Cathepsin B as a cancer target

Novel selective proline-based peptidomimetics for human cathepsin K inhibition

Human cathepsin K (CatK) stands out as a promising target for the treatment of osteoporosis, considering its role in degrading the bone matrix. Given the small and shallow S2 subsite of CatK and considering its preference for proline or hydroxyproline, we now propose the rigidification of the leucine fragment found at the P2 position in a dipeptidyl-based inhibitor, generating rigid proline-based analogs. Accordingly, with these new proline-based peptidomimetics inhibitors, we selectively inhibited CatK against other human cathepsins (B, L and S). Among these new ligands, the most active one exhibited a high affinity (pKi = 7.3 - 50.1 nM) for CatK and no inhibition over the other cathepsins. This specific inhibitor harbors two novel substituents never employed in other CatK inhibitors: the trifluoromethylpyrazole and the 4-methylproline at P3 and P2 positions. These results broaden and advance the path toward new potent and selective inhibitors for CatK.

Novel thiazolotriazole and triazolothiadiazine scaffolds as selective tumor associated carbonic anhydrase inhibitors endowed with cathepsin B inhibition

The present research focused on the tail-approach synthesis of novel extended thiazolotriazoles (8a-8j) and triazolothiadiazines (11a-11j) including aminotriazole intermediate 10. After successful synthesis, all the compounds were evaluated for their inhibition potential against cytosolic isoforms of human carbonic anhydrase (hCA I, II), tumor-linked transmembrane isoforms (hCA IX, XII), and cathepsin B. As per the inhibition data, the newly synthesized compounds showed poor inhibition against hCA I. Many of the compounds showed effective inhibition toward hCA IX and/or XII in low nanomolar concentration. Despite the strong to moderate inhibition of hCA II by these compounds, more than half of them demonstrated better inhibition against hCA IX and/or XII, comparatively. Further, insights of CA inhibition data of these extended analogs and their comparison with earlier reported thiazolotriazole and triazolothiadiazine derivatives might help in the rational design of novel potent and selective hCA IX and XII inhibitors. The novel compounds were also found to possess anti-cathepsin B potential at a low concentration of 10-7 M. Broadly, compounds of series 11a-11j presented more effective inhibition against cathepsin B than their counterparts in series 8a-8j. Moreover, these in vitro results with respect to cathepsin B inhibition were also supported by the in silico insights obtained via molecular modeling studies.

Enzyme-responsive liposomes for controlled drug release

Compared to other nanovectors, liposomes exhibit unique advantages, such as good biosafety and high drug-loading capacity. However, slow drug release from conventional liposomes makes most payloads unavailable, restricting the therapeutic efficacy. Therefore, in the last ∼20 years, enzyme-responsive liposomes have been extensively investigated, which liberate drugs under the stimulation of enzymes overexpressed at disease sites. In this review, we elaborate on the research progress on enzyme-responsive liposomes. The involved enzymes mainly include phospholipases, particularly phospholipase A2, matrix metalloproteinases, cathepsins, and esterases. These enzymes can cleave ester bonds or specific peptide sequences incorporated in the liposomes for controlled drug release by disrupting the primary structure of liposomes, detaching protective polyethylene glycol shells, or activating liposome-associated prodrugs. Despite decades of efforts, there are still a lack marketed products of enzyme-responsive liposomes. Therefore, more efforts should be made to improve the safety and effectiveness of enzyme-responsive liposomes and address the issues associated with production scale-up.

Smart Nanoplatforms Responding to the Tumor Microenvironment for Precise Drug Delivery in Cancer Therapy

The tumor microenvironment (TME) is a complex and dynamic entity, comprising stromal cells, immune cells, blood vessels and extracellular matrix, which is intimately associated with the occurrence and development of cancers, as well as their therapy. Utilizing the shared characteristics of tumors, such as an acidic environment, enzymes and hypoxia, researchers have developed a promising cancer therapy strategy known as responsive release of nano-loaded drugs, specifically targeted at tumor tissues or cells. In this comprehensive review, we provide an in-depth overview of the current fundamentals and state-of-the-art intelligent strategies of TME-responsive nanoplatforms, which include acidic pH, high GSH levels, high-level adenosine triphosphate, overexpressed enzymes, hypoxia and reductive environment. Additionally, we showcase the latest advancements in TME-responsive nanoparticles. In conclusion, we thoroughly examine the immediate challenges and prospects of TME-responsive nanopharmaceuticals, with the expectation that the progress of these targeted nanoformulations will enable the exploitation, overcoming or modulation of the TME, ultimately leading to significantly more effective cancer therapy.

Advances in 2,3-Dimethylmaleic Anhydride (DMMA)-Modified Nanocarriers in Drug Delivery Systems

Cancer represents a significant threat to human health. The cells and tissues within the microenvironment of solid tumors exhibit complex and abnormal properties in comparison to healthy tissues. The efficacy of nanomedicines is inhibited by the presence of substantial and complex physical barriers in the tumor tissue. The latest generation of intelligent drug delivery systems, particularly nanomedicines capable of charge reversal, have shown promise in addressing this issue. These systems can transform their charge from negative to positive upon reaching the tumor site, thereby enhancing tumor penetration via transcytosis and promoting cell internalization by interacting with the negatively charged cell membranes. The modification of nanocarriers with 2,3-dimethylmaleic anhydride (DMMA) and its derivatives, which are responsive to weak acid stimulation, represents a significant advance in the field of charge-reversal nanomedicines. This review provides a comprehensive examination of the recent insights into DMMA-modified nanocarriers in drug delivery systems, with a particular focus on their potential in targeted therapeutics. It also discusses the synthesis of DMMA derivatives and their role in charge reversal, shell detachment, size shift, and ligand reactivation mechanisms, offering the prospect of a tailored, next-generation therapeutic approach to overcome the diverse challenges associated with cancer therapy.

Enhancing Targeted Drug Delivery through Cell-Specific Endosomal Escape

Endosome is a major barrier in the intracellular delivery of drugs, especially for biologics, such as proteins, peptides, and nucleic acids. After being endocytosed, these cargos will be trapped inside the endosomal compartments and finally degraded in the lysosomes. Thus, various strategies have been developed to facilitate the escape of cargos from the endosomes to improve the intracellular delivery efficiency. While the majority of the studies are focusing on strengthening the endosomal escape capability to maximize the delivery outcome, recent evidence suggests that a careful control of the endosomal escape process could provide opportunity for targeted drug delivery. In this concept review, we examined current delivery systems that can sense intra-endosomal factors or external stimuli for controlling endosomal escape toward a targeted intracellular delivery of cargos. Furthermore, the prospects and challenges of such strategies are discussed.

Therapeutic resurgence of 6-diazo-5-oxo-l-norleucine (DON) through tissue-targeted prodrugs

The recognition that rapidly proliferating cancer cells rely heavily on glutamine for their survival and growth has renewed interest in the development of glutamine antagonists for cancer therapy. Glutamine plays a pivotal role as a carbon source for synthesizing lipids and metabolites through the TCA cycle, as well as a nitrogen source for synthesis of amino acid and nucleotides. Numerous studies have explored the significance of glutamine metabolism in cancer, providing a robust rationale for targeting this metabolic pathway in cancer treatment. The glutamine antagonist 6-diazo-5-oxo-l-norleucine (DON) has been explored as an anticancer therapeutic for nearly six decades. Initial investigations revealed remarkable efficacy in preclinical studies and promising outcomes in early clinical trials. However, further advancement of DON was hindered due to dose-limiting gastrointestinal (GI) toxicities as the GI system is highly dependent on glutamine for regulating growth and repair. In an effort to repurpose DON and mitigate gastrointestinal (GI) toxicity concerns, prodrug strategies were utilized. These strategies aimed to enhance the delivery of DON to specific target tissues, such as tumors and the central nervous system (CNS), while sparing DON delivery to normal tissues, particularly the GI tract. When administered at low daily doses, optimized for metabolic inhibition, these prodrugs exhibit remarkable effectiveness without inducing significant toxicity to normal tissues. This approach holds promise for overcoming past challenges associated with DON, offering an avenue for its successful utilization in cancer treatment.

