Engineering a prostate-specific membrane antigen-activated tumor endothelial cell prodrug for cancer therapy

Nanotechnology and bioengineering approaches to improve the potency of mesenchymal stem cell as an off-the-shelf versatile tumor delivery vehicle

Targeting actionable mutations in oncogene-driven cancers and the evolution of immuno-oncology are the two prominent revolutions that have influenced cancer treatment paradigms and caused the emergence of precision oncology. However, intertumoral and intratumoral heterogeneity are the main challenges in both fields of precision cancer treatment. In other words, finding a universal marker or pathway in patients suffering from a particular type of cancer is challenging. Therefore, targeting a single hallmark or pathway with a single targeted therapeutic will not be efficient for fighting against tumor heterogeneity. Mesenchymal stem cells (MSCs) possess favorable characteristics for cellular therapy, including their hypoimmune nature, inherent tumor-tropism property, straightforward isolation, and multilineage differentiation potential. MSCs can be loaded with various chemotherapeutics and oncolytic viruses. The combination of these intrinsic features with the possibility of genetic manipulation makes them a versatile tumor delivery vehicle that can be used for in vivo selective tumor delivery of various chemotherapeutic and biological therapeutics. MSCs can be used as biofactory for the local production of chemical or biological anticancer agents at the tumor site. MSC-mediated immunotherapy could facilitate the sustained release of immunotherapeutic agents specifically at the tumor site, and allow for the achievement of therapeutic concentrations without the need for repetitive systemic administration of high therapeutic doses. Despite the enthusiasm evoked by preclinical studies that used MSC in various cancer therapy approaches, the translation of MSCs into clinical applications has faced serious challenges. This manuscript, with a critical viewpoint, reviewed the preclinical and clinical studies that have evaluated MSCs as a selective tumor delivery tool in various cancer therapy approaches, including gene therapy, immunotherapy, and chemotherapy. Then, the novel nanotechnology and bioengineering approaches that can improve the potency of MSC for tumor targeting and overcoming challenges related to their low localization at the tumor sites are discussed.

Engineering peptide drug therapeutics through chemical conjugation and implication in clinics

The development of peptide drugs has made tremendous progress in the past few decades because of the advancements in modification chemistry and analytical technologies. The novel-designed peptide drugs have been modified through various biochemical methods with improved diagnostic, therapeutic, and drug-delivery strategies. Researchers found it a helping hand to overcome the inherent limitations of peptides and bring continued advancements in their applications. Furthermore, the emergence of peptide-drug conjugates (PDCs)-utilizes target-oriented peptide moieties as a vehicle for cytotoxic payloads via conjugation with cleavable chemical agents, resulting in the key foundation of the new era of targeted peptide drugs. This review summarizes the various classifications of peptide drugs, suitable chemical modification strategies to improve the ADME (adsorption, distribution, metabolism, and excretion) features of peptide drugs, and recent (2015-early 2024) progress/achievements in peptide-based drug delivery systems as well as their fruitful implication in preclinical and clinical studies. Furthermore, we also summarized the brief description of other types of PDCs, including peptide-MOF conjugates and peptide-UCNP conjugates. The principal aim is to provide scattered and diversified knowledge in one place and to help researchers understand the pinching knots in the science of PDC development and progress toward a bright future of novel peptide drugs.

Hypoxia-activated XBP1s recruits HDAC2-EZH2 to engage epigenetic suppression of ΔNp63α expression and promote breast cancer metastasis independent of HIF1α

Hypoxia is a hallmark of cancer development. However, the molecular mechanisms by which hypoxia promotes tumor metastasis are not fully understood. In this study, we demonstrate that hypoxia promotes breast cancer metastasis through suppression of ΔNp63α in a HIF1α-independent manner. We show that hypoxia-activated XBP1s forms a stable repressor protein complex with HDAC2 and EZH2 to suppress ΔNp63α transcription. Notably, H3K27ac is predominantly occupied on the ΔNp63 promoter under normoxia, while H3K27me3 on the promoter under hypoxia. We show that XBP1s binds to the ΔNp63 promoter to recruit HDAC2 and EZH2 in facilitating the switch of H3K27ac to H3K27me3. Pharmacological inhibition or the knockdown of either HDAC2 or EZH2 leads to increased H3K27ac, accompanied by the reduced H3K27me3 and restoration of ΔNp63α expression suppressed by hypoxia, resulting in inhibition of cell migration. Furthermore, the pharmacological inhibition of IRE1α, but not HIF1α, upregulates ΔNp63α expression in vitro and inhibits tumor metastasis in vivo. Clinical analyses reveal that reduced p63 expression is correlated with the elevated expression of XBP1, HDAC2, or EZH2, and is associated with poor overall survival in human breast cancer patients. Together, these results indicate that hypoxia-activated XBP1s modulates the epigenetic program in suppression of ΔNp63α to promote breast cancer metastasis independent of HIF1α and provides a molecular basis for targeting the XBP1s/HDAC2/EZH2-ΔNp63α axis as a putative strategy in the treatment of breast cancer metastasis.

Nanotherapeutics for prostate cancer treatment: A comprehensive review

Prostate cancer (PCa) is the most prevalent solid organ malignancy and seriously affects male health. The adverse effects of prostate cancer therapeutics can cause secondary damage to patients. Nanotherapeutics, which have special targeting abilities and controlled therapeutic release profiles, may serve as alternative agents for PCa treatment. At present, many nanotherapeutics have been developed to treat PCa and have shown better treatment effects in animals than traditional therapeutics. Although PCa nanotherapeutics are highly attractive, few successful cases have been reported in clinical practice. To help researchers design valuable nanotherapeutics for PCa treatment and avoid useless efforts, herein, we first reviewed the strategies and challenges involved in prostate cancer treatment. Subsequently, we presented a comprehensive review of nanotherapeutics for PCa treatment, including their targeting methods, controlled release strategies, therapeutic approaches and mechanisms. Finally, we proposed the future prospects of nanotherapeutics for PCa treatment.

Peptide-Drug Conjugates: Design, Chemistry, and Drug Delivery System as a Novel Cancer Theranostic

The emergence of peptide-drug conjugates (PDCs) that utilize target-oriented peptide moieties as carriers of cytotoxic payloads, interconnected with various cleavable/noncleavable linkers, resulted in the key-foundation of the new era of targeted therapeutics. They are capable of retaining the integrity of conjugates in the blood circulatory system as well as releasing the drugs at the tumor microenvironment. Other valuable advantages are specificity and selectivity toward targeted-receptors, higher penetration ability, and drug-loading capacity, making them a suitable candidate to play their vital role as promising carrier agents. In this review, we summarized the types of cell-targeting (CTPs) and cell-penetrating peptides (CPPs) that have broad applications in the advancement of targeted drug-delivery systems (DDS). Moreover, the techniques to overcome the limitations of peptide-chemistry for their extensive implementation to construct the PDCs. Besides this, the diversified breakthrough of linker chemistry, and ample knowledge of various cytotoxic payloads used in PDCs in recent years, as well as the mechanism of action of PDCs was critically discussed. The principal aim is to provide scattered and diversified knowledge in one place and to help researchers understand the pinching knots in the science of PDC development, also their progression toward a bright future for PDCs as novel theranostics in clinical practice.

Peptide-Mediated Nanocarriers for Targeted Drug Delivery: Developments and Strategies

Effective drug delivery is essential for cancer treatment. Drug delivery systems, which can be tailored to targeted transport and integrated tumor therapy, are vital in improving the efficiency of cancer treatment. Peptides play a significant role in various biological and physiological functions and offer high design flexibility, excellent biocompatibility, adjustable morphology, and biodegradability, making them promising candidates for drug delivery. This paper reviews peptide-mediated drug delivery systems, focusing on self-assembled peptides and peptide-drug conjugates. It discusses the mechanisms and structural control of self-assembled peptides, the varieties and roles of peptide-drug conjugates, and strategies to augment peptide stability. The review concludes by addressing challenges and future directions.

STIM1 in tumor cell death: angel or devil?

