Serial Transplantation Research Articles

Recurrent Idiopathic Liver Allograft Failure

Many transplant programs have had patients who develop idiopathic recurrent liver allograft failure, necessitating serial transplants, and are deemed to have refractory or recurrent rejection. The frequency and the etiology of this immunologic dysfunction have not been well characterized. Herein, we illustrate the case of a patient who required three retransplants over a period of 20 years for recurrent liver allograft failure. By extensively compiling the patient's many liver biopsy specimens and explants over time, we demonstrate that antibody-mediated rejection (AMR) was a major contributing factor from the outset. We conducted a review of the Scientific Registry for Transplant Recipients database to estimate the potential frequency of AMR. As illustrated by this case, AMR has varied histologic findings in the setting of elevated donor-specific antibody titers. The cause of recurrent allograft failure in this patient was likely a combination of acute cellular rejection and AMR, manifestations of likely underlying immune dysregulation. Pathologists and transplant physicians should recognize the variable histologic presentations of AMR, which is imperative for its timely intervention. This case demonstrates how difficult the diagnosis of AMR can be to make, highlighting the need for strong clinical suspicion in patients having difficult-to-treat rejection and recurrent allograft failure.

The TGF\u03b2-miR-499a-SHKBP1 pathway induces resistance to EGFR inhibitors in osteosarcoma cancer stem cell-like cells

Background/aimsA novel paradigm in tumor biology suggests that osteosarcoma (OS) chemo-resistance is driven by osteosarcoma stem cell-like cells (OSCs). As the sensitivity of only a few tumors to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) can be explained by the presence of EGFR tyrosine kinase (TK) domain mutations, there is a need to elucidate mechanisms of resistance to EGFR-targeted therapies in OS that do not harbor TK sensitizing mutations to develop new strategies to circumvent resistance to EGFR inhibitors.MethodsAs a measure of the characters of OSCs, serum-free cultivation, cell viability test with erlotinib, and serial transplantation in vivo was used. Western blot assays were used to detect the association between erlotinib resistance and transforming growth factor beta (TGFβ)-induced epithelial-to-mesenchymal transition (EMT) progression. By using TaqMan qPCR miRNA array, online prediction software, luciferase reporter assays and western blot analysis, we further elucidated the mechanisms.ResultsHere, CD166+ cells are found in 10 out of 10 tumor samples. We characterize that CD166+ cells from primary OS tissues bear hallmarks of OSCs and erlotinib-resistance. TGFβ-induced EMT-associated kinase switch is demonstrated to promote erlotinib-resistance of CD166+ OSCs. Further mechanisms study show that TGFβ-induced EMT decreases miR-499a expression through the direct binding of Snail1/Zeb1 to miR-499a promoter. Overexpression of miR-499a in CD166+ OSCs inhibits TGFβ-induced erlotinib-resistance in vitro and in vivo. SHKBP1, the direct target of miR-499a, regulates EGFR activity reduction occurring concomitantly with a TGFβ-induced EMT-associated kinase switch to an AKT-activated EGFR-independent state. TGFβ-induced activation of AKT co-opts an increased SHKBP1 expression, which further regulates EGFR activity. In clinic, the ratio of the expression levels of SHKBP1 and miR-499a is highly correlated with EMT and resistance to erlotinib.ConclusionTGFβ–miR-499a–SHKBP1 network orchestrates the EMT-associated kinase switch that induces resistance to EGFR inhibitors in CD166+ OSCs, implies that inhibition of TGFβ induced EMT-associated kinase switch may reverse the chemo-resistance of OSCs to EGFR inhibitors. We also suggest that an elevated SHKBP1/miR-499a ratio is a molecular signature that characterizes the erlotinib-resistant OS, which may have clinical value as a predictive biomarker.

