Immunologic purging of autologous peripheral blood stem cell products based on CD34 and CD133 expression can be effectively and safely applied in half of the acute myeloid leukemia patients

Endomucin marks quiescent long-term multi-lineage repopulating hematopoietic stem cells and is essential for their transendothelial migration

Endomucin (EMCN) currently represents the only hematopoietic stem cell (HSC) marker expressed by both murine and human HSCs. Here, we report that EMCN+ long-term repopulating HSCs (LT-HSCs; CD150+CD48-LSK) have a higher long-term multi-lineage repopulating capacity compared to EMCN- LT-HSCs. Cell cycle analyses and transcriptional profiling demonstrated that EMCN+ LT-HSCs were more quiescent compared to EMCN- LT-HSCs. Emcn-/- and Emcn+/+ mice displayed comparable steady-state hematopoiesis, as well as frequencies, transcriptional programs, and long-term multi-lineage repopulating capacity of their LT-HSCs. Complementary functional analyses further revealed increased cell cycle entry upon treatment with 5-fluorouracil and reduced granulocyte colony-stimulating factor (GCSF) mobilization of Emcn-/- LT-HSCs, demonstrating that EMCN expression by LT-HSCs associates with quiescence in response to hematopoietic stress and is indispensable for effective LT-HSC mobilization. Transplantation of wild-type bone marrow cells into Emcn-/- or Emcn+/+ recipients demonstrated that EMCN is essential for endothelial cell-dependent maintenance/self-renewal of the LT-HSC pool and sustained blood cell production post-transplant.

A promising antitumor method: Targeting CSC with immune cells modified with CAR

Tumors pose a great threat to human health; as a subgroup of tumor cells, cancer stem cells (CSCs) contribute to the genesis, development, metastasis, and recurrence of tumors because of their enhanced proliferation and multidirectional differentiation. Thus, a critical step in tumor treatment is to inhibit CSCs. Researchers have proposed many methods to inhibit or reduce CSCs, including monoclonal antibodies targeting specific surface molecules of CSCs, signal pathway inhibitors, and energy metabolic enzyme inhibitors and inducing differentiation therapy. Additionally, immunotherapy with immune cells engineered with a chimeric antigen receptor (CAR) showed favorable results. However, there are few comprehensive reviews in this area. In this review, we summarize the recent CSC targets used for CSC inhibition and the different immune effector cells (T cells, natural killer (NK) cells, and macrophages) which are engineered with CAR used for CSC therapy. Finally, we list the main challenges and options in targeting CSC with CAR-based immunotherapy. The design targeting two tumor antigens (one CSC antigen and one mature common tumor antigen) should be more reasonable and practical; meanwhile, we highlight the potential of CAR-NK in tumor treatment.

AML/Normal Progenitor Balance Instead of Total Tumor Load (MRD) Accounts for Prognostic Impact of Flowcytometric Residual Disease in AML

Measurable residual disease (MRD) in AML, assessed by multicolor flow cytometry, is an important prognostic factor. Progenitors are key populations in defining MRD, and cases of MRD involving these progenitors are calculated as percentage of WBC and referred to as white blood cell MRD (WBC-MRD). Two main compartments of WBC-MRD can be defined: (1) the AML part of the total primitive/progenitor (CD34+, CD117+, CD133+) compartment (referred to as primitive marker MRD; PM-MRD) and (2) the total progenitor compartment (% of WBC, referred to as PM%), which is the main quantitative determinant of WBC-MRD. Both are related as follows: WBC-MRD = PM-MRD × PM%. We explored the relative contribution of each parameter to the prognostic impact. In the HOVON/SAKK study H102 (300 patients), based on two objectively assessed cut-off points (2.34% and 10%), PM-MRD was found to offer an independent prognostic parameter that was able to identify three patient groups with different prognoses with larger discriminative power than WBC-MRD. In line with this, the PM% parameter itself showed no prognostic impact, implying that the prognostic impact of WBC-MRD results from the PM-MRD parameter it contains. Moreover, the presence of the PM% parameter in WBC-MRD may cause WBC-MRD false positivity and WBC-MRD false negativity. For the latter, at present, it is clinically relevant that PM-MRD ≥ 10% identifies a patient sub-group with a poor prognosis that is currently classified as good prognosis MRDnegative using the European LeukemiaNet 0.1% consensus MRD cut-off value. These observations suggest that residual disease analysis using PM-MRD should be conducted.