Stromal interaction molecule 1 (STIM1) is involved in mediating the store-operated Ca2+ entry (SOCE), driving the influx of the intracellular second messenger calcium ion (Ca2+), which is closely associated with tumor cell proliferation, metastasis, apoptosis, autophagy, metabolism and immune processes. STIM1 is not only regulated at the transcriptional level by NF-κB and HIF-1, but also post-transcriptionally modified by miRNAs and degraded by ubiquitination. Recent studies have shown that STIM1 or Ca2+ signaling can regulate apoptosis, autophagy, pyroptosis, and ferroptosis in tumor cells and act discrepantly in different cancers. Furthermore, STIM1 contributes to resistance against antitumor therapy by influencing tumor cell death. Further investigation into the mechanisms through which STIM1 controls other forms of tumor cell death could aid in the discovery of novel therapeutic targets. Moreover, STIM1 has the ability to regulate immune cells within the tumor microenvironment. Here, we review the basic structure, function and regulation of STIM1, summarize the signaling pathways through which STIM1 regulates tumor cell death, and propose the prospects of antitumor therapy by targeting STIM1.

Calcium signalling pathways in prostate cancer initiation and progression

Cancer cells proliferate, differentiate and migrate by repurposing physiological signalling mechanisms. In particular, altered calcium signalling is emerging as one of the most widespread adaptations in cancer cells. Remodelling of calcium signalling promotes the development of several malignancies, including prostate cancer. Gene expression data from in vitro, in vivo and bioinformatics studies using patient samples and xenografts have shown considerable changes in the expression of various components of the calcium signalling toolkit during the development of prostate cancer. Moreover, preclinical and clinical evidence suggests that altered calcium signalling is a crucial component of the molecular re-programming that drives prostate cancer progression. Evidence points to calcium signalling re-modelling, commonly involving crosstalk between calcium and other cellular signalling pathways, underpinning the onset and temporal progression of this disease. Discrete alterations in calcium signalling have been implicated in hormone-sensitive, castration-resistant and aggressive variant forms of prostate cancer. Hence, modulation of calcium signals and downstream effector molecules is a plausible therapeutic strategy for both early and late stages of prostate cancer. Based on this premise, clinical trials have been undertaken to establish the feasibility of targeting calcium signalling specifically for prostate cancer.

New frontiers in the design and discovery of therapeutics that target calcium ion signaling: a novel approach in the fight against cancer

INTRODUCTION

The Ca2+ signaling toolkit is currently under investigation as a potential target for addressing the threat of cancer. A growing body of evidence suggests that calcium signaling plays a crucial role in promoting various aspects of cancer, including cell proliferation, progression, drug resistance, and migration-related activities. Consequently, focusing on these altered Ca2+ transporting proteins has emerged as a promising area of research for cancer treatment.

AREAS COVERED

This review highlights the existing research on the role of Ca2+-transporting proteins in cancer progression. It discusses the current studies evaluating Ca2+ channel/transporter/pump blockers, inhibitors, or regulators as potential anticancer drugs. Additionally, the review addresses specific gaps in our understanding of the field that may require further investigation.

EXPERT OPINION

Targeting specific Ca2+ signaling cascades could disrupt normal cellular activities, making cancer therapy complex and elusive. Therefore, there is a need for improvements in current Ca2+ signaling pathway focused medicines. While synthetic molecules and plant compounds show promise, they also come with certain limitations. Hence, exploring the framework of targeted drug delivery, structure-rationale-based designing, and repurposing potential drugs to target Ca2+ transporting proteins could potentially lead to a significant breakthrough in cancer treatment.

[177Lu]Lu-PSMA-617 theranostic probe for hepatocellular carcinoma imaging and therapy

PURPOSE

This study aimed to explore the feasibility of using [177Lu]Lu-prostate-specific membrane antigen (PSMA)-617 and [177Lu]Lu-Evans blue (EB)-PSMA-617 for in vivo radioligand therapy by single-dose administration in a PSMA-positive hepatocellular carcinoma (HCC) xenograft mouse model.

METHODS

[177Lu]Lu-PSMA-617 and [177Lu]Lu-EB-PSMA-617 were prepared, and labelling efficiency and radiochemical purity were determined. A HepG2 human HCC subcutaneous xenograft mouse model was established. After intravenous injection of [177Lu]Lu-PSMA-617 or [177Lu]Lu-EB-PSMA-617 (37 MBq) into the mouse model, single-photon emission computed tomography/computed tomography (SPECT/CT) was performed. Biodistribution studies were conducted to verify targeting specificity and pharmacokinetics. In the radioligand therapy study, mice were randomized into 4 groups: 37 MBq [177Lu]Lu-PSMA-617, 18.5 MBq [177Lu]Lu-PSMA-617, 7.4 MBq [177Lu]Lu-EB-PSMA-617, and saline (control). A single-dose administration was applied at the beginning of therapy studies. Tumor volume, body weight, and survival were monitored every 2 days. After the end of therapy, mice were euthanized. Tumors were then weighed, and systemic toxicity was evaluated via blood testing and histological examination of healthy organs.

RESULTS

[177Lu]Lu-PSMA-617 and [177Lu]Lu-EB-PSMA-617 were successfully prepared with high purity and stability. SPECT/CT and biodistribution showed that tumor uptake was higher and persisted longer for [177Lu]Lu-EB-PSMA-617 compared with [177Lu]Lu-PSMA-617. [177Lu]Lu-PSMA-617 was rapidly cleared from the blood, while [177Lu]Lu-EB-PSMA-617 persisted for significantly longer. In radioligand therapy studies, tumor growth was significantly suppressed in the 37 MBq [177Lu]Lu-PSMA-617, 18.5 MBq [177Lu]Lu-PSMA-617, and 7.4 MBq [177Lu]Lu-EB-PSMA-617 groups compared to the saline group. Median survival was 40, 44, 43, and 30 days, respectively. No healthy organ toxicity was observed in safety and tolerability evaluation.

CONCLUSIONS

Radioligand therapy using [177Lu]Lu-PSMA-617 and [177Lu]Lu-EB-PSMA-617 significantly suppressed tumor growth and prolonged survival time in PSMA-positive HCC xenograft mice without obvious toxicity. These radioligands appear promising for clinical use in humans, and future studies are warranted.

Update on PET Radiopharmaceuticals for Imaging Hepatocellular Carcinoma

Numerous positron emission tomography (PET) targets for detection and staging of hepatocellular cancer have been developed in recent years. Hepatocellular carcinomas (HCCs) are clinically and pathologically heterogeneous tumours with a high tendency to be aggressive and unresponsive to chemotherapy. Early detection is essential, and the need for an adequate imaging biomarker, which can overcome some of the limitations of conventional radiological imaging, is persistent. Flourine-18 (18F) flourodeoxyglucose (FDG), the most widely used PET radiopharmaceutical, has proven disappointing as a possible staple in the evaluation of HCC. This disappointment had led to experimentation with carious radiotracers, such as the choline derivatives, acetate, and prostate-specific membrane antigen, which appear to complement and/or enhance the role of FDG. In this study, we look at the various PET radiopharmaceuticals that have been used for imaging HCC and the particular pathways that they target in HCC and liver cancers.

Functional Imaging of Liver Cancer (FLIC): Study protocol of a phase 2 trial of 18F-DCFPyL PET/CT imaging for patients with hepatocellular carcinoma

Background

While prostate specific membrane antigen (PSMA) is overexpressed in high-grade prostate cancers, it is also expressed in tumor neovasculature and other malignancies, including hepatocellular carcinoma (HCC). Importantly, no functional imaging for HCC is clinically available, making diagnosis and surveillance following local therapies particularly challenging. 18F-DCFPyL binds with high affinity to PSMA yet clears rapidly from the blood pool. PET imaging with 18F-DCFPyL may represent a new tool for staging, surveillance and assessment of treatment response in HCC. The purpose of this Functional Imaging Liver Cancer (FLIC) trial is to assess the ability of 18F-DCFPyL-PET/CT to detect sites of HCC.