NCAM1 (CD56) promotes leukemogenesis and confers drug resistance in AML

AbstractNeural cell adhesion molecule 1 (NCAM1; CD56) is expressed in up to 20% of acute myeloid leukemia (AML) patients. NCAM1 is widely used as a marker of minimal residual disease; however, the biological function of NCAM1 in AML remains elusive. In this study, we investigated the impact of NCAM1 expression on leukemogenesis, drug resistance, and its role as a biomarker to guide therapy. Beside t(8;21) leukemia, NCAM1 expression was found in most molecular AML subgroups at highly heterogeneous expression levels. Using complementary genetic strategies, we demonstrated an essential role of NCAM1 in the regulation of cell survival and stress resistance. Perturbation of NCAM1 induced cell death or differentiation and sensitized leukemic blasts toward genotoxic agents in vitro and in vivo. Furthermore, Ncam1 was highly expressed in leukemic progenitor cells in a murine leukemia model, and genetic depletion of Ncam1 prolonged disease latency and significantly reduced leukemia-initiating cells upon serial transplantation. To further analyze the mechanism of the NCAM1-associated phenotype, we performed phosphoproteomics and transcriptomics in different AML cell lines. NCAM1 expression strongly associated with constitutive activation of the MAPK-signaling pathway, regulation of apoptosis, or glycolysis. Pharmacological inhibition of MEK1/2 specifically inhibited proliferation and sensitized NCAM1+ AML cells to chemotherapy. In summary, our data demonstrate that aberrant expression of NCAM1 is involved in the maintenance of leukemic stem cells and confers stress resistance, likely due to activation of the MAPK pathway. Targeting MEK1/2 sensitizes AML blasts to genotoxic agents, indicating a role for NCAM1 as a biomarker to guide AML treatment.

CD27, CD201, FLT3, CD48, and CD150 cell surface staining identifies long-term mouse hematopoietic stem cells in immunodeficient non-obese diabetic severe combined immune deficient-derived strains.

Staining for CD27 and CD201 (endothelial protein C receptor) has been recently suggested as an alternative to stem cell antigen–1 (Sca1) to identify hematopoietic stem cells in inbred mouse strains with low or nil expression of SCA1. However, whether staining for CD27 and CD201 is compatible with low fms-like tyrosine kinase 3 (FLT3) expression and the “SLAM” code defined by CD48 and CD150 to identify mouse long-term reconstituting hematopoietic stem cells has not been established. We compared the C57BL/6 strain, which expresses a high level of SCA1 on hematopoietic stem cells to non-obese diabetic severe combined immune deficient NOD.CB17-prkdcscid/Sz (NOD-scid) mice and NOD.CB17-prkdcscid il2rgtm1Wj1/Sz (NSG) mice which both express low to negative levels of SCA1 on hematopoietic stem cells. We demonstrate that hematopoietic stem cells are enriched within the linage-negative C-KIT+ CD27+ CD201+ FLT3− CD48-CD150+ population in serial dilution long-term competitive transplantation assays. We also make the novel observation that CD48 expression is up-regulated in Lin− KIT+ progenitors from NOD-scid and NSG strains, which otherwise have very few cells expressing the CD48 ligand CD244. Finally, we report that unlike hematopoietic stem cells, SCA1 expression is similar on bone marrow endothelial and mesenchymal progenitor cells in C57BL/6, NOD-scid and NSG mice. In conclusion, we propose that the combination of Lineage, KIT, CD27, CD201, FLT3, CD48, and CD150 antigens can be used to identify long-term reconstituting hematopoietic stem cells from mouse strains expressing low levels of SCA1 on hematopoietic cells.

The global clonal complexity of the murine blood system declines throughout life and after serial transplantation

AbstractAlthough many recent studies describe the emergence and prevalence of “clonal hematopoiesis of indeterminate potential” in aged human populations, a systematic analysis of the numbers of clones supporting steady-state hematopoiesis throughout mammalian life is lacking. Previous efforts relied on transplantation of “barcoded” hematopoietic stem cells (HSCs) to track the contribution of HSC clones to reconstituted blood. However, ex vivo manipulation and transplantation alter HSC function and thus may not reflect the biology of steady-state hematopoiesis. Using a noninvasive in vivo color-labeling system, we report the first comprehensive analysis of the changing global clonal complexity of steady-state hematopoiesis during the natural murine lifespan. We observed that the number of clones (ie, clonal complexity) supporting the major blood and bone marrow hematopoietic compartments decline with age by ∼30% and ∼60%, respectively. Aging dramatically reduced HSC in vivo–repopulating activity and lymphoid potential while increasing functional heterogeneity. Continuous challenge of the hematopoietic system by serial transplantation provoked the clonal collapse of both young and aged hematopoietic systems. Whole-exome sequencing of serially transplanted aged and young hematopoietic clones confirmed oligoclonal hematopoiesis and revealed mutations in at least 27 genes, including nonsense, missense, and deletion mutations in Bcl11b, Hist1h2ac, Npy2r, Notch3, Ptprr, and Top2b.

