Assessing the Effectiveness of a Far-Red Fluorescent Reporter for Tracking Stem Cells In Vivo

Novel role of microphthalmia-associated transcription factor in modulating the differentiation and immunosuppressive functions of myeloid-derived suppressor cells

BACKGROUND

Microphthalmia-associated transcription factor (MITF) is a master regulator of melanogenesis and is mainly expressed in melanoma cells. MITF has also been reported to be expressed in non-pigmented cells, such as osteoclasts, mast cells, and B cells. However, the roles of MITF in immunosuppressive myeloid cells, including myeloid-derived suppressor cells (MDSCs), remain unclear. Here, we investigated the role of MITF in the differentiation process of MDSCs during tumor development.

METHODS

In vitro-generated murine MDSCs and primary MDSCs from breast cancer-bearing mice or lung carcinoma-bearing mice were used to determine the expression level of MITF and the activity of MDSCs. Additionally, we investigated whether in vivo tumor growth can be differentially regulated by coinjection of MDSCs in which MITF expression is modulated by small molecules. Furthermore, the number of MITF⁺ monocytic (MO)-MDSCs was examined in human tumor tissues or tumor-free lymph nodes by immunohistochemistry (IHC).

RESULTS

The expression of MITF was strongly increased in MO-MDSCs from tumors of breast cancer-bearing mice compared with polymorphonuclear MDSCs. We found that MITF expression in MDSCs was markedly induced in the tumor microenvironment (TME) and related to the functional activity of MDSCs. MITF overexpression in myeloid cells increased the expression of MDSC activity markers and effectively inhibited T-cell proliferation compared with those of control MDSCs, whereas shRNA-mediated knockdown of MITF in myeloid cells altered the immunosuppressive function of MDSCs. Modulation of MITF expression by small molecules affected the differentiation and immunosuppressive function of MDSCs. While increased MITF expression in MDSCs promoted breast cancer progression and CD4⁺ or CD8⁺ T-cell dysfunction, decreased MITF expression in MDSCs suppressed tumor progression and enhanced T-cell activation. Furthermore, IHC staining of human tumor tissues revealed that MITF⁺ MO-MDSCs are more frequently observed in tumor tissues than in tumor-free draining lymph nodes obtained from patients with cancer.

CONCLUSIONS

Our results indicate that MITF regulates the differentiation and function of MDSCs and can be a novel therapeutic target for modulating MDSC activity in immunosuppressive s.

Metformin in pregnancy and risk of abnormal growth outcomes at birth: a register-based cohort study

We previously reported an increased risk of being small for gestational age (SGA) and a decreased risk of being large for gestational age (LGA) after in utero exposure to metformin compared with insulin exposure. This follow-up study investigated if these observations remain when metformin exposure (henceforth, metformin cohort) is compared with non-pharmacological antidiabetic treatment of gestational diabetes mellitus (GDM; naïve cohort), instead of insulin. RESEARCH DESIGN AND METHODS : This was a Finnish population register-based cohort study from singleton children born during 2004-2016. Birth outcomes from metformin cohort (n=3964) and the naïve cohort (n=82 675) were used in the main analyses. Additional analyses were conducted in a subcohort, restricting the metformin cohort to children of mothers with GDM only (n=2361). Results were reported as inverse probability of treatment weighted OR (wOR), with the naïve cohort as reference. RESULTS  : No difference was found for the outcome of SGA between the cohorts in the main analyses (wOR 0.97, 95% CI 0.73 to 1.27) or in the additional analyses (wOR 1.01, 95% CI 0.75 to 1.37). No difference between the cohorts was found for the risk of LGA (wOR 0.91, 95% CI 0.75 to 1.11) in the main analyses but a decreased risk was observed in the additional analyses (wOR 0.72, 95% CI 0.56 to 0.92). CONCLUSIONS : This follow-up study found no increase in the risk of SGA or LGA after in utero exposure to metformin, compared with drug-naïve GDM. The decreased risk of LGA in mothers with GDM may suggest residual confounding. The lack of increased SGA risk aligns with findings from studies using metformin in non-diabetic pregnancies. In contrast, lower birth weight and increased SGA birth risk were observed in GDM pregnancies for metformin versus insulin. Metformin should be avoided with emerging growth restriction in utero. The interplay of intrauterine hyperglycemia and pharmacological treatments needs further assessment.