Methods

This is a phase II multi-site prospective imaging trial with a plan to enroll 50 subjects with suspected HCC on standard of care CT or MRI and eligible for standard local treatment. Participants will undergo a baseline 18F-DCFPyL-PET/CT, prior to therapy. Subjects will also be scanned with 18F-FDG-PET/CT within 2 weeks of 18F-DCFPyL-PET/CT. Participants will undergo histopathologic assessment and standard of care local treatment for HCC within a multidisciplinary team context. Participants with histopathologic confirmation of HCC and a positive baseline 18F-DCFPyL-PET/CT will undergo a post-treatment 18F-DCFPyL-PET/CT during the first routine follow-up, typically within 4–8 weeks. Subjects with negative baseline 18F-DCFPyL-PET/CT will not be re-scanned after treatment but will remain in follow-up. Participants will be followed for 5-years to assess for progression-free-survival. The primary endpoint is the positive predictive value of 18F-DCFPyL-PET for HCC as confirmed by histopathology. Secondary endpoints include comparison of 18F-DCFPyL-PET/CT with CT, MRI, and 18F-FDG-PET/CT, and evaluation of the value of 18F-DCFPyL-PET/CT in assessing treatment response following local treatment. Exploratory endpoints include next generation sequencing of tumors, and analysis of extracellular vesicles to identify biomarkers associated with response to therapy.

Discussion

This is a prospective imaging trial designed to evaluate whether PSMA-PET/CT imaging with 18F-DCFPyL can detect tumor sites, assess local treatment response in HCC patients, and to eventually determine whether PSMA-PET/CT could improve outcomes of patients with HCC receiving standard of care local therapy. Importantly, this trial may help determine whether PSMA-selective radiopharmaceutical therapies may be beneficial for patients with HCC.

Clinical trial registration

NIH IND#133631. Submission date: 04-07-2021. Safe-to-proceed letter issued by FDA: 05.07.2021. NIH IRB #00080. ClinicalTrials.gov Identifier NCT05009979. Date of Registry: 08-18-2021. Protocol version date: 01-07-2022.

The endoplasmic reticulum membrane protein Sec62 as potential therapeutic target in SEC62 overexpressing tumors

The human SEC62 gene is located on chromosome 3q, was characterized as a tumor driver gene and is found to be overexpressed in an ever-growing number of tumors, particularly those with 3q26 amplification. Where analyzed, SEC62 overexpression was associated with poor prognosis. Sec62 protein is a membrane protein of the endoplasmic reticulum (ER) and has functions in endoplasmic reticulum protein import, endoplasmic reticulum-phagy and -in cooperation with the cytosolic protein calmodulin- the maintenance of cellular calcium homeostasis. Various human tumors show SEC62 overexpression in immunohistochemistry and corresponding cell lines confirm this phenomenon in western blots and immunofluorescence. Furthermore, these tumor cells are characterized by increased stress tolerance and migratory as well as invasive potential, three hallmarks of cancer cells. Strikingly, plasmid-driven overexpression of SEC62 in non-SEC62 overexpressing cells introduces the same three hallmarks of cancer into the transfected cells. Depletion of Sec62 from either type of SEC62 overexpressing tumor cells by treatment with SEC62-targeting siRNAs leads to reduced stress tolerance and reduced migratory as well as invasive potential. Where tested, treatment of SEC62 overexpressing tumor cells with the small molecule/calmodulin antagonist trifluoperazine (TFP) phenocopied the effect of SEC62-targeting siRNAs. Recently, first phase II clinical trials with the prodrug mipsagargin/G202, which targets cellular calcium homeostasis in prostate cells as well as neovascular tissue in various tumors were started. According to experiments with tumor cell lines, however, SEC62 overexpressing tumor cells may be less responsive or resistant against such treatment. Therefore, murine tumor models for tumor growth or metastasis were evaluated with respect to their responsiveness to treatment with a mipsagargin analog (thapsigargin), or trifluoperazine, which had previously been in clinical use for the treatment of schizophrenia, or with the combination of both drugs. So far, no additive effect of the two drugs was observed but trifluoperazine had an inhibitory effect on tumor growth and metastatic potential in the models. Here, we review the state of affairs.

PET imaging of hepatocellular carcinoma by targeting tumor-associated endothelium using [68Ga]Ga-PSMA-617

OBJECTIVE

Hepatocellular carcinoma (HCC) is a malignant tumor associated with high morbidity and mortality rates. In many non-prostate solid tumors such as HCC, prostate-specific membrane antigens (PSMA) are overexpressed in tumor-associated endothelial cells. Therefore, the aim of this study was to evaluate the performance of [68Ga]Ga-PSMA-617 PET imaging on HCC with different animal models, including cell line-derived xenografts (CDX) and patient-derived xenografts (PDX), and to explore its mechanisms of function.

METHODS

[68Ga]Ga-PSMA-617 was prepared. The expression level of PSMA in two human hepatocellular cancer cells (HepG2 and HuH-7) was evaluated, and the cellular uptakes of [68Ga]Ga-PSMA-617 were assayed. HepG2 and HuH-7 subcutaneous xenograft models, HepG2 orthotopic xenograft models, and four different groups of PDX models were prepared. Preclinical pharmacokinetics and performance of [68Ga]Ga-PSMA-617 were evaluated in different types of HCC xenografts models using small animal PET and biodistribution studies.

RESULTS

Low PSMA expression level of HepG2 and HuH-7 cells was observed, and the cellular uptake and blocking study confirmed the non-specificity of the PSMA-targeted probe binding to HepG2 and HuH-7 cells. In the subcutaneous xenograft models, the tumor uptakes at 0.5 h were 0.76 ± 0.12%ID/g (HepG2 tumors) and 0.78 ± 0.08%ID/g (HuH-7 tumors), respectively, which were significantly higher than those of the blocking groups (0.23 ± 0.04%ID/g and 0.20 ± 0.04%ID/g, respectively). In the orthotopic xenograft models, PET images clearly displayed the tumor locations based on the preferential accumulation of [68Ga]Ga-PSMA-617 in tumor tissue versus normal liver tissue, suggesting the possibility of using [68Ga]Ga-PSMA-617 PET imaging to detect primary HCC lesions in deep tissue. In the four different groups of HCC PDX models, PET imaging with [68Ga]Ga-PSMA-617 provided clear tumor uptakes with prominent tumor-to-background contrast, further demonstrating its potential for the clinical imaging of PSMA-positive HCC lesions. The staining of tumor tissue sections with CD31- and PSMA-specific antibodies visualized the tumor-associated blood vessels and PSMA expression on endothelial cells in subcutaneous, orthotopic tissues, and PDX tissues, confirming the imaging with [68Ga]Ga-PSMA-617 might be mediated by targeting tumor associated endothelium.

CONCLUSION

In this study, in vivo PET on different types of HCC xenograft models illustrated high uptake within tumors, which confirmed that [68Ga]Ga-PSMA-617 PET may be a promising imaging modality for HCC by targeting tumor associated endothelium.

Role of the SEC62 gene in dermato-oncology - impact on tumor cell biology, prognostication, and personalized therapy management

The SEC62 gene encodes for a transmembrane protein of the endoplasmic reticulum (ER). Sec62 protein is involved in the post-translational transport of secretory and membrane-bound proteins in eukaryotic cells, regulates intracellular calcium homeostasis through direct interaction with the Sec61 channel and makes a decisive contribution to the cellular compensation of ER stress in the context of recovER-phagy. A significantly increased expression of the SEC62 gene has already been demonstrated in various tumor entities. First approaches of a targeted therapy have been tested for various tumor entities in vitro and in vivo with promising results that motivate further preclinical and clinical studies. Nevertheless, many questions remain unanswered, in particular with regard to the molecular mechanisms underlying the observed clinical effects, and require further investigation in future studies. The protein also plays a relevant role in dermato-oncology. The overexpression of SEC62 in atypical fibroxanthomas and malignant melanomas has already been demonstrated and a correlation of SEC62 expression with various clinical and pathological features has been observed. Future studies, especially in vivo and clinical, will show whether Sec62 can be established as a prognostic marker in dermato-oncology and whether it can serve as a starting point for targeted therapy.

