MiR-383 sensitizes osteosarcoma cells to bortezomib treatment via down-regulating PSMB5

BACKGROUND

Proteasome inhibition is a promising strategy for cancer therapy. Bortezomib, which primarily targets the chymotrypsin-like activity of PSMB5, has demonstrated efficacy in various tumors. However, there is variable sensitivity to bortezomib, which could be attributed, in part, to variations in the expression of proteasome subunits.

METHODS AND RESULTS

In this study, we investigated whether miR-383 affects the expression of proteasome subunits in osteosarcoma (OS) cells, and if so, whether OS cells display differential sensitivity to bortezomib concerning miR-383 expression. We detected a decreased miR-383 expression in OS cells and tissues. Then we found a negative correlation between the cytotoxicity of bortezomib and the expression level of the proteasome 20S core particle subunit β5 (PSMB5). Intriguingly, we identified PSMB5 as a direct target of miR-383. Increased expression of miR-383 resulted in decreased PSMB5 expression and increased sensitivity to bortezomib in OS cells.

CONCLUSIONS

In summary, our findings present the initial comprehensive analysis of the function of miR-383 in OS. The outcomes indicate that miR-383 may augment the anticancer effect of bortezomib through PSMB5 repression, offering a novel therapeutic approach in OS and a fresh pathway for proteasome regulation.

Harnessing the power of gold: advancements in anticancer gold complexes and their functionalized nanoparticles

Cancer poses a formidable challenge, necessitating improved treatment strategies. Metal-based drugs and nanotechnology offer new hope in this battle. Versatile gold complexes and functionalized gold nanoparticles exhibit unique properties like biologically inert behaviour, outstanding light absorption, and heat-conversion abilities. These nanoparticles can be finely tuned for drug delivery, enabling precise and targeted cancer therapy. Their exceptional drug-loading capacity and low toxicity, stemming from excellent stability, biocompatibility, and customizable shapes, make them a promising option for enhancing cancer treatment outcomes and improving diagnostic imaging. Leveraging these attributes, researchers can design more effective and targeted cancer therapeutics. The potential of functionalized gold nanoparticles to advance cancer treatment and diagnostics holds a promising avenue for further exploration and development in the fight against cancer. This review article delves into the finely tuned attributes of functionalized gold nanoparticles, unveiling their potential for application in drug delivery for precise and targeted cancer therapy.

Drugs targeting the particle for arrangement of quaternary structure (PAQosome) and protein complex assembly

INTRODUCTION

The PAQosome is a 12-subunit complex that acts as a co-factor of the molecular chaperones HSP90 and HSP70. This co-chaperone has been shown to participate in assembly and maturation of several protein complexes, including nuclear RNA polymerases, RNA processing factors, the ribosome, PIKKs, and others. Subunits of the PAQosome, adaptors, and clients have been reported to be involved in various diseases, making them interesting targets for drug discovery.

AREA COVERED

In this review, the authors cover the detailed mechanisms of PAQosome and chaperone function. Specifically, the authors summarize the status of the PAQosome and some related chaperones and co-chaperones as candidate targets for drug discovery. Indeed, a number of compounds are currently being tested for the development of treatments against diseases, such as cancers and neurodegenerative conditions.

EXPERT OPINION

Searching for new drugs targeting the PAQosome requires a better understanding of PAQosome subunit interactions and the discovery of new interaction partners. Thus, PAQosome subunit crystallization is an important experiment to initiate virtual screening against new target and the development of in silico tools such as AlphaFold-multimer could accelerate the search for new interaction partner and determine more rapidly the interaction pocket needed for virtual drug screening.

Next Generation Gold Drugs and Probes: Chemistry and Biomedical Applications

The gold drugs, gold sodium thiomalate (Myocrisin), aurothioglucose (Solganal), and the orally administered auranofin (Ridaura), are utilized in modern medicine for the treatment of inflammatory arthritis including rheumatoid and juvenile arthritis; however, new gold agents have been slow to enter the clinic. Repurposing of auranofin in different disease indications such as cancer, parasitic, and microbial infections in the clinic has provided impetus for the development of new gold complexes for biomedical applications based on unique mechanistic insights differentiated from auranofin. Various chemical methods for the preparation of physiologically stable gold complexes and associated mechanisms have been explored in biomedicine such as therapeutics or chemical probes. In this Review, we discuss the chemistry of next generation gold drugs, which encompasses oxidation states, geometry, ligands, coordination, and organometallic compounds for infectious diseases, cancer, inflammation, and as tools for chemical biology via gold-protein interactions. We will focus on the development of gold agents in biomedicine within the past decade. The Review provides readers with an accessible overview of the utility, development, and mechanism of action of gold-based small molecules to establish context and basis for the thriving resurgence of gold in medicine.

Recent advances in the pharmacological targeting of ubiquitin-regulating enzymes in cancer

As a post-translational modification that has pivotal roles in protein degradation, ubiquitination ensures that intracellular proteins act in a precise spatial and temporal manner to regulate diversified cellular processes. Perturbation of the ubiquitin system contributes directly to the onset and progression of a wide variety of diseases, including various subtypes of cancer. This highly regulated system has been for years an active research area for drug discovery that is exemplified by several approved drugs. In this review, we will provide an update of the main breakthrough scientific discoveries that have been leading the clinical development of ubiquitin-targeting therapies in the last decade, with a special focus on E1 and E3 modulators. We will further discuss the unique challenges of identifying new potential therapeutic targets within this ubiquitous and highly complex machinery, based on available crystallographic structures, and explore chemical approaches by which these challenges might be met.