γ-Glutamyltranspeptidase (GGT) Sensitive Fluorescence Probes for Cancer Diagnosis; Brief Review

Millions of deaths occur each year due to the late diagnosis of abnormal cellular growth within the body. However, the devastating impact of this can be significantly reduced if cancer metastasis is detected early through the use of enzymatic biomarkers. Among several biomarkers, γ-glutamyltranspeptidase (GGT) stands out as a member of the aminopeptidase family. It is primarily found on the surface of cancer cells such as glioma, ovarian, lung, and prostate cancer, without being overexpressed in normal cells or tissues. Recent years have witnessed significant progress in the field of cancer monitoring and imaging. Fluorescence sensing techniques have been employed, utilizing organic small molecular probes with enzyme-specific recognition sites. These probes emit a fluorescent signal upon interacting with GGT, enabling the imaging, identification, and differentiation of normal and cancerous cells, tissues, and organs. This review article presents a concise overview of recent progress in fluorescent probes developed for the selective detection of GGT, focusing on their applications in cancer imaging. It highlights the observed alterations in the fluorescence and absorption spectra of the probes before and after interaction with GGT. Additionally, the study investigates the changes in the probe molecule's structure following enzyme treatment, evaluates the sensor's detection limit, and consolidated imaging studies conducted using confocal fluorescence analysis. This comprehensive survey is expected to contribute to the advancement of sensing techniques for biomarker detection and cancer imaging, providing valuable insights for refining methodologies and inspiring future developments in this field.

Engineering small-molecule and protein drugs for targeting bone tumors

Bone cancer is common and severe. Both primary (e.g., osteosarcoma, Ewing sarcoma) and secondary (e.g., metastatic) bone cancers lead to significant health problems and death. Currently, treatments such as chemotherapy, hormone therapy, and radiation therapy are used to treat bone cancer, but they often only shrink or slow tumor growth and do not eliminate cancer completely. The bone microenvironment contributes unique signals that influence cancer growth, immunogenicity, and metastasis. Traditional cancer therapies have limited effectiveness due to off-target effects and poor distribution on bones. As a result, therapies with improved specificity and efficacy for treating bone tumors are highly needed. One of the most promising strategies involves the targeted delivery of pharmaceutical agents to the site of bone cancer by introduction of bone-targeting moieties, such as bisphosphonates or oligopeptides. These moieties have high affinities to the bone hydroxyapatite matrix, a structure found exclusively in skeletal tissue, and can enhance the targeting ability and efficacy of anticancer drugs when combating bone tumors. This review focuses on the engineering of small molecules and proteins with bone-targeting moieties for the treatment of bone tumors.

Enzyme-responsive design combined with photodynamic therapy for cancer treatment

Photodynamic therapy (PDT) is a noninvasive cancer treatment that has garnered significant attention in recent years. However, its application is still hampered by certain limitations, such as the hydrophobicity and low targeting of photosensitizers (PSs) and the hypoxia of the tumor microenvironment. Nevertheless, the fusion of enzyme-responsive drugs with PDT offers novel solutions to overcome these challenges. Utilizing the attributes of enzyme-responsive drugs, PDT can deliver PSs to the target site and selectively release them, thereby enhancing therapeutic outcomes. In this review, we spotlight recent advances in enzyme-responsive materials for cancer treatment and primarily delineate their application in combination with PDT.

Ruthenium-Cathepsin Inhibitor Conjugates for Green Light-Activated Photodynamic Therapy and Photochemotherapy

Dysregulated cathepsin activity is linked to various human diseases including metabolic disorders, autoimmune conditions, and cancer. Given the overexpression of cathepsin in the tumor microenvironment, cathepsin inhibitors are promising pharmacological agents and drug delivery vehicles for cancer treatment. In this study, we describe the synthesis and photochemical and biological assessment of a dual-action agent based on ruthenium that is conjugated with a cathepsin inhibitor, designed for both photodynamic therapy (PDT) and photochemotherapy (PCT). The ruthenium-cathepsin inhibitor conjugate was synthesized through an oxime click reaction, combining a pan-cathepsin inhibitor based on E64d with the Ru(II) PCT/PDT fragment [Ru(dqpy)(dppn)], where dqpy = 2,6-di(quinoline-2-yl)pyridine and dppn = benzo[i]dipyrido[3,2-a:2',3'-c]phenazine. Photochemical investigations validated the conjugate's ability to release a triazole-containing cathepsin inhibitor for PCT and to generate singlet oxygen for PDT upon exposure to green light. Inhibition studies demonstrated the conjugate's potent and irreversible inactivation of purified and intracellular cysteine cathepsins. Two Ru(II) PCT/PDT agents based on the [Ru(dqpy)(dppn)] moiety were evaluated for photoinduced cytotoxicity in 4T1 murine triple-negative breast cancer cells, L929 fibroblasts, and M0, M1, and M2 macrophages. The cathepsin inhibitor conjugate displayed notable selectivity for inducing cell death under irradiation compared to dark conditions, mitigating toxicity in the dark observed with the triazole control complex [Ru(dqpy)(dppn)(MeTz)]2+ (MeTz = 1-methyl-1H-1,2,4-triazole). Notably, our lead complex is among a limited number of dual PCT/PDT agents activated with green light.

Responsive Supramolecular Polymers for Diagnosis and Treatment

Stimuli-responsive supramolecular polymers are ordered nanosized materials that are held together by non-covalent interactions (hydrogen-bonding, metal-ligand coordination, π-stacking and, host-guest interactions) and can reversibly undergo self-assembly. Their non-covalent nature endows supramolecular polymers with the ability to respond to external stimuli (temperature, light, ultrasound, electric/magnetic field) or environmental changes (temperature, pH, redox potential, enzyme activity), making them attractive candidates for a variety of biomedical applications. To date, supramolecular research has largely evolved in the development of smart water-soluble self-assemblies with the aim of mimicking the biological function of natural supramolecular systems. Indeed, there is a wide variety of synthetic biomaterials formulated with responsiveness to control and trigger, or not to trigger, aqueous self-assembly. The design of responsive supramolecular polymers ranges from the use of hydrophobic cores (i.e., benzene-1,3,5-tricarboxamide) to the introduction of macrocyclic hosts (i.e., cyclodextrins). In this review, we summarize the most relevant advances achieved in the design of stimuli-responsive supramolecular systems used to control transport and release of both diagnosis agents and therapeutic drugs in order to prevent, diagnose, and treat human diseases.

Cathepsin B: The dawn of tumor therapy

Cathepsin B (CTSB) is a key lysosomal protease that plays a crucial role in the development of cancer. This article elucidates the relationship between CTSB and cancer from the perspectives of its structure, function, and role in tumor growth, migration, invasion, metastasis, angiogenesis and autophagy. Further, we summarized the research progress of cancer treatment related drugs targeting CTSB, as well as the potential and advantages of Traditional Chinese medicine in treating tumors by regulating the expression of CTSB.

Novel 1,2,4-triazoles as selective carbonic anhydrase inhibitors showing ancillary anticathepsin B activity

Background: Exploration of the multi-target approach considering both human carbonic anhydrase (hCA) IX and XII and cathepsin B is a promising strategy to target cancer. Methodology & Results: 22 novel 1,2,4-triazole derivatives were synthesized and evaluated for their inhibition efficacy against hCA I, II, IX, XII isoforms and cathepsin B. The compounds demonstrated effective inhibition against hCA IX and/or XII isoforms with considerable selectivity over off-target hCA I/II. All compounds presented significant anticathepsin B activities at a low concentration of 10-7 M and in vitro results were also supported by the molecular modeling studies. Conclusion: Insights of present study can be utilized in the rational design of effective and selective hCA IX and XII inhibitors capable of inhibiting cathepsin B.