Urothelial Carcinoma and Prostate-specific Membrane Antigen: Cellular, Imaging, and Prognostic Implications

CONTEXT

Staging, restaging, and surveillance of urothelial carcinoma (UC) is challenging due to suboptimal accuracy of standard of care imaging modalities. Prostate-specific membrane antigen (PSMA) imaging may serve to improve characterisation of UC.

OBJECTIVE

To appraise available literature regarding cellular, imaging, and prognostic implications of PSMA for UC.

EVIDENCE ACQUISITION

A systematic review was performed considering all available literature (including conference abstracts) published from 1990 to 2020 and reported according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines following registration in PROSPERO (CRD42020186744). All relevant texts relating to immunohistochemical analysis and PSMA-based imaging in UC were included and collated. Additionally, FOLH1 (gene encoding PSMA) expression according to The Cancer Genome Atlas (TCGA) database was analysed as well as according to consensus and TCGA molecular classification subtypes and subsequently compared with clinical outcomes.

EVIDENCE SYNTHESIS

PSMA expression across UC tumour tissue was heterogeneous (0-100%) but appeared to decrease with increased grade and stage. The TCGA analysis demonstrated loss of FOLH1 expression with increasing T stage (p = 0.0180) and N stage (p = 0.0269), and reduced FOLH1 expression was associated with worse disease-free survival. PSMA expression in UC neovasculature was variable but mostly increased (44-100%). Eleven reports of PSMA-based imaging for UC were identified, reporting on 18 patients. PSMA positron emission tomography (PET) imaging was positive in 17 out of 18 patients. The included literature review data were limited by mostly low-quality, retrospective studies.

CONCLUSIONS

Tissue PSMA, or FOLH1 expression, may inversely be associated with pathological and survival outcomes in localised UC. PSMA PET imaging may improve detection of metastatic disease and response to systemic therapy due to PSMA expression in neovasculature. Available evidence is limited; thus, larger, prospective studies are required to confirm early results and define populations that benefit most.

PATIENT SUMMARY

In this systematic review, we assess the potential role of prostate-specific membrane antigen in urothelial cancer. We found that its utility is in expression of blood vessels surrounding metastasis. We conclude that it may be beneficial in detecting metastasis and response to systemic therapies.

Antagonizing Sec62 function in intracellular Ca2+ homeostasis represents a novel therapeutic strategy for head and neck cancer

Various cancer types including head and neck squamous cell carcinomas (HNSCC) show a frequent amplification of chromosomal region 3q26 that encodes, among others, for the SEC62 gene. Located in the ER membrane, this translocation protein is known to play a critical role as a potential driver oncogene in cancer development. High SEC62 expression levels were observed in various cancer entities and were associated with a poor outcome and increased metastatic burden. Because of its intracellular localization the SEC62 protein is poorly accessible for therapeutic antibodies, therefore a functional SEC62 knockdown represents the most promising mechanism of a potential antineoplastic targeted therapy. By stimulating the Ca2+ efflux from the ER lumen and thereby increasing cellular stress levels, a functional inhibition of SEC62 bears the potential to limit tumor growth and metastasis formation. In this study, two potential anti-metastatic and -proliferative agents that counteract SEC62 function were investigated in functional in vitro assays by utilizing an immortalized human hypopharyngeal cancer cell line as well as a newly established orthotopic murine in vivo model. Additionally, a CRISPR/Cas9 based SEC62 knockout HNSCC cell line was generated and functionally characterized for its relevance in HNSCC cell proliferation and migration as well as sensitivity to SEC62 targeted therapy in vitro.

Macrophage-Encapsulated Bioorthogonal Nanozymes for Targeting Cancer Cells

Macrophages migrate to tumor sites by following chemoattractant gradients secreted by tumor cells, providing a truly active targeting strategy for cancer therapy. However, macrophage-based delivery faces challenges of cargo loading, control of release, and effects of the payload on the macrophage vehicle. We present a strategy that employs bioorthogonal "nanozymes" featuring transition metal catalysts (TMCs) to provide intracellular "factories" for the conversion of prodyes and prodrugs into imaging agents and chemotherapeutics. These nanozymes solubilize and stabilize the TMCs by embedding them into self-assembled monolayer coating gold nanoparticles. Nanozymes delivered into macrophages were intracellularly localized and retained activity even after prolonged (72 h) incubation. Significantly, nanozyme-loaded macrophages maintained their inherent migratory ability toward tumor cell chemoattractants, efficiently killing cancer cells in cocultures. This work establishes the potential of nanozyme-loaded macrophages for tumor site activation of prodrugs, providing readily tunable dosages and delivery rates while minimizing off-target toxicity of chemotherapeutics.

Anti-Inflammatory and Immunoregulatory Action of Sesquiterpene Lactones

Sesquiterpene lactones (SL), characterized by their high prevalence in the Asteraceae family, are one of the major groups of secondary metabolites found in plants. Researchers from distinct research fields, including pharmacology, medicine, and agriculture, are interested in their biological potential. With new SL discovered in the last years, new biological activities have been tested, different action mechanisms (synergistic and/or antagonistic effects), as well as molecular structure–activity relationships described. The review identifies the main sesquiterpene lactones with interconnections between immune responses and anti-inflammatory actions, within different cellular models as well in in vivo studies. Bioaccessibility and bioavailability, as well as molecular structure–activity relationships are addressed. Additionally, plant metabolic engineering, and the impact of sesquiterpene lactone extraction methodologies are presented, with the perspective of biological activity enhancement. Sesquiterpene lactones derivatives are also addressed. This review summarizes the current knowledge regarding the therapeutic potential of sesquiterpene lactones within immune and inflammatory activities, highlighting trends and opportunities for their pharmaceutical/clinical use.

Prostate-Specific Membrane Antigen and Esterase Dual Responsive Camptothecin-Oligopeptide Self-Assembled Nanoparticles for Efficient Anticancer Drug Delivery

Background

The clinical utility of camptothecin (CPT) is restricted by poor aqueous solubility, high lipophilicity, active lactone ring instability, and off-targeted toxicities. We report here a prostate-specific membrane antigen (PSMA) and esterase dual responsive self-assembled nanoparticles (CPT-WT-H NPs) for highly efficient CPT delivery and effective cancer therapy.

Methods and Results

In this study, smart self-assembled nanoparticles CPT-WT-H NPs were elaborately designed and synthesized by combing hydrophobic CPT with hydrophilic PSMA-responsive penta-peptide via a cleavable ester bond. This dual responsive nanoparticle with negatively charged surface first respond to the extracellular PSMA and then to the intracellular esterase, achieving a programmable release of CPT at the tumor site and producing the byproducts of biocompatible glutamic acid and aspartic acid. Our data demonstrated that CPT-WT-H NPs exhibited greatly improved water solubility and stability. Results from MTT and flow cytometry showed CPT-WT-H NPs exhibited significantly higher cytotoxicity as well as apoptosis-inducing activity against PSMA-expressing LNCaP-FGC cells than the non-PSMA-expressing cancer cells, showing excellent cytotoxic selectivity. Moreover, the unique nanostructure provided the efficient transportation of CPT to tumor site, which resulted in the effective inhibition of tumor growth and low systemic toxicity in vivo.

Conclusion

CPT-WT-H NPs exhibited excellent in vitro PSMA-response ability and in vivo antitumor activity and safety, holding the promise to become a new and potent anticancer drug. The current research presents a promising strategy for efficient drug delivery.