MiR-182-5p inhibits the tumorigenesis of clear cell renal cell carcinoma by repressing UBE2T

Ubiquitin-conjugating enzyme E2T (UBE2T), a member of the E2 family, has been reported to be overexpressed in certain tumor types and to have an important role in the Fanconi anemia pathway. However, the role of UBE2T in clear cell renal cell carcinoma (ccRCC) has not been clarified. MicroRNAs (miRNAs) participate in tumorigenesis by binding to genes and proteins that regulate cell proliferation or cell apoptosis. The aim of this study was to determine the role of UBE2T and the relationship between miR-182-5p and UBE2T in ccRCC. In the present study, UBE2T expression levels in ccRCC tissues and cells were assessed using real-time quantitative PCR (RT-qPCR) and western blotting. UBE2T protein expression was assessed in a total of 93 ccRCC patients from Peking University First Hospital (PKU) via immunohistochemistry (IHC). The effects of UBE2T knockdown on ccRCC cells were assessed with MTS assays, wound healing assays, Transwell invasion assays and flow cytometry. The effects of in vivo treatment were evaluated through xenograft experiments. The relationship between miR-182-5p and UBE2T was verified with a dual-luciferase reporter gene assay. We found that UBE2T was highly expressed in ccRCC cells and tissues. High UBE2T expression was positively correlated with advanced pathological stage, histological grade, maximum tumor diameter and distant metastasis. Multivariate analysis revealed that UBE2T expression was an independent risk factor for overall survival (OS) and recurrence-free survival (RFS) in patients with ccRCC. Knockdown of UBE2T significantly suppressed RCC cell proliferation, migration and invasion. Flow cytometry analysis showed that UBE2T knockdown promoted RCC cell cycle arrest at G2/M phase and increased cell apoptosis. The xenograft model confirmed that suppression of UBE2T significantly delayed tumor formation and growth in vivo. In addition, miR-182-5p inhibited UBE2T protein expression by targeting UBE2T mRNA and then inhibited the proliferation, migration and invasion of ccRCC cell. Our research reveals that UBE2T likely plays a critical role in ccRCC progression and may be a potential therapeutic target for ccRCC.

Ubiquitin-associated protein 2 like (UBAP2L) enhances growth and metastasis of gastric cancer cells

Ubiquitin-proteasome pathway has emerged as therapeutic targets for cancer. GEPIA database analysis showed that the expression of ubiquitin-associated protein 2 like (UBAP2L) in gastric cancer specimens was significantly higher than that in non-tumor tissue, and its high expression is associated with poor survival of gastric cancer patients. This study aims to investigate the role of UBAP2L in gastric cancer. Real-time PCR and western blot results showed that UBAP2L expression was upregulated in gastric cancer cell lines. Loss- and gain-of-function experiments demonstrated that silencing of UBAP2L inhibited proliferation, migration and invasion, and induced apoptosis of gastric cancer cells, and overexpression of UBAP2L played opposite roles. Nude mice inoculated with UBAP2L-silenced gastric cancer cells generated smaller xenografted tumors in vivo. Furthermore, UBAP2L activated Wnt/β-catenin signaling - the accumulation of nuclear β-catenin and the expression of its downstream targets (cyclin D1, AXIN-2 and c-MYC) was facilitated, whereas knockdown of UBAP2L deactivated this signaling. The tumor-suppressing effect of UBAP2L silencing was abolished by forced activation of β-cateninS33A. UBAP2L has been confirmed as a novel and direct target of miR-148b-3p. The anti-tumor effect of miR-148b-3p was partly reversed by UBAP2L overexpression. The expression of miR-148b-3p was negatively correlated with that of UBAP2L in gastric cancer samples. Overall, our study indicates that UBAP2L is required to maintain malignant behavior of gastric cancer cells, which involves the activation of Wnt/β-catenin signaling pathway. We propose UBAP2L as a potential therapeutic target against gastric cancer.

Synthesis of New Thiourea-Metal Complexes with Promising Anticancer Properties

In this work, two thiourea ligands bearing a phosphine group in one arm and in the other a phenyl group (T2) or 3,5-di-CF₃ substituted phenyl ring (T1) have been prepared and their coordination to Au and Ag has been studied. A different behavior is observed for gold complexes, a linear geometry with coordination only to the phosphorus atom or an equilibrium between the linear and three-coordinated species is present, whereas for silver complexes the coordination of the ligand as P^S chelate is found. The thiourea ligands and their complexes were explored against different cancer cell lines (HeLa, A549, and Jurkat). The thiourea ligands do not exhibit relevant cytotoxicity in the tested cell lines and the coordination of a metal triggers excellent cytotoxic values in all cases. In general, data showed that gold complexes are more cytotoxic than the silver compounds with T1, in particular the complexes [AuT1(PPh₃)]OTf, the bis(thiourea) [Au(T1)₂]OTf and the gold-thiolate species [Au(SR)T1]. In contrast, with T2 better results are obtained with silver species [AgT1(PPh₃)]OTf and the [Ag(T1)₂]OTf. The role played by the ancillary ligand bound to the metal is important since it strongly affects the cytotoxic activity, being the bis(thiourea) complex the most active species. This study demonstrates that metal complexes derived from thiourea can be biologically active and these compounds are promising leads for further development as potential anticancer agents.

