Helios expression in regulatory T cells promotes immunosuppression, angiogenesis and the growth of leukemia cells in pediatric acute lymphoblastic leukemia

Regulatory T cells (Tregs) characterized by the transcription factor forkhead box P3 (FoxP3) are crucial for maintaining immune tolerance and preventing autoimmunity. However, FoxP3 does not function alone and Helios is considered a potential candidate for defining Treg subsets. In this study, we investigated the expression and function of Helios for identifying Tregs in childhood precursor B-cell acute lymphoblastic leukemia (pre-B ALL). Our results demonstrated that patients with pre-B ALL had a higher percentage of Helios⁺ FoxP3⁺ CD4⁺ Tregs. And there was a positive correlation between the expression of Helios and the suppressive function of Tregs, the risk gradation of ALL. Helios in combination with CD4 and FoxP3 may be an effective way to detect functional Tregs in pre-B ALL by promoting the secretion of transforming growth factor (TGF)-β1. Furthermore, Helios⁺ Tregs could regulate angiogenesis in the BM niche of pre-B ALL via the VEGFA/VEGFR2 pathway. We also found Helios⁺ Tregs decreased apoptosis rate of nalm-6 cells by up-regulating the expression of anti-apoptosis protein Bcl-2. In summary, these data strongly imply the physiological importance of Helios expression in Tregs, and suggest that the manipulation of Helios may serve as a novel strategy for cancer immunotherapy.

RAC2, AEP, and ICAM1 expression are associated with CNS disease in a mouse model of pre-B childhood acute lymphoblastic leukemia

We developed a murine model of CNS disease to obtain a better understanding of the pathogenesis of CNS involvement in pre-B-cell acute lymphoblastic leukemia (ALL). Semiquantitative proteomic discovery-based approaches identified unique expression of asparaginyl endopeptidase (AEP), intercellular adhesion molecule 1 (ICAM1), and ras-related C3 botulinum toxin substrate 2 (RAC2), among others, in an invasive pre-B-cell line that produced CNS leukemia in NOD-SCID mice. Targeting RAC2 significantly inhibited in vitro invasion and delayed disease onset in mice. Induced expression of RAC2 in cell lines with low/absent expression of AEP and ICAM1 did not result in an invasive phenotype or murine CNS disease. Flow cytometric analysis identified an enriched population of blast cells expressing ICAM1/lymphocyte function associated antigen-1 (LFA-1)/CD70 in the CD10(+)/CD19(+) fraction of bone marrow aspirates obtained from relapsed compared with normal controls and those with primary disease. CD10(+)/CD19(+) fractions obtained from relapsed patients also express RAC2 and give rise to CNS disease in mice. Our data suggest that combinations of processes are involved in the pathogenesis of CNS disease in pre-B-cell ALL, support a model in which CNS disease occurs as a result of external invasion, and suggest that targeting the processes of adhesion and invasion unique to pre-B cells may prevent recurrences within the CNS.

Altered glucose metabolism in childhood pre-B acute lymphoblastic leukaemia

The cells of solid tumours are known to have an altered metabolism, with high rates of glucose uptake and glycolysis, which results in the excessive production of lactate. To date there has been no definitive research documenting metabolic changes in acute lymphoblastic leukaemia (ALL) cells. In order to investigate whether ALL cells have an altered metabolism, we initially compared the transcriptional profiles of 22 specimens from paediatric patients diagnosed with ALL to five CD34+ specimens isolated from bone marrow, which was verified in an independent cohort of 101 specimens. Profiling revealed the upregulation of genes facilitating glycolysis in the ALL specimens compared to the CD34+ specimens, while those involved in the tricarboxylic acid cycle were downregulated. Functional studies supported the microarray findings threefold: (1) higher expression of the glucose transport protein glucose transporter 1 in ALL compared to CD34+ specimens, (2) the excessive production of lactate in ALL cell lines and (3) sensitivity of ALL cell lines to the glycolysis inhibitor 2-deoxy-D-glucose. While metabolic alterations have been well documented in solid tumours, this is the first study to provide direct evidence for the existence of metabolic changes in the leukaemic cells of ALL patients. The finding offers new options for targeted therapy for ALL patients.