Mipsagargin: The Beginning-Not the End-of Thapsigargin Prodrug-Based Cancer Therapeutics

Søren Brøgger Christensen isolated and characterized the cell-penetrant sesquiterpene lactone Thapsigargin (TG) from the fruit Thapsia garganica. In the late 1980s/early 1990s, TG was supplied to multiple independent and collaborative groups. Using this TG, studies documented with a large variety of mammalian cell types that TG rapidly (i.e., within seconds to a minute) penetrates cells, resulting in an essentially irreversible binding and inhibiting (IC50~10 nM) of SERCA 2b calcium uptake pumps. If exposure to 50-100 nM TG is sustained for >24-48 h, prostate cancer cells undergo apoptotic death. TG-induced death requires changes in the cytoplasmic Ca2+, initiating a calmodulin/calcineurin/calpain-dependent signaling cascade that involves BAD-dependent opening of the mitochondrial permeability transition pore (MPTP); this releases cytochrome C into the cytoplasm, activating caspases and nucleases. Chemically unmodified TG has no therapeutic index and is poorly water soluble. A TG analog, in which the 8-acyl groups is replaced with the 12-aminododecanoyl group, afforded 12-ADT, retaining an EC50 for killing of <100 nM. Conjugation of 12-ADT to a series of 5-8 amino acid peptides was engineered so that they are efficiently hydrolyzed by only one of a series of proteases [e.g., KLK3 (also known as Prostate Specific Antigen); KLK2 (also known as hK2); Fibroblast Activation Protein Protease (FAP); or Folh1 (also known as Prostate Specific Membrane Antigen)]. The obtained conjugates have increased water solubility for systemic delivery in the blood and prevent cell penetrance and, thus, killing until the TG-prodrug is hydrolyzed by the targeting protease in the vicinity of the cancer cells. We summarize the preclinical validation of each of these TG-prodrugs with special attention to the PSMA TG-prodrug, Mipsagargin, which is in phase II clinical testing.

Theragnostics in primary and secondary liver tumors: the need for a personalized approach

Primary and secondary hepatic tumors have a dramatic impact in oncology. Despite many advances in diagnosis and therapy, the management of hepatic malignancies is still challenging, ranging from various loco-regional approaches to system therapies. In this scenario, theragnostic approaches, based on the administration of a radiopharmaceuticals' pair, the first labeled with a radionuclide suitable for the diagnostic phase and the second one bound to radionuclide emitting particles for therapy, is gaining more and more importance. Selective internal radiation therapy (SIRT) with microspheres labeled with ⁹⁰Y or ¹⁶⁶Ho is widely used as a loco-regional treatment for primary and secondary hepatic tumors. While ¹⁶⁶Ho presents both gamma and beta emission and can be therefore considered a real "theragnostic" agent, for ⁹⁰Y-microspheres theragnostic approach is realized at the diagnostic phase through the utilization of macroaggregates of human albumin, labeled with ^99mTc as "biosimilar" agent respect to microspheres. The aim of the present review was to cover theragnostic applications of ⁹⁰Y/¹⁶⁶Ho-labeled microspheres in clinical practice. Furthermore, we report the preliminary data concerning the potential role of some emerging theragnostic biomarkers for hepatocellular carcinoma, such as glypican-3 (GPC3) and prostate specific membrane antigen (PSMA).

A PSMA-targeted bispecific antibody for prostate cancer driven by a small-molecule targeting ligand

Despite the development of next-generation antiandrogens, metastatic castration-resistant prostate cancer (mCRPC) remains incurable. Here, we describe a unique semisynthetic bispecific antibody that uses site-specific unnatural amino acid conjugation to combine the potency of a T cell-recruiting anti-CD3 antibody with the specificity of an imaging ligand (DUPA) for prostate-specific membrane antigen. This format enabled optimization of structure and function to produce a candidate (CCW702) with specific, potent in vitro cytotoxicity and improved stability compared with a bispecific single-chain variable fragment format. In vivo, CCW702 eliminated C4-2 xenografts with as few as three weekly subcutaneous doses and prevented growth of PCSD1 patient-derived xenograft tumors in mice. In cynomolgus monkeys, CCW702 was well tolerated up to 34.1 mg/kg per dose, with near-complete subcutaneous bioavailability and a PK profile supporting testing of a weekly dosing regimen in patients. CCW702 is being evaluated in a first in-human clinical trial for men with mCRPC who had progressed on prior therapies (NCT04077021).

Source and exploration of the peptides used to construct peptide-drug conjugates

Peptide-drug conjugates (PDCs) are a class of novel molecules widely designed and synthesized for delivering payload drugs. The peptide part plays a vital role in the whole molecule, because they determine the ability of the molecules to penetrate the membrane and target to the specific targets. Here, we introduce the source of different kinds of cell-penetrating peptides (CPPs) and cell-targeting peptides (CTPs) that have been used or could be used in constructing PDCs as well as their latest application in delivering drugs. What's more, the approaches of developing CPPs and CTPs and the techniques to discover novel peptides are focused on and summarized in the review. This review aims to help relevant researchers fast understand the research status of peptides in PDCs and carry forward the process of novel peptides discovery.

Tumor-targeted CD28 bispecific antibodies enhance the antitumor efficacy of PD-1 immunotherapy

Monoclonal antibodies that block the programmed cell death 1 (PD-1) checkpoint have revolutionized cancer immunotherapy. However, many major tumor types remain unresponsive to anti-PD-1 therapy, and even among responsive tumor types, most of the patients do not develop durable antitumor immunity. It has been shown that bispecific antibodies activate T cells by cross-linking the TCR/CD3 complex with a tumor-specific antigen (TSA). The class of TSAxCD3 bispecific antibodies have generated exciting results in early clinical trials. We have recently described another class of "costimulatory bispecifics" that cross-link a TSA to CD28 (TSAxCD28) and cooperate with TSAxCD3 bispecifics. Here, we demonstrate that these TSAxCD28 bispecifics (one specific for prostate cancer and the other for epithelial tumors) can also synergize with the broader anti-PD-1 approach and endow responsiveness-as well as long-term immune memory-against tumors that otherwise do not respond to anti-PD-1 alone. Unlike CD28 superagonists, which broadly activate T cells and induce cytokine storm, TSAxCD28 bispecifics display little or no toxicity when used alone or in combination with a PD-1 blocker in genetically humanized immunocompetent mouse models or in primates and thus may provide a well-tolerated and "off the shelf" combination approach with PD-1 immunotherapy that can markedly enhance antitumor efficacy.

Mitochondrial Ca2+ Signaling in Health, Disease and Therapy

The divalent cation calcium (Ca²⁺) is considered one of the main second messengers inside cells and acts as the most prominent signal in a plethora of biological processes. Its homeostasis is guaranteed by an intricate and complex system of channels, pumps, and exchangers. In this context, by regulating cellular Ca²⁺ levels, mitochondria control both the uptake and release of Ca²⁺. Therefore, at the mitochondrial level, Ca²⁺ plays a dual role, participating in both vital physiological processes (ATP production and regulation of mitochondrial metabolism) and pathophysiological processes (cell death, cancer progression and metastasis). Hence, it is not surprising that alterations in mitochondrial Ca²⁺ (mCa²⁺) pathways or mutations in Ca²⁺ transporters affect the activities and functions of the entire cell. Indeed, it is widely recognized that dysregulation of mCa²⁺ signaling leads to various pathological scenarios, including cancer, neurological defects and cardiovascular diseases (CVDs). This review summarizes the current knowledge on the regulation of mCa²⁺ homeostasis, the related mechanisms and the significance of this regulation in physiology and human diseases. We also highlight strategies aimed at remedying mCa²⁺ dysregulation as promising therapeutical approaches.

More Than Meets the Eye: Scientific Rationale behind Molecular Imaging and Therapeutic Targeting of Prostate-Specific Membrane Antigen (PSMA) in Metastatic Prostate Cancer and Beyond

Simple Summary

Prostate-specific membrane antigen (PSMA) is a transmembrane protein that is overexpressed in prostate cancer and correlates with the aggressiveness of the disease. PSMA is a promising target for imaging and therapeutics in prostate cancer patients validated in prospective trials. However, the role of PSMA in prostate cancer progression is poorly understood. In this review, we discuss the biology and scientific rationale behind the use of PSMA and other targets in the detection and theranostics of metastatic prostate cancer.

