Restoring Tumour Selectivity of the Bioreductive Prodrug PR-104 by Developing an Analogue Resistant to Aerobic Metabolism by Human Aldo-Keto Reductase 1C3

PR-104 is a phosphate ester pre-prodrug that is converted in vivo to its cognate alcohol, PR-104A, a latent alkylator which forms potent cytotoxins upon bioreduction. Hypoxia selectivity results from one-electron nitro reduction of PR-104A, in which cytochrome P450 oxidoreductase (POR) plays an important role. However, PR-104A also undergoes ‘off-target’ two-electron reduction by human aldo-keto reductase 1C3 (AKR1C3), resulting in activation in oxygenated tissues. AKR1C3 expression in human myeloid progenitor cells probably accounts for the dose-limiting myelotoxicity of PR-104 documented in clinical trials, resulting in human PR-104A plasma exposure levels 3.4- to 9.6-fold lower than can be achieved in murine models. Structure-based design to eliminate AKR1C3 activation thus represents a strategy for restoring the therapeutic window of this class of agent in humans. Here, we identified SN29176, a PR-104A analogue resistant to human AKR1C3 activation. SN29176 retains hypoxia selectivity in vitro with aerobic/hypoxic IC50 ratios of 9 to 145, remains a substrate for POR and triggers γH2AX induction and cell cycle arrest in a comparable manner to PR-104A. SN35141, the soluble phosphate pre-prodrug of SN29176, exhibited superior hypoxic tumour log cell kill (>4.0) to PR-104 (2.5–3.7) in vivo at doses predicted to be achievable in humans. Orthologues of human AKR1C3 from mouse, rat and dog were incapable of reducing PR-104A, thus identifying an underlying cause for the discrepancy in PR-104 tolerance in pre-clinical models versus humans. In contrast, the macaque AKR1C3 gene orthologue was able to metabolise PR-104A, indicating that this species may be suitable for evaluating the toxicokinetics of PR-104 analogues for clinical development. We confirmed that SN29176 was not a substrate for AKR1C3 orthologues across all four pre-clinical species, demonstrating that this prodrug analogue class is suitable for further development. Based on these findings, a prodrug candidate was subsequently identified for clinical trials.

Expansion of myeloid-derived suppressor cells contributes to metabolic osteoarthritis through subchondral bone remodeling

Background Osteoarthritis (OA) subsequent to acute joint injury accounts for a significant proportion of all arthropathies. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid progenitor cells classically known for potent immune-suppressive activity; however, MDSCs can also differentiate into osteoclasts. In addition, this population is known to be expanded during metabolic disease. The objective of this study was to determine the role of MDSCs in the context of OA pathophysiology. Methods In this study, we examined the differentiation and functional capacity of MDSCs to become osteoclasts in vitro and in vivo using mouse models of OA and in MDSC quantitation in humans with OA pathology relative to obesity status. Results We observed that MDSCs are expanded in mice and humans during obesity. MDSCs were expanded in peripheral blood of OA subjects relative to body mass index and in mice fed a high-fat diet (HFD) compared to mice fed a low-fat diet (LFD). In mice, monocytic MDSC (M-MDSC) was expanded in diet-induced obesity (DIO) with a further expansion after destabilization of the medial meniscus (DMM) surgery to induce post-traumatic OA (PTOA) (compared to sham-operated controls). M-MDSCs from DIO mice had a greater capacity to form osteoclasts in culture with increased subchondral bone osteoclast number. In humans, we observed an expansion of M-MDSCs in peripheral blood and synovial fluid of obese subjects compared to lean subjects with OA. Conclusion These data suggest that MDSCs are reprogrammed in metabolic disease, with the potential to contribute towards OA progression and severity.

Increased Expression of CD56 on Plasmacytoid Dendritic Cells in Myeloid Leukemia Associated with Down Syndrome (ML-DS) Is Normal Regeneration and Not Measurable Residual Disease