Selective Intracellular Delivery of Antibodies in Cancer Cells with Nanocarriers Sensing Endo/Lysosomal Enzymatic Activity

The differential enzymatic activity in the endo/lysosomes of particular cells could trigger targeted endosomal escape functions, enabling selective intracellular protein delivery. However, this strategy may be jeopardized due to protein degradation during endosomal trafficking. Herein, using custom made fluorescent probes to assess the endosomal activity of cathepsin B (CTSB) and protein degradation, we found that certain cancer cells with hyperacidified endosomes grant a spatiotemporal window where CTSB activity surpass protein digestion. This inspired the engineering of antibody-loaded polymeric nanocarriers having CTSB-activatable endosomal escape ability. The nanocarriers selectively escaped from the endo/lysosomes in the cells with high endosomal CTSB activity and delivered active antibodies to intracellular targets. This study provides a viable strategy for cell-specific protein delivery using stimuli-responsive nanocarriers with controlled endosomal escape.

Ursolic acid alleviates meiotic abnormalities induced by 3-nitropropionic acid in mouse oocytes

3-nitropropionic acid (3-NPA), a toxic metabolite produced by mold, is mainly found in moldy sugarcane. 3-NPA inhibits the activity of succinate dehydrogenase that can induce oxidative stress injury in cells, reduce ATP production and induce oxidative stress in mouse ovaries to cause reproductive disorders. Ursolic acid (UA) has a variety of biological activities and is a pentacyclic triterpene compound found in many plants. This experiment aimed to investigate the cytotoxicity of 3-NPA during mouse oocyte in vitro maturation and the protective effects of UA on oocytes challenged with 3-NPA. The results showed that UA could alleviate 3-NPA-induced oocyte meiotic maturation failure. Specifically, 3-NPA induced a decrease in the first polar body extrusion rate of oocytes, abnormal distribution of cortical granules, and an increase in the proportion of spindle abnormalities. In addition, 3-NPA caused mitochondrial dysfunction and induced oxidative stress, including decreases in the GSH, mitochondrial membrane potential and ATP levels, and increases in the ROS levels, and these effects led to apoptosis and autophagy. The addition of UA could significantly improve the adverse effects caused by 3-NPA. In general, our data show that 3-NPA affects the normal development of oocytes during the in vitro culture, and the addition of UA can effectively repair the damage caused by 3-NPA to oocytes.

Strategies to address key challenges of metallacycle/metallacage-based supramolecular coordination complexes in biomedical applications

Owing to their capacity for dynamically linking two or more functional molecules, supramolecular coordination complexes (SCCs), exemplified by two-dimensional (2D) metallacycles and three-dimensional (3D) metallacages, have gained increasing significance in biomedical applications. However, their inherent hydrophobicity and self-assembly driven by heavy metal ions present common challenges in their applications. These challenges can be overcome by enhancing the aqueous solubility and in vivo circulation stability of SCCs, alongside minimizing their side effects during treatment. Addressing these challenges is crucial for advancing the fundamental research of SCCs and their subsequent clinical translation. In this review, drawing on extensive contemporary research, we offer a thorough and systematic analysis of the strategies employed by SCCs to surmount these prevalent yet pivotal obstacles. Additionally, we explore further potential challenges and prospects for the broader application of SCCs in the biomedical field.

1,2,3-Triazole-based esters and carboxylic acids as nonclassical carbonic anhydrase inhibitors capable of cathepsin B inhibition

Herein, we report the design and synthesis of a library of 28 new 1,2,3-triazole derivatives bearing carboxylic acid and ester moieties as dual inhibitors of carbonic anhydrase (CA) and cathepsin B enzymes. The synthesised compounds were assayed in vitro for their inhibition potential against four human CA (hCA) isoforms, I, II, IX and XII. The carboxylic acid derivatives displayed low micromolar inhibition against hCA II, IX and XII in contrast to the ester derivatives. Most of the target compounds showed poor inhibition against the hCA I isoform. 4-Fluorophenyl appended carboxylic acid derivative 6c was found to be the most potent inhibitor of hCA IX and hCA XII with a KI value of 0.7 μM for both the isoforms. The newly synthesised compounds showed dual inhibition towards CA as well as cathepsin B. The ester derivatives exhibited higher % inhibition at 10-7  M concentration as compared with the corresponding carboxylic acid derivatives against cathepsin B. The results from in silico studies of the target compounds with the active site of cathepsin B were found in good correlation with the in vitro results. Moreover, two compounds, 5i and 6c, showed cytotoxic activity against A549 lung cancer cells, with IC50 values lower than 100 μM.

Potent antitumor activity of anti-HER2 antibody-topoisomerase I inhibitor conjugate based on self-immolative dendritic dimeric-linker

Antibody-drug conjugates (ADCs) are a rapidly expanding class of anticancer therapeutics, with 14 ADCs already approved worldwide. We developed unique linker technologies for the bioconjugation of drug molecules with controlled-release applications. We synthesized cathepsin-cleavable ADCs using a dimeric prodrug system based on a self-immolative dendritic scaffold, resulting in a high drug-antibody ratio (DAR) with the potential to reach 16 payloads due to its dendritic structure, increased stability in the circulation and efficient release profile of a highly cytotoxic payload at the targeted site. Using our novel cleavable linker technologies, we conjugated the anti-human epidermal growth factor receptor 2 (anti-HER2) antibody, trastuzumab, with topoisomerase I inhibitors, exatecan or belotecan. The newly synthesized ADCs were tested in vitro on mammary carcinoma cells overexpressing human HER2, demonstrating a substantial inhibitory effect on the proliferation of HER2-positive cells. Importantly, a single dose of our trastuzumab-based ADCs administered in vivo to mice bearing HER2-positive tumors, showed a dose-dependent inhibition of tumor growth and survival benefit, with the most potent antitumor effects observed at 10 mg/kg, which resulted in complete tumor regression and survival of 100% of the mice. Overall, our novel dendritic technologies using the protease-cleavable Val-Cit linker present an opportunity for the development of highly selective and potent controlled-released therapeutic payloads. This strategy could potentially lead to the development of novel and effective ADC technologies for patients diagnosed with HER2-positive cancers. Moreover, our proposed ADC linker technology can be implemented in additional medical conditions such as other malignancies as well as autoimmune diseases that overexpress targets, other than HER2.

Role of Cathepsin B Expression in Oral Squamous Cell Carcinoma: A Comprehensive Review

This comprehensive review delves into the intricate landscape of oral squamous cell carcinoma (OSCC) by examining the role of cathepsin B expression in its pathogenesis. OSCC, a prevalent and clinically significant oral malignancy, poses a considerable global health burden, necessitating a thorough exploration of its underlying molecular mechanisms. Cathepsin B, a lysosomal cysteine protease, emerges as a critical player in OSCC, influencing tumour initiation, invasion, and metastasis. The review begins with a brief overview of OSCC, emphasizing its epidemiological and clinical features, followed by exploring the significance of studying cathepsin B expression in this context. In the manuscript, the structure and function of cathepsin B are elucidated, providing a foundation for understanding its aberrant expression in OSCC. Clinical studies revealing correlations with tumour grade and stage, along with prognostic significance, are scrutinized, offering insights into the potential diagnostic and prognostic utility of cathepsin B. The biological functions of cathepsin B in OSCC, including its impact on tumour invasion and modulation of apoptosis, are comprehensively discussed. The Therapeutic Implications section explores targeting cathepsin B as a potential strategy, emphasizing the need for future research to overcome associated challenges. In the Conclusion section, the review synthesizes key findings, delineates implications for future research, and highlights the potential impact of cathepsin B on OSCC diagnosis and treatment, contributing to the ongoing efforts to advance our understanding of this complex malignancy, which is associated with a high mortality rate and improve clinical outcomes.