EGFR/Notch Antagonists Enhance the Response to Inhibitors of the PI3K-Akt Pathway by Decreasing Tumor-Initiating Cell Frequency.

Both EGFR and PI3K-Akt signaling pathways have been used as therapeutically actionable targets, but resistance is frequently reported. In this report, we show that enrichment of the cancer stem cell (CSC) subsets and dysregulation of Notch signaling underlie the challenges to therapy and describe the development of bispecific antibodies targeting both HER and Notch signaling. We utilized cell-based models to study Notch signaling in drug-induced CSC expansion. Both cancer cell line models and patient-derived xenograft tumors were used to evaluate the antitumor effects of bispecific antibodies. Cell assays, flow cytometry, qPCR, and in vivo serial transplantation assays were employed to investigate the mechanisms of action and pharmacodynamic readouts. We found that EGFR/Notch targeting bispecific antibodies exhibited a notable antistem cell effect in both in vitro and in vivo assays. Bispecific antibodies delayed the occurrence of acquired resistance to EGFR inhibitors in triple-negative breast cancer cell line-based models and showed efficacy in patient-derived xenografts. Moreover, the EGFR/Notch bispecific antibody PTG12 in combination with GDC-0941 exerted a stronger antitumor effect than the combined therapy of PI3K inhibitor with EGFR inhibitors or tarextumab in a broad spectrum of epithelial tumors. Mechanistically, bispecific antibody treatment inhibits the stem cell-like subpopulation, reduces tumor-initiating cell frequency, and downregulates the mesenchymal gene expression. These findings suggest that the coblockade of EGFR and Notch signaling has the potential to increase the response to PI3K inhibition, and PTG12 may gain clinical efficacy when combined with PI3K blockage in cancer treatment.

Ttc7a regulates hematopoietic stem cell functions while controlling the stress-induced response.

The molecular machinery that regulates the balance between self-renewal and differentiation properties of hematopoietic stem cells (HSC) has yet to be characterized in detail. Here we found that the tetratricopeptide repeat domain 7 A (Ttc7a) protein, a putative scaffold protein expressed by HSC, acts as an intrinsic regulator of the proliferative response and the self-renewal potential of murine HSC in vivo. Loss of Ttc7a consistently enhanced the competitive repopulating ability of HSC and their intrinsic capacity to replenish the hematopoietic system after serial cell transplantations, relative to wildtype cells. Ttc7a-deficient HSC exhibit a different transcriptomic profile for a set of genes controlling the cellular response to stress, which was associated with increased proliferation in response to chemically induced stress in vitro and myeloablative stress in vivo. Our results therefore revealed a previously unrecognized role of Ttc7a as a critical regulator of HSC stemness. This role is related, at least in part, to regulation of the endoplasmic reticulum stress response.

1039 Novel mouse model of recessive dystrophic epidermolysis bullosa-squamous cell carcinoma

The high frequency and extremely aggressive behavior of squamous cell carcinoma from recessive dystrophic epidermolysis bullosa patients (RDEB-cSCC), as well as the lack of an appropriate preclinical mouse model recapitulating the RDEB-cSCC phenotype for testing effective therapies/drugs, creates an urgent need for generating such a model. Here, we established a novel mouse model for RDEB-cSCC, in which we generated 3D cSCC skin constructs (SCs) using RDEB-cSCC and RDEB fibroblasts (FB), which were then grafted onto immunocompromised mice. 16 out of 18 animals that were grafted with RDEB patient-derived cSCC and FB developed tumors within 4 weeks post-grafting, with characteristic morphological features of human RDEB-cSCC. H&E staining of RDEB-cSCC grafts revealed invading epithelial cell columns and differentiated tumor cell islands in the upper dermis. Immunofluorescence (IF) staining showed a complete lack of C7 and increased pSTAT3 expression in the RDEB-cSCC grafted skin construct. Keratin 14, keratin 10 and E-cadherin IF staining were increased within the RDEB-cSCC grafted tumor tissue, indicating the epithelial origin of RDEB-cSCC cells in the dermis and their differentiation. Further, the RDEB-cSCC grafted tumor displayed high proliferation as demonstrated by increased Ki-67+ and p63+ expression seen in IF staining and reduced expression in vimentin staining compared with normal grafts. Moreover, serial transplantation revealed that 88% of RDEB-cSCC tumors had similar biology to the primary tumor (developed on the initial immunocompetent mouse) within 2 weeks post-transplantation onto a second immunocompetent mouse. Our data established a new preclinical model RDEB-cSCC, and an important new method for drug testing in translational cancer research.