Introduction: It has long been known that Down syndrome is associated with an increased risk for hematologic malignancies. One such disease is myeloid leukemia associated with Down syndrome (ML-DS), a disease that almost always occurs during the first 5 years of life. As research on ML-DS has progressed, understanding has grown that after the initiation of therapy, the non-neoplastic myeloid progenitor cells in ML-DS patients have a characteristic immunophenotype with the expression of CD56 on a subset of the CD34+ myeloid progenitor cells being one of the most notable features. The discovery that this immunophenotype is normal in ML-DS patients post-therapy has been of the utmost importance as it has led to such patients being properly classified as being negative for measurable residual disease. Plasmacytoid dendritic cells (pDCs) are another cell type in which CD56 expression is often part of the neoplastic immunophenotype, and we hypothesized that CD56 may also be differentially expressed in ML-DS pDCs post-therapy. Herein, we investigated the immunophenotype of pDCs in ML-DS patients found to be negative for measurable residual disease. Methods: A total of 10 bone marrow specimens from ML-DS patients post-treatment initiation and 7 bone marrow specimens from patients that did not have DS, were aged 0-4 years (matching the age range of ML-DS), had a myeloid neoplasm and were post-treatment initiation (non-DS) were included in this study. All specimens were found to be negative for measurable residual disease by difference from normal (ΔN) flow cytometry (the gold standard for the determination of residual disease in the Children's Oncology Group 1531 study on ML-DS) and were evaluated for CD56 and CD303 expression on pDCs. pDCs were defined as HLA-DR+/CD123++ (high intensity). Results: As expected, the ML-DS patients had a significantly greater percentage of CD34+CD56+ myeloid progenitor cells than the non-DS group, both in terms of percent total non-erythroid cells (0.9% vs 0.006%, P<0.001) and percent total myeloid progenitors (38% vs 0.57%, P<0.001). There was not a significant difference between groups in terms of pDC percentage (ML-DS 0.63% of total non-erythroid cells vs non-DS 0.53%, P=0.9%). There were also no significant differences in CD303 expression between the groups, both in terms of percent positive (ML-DS 89% vs non-DS 92%, P=0.5) and mean fluorescence intensity (MFI, in PE) (ML-DS 190 vs non-DS 246, P=0.3). On the other hand, the ML-DS group had significantly greater CD56 expression than the non-DS group, both in percent positive (74% vs 25%, P=0.005) and MFI (PE) (122 vs 5.9, P=0.005). Nine of the 10 ML-DS specimens had CD56 expression on greater than 50% of pDCs, and 3 showed a CD56 MFI of over 200. Conclusions: The data from this preliminary study indicate that much like the myeloid progenitor cells, the pDCs in ML-DS patients after the initiation of therapy have an immunophenotype that could be mistaken as abnormal. Importantly, they show that the setting of cutoff values for the determination of abnormal pDC CD56 expression, even relatively high ones, could lead to false positive results in ML-DS specimens post-treatment initiation. The dissemination of this knowledge is of increased importance as more flow cytometry laboratories begin to increase their investigation of pDCs. Further studies are needed to delineate common mechanisms between the expression of CD56 in myeloid progenitor cells and pDCs in ML-DS patients post-treatment initiation. Disclosures Pardo: Hematologics, Inc.: Current Employment. Lott: Hematologics, Inc.: Current Employment. Loken: Hematologics, Inc.: Current Employment, Other: current equity holder in a privately owned company. Eidenschink Brodersen: Hematologics, Inc.: Current Employment, Other: Equity Ownership.

The genetic abnormalities investigation of leukemia in past few decades

Cytogenetic and molecular analysis of each patient’s leukemia cells has become an essential component of diagnosis prior to treatment. It has furthered our understanding of leukemogenesis at a molecular level. Specific and well-characterized recurring chromosomal abnormalities facilitate diagnosis, confirm subtype classification, and have major prognostic value for treatment planning. Conventional chromosome analysis is a basic way for diagnosis and treatment. In addition in this way evaluation of disease progression is important and so it is the only method that can identify the presence of clonal evolution, particularly in accelerated and relapse phase in the disease. Also conventional cytogenetic can detect chromosomal abnormality associated with its advanced phase. Anyhow, the value of translocation rates in interphase and metaphase nuclei in monitoring leukemia is at the time of diagnosis and after treatment additionally. Genomic profiling transformed our understanding of the genetic basis of leukemia particularly in acute leukemia, which is a malignant clonal proliferation in lymphoid stem cells or myeloid progenitor cells.

Localised renal Langerhans cell histiocytosis coexisting with unilateral renal clear cell carcinoma

Langerhans cell histiocytosis (LCH) is an uncommon group of disorders, which can be either localised or systemic, characterised by abnormal proliferation of monocytes, macrophages and dendritic cells. These disorders represent an aberrant response of myeloid progenitor cells. Bones are the most commonly affected organ but there can be involvement of the skin, lungs, liver and spleen. Renal involvement, however, is rare. LCH is the most commonly seen in children but certain rare forms such as Erdheim-Chester disease can be seen in adults. In this report, we present a case of clear cell renal adenocarcinoma (CCRC) admixed with LCH in a patient with history of smoking and presenting with abdominal pain and heamaturia. Imaging revealed left renal lesion and subsequently left renal nephrectomy was performed with tissue biopsy showing grade 3 clear cell renal cell carcinoma admixed with neoplastic LCH.

miRNome profiling of LSC-enriched CD34+CD38−CD26+ fraction in Ph+ CML-CP samples from Argentinean patients: a potential new pharmacogenomic tool