Abstract

Prostate cancer is the second most common cancer type in men globally. Although the prognosis for localized prostate cancer is good, no curative treatments are available for metastatic disease. Better diagnostic methods could help target therapies and improve the outcome. Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein that is overexpressed on malignant prostate tumor cells and correlates with the aggressiveness of the disease. PSMA is a clinically validated target for positron emission tomography (PET) imaging-based diagnostics in prostate cancer, and during recent years several therapeutics have been developed based on PSMA expression and activity. The expression of PSMA in prostate cancer can be very heterogeneous and some metastases are negative for PSMA. Determinants that dictate clinical responses to PSMA-targeting therapeutics are not well known. Moreover, it is not clear how to manipulate PSMA expression for therapeutic purposes and develop rational treatment combinations. A deeper understanding of the biology behind the use of PSMA would help the development of theranostics with radiolabeled compounds and other PSMA-based therapeutic approaches. Along with PSMA several other targets have also been evaluated or are currently under investigation in preclinical or clinical settings in prostate cancer. Here we critically elaborate the biology and scientific rationale behind the use of PSMA and other targets in the detection and therapeutic targeting of metastatic prostate cancer.

Protein analysis of extracellular vesicles to monitor and predict therapeutic response in metastatic breast cancer

Molecular profiling of circulating extracellular vesicles (EVs) provides a promising noninvasive means to diagnose, monitor, and predict the course of metastatic breast cancer (MBC). However, the analysis of EV protein markers has been confounded by the presence of soluble protein counterparts in peripheral blood. Here we use a rapid, sensitive, and low-cost thermophoretic aptasensor (TAS) to profile cancer-associated protein profiles of plasma EVs without the interference of soluble proteins. We show that the EV signature (a weighted sum of eight EV protein markers) has a high accuracy (91.1 %) for discrimination of MBC, non-metastatic breast cancer (NMBC), and healthy donors (HD). For MBC patients undergoing therapies, the EV signature can accurately monitor the treatment response across the training, validation, and prospective cohorts, and serve as an independent prognostic factor for progression free survival in MBC patients. Together, this work highlights the potential clinical utility of EVs in management of MBC.

A thermophoretic aptasensor can be used to profile cancer-associated proteins of extracellular vesicles (EVs) in patients’ plasma. Here, the authors use this technique to develop an EV-signature able to discriminate metastatic breast cancer, monitor treatment response, and predict patients’ progression-free survival.

Autophagy and organelle homeostasis in cancer

Beginning with the earliest studies of autophagy in cancer, there have been indications that autophagy can both promote and inhibit cancer growth and progression; autophagy regulation of organelle homeostasis is similarly complicated. In this review we discuss pro- and antitumor effects of organelle-targeted autophagy and how this contributes to several hallmarks of cancer, such as evading cell death, genomic instability, and altered metabolism. Typically, the removal of damaged or dysfunctional organelles prevents tumor development but can also aid in proliferation or drug resistance in established tumors. By better understanding how organelle-specific autophagy takes place and can be manipulated, it may be possible to go beyond the brute-force approach of trying to manipulate all autophagy in order to improve therapeutic targeting of this process in cancer.

A prostate-specific membrane antigen (PSMA)-targeted prodrug with a favorable in vivo toxicity profile

Prostate-specific membrane antigen (PSMA) is a promising target for the treatment of advanced prostate cancer (PC) and various solid tumors. Although PSMA-targeted radiopharmaceutical therapy (RPT) has enabled significant imaging and prostate-specific antigen (PSA) responses, accumulating clinical data are beginning to reveal certain limitations, including a subgroup of non-responders, relapse, radiation-induced toxicity, and the need for specialized facilities for its administration. To date non-radioactive attempts to leverage PSMA to treat PC with antibodies, nanomedicines or cell-based therapies have met with modest success. We developed a non-radioactive prodrug, SBPD-1, composed of a small-molecule PSMA-targeting moiety, a cancer-selective cleavable linker, and the microtubule inhibitor monomethyl auristatin E (MMAE). SBPD-1 demonstrated high binding affinity to PSMA (K_i = 8.84 nM) and selective cytotoxicity to PSMA-expressing PC cell lines (IC₅₀ = 3.90 nM). SBPD-1 demonstrated a significant survival benefit in two murine models of human PC relative to controls. The highest dose tested did not induce toxicity in immunocompetent mice. The high specific targeting ability of SBPD-1 to PSMA-expressing tumors and its favorable toxicity profile warrant its further development.

Targeting Toxins toward Tumors

Many cancer diseases, e.g., prostate cancer and lung cancer, develop very slowly. Common chemotherapeutics like vincristine, vinblastine and taxol target cancer cells in their proliferating states. In slowly developing cancer diseases only a minor part of the malignant cells will be in a proliferative state, and consequently these drugs will exert a concomitant damage on rapidly proliferating benign tissue as well. A number of toxins possess an ability to kill cells in all states independently of whether they are benign or malignant. Such toxins can only be used as chemotherapeutics if they can be targeted selectively against the tumors. Examples of such toxins are mertansine, calicheamicins and thapsigargins, which all kill cells at low micromolar or nanomolar concentrations. Advanced prodrug concepts enabling targeting of these toxins to cancer tissue comprise antibody-directed enzyme prodrug therapy (ADEPT), gene-directed enzyme prodrug therapy (GDEPT), lectin-directed enzyme-activated prodrug therapy (LEAPT), and antibody-drug conjugated therapy (ADC), which will be discussed in the present review. The review also includes recent examples of protease-targeting chimera (PROTAC) for knockdown of receptors essential for development of tumors. In addition, targeting of toxins relying on tumor-overexpressed enzymes with unique substrate specificity will be mentioned.

Design of PSMA ligands with modifications at the inhibitor part: an approach to reduce the salivary gland uptake of radiolabeled PSMA inhibitors?

AIM

To investigate whether modifications of prostate-specific membrane antigen (PSMA)-targeted radiolabeled urea-based inhibitors could reduce salivary gland uptake and thus improve tumor-to-salivary gland ratios, several analogs of a high affinity PSMA ligand were synthesized and evaluated in in vitro and in vivo studies.

METHODS

Binding motifs were synthesized 'on-resin' or, when not practicable, in solution. Peptide chain elongations were performed according to optimized standard protocols via solid-phase peptide synthesis. In vitro experiments were performed using PSMA⁺ LNCaP cells. In vivo studies as well as μSPECT/CT scans were conducted with male LNCaP tumor xenograft-bearing CB17-SCID mice.

RESULTS

PSMA ligands with A) modifications within the central Zn²⁺-binding unit, B) proinhibitor motifs and C) substituents & bioisosteres of the P1'-γ-carboxylic acid were synthesized and evaluated. Modifications within the central Zn²⁺-binding unit of PSMA-10 (Glu-urea-Glu) provided three compounds. Thereof, only ^natLu-carbamate I (^natLu-3) exhibited high affinity (IC₅₀ = 7.1 ± 0.7 nM), but low tumor uptake (5.31 ± 0.94% ID/g, 1 h p.i. and 1.20 ± 0.55% ID/g, 24 h p.i.). All proinhibitor motif-based ligands (three in total) exhibited low binding affinities (> 1 μM), no notable internalization and very low tumor uptake (< 0.50% ID/g). In addition, four compounds with P1'-ɣ-carboxylate substituents were developed and evaluated. Thereof, only tetrazole derivative ^natLu-11 revealed high affinity (IC₅₀ = 16.4 ± 3.8 nM), but also this inhibitor showed low tumor uptake (3.40 ± 0.63% ID/g, 1 h p.i. and 0.68 ± 0.16% ID/g, 24 h p.i.). Salivary gland uptake in mice remained at an equally low level for all compounds (between 0.02 ± 0.00% ID/g and 0.09 ± 0.03% ID/g), wherefore apparent tumor-to-submandibular gland and tumor-to-parotid gland ratios for the modified peptides were distinctly lower (factor 8-45) than for [¹⁷⁷Lu]Lu-PSMA-10 at 24 h p.i.

CONCLUSIONS

The investigated compounds could not compete with the in vivo characteristics of the EuE-based PSMA inhibitor [¹⁷⁷Lu]Lu-PSMA-10. Although two derivatives (3 and 11) were found to exhibit high affinities towards LNCaP cells, tumor uptake at 24 h p.i. was considerably low, while uptake in salivary glands remained unaffected. Optimization of the established animal model should be envisaged to enable a clear identification of PSMA-targeting radioligands with improved tumor-to-salivary gland ratios in future studies.