PHF6 regulates hematopoietic stem and progenitor cells and its loss synergizes with expression of TLX3 to cause leukemia

AbstractSomatically acquired mutations in PHF6 (plant homeodomain finger 6) frequently occur in hematopoietic malignancies and often coincide with ectopic expression of TLX3. However, there is no functional evidence to demonstrate whether these mutations contribute to tumorigenesis. Similarly, the role of PHF6 in hematopoiesis is unknown. We report here that Phf6 deletion in mice resulted in a reduced number of hematopoietic stem cells (HSCs), an increased number of hematopoietic progenitor cells, and an increased proportion of cycling stem and progenitor cells. Loss of PHF6 caused increased and sustained hematopoietic reconstitution in serial transplantation experiments. Interferon-stimulated gene expression was upregulated in the absence of PHF6 in hematopoietic stem and progenitor cells. The numbers of hematopoietic progenitor cells and cycling hematopoietic stem and progenitor cells were restored to normal by combined loss of PHF6 and the interferon α and β receptor subunit 1. Ectopic expression of TLX3 alone caused partially penetrant leukemia. TLX3 expression and loss of PHF6 combined caused fully penetrant early-onset leukemia. Our data suggest that PHF6 is a hematopoietic tumor suppressor and is important for fine-tuning hematopoietic stem and progenitor cell homeostasis.

Expression and functional relevance of long non-coding RNAs in acute myeloid leukemia stem cells.

In acute myeloid leukemia (AML), novel therapies are needed to target not only the rapidly dividing AML blasts but also the distinct population of leukemia stem cells (LSCs), which have abnormal self-renewal capacity and increased chemotherapy resistance. Elucidation of the expression and function of deregulated genes in LSCs is critical to specifically target LSCs and may consequently lead to improving outcomes of AML patients. Here, we correlated long non-coding RNA (lncRNA) expression profiles obtained from two RNA-seq datasets of 375 younger (aged <60 years) 76 older (≥60 years) adults with cytogenetically normal AML with a 'core enriched' (CE) gene expression signature (GES) associated with LSCs. We identified a LSC-specific signature of 111 lncRNAs that correlated strongly with the CE-GES. Among the top upregulated LSC-associated lncRNAs, we identified the lncRNA DANCR. Further experiments confirmed that DANCR is upregulated in functionally validated LSC-enriched populations. DANCR knock-down in LSCs resulted in decreased stem-cell renewal and quiescence. Furthermore, we showed that targeting Dancr in vivo using a primary murine model of AML (expressing both Mll partial tandem duplication/Flt3 internal tandem duplication) prolonged the survival of mice after serial transplantation. Our data suggest that LSCs have a distinct lncRNA signature with functional relevance and therapeutic potential.

MicroRNA-127-3p controls murine hematopoietic stem cell maintenance by limiting differentiation.

The balance between self-renewal and differentiation is crucial to ensure the homeostasis of the hematopoietic system, and is a hallmark of hematopoietic stem cells. However, the underlying molecular pathways, including the role of micro-RNA, are not completely understood. To assess the contribution of micro-RNA, we performed micro-RNA profiling of hematopoietic stem cells and their immediate downstream progeny multi-potent progenitors from wild-type control and Pbx1-conditional knockout mice, whose stem cells display a profound self-renewal defect. Unsupervised hierarchical cluster analysis separated stem cells from multi-potent progenitors, suggesting that micro-RNA might regulate the first transition step in the adult hematopoietic development. Notably, Pbx1-deficient and wild-type cells clustered separately, linking micro-RNAs to self-renewal impairment. Differential expression analysis of micro-RNA in the physiological stem cell-to-multi-potent progenitor transition and in Pbx1-deficient stem cells compared to control stem cells revealed miR-127-3p as the most differentially expressed. Furthermore, miR-127-3p was strongly stem cell-specific, being quickly down-regulated upon differentiation and not re-expressed further downstream in the bone marrow hematopoietic hierarchy. Inhibition of miR-127-3p function in Lineage-negative cells, achieved through a lentiviral-sponge vector, led to severe stem cell depletion, as assessed with serial transplantation assays. miR-127-3p-sponged stem cells displayed accelerated differentiation, which was uncoupled from proliferation, accounting for the observed stem cell reduction. miR-127-3p overexpression in Lineage-negative cells did not alter stem cell pool size, but gave rise to lymphopenia, likely due to lack of miR-127-3p physiological downregulation beyond the stem cell stage. Thus, tight regulation of miR-127-3p is crucial to preserve the self-renewing stem cell pool and homeostasis of the hematopoietic system.