Reactions of Medicinal Gold Compounds with Cathepsin B Explored through Electrospray Mass Spectrometry Measurements

Medicinal gold compounds, a novel class of potential anticancer drugs, are believed to produce their pharmacological effects mainly through direct gold binding to protein targets at the level of solvent exposed cysteine (or selenocysteine) residues. We have explored therein the reactions of a panel of seven representative gold compounds with the cysteine protease cathepsin B according to an established ESI MS approach. Detailed information on the mode of protein binding of these gold compounds is gained; notably, quite distinct patterns of cathepsin B metalation have emerged from these studies. It is shown that panel gold compounds interact preferentially, often exclusively, with the free cysteine located in the active site of the enzyme.

DNA-Barcoded Plasmonic Nanostructures for Activity-Based Protease Sensing

We report the development of a new class of protease activity sensors called DNA-barcoded plasmonic nanostructures. These probes are comprised of gold nanoparticles functionalized with peptide-DNA conjugates (GPDs), where the peptide is a substrate of the protease of interest. The DNA acts as a barcode identifying the peptide and facilitates signal amplification. Protease-mediated peptide cleavage frees the DNA from the nanoparticle surface, which is subsequently measured via a CRISPR/Cas12a-based assay as a proxy for protease activity. As proof-of-concept, we show activity-based, multiplexed detection of the SARS-CoV-2-associated protease, 3CL, and the apoptosis marker, caspase 3, with high sensitivity and selectivity. GPDs yield >25-fold turn-on signals, 100-fold improved response compared to commercial probes, and detection limits as low as 58 pM at room temperature. Moreover, nanomolar concentrations of proteases can be detected visually by leveraging the aggregation-dependent color change of the gold nanoparticles. We showcase the clinical potential of GPDs by detecting a colorectal cancer-associated protease, cathepsin B, in three different patient-derived cell lines. Taken together, GPDs detect physiologically relevant concentrations of active proteases in challenging biological samples, require minimal sample processing, and offer unmatched multiplexing capabilities (mediated by DNA), making them powerful chemical tools for biosensing and disease diagnostics.

Antibody-drug conjugates in cancer therapy: innovations, challenges, and future directions

The emergence of antibody-drug conjugates (ADCs) as a potential therapeutic avenue in cancer treatment has garnered significant attention. By combining the selective specificity of monoclonal antibodies with the cytotoxicity of drug molecules, ADCs aim to increase the therapeutic index, selectively targeting cancer cells while minimizing systemic toxicity. Various ADCs have been licensed for clinical usage, with ongoing research paving the way for additional options. However, the manufacture of ADCs faces several challenges. These include identifying suitable target antigens, enhancing antibodies, linkers, and payloads, and managing resistance mechanisms and side effects. This review focuses on the strategies to overcome these hurdles, such as site-specific conjugation techniques, novel antibody formats, and combination therapy. Our focus lies on current advancements in antibody engineering, linker technology, and cytotoxic payloads while addressing the challenges associated with ADC development. Furthermore, we explore the future potential of personalized medicine, leveraging individual patients' molecular profiles, to propel ADC treatments forward. As our understanding of the molecular mechanisms driving cancer progression continues to expand, we anticipate the development of new ADCs that offer more effective and personalized therapeutic options for cancer patients.

Considerations for the design of antibody drug conjugates (ADCs) for clinical development: lessons learned

Antibody-drug conjugates (ADCs) have emerged as a novel therapeutic strategy that has successfully reached patient treatment in different clinical scenarios. ADCs are formed by an antibody against a specific tumor-associated antigen (TAA), a cytotoxic payload, and a chemical linker that binds both. To this regard, most efforts have been focused on target identification, antibody design and linker optimization, but other relevant aspects for clinical development have not received the necessary attention. In this article using data from approved ADCs, we evaluated all characteristics of these agents, including payload physicochemical properties, in vitro potency, drug antibody ratio (DAR), exposure-response relationships, and clinical development strategies. We suggest that compounds with best options for clinical development include those with optimal payload physicochemical properties and cleavable linkers that would lead to a bystander effect. These modalities can facilitate the development of ADCs in indications with low expression of the TAA. Early clinical development strategies including changes in the schedule of administration with more frequent doses are also discussed in the context of an efficient strategy. In conclusion, we highlight relevant aspects that are needed for the optimal development of ADCs in cancer, proposing options for improvement.

The cell type dependent sorting of CD9- and CD81 to extracellular vesicles can be exploited to convey tumor sensitive cargo to target cells

Extracellular vesicles (EVs) are lipid membrane-bound particles involved in cell-to-cell communication through a delivery of regulatory molecules essential for physiological processes. Since EVs efficiently vectorize specific cargo molecules, they have been proposed as suitable vehicles for therapeutic agents. Drug loading into EVs can be achieved by active, exogenous strategies or by genetic modifications of vesicle-producing cells. With the aim to produce EVs conveying therapeutic proteins, we genetically engineered and compared HEK293 to tumor cells. Tetraspanin-based RFP fusions were found to be more stable and preferentially sorted into EVs in HEK293. EVs isolated from genetically modified HEK293 cells media were captured by cancer cells, efficiently delivering their cargo. Cathepsin B cleavage site introduced between CD9/CD81 and RFP was recognized by tumor specific proteases allowing the release of the reporter protein. Our results indicate HEK293 cells as a preferential system for the production of EVs and pave the way to the development of nano-platforms for the efficient delivery of therapeutic proteins and prodrugs to tumor cells.

Potent inhibitors of tumor associated carbonic anhydrases endowed with cathepsin B inhibition

Twenty-one novel extended analogs of acetazolamide were synthesized and screened in vitro for their inhibition efficacy against human carbonic anhydrase (hCA) isoforms I, II, IX, XII, and cathepsin B. The majority of the compounds were found to be effective inhibitors of tumor-associated hCA IX and XII, and poor inhibitors of cytosolic hCA I. Despite the strong to moderate inhibition potential possessed by these compounds toward another cytosolic isoform hCA II, some of them demonstrated better potency against hCA IX and/or XII isoforms as compared to hCA II. Four compounds (11f, 11g, 12c, and 12g) effectively inhibited hCA IX and/or XII isoforms with considerable selectivity over the off-targets hCA I and II. Interestingly, five compounds, including 11f, 11g, 12c, 12d, and 12g, inhibited hCA IX even better than the clinically used acetazolamide. Some of the novel synthesized compounds exhibited higher anti-cathepsin B potential than acetazolamide, with % inhibition of around 50%, at a concentration of 10-7  M. Further, two compounds (12g and 12c) that showed effective and selective inhibition activity profiles against hCA IX and XII were additionally found to be effective inhibitors of cathepsin B.

Fluorescent Probes for Imaging in Humans: Where Are We Now?

Optical imaging has become an indispensable technology in the clinic. The molecular design of cell-targeted and highly sensitive materials, the validation of specific disease biomarkers, and the rapid growth of clinically compatible instrumentation have altogether revolutionized the way we use optical imaging in clinical settings. One prime example is the application of cancer-targeted molecular imaging agents in both trials and routine clinical use to define the margins of tumors and to detect lesions that are "invisible" to the surgeons, leading to improved resection of malignant tissues without compromising viable structures. In this Perspective, we summarize some of the key research advances in chemistry, biology, and engineering that have accelerated the translation of optical imaging technologies for use in human patients. Finally, our paper comments on several research areas where further work will likely render the next generation of technologies for translational optical imaging.