Targeting oncogenic Notch signaling with SERCA inhibitors

P-type ATPase inhibitors are among the most successful and widely prescribed therapeutics in modern pharmacology. Clinical transition has been safely achieved for H+/K+ ATPase inhibitors such as omeprazole and Na+/K+-ATPase inhibitors like digoxin. However, this is more challenging for Ca2+-ATPase modulators due to the physiological role of Ca2+ in cardiac dynamics. Over the past two decades, sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) modulators have been studied as potential chemotherapy agents because of their Ca2+-mediated pan-cancer lethal effects. Instead, recent evidence suggests that SERCA inhibition suppresses oncogenic Notch1 signaling emerging as an alternative to γ-secretase modulators that showed limited clinical activity due to severe side effects. In this review, we focus on how SERCA inhibitors alter Notch1 signaling and show that Notch on-target-mediated antileukemia properties of these molecules can be achieved without causing overt Ca2+ cellular overload.

From Plant to Patient: Thapsigargin, a Tool for Understanding Natural Product Chemistry, Total Syntheses, Biosynthesis, Taxonomy, ATPases, Cell Death, and Drug Development

Thapsigargin, the first representative of the hexaoxygenated guaianolides, was isolated 40 years ago in order to understand the skin-irritant principles of the resin of the umbelliferous plant Thapsia garganica. The pronounced cytotoxicity of thapsigargin is caused by highly selective inhibition of the intracellular sarco-endoplasmic Ca²⁺-ATPase (SERCA) situated on the membrane of the endo- or sarcoplasmic reticulum. Thapsigargin is selective to the SERCA pump and to a minor extent the secretory pathway Ca²⁺/Mn²⁺ ATPase (SPCA) pump. Thapsigargin has become a tool for investigation of the importance of SERCA in intracellular calcium homeostasis. In addition, complex formation of thapsigargin with SERCA has enabled crystallization and structure determination of calcium-free states by X-ray crystallography. These results led to descriptions of the mechanism of action and kinetic properties of SERCA and other ATPases. Inhibition of SERCA depletes Ca²⁺ from the sarco- and endoplasmic reticulum provoking the unfolded protein response, and thereby has enabled new studies on the mechanism of cell death. Development of protocols for selective transformation of thapsigargin disclosed the chemistry and facilitated total synthesis of the molecule. Conversion of trilobolide into thapsigargin offered an economically feasible sustainable source of thapsigargin, which enables a future drug production. Principles for prodrug development were used by conjugating a payload derived from thapsigargin with a hydrophilic peptide selectively cleaved by proteases in the tumor. Mipsagargin was developed in order to obtain a drug for treatment of cancer diseases characterized by the presence of prostate specific membrane antigen (PSMA) in the neovascular tissue of the tumors. Even though mipsagargin showed interesting clinical effects the results did not encourage funding and consequently the attempt to register the drug has been abandoned. In spite of this disappointing fact, the research performed to develop the drug has resulted in important scientific discoveries concerning the chemistry, biosynthesis and biochemistry of sesquiterpene lactones, the mechanism of action of ATPases including SERCA, mechanisms for cell death caused by the unfolded protein response, and the use of prodrugs for cancer-targeting cytotoxins. The presence of toxins in only some species belonging to Thapsia also led to a major revision of the taxonomy of the genus.

Engineered drug-loaded cells and cell derivatives as a delivery platform for cancer immunotherapy

Recent advances in improving cancer immunotherapy have been summarized with a focus on using functionalized intact cells and cell derivatives.

Thapsigargin-From Traditional Medicine to Anticancer Drug

A sesquiterpene lactone, thapsigargin, is a phytochemical found in the roots and fruits of Mediterranean plants from Thapsia L. species that have been used for centuries in folk medicine to treat rheumatic pain, lung diseases, and female infertility. More recently thapsigargin was found to be a potent cytotoxin that induces apoptosis by inhibiting the sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase (SERCA) pump, which is necessary for cellular viability. This biological activity encouraged studies on the use of thapsigargin as a novel antineoplastic agent, which were, however, hampered due to high toxicity of this compound to normal cells. In this review, we summarized the recent knowledge on the biological activity and molecular mechanisms of thapsigargin action and advances in the synthesis of less-toxic thapsigargin derivatives that are being developed as novel anticancer drugs.

Large Scale Conversion of Trilobolide into the Payload of Mipsagargin: 8-O-(12-Aminododecanoyl)-8-O-Debutanoylthapsigargin

In spite of the impressing cytotoxicity of thapsigargin (Tg), this compound cannot be used as a chemotherapeutic drug because of general toxicity, causing unacceptable side effects. Instead, a prodrug targeted towards tumors, mipsagargin, was brought into clinical trials. What substantially reduces the clinical potential is the limited access to Tg and its derivatives and cost-inefficient syntheses with unacceptably low yields. Laser trilobum, which contains a structurally related sesquiterpene lactone, trilobolide (Tb), is successfully cultivated. Here, we report scalable isolation of Tb from L. trilobum and a transformation of Tb to 8-O-(12-aminododecanoyl)-8-O-debutanoylthapsigargin in seven steps. The use of cultivated L. trilobum offers an unlimited source of the active principle in mipsagargin.

Evolution of Pauson-Khand Reaction: Strategic Applications in Total Syntheses of Architecturally Complex Natural Products (2016–2020)

Metal-mediated cyclizations are important transformations in a natural product total synthesis. The Pauson-Khand reaction, particularly powerful for establishing cyclopentenone-containing structures, is distinguished as one of the most attractive annulation processes routinely employed in synthesis campaigns. This review covers Co, Rh, and Pd catalyzed Pauson-Khand reaction and summarizes its strategic applications in total syntheses of structurally complex natural products in the last five years. Additionally, the hetero-Pauson-Khand reaction in the synthesis of heterocycles will also be discussed. Focusing on the panorama of organic synthesis, this review highlights the strategically developed Pauson-Khand reaction in fulfilling total synthetic tasks and its synthetic attractiveness is aimed to be illustrated.

SJI 2020 special issue: A catalogue of Ovarian Cancer targets for CAR therapy

Ovarian Cancer (OC) is currently difficult to cure, mainly due to its late detection and the advanced state of the disease at the time of diagnosis. Therefore, conventional treatments such as debulking surgery and combination chemotherapy are rarely able to control progression of the tumour, and relapses are frequent. Alternative therapies are currently being evaluated, including immunotherapy and advanced T cell-based therapy. In the present review, we will focus on a description of those Chimeric Antigen Receptors (CARs) that have been validated in the laboratory or are being tested in the clinic. Numerous target antigens have been defined due to the identification of OC biomarkers, and many are being used as CAR targets. We provide an exhaustive list of these constructs and their current status. Despite being innovative and efficient, the OC-specific CARs face a barrier to their clinical efficacy: the tumour microenvironment (TME). Indeed, effector cells expressing CARs have been shown to be severely inhibited, rendering the CAR T cells useless once at the tumour site. Herein, we give a thorough description of the highly immunosuppressive OC TME and present recent studies and innovations that have enabled CAR T cells to counteract this negative environment and to destroy tumours.

Targeting Notch Trafficking and Processing in Cancers

The Notch family comprises a group of four ligand-dependent receptors that control evolutionarily conserved developmental and homeostatic processes and transmit signals to the microenvironment. NOTCH undergoes remodeling, maturation, and trafficking in a series of post-translational events, including glycosylation, ubiquitination, and endocytosis. The regulatory modifications occurring in the endoplasmic reticulum/Golgi precede the intramembrane γ-secretase proteolysis and the transfer of active NOTCH to the nucleus. Hence, NOTCH proteins coexist in different subcellular compartments and undergo continuous relocation. Various factors, including ion concentration, enzymatic activity, and co-regulatory elements control Notch trafficking. Interfering with these regulatory mechanisms represents an innovative therapeutic way to bar oncogenic Notch signaling. In this review, we briefly summarize the role of Notch signaling in cancer and describe the protein modifications required for NOTCH to relocate across different subcellular compartments. We focus on the functional relationship between these modifications and the corresponding therapeutic options, and our findings could support the development of trafficking modulators as a potential alternative to the well-known γ-secretase inhibitors.