Phenotypic characterization of malignant progenitor cells in patients with idiopathic myelofibrosis

Objective/BackgroundIdiopathic myelofibrosis (IM) is a clonal hematological malignancy originating from pluripotent hematopoietic stem cells (HSC). HSC are very rare potent cells that reside in the bone marrow (BM) and at a lower level in peripheral blood (PB). Previous studies showed that IM PB CD34+ cells contain not only BM repopulating cells belonging to the malignant clone but also residual normal HSC. MethodsIn the current study, we separated the subpopulations of IM PB CD34+ cells using IL-3Rα/CD123 labeling and further characterized them by genetic and functional analyses. ResultsWe differentiated IM PB CD34+ cells into three subpopulations (IL-3Rαhigh, IL-3Rαlow, and IL-3Rαnegative). IL-3Rαhigh CD34+ cell subgroup represents a small population in IM PB CD34+ cells which was not seen in normal G-CSF mobilized CD34+ cells. IM IL-3Rαhigh CD34+ cells contained significant higher percentage of cells bearing marker chromosome detected by fluorescence in situ hybridization (FISH) analysis. In the absence of growth factors, IM IL-3Rαhigh CD34+ cells exhibited abnormal colony forming ability and carried greater percentage of JAK2V617F mutant allele compared with IL-3Rαlow and IL-3Rαnegative CD34+ cells. ConclusionThese data indicate that IL-3Rαhigh CD34+ cells from IM enriched for the malignant progenitor cells and IL-3Rα/CD123 may be a potential biomarker and therapeutic target for IM. Our findings will be further validated in future studies with a larger sample size and serial transplant in murine models.

Serial transplantation reveals a critical role for endoglin in hematopoietic stem cell quiescence

AbstractTransforming growth factor β (TGF-β) is well known for its important function in hematopoietic stem cell (HSC) quiescence. However, the molecular mechanism underlining this function remains obscure. Endoglin (Eng), a type III receptor for the TGF-β superfamily, has been shown to selectively mark long-term HSCs; however, its necessity in adult HSCs is unknown due to embryonic lethality. Using conditional deletion of Eng combined with serial transplantation, we show that this TGF-β receptor is critical to maintain the HSC pool. Transplantation of Eng-deleted whole bone marrow or purified HSCs into lethally irradiated mice results in a profound engraftment defect in tertiary and quaternary recipients. Cell cycle analysis of primary grafts revealed decreased frequency of HSCs in G0, suggesting that lack of Eng impairs reentry of HSCs to quiescence. Using cytometry by time of flight (CyTOF) to evaluate the activity of signaling pathways in individual HSCs, we find that Eng is required within the Lin−Sca+Kit+–CD48− CD150+ fraction for canonical and noncanonical TGF-β signaling, as indicated by decreased phosphorylation of SMAD2/3 and the p38 MAPK-activated protein kinase 2, respectively. These findings support an essential role for Eng in positively modulating TGF-β signaling to ensure maintenance of HSC quiescence.

The long non-coding RNA Meg3 is dispensable for hematopoietic stem cells

The long non-coding RNA (lncRNA) Maternally Expressed Gene 3 (Meg3) is encoded within the imprinted Dlk1-Meg3 gene locus and is only maternally expressed. Meg3 has been shown to play an important role in the regulation of cellular proliferation and functions as a tumor suppressor in numerous tissues. Meg3 is highly expressed in mouse adult hematopoietic stem cells (HSCs) and strongly down-regulated in early progenitors. To address its functional role in HSCs, we used MxCre to conditionally delete Meg3 in the adult bone marrow of Meg3mat-flox/pat-wt mice. We performed extensive in vitro and in vivo analyses of mice carrying a Meg3 deficient blood system, but neither observed impaired hematopoiesis during homeostatic conditions nor upon serial transplantation. Furthermore, we analyzed VavCre Meg3mat-flox/pat-wt mice, in which Meg3 was deleted in the embryonic hematopoietic system and unexpectedly this did neither generate any hematopoietic defects. In response to interferon-mediated stimulation, Meg3 deficient adult HSCs responded highly similar compared to controls. Taken together, we report the finding, that the highly expressed imprinted lncRNA Meg3 is dispensable for the function of HSCs during homeostasis and in response to stress mediators as well as for serial reconstitution of the blood system in vivo.