Dual Role of the Adaptor Protein SLP-65: Organizer of Signal Transduction and Tumor Suppressor of Pre-B Cell Leukemia

B cell development is characterized by a coordinated progression through defined stages that are controlled at several checkpoints. Signals from the pre-B cell receptor (pre-BCR) are essential for regulated transition from the pre-B cell stage. The adaptor protein SLP-65 plays a key role in this signaling pathway. Recent findings indicate an additional function of SLP-65 as a tumor suppressor that regulates pre-B cell proliferation. We will discuss here the potential mechanisms by which SLP-65 controls the pre-B cell checkpoint.

Chemotherapy dosing with elevated liver function test results in acute leukemia

OBJECTIVE

To report a case of massive blast infiltration of the liver by acute lymphoblastic leukemia (ALL) manifested by worsening liver function test (LFT) results and concern over how to dose chemotherapy in this patient.

CASE SUMMARY

A 36-year-old male presenting with productive cough, abdominal pain, and lower back pain was diagnosed with pre-B cell ALL. Of note, the patient developed worsening LFT results within the first few days of diagnosis. Because of concern over increasing liver dysfunction and the need to administer vincristine and daunorubicin with induction therapy, a transvenous liver biopsy was performed, revealing massive lymphoblast infiltration.

DISCUSSION

A short course of prednisone was given to determine whether the LFT abnormalities would reverse with treatment. Once a downward trend in the abnormalities was noted, full-dose induction chemotherapy was administered.

CONCLUSIONS

It is important to discern the cause of elevated LFT values in patients with acute leukemia who require induction chemotherapy, as this may affect treatment decisions and patient outcomes.

Dok1 and SHIP act as negative regulators of v-Abl-induced pre-B cell transformation, proliferation and Ras/Erk activation

The v-Abl tyrosine kinase activates several signaling pathways during transformation of bone marrow cells in mice. Because the SH2-containing inositol 5'-phosphatase (SHIP) and Downstream of tyrosine kinase 1 (Dok1) have been shown to interact with Abl, the effect of SHIP and Dok1 deficiency on v-Abl transformation was investigated. Bone marrow cells from either Dok1- or SHIP-deficient mice are more susceptible to transformation by v-Abl. v-Abl-transformed preB cells from these knockout mice show Abl kinase-dependent hyperproliferation and moderate resistance to apoptosis. Elevated activation of Ras, Raf-1, and Erk, but not of Akt, was observed in either SHIP(-/-) or Dok1(-/-) v-Abl-transformed cells. This activation is sensitive to treatment with STI571. Furthermore, treatment of these cells with either a farnesyltransferase inhibitor or a MEK1/2 inhibitor abrogates the increased proliferation of SHIP(-/-) or Dok1(-/-) cells in a dose-dependent manner. Complementation of SHIP(-/-) or Dok1(-/-) cells abrogates their hyperproliferation and intracellular Erk activation. These data indicate that both SHIP and Dok1 functionally regulate the activation of Ras-Erk pathway by v-Abl and affect the mitogenic activity of v-Abl transformed bone marrow cells.

TGF-beta and its receptor complex in leukemic B-cell precursors

Transforming growth factor beta (TGF-beta) is a highly conserved peptide with growth-inhibitory activity in multiple normal and transformed cell types. Signal transduction is mediated through the receptor complex, consisting of two active seronine or threonine kinases (TGF-beta-receptor I and II) and the receptor-associated proteins betaglycan (TGF-beta-receptor III) and endoglin. In this study, we assessed the analysis of the role of TGF-beta and the transcription of the genes for TGF-beta and its receptor in highly purified leukemic B-cell precursors (BCPs) of patients with common acute lymphoblastic leukemia (cALL). Leukemic BCPs were positive for gene transcription of TGF-beta (9/9), the TGF-beta-receptor I (9/9), the TGF-beta-receptor II (6/6), betaglycan (5/6), and endoglin (6/6). Incubation with TGF-beta significantly reduced the cell viability of leukemic BCPs by a mean of 45% (p = 0.0009). The reduction of cell viability was associated with the induction of apoptosis by a mean of 31%. TGF-beta caused significant suppression of the S phase (p = 0.002) and accumulation in the G0/G1 phase (p = 0.0005). It also reduced expression of the adhesion surface receptor CD18 and the Fas antigen CD95 from 58% to 40% and from 48% to 27%, respectively. The data indicate that TGF-beta is a negative growth signal in leukemic BCPs and point to an additional role of TGF-beta as an immunomodulatory cytokine, suggesting a complex role of TGF-beta in the leukemogenesis of cALL.

