Molecular Mechanisms in Murine Syngeneic Leukemia Stem Cells

Acute Myeloid Leukemia (AML) is a severe disease with a very high relapse rate. AML relapse may be attributable to leukemic stem cells (LSC). Notably, the "cancer stem cell" theory, which relates to LSCs, is controversial and criticized due to the technical peculiarities of the xenotransplant of human cells into mice. In this study, we searched for possible LSCs in an immunocompetent synergetic mice model. First, we found phenotypic heterogeneity in the ML23 leukemia line. We prospectively isolated a sub-population using the surface markers cKit⁺CD9^-CD48⁺Mac1^-/low, which have the potency to relapse the disease. Importantly, this sub-population can pass in syngeneic hosts and retrieve the heterogeneity of the parental ML23 leukemia line. The LSC sub-population resides in various organs. We present a unique gene expression signature of the LSC in the ML23 model compared to the other sub-populations. Interestingly, the ML23 LSC sub-population expresses therapeutic targeted genes such as CD47 and CD93. Taken together, we present the identification and molecular characterization of LSCs in a syngeneic murine model.

Blocking the PCNA/NKp44 Checkpoint to Stimulate NK Cell Responses to Multiple Myeloma

Simple Summary

Membrane-associated PCNA is expressed on the surface of human MM cell lines and primary MM cells. Mab 14-25-9 interacts with membrane-associated PCNA and blocks its binding to NK-expressed NKp44, thus activating NK function. We showed that mAb 14-25-9 can serve as an immune checkpoint blocker, enhancing the function of NK cells on target human MM cell lines and primary cells.

Abstract

Multiple Myeloma (MM) is a devastating malignancy that evades immune destruction using multiple mechanisms. The NKp44 receptor interacts with PCNA (Proliferating Cell Nuclear Antigen) and may inhibit NK cells’ functions. Here we studied in vitro the expression and function of PCNA on MM cells. First, we show that PCNA is present on the cell membrane of five out of six MM cell lines, using novel anti-PCNA mAb developed to recognize membrane-associated PCNA. Next, we stained primary bone marrow (BM) mononuclear cells from MM patients and showed significant staining of membrane-associated PCNA in the fraction of CD38⁺CD138⁺ BM cells that contain the MM cells. Importantly, blocking of the membrane PCNA on MM cells enhanced the activity of NK cells, including IFN-γ-secretion and degranulation. Our results highlight the possible blocking of the NKp44-PCNA immune checkpoint by the mAb 14-25-9 antibody to enhance NK cell responses against MM, providing a novel treatment option.

Hypersensitivity response has negligible impact on Hematopoietic Stem Cells

Immune cells are generated from hematopoietic stem cells (HSCs) in the bone marrow (BM). Immune stimulation can rapidly activate HSCs out of their quiescent state to accelerate the generation of immune cells. HSCs' activation follows various viral or bacterial stimuli, and we sought to investigate the hypersensitivity immune response. Surprisingly, the Ova-induced hypersensitivity peritonitis model finds no significant changes in BM HSCs. HSC markers cKIT, SCA1, CD48, CD150, and the Fgd5-mCherry reporter showed no significant difference from control. Functionally, hypersensitivity did not alter HSCs' potency, as assayed by transplantation. We further characterized the possible impact of hypersensitivity using RNA-sequencing of HSCs, finding minor changes at the transcriptome level. Moreover, hypersensitivity induced no significant change in the proliferative state of HSCs. Therefore, this study suggests that, in contrast to other immune stimuli, hypersensitivity has no impact on HSCs.

Botryllus schlosseri as a Unique Colonial Chordate Model for the Study and Modulation of Innate Immune Activity