De Novo PITX1 Expression Controls Bi-Stable Transcriptional Circuits to Govern Self-Renewal and Differentiation in Squamous Cell Carcinoma.

Basal tumor propagating cells (TPCs) control squamous cell carcinoma (SCC) growth by self-renewing and differentiating into supra-basal SCC cells, which lack proliferative potential. While transcription factors such as SOX2 and KLF4 can drive these behaviors, their molecular roles and regulatory interactions with each other have remained elusive. Here, we show that PITX1 is specifically expressed in TPCs, where it co-localizes with SOX2 and TRP63 and determines cell fate in mouse and human SCC. Combining genetargeting with chromatin immunoprecipitation sequencing (ChIP-seq) and transcriptomic analysesreveals that PITX1 cooperates with SOX2 and TRP63 to sustain an SCC-specific transcriptional feed-forward circuit that maintains TPC-renewal, while inhibiting KLF4 expression and preventing KLF4-dependent differentiation. Conversely, KLF4 represses PITX1, SOX2, and TRP63 expression toprevent TPC expansion. This bi-stable, multi-inputnetwork reveals a molecular framework that explains self-renewal, aberrant differentiation, and SCCgrowth in mice and humans, providing clues for developing differentiation-inducing therapeutic strategies.

A highly efficient and faithful MDS patient-derived xenotransplantation model for pre-clinical studies

Comprehensive preclinical studies of Myelodysplastic Syndromes (MDS) have been elusive due to limited ability of MDS stem cells to engraft current immunodeficient murine hosts. Here we report a MDS patient-derived xenotransplantation model in cytokine-humanized immunodeficient “MISTRG” mice that provides efficient and faithful disease representation across all MDS subtypes. MISTRG MDS patient-derived xenografts (PDX) reproduce patients’ dysplastic morphology with multi-lineage representation, including erythro- and megakaryopoiesis. MISTRG MDS-PDX replicate the original sample’s genetic complexity and can be propagated via serial transplantation. MISTRG MDS-PDX demonstrate the cytotoxic and differentiation potential of targeted therapeutics providing superior readouts of drug mechanism of action and therapeutic efficacy. Physiologic humanization of the hematopoietic stem cell niche proves critical to MDS stem cell propagation and function in vivo. The MISTRG MDS-PDX model opens novel avenues of research and long-awaited opportunities in MDS research.

The side population enriches for leukemia-propagating cell activity and Wnt pathway expression in zebrafish acute lymphoblastic leukemia.

Cancer stem cells have been strongly linked to resistance and relapse in many malignancies. However, purifying them from within the bulk tumor has been challenging, so their precise genetic and functional characteristics are not well defined. The side population assay exploits the ability of some cells to efflux Hoechst dye via ATP-binding cassette transporters. Stem cells have increased expression of these transporters and this assay has been shown to enrich for stem cells in various tissues and cancers. This study identifies the side population within a zebrafish model of acute lymphoblastic leukemia and correlates the frequency of side population cells with the frequency of leukemia stem cells (more precisely referred to as leukemia-propagating cells within our transplantation model). In addition, the side population within the leukemia evolves with serial transplantation, increasing in tandem with leukemia-propagating cell frequency over subsequent generations. Sorted side population cells from these tumors are enriched for leukemia-propagating cells and have enhanced engraftment compared to sorted non-side population cells when transplanted into syngeneic recipients. RNA-sequencing analysis of sorted side population cells compared to non-side population cells identified a shared expression profile within the side population and pathway analysis yielded Wnt-signaling as the most overrepresented. Gene set enrichment analysis showed that stem cell differentiation and canonical Wnt-signaling were significantly upregulated in the side population. Overall, these results demonstrate that the side population in zebrafish acute lymphoblastic leukemia significantly enriches for leukemia-propagating cells and identifies the Wnt pathway as a likely genetic driver of leukemia stem cell fate.