PI3K/AKT inhibition reverses R-CHOP resistance by destabilizing SOX2 in diffuse large B cell lymphoma

Up to one-third of diffuse large B cell lymphoma (DLBCL) patients eventually develop resistance to R-CHOP regimen, while the remaining therapeutic options are limited. Thus, understanding the underlying mechanisms and developing therapeutic approaches are urgently needed. Methods: We generated two germinal center B cell-like (GCB) and activated B cell-like (ABC) subtype R-CHO resistant DLBCL cell lines, of which the tumor-initiating capacity was evaluated by serial-transplantation and stemness-associated features including CD34 and CD133 expression, side population and ALDH1 activity were detected by flow cytometry or immunoblotting. Expression profiles of these resistant cells were characterized by RNA sequencing. The susceptibility of resistant cells to different treatments was evaluated by in vitro CytoTox-glo assay and in tumor-bearing mice. The expression levels of SOX2, phos-AKT, CDK6 and FGFR1/2 were detected in 12 R-CHOP-resistant DLBCL clinical specimens by IHC. Results: The stem-like CSC proportion significantly increased in both resistant DLBCL subtypes. SOX2 expression level remarkably elevated in both resistant cell lines due to its phosphorylation by activated PI3K/AKT signaling, thus preventing ubiquitin-mediated degradation. Further, multiple factors, including BCR, integrins, chemokines and FGFR1/2 signaling, regulated PI3K/AKT activation. CDK6 in GCB subtype and FGFR1/2 in ABC subtype were SOX2 targets, whose inhibition potently re-sensitized resistant cells to R-CHOP treatment. More importantly, addition of PI3K inhibitor to R-CHOP completely suppressed the tumor growth of R-CHO-resistant DLBCL cells, most likely by converting CSCs to chemo-sensitive differentiated cells. Conclusions: The PI3K/AKT/SOX2 axis plays a critical role in R-CHOP resistance development and the pro-differentiation therapy against CSCs proposed in this study warrants further study in clinical trials for the treatment of resistant DLBCL.

Relationship between CD34/CD38 and side population (SP) defined leukemia stem cell compartments in acute myeloid leukemia

Leukemic stem cells (LSCs), defined by CD34/CD38 expression, are believed to be essential for leukemia initiation and therapy resistance in acute myeloid leukemia. In addition, the side population (SP), characterized by high Hoechst 33342 efflux, reflecting therapy resistance, has leukemia initiating ability. The purpose of this study is, in both CD34-positive and CD34-negative AML, to integrate both types of LSC compartment into a new more restricted definition. Different CD34/CD38/SP defined putative LSC and normal hematopoietic compartments, with neoplastic or normal nature, respectively, were thus identified after cell sorting, and confirmed by FISH/PCR. Stem cell activity was assessed in the long-term liquid culture stem cell assay. SP fractions harbored the strongest functional stem cell activity in both normal and neoplastic cells in both CD34-positive and CD34-negative AML. Overall, inclusion of SP fraction decreased the size of the putative CD34/CD38 defined LSC compartment by a factor >500. For example, for the important CD34+CD38- LSC compartment, the median SP/CD34+CD38- frequency was 5.1 per million WBC (CD34-positive AML), and median SP/CD34-CD38+ frequency (CD34-negative AML) was 1796 per million WBC. Improved detection of LSC may enable identification of therapy resistant clones, and thereby identification of novel LSC specific, HSC sparing, therapies.

Human adult HSCs can be discriminated from lineage-committed HPCs by the expression of endomucin

EMCN is a novel marker of human HSCs. EMCN is a more specific marker of HSCs than CD34 as it can discriminate HSCs from lineage-committed HPCs.

DNA damage response in CD133 + stem/progenitor cells from umbilical cord blood: low level of endogenous foci and high recruitment of 53BP1

Abstract Purpose: Human hematopoietic stem cells (HSC) are thought to be a major target of radiation-induced leukemogenesis and also provide a relevant cellular model for assessing cancer risk. Cluster of designation 133+ (CD133+) is a marker found in human progenitor and hematopoietic stem cells. Our study examined the repair of radiation-induced DNA double-strand breaks (DSB) in CD133 + umbilical cord blood cells (UCBC).