Prognostic Role of the Ubiquitin Proteasome System in Clear Cell Renal Cell Carcinoma: A Bioinformatic Perspective

Background: Clear cell renal cell carcinoma (ccRCC) is a common malignant tumor of the urinary system. The ubiquitin proteasome system (UPS) plays an important role in the generation, metabolism and survival of tumor. We are aimed to make a comprehensive exploration of the UPS's role in ccRCC with bioinformatic tools, which may contribute to the understanding of UPS in ccRCC, and give insight for further research. Methods: The UPS-related genes (UPSs) were collected by an integrative approach. The expression and clinical data were downloaded from TCGA database. R soft was used to perform the differentially expressed UPSs analysis, functional enrichment analysis. We also estimated prognostic value of each UPS with the help of GEPIA database. Two predicting models were constructed with the differentially expressed UPSs and prognosis-related genes, respectively. The correlations of risk score with clinical characteristics were also evaluated. Data of GSE29609 cohort were obtained from GEO database to validate the prognostic models. Results: We finally identified 91 differentially expressed UPSs, 48 prognosis related genes among them, and constructed a prognostic model with 18 UPSs successfully, the AUC was 0.760. With the help of GEPIA, we found 391 prognosis-related UPSs, accounting for 57.84% of all UPSs. Another prognostic model was constructed with 28 prognosis-related genes of them, and with a better AUC of 0.825. Additionally, our models can also stratify patients into high and low risk groups accurately in GSE29609 cohort. Similar prognostic values of our models were observed in the validated GSE29609 cohort. Conclusions: UPS is dysregulated in ccRCC. UPS related genes have significant prognostic value in ccRCC. Models constructed with UPSs are effective and applicable. An abnormal ubiquitin proteasome system should play an important role in ccRCC and be worthy of further study.

Drug Development Targeting the Ubiquitin-Proteasome System (UPS) for the Treatment of Human Cancers

Cancer cells are characterized by a higher rate of protein turnover and greater demand for protein homeostasis compared to normal cells. In this scenario, the ubiquitin-proteasome system (UPS), which is responsible for the degradation of over 80% of cellular proteins within mammalian cells, becomes vital to cancer cells, making the UPS a critical target for the discovery of novel cancer therapeutics. This review systematically categorizes all current reported small molecule inhibitors of the various essential components of the UPS, including ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), ubiquitin ligases (E3s), the 20S proteasome catalytic core particle (20S CP) and the 19S proteasome regulatory particles (19S RP), as well as their mechanism/s of action and limitations. We also discuss the immunoproteasome which is considered as a prospective therapeutic target of the next generation of proteasome inhibitors in cancer therapies.

Inhibitory effects of bortezomib in a subcutaneous tumor model of H22 mouse hepatocarcinoma cells

OBJECTIVE

To evaluate the inhibition effects and mechanism of bortezomib in a subcutaneous H22 mouse hepatocarcinoma model.

METHODS

A subcutaneous xenograft model was constructed by subcutaneous injection of H22 cells in mice. The xenograft mice was randomly divided into bortezomib and control groups (n = 8 each). The bortezomib group was injected with 0.5 mg/kg bortezomib in saline via tail vein once every four days for a total of 4 times. The control group was intravenously given an equal volume of saline. The tumor size was measured every four days. At day 19, subcutaneous xenografts were obtained and the expression of apoptosis-related proteins in tumor was detected by immunochemical staining.

RESULTS

The tumor volume of H22 xenografts in bortezomib group was significantly smaller than that in control group on day 19 (p =  0.004). The tumor volume/mouse weight ratio in bortezomib group was significantly lower compared with control group on day 13, 16 and 19 (all p <  0.05). The bortezomib group exhibited significantly higher expression of pro-apoptotic protein TNF-α (p =  0.032), and lower expression of anti-apoptotic protein XIAP, Stat3, and Survivin (p =  0.024, 0.016, and 0.039, respectively).

CONCLUSION

Bortezomib effectively inhibited the growth of H22 xenografts without affecting the mouse weight. The anti-tumor effects of bortezomib is associated with its stimulation on tumor cell apoptosis.

Cytotoxic Gold(I) Complexes with Amidophosphine Ligands Containing Thiophene Moieties

A new phosphine ligand bearing a thiophene moiety, C4H3SNHCOCH2CH2PPh2 (L), has been prepared by reaction of the aminophosphine Ph2PCH2CH2NH2 with thiophenecarbonylchloride in the presence of triethylamine. The coordination behavior towards gold(I), gold(III) and silver(I) species has been studied and several metal compounds of different stoichiometry have been achieved, such as [AuL2]OTf, [AuXL] (X = Cl, C6F5), [Au(C6F5)3L], [AgL2]OTf or [Ag(OTf)L]. Additionally, the reactivity of the chloride gold(I) species with biologically relevant thiolates was explored, thus obtaining the neutral thiolate compounds [AuL(SR)] (SR = 2-thiocitosine, 2-thiolpyridine, 2-thiouracil, 2-thionicotinic acid, 2,3,4,6-tetra-6-acetyl-1-thiol-β-d-glucopyranosato or thiopurine). The antitumor activity of the compounds was measured by the MTT method in several cancer cells and the complexes exhibit excellent cytotoxic activity.

Anticancer properties of gold complexes with biologically relevant ligands

The present review highlights our findings in the field of antitumor gold complexes bearing biologically relevant molecules, such as DNA-bases, amino acids or peptide derivatives. The results show that very active complexes are achieved with this sort of ligands in several cancer cells. In these compounds the gold center is bonded to these biological molecules mainly through a sulfur atom belonging to a cysteine moiety or to a thionicotinic moiety as result of the functionalization of the biological compounds, and additionally phosphines or N-heterocyclic carbenes are present as ancillary ligands. These robust compounds are stable in the biological media and can be transported to their targets without previous deactivation. The presence of these scaffolds represents a good approach to obtain complexes with improved biologically activity, better transport and biodistribution to cancer cells. Thioredoxin reductase (TrxR) has been shown as the main target for these complexes and in some cases, DNA interactions has been also observed.