The evolution of B precursor leukemia in the Emu-ret mouse

Emu-ret mice carrying an RFP/RET fusion gene under the transcriptional control of the immunoglobulin heavy chain enhancer develop B lineage leukemias/lymphomas. We have characterized B-cell development in these mice before the onset of clinical disease to determine the steps involved in leukemogenesis. Flow cytometry reveals that the CD45R+CD43(+)CD24(+)BP-1(+) late pro-B-cell population is markedly expanded in the bone marrow of 3- to 5-week-old Emu-ret mice. Compared with late pro-B cells from transgene-negative mice, Emu-ret late pro-B cells have a limited capacity to differentiate in interleukin (IL)-7 and a higher incidence of VDJ rearrangements, but a similar cell cycle profile. In contrast, CD45R+CD43(+)CD24(+)BP-1(-) early pro-B cells from 3- to 5-week-old Emu-ret mice, which also express the RFP/RET transgene, differentiate in IL-7 similarly to their normal counterparts. Furthermore, early pro-B cells from Emu-ret and transgene-negative mice have an identical pattern of growth inhibition when exposed to interferons (IFNs)-alpha/beta and -gamma, whereas, pro-B-cell leukemia lines derived from Emu-ret mice are markedly less sensitive to growth inhibition by these IFNs. In 13-week-old well-appearing Emu-ret mice, late pro-B cells upregulate CYCLIN D1 expression and downregulate CASPASE-1 expression in a pattern that correlates with the emergence of B precursor cells in the peripheral blood and the loss of other B lineage subsets in the bone marrow. Taken together, these results suggest that the expression of the RFP/RET transgene initially prevents the normal elimination of late pro-B cells with nonproductive rearrangements. Secondary events that simultaneously disturb the normal transcriptional regulation of genes involved in the control of the cell cycle and apoptosis may allow for subsequent malignant transformation within the expanded late pro-B-cell population.

Expression of an abnormal sized c-kit transcript in Hong Kong Chinese acute lymphoblastic leukaemia patients

Blast cells from a majority of acute myelogenous leukaemia (AML) patients express c-kit mRNA. However, c-kit expression has not been observed in patients with acute lymphoblastic leukaemia (ALL) and lymphoproliferative disease. We report here the detection of an abnormal sized c-kit mRNA in two Hong Kong Chinese patients with pre-B ALL and common ALL.

Human bone marrow stromal cell contact and soluble factors have different effects on the survival and proliferation of paediatric B-lineage acute lymphoblastic leukaemic blasts

Recent studies have confirmed that in vitro viability and proliferation of precursor B-cell leukaemia (ALL) cells are linked to the presence of bone marrow derived stromal cells. To investigate whether this effect is mediated by direct contact or through the action of soluble factors, using a method we have recently described, the growth parameters of ALL bone marrow blast cells from eight newly diagnosed patients were determined with the lipophilic fluorescent probe PKH 26 GL. The viability of ALL cells and the rate of cell division in cultures containing either medium alone; stromal cell conditioned medium; stromal cell layers allowing direct contact, or in 0.4 microns microporous membrane cultures suspended above stromal cell layers were examined. In all eight samples an improved maintenance of ALL cells in a viable state in cultures containing bone marrow stromal cells was observed. The survival of leukaemic cells was equivalent in 0.4 microns microporous membrane cultures suspended above stromal cell layers and in cultures of leukaemic cells in direct contact with stromal cell layers. It was thus demonstrated that this effect was mediated by the action of soluble factor(s) present in these cultures. However, the improved maintenance of ALL cells in a viable state was observed in only one of the eight cases when ALL cells were cultured in stromal cell conditioned medium alone. The highest rate of cell division of leukaemic cells was observed in ALL cells in direct contact with bone marrow stromal cells. The activities of stromal cell derived soluble factors could not be reproduced by recombinant forms of likely candidate factors including IL-1 beta, IL-4, IL-6, IL-7, SCF, TNF alpha, TGF beta, LIF, NGF or a mixture of these factors when examined in cultures of the same patient samples. This study implicates the existence of a novel bone marrow derived factor(s) that improves survival of ALL cells in vitro.

LAMA tumor in the rat as an experimental model for