Chronic myeloid leukemia (CML) is a myeloid stem cell neoplasm characterized by an expansion of myeloid progenitor cells and the presence of BCR-ABL1 oncoprotein. Since the introduction of specific BCR-ABL1 tyrosine kinase inhibitors (TKI), overall survival has improved significantly. However, under long-term therapy patients may have residual disease that originates from TKI-resistant leukemic stem cells (LSC). In this work, we analyzed the miRNome of LSC-enriched CD34+CD38−CD26+ and normal hematopoietic stem cells (HSC) fractions obtained from the same chronic phase (CP) CML patients, and stem and progenitor cells obtained from healthy donors (HD) by next-generation sequencing. We detected a global decrease of microRNA levels in LSC-enriched CD34+CD38−CD26+ and HSC fractions from CML-CP patients, and decreased levels of microRNAs and snoRNAs from a genomic cluster in chromosome 14, suggesting a mechanism of silencing of multiple non-coding RNAs. Surprisingly, HSC from CML-CP patients, despite the absence of BCR-ABL1 expression, showed an altered miRNome. We confirmed by RT-qPCR that the levels of miR-196a-5p were increased more than nine-fold in CD26+ (BCR-ABL1+) vs. CD26− (BCR-ABL1−) CD34+CD38− fractions from CML-CP patients at diagnosis, and in silico analysis revealed a significant association to lipid metabolism and hematopoiesis functions. In the light of recent descriptions of increased oxidative metabolism in CML LSC-enriched fractions, these results serve as a guide for future functional studies that evaluate the role of microRNAs in this process. Metabolic vulnerabilities in LSCs open the road for new therapeutic strategies. This is the first report of the miRNome of CML-CP CD34+CD38− fractions that distinguishes between CD26+ (BCR-ABL1+) and their CD26− (BCR-ABL1-) counterparts, providing valuable data for future studies.

Coexistence of multiple myeloma and chronic myeloleukosis in one patient

Intoduction. Multiple myeloma (MM) and chronic myelogenous leukaemia (CML) are two haematological malignancies developing through tumour transformation of lymphoid and myeloid progenitor cells, respectively, not sharing a common ancestry. Coexistence of the two diseases is extremely rare.Aim. Clinical description of a patient diagnosed with CML in a few months after start of MM therapy.Main findings. We report a clinical case of MM and CML in a 62 years-old female patient. MM was diagnosed newly and followed by 5 VD chemotherapy cycles. Treatment discontinued due to severe polyneuropathy. The patient was transferred to thalidomide maintenance therapy. CML was diagnosed 12 months after initiation of thalidomide therapy: BCR-ABL (p190), BCR-ABL (p210). Since imatinib produced short-term effect, dasatinib therapy was started. Following 16 months after the onset of dasatinib therapy, MM relapse and CML progression were diagnosed.

Hdac3 deletion in myeloid progenitor cells enhances bone healing in females and limits osteoclast fusion via Pmepa1

Previous studies examining the role of the histone deacetylase Hdac3 within myeloid cells demonstrated that Hdac3 promotes M2 activation and tissue healing in inflammatory conditions. Since myeloid lineage cells are required for proper bone formation and regeneration, in this study we examined the functions of Hdac3 during bone healing. Conditional deletion of Hdac3 within myeloid progenitors accelerates healing of cortical bone defects. Moreover, reduced osteoclast numbers within the defect site are correlated with Hdac3 suppression. Ex vivo osteoclastogenesis assays further demonstrate that Hdac3 deficiency limits osteoclastogenesis, the number of nuclei per cell and bone resorption, suggesting a defect in cell fusion. High throughput RNA sequencing identified the transmembrane protein Pmepa1 as a differentially expressed gene within osteoclast progenitor cells. Knockdown of Pmepa1 partially restores defects in osteoclastogenesis induced by Hdac3 deficiency. These results show that Hdac3 is required for optimal bone healing and osteoclast fusion, potentially via its regulation of Pmepa1 expression.

Predicting single-cell gene expression profiles of imaging flow cytometry data with machine learning

High-content imaging and single-cell genomics are two of the most prominent high-throughput technologies for studying cellular properties and functions at scale. Recent studies have demonstrated that information in large imaging datasets can be used to estimate gene mutations and to predict the cell-cycle state and the cellular decision making directly from cellular morphology. Thus, high-throughput imaging methodologies, such as imaging flow cytometry can potentially aim beyond simple sorting of cell-populations. We introduce IFC-seq, a machine learning methodology for predicting the expression profile of every cell in an imaging flow cytometry experiment. Since it is to-date unfeasible to observe single-cell gene expression and morphology in flow, we integrate uncoupled imaging data with an independent transcriptomics dataset by leveraging common surface markers. We demonstrate that IFC-seq successfully models gene expression of a moderate number of key gene-markers for two independent imaging flow cytometry datasets: (i) human blood mononuclear cells and (ii) mouse myeloid progenitor cells. In the case of mouse myeloid progenitor cells IFC-seq can predict gene expression directly from brightfield images in a label-free manner, using a convolutional neural network. The proposed method promises to add gene expression information to existing and new imaging flow cytometry datasets, at no additional cost.