Targeting the ubiquitin-proteasome system for cancer treatment: discovering novel inhibitors from nature and drug repurposing

In the past 15 years, the proteasome has been validated as an anti-cancer drug target and 20S proteasome inhibitors (such as bortezomib and carfilzomib) have been approved by the FDA for the treatment of multiple myeloma and some other liquid tumors. However, there are shortcomings of clinical proteasome inhibitors, including severe toxicity, drug resistance, and no effect in solid tumors. At the same time, extensive research has been conducted in the areas of natural compounds and old drug repositioning towards the goal of discovering effective, economical, low toxicity proteasome-inhibitory anti-cancer drugs. A variety of dietary polyphenols, medicinal molecules, metallic complexes, and metal-binding compounds have been found to be able to selectively inhibit tumor cellular proteasomes and induce apoptotic cell death in vitro and in vivo, supporting the clinical success of specific 20S proteasome inhibitors bortezomib and carfilzomib. Therefore, the discovery of natural proteasome inhibitors and researching old drugs with proteasome-inhibitory properties may provide an alternative strategy for improving the current status of cancer treatment and even prevention.

New comprehensive studies of a gold(III) Dithiocarbamate complex with proven anticancer properties: Aqueous dissolution with cyclodextrins, pharmacokinetics and upstream inhibition of the ubiquitin-proteasome pathway

The gold(III)-dithiocarbamate complex AuL12 (dibromo [ethyl-N-(dithiocarboxy-kS,kS')-N-methylglycinate] gold(III)), is endowed with promising in vitro/in vivo antitumor activity and toxicological profile. Here, we report our recent strategies to improve its water solubility and stability under physiological conditions along with our efforts for unravelling its tangled mechanism of action. We used three types of α-cyclodextrins (CDs), namely β-CD, Me-β-CD and HP-β-CD to prepare aqueous solutions of AuL12. The ability of these natural oligosaccharide carriers to enhance water solubility of hydrophobic compounds, allowed drug stability of AuL12 to be investigated. Moreover, pharmacokinetic experiments were first carried out for a gold(III) coordination compound, after i.v. injection of the nanoformulation AuL12/HP-β-CD to female mice. The gold content in the blood samples was detected at scheduled times by AAS (atomic absorption spectrometry) analysis, highlighting a fast biodistribution with a t_β1/2 of few minutes and a slow escretion (t_α1/2 of 14.3 h). The in vitro cytotoxic activity of AuL12 was compared with the AuL12/HP-β-CD mixture against a panel of three human tumor cell lines (i.e., HeLa, KB and MCF7). Concerning the mechanism of action, we previously reported the proteasome-inhibitory activity of some our gold(III)-based compounds. In this work, we moved from the proteasome target to upstream of the important ubiquitin-proteasome pathway, testing the effects of AuL12 on the polyubiquitination reactions involving the Ub-activating (E1) and -conjugating (E2) enzymes.

The effects of phosphanegold(I) thiolates on the biological properties of Acanthamoeba castellanii belonging to the T4 genotype

BACKGROUND

Gold compounds have shown promise in the treatment of non-communicable diseases such as rheumatoid arthritis and cancer, and are considered of value as anti-microbial agents against Gram-negative and Gram-positive bacteria, and have anti-parasitic properties against Schistosoma mansoni, Trypanosoma brucei, Plasmodium falciparum, Leishmania infantinum, Giardia lamblia, and Entamoeba histolytica. They are known to affect enzymatic activities that are required for the cellular respiration processes.

METHODS

Anti-amoebic effects of phosphanegold(I) thiolates were tested against clinical isolate of A. castellanii belonging to the T4 genotype by employing viability assays, growth inhibition assays, encystation assays, excystation assays, and zymographic assays.

RESULTS

The treatment of A. castellanii with the phosphanegold(I) thiolates tested (i) had no effect on the viability of A. castellanii as determined by Trypan blue exclusion test, (ii) did not affect amoebae growth using PYG growth medium, (iii) did not inhibit cellular differentiation, and (iv) had no effect on the extracellular proteolytic activities of A. castellanii.

CONCLUSION

Being free-living amoeba, A. castellanii is a versatile respirator and possesses respiratory mechanisms that adapt to various aerobic and anaerobic environments to avoid toxic threats and adverse conditions. For the first time, our findings showed that A. castellanii exhibits resistance to the toxic effects of gold compounds and could prove to be an attractive model to study mechanisms of metal resistance in eukaryotic cells.

Integrative analysis of multi-omics data reveals distinct impacts of DDB1-CUL4 associated factors in human lung adenocarcinomas

Many DDB1-CUL4 associated factors (DCAFs) have been identified and serve as substrate receptors. Although the oncogenic role of CUL4A has been well established, specific DCAFs involved in cancer development remain largely unknown. Here we infer the potential impact of 19 well-defined DCAFs in human lung adenocarcinomas (LuADCs) using integrative omics analyses, and discover that mRNA levels of DTL, DCAF4, 12 and 13 are consistently elevated whereas VBRBP is reduced in LuADCs compared to normal lung tissues. The transcriptional levels of DCAFs are significantly correlated with their gene copy number variations. SKIP2, DTL, DCAF6, 7, 8, 13 and 17 are frequently gained whereas VPRBP, PHIP, DCAF10, 12 and 15 are frequently lost. We find that only transcriptional level of DTL is robustly, significantly and negatively correlated with overall survival across independent datasets. Moreover, DTL-correlated genes are enriched in cell cycle and DNA repair pathways. We also identified that the levels of 25 proteins were significantly associated with DTL overexpression in LuADCs, which include significant decreases in protein level of the tumor supressor genes such as PDCD4, NKX2-1 and PRKAA1. Our results suggest that different CUL4-DCAF axis plays the distinct roles in LuADC development with possible relevance for therapeutic target development.