MATERIALS AND METHODS

After γ-irradiation, endogenous and induced DSB were evaluated in CD133 + UCBC, CD133 - UCBC and peripheral blood lymphocytes (PBL) in terms of phosphorylated histone 2A family member X (γH2AX) and tumor suppressor p53 binding protein 1 (53BP1) foci.

RESULTS

We found that repair signaling in CD133 + UCBC is different from CD133 - UCBC and PBL. These differences include lower endogenous DSB levels and higher 53BP1 recruitment.

CONCLUSIONS

Our data, together with a recent report on radiation-induced γH2AX and 53BP1 foci in CD34 + cells, indicate enhanced DNA repair capacity in HSC as compared to mature lymphocytes.

CD133-Positive Hematopoietic Stem Cells: From Biology to Medicine

Lifelong hematopoiesis is sustained by a very small number of hematopoietic stem cells capable of self-renewal and differentiation into multiple hematopoietic lineages. The sialomucin CD34 has been, and is currently, used for the identification and purification of primitive hematopoietic progenitors. Depending on the source of stem cells, CD34 may not be expressed on all progenitor cells. An alternative stem cell marker is prominin-1 (CD133), which is expressed on a subpopulation of CD34(+) cells as well as on CD34(-) progenitor cells derived from various sources including fetal liver and bone marrow, adult bone marrow, cord blood, and mobilized peripheral blood. CD133(+) stem cells can reconstitute myelo- and lymphopoiesis of lethally irradiated mice, and the characterization of the CD133 expression on stem cells provides some insights into the biology of the hierarchy and functional organization of human hematopoiesis. The availability of methods for clinical large-scale isolation of CD133(+) cells facilitates their use in autologous and allogeneic hematopoietic stem cell transplantation and possibly in other fields of regenerative medicine.

Oncolytic virotherapy for hematological malignancies

Hematological malignancies such as leukemias, lymphomas, multiple myeloma (MM), and the myelodysplastic syndromes (MDSs) primarily affect adults and are difficult to treat. For high-risk disease, hematopoietic stem cell transplant (HCT) can be used. However, in the setting of autologous HCT, relapse due to contamination of the autograft with cancer cells remains a major challenge. Ex vivo manipulations of the autograft to purge cancer cells using chemotherapies and toxins have been attempted. Because these past strategies lack specificity for malignant cells and often impair the normal hematopoietic stem and progenitor cells, prior efforts to ex vivo purge autografts have resulted in prolonged cytopenias and graft failure. The ideal ex vivo purging agent would selectively target the contaminating cancer cells while spare normal stem and progenitor cells and would be applied quickly without toxicities to the recipient. One agent which meets these criteria is oncolytic viruses. This paper details experimental progress with reovirus, myxoma virus, measles virus, vesicular stomatitis virus, coxsackievirus, and vaccinia virus as well as requirements for translation of these results to the clinic.

Combined characterization of microRNA and mRNA profiles delineates early differentiation pathways of CD133+ and CD34+ hematopoietic stem and progenitor cells

MicroRNAs (miRNAs) have been shown to play an important role in hematopoiesis. To elucidate the role of miRNAs in the early steps of hematopoiesis, we directly compared donor-matched CD133⁺ cells with the more differentiated CD34⁺CD133⁻ and CD34⁻CD133⁻ cells from bone marrow on the miRNA and mRNA level. Using quantitative whole genome miRNA microarray and sequencing-based profiling, we found that between 109 (CD133⁺) and 216 (CD34⁻CD133⁻) miRNAs were expressed. Quantification revealed that the 25 highest expressed miRNAs accounted for 73% of the total miRNA pool. miR-142-3p was the highest expressed miRNA with up to 2,000 copies per cell in CD34⁺CD133⁻ cells. Eighteen miRNAs were significantly differentially expressed between CD133⁺ and CD34⁺CD133⁻ cells. We analyzed their biological role by examining the coexpression of miRNAs and its bioinformatically predicted mRNA targets and luciferase-based reporter assays. We provide the first evidence for a direct regulation of CD133 by miR-142-3p as well as tropomyosin 1 and frizzled homolog 5 by miR-29a. Overexpression of miRNAs in CD133⁺ cells demonstrated that miR-142-3p has a negative influence on the overall colony-forming ability. In conclusion, the miRNAs expressed differentially between the CD133⁺ and CD34⁺CD133⁻ cells are involved in inhibition of differentiation, prevention of apoptosis, and cytoskeletal remodeling. These results are highly relevant for stem cell-based therapies with CD133⁺ cells and delineate for the first time how the stem cell character of CD133⁺ cells is defined by the expression of specific miRNAs. Stem Cells 2011;29:847–857