Characterization of Cytosolic Glutathione S-Transferases Involved in the Metabolism of the Aromatase Inhibitor, Exemestane

Exemestane (EXE) is a hormonal therapy used to treat estrogen receptor-positive breast cancer by inhibiting the final step of estrogen biosynthesis catalyzed by the enzyme aromatase. Cysteine conjugates of EXE and its active metabolite 17β-dihydro-EXE (DHE) are the major metabolites found in both the urine and plasma of patients taking EXE. The initial step in cysteine conjugate formation is glutathione conjugation catalyzed by the glutathione S-transferase (GST) family of enzymes. The goal of the present study was to identify cytosolic hepatic GSTs active in the GST-mediated metabolism of EXE and 17β-DHE. Twelve recombinant cytosolic hepatic GSTs were screened for their activity against EXE and 17β-DHE, and glutathionylated EXE and 17β-DHE conjugates were detected by ultra-performance liquid chromatography tandem mass spectrometry. GST α (GSTA) isoform 1, GST μ (GSTM) isoform 3 and isoform 1 were active against EXE, whereas only GSTA1 exhibited activity against 17β-DHE. GSTM1 exhibited the highest affinity against EXE with a Michaelis-Menten constant (KM) value that was 3.8- and 7.1-fold lower than that observed for GSTA1 and GSTM3, respectively. Of the three GSTs, GSTM3 exhibited the highest intrinsic clearance against EXE (intrinsic clearance = 0.14 nl·min-1·mg-1). The KM values observed for human liver cytosol against EXE (46 μM) and 17β-DHE (77 μM) were similar to those observed for recombinant GSTA1 (53 and 30 μM, respectively). Western blot analysis revealed that GSTA1 and GSTM1 composed 4.3% and 0.57%, respectively, of total protein in human liver cytosol; GSTM3 was not detected. These data suggest that GSTA1 is the major hepatic cytosolic enzyme involved in the clearance of EXE and its major active metabolite, 17β-DHE. SIGNIFICANCE STATEMENT: Most previous studies related to the metabolism of the aromatase inhibitor exemestane (EXE) have focused mainly on phase I metabolic pathways and the glucuronidation phase II metabolic pathway. However, recent studies have indicated that glutathionylation is the major metabolic pathway for EXE. The present study is the first to characterize hepatic glutathione S-transferase (GST) activity against EXE and 17β-dihydro-EXE and to identify GST α 1 and GST μ 1 as the major cytosolic GSTs involved in the hepatic metabolism of EXE.

Role of extracellular vesicle derived biomarkers in drug metabolism and disposition

Extracellular vesicles (EVs) are small, non-replicating, lipid encapsulated particles that contain a myriad of protein and nucleic acid cargo derived from their tissue of origin. The potential role of EV derived biomarkers to the study of drug metabolism and disposition (DMD) has gained attention in recent years. The key trait that makes EVs an attractive biomarker source is their capacity to provide comparable insights to solid organ biopsy through an appreciably less invasive collection procedure. Blood-derived EVs exist as a heterogenous milieu of biologically distinct particles originating from different sources through different biogenesis pathways. Furthermore, blood (plasma and serum) contains an array of vesicular and non-vesicular contaminants such as apoptotic bodies, plasma proteins and lipoproteins that are routinely co-isolated with EVs albeit to a different extent depending on the isolation technique. The following mini-review summarises current studies reporting DMD biomarkers and addresses elements of EV isolation and quantification relevant to the application of EV derived DMD biomarkers. Evidence based best practice guidance aligned to Minimum Information for the Study of Extracellular Vesicles (MISEV) and EV Track reporting standards are summarised in the context of DMD studies. Significance Statement Extracellular vesicle (EV) derived protein and nucleic acid cargo represent a potentially game changing source of novel DMD biomarkers with the capacity to define within- and between- individual variability in drug exposure irrespective of aetiology. However, robust translation of EV-derived biomarkers requires the generation of transparent reproducible evidence. This review outlines the critical elements of data generation and reporting relevant to achieving this evidence in a drug metabolism and disposition context.

Bioinformatic analysis of RHO family of GTPases identifies RAC1 pharmacological inhibition as a new therapeutic strategy for hepatocellular carcinoma

OBJECTIVE

The RHO family of GTPases, particularly RAC1, has been linked with hepatocarcinogenesis, suggesting that their inhibition might be a rational therapeutic approach. We aimed to identify and target deregulated RHO family members in human hepatocellular carcinoma (HCC).

DESIGN

We studied expression deregulation, clinical prognosis and transcription programmes relevant to HCC using public datasets. The therapeutic potential of RAC1 inhibitors in HCC was study in vitro and in vivo. RNA-Seq analysis and their correlation with the three different HCC datasets were used to characterise the underlying mechanism on RAC1 inhibition. The therapeutic effect of RAC1 inhibition on liver fibrosis was evaluated.