In vitro anti-cancer activity of a polyherbal preparation, VEDICINALS®9, against A549 human lung adenocarcinoma cells

PURPOSE

Non-small cell lung cancer (NSCLC) is among the leading causes of morbidity and mortality worldwide. Despite the availability of several treatment options, the five-year survival rate of NSCLC is extremely low (<20%). This underlines the necessity of more effective therapeutic alternatives. In this context, plant-derived extracts and bioactive molecules extracted from plants, known collectively as phytoceuticals, represent an extremely variegated source of bioactive compounds with potent anticancer potential. In the present study, we tested the in vitro anticancer activity of a polyherbal preparation, VEDICINALS®9, containing nine different bioactive principles extracted by medicinal plants.

METHODS

The anticancer activity of VEDICINALS®9 was investigated by measuring its impact on A549 human NSCLC cell proliferation (MTT assay and trypan blue staining), migration (wound healing assay and transwell chamber assay) and by measuring the impact on the expression of cancer-related proteins (Human XL Oncology Protein Array).

RESULTS

We show that VEDICINALS®9 at a concentration of 0.2% v/v has potent anticancer effect, significantly inhibiting A549 cell proliferation and migration. Mechanistically, this was achieved by downregulating the expression of proteins involved in cancer cell proliferation (Axl, FGF basic, enolase 2, progranulin, survivin) and migration (Dkk-1, cathepsins B and D, BCL-x, amphiregulin, CapG, u-plasminogen activator). Furthermore, treatment with VEDICINALS®9 resulted in increased expression of the oncosuppressor protein p53 and of the angiogenesis inhibitor endostatin.

CONCLUSIONS

Taken together, our results provide proof of principle of the potent anticancer activity of the polyherbal preparation VEDICINALS®9, highlighting its enormous potential as an alternative or adjuvant therapy for lung cancer.

Keto-bridged dual triazole-linked benzenesulfonamides as potent carbonic anhydrase and cathepsin B inhibitors

Background: Inhibition of human carbonic anhydrase (hCA) isoforms IX and XII with concurrent inhibition of cathepsin B is a promising approach for targeting cancers. Methods/results: 28 keto-bridged dual triazole-containing benzenesulfonamides were synthesized and tested, following the multitarget approach, for their efficacy as inhibitors of cathepsin B and hCA isoforms (I, II, IX, XII). The synthesized compounds showed excellent inhibition of CA isoforms (IX and XII) and cathepsin B. Compound 8i exhibited better and more selective inhibition of the cancer-associated isoform hCA IX as compared with acetazolamide (reference drug) and SLC-0111 (potent lead as carbonic anhydrase inhibitor). Molecular docking studies were also carried out. Conclusion: The present work gives important generalizations for the development of isoform-selective hCA inhibitors endowed with anti-cathepsin properties.

Tumor Abnormality-Oriented Nanomedicine Design

Anticancer nanomedicines have been proven effective in mitigating the side effects of chemotherapeutic drugs. However, challenges remain in augmenting their therapeutic efficacy. Nanomedicines responsive to the pathological abnormalities in the tumor microenvironment (TME) are expected to overcome the biological limitations of conventional nanomedicines, enhance the therapeutic efficacies, and further reduce the side effects. This Review aims to quantitate the various pathological abnormalities in the TME, which may serve as unique endogenous stimuli for the design of stimuli-responsive nanomedicines, and to provide a broad and objective perspective on the current understanding of stimuli-responsive nanomedicines for cancer treatment. We dissect the typical transport process and barriers of cancer drug delivery, highlight the key design principles of stimuli-responsive nanomedicines designed to tackle the series of barriers in the typical drug delivery process, and discuss the "all-into-one" and "one-for-all" strategies for integrating the needed properties for nanomedicines. Ultimately, we provide insight into the challenges and future perspectives toward the clinical translation of stimuli-responsive nanomedicines.

A comprehensive overview on antibody-drug conjugates: from the conceptualization to cancer therapy

Antibody-Drug Conjugates (ADCs) represent an innovative class of potent anti-cancer compounds that are widely used in the treatment of hematologic malignancies and solid tumors. Unlike conventional chemotherapeutic drug-based therapies, that are mainly associated with modest specificity and therapeutic benefit, the three key components that form an ADC (a monoclonal antibody bound to a cytotoxic drug via a chemical linker moiety) achieve remarkable improvement in terms of targeted killing of cancer cells and, while sparing healthy tissues, a reduction in systemic side effects caused by off-tumor toxicity. Based on their beneficial mechanism of action, 15 ADCs have been approved to date by the market approval by the Food and Drug Administration (FDA), the European Medicines Agency (EMA) and/or other international governmental agencies for use in clinical oncology, and hundreds are undergoing evaluation in the preclinical and clinical phases. Here, our aim is to provide a comprehensive overview of the key features revolving around ADC therapeutic strategy including their structural and targeting properties, mechanism of action, the role of the tumor microenvironment and review the approved ADCs in clinical oncology, providing discussion regarding their toxicity profile, clinical manifestations and use in novel combination therapies. Finally, we briefly review ADCs in other pathological contexts and provide key information regarding ADC manufacturing and analytical characterization.

Intra-Lysosomal Peptide Assembly for the High Selectivity Index against Cancer

Lysosomes remain powerful organelles and important targets for cancer therapy because cancer cell proliferation is greatly dependent on effective lysosomal function. Recent studies have shown that lysosomal membrane permeabilization induces cell death and is an effective way to treat cancer by bypassing the classical caspase-dependent apoptotic pathway. However, most lysosome-targeted anticancer drugs have very low selectivity for cancer cells. Here, we show intra-lysosomal self-assembly of a peptide amphiphile as a powerful technique to overcome this problem. We designed a peptide amphiphile that localizes in the cancer lysosome and undergoes cathepsin B enzyme-instructed supramolecular assembly. This localized assembly induces lysosomal swelling, membrane permeabilization, and damage to the lysosome, which eventually causes caspase-independent apoptotic death of cancer cells without conventional chemotherapeutic drugs. It has specific anticancer effects and is effective against drug-resistant cancers. Moreover, this peptide amphiphile exhibits high tumor targeting when attached to a tumor-targeting ligand and causes significant inhibition of tumor growth both in cancer and drug-resistant cancer xenograft models.

Genetic association of cardiovascular disease related biomarkers with the overall survival of hepatocellular carcinoma: a Mendelian randomization analysis

Observational studies have reported associations between circulating biomarkers related to cardiovascular disease and the survival of patients with hepatocellular carcinoma. However, the relationship between these biomarkers and survival remains controversial. We conducted a two-sample Mendelian randomization analysis to investigate possible causal associations between cardiovascular disease biomarkers and hepatocellular carcinoma survival. Genetic risk scores, calculated using individual-level data from 866 cases of hepatitis B virus-related hepatocellular carcinoma in Guangxi, were utilized as proxies for four cardiovascular disease biomarkers: C-reactive protein, Apolipoprotein A-1, Cystatin C, and Lipoprotein(a). Associations between the genetic scores and survival were analyzed using Cox regression. The inverse-variance weighted method was used to estimate the summary statistics for the biomarkers and survival. Considering the multiple comparisons, the statistical significance was set at P < 0.0125. We observed a significant risk signal between genetically increased Cystatin C levels and poorer survival in hepatocellular carcinoma (HR for genetic scores = 1.29, 95% CI = 1.02-1.64; HR for inverse-variance weighted = 2.60, 95% CI = 1.45-4.65). Furthermore, we found a causal relationship of genetically determined Cystatin C and Lipoprotein(a) level with the survival of hepatocellular carcinoma patients with embolus. Our findings indicated the causal effects of increased levels of Cystatin C and Lipoprotein(a) on poorer survival in hepatocellular carcinoma.