Surgical Therapy of End-Stage Heart Failure: Understanding Cell-Mediated Mechanisms Interacting with Myocardial Damage

Worldwide, cardiovascular disease results in an estimated 14.3 million deaths per year, giving rise to an increased demand for alternative and advanced treatment. Current approaches include medical management, cardiac transplantation, device therapy, and, most recently, stem cell therapy. Research into cell-based therapies has shown this option to be a promising alternative to the conventional methods. In contrast to early trials, modern approaches now attempt to isolate specific stem cells, as well as increase their numbers by means of amplifying in a culture environment. The method of delivery has also been improved to minimize the risk of micro-infarcts and embolization, which were often observed after the use of coronary catheterization. The latest approach entails direct, surgical, transepicardial injection of the stem cell mixture, as well as the use of tissue-engineered meshes consisting of embedded progenitor cells.

CD133+ cell content does not influence recovery time after hematopoietic stem cell transplantation

BACKGROUND

Infusion of an adequate dose of CD34+ mononuclear hematopoietic stem cells (HSCs) is the single most important variable to assure success in hematopoietic grafting. CD133+ HSCs constitute the CD34+ subgroup with higher differentiation potential. The number of granulocyte-colony-stimulating factor (G-CSF)-mobilized CD133+ HSCs administered during hematopoietic grafting and its relationship with the number of days needed to regain hematopoiesis was determined.

STUDY DESIGN AND METHODS

Thirty-eight patients with malignant hematologic diseases who received an autologous (n = 15) or allogeneic (n = 23) HSC transplant were prospectively evaluated. G-CSF was administered for 5 days at 10 microg/kg/day. Hematopoietic progenitors were recovered from peripheral blood on day 5 by leukopheresis. CD34+ and CD133+/CD34+ cell populations were quantified by flow cytometry; the number of days to hematologic recovery was documented.

RESULTS

A median dose of 4.56 x 10(6)/kg CD34+ HSCs (range, 1.35 x 10(6)-14.6 x 10(6)) was recovered and transplanted; of these grafted cells, a median 3.25 x 10(6) were also CD133+ (range, 1.25 x 10(6)-14.3 x 10(6)). In the autologous group, the median number of days to reach a platelet (PLT) count of 20 x 10(9)/L or greater was 12, and 15 days to obtain a neutrophil count of 0.5 x 10(9)/L or greater; in the allogeneic group 13 and 16 days, respectively, were required (p > 0.05). A median 76.5% of G-CSF-mobilized CD34+ HSCs coexpressed the CD133+ antigen (range, 23.1-97.9).

CONCLUSIONS

A higher number of CD133+/CD34+ HSCs in the graft was not clearly associated with a shorter neutrophil or PLT recovery time in either allogeneic or autologous recipients.

AC133 expression in egyptian children with acute leukemia: impact on treatment response and disease outcome

AC133 antigen is expressed restrictively in the immature subset of the CD34 cells. Hence, it is expected to be a valuable prognostic marker in acute leukemia. Sixty Egyptian children with acute leukemia were enrolled into this prospective study divided into 2 groups: 30 acute myeloblastic leukemia (AML) and 30 acute lymphoblastic leukemia (ALL) patients. Flow cytometric assessment of AC133 expression was performed on CD34 blast cells. AC133 was expressed in 66.7% and 40% of AML and ALL patients, respectively. AC133-positive expression was not associated with any of the studied standard prognostic factors. In AML, 80% of patients with poor clinical outcome (relapse or death) were positive for AC133 expression, whereas, all ALL patients who developed resistance as well as those who displayed poor clinical outcome had AC133-positive expression (P<0.05). Patients with positive AC133 expression had significantly shorter overall and disease-free survival times compared with AC133-negative patients in both ALL (P<0.001) and AML (P<0.05) groups. AC133 expression percentage was a reliable poor prognostic marker in ALL patients (P<0.0001). AC133-positive expression is an independent poor prognostic factor in childhood acute leukemia and could characterize a group of patients with resistance to standard chemotherapy, as well as high incidence of relapse and death.