Understanding the mechanisms that sustain immunological nonreactivity is essential for maintaining tissue in syngeneic and allogeneic settings, such as transplantation and pregnancy tolerance. While most transplantation rejections occur due to the adaptive immune response, the proinflammatory response of innate immunity is necessary for the activation of adaptive immunity. Botryllus schlosseri, a colonial tunicate, which is the nearest invertebrate group to the vertebrates, is devoid of T- and B-cell-based adaptive immunity. It has unique characteristics that make it a valuable model system for studying innate immunity mechanisms: (i) a natural allogeneic transplantation phenomenon that results in either fusion or rejection; (ii) whole animal regeneration and noninflammatory resorption on a weekly basis; (iii) allogeneic resorption which is comparable to human chronic rejection. Recent studies in B. schlosseri have led to the recognition of a molecular and cellular framework underlying the innate immunity loss of tolerance to allogeneic tissues. Additionally, B. schlosseri was developed as a model for studying hematopoietic stem cell (HSC) transplantation, and it provides further insights into the similarities between the HSC niches of human and B. schlosseri. In this review, we discuss why studying the molecular and cellular pathways that direct successful innate immune tolerance in B. schlosseri can provide novel insights into and potential modulations of these immune processes in humans.

Syngeneic leukemia models using lentiviral transgenics

Animal models are necessary to study cancer and develop treatments. After decades of intensive research, effective treatments are available for only a few types of leukemia, while others are currently incurable. Our goal was to generate novel leukemia models in immunocompetent mice. We had achieved abilities for overexpression of multiple driving oncogenes simultaneously in normal primary cells, which can be transplanted and followed in vivo. Our experiments demonstrated the induction of primary malignant growth. Leukemia lines that model various types of leukemia, such as acute myeloid leukemia (AML) or chronic lymphocytic leukemia (CLL), were passaged robustly in congenic wild-type immunocompetent mice. These novel leukemia lines, which may complement previous models, offer the flexibility to generate tailored models of defined oncogenes of interest. The characterization of our leukemia models in immunocompetent animals can uncover the mechanisms of malignancy progression and offer a unique opportunity to stringently test anti-cancer chemotherapies.

Evidence for pain attenuation by the motor system-based judgment of agency

Pain is an integral part of our lives. Although the effect of 'control' on sensed pain has been extensively studied and discussed, recent findings seem to be at odds with the substantial evidence for a robust motor-based sensory attenuation effect - an indirect marker for one's sense of agency. The goal of the current study was to re-examine whether there is evidence for such an effect in the context of pain. In three experiments, human participants were aversively stimulated and the sensitivity of self-reported pain to factors previously shown to modulate the sensory attenuation effect was tested (control over parameters of the stimulation; temporal contiguity and predictability, and stimulation intensity). Two of three experiments found some evidence that objective control attenuates pain, but only when the painful stimulation immediately follows the motor response. We discuss the complex relations between having objective control, feeling helpless, predictability and sensed pain.

Neat1 in hematopoietic stem cells

Hematopoietic Stem Cells (HSCs) generate blood and immune cells through a hierarchical process of differentiation. Genes that regulate this process are of great interest for understanding normal and also malignant hematopoiesis. Surprisingly, however, very little is known about long-non-coding RNAs (lncRNA) in HSCs. Neat1 is a lncRNA that plays a major role in the formation of sub-nuclear structures called paraspeckles, and was reported to regulate proliferation and differentiation in other cells types. We detected Neat1 expression using RNA-seq data and RT-qPCR in HSCs, progenitors and effector immune cells, by specific detection of its isoforms. Neat1 is highly expressed in stem and progenitor cells, yet it shows significant reduction in granulocytes. Microscopically, Neat1 is detected as sharp nuclear foci. Paraspeckle proteins NONO and PSPC1 are detected as aggregated nuclear foci in fresh primary hematopoietic cells, and in cultured cells. Induction of differentiation in vitro was found to enhance Neat1 expression. Taken together, our data demonstrate for the first time the expression of Neat1 and paraspeckles formation in HSCs and along hematopoiesis.

Mapping Whole-Transcriptome Splicing in Mouse Hematopoietic Stem Cells

Hematopoietic stem cells (HSCs) are rare cells that generate all the various types of blood and immune cells. High-quality transcriptome data have enabled the identification of significant genes for HSCs. However, most genes are expressed in various forms by alternative splicing (AS), extending transcriptome complexity. Here, we delineate AS to determine which isoforms are expressed in mouse HSCs. Our analysis of microarray and RNA-sequencing data includes differential expression of splicing factors that may regulate AS, and a complete map of splicing isoforms. Multiple types of isoforms for known HSC genes and unannotated splicing that may alter gene function are presented. Transcriptome-wide identification of genes and their respective isoforms in mouse HSCs will open another dimension for adult stem cells.