Mechanisms and applications of radiation-induced oxidative stress in regulating cancer immunotherapy

Radiotherapy (RT) is an effective treatment option for cancer patients, which induces the production of reactive oxygen species (ROS) and causes oxidative stress (OS), leading to the death of tumor cells. OS not only causes apoptosis, autophagy and ferroptosis, but also affects tumor immune response. The combination of RT and immunotherapy has revolutionized the management of various cancers. In this process, OS caused by ROS plays a critical role. Specifically, RT-induced ROS can promote the release of tumor-associated antigens (TAAs), regulate the infiltration and differentiation of immune cells, manipulate the expression of immune checkpoints, and change the tumor immune microenvironment (TME). In this review, we briefly summarize several ways in which IR induces tumor cell death and discuss the interrelationship between RT-induced OS and antitumor immunity, with a focus on the interaction of ferroptosis with immunogenic death. We also summarize the potential mechanisms by which ROS regulates immune checkpoint expression, immune cells activity, and differentiation. In addition, we conclude the therapeutic opportunity improving radiotherapy in combination with immunotherapy by regulating OS, which may be beneficial for clinical treatment.

Antibody-Drug Conjugates: A Review of Approved Drugs and Their Clinical Level of Evidence

Antibody-drug conjugates (ADCs) are an innovative family of agents assembled through linking cytotoxic drugs (payloads) covalently to monoclonal antibodies (mAbs) to be delivered to tumor tissue that express their particular antigen, with the theoretical advantage of an augmented therapeutic ratio. As of June 2023, eleven ADCs have been approved by the Food and Drug Administration (FDA) and are on the market. These drugs have been added to the therapeutic armamentarium of acute myeloblastic and lymphoblastic leukemias, various types of lymphoma, breast, gastric or gastroesophageal junction, lung, urothelial, cervical, and ovarian cancers. They have proven to deliver more potent and effective anti-tumor activities than standard practice in a wide variety of indications. In addition to targeting antigen-expressing tumor cells, bystander effects have been engineered to extend cytotoxic killing to low-antigen-expressing or negative tumor cells in the heterogenous tumor milieu. Inevitably, myelosuppression is a common side effect with most of the ADCs due to the effects of the cytotoxic payload. Also, other unique side effects are specific to the tissue antigen that is targeted for, such as the cardiac toxicity with Her-2 targeting ADCs, and the hemorrhagic side effects with the tissue factor (TF) targeting Tisotumab vedotin. Further exciting developments are centered in the strategies to improve the tolerability and efficacy of the ADCs to improve the therapeutic window; as well as the development of novel payloads including (1) peptide-drug conjugates (PDCs), with the peptide replacing the monoclonal antibody, rendering greater tumor penetration; (2) immune-stimulating antibody conjugates (ISACs), which upon conjugation of the antigen, cause an influx of pro-inflammatory cytokines to activate dendritic cells and harness an anti-tumor T-cell response; and (3) the use of radioactive isotopes as a payload to enhance cytotoxic activity.

Antibody-Drug Conjugates: Ushering in a New Era of Cancer Therapy

Antibody-drug conjugates (ADCs) have provided new therapeutic options and significant promise for patients with cancer, particularly where existing treatments are limited. Substantial effort in ADC development is underway globally, with 13 ADCs currently approved and many more in development. The therapeutic benefits of ADCs leverage the ability to selectively target cancer cells through antibody binding, resultant relative sparing of non-malignant tissues, and the targeted delivery of a cytotoxic payload. Consequently, this drug class has demonstrated activity in multiple malignancies refractory to standard therapeutic options. Despite this, limitations exist, including narrow therapeutic windows, unique toxicity profiles, development of therapeutic resistance, and appropriate biomarker selection. This review will describe the development of ADCs, their mechanisms of action, pivotal trials, and approved indications and identify common themes. Current challenges and opportunities will be discussed for this drug class in cancer therapeutics at a time when significant developments in antibody therapies, immunotherapy, and targeted agents are occurring.

Targeting CD44 Variant 5 with an Antibody-Drug Conjugate Is an Effective Therapeutic Strategy for Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is the second most frequent type of primary liver cancer. ICC is among the deadliest malignancies, highlighting that novel treatments are urgently needed. Studies have shown that CD44 variant isoforms, rather than the CD44 standard isoform, are selectively expressed in ICC cells, providing an opportunity for the development of an antibody-drug conjugate (ADC)-based targeted therapeutic strategy. In this study, we observed the specific expression of CD44 variant 5 (CD44v5) in ICC tumors. CD44v5 protein was expressed on the surface of most ICC tumors (103 of 155). A CD44v5-targeted ADC, H1D8-DC (H1D8-drug conjugate), was developed that comprises a humanized anti-CD44v5 mAb conjugated to the microtubule inhibitor monomethyl auristatin E (MMAE) via a cleavable valine-citrulline-based linker. H1D8-DC exhibited efficient antigen binding and internalization in cells expressing CD44v5 on the cell surface. Because of the high expression of cathepsin B in ICC cells, the drug was preferentially released in cancer cells but not in normal cells, thus inducing potent cytotoxicity at picomolar concentrations. In vivo studies showed that H1D8-DC was effective against CD44v5-positive ICC cells and induced tumor regression in patient-derived xenograft models, whereas no significant adverse toxicities were observed. These data demonstrate that CD44v5 is a bona fide target in ICC and provide a rationale for the clinical investigation of a CD44v5-targeted ADC-based approach.

SIGNIFICANCE

Elevated expression of CD44 variant 5 in intrahepatic cholangiocarcinoma confers a targetable vulnerability using the newly developed antibody-drug conjugate H1D8-DC, which induces potent growth suppressive effects without significant toxicity.

Dichloro Ru(II)-p-cymene-1,3,5-triaza-7-phosphaadamantane (RAPTA-C): A Case Study

The use of organometallic compounds to treat various phenotypes of cancer has attracted increased interest in recent decades. Organometallic compounds, which are transitional between conventional inorganic and organic materials, have outstanding and one-of-a-kind features that offer fresh insight into the development of inorganic medicinal chemistry. The therapeutic potential of ruthenium(II)-arene RAPTA-type compounds is being thoroughly investigated, specifically owing to the excellent antimetastatic property of the initial candidate RAPTA-C. This review gives a thorough analysis of this complex and its evolution as a potential anticancer drug candidate. The numerous mechanistic investigations of RAPTA-C are discussed, and they are connected to the macroscopic biological characteristics that have been found. The "multitargeted" complex described here target enzymes, peptides, and intracellular proteins in addition to DNA that allow it to specifically target cancer cells. Understanding these may allow researchers to find specific targets and tune a new-generation organometallic complex accordingly.

Expression, Intracellular Localization, and Maturation of Cysteine Cathepsins in Renal Embryonic and Cancer Cell Lines

Cysteine cathepsins play an important role in tumor development and metastasis. The expression of these enzymes is often increased in many types of tumor cells. Cysteine cathepsins contribute to carcinogenesis through a number of mechanisms, including proteolysis of extracellular matrix and signaling molecules on the cell surface, as well as degradation of transcription factors and disruption of signaling cascades in the cell nucleus. Distinct oncogenic functions have been reported for several members of the cysteine cathepsin family in various types of cancer, but a comparative study of all eleven cysteine cathepsins in one experimental model is still missing. In this work, we assessed and compared the expression, localization, and maturation of all eleven cysteine cathepsins in embryonic kidney cells HEK293 and kidney cancer cell lines 769-P and A-498. We found that the expression of cathepsins V, B, Z, L, and S was 3- to 9-fold higher in kidney tumor cells than in embryonic cells. We also showed that all cysteine cathepsins were present in varying amounts in the nucleus of both embryonic and tumor cells. Notably, more than half of the cathepsin Z or K and over 88% of cathepsin F were localized in tumor cell nuclei. Moreover, mature forms of cysteine cathepsins were more prevalent in tumor cells than in embryonic cells. These results can be further used to develop novel diagnostic tools and may assist in the investigation of cysteine cathepsins as potential therapeutic targets.