Bortezomib induces apoptosis and suppresses cell growth and metastasis by inactivation of Stat3 signaling in chondrosarcoma

Bortezomib, formerly known as PS341, is a novel proteasome inhibitor with in vitro and in vivo antineoplastic effects in many malignancies. However, diverse antitumor mechanisms of bortezomib have been identified in many investigations and preclinical studies. Understanding the molecular and cellular mechanisms through which bortezomib acts will improve the therapeutic utility of this drug in different cancer types. In the present study, we investigated the in vitro and in vivo effects of bortezomib on chondrosarcoma. Bortezomib selectively inhibited cell growth in chondrosarcoma cells but not in normal articular cartilage cells. In addition to growth inhibition, apoptosis and cell cycle arrest, bortezomib triggered alleviation of migratory and invasive properties of chondrosarcoma cells. Mechanistically, signal transducer and activator of transcription 3 (Stat3) and its downstream targets Bcl-2, cyclin D1 and c-Myc was inactivated by bortezomib treatment. Accordingly, small interfering RNA (siRNA)-mediated Stat3 knockdown enhanced bortezomib-induced apoptosis, and concomitantly enhanced the inhibitory effect of bortezomib on cell viability, migration and invasion. Moreover, while Slug, MMP9, MMP2, CD44, N-cadherin and vimentin, the mesenchymal cell markers, were repressed by bortezomib concomitant increased expression of E-cadherin was observed. In vivo, bortezomib downregulated Stat3 activity and mesenchymal cell marker expression, induced apoptosis and inhibition of metastasis and tumor growth. Together, inactivation of Stat3 signaling contributes to bortezomib-induced inhibition of tumor growth, migration and invation on chondrosarcoma. Bortezomib demonstrates an antineoplastic role on chondrosarcoma both in vitro and in vivo. These beneficial effects can be explained by bortezomib-mediated Stat3 supression. The present study suggests a promising therapeutics target in chondrosarcoma and probably in other kinds of metastatic malignant tumors.

Novel copper complexes as potential proteasome inhibitors for cancer treatment (Review)

The use of metal complexes in the pharmaceutical industry has recently increased and as a result, novel metal‑based complexes have initiated an interest as potential anticancer agents. Copper (Cu), which is an essential trace element in all living organisms, is important in maintaining the function of numerous proteins and enzymes. It has recently been demonstrated that Cu complexes may be used as tumor‑specific proteasome inhibitors and apoptosis inducers, by targeting the ubiquitin‑proteasome pathway (UPP). Cu complexes have demonstrated promising results in preclinical studies. The UPP is important in controlling the expression, activity and location of various proteins. Therefore, selective proteasome inhibition and apoptotic induction in cancer cells have been regarded as potential anticancer strategies. The present short review discusses recent progress in the development of Cu complexes, including clioquinol, dithiocarbamates and Schiff bases, as proteasome inhibitors for cancer treatment. A discussion of recent research regarding the understanding of metal inhibitors based on Cu and ligand platforms is presented.

Bioactive gold(i) complexes with 4-mercaptoproline derivatives

Unprecedented gold(i) bioconjugates bearing non-proteinogenic amino acid 4-mercaptoproline species as bioorganic ligands have been prepared. The complexes displayed excellent cytotoxic activity with IC₅₀ values in the low μM range and even in the nM range.

Broad targeting of resistance to apoptosis in cancer

Apoptosis or programmed cell death is natural way of removing aged cells from the body. Most of the anti-cancer therapies trigger apoptosis induction and related cell death networks to eliminate malignant cells. However, in cancer, de-regulated apoptotic signaling, particularly the activation of an anti-apoptotic systems, allows cancer cells to escape this program leading to uncontrolled proliferation resulting in tumor survival, therapeutic resistance and recurrence of cancer. This resistance is a complicated phenomenon that emanates from the interactions of various molecules and signaling pathways. In this comprehensive review we discuss the various factors contributing to apoptosis resistance in cancers. The key resistance targets that are discussed include (1) Bcl-2 and Mcl-1 proteins; (2) autophagy processes; (3) necrosis and necroptosis; (4) heat shock protein signaling; (5) the proteasome pathway; (6) epigenetic mechanisms; and (7) aberrant nuclear export signaling. The shortcomings of current therapeutic modalities are highlighted and a broad spectrum strategy using approaches including (a) gossypol; (b) epigallocatechin-3-gallate; (c) UMI-77 (d) triptolide and (e) selinexor that can be used to overcome cell death resistance is presented. This review provides a roadmap for the design of successful anti-cancer strategies that overcome resistance to apoptosis for better therapeutic outcome in patients with cancer.

Heterometallic titanium-gold complexes inhibit renal cancer cells in vitro and in vivo

Heterometallic compounds as anticancer agents demonstrating in vivo potential for the first time. Titanocene–gold derivatives: promising candidates for renal cancer.

Following recent work on heterometallic titanocene–gold complexes as potential chemotherapeutics for renal cancer, we report here on the synthesis, characterization and stability studies of new titanocene complexes containing a methyl group and a carboxylate ligand (mba = S–C₆H₄–COO^–) bound to gold(i)-phosphane fragments through a thiolate group [(η-C₅H₅)₂TiMe(μ-mba)Au(PR₃)]. The compounds are more stable in physiological media than those previously reported and are highly cytotoxic against human cancer renal cell lines. We describe here preliminary mechanistic data involving studies on the interaction of selected compounds with plasmid (pBR322) DNA used as a model nucleic acid, and with selected protein kinases from a panel of 35 protein kinases having oncological interest. Preliminary mechanistic studies in Caki-1 renal cells indicate that the cytotoxic and anti-migration effects of the most active compound 5 [(η-C₅H₅)₂TiMe(μ-mba)Au(PPh₃)] involve inhibition of thioredoxin reductase and loss of expression of protein kinases that drive cell migration (AKT, p90-RSK, and MAPKAPK3). The co-localization of both titanium and gold metals (1 : 1 ratio) in Caki-1 renal cells was demonstrated for 5 indicating the robustness of the heterometallic compound in vitro. Two compounds were selected for further in vivo studies on mice based on their selectivity in vitro against renal cancer cell lines when compared to non-tumorigenic human kidney cell lines (HEK-293T and RPTC) and the favourable preliminary toxicity profile in C57BL/6 mice. Evaluation of Caki-1 xenografts in NOD.CB17-Prkdc SCID/J mice showed an impressive tumor reduction (67%) after treatment for 28 days (3 mg per kg per every other day) with heterometallic compound 5 as compared with the previously described [(η-C₅H₅)₂Ti{OC(O)-4-C₆H₄-P(Ph₂)AuCl}₂] 3 which was non-inhibitory. These findings indicate that structural modifications on the ligand scaffold affect the in vivo efficacy of this class of compounds.