Plant responsiveness to root-root communication of stress cues

BACKGROUND AND AIMS

Phenotypic plasticity is based on the organism's ability to perceive, integrate and respond to multiple signals and cues informative of environmental opportunities and perils. A growing body of evidence demonstrates that plants are able to adapt to imminent threats by perceiving cues emitted from their damaged neighbours. Here, the hypothesis was tested that unstressed plants are able to perceive and respond to stress cues emitted from their drought- and osmotically stressed neighbours and to induce stress responses in additional unstressed plants.

METHODS

Split-root Pisum sativum, Cynodon dactylon, Digitaria sanguinalis and Stenotaphrum secundatum plants were subjected to osmotic stress or drought while sharing one of their rooting volumes with an unstressed neighbour, which in turn shared its other rooting volume with additional unstressed neighbours. Following the kinetics of stomatal aperture allowed testing for stress responses in both the stressed plants and their unstressed neighbours.

KEY RESULTS

In both P. sativum plants and the three wild clonal grasses, infliction of osmotic stress or drought caused stomatal closure in both the stressed plants and in their unstressed neighbours. While both continuous osmotic stress and drought induced prolonged stomatal closure and limited acclimation in stressed plants, their unstressed neighbours habituated to the stress cues and opened their stomata 3-24 h after the beginning of stress induction.

CONCLUSIONS

The results demonstrate a novel type of plant communication, by which plants might be able to increase their readiness to probable future osmotic and drought stresses. Further work is underway to decipher the identity and mode of operation of the involved communication vectors and to assess the potential ecological costs and benefits of emitting and perceiving drought and osmotic stress cues under various ecological scenarios.

Toilet reading habits in Israeli adults

Although toilet reading (TR) is a common habit, the effect of TR on bowel movements is neglected in the medical literature. Our hypothesis was that TR provides a distraction and acts as an unconscious relaxation technique and allows an easier defecation process. The aim of this study was to assess how common is TR and to map the reading/playing toilet habits in the Israeli adult population. In addition, we aimed to explore a possible connection between TR and the nature of bowel habits in general and constipation and haemorrhoids in particular. Five hundred adults who represent the diverse demographic backgrounds have been asked to fill an anonymous short questionnaire. The subjects were questioned regarding their demographic details, their TR and playing habits, their bowel habits, whether they suffer from haemorrhoids and whether they use some sort of faecal softener. We found that TR is common and involves 52.7% of the population. Males, younger age, secular population, higher education level and white collar workers compose the TR profile. Although toilet readers spent significantly more time in the toilets, no differences were noted for the type or frequency of stools. Nevertheless, the TR group considered themselves to be less constipated (8.0%vs 13.7%) and had more haemorrhoids (23.6%vs 18.2%). These differences, however, were not significant. Toilet reading is a common and benign habit. It is involved with a longer time spent in the toilet. It seems to be more for fun and not necessarily to solve or due to medical problems.

Do forceps biopsies truthfully reflect the nature of endoscopically uncovered polypoid lesions of the colon?

BACKGROUND

Total excision of colonic polyps is not always attainable and in some patients it is clinically contraindicated. Also, a resected polyp may be lost at any step between its endoscopic removal and its embedding in paraffin. The aim of this study was to compare the histological features of colonic polyps as analysed by the study of biopsy-forceps obtained samples with those assessed on scrutinizing the totally resected growths.

PATIENTS AND METHODS

This prospective study included a cohort of 59 patients in whom, in the course of an elective colonoscopy, a total excision of a 6 mm-sized or larger polyp was called for. Sizeable biopsies were obtained by means of an Olympus Multibyte forceps prior to the total polypectomy. Subsequent to the study of the polypectomy specimens, the forceps biopsy samples were submitted for histological examination. The pathologists were blinded as to the source of the tissue they were studying. The diagnoses rendered by evaluating the biopsy samples and polypectomy specimens of each patient were contrasted with each other.

RESULTS

Major discrepancies between the histological features of the fragments captured by the biopsy-forceps and the factual nature of the totally removed polyps were uncovered in 11 (18.6%) of 59 cases. Intriguingly, the grade of the tumours was underrated in all the 11 cases, as judged by contrasting the tentative diagnoses of the forceps-biopsies with the decisive diagnoses of the polypectomies. Importantly, 2 adenocarcinomas would have been missed by just looking at the forceps-retrieved sample.