Proteolytic signaling in cancer

INTRODUCTION

Cancer is a disease of (altered) biological pathways, often driven by somatic mutations and with several implications. Therefore, the identification of potential markers of disease is challenging. Given the large amount of biological data generated with omics approaches, oncology has experienced significant contributions. Proteomics mapping of protein fragments, derived from proteolytic processing events during oncogenesis, may shed light on (i) the role of active proteases and (ii) the functional implications of processed substrates in biological signaling circuits. Both outcomes have the potential for predicting diagnosis/prognosis in diseases like cancer. Therefore, understanding proteolytic processing events and their downstream implications may contribute to advances in the understanding of tumor biology and targeted therapies in precision medicine.

AREAS COVERED

Proteolytic events associated with some hallmarks of cancer (cell migration and proliferation, angiogenesis, metastasis, as well as extracellular matrix degradation) will be discussed. Moreover, biomarker discovery and the use of proteomics approaches to uncover proteolytic signaling events will also be covered.

EXPERT OPINION

Proteolytic processing is an irreversible protein post-translational modification and the deconvolution of biological data resulting from the study of proteolytic signaling events may be used in both patient diagnosis/prognosis and targeted therapies in cancer.

Cathepsins in oral diseases: mechanisms and therapeutic implications

Cathepsins are a type of lysosomal globulin hydrolase and are crucial for many physiological processes, including the resorption of bone matrix, innate immunity, apoptosis, proliferation, metastasis, autophagy, and angiogenesis. Findings regarding their functions in human physiological processes and disorders have drawn extensive attention. In this review, we will focus on the relationship between cathepsins and oral diseases. We highlight the structural and functional properties of cathepsins related to oral diseases, as well as the regulatory mechanisms in tissue and cells and their therapeutic uses. Elucidating the associated mechanism between cathepsins and oral diseases is thought to be a promising strategy for the treatment of oral diseases and may be a starting point for further studies at the molecular level.

Old Drug, New Delivery Strategy: MMAE Repackaged

Targeting therapy is a concept that has gained significant importance in recent years, especially in oncology. The severe dose-limiting side effects of chemotherapy necessitate the development of novel, efficient and tolerable therapy approaches. In this regard, the prostate specific membrane antigene (PSMA) has been well established as a molecular target for diagnosis of, as well as therapy for, prostate cancer. Although most PSMA-targeting ligands are radiopharmaceuticals used in imaging or radioligand therapy, this article evaluates a PSMA-targeting small molecule-drug conjugate, and, thus, addresses a hitherto little-explored field. PSMA binding affinity and cytotoxicity were determined in vitro using cell-based assays. Enzyme-specific cleavage of the active drug was quantified via an enzyme-based assay. Efficacy and tolerability in vivo were assessed using an LNCaP xenograft model. Histopathological characterization of the tumor in terms of apoptotic status and proliferation rate was carried out using caspase-3 and Ki67 staining. The binding affinity of the Monomethyl auristatin E (MMAE) conjugate was moderate, compared to the drug-free PSMA ligand. Cytotoxicity in vitro was in the nanomolar range. Both binding and cytotoxicity were found to be PSMA-specific. Additionally, complete MMAE release could be reached after incubation with cathepsin B. In vivo, the MMAE conjugate displayed good tolerability and dose-dependent inhibition of tumor growth. Immunohistochemical and histological studies revealed the antitumor effect of MMAE.VC.SA.617, resulting in the inhibition of proliferation and the enhancement of apoptosis. The developed MMAE conjugate showed good properties in vitro, as well as in vivo, and should, therefore, be considered a promising candidate for a translational approach.

Isolation of Nocuolin A and Synthesis of New Oxadiazine Derivatives. Design, Synthesis, Molecular Docking, Apoptotic Evaluation, and Cathepsin B Inhibition

Nocuolin A (1), an oxadiazine, was isolated from the cyanobacterium Nostoc sp. Its chemical structure was elucidated using NMR and mass spectroscopic data. From this compound, two new oxadiazines, 3-[(6R)-5,6-dihydro-4,6-dipentyl-2H-1,2,3-oxadiazin-2-yl]-3-oxopropyl acetate (2) and 4-{3-[(6R)-5,6-dihydro-4,6-dipentyl-2H-1,2,3-oxadiazin-2-yl]-3-oxopropoxy}-4-oxobutanoic acid (3), were synthesised. The chemical structures of these two compounds were elucidated by a combination of NMR and MS analysis. Compound 3 showed cytotoxicity against the ACHN (0.73 ± 0.10 μM) and Hepa-1c1c7 (0.91 ± 0.08 μM) tumour cell lines. Similarly, compound 3 significantly decreased cathepsin B activity in ACHN and Hepa-1c1c7 tumour cell lines at concentrations of 1.52 ± 0.13 nM and 1.76 ± 0.24 nM, respectively. In addition, compound 3 showed no in vivo toxicity in a murine model treated with a dose of 4 mg/kg body weight.

Development of a Peptide-Based Nano-Sized Cathepsin B Inhibitor for Anticancer Therapy

Numerous cathepsin B inhibitors have been developed and are under investigation as potential cancer treatments. They have been evaluated for their ability to inhibit cathepsin B activity and reduce tumor growth. However, they have shown critical limitations, including low anticancer efficacy and high toxicity, due to their low selectivity and delivery problems. In this study, we developed a novel peptide and drug conjugate (PDC)-based cathepsin B inhibitor using cathepsin-B-specific peptide (RR) and bile acid (BA). Interestingly, this RR and BA conjugate (RR–BA) was able to self-assemble in an aqueous solution, and as a result, it formed stable nanoparticles. The nano-sized RR–BA conjugate showed significant cathepsin B inhibitory effects and anticancer effects against mouse colorectal cancer (CT26) cells. Its therapeutic effect and low toxicity were also confirmed in CT26 tumor-bearing mice after intravenous injection. Therefore, based on these results, the RR–BA conjugate could be developed as an effective anticancer drug candidate for inhibiting cathepsin B in anticancer therapy.

Cathepsin protease expression in infiltrative soft tissue sarcomas: cathepsin-K correlates with infiltrative tumor growth and clinical outcomes

Cathepsin proteases, activated in the lysosomes, are upregulated in many cancers. Intraoperative detection systems of microscopic residual tumor using cathepsin-mediated release of fluorescent nanoparticles may guide surgical excisions to improve local control. We sought to define the genetic and proteomic expression of cathepsins and their clinicopathological correlates in myxofibrosarcoma and undifferentiated pleomorphic sarcoma (UPS)-soft tissue sarcomas with high rates of positive resection margins and local recurrence-and to establish a cellular justification for cathepsin-dependent systems to identify residual cancer in the resection bed. Real-time quantitative polymerase chain reaction analysis of 58 fresh-frozen tumor specimens revealed that 56 (97%) had elevated mRNA expression of ≥1 cathepsin, including cathepsin-B (79%), cathepsin-K (59%), cathepsin-L (71%), and -S (71%). Immunohistochemical analysis of these fresh-frozen specimens revealed that 98% of tumors were positive for one or more of cathepsin-B (85%), cathepsin-K (50%), cathepsin-L (63%), and -S (10%). Strong cathepsin-K expression was associated with greater risks of local recurrence (hazard ratio, 3.78; p = 0.044) and disease-specific mortality (hazard ratio, 3.70; p = 0.025). Immunohistochemical analysis of 33 formalin-fixed paraffin-embedded block samples revealed that 97% were positive for cathepsin-B (88%), cathepsin-K (76%), cathepsin-L (52%), or -S (52%) at the tumor periphery; cathepsin-K positivity correlated with a radiographic tail-like sign (p = 0.004) and microscopic infiltrative growth (p = 0.020). We conclude that cathepsins are broadly overexpressed in myxofibrosarcoma and UPS, and cathepsin-K may be an immunohistochemical marker of local infiltration and poorer prognosis that could be used to guide precision surgery.