CCK8 peptide-labeled Pluronic® F127 micelles as a targeted vehicle of gold-based anticancer chemotherapeutics

A sparingly water-soluble gold(iii) complex was encapsulated in micelles functionalized with the CCK8-targeting moiety for the selective delivery of an anticancer drug.

Organometallic Titanocene-Gold Compounds as Potential Chemotherapeutics in Renal Cancer. Study of their Protein Kinase Inhibitory Properties

Early-late transition metal TiAu2 compounds [(η-C5H5)2Ti{OC(O)CH2PPh2AuCl}2] (3) and new [(η-C5H5)2Ti{OC(O)-4-C6H4PPh2AuCl}2] (5) were evaluated as potential anticancer agents in vitro against renal and prostate cancer cell lines. The compounds were significantly more effective than monometallic titanocene dichloride and gold(I) [{HOC(O)RPPh2}AuCl] (R = -CH2- 6, -4-C6H4- 7) derivatives in renal cancer cell lines, indicating a synergistic effect of the resulting heterometallic species. The activity on renal cancer cell lines (for 5 in the nanomolar range) was considerably higher than that of cisplatin and highly active titanocene Y. Initial mechanistic studies in Caki-1 cells in vitro coupled with studies of their inhibitory properties on a panel of 35 kinases of oncological interest indicate that these compounds inhibit protein kinases of the AKT and MAPKAPK families with a higher selectivity toward MAPKAPK3 (IC503 = 91 nM, IC505 = 117 nM). The selectivity of the compounds in vitro against renal cancer cell lines when compared to a nontumorigenic human embryonic kidney cell line (HEK-293T) and the favorable preliminary toxicity profile on C57black6 mice indicate that these compounds (especially 5) are excellent candidates for further development as potential renal cancer chemotherapeutics.

Functional inhibition of aquaporin-3 with a gold-based compound induces blockage of cell proliferation

AQP3 has been correlated with higher transport of glycerol, increment of ATP content, and larger proliferation capacity. Recently, we described the gold(III) complex Auphen as a very selective and potent inhibitor of AQP3's glycerol permeability (Pgly ). Here we evaluated Auphen effect on the proliferation of various mammalian cell lines differing in AQP3 expression level: no expression (PC12), moderate (NIH/3T3) or high (A431) endogenous expression, cells stably expressing AQP3 (PC12-AQP3), and human HEK293T cells transiently transfected (HEK-AQP3) for AQP3 expression. Proliferation was evaluated in the absence or presence of Auphen (5 μM) by counting number of viable cells and analyzing 5-bromo-2'-deoxyuridine (BrdU) incorporation. Auphen reduced ≈50% the proliferation in A431 and PC12-AQP3, ≈15% in HEK-AQP3 and had no effect in PC12-wt and NIH/3T3. Strong arrest in the S-G2/M phases of the cell cycle, supported by analysis of cyclins (A, B1, D1, E) levels, was observed in AQP3-expressing cells treated with Auphen. Flow-cytometry of propidium iodide incorporation and measurements of mitochondrial dehydrogenases activity confirmed absence of cytotoxic effect of the drug. Functional studies evidenced ≈50% inhibition of A431 Pgly by Auphen, showing that the compound's antiproliferative effect correlates with its ability to inhibit AQP3 Pgly . Role of Cys-40 on AQP3 permeability blockage by Auphen was confirmed by analyzing the mutated protein (AQP3-Ser-40). Accordingly, cells transfected with mutated AQP3 gained resistance to the antiproliferative effect of Auphen. These results highlight an Auphen inhibitory effect on proliferation of cells expressing AQP3 and suggest a targeted therapeutic effect on carcinomas with large AQP3 expression.

Selected cytotoxic gold compounds cause significant inhibition of 20S proteasome catalytic activities

Six structurally diverse cytotoxic gold compounds are reported to cause profound and differential inhibition of the three main catalytic activities of purified 20S proteasome whilst auranofin, an established gold(I) drug in clinical use, is nearly ineffective. In particular, the gold(I) complex [(pbiH)Au(PPh3)]PF6, turns out to be the most potent inhibitor of all three enzyme activities with sub-micromolar IC50 values. The present results further support the view that proteasome inhibition may play a major--yet not exclusive--role in the cytotoxic actions of gold based anticancer agents.

Preclinical activity of multiple-target gold(III)-dithiocarbamato peptidomimetics in prostate cancer cells and xenografts

Background: Recently, novel gold(III)-dithiocarbamato peptidomimetics, designed to target peptide transporters upregulated in several tumor cells have shown promise as anticancer agents. Results: The biological behavior of the most promising derivatives AuD8 and AuD9 was studied in PC3 and DU145 prostate cancer cells. They exert higher cytotoxicity in vitro than the reference drug cisplatin and induce apoptosis, promoting mitochondrial membrane permeabilization and stimulating reactive oxygen species generation. Moreover, they inhibit both selenoenzyme thioredoxin reductase and proteasome activity. Additionally, AuD8 effectively reduces tumor growth in prostate tumor-bearing nude mice with minimal systemic toxicity. Conclusion: Altogether, our results provide insights into the anticancer activity of these gold(III)-dithiocarbamato peptidomimetics and support their potential as new agents for prostate cancer treatment.