CD133-2 (AC141) expression analysis in acute leukemia immunophenotyping in correlation to CD34 and P-glycoprotein

A total of 49 newly diagnosed patients with acute leukemia were studied in order to assess the diagnostic value of clone AC141 of CD133 antibody by flow cytometry. AC141 expression was further compared to CD34 and P-glycoprotein, immunophenotype, morphology and cytogenetic/molecular data. Flow cytometry allowed for the detection of AC141 expression in 42.8% of the patients. A strong correlation with myeloid lineage was observed. All AC141(+) acute myeloid leukemia (AML) cases were of immature morphology and a strong concordance with CD34 expression was found. However, discordant patterns were also observed. Besides, AC141 expression correlated with CD7 in the absence of mature markers (CD14, CD15 and CD64). Similarly to CD34, P-glycoprotein levels were also significantly higher in AC141(+) AML cases. No correlation was found with cytogenetic/molecular data of the patients. In conclusion, membrane expression of AC141, in combination with other antigens, might facilitate a more precise immunologic characterization of acute leukemias and may serve as an alternative to CD34 for purging purposes in selected patients.

Positive selection for CD90 as a purging option in acute myeloid leukemia stem cell transplants

BACKGROUND

Several studies showed the benefit of purging of acute myeloid leukemia (AML) stem cell transplants. We reported previously that purging by positive selection of CD34+ and CD133+ cells resulted in a 3-4 log tumor cell reduction (TCR) in CD34- and/or CD133- AML, but has been shown to be potentially applicable in only about 50% of cases. Similar to CD34 and CD133, CD90 marks the hematopoietic CD34 positive stem cells capable of full hematopoietic recovery after myeloablative chemotherapy, and therefore, in the present study, we explored whether a similar purging approach is possible using CD90.

METHODS

CD90 expression was established by flowcytometry in diagnosis AML on the clonogenic AML CD34+ blast population by flow cytometry. Positivity was defined as >3% CD90 (CD34+) expression on blasts. For the calculation of the efficacy of TCR by positive selection, AML blasts were recognized by either prelabeling diagnosis blasts with CD45-FITC in spiking model experiments or using expression of leukemia associated marker combinations both in spiking experiments and in real transplants.

RESULTS

In 119 patients with AML and myelodysplastic syndrome, we found coexpression of CD34 and CD90 (>3%) in 42 cases (35%). In AML patients 60 years or younger, representing the patients who are eligible for transplantation, only 23% (16/69) of the patients showed CD90 expression. Positive selection for CD90 in transplants containing CD90 negative AML resulted in a 2.8-4 log TCR in the models used.

CONCLUSIONS

Purging by positive selection using CD90 can potentially be applied effectively in the majority of AML patients 60 years or younger.

Viral purging of haematological autografts: should we sneeze on the graft?

High-dose cytotoxic chemotherapy followed by autologous haematopoietic stem cell transplantation (ASCT) is extensively used for the treatment of many haematopoietic, as well as several epithelial cancers. Disease relapse may be the result of tumour contamination within autograft as evidenced by gene marking studies. The multiple purging strategies that have been described to date have not proven effective in most ASCT settings. This review addresses the possibility of using oncolytic viruses as a novel purging strategy. DNA viruses such as genetically engineered adenoviral vectors have widely been used to deliver either a prodrug-activating enzyme or express wild-type p53 selectively in tumour cells in ex vivo purging protocols. In addition, conditionally replicating adenoviruses that selectively replicate in tumour cells and herpes simplex virus type 1 are other DNA viruses that have been tested as ex vivo purging agents under laboratory conditions. Vesicular stomatitis virus (VSV) and reovirus are naturally occurring RNA viruses that appear to hold promise as purging agents under ex vivo and in vivo settings. Preclinical data demonstrate reovirus's purging potential against breast, monocytic and myeloma cell lines as well as patient-derived tumours of diffuse large B-cell lymphoma, chronic lymphocytic leukaemia, Waldenstrom macroglobulinemia and small lymphocytic lymphoma. In addition, VSV has shown effective killing of leukaemic cell lines and multiple myeloma patient specimens. Given the increasing interest in the utilization of viruses as purging agents, the following review provides a timely summary of the potential and the challenges of oncolytic viruses as purging modalities during ASCT.