CONCLUSIONS

In our experience, a discordance of 18.6% is to be expected between the diagnoses rendered after examining forceps-biopsies of and totally excised colonic polyps. Nevertheless, it is advisable to procure biopsies prior to the excision of the growths, because on those occasions in which patients' growths cannot be removed or have not been retrieved for one reason or another, a small forceps-captured tissue sample correctly reflects the characteristics of the polyp in 81.4% of the cases. Finally, the biopsies may be discarded in the event that total removal was successful.

IGF-II and IGF binding protein (IGFBP-1, IGFBP-3) gene expression in fetal rhesus monkey tissues during the second and third trimesters

The IGF system is a key modulator of somatic fetal growth. Studies with human fetal tissues have shown a specific spatial and temporal pattern of expression of IGF and IGF binding protein (IGFBP) mRNAs, but have been limited to defined periods during gestation (i.e. 8-20 wk gestation) because of tissue availability. To fully assess the role of these peptides in the primate growth process, a longitudinal study was conducted that focused on the expression of IGF-II and IGFBP-1 and IGFBP-3 genes in the rhesus monkey (Macaca mulatta). Liver, kidney, brain, and lung were collected from rhesus monkey fetuses approximately every 2 wk from 65 (early second trimester) through 150 d gestation (term 165 +/- 10 d) (n = 50), then processed for in situ hybridization using radiolabeled human cDNAs. IGF-II mRNA was abundantly expressed in fetal kidney (maturing glomerulus, supporting mesenchyme, cells of the developing nephrons), liver (hepatocytes), cerebral cortex (choroid plexus, capillaries), and lung (blood vessels, connective tissues, lamina propria, cartilage framework). IGFBP-1 was expressed only in the hepatocytes and IGFBP-3 mRNA was modestly expressed within the kidney (developing nephrons, collecting system mesenchyme), and liver (hepatocytes). These studies have shown that (1) IGF-II, IGFBP-1, and IGFBP-3 are expressed in specific cell types of the fetal monkey indicating a paracrine/autocrine role during development; (2) changes in IGF-II and IGFBP mRNA expression occur with advancing gestation; and (3) fetal monkey tissues express IGF-II and IGFBPs in a similar manner when compared with the human fetus.

Transplantation of human peripheral blood stem cells into fetal rhesus monkeys (Macaca mulatta)

BACKGROUND

Methods for assessing engraftment efficiency have been explored in a primate xenogeneic model of in utero hematopoietic stem cell transplantation.

METHODS

Human peripheral blood stem cells (PBSC) were obtained by leukapheresis from a human male donor after 4 days of administration of recombinant human granulocyte-colony stimulating factor (5 microg/kg/ day). PBSC were enriched for the CD34+ population with and without T-cell depletion. The resulting mononuclear cells consisted of two cell populations, one that was stem cell enriched (0.83% CD3+ cells, 95% CD34+; group 1) and one that was stem cell enriched and T-cell depleted (<0.03% CD3+ cells, 98% CD34+; group 2). Four fetal monkeys (two per group) received either two or four i.p. injections (approximately 5x10(6) cells/injection) via ultrasound guidance every other day over a 7-day period (gestational days 50, 52, 54, and 56). One fetus in each group also received i.p. recombinant human stem cell factor (25 microg/kg) and recombinant human granulocyte-colony stimulating factor (10 microg/kg) posttransplant every 10 days from gestational day 60-150.

RESULTS

Four healthy newborns were delivered at term, and specimens were analyzed by polymerase chain reaction for the human Y chromosome (birth, monthly to 6 months; blood, marrow, progenitor assays). Polymerase chain reaction results were positive for all four newborns in all specimens assessed, and flow cytometric analysis for human CD45 in marrow showed engraftment ranging from 0.1-1.7%. There was no evidence of graft-versus-host disease in any of the animals.

CONCLUSION

These studies show that (1) multilineage engraftment of human PBSC can be achieved in the fetal rhesus recipient, (2) the rhesus fetus appears to tolerate relatively high numbers of human CD3+ cells, and (3) healthy chimeric rhesus infants can be delivered at term after multiple in utero procedures.