Enzyme-Responsive Double-Locked Photodynamic Molecular Beacon for Targeted Photodynamic Anticancer Therapy

An advanced photodynamic molecular beacon (PMB) was designed and synthesized, in which a distyryl boron dipyrromethene (DSBDP)-based photosensitizer and a Black Hole Quencher 3 moiety were connected via two peptide segments containing the sequences PLGVR and GFLG, respectively, of a cyclic peptide. These two short peptide sequences are well-known substrates of matrix metalloproteinase-2 (MMP-2) and cathepsin B, respectively, both of which are overexpressed in a wide range of cancer cells either extracellularly (for MMP-2) or intracellularly (for cathepsin B). Owing to the efficient Förster resonance energy transfer between the two components, this PMB was fully quenched in the native form. Only upon interaction with both MMP-2 and cathepsin B, either in a buffer solution or in cancer cells, both of the segments were cleaved specifically, and the two components could be completely separated, thereby restoring the photodynamic activities of the DSBDP moiety. This PMB could also be activated in tumors, and it effectively suppressed the tumor growth in A549 tumor-bearing nude mice upon laser irradiation without causing notable side effects. In particular, it did not cause skin photosensitivity, which is a very common side effect of photodynamic therapy (PDT) using conventional "always-on" photosensitizers. The overall results showed that this "double-locked" PMB functioned as a biological AND logic gate that could only be unlocked by the coexistence of two tumor-associated enzymes, which could greatly enhance the tumor specificity in PDT.

Dipeptide-Derived Alkynes as Potent and Selective Irreversible Inhibitors of Cysteine Cathepsins

The potential of designing irreversible alkyne-based inhibitors of cysteine cathepsins by isoelectronic replacement in reversibly acting potent peptide nitriles was explored. The synthesis of the dipeptide alkynes was developed with special emphasis on stereochemically homogeneous products obtained in the Gilbert-Seyferth homologation for C≡C bond formation. Twenty-three dipeptide alkynes and 12 analogous nitriles were synthesized and investigated for their inhibition of cathepsins B, L, S, and K. Numerous combinations of residues at positions P1 and P2 as well as terminal acyl groups allowed for the derivation of extensive structure-activity relationships, which were rationalized by computational covalent docking for selected examples. The determined inactivation constants of the alkynes at the target enzymes span a range of >3 orders of magnitude (3-10 133 M^-1 s^-1). Notably, the selectivity profiles of alkynes do not necessarily reflect those of the nitriles. Inhibitory activity at the cellular level was demonstrated for selected compounds.

Conjugation of Short Oligopeptides to a Second-Generation Polyamidoamine Dendrimer Shows Antibacterial Activity

The growing evolution of bacterial resistance to antibiotics represents a global issue that not only impacts healthcare systems but also political and economic processes. This necessitates the development of novel antibacterial agents. Antimicrobial peptides have shown promise in this regard. Thus, in this study, a new functional polymer was synthesized by joining a short oligopeptide sequence (Phe-Lys-Phe-Leu, FKFL) to the surface of a second-generation polyamidoamine (G2 PAMAM) dendrimer as an antibacterial component. This method of synthesis proved simple and resulted in a high conjugation yield of the product FKFL-G2. To determine its antibacterial potential, FKFL-G2 was subsequently analyzed via mass spectrometry, a cytotoxicity assay, bacterial growth assay, colony-forming unit assay, membrane permeabilization assay, transmission electron microscopy, and biofilm formation assay. FKFL-G2 was found to exhibit low toxicity to noncancerous NIH3T3 cells. Additionally, FKFL-G2 had an antibacterial effect on Escherichia coli and Staphylococcus aureus strains by interacting with and disrupting the bacterial cell membrane. Based on these findings, FKFL-G2 shows promise as a potential antibacterial agent.

Tumor protease-activated theranostic nanoparticles for MRI-guided glioblastoma therapy

Rationale: As a cancer, Glioblastoma (GBM) is a highly lethal and difficult-to-treat. With the aim of improving therapies to GBM, we developed novel and target-specific theranostic nanoparticles (TNPs) that can be selectively cleaved by cathepsin B (Cat B) to release the potent toxin monomethyl auristatin E (MMAE). Methods: We synthesized TNPs composed of a ferumoxytol-based nanoparticle carrier and a peptide prodrug with a Cat-B-responsive linker and the tubulin inhibitor MMAE. We hypothesized that intratumoral Cat B can cleave our TNPs and release MMAE to kill GBM cells. The ferumoxytol core enables in vivo drug tracking with magnetic resonance imaging (MRI). We incubated U87-MG GBM cells with TNPs or ferumoxytol and evaluated the TNP content in the cells with transmission electron microscopy and Prussian blue staining. In addition, we stereotaxically implanted 6- to 8-week-old nude mice with U87-MG with U87-MG GBM cells that express a fusion protein of Green Fluorescence Protein and firefly Luciferase (U87-MG/GFP-fLuc). We then treated the animals with an intravenous dose of TNPs (25 mg/kg of ferumoxytol, 0.3 mg/kg of MMAE) or control. We also evaluated the combination of TNP treatment with radiation therapy. We performed MRI before and after TNP injection. We compared the results for tumor and normal brain tissue between the TNP and control groups. We also monitored tumor growth for a period of 21 days. Results: We successfully synthesized TNPs with a hydrodynamic size of 41 ± 5 nm and a zeta potential of 6 ± 3 mV. TNP-treated cells demonstrated a significantly higher iron content than ferumoxytol-treated cells (98 ± 1% vs. 3 ± 1% of cells were iron-positive, respectively). We also found significantly fewer live attached cells in the TNP-treated group (3.8 ± 2.0 px2) than in the ferumoxytol-treated group (80.0 ± 14.5 px2, p < 0001). In vivo MRI studies demonstrated a decline in the tumor signal after TNP (T2= 28 ms) but not control (T2= 32 ms) injections. When TNP injection was combined with radiation therapy, the tumor signals dropped further (T2 = 24 ms). The combination therapy of radiation therapy and TNPs extended the median survival from 14.5 days for the control group to 45 days for the combination therapy group. Conclusion: The new cleavable TNPs reported in this work accumulate in GBM, cause tumor cell death, and have synergistic effects with radiation therapy.

Rational Drug Design of Targeted and Enzyme-Cleavable Vitamin E Analogs as a Neoadjuvant to Chemotherapy: In Vitro and In Vivo Evaluation on Reduction of the Cardiotoxicity Side Effect of Doxorubicin

Traditional drug design focuses on specific biological targets where specific receptors or biomarkers are overexpressed by cancer cells. Cancer cells circumvent the interventions by activating survival pathways and/or downregulating cell death pathways for their survival. A priori activation of apoptosis pathways of tumor (AAAPT) is a novel tumor-sensitizing technology that sensitizes tumor cells that are not responding well to the current treatments by targeting specific survival pathways involved in the desensitization of tumor cells and tries to revive them selectively in cancer cells, sparing normal cells. Several vitamin E derivatives (AMP-001, AMP-002, AMP-003, and AMP-004) were synthesized, characterized, and studied for their anti-tumorigenic properties and their synergistic potential with the standard chemotherapy doxorubicin in various cancer cells including brain cancer stem cells in vitro. Preliminary studies revealed that AAAPT drugs (a) reduced the invasive potential of brain tumor stem cells, (b) synergized with Federal Drug Application-approved doxorubicin, and (c) enhanced the therapeutic index of doxorubicin in the triple-negative breast cancer tumor rat model, preserving the ventricular function compared to cardiotoxic doxorubicin alone at therapeutic dose. The AAAPT approach has the advantage of inhibiting survival pathways and activating cell death pathways selectively in cancer cells by using targeting, linkers cleavable by tumor-specific Cathepsin B, and PEGylation technology to enhance the bioavailability. We propose AAAPT drugs as a neoadjuvant to chemotherapy and not as stand-alone therapy, which is shown to be effective in expanding the therapeutic index of doxorubicin and making it work at lower doses.