Hormones induce the formation of luminal-derived basal cells in the mammary gland.

In the mammary gland, it is widely believed that the luminal cells are unipotent after birth, contributing only to the luminal compartment in normal development. Here, by lineage tracing, we uncovered an unexpected potential of luminal cells that can give rise to basal cells during pregnancy. These luminal-derived basal cells (LdBCs) persisted through mammary regression and generated more progeny in successive rounds of pregnancies. LdBCs express basal markers as well as estrogen receptor α (ERα). In ovariectomized (OVX) mice, stimulation with estrogen and progesterone promoted the formation of LdBCs. In serial transplantation assays, LdBCs were able to reconstitute new mammary glands in a hormone-dependent manner. Transcriptome analysis and genetic experiments suggest that Wnt/β-catenin signaling is essential for the formation and maintenance of LdBCs. Our data uncover an unexpected bi-potency of luminal cells in a physiological context. The discovery of ERα+ basal cells, which can respond to hormones and are endowed with stem cell-like regenerative capacity in parous mammary gland, provides new insights into the association of hormones and breast cancer.

USP44 is dispensable for normal hematopoietic stem cell function, lymphocyte development, and B-cell-mediated immune response in a mouse model

Ubiquitin-specific protease 44 (USP44) is a nuclear protein with deubiquitinase (DUB) catalytic activity that has been implicated as an important regulator of cell cycle progression, gene expression, and genomic stability. Dysregulation in the molecular machinery controlling cell proliferation, gene expression, and genomic stability in human or mouse is commonly linked to hematopoietic dysfunction, immunodeficiency, and cancer. We therefore set out to explore the role of USP44 in hematopoietic and immune systems through characterization of a Usp44-deficient mouse model. We report that USP44 is dispensable for the maintenance of hematopoietic stem cell numbers and function under homeostatic conditions, and also after irradiation or serial transplantation. USP44 is also not required for normal lymphocyte development. Usp44-deficient B cells show normal activation, proliferation, and immunoglobulin class switching in response to in vitro stimulation, and Usp44-deficient mice mount normal antibody response to immunization. We also tested the effects of USP44 deficiency on disease progression and survival in the Emu-myc model of mouse B-cell lymphoma and observed a trend toward earlier lethality of Usp44-/- Emu-myc mice; however, this did not reach statistical significance. Overall, we conclude that USP44 is dispensable for the normal physiology of hematopoietic and immune systems, and its functions in these systems are likely redundant with other USP family proteins.

Various Treatment Modalities in Hepatic Hydrothorax: What Is Safe and Effective?

PurposeHepatic hydrothorax is a complication of decompensated liver cirrhosis that is difficult and complex to manage. Data concerning the optimal treatment method, other than liver transplantation, are limited. This study aimed to compare the clinical features and outcomes of patients treated with various modalities, while focusing on surgical management and pigtail drainage.Materials and MethodsForty-one patients diagnosed with refractory hepatic hydrothorax between January 2013 and December 2017 were enrolled.ResultsThe mean Child-Turcotte-Pugh and model for end stage liver disease scores of the enrolled patients were 10.1 and 19.7, respectively. The patients underwent four modalities: serial thoracentesis (n=11, 26.8%), pigtail drainage (n=16, 39.0%), surgery (n=10, 24.4%), and liver transplantation (n=4, 9.8%); 12-month mortality rate/median survival duration was 18.2%/868 days, 87.5%/79 days, 70%/179 days, and 0%/601.5 days, respectively. Regarding the management of refractory hepatic hydrothorax, surgery group required less frequent needle puncture (23.5 times in pigtail group vs. 9.3 times in surgery group), had a lower occurrence of hepatorenal syndrome (50% vs. 30%), and had a non-inferior cumulative overall survival (402.1 days vs. 221.7 days) compared to pigtail group. On multivariate analysis for poor survival, body mass index <19 kg/m2, refractory hepatic hydrothorax not managed with liver transplantation, Child-Turcotte-Pugh score >10, and history of severe encephalopathy (grade >2) were associated with poor survival.ConclusionSerial thoracentesis may be recommended for management of hepatic hydrothorax and surgical management can be a useful option in patients with refractory hepatic hydrothorax, alternative to pigtail drainage.