were markedly decreased in the RAIR group. Thyroid peroxidase plays an important role in catalyzing the iodination of tyrosine residues, while the ionic state of iodine promotes the iodination reaction. Quinate, shikimic acid, hippuric acid, and 2-phenylacetamide were found to be involved in the iodination of tyrosine, which is a key step in thyroid hormone synthesis. Specifically, quinate and shikimic acid were found to inhibit iodination, while hippuric acid and 2-phenylacetamide promoted iodination. Abnormalities in phenylalanine and tyrosine metabolic pathways are closely associated with iodine resistance. Tyrosine is required for thyroid hormone synthesis and could be a potential cause of iodine resistance.

ML162 derivatives incorporating a naphthoquinone unit as ferroptosis/apoptosis inducers: Design, synthesis, anti-cancer activity, and drug-resistance reversal evaluation.

Activating apoptosis has long been viewed as an anti-cancer process, but recently increasing evidence has accumulated that induction of ferroptosis has emerged as a promising strategy for cancer therapeutics. Glutathione peroxidase 4 (GPX4) is one of the pivotal factors regulating ferroptosis that targeted inhibition or degradation of GPX4 could effectively trigger ferroptosis. In this study, a series of ML162-quinone conjugates were constructed by using pharmacophore hybridization and bioisosterism strategies, with the aim of obtaining more active anticancer agents via the ferroptosis and apoptosis dual cell death processes. Of these compounds, GIC-20 was identified as the most active one that exhibited promising anticancer activity both in vitro and in vivo via ferroptosis and apoptosis dual-targeting processes, without obvious toxicity compared with ML162. On one hand, GIC-20 could trigger ferroptosis in cells by inducing intracellular lipid peroxide and ROS accumulation, and destroying mitochondrial structure. In addition to GPX4 inhibition, GIC-20 can also trigger ferroptosis via proteasomal-mediated degradation of GPX4, suggesting GIC-20 may function as a molecule glue degrader. On the other hand, GIC-20 can also induce apoptosis via upregulating the level of apoptotic protein Bax and downregulating the level of anti-apoptotic protein Bcl-2 in HT1080 cells. Furthermore, GIC-20 also enhanced the sensitivity of resistant MIA-PaCa-2-AMG510R cells to AMG510, suggesting the great potential of GIC-20 in overcoming the acquired resistance of KRASG12C inhibitors. Overall, GIC-20 represents a novel dual ferroptosis/apoptosis inducer warranting further development for cancer therapeutics and overcoming drug resistance.

Synthesis and evaluation of WK-X-34 derivatives as P-glycoprotein (P-gp/ABCB1) inhibitors for reversing multidrug resistance.

The emergence of multidrug resistance (MDR) in malignant tumors is one of the leading threats encountered currently by many chemotherapeutic agents. A proposed strategy to overcome MDR is to disable the efflux function of P-glycoprotein (P-gp/ABCB1), a critical member of the ABC transporter family that significantly increases the efflux of various anticancer drugs from tumor cells. In this study, structural modification of a third-generation P-gp inhibitor WK-X-34 based on bioisosteric and fragment-growing strategies led to the discovery of the adamantane derivative PID-9, which exhibited the best MDR reversal activity (IC50 = 0.1338 µM, RF = 78.6) in this series, exceeding those of the reported P-gp inhibitors verapamil and WK-X-34. In addition, compared with WK-X-34, PID-9 showed decreased toxicity to cells. Furthermore, the mechanism studies revealed that the reversal activity of adamantane derivatives PID-5, PID-7, and PID-9 stemmed from the inhibition of P-gp efflux. These results indicated that compound PID-9 is the most effective P-gp inhibitor among them with low toxicity and high MDR reversal activity, which provided a fundamental structural reference for further discovery of novel, effective, and non-toxic P-gp inhibitors.

Development of novel ferulic acid derivatives as potent histone deacetylase inhibitors.

Histone deacetylase inhibitors (HDACIs) offer a promising strategy for cancer therapy. The discovery of potent ferulic acid-based HDACIs with hydroxamic acid or 2-aminobenzamide group as zinc binding group was reported. The halogeno-acetanilide was introduced as novel surface recognition moiety (SRM). The majority of title compounds displayed potent HDAC inhibitory activity. In particular, FA6 and FA16 exhibited significant enzymatic inhibitory activities, with IC50 values of 3.94 and 2.82 µM, respectively. Furthermore, these compounds showed moderate antiproliferative activity against a panel of human cancer cells. FA17 displayed promising profile as an antitumor candidate. The results indicated that these ferulic acid derivatives could serve as promising lead compounds for further optimization.

Strategies to overcome cancer multidrug resistance (MDR) through targeting P-glycoprotein (ABCB1): An updated review.

The emergence of multidrug resistance (MDR) in malignant tumors is one of the leading threats encountered currently in many chemotherapeutic agents. The overexpression of the ATP-binding cassette (ABC) transporters is involved in MDR. P-glycoprotein (P-gp)/ABCB1 is a member of the ABC transporter family that significantly increases the efflux of various anticancer drugs from tumor cells. Therefore, targeting P-gp with small molecule inhibitors is an effective therapeutic strategy to overcome MDR. Over the past four decades, diverse compounds with P-gp inhibitory activity have been identified to sensitize drug-resistant cells, but none of them has been proven clinically useful to date. Research efforts continue to discover an effective approach for circumventing MDR. This review has provided an overview of the most recent advances (last three years) in various strategies for circumventing MDR mediated by P-gp. It may be helpful for the scientists working in the field of drug discovery to further synthesize and discover new chemical entities/therapeutic modalities with less toxicity and more efficacies to overcome MDR in cancer chemotherapy.

A benzochalcone derivative synchronously induces apoptosis and ferroptosis in pancreatic cancer cells.

Background: Pancreatic cancer is a highly aggressive and lethal disease with limited treatment options. In this study, we investigated the potential therapeutic effects of compound KL-6 on pancreatic cancer cells. Methods: The study involved assessing the inhibitory effects of KL-6 on cell proliferation, clonogenic potential, cell cycle progression, apoptosis, migration, and invasion. Additionally, we examined the action mechanism of KL-6 by RNA-seq and bioinformatic analysis and validated by qRT-PCR and western blot in pancreatic cancer cells. Results: Our results demonstrated that KL-6 effectively inhibited the growth of pancreatic cancer cells in a dose-dependent manner. It induced G2/M phase cell cycle arrest and apoptosis, disrupting the cell cycle progression and promoting cell death. KL-6 also exhibited inhibitory effects on cell migration and invasion, suggesting its potential to suppress the metastatic properties of pancreatic cancer cells. Furthermore, KL-6 modulated the expression of genes involved in various cancer-related pathways including apoptosis and ferroptosis. Conclusion: These findings collectively support the potential of KL-6 as a promising therapeutic option for pancreatic cancer treatment. Further research is needed to fully understand the underlying mechanisms and evaluate the clinical efficacy of KL-6 in pancreatic cancer patients.