RESULTS

Among the RHO family of GTPases we observed that RAC1 is upregulated, correlates with poor patient survival, and is strongly linked with a prooncogenic transcriptional programme. From a panel of novel RAC1 inhibitors studied, 1D-142 was able to induce apoptosis and cell cycle arrest in HCC cells, displaying a stronger effect in highly proliferative cells. Partial rescue of the RAC1-related oncogenic transcriptional programme was obtained on RAC1 inhibition by 1D-142 in HCC. Most importantly, the RAC1 inhibitor 1D-142 strongly reduce tumour growth and intrahepatic metastasis in HCC mice models. Additionally, 1D-142 decreases hepatic stellate cell activation and exerts an anti-fibrotic effect in vivo.

CONCLUSIONS

The bioinformatics analysis of the HCC datasets, allows identifying RAC1 as a new therapeutic target for HCC. The targeted inhibition of RAC1 by 1D-142 resulted in a potent antitumoural effect in highly proliferative HCC established in fibrotic livers.

Non-invasive Reporter Gene Imaging of Cell Therapies, including T Cells and Stem Cells

Cell therapies represent a rapidly emerging class of new therapeutics. They are intended and developed for the treatment of some of the most prevalent human diseases, including cancer, diabetes, and for regenerative medicine. Currently, they are largely developed without precise assessment of their in vivo distribution, efficacy, or survival either clinically or preclinically. However, it would be highly beneficial for both preclinical cell therapy development and subsequent clinical use to assess these parameters in situ to enable enhancements in efficacy, applicability, and safety. Molecular imaging can be exploited to track cells non-invasively on the whole-body level and can enable monitoring for prolonged periods in a manner compatible with rapidly expanding cell types. In this review, we explain how in vivo imaging can aid the development and clinical translation of cell-based therapeutics. We describe the underlying principles governing non-invasive in vivo long-term cell tracking in the preclinical and clinical settings, including available imaging technologies, reporter genes, and imaging agents as well as pitfalls related to experimental design. Our emphasis is on adoptively transferred T cell and stem cell therapies.

How Non-invasive in vivo Cell Tracking Supports the Development and Translation of Cancer Immunotherapies

Immunotherapy is a relatively new treatment regimen for cancer, and it is based on the modulation of the immune system to battle cancer. Immunotherapies can be classified as either molecular or cell-based immunotherapies, and both types have demonstrated promising results in a growing number of cancers. Indeed, several immunotherapies representing both classes are already approved for clinical use in oncology. While spectacular treatment successes have been reported, particularly for so-called immune checkpoint inhibitors and certain cell-based immunotherapies, they have also been accompanied by a variety of severe, sometimes life-threatening side effects. Furthermore, not all patients respond to immunotherapy. Hence, there is the need for more research to render these promising therapeutics more efficacious, more widely applicable, and safer to use. Whole-body in vivo imaging technologies that can interrogate cancers and/or immunotherapies are highly beneficial tools for immunotherapy development and translation to the clinic. In this review, we explain how in vivo imaging can aid the development of molecular and cell-based anti-cancer immunotherapies. We describe the principles of imaging host T-cells and adoptively transferred therapeutic T-cells as well as the value of traceable cancer cell models in immunotherapy development. Our emphasis is on in vivo cell tracking methodology, including important aspects and caveats specific to immunotherapies. We discuss a variety of associated experimental design aspects including parameters such as cell type, observation times/intervals, and detection sensitivity. The focus is on non-invasive 3D cell tracking on the whole-body level including aspects relevant for both preclinical experimentation and clinical translatability of the underlying methodologies.

Functional comparison of distinct Brachyury+ states in a renal differentiation assay

Mesodermal populations can be generated in vitro from mouse embryonic stem cells (mESCs) using three-dimensional (3-D) aggregates called embryoid bodies or two-dimensional (2-D) monolayer culture systems. Here, we investigated whether Brachyury-expressing mesodermal cells generated using 3-D or 2-D culture systems are equivalent or, instead, have different properties. Using a Brachyury-GFP/E2-Crimson reporter mESC line, we isolated Brachyury-GFP ⁺ mesoderm cells using flow-activated cell sorting and compared their gene expression profiles and ex vivo differentiation patterns. Quantitative real-time polymerase chain reaction analysis showed significant up-regulation of Cdx2, Foxf1 and Hoxb1 in the Brachyury-GFP⁺ cells isolated from the 3-D system compared with those isolated from the 2-D system. Furthermore, using an ex vivo mouse kidney rudiment assay, we found that, irrespective of their source, Brachyury-GFP⁺ cells failed to integrate into developing nephrons, which are derived from the intermediate mesoderm. However, Brachyury-GFP⁺ cells isolated under 3-D conditions appeared to differentiate into endothelial-like cells within the kidney rudiments, whereas the Brachyury-GFP⁺ isolated from the 2-D conditions only did so to a limited degree. The high expression of Foxf1 in the 3-D Brachyury-GFP⁺ cells combined with their tendency to differentiate into endothelial-like cells suggests that these mesodermal cells may represent lateral plate mesoderm.