Luminescent iminophosphorane gold, palladium and platinum complexes as potential anticancer agents

A series of coordination gold(III), palladium(II), and platinum(II) complexes with a luminescent iminophosphorane ligand derived from 8-aminoquinoline [Ph3P=N-C9H6N] (1), have been synthesized and structurally characterized. The coordination palladium(II) and platinum(II) compounds can evolve further, under appropriate conditions, to give stable cyclometalated endo species [M{κ3-C,N,N-C6H4(PPh2=N-8-C9H6N}Cl] (M = Pd, Pt) by C-H activation of the phenyl group of the PPh 3 fragment. Iminophosphorane 1 and the new metallic complexes are luminescent in DMSO or DMSO:H2O (1:1 mixture) solutions at RT. The compounds have been evaluated for their antiproliferative properties in a human ovarian cancer cell line (A2780S), in human lung cancer cells (A-549) and in a non-tumorigenic human embryonic kidney cell line (HEK-293T). Most compounds have been more toxic to the ovarian cancer cell line than to the non-tumorigenic cell line. The new complexes interact with human serum albumin (HSA) faster than cisplatin. Studies of the interactions of the compounds with DNA indicate that, in some cases, they exert anticancer effects in vitro based on different mechanisms of action with respect to cisplatin.

Gold(III)-dithiocarbamato peptidomimetics in the forefront of the targeted anticancer therapy: preclinical studies against human breast neoplasia

Since the serendipitous discovery of cisplatin, platinum-based drugs have become well-established antitumor agents, despite the fact that their clinical use is limited by many severe side-effects. In order to both improve the chemotherapeutic index and broaden the therapeutic spectrum of current drugs, our most recent anti-neoplastic agents, Au(III) complexes, were designed as carrier-mediated delivery systems exploiting peptide transporters, which are up-regulated in some cancers. Among all, we focused on two compounds and tested them on human MDA-MB-231 (resistant to cisplatin) breast cancer cell cultures and xenografts, discovering the proteasome as a major target both in vitro and in vivo. 53% inhibition of breast tumor growth in mice was observed after 27 days of treatment at 1.0 mg kg⁻¹ d⁻¹, compared to control. Remarkably, if only the most responsive mice are taken into account, 85% growth inhibition, with some animals showing tumor shrinkage, was observed after 13 days. These results led us to file an international patent, recognizing this class of gold(III) peptidomimetics as suitable candidates for entering phase I clinical trials.

Impact of EBV essential nuclear protein EBNA-3C on B-cell proliferation and apoptosis

For over 40 years, EBV infection has been implicated in the etiology of a variety of lymphoid malignancies with the exceptional ability to drive resting B cells to continuously proliferate by successfully overriding cellular apoptotic stimuli. EBV utilizes the normal physiology of B-cell differentiation to persist within the memory B-cell pool of the immunocompetent host and subsequently establishes a life-long latent infection. During latency, out of a subset of viral genes expressed, EBNA-3C is one of the essential antigens required for in vitro primary B-cell transformation. EBNA-3C acts as a transcriptional coregulator by interacting with various cellular and viral factors. For the last 10 years, we have been actively engaged in discerning the biological significance of these interactions and revealed that EBNA-3C primarily targets two important cellular pathways - cell cycle and apoptosis. This review aims to summarize our current knowledge on EBNA-3C-mediated functions and describe how EBNA-3C seizes these cellular pathways that eventually promote B-cell lymphomagenesis. A scrupulous understanding of the critical relationship between EBNA-3C and these cellular machineries will not only aid in elucidating EBV pathogenesis, but also largely facilitate the development of novel diagnostic, as well as therapeutic, strategies against a vast range of EBV-associated B-cell lymphomas.

Bortezomib induces apoptosis and autophagy in osteosarcoma cells through mitogen-activated protein kinase pathway in vitro

Objective

To investigate the effects of bortezomib on human osteosarcoma cells from the HOS cell line, and the underlying associated mechanisms.

Methods

Viability of HOS cells treated with bortezomib (5–20 nM) for different time periods was measured and changes in the cell cycle were assessed. Apoptosis and autophagy in HOS cells treated with bortezomib were analysed using annexin V-fluorescein isothiocyanate assay, transmission electron microscopy and Western blotting. Surges in mitogen-activated protein kinase (MAPK) pathways including MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK1/2), ERK1/2, c-Jun N-terminal kinase (JNK) and p38 MAPK were analysed using Western blotting.

Results

Bortezomib induced growth inhibition in a time- and dose-dependent manner, and autophagy and apoptosis in a dose-dependent manner, in HOS cells. HOS cell autophagy and apoptosis in response to bortezomib, corresponded with changing levels of intracellular MAPK signalling molecules.

Conclusions

This study provided new insights into the mechanisms underlying bortezomib-induced apoptosis in human osteosarcoma HOS cells, and suggests that bortezomib could be a potent chemotherapeutic agent in the treatment of osteosarcoma.