The white blood cell line: changes induced in mice by hypergravity

The effect of hypergravity on the white blood cell (WBC) line of mice was investigated by use of horizontal centrifuge. Several sets of experiments were performed, in which the parameters measured were the WBC and differential cell count in the peripheral blood. In another experiment, lymphocyte counts from the spleen, lymph nodes, and the thymus were measured. The needed samples were taken from the mice during a stay of 7-40 days under a hypergravity of 1.6G. The test groups that were placed on the arms of the centrifuge (1.6G) were compared with stationary control groups (1G) and a rotating control group located at the center of the centrifuge (1G). Such a comparison revealed the test animals to be deficient on all counts, to wit, showing a decrease in total number of WBC's, a decrease in lymphocyte number in the peripheral blood and a decrease in the number of lymphocyte in the spleen and thymus. The decrease of lymphocytes in peripheral blood was characterized by two different slopes--an early and temporary decrease at the first days of the experiment evident in both test and rotating control groups followed by a temporary increase, and a later persistent decrease, evident only in the test group, while in the rotating control lymphocyte counts reverted to normal. There were no significant differences in monocyte or neutrophil counts, except for a temporary increase in the number of neutrophils which peaked on the seventh day. In order to evaluate the effect of hypergravity on restoration of hematopoiesis following hematopoietic suppression, 5-fluoro-uracil (5-FU) was administered i.v. to both the experimental and control mice. Suppression of bone marrow was observed in all groups injected with 5-FU, but while there was later an increase in cell counts in the control groups, there was no such increase in the test group subjected to hypergravity.

An aldosterone regulated chicken intestine protein with high affinity to amiloride

The pattern of chicken intestine amiloride-binding proteins was determined using the photoreactive amiloride analogue 2'-methoxy-5'-nitrobenzamil (NMBA) and a polyclonal anti-amiloride antibody. At 10(-7)M, NMBA inhibits approximately 62% of the Na+ channel activity. At this concentration the amiloride analogue labels a number of membrane proteins, and in particular a 40-45 kDa polypeptide denoted ABP40. Incorporation of NMBA into ABP40 could be prevented by a 100-fold excess of benzamil, but not by a 1000-fold excess of 5-(N-ethyl-N-isopropyl)-amiloride. Labeling of ABP40 was intense in membranes derived from salt-deprived chickens and approximately 5-fold weaker in membranes from salt-repleted animals. Because of its small size, ABP40 is not likely to be an avian Na+ channel subunit, yet this amiloride-binding protein could be involved in the response to aldosterone.

Cloning and induction by low NaCl intake of avian intestine Na+ channel subunits

The alpha-subunit of the highly Na(+)-selective amiloride-blockable channel (ENaC) was cloned from chicken lower intestine. The deduced amino acid sequence of the avian clone exhibits -60% identity to the previously cloned mammalian and amphibian alpha-subunits. It also maintains the same hydropathy profile and structural motifs. These include two transmembrane domains separated by a large extracellular loop, four extracellular N-glycosylation sites, a cysteine-rich box in the extracellular domain, and a proline-rich stretch at the carboxy terminus. Xenopus oocytes injected with cRNA transcribed from this clone express a small amiloride-blockable Na+ conductance. Degenerate primers have been used to amplify two other related products. Sequence homology indicates that one of them is the beta-subunit, whereas the other appears to represent a closely related but different transcript. Regulation of the mRNA corresponding to these clones was examined in chickens fed normal and low-NaCl rations. The low-salt diet evoked an approximately fourfold increase in the abundance of mRNA coding for the alpha-subunit, presumably through an increase in plasma aldosterone. The beta- and "beta-like" transcripts were even more strongly affected. The current data provide additional information on sequence conservation in the growing ENaC family and demonstrate that the avian intestine channel is strongly induced by varying NaCl intake.