Transcriptional Profiling Reflects Shared and Unique Characters for CD34+and CD133+Cells

CD34 and CD133 are the most commonly used markers to enrich hematopoietic stem cells (HSCs). Positively selected HSCs are increasingly used for autologous and allogeneic transplantation, yet the biological properties of CD34(+) and CD133(+) cells are largely unknown. In the present study, a genome-wide gene expression analysis of human cord blood (CB)-derived CD34(+) cells was performed. The CD34(+) gene expression profile was compared to an identically constructed CD133(+) gene expression profile to reveal the specific expression patterns and major differences of CD34(+) and CD133(+) cells. As expected, many genes were similarly expressed in the two cell populations, but cell-type-specific gene expression was also demonstrated. Self-organizing map analysis was used to identify transcripts having similar expression patterns, and the results were compared between CD34(+) and CD133(+) cells. Also, a prioritization algorithm was used to rank the genes best separating CD34(+) and CD133(+) cells from their CD34() and CD133() counterparts in CB. Our results show that CD133(+) cells have higher numbers of up-regulated genes than CD34(+) cells. Furthermore, the uniquely expressed genes in CD34(+) or CD133(+) cell populations were associated with different biological processes. CD34(+) cells overexpressed many transcripts associated with development and response to stress or external stimuli. In CD133(+) cells, the most significantly represented biological processes were establishment and maintenance of chromatin architecture, DNA metabolism, and cell cycle. The differences between the gene expression profiles of CD34(+) and CD133(+) cells indicate the more primitive nature of CD133(+) cells. These profiles suggest that CD34(+) and CD133(+) cells may have different roles in hematopoietic regeneration.

Ex vivo expansion of G-CSF-mobilized peripheral blood CD133+ progenitor cells on coculture with human stromal cells

OBJECTIVE

The pentaspan molecule CD133 has been shown to be a marker of more primitive hematopoietic progenitors in mobilized peripheral blood (PB). Our objective was to assess the efficacy of PB CD133(+) cells in our coculture system using human telomerized stromal (HTS) cells.

METHODS

Five thousand PB CD133(+) cells or conventional cord blood (CB) CD34(+) cells were expanded with or without HTS cells in the presence or absence of stem cell factor, thrombopoietin, and Flk-2/Flt-3 ligand.

RESULTS

The coculture was significantly superior in expanding PB clonogenic cells as compared with the stroma-free culture (CFU-C, 2 +/- 0 vs 111 +/- 15-fold of initial cell number, p < 0.01), and the fold increase of PB clonogenic cells was comparable to that for CB cells after two weeks of coculture (BFU-E, 54 +/- 3 vs 56 +/- 4-fold; CFU-GM, 156 +/- 26 vs 83 +/- 9-fold; CFU-Mix, 30 +/- 11 vs 80 +/- 36-fold). However, proliferation of CFU-Mk from PB on coculture with HTS cells was modest as compared with stroma-free culture. Concomitantly, multiple hematopoietic cells transmigrated below the stromal layer and formed cobblestone areas (CAs). The production of hematopoietic progenitor cells from CAs after coculture with PB was significantly lower than that seen in cells cocultured with CB for four weeks (CFU-Mix, 0 +/- 0 vs 9 +/- 5-fold on day 28, p < 0.01), although a similar number of CAs derived from PB and CB were observed.

CONCLUSION

PB CD133(+) cells proliferated efficiently above the stromal layer, while the characteristics of PB CD133(+) cells underneath the human stromal layer were likely to be maintained, even after long-term hematopoietic-stromal interaction.