Potential anticancer heterometallic Fe-Au and Fe-Pd agents: initial mechanistic insights

A series of gold(III) and palladium(II) heterometallic complexes with new iminophosphorane ligands derived from ferrocenylphosphanes [{Cp-P(Ph2)═N-Ph}2Fe] (1), [{Cp-P(Ph2)═N-CH2-2-NC5H4}2Fe] (2), and [{Cp-P(Ph2)═N-CH2-2-NC5H4}Fe(Cp)] (3) have been synthesized and structurally characterized. Ligands 2 and 3 afford stable coordination complexes [AuCl2(3)]ClO4, [{AuCl2}2(2)](ClO4)2, [PdCl2(3)], and [{PdCl2}2(2)]. The complexes have been evaluated for their antiproliferative properties in human ovarian cancer cells sensitive and resistant to cisplatin (A2780S/R), in human breast cancer cells (MCF7) and in a nontumorigenic human embryonic kidney cell line (HEK-293T). The highly cytotoxic trimetallic derivatives M2Fe (M = Au, Pd) are more cytotoxic to cancer cells than their corresponding monometallic fragments. Moreover, these complexes were significantly more cytotoxic than cisplatin in the resistant A2780R and the MCF7 cell lines. Studies of the interactions of the trimetallic compounds with DNA and the zinc-finger protein PARP-1 indicate that they exert anticancer effects in vitro based on different mechanisms of actions with respect to cisplatin.

Aquaporin inhibition by gold(III) compounds: new insights

Aquaporins (AQPs) are membrane water/glycerol channels with essential roles in biological systems, as well as being promising targets for therapy and imaging. Using a stopped-flow method, a series of gold(III), platinum(II) and copper(II) complexes bearing nitrogen donor ligands, such as 1,10-phenatroline, 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-diamino-2,2'-bipyridine and 2,2';6',2"-terpyridine, were evaluated in human red blood cells expressing AQP1 and AQP3, responsible for water and glycerol movement, respectively. The results showed that the gold(III) complexes selectively modulate AQP3 over AQP1. Molecular modeling and density functional theory (DFT) calculations were subsequently performed to rationalize the observations and to investigate the possible molecular mechanism through which these gold compounds act on their putative target (AQP3). In the absence of any crystallographic data, a previously reported homology model was used for this purpose. Combined, the findings of this study show that potent and selective modulation of these solute channels is possible, however further investigation is required into the selectivity of this class of agents against all AQP isoforms and their potential therapeutic uses.

DNA damage emergency: cellular garbage disposal to the rescue?

The proteasome is a cellular machine found in the cytosol, nucleus and on chromatin that performs much of the proteolysis in eukaryotic cells. Recent reports show it is enriched at sites of double-stranded DNA breaks (DSBs) in mammalian cells. What is it doing there? This review will address three possibilities suggested by recent reports: in degrading proteins after their ubiquitination at and eviction from chromatin; as a deubiquitinase, specific to the antagonism of ubiquitin conjugates generated as part of the signalling of a DSB; and as a functional component of DNA repair mechanism itself. These findings add complexity to the proteasome as a potential therapeutic target in cancer treatment.

p70S6 kinase is a target of the novel proteasome inhibitor 3,3'-diamino-4'-methoxyflavone during apoptosis in human myeloid tumor cells

Acute myeloid leukemia (AML) is a deadly disease characterized by the clonal expansion and accumulation of hematopoietic stem cells arrested at various stages of development. Clinical research efforts are currently focusing on targeted therapies that induce apoptosis in AML cells. Herein, the effects and mechanisms of the novel flavone 3,3'-diamino-4'-methoxyflavone (DD1) on AML cell dysfunction were investigated in AML cells (monoblast U937, myelomonocyte OCI-AML3, promyelocyte NB4, myeloblast HL-60) and blood samples from patients with AML. The administration of DD1 inhibited proliferation and induced death of AML cell lines and reduced the clonogenic activity of AML, but not normal, blood cells. The flavone's apoptotic action in U937 cells was associated with recruitment of mitochondria, Bax activation, Bad dephosphorylation (at Ser(136)), activation of caspases -8, -9, and -3 and cleavage of the caspase substrate PARP-1. DD1 induced a marked decrease in (i) Thr(389)-phosphorylation and (ii) protein levels of the caspase-3 substrate P70 ribosomal S6 kinase (P70S6K, known for its ability to phosphorylate Bad). Caspase-dependent apoptosis and P70S6K degradation were simultaneously prevented by the caspase inhibitors. Importantly, DD1 was shown to directly inhibit the proteasome's chymotrypsin-like activity in U937 cells. Apoptotic activity of the proteasome inhibitor bortezomib was also related to Bax activation and P70S6K downregulation. Accordingly, DD1 failed to induce P70S6K cleavage, Bax stimulation and apoptosis in K562 cells resistant to bortezomib. These results indicate that DD1 has the potential to eradicate AML cells and support a critical role for Bax and P70S6K in DD1-mediated proteasome inhibition and apoptosis of leukemia cells.

A gold(III) porphyrin complex as an anti-cancer candidate to inhibit growth of cancer-stem cells

A cytotoxic gold(III) complex of meso-tetraphenylporphyrin ([Au(TPP)]Cl, denoted gold-1a) blocks the self-renewal ability of cancer stem-like cells and shows appealing safety pharmacological profiles in rodents.

Interview: Interview with Future Medicinal Chemistry’s US Senior Editor, Iwao Ojima

Professor Iwao Ojima studied at the University of Tokyo (Japan) before being appointed as a Senior Research Fellow and Group Leader at the Sagami Institute of Chemical Research. He is now Director of the Institute of Chemical Biology and Drug Discovery at State University of New York (USA) and has been a visiting professor in European, North American and Asian academic institutions. Professor Ojima agreed to serve as the US Senior Editor of Future Medicinal Chemistry when it launched in 2009 and continues to provide his expertise to the journal. Professor Ojima spoke to Future Medicinal Chemistry about why medicinal chemistry is such an exciting field to work in, the state of the pharmaceutical industry, and what features and issues make this journal unique.

Interview conducted by Isaac Bruce, Commissioning Editor.