Antitumor and antiangiogenic activity of the novel chimeric inhibitor animacroxam in testicular germ cell cancer

Mechanisms of cisplatin sensitivity and resistance in testicular germ cell tumors and potential therapeutic agents (Review)

Testicular germ cell tumors (TGCTs) are the most common tumors in men aged 20-40 years and are primarily treated with cisplatin-based drugs. Although TGCTs are highly sensitive to DNA damage induced by cisplatin and show a hypersensitive apoptotic response, cisplatin resistance still exists. Emerging evidence shows that cisplatin resistance in TGCTs is mainly related to the inhibition of apoptotic pathways such as MDM2/p53, OCT4/NOXA, PDGFR/PI3K/AKT, inhibition of cell cycle checkpoints, increased methylation or neddylation and DNA repair balance. In this review, recent advances regarding the mechanisms of TGCTs' sensitivity and resistance to cisplatin were summarized and potential therapeutic agents for cisplatin-resistant TGCTs were presented, providing a new therapeutic strategy for drug-resistant TGCTs.

The roles of enhancer, especially super-enhancer-driven genes in tumor metabolism and immunity

Abnormal metabolism is a characteristic of malignant tumors. Numerous factors play roles in the regulation of tumor metabolism. As epigenetic regulators, enhancers, especially the super-enhancers (SEs), serve as platforms for transcription factors that regulate the expression of metabolism-related enzymes or transporters at the gene level. In this study, we review the effects of enhancer/ SE-driven genes on tumor metabolism and immunity. Enhancers/SEs play regulatory roles in glucose metabolism (glycolysis, gluconeogenesis, tricarboxylic acid (TCA) cycle, pyruvate, and pentose phosphate pathway, lipid metabolism (cholesterol, fatty acid, phosphatide, and sphingolipid), and amino acid metabolism (glutamine, tryptophan, arginine, and cystine). By regulating tumor metabolism, enhancers and SEs can reprogram tumor microenvironment, especially the status of various immune cells. Therefore, interfering enhancers/SEs that regulate the tumor metabolism is likely to enhance the effectiveness of immunotherapy.

Quantitative accuracy of preclinical in ovo PET/MRI: influence of attenuation and quantification methods

AIM

The combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) provides an innovation leap in the use of fertilized chicken eggs (in ovo model) in preclinical imaging as PET/MRI enables the investigation of the chick embryonal organ-specific distribution of PET-tracers. However, hybrid PET/MRI inheres technical challenges in quantitative in ovo PET such as attenuation correction (AC) for the object as well as for additional hardware parts present in the PET field-of-view, which potentially contribute to quantification biases in the PET images if not accounted for. This study aimed to investigate the influence of the different sources of attenuation on in ovo PET/MRI and assess the accuracy of MR-based AC for in ovo experiments.

METHOD

An in-house made chicken egg phantom was used to investigate the magnitude of self-attenuation and the influence of the MRI hardware on the PET signal. The phantom was placed in a preclinical PET/MRI system and PET acquisitions were performed without, and after subsequently adding the different hardware parts to the setup. Reconstructions were performed without any AC for the different setups and with subsequently incorporating the hardware parts into the AC. In addition, in ovo imaging was performed using [18F]FDG and [68Ga]Ga-Pentixafor, and PET data was reconstructed with the different AC combinations. Quantitative accuracy was assessed for the phantom and the in ovo measurements.

RESULTS

In general, not accounting for the self-attenuation of the egg and the hardware parts caused an underestimation of the PET signal of around 49% within the egg. Accounting for all sources of attenuation allowed a proper quantification with global offsets of 2% from the true activity. Quantification based on % injected dose per cc (%ID/cc) was similar for the in ovo measurements, regardless of whether hardware parts were included in AC or not, when the injected activity was extracted from the PET images. However, substantial quantification biases were found when the self-attenuation of the egg was not taken into account.