Aldosterone induction and epithelial distribution of CHIF

CHIF is a recently cloned, corticosteroid-induced gene which evokes K+ channel activity in oocytes (B. Attali, H. Latter, N. Rachamim, and H. Garty. Proc. Natl. Acad. Sci. USA 92: 6092-6096, 1995). To further characterize the possible role of this gene in epithelial ion transport, we have studied its epithelial distribution and hormonal induction. Northern hybridizations indicate that the zonal distribution of CHIF mRNA in kidney is: papilla >>medulla>> cortex. High levels of CHIF were also detected in a primary culture from inner medullary collecting duct (IMCD). Perfusing rats with < 20 nM aldosterone through osmotic minipumps evoked a 22.4 +/- 1.9-fold increase in colonic CHIF. A significant increase was observed 3 h after administrating the corticosteroid, but maximal response was detected only after a 72-h incubation. This response appears to be mineralocorticoid specific; perfusing or injecting rats with maximal doses of dexamethasone did not evoke a further increase in CHIF mRNA. In contrast, high levels of CHIF are expressed in kidney papilla and IMCD primary culture, irrespective of corticosteroid treatment. Thus, like the apical Na+ channel and the H(+)-K(+)-adenosinetriphosphatase, CHIF is mineralocorticoid induced in the colon but constitutively expressed in kidney.

Low doses of radiation induce systemic production of cytokines: possible contribution to leukemogenesis

Experiments were conducted to explore the possible effect of low-dose irradiation on cytokine production in mice. SJL/J and C57BL/6J mice were exposed to 3 Gy and 4 Gy respectively. At various time intervals thereafter, lung-conditioned media, bone-marrow-conditioned media and sera were collected. Interleukin-6 and macrophage-colony-stimulating-factor activities were tested. Interleukin-6 in lung-conditioned media from both strains was found to be significantly induced by irradiation. Macrophage-colony-stimulating-factor activity was greatly enhanced in sera of irradiated SJL/J mice as well as in bone-marrow-conditioned media of both strains. The kinetics of the radiation-induced interleukin 6 and macrophage-colony-stimulating-factor activity differed in the 2 strains. SJL/J and C57BL/6J mice have been previously shown to be susceptible to low-dose-radiation-induced leukemia. The coleukemogenic effects of both cytokines in 3 different models of experimental leukemogenesis is demonstrated.

An epithelial high-affinity amiloride-binding site, different from the Na+ channel

Specific binding of the radioactive amiloride analogues [3H]phenamil and [3H]benzamil was studied in plasma membrane from chicken lower intestine. A single population of sites whose affinities and specificities towards pyrazinecarboxamides roughly resemble those of the epithelial Na+ channel, was identified. However, a matched comparison of pyrazinecarboxamide binding and Na+ transport inhibition revealed substantial differences between the high-affinity [3H]phenamil-binding site detected, and the site whose occupancy by phenamil blocks Na+ transport. First, 5-(N-ethyl-N-isopropyl)-amiloride was found to displace bound [3H]phenamil at concentrations that are at least 10-fold lower than those needed to block the channel. Second, the rates at which [3H]phenamil associates and dissociates from this site are lower than the rates at which Na+ channels are inhibited and reactivated, under similar conditions. A site with high affinity to both amiloride and 5-(N-ethyl-N-isopropyl)-amiloride was detected also in membranes from other epithelia. We conclude that tight epithelia contain a major high-affinity amiloride receptor other than the Na(+)-conducting channel, the Na+/H+ antiport or the Na+/Ca2+ exchanger. This site could be associated with a pool of nonconducting channels, another (but structurally related) channel, or a totally unrelated protein.

Colony-stimulating factor-1 blocks early pregnancy in mice

To elucidate the mechanisms underlying the suspected immune-related pregnancy failures in humans, we established experimental systems to induce pregnancy blocking and abortion in mice. One system, based on the preimmunization of C57BL/6J females with a syngeneic regressor tumor, is described. Such females fail to develop normal gestations when mated to C57BL/6J x DBA/2 F-1 (B6D2F-1) males or DBA/2 males but sustain normal pregnancies when impregnated by CBA/J or C57BL/6 males. An investigation into the cause of these male-specific pregnancy failures led us to identify colony-stimulating factor-1 (CSF-1) as responsible for both pregnancy-block and resorption of embryos. Indeed, injection of very small amounts of CSF-1 into plugged females, for the first 5 days of pregnancy, was sufficient to block B6D2F-1-induced gestations but had no effect on CBA/J-mated females. It also induced a high rate of fetal resorptions in the sensitive mating. These results suggest a novel mechanism underlying pregnancy failures: a mechanism based on cytokines and their effect on early embryonic development in certain mating combinations.