Microparticle Encapsulation of a Prostate-targeted Biologic for the Treatment of Liver Metastases in a Preclinical Model of Castration-resistant Prostate Cancer

PRX302 is a highly potent, mutant bacterial pore-forming biologic protoxin engineered for selective activation by PSA, a serine protease expressed by benign and malignant prostate epithelial cells. Although being developed as a local therapy for benign prostatic hyperplasia and localized prostate cancer, PRX302 cannot be administered systemically as a treatment for metastatic disease due to binding to ubiquitously expressed glycosylphosphatidylinositol (GPI)-anchored proteins, which leads to poor accumulation within the tumor microenvironment. To overcome this limitation, poly-lactic-co-glycolic acid (PLGA) microparticles encapsulating the protoxin were developed, which are known to accumulate in the liver, a major site of metastasis for prostate cancer and other solid tumors. A highly sensitive and reproducible sandwich ELISA to quantify PRX302 released from microparticles was developed. Utilizing this assay, PRX302 release from different microparticle formulations was assessed over multiple days. Hemolysis assays documented PSA-dependent pore formation and lytic potential (i.e., function) of the released protoxin. MTT assays demonstrated that conditioned supernatant from PRX302-loaded, but not blank (i.e., unloaded), PLGA microparticles was highly cytotoxic to PC3 and DU145 human prostate cancer cells in the presence of exogenous PSA. Microparticle encapsulation prevented PRX302 from immediately interacting with GPI-anchored proteins as demonstrated in a competition assay, which resulted in an increased therapeutic index and significant antitumor efficacy following a single dose of PRX302-loaded microparticles in a preclinical model of prostate cancer liver metastasis with no obvious toxicity. These results document that PRX302 released from PLGA microparticles demonstrate in vivo antitumor efficacy in a clinically relevant preclinical model of metastatic prostate cancer.

Ca2+ Fluxes and Cancer

Ca²⁺ ions are key second messengers in both excitable and non-excitable cells. Owing to the rather pleiotropic nature of Ca²⁺ transporters and other Ca²⁺-binding proteins, however, Ca²⁺ signaling has attracted limited attention as a potential target of anticancer therapy. Here, we discuss cancer-associated alterations of Ca²⁺ fluxes at specific organelles as we identify novel candidates for the development of drugs that selectively target Ca²⁺ signaling in malignant cells.

Novel Therapeutic Approaches of Ion Channels and Transporters in Cancer

The expression and function of many ion channels and transporters in cancer cells display major differences in comparison to those from healthy cells. These differences provide the cancer cells with advantages for tumor development. Accordingly, targeting ion channels and transporters have beneficial anticancer effects including inhibition of cancer cell proliferation, migration, invasion, metastasis, tumor vascularization, and chemotherapy resistance, as well as promoting apoptosis. Some of the molecular mechanisms associating ion channels and transporters with cancer include the participation of oxidative stress, immune response, metabolic pathways, drug synergism, as well as noncanonical functions of ion channels. This diversity of mechanisms offers an exciting possibility to suggest novel and more effective therapeutic approaches to fight cancer. Here, we review and discuss most of the current knowledge suggesting novel therapeutic approaches for cancer therapy targeting ion channels and transporters. The role and regulation of ion channels and transporters in cancer provide a plethora of exceptional opportunities in drug design, as well as novel and promising therapeutic approaches that may be used for the benefit of cancer patients.

Co-targeting Mitochondrial Ca2+ Homeostasis and Autophagy Enhances Cancer Cells' Chemosensitivity

Mitochondria are important cell death checkpoints, and mitochondrial Ca²⁺ overload is considered as a potent apoptotic intrinsic pathway inducer. Here, we report that this Ca²⁺ apoptosis link is largely ineffective in inducing cell-death just by itself and required a concomitant inhibition of autophagy to counteract its pro-survival action. In such condition, an acute mitochondrial stress revealed by a DRP1-mediated mitochondrial dynamic remodeling is observed concomitantly with mitochondrial depolarization, release of cytochrome c, and efficient apoptosis induction. We also uncover that mitochondrial Ca²⁺ status modulates the function of autophagy as a sensitizer for chemotherapies. This priming mediated by mitochondrial Ca²⁺ overload and inhibition of autophagy sensitizes many cancer cells types to different chemotherapies with independent mechanisms of action. Collectively, our results redefine an important cell signaling pathway, uncovering new combined therapies for the treatment of diseases associated with mitochondrial Ca²⁺ homeostasis disorders such as cancer.

PERP-ing into diverse mechanisms of cancer pathogenesis: Regulation and role of the p53/p63 effector PERP

The tetraspan plasma membrane protein PERP (p53 apoptosis effector related to PMP22) is a lesser-known transcriptional target of p53 and p63. A member of the PMP22/GAS3/EMP membrane protein family, PERP was originally identified as a p53 target specifically trans-activated during apoptosis, but not during cell-cycle arrest. Several studies have since shown downregulation of PERP expression in numerous cancers, suggesting that PERP is a tumour suppressor protein. This review focusses on the important advances made in elucidating the mechanisms regulating PERP expression and its function as a tumour suppressor in diverse human cancers, including breast cancer and squamous cell carcinoma. Investigating PERP's role in clinically-aggressive uveal melanoma has revealed that PERP engages a positive-feedback loop with p53 to regulate its own expression, and that p63 is required beside p53 to achieve pro-apoptotic levels of PERP in this cancer. Furthermore, the recent discovery of the apoptosis-mediating interaction of PERP with SERCA2b at the plasma membrane-endoplasmic reticulum interface demonstrates a novel mechanism of PERP stabilisation, and how PERP can mediate Ca²⁺ signalling to facilitate apoptosis. The multi-faceted role of PERP in cancer, involving well-documented functions in mediating apoptosis and cell-cell adhesion is discussed, alongside PERP's emerging roles in epithelial-mesenchymal transition, and PERP crosstalk with inflammation signalling pathways, and other signalling pathways. The potential for restoring PERP expression as a means of cancer therapy is also considered.

From Orai to E-Cadherin: Subversion of Calcium Trafficking in Cancer to Drive Proliferation, Anoikis-Resistance, and Metastasis

The common currency of epithelial differentiation and homeostasis is calcium, stored primarily in the endoplasmic reticulum, rationed according to need, and replenished from the extracellular milieu via store-operated calcium entry (SOCE). This currency is disbursed by the IP3 receptor in response to diverse extracellular signals. The rate of release is governed by regulators of proliferation, autophagy, survival, and programmed cell death, the strength of the signal leading to different outcomes. Intracellular calcium acts chiefly through intermediates such as calmodulin that regulates growth factor receptors such as epidermal growth factor receptor (EGFR), actin polymerization, and adherens junction assembly and maintenance. Here we review this machinery and its role in differentiation, then consider how cancer cells subvert it to license proliferation, resist anoikis, and enable metastasis, either by modulating the level of intracellular calcium or its downstream targets or effectors such as EGFR, E-cadherin, IQGAP1, TMEM16A, CLCA2, and TRPA1. Implications are considered for the roles of E-cadherin and growth factor receptors in circulating tumor cells and metastasis. The discovery of novel, cell type-specific modulators and effectors of calcium signaling offers new possibilities for cancer chemotherapy.

Missing Selectivity of Targeted 4β-Phorbol Prodrugs Expected to be Potential Chemotherapeutics

Targeting cytotoxic 4β-phorbol esters toward cancer tissue was attempted by conjugating a 4β-pborbol derivative with substrates for the proteases prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) expressed in cancer tissue. The hydrophilic peptide moiety was hypothesized to prevent penetration of the prodrugs into cells and prevent interaction with PKC. Cleavage of the peptide in cancer tumors was envisioned to release lipophilic cytotoxins, which subsequently penetrate into cancer cells. The 4β-phorbol esters were prepared from 4β-phorbol isolated from Croton tiglium seeds, while the peptides were prepared by solid-phase synthesis. Cellular assays revealed activation of PKC by the prodrugs and efficient killing of both peptidase positive as well as peptidase negative cells. Consequently no selectivity for enzyme expressing cells was found.