CONCLUSION

Self-attenuation of the egg and PET signal attenuation within the hardware parts of the MRI substantially influence quantitative accuracy in in ovo measurements. However, when compensating for the self-attenuation of the egg by a respective AC, a reliable quantification using %ID/cc can be performed even if not accounting for the attenuation of the hardware parts.

Circulating tumor cells: from new biological insights to clinical practice

The primary reason for high mortality rates among cancer patients is metastasis, where tumor cells migrate through the bloodstream from the original site to other parts of the body. Recent advancements in technology have significantly enhanced our comprehension of the mechanisms behind the bloodborne spread of circulating tumor cells (CTCs). One critical process, DNA methylation, regulates gene expression and chromosome stability, thus maintaining dynamic equilibrium in the body. Global hypomethylation and locus-specific hypermethylation are examples of changes in DNA methylation patterns that are pivotal to carcinogenesis. This comprehensive review first provides an overview of the various processes that contribute to the formation of CTCs, including epithelial-mesenchymal transition (EMT), immune surveillance, and colonization. We then conduct an in-depth analysis of how modifications in DNA methylation within CTCs impact each of these critical stages during CTC dissemination. Furthermore, we explored potential clinical implications of changes in DNA methylation in CTCs for patients with cancer. By understanding these epigenetic modifications, we can gain insights into the metastatic process and identify new biomarkers for early detection, prognosis, and targeted therapies. This review aims to bridge the gap between basic research and clinical application, highlighting the significance of DNA methylation in the context of cancer metastasis and offering new avenues for improving patient outcomes.

Redirecting Tumor Evolution with Nanocompiler Precision for Enhanced Therapeutic Outcomes

Precisely programming the highly plastic tumor expression profile to render it devoid of drug resistance and metastatic potential presents immense challenges. Here, a transformative nanocompiler designed to reprogram and stabilize the mutable state of tumor cells is introduced. This nanocompiler features a trio of components: 2-deoxy-d-glucose-modified lipid nanoparticles to inhibit glucose uptake, iron oxide nanoparticles to induce oxidative stress, and a deubiquitinase inhibitor to block adaptive protein profile changes in tumor cells. By specifically targeting the hypermetabolic nature of tumors, this approach disrupted their energy production, ultimately fostering a state of vulnerability and impeding their ability to adapt and resist. The results of this study indicate a substantial reduction in tumor growth and metastasis, thus demonstrating the potential of this strategy to manipulate tumor protein expression and fate. This proactive nanocompiler approach promises to steer cancer therapy toward more effective and lasting outcomes.

In-ovo echocardiography for application in cardiovascular research

Preclinical cardiovascular research relies heavily on non-invasive in-vivo echocardiography in mice and rats to assess cardiac function and morphology, since the complex interaction of heart, circulation, and peripheral organs are challenging to mimic ex-vivo. While n-numbers of annually used laboratory animals worldwide approach 200 million, increasing efforts are made by basic scientists aiming to reduce animal numbers in cardiovascular research according to the 3R's principle. The chicken egg is well-established as a physiological correlate and model for angiogenesis research but has barely been used to assess cardiac (patho-) physiology. Here, we tested whether the established in-ovo system of incubated chicken eggs interfaced with commercially available small animal echocardiography would be a suitable alternative test system in experimental cardiology. To this end, we defined a workflow to assess cardiac function in 8-13-day-old chicken embryos using a commercially available high resolution ultrasound system for small animals (Vevo 3100, Fujifilm Visualsonics Inc.) equipped with a high frequency probe (MX700; centre transmit: 50 MHz). We provide detailed standard operating procedures for sample preparation, image acquisition, data analysis, reference values for left and right ventricular function and dimensions, and inter-observer variabilities. Finally, we challenged incubated chicken eggs with two interventions well-known to affect cardiac physiology-metoprolol treatment and hypoxic exposure-to demonstrate the sensitivity of in-ovo echocardiography. In conclusion, in-ovo echocardiography is a feasible alternative tool for basic cardiovascular research, which can easily be implemented into the small animal research environment using existing infrastructure to replace mice and rat experiments, and thus, reduce use of laboratory animals according to the 3R principle.

Breaking the Mold: Epigenetics and Genomics Approaches Addressing Novel Treatments and Chemoresponse in TGCT Patients

Testicular germ-cell tumors (TGCT) have been widely recognized for their outstanding survival rates, commonly attributed to their high sensitivity to cisplatin-based therapies. Despite this, a subset of patients develops cisplatin resistance, for whom additional therapeutic options are unsuccessful, and ~20% of them will die from disease progression at an early age. Several efforts have been made trying to find the molecular bases of cisplatin resistance. However, this phenomenon is still not fully understood, which has limited the development of efficient biomarkers and precision medicine approaches as an alternative that could improve the clinical outcomes of these patients. With the aim of providing an integrative landscape, we review the most recent genomic and epigenomic features attributed to chemoresponse in TGCT patients, highlighting how we can seek to combat cisplatin resistance through the same mechanisms by which TGCTs are particularly hypersensitive to therapy. In this regard, we explore ongoing treatment directions for resistant TGCT and novel targets to guide future clinical trials. Through our exploration of recent findings, we conclude that epidrugs are promising treatments that could help to restore cisplatin sensitivity in resistant tumors, shedding light on potential avenues for better prognosis for the benefit of the patients.

Epigenetic Regulation of Driver Genes in Testicular Tumorigenesis

In testicular germ cell tumor type II (TGCT), a seminoma subtype expresses an induced pluripotent stem cell (iPSC) panel with four upregulated genes, OCT4/POU5F1, SOX17, KLF4, and MYC, and embryonal carcinoma (EC) has four upregulated genes, OCT4/POU5F1, SOX2, LIN28, and NANOG. The EC panel can reprogram cells into iPSC, and both iPSC and EC can differentiate into teratoma. This review summarizes the literature on epigenetic regulation of the genes. Epigenetic mechanisms, such as methylations of cytosines on the DNA string and methylations and acetylations of histone 3 lysines, regulate expression of these driver genes between the TGCT subtypes. In TGCT, the driver genes contribute to well-known clinical characteristics and the driver genes are also important for aggressive subtypes of many other malignancies. In conclusion, epigenetic regulation of the driver genes are important for TGCT and for oncology in general.

CAM-Xenograft Model Provides Preclinical Evidence for the Applicability of [68Ga]Ga-Pentixafor in CRC Imaging

Colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Increased expression of CXCR4 has been associated with liver metastasis, disease progression, and shortened survival. Using in vitro cell binding studies and the in ovo model, we aimed to investigate the potential of [⁶⁸Ga]Ga-Pentixafor, a radiotracer specifically targeting human CXCR4, for CRC imaging. Specific membrane binding and internalisation of [⁶⁸Ga]Ga-Pentixafor was shown for HT29 cells, but not for HCT116 cells. Accordingly, [⁶⁸Ga]Ga-Pentixafor accumulated specifically in CAM-xenografts derived from HT29 cells, but not in HCT116 xenografts, as determined by µPET/MRI. The CAM-grown xenografts were histologically characterised, demonstrating vascularisation of the graft, preserved expression of human CXCR4, and viability of the tumour cells within the grafts. In vivo viability was further confirmed by µPET/MRI measurements using 2-[¹⁸F]FDG as a surrogate for glucose metabolism. [⁶⁸Ga]Ga-Pentixafor µPET/MRI scans showed distinct radiotracer accumulation in the chick embryonal heart, liver, and kidneys, whereas 2-[¹⁸F]FDG uptake was predominantly found in the kidneys and joints of the chick embryos. Our findings suggest that [⁶⁸Ga]Ga-Pentixafor is an interesting novel radiotracer for CRC imaging that is worth further investigation. Moreover, this study further supports the suitability of the CAM-xenograft model for the initial preclinical evaluation of targeted radiopharmaceuticals.

Epigenetics and Testicular Cancer: Bridging the Gap Between Fundamental Biology and Patient Care

Testicular cancer is the most common solid tumor affecting young males. Most testicular cancers are testicular germ cell tumors (TGCTs), which are divided into seminomas (SGCTs) and non-seminomatous testicular germ cell tumors (NSGCTs). During their development, primordial germ cells (PGCs) undergo epigenetic modifications and any disturbances in their pattern might lead to cancer development. The present study provides a comprehensive review of the epigenetic mechanisms–DNA methylation, histone post-translational modifications, bivalent marks, non-coding RNA–associated with TGCT susceptibility, initiation, progression and response to chemotherapy. Another important purpose of this review is to highlight the recent investigations regarding the identification and development of epigenetic biomarkers as powerful tools for the diagnostic, prognostic and especially for epigenetic-based therapy.

The component of the m6A writer complex VIRMA is implicated in aggressive tumor phenotype, DNA damage response and cisplatin resistance in germ cell tumors

Background

Germ cell tumors (GCTs) are developmental cancers, tightly linked to embryogenesis and germ cell development. The recent and expanding field of RNA modifications is being increasingly implicated in such molecular events, as well as in tumor progression and resistance to therapy, but still rarely explored in GCTs. In this work, and as a follow-up of our recent study on this topic in TGCT tissue samples, we aim to investigate the role of N6-methyladenosine (m⁶A), the most abundant of such modifications in mRNA, in in vitro and in vivo models representative of such tumors.

Methods

Four cell lines representative of GCTs (three testicular and one mediastinal), including an isogenic cisplatin resistant subline, were used. CRISPR/Cas9-mediated knockdown of VIRMA was established and the chorioallantoic membrane assay was used to study its phenotypic effect in vivo.

Results

We demonstrated the differential expression of the various m⁶A writers, readers and erasers in GCT cell lines representative of the major classes of these tumors, seminomas and non-seminomas, and we evidenced changes occurring upon differentiation with all-trans retinoic acid treatment. We showed differential expression also among cells sensitive and resistant to cisplatin treatment, implicating these players in acquisition of cisplatin resistant phenotype. Knockdown of VIRMA led to disruption of the remaining methyltransferase complex and decrease in m⁶A abundance, as well as overall reduced tumor aggressiveness (with decreased cell viability, tumor cell proliferation, migration, and invasion) and increased sensitivity to cisplatin treatment, both in vitro and confirmed in vivo. Enhanced response to cisplatin after VIRMA knockdown was related to significant increase in DNA damage (with higher γH2AX and GADD45B levels) and downregulation of XLF and MRE11.

Conclusions

VIRMA has an oncogenic role in GCTs confirming our previous tissue-based study and is further involved in response to cisplatin by interfering with DNA repair. These data contribute to our better understanding of the emergence of cisplatin resistance in GCTs and support recent attempts to therapeutically target elements of the m⁶A writer complex.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02072-9.

Comparison of Quantification of Target-Specific Accumulation of [18F]F-siPSMA-14 in the HET-CAM Model and in Mice Using PET/MRI

Simple Summary

Animal studies are essential for the development of new radiopharmaceuticals to determine specific accumulation and biodistribution. Alternative models, such as the HET-CAM model, offer the possibility of reducing animal experiments in accordance with the 3Rs principles. Accurate quantification of tumor accumulation of a PSMA-specific ligand in the HET-CAM model and comparison with corresponding animal experiments was performed using the imaging modalities PET and MRI. It was demonstrated that the HET-CAM model leads to comparable results and is suitable as an alternative to animal experiments for the initial assessment of target-specific binding of novel radiopharmaceuticals. However, as evaluation of biodistribution in ovo is still limited, further animal experiments with promising compounds are mandatory.

Abstract

Assessment of biodistribution and specific tumor accumulation is essential for the development of new radiopharmaceuticals and requires animal experiments. The HET-CAM (hens-egg test—chorioallantoic membrane) model can be used in combination with the non-invasive imaging modalities PET and MRI for pre-selection during radiopharmaceutical development to reduce the number of animal experiments required. Critical to the acceptance of this model is the demonstration of the quantifiability and reproducibility of these data compared to the standard animal model. Tumor accumulation and biodistribution of the PSMA-specific radiotracer [¹⁸F]F-siPSMA-14 was analyzed in the chick embryo and in an immunodeficient mouse model. Evaluation was based on MRI and PET data in both models. γ-counter measurements and histopathological analyses complemented these data. PSMA-specific accumulation of [¹⁸F]F-siPSMA-14 was successfully demonstrated in the HET-CAM model, similar to the results obtained by mouse model studies. The combination of MR and PET imaging allowed precise quantification of peptide accumulation, initial assessment of biodistribution, and accurate determination of tumor volume. Thus, the use of the HET-CAM model is suitable for the pre-selection of new radiopharmaceuticals and potentially reduces animal testing in line with the 3Rs principles of animal welfare.

Anticancer Activity and Mechanisms of Action of New Chimeric EGFR/HDAC-Inhibitors

New chimeric inhibitors targeting the epidermal growth factor (EGFR) and histone deacetylases (HDACs) were synthesized and tested for antineoplastic efficiency in solid cancer (prostate and hepatocellular carcinoma) and leukemia/lymphoma cell models. The most promising compounds, 3BrQuin-SAHA and 3ClQuin-SAHA, showed strong inhibition of tumor cell growth at one-digit micromolar concentrations with IC₅₀ values similar to or lower than those of clinically established reference compounds SAHA and gefitinib. Target-specific EGFR and HDAC inhibition was demonstrated in cell-free kinase assays and Western blot analyses, while unspecific cytotoxic effects could not be observed in LDH release measurements. Proapoptotic formation of reactive oxygen species and caspase-3 activity induction in PCa and HCC cell lines DU145 and Hep-G2 seem to be further aspects of the modes of action. Antiangiogenic potency was recognized after applying the chimeric inhibitors on strongly vascularized chorioallantoic membranes of fertilized chicken eggs (CAM assay). The novel combination of two drug pharmacophores against the EGFR and HDACs in one single molecule was shown to have pronounced antineoplastic effects on tumor growth in both solid and leukemia/lymphoma cell models. The promising results merit further investigations to further decipher the underlying modes of action of the novel chimeric inhibitors and their suitability for new clinical approaches in tumor treatment.

Radionuclide, magnetic resonance and computed tomography imaging in European round back slugs (Arionidae) and leopard slugs (Limacidae)

Other than in animal models of human disease, little functional imaging has been performed in most of the animal world. The aim of this study was to explore the functional anatomy of the European round back slug (Arionidae) and leopard slug (Limacidae) and to establish an imaging protocol for comparative species study. Radionuclide images with single photon emission computed tomography (SPECT) and positron emission tomography (PET) were obtained after injections of standard clinical radiopharmaceuticals ^99mtechnetium dicarboxypropane diphosphonate (bone scintigraphy), ^99mtechnetium mercaptoacetyltriglycine (kidney function), ^99mtechnetium diethylenetriaminepentaacetic acid (kidney function), ^99mtechnetium pertechnetate (mediated by the sodium-iodide symporter), ^99mtechnetium sestamibi (cardiac scintigraphy) or ¹⁸F-fluoro-deoxyglucose (glucose metabolism) in combination with magnetic resonance imaging (MRI) and computed tomography (CT) for uptake anatomic definition. Images were compared with anatomic drawings for the Arionidae species. Additionally, organ uptake data was determined for a description of slug functional anatomy in comparison to human tracer biodistribution patterns identifying the heart, the open circulatory anatomy, calcified shell remnant, renal structure (nephridium), liver (digestive gland) and intestine. The results show the detailed functional anatomy of Arionidae and Limacidae, and describe an in vivo whole-body imaging procedure for invertebrate species.

The chorioallantoic membrane as a bio-barrier model for the evaluation of nanoscale drug delivery systems for tumour therapy

In 2010, the European Parliament and the European Union adopted a directive on the protection of animals used for scientific purposes. The directive aims to protect animals in scientific research, with the final goal of complete replacement of procedures on live animals for scientific and educational purposes as soon as it is scientifically viable. Furthermore, the directive announces the implementation of the 3Rs principle: "When choosing methods, the principles of replacement, reduction and refinement should be implemented through a strict hierarchy of the requirement to use alternative methods." The visibility, accessibility, and the rapid growth of the chorioallantoic membrane (CAM) offers a clear advantage for various manipulations and for the simulation of different Bio-Barriers according to the 3R principle. The extensive vascularisation on the CAM provides an excellent substrate for the cultivation of tumour cells or tumour xenografts which could be used for the therapeutic evaluation of nanoscale drug delivery systems. The tumour can be targeted either by topical application, intratumoural injection or i.v. injection. Different application sites and biological barriers can be examined within a single model.

Achievement in active agent structures as a power tools in tumor angiogenesis imaging

According to World Health Organization (WHO) cancer is the second most important cause of death globally. Because angiogenesis is considered as an essential process of growth, proliferation and tumor progression, within this review we decided to shade light on recent development of chemical compounds which play a significant role in its imaging and monitoring. Indeed, the review gives insight about the current achievements of active agents structures involved in imaging techniques such as: positron emission computed tomography (PET), magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT), as well as combination PET/MRI and PET/CT. The review aims to provide the journal audience with a comprehensive and in-deep understanding of chemistry policy in tumor angiogenesis imaging.

Anticancer properties of chimeric HDAC and kinase inhibitors

Histone deacetylases (HDACs) are epigenetic regulators of chromatin condensation and decondensation and exert effects on the proliferation and spread of cancer. Thus, HDAC enzymes are promising drug targets for the treatment of cancer. Some HDAC inhibitors such as the hydroxamic acid derivatives vorinostat or panobinostat were already approved for the treatment of hematologic cancer diseases, and are under intensive investigation for their use in solid tumors. But there are also drawbacks of the clinical application of HDAC inhibitors like intrinsic or acquired drug resistance and, thus, new HDAC inhibitors with improved activities are sought for. Kinase inhibitors are very promising anticancer drugs and often showed synergistic anticancer effects in combination with HDAC inhibitors. Several hybrid molecules with HDAC and kinase inhibitory structural motifs were disclosed with even improved anticancer activities when compared with co-application of HDAC and receptor tyrosine kinase inhibitors. Chimeric inhibitors with HDAC inhibitory activities exert a rapidly growing field of research and only in this year several new dual HDAC/kinase inhibitors were disclosed. This review briefly summarizes the status and future perspective of the most advanced and promising dual HDAC/kinase inhibitors and their potential as anticancer drug candidates.

Multi-Modal PET and MR Imaging in the Hen's Egg Test-Chorioallantoic Membrane (HET-CAM) Model for Initial in Vivo Testing of Target-Specific Radioligands

The validation of novel target-specific radioligands requires animal experiments mostly using mice with xenografts. A pre-selection based on a simpler in vivo model would allow to reduce the number of animal experiments, in accordance with the 3Rs principles (reduction, replacement, refinement). In this respect, the chick embryo or hen’s egg test–chorioallantoic membrane (HET-CAM) model is of special interest, as it is not considered an animal until day 17. Thus, we evaluated the feasibility of quantitative analysis of target-specific radiotracer accumulation in xenografts using the HET-CAM model and combined positron emission tomography (PET) and magnetic resonance imaging (MRI). For proof-of-principle we used established prostate-specific membrane antigen (PSMA)-positive and PSMA-negative prostate cancer xenografts and the clinically widely used PSMA-specific PET-tracer [⁶⁸Ga]Ga-PSMA-11. Tracer accumulation was quantified by PET and tumor volumes measured with MRI (n = 42). Moreover, gamma-counter analysis of radiotracer accumulation was done ex-vivo. A three- to five-fold higher ligand accumulation in the PSMA-positive tumors compared to the PSMA-negative tumors was demonstrated. This proof-of-principle study shows the general feasibility of the HET-CAM xenograft model for target-specific imaging with PET and MRI. The ultimate value for characterization of novel target-specific radioligands now has to be validated in comparison to mouse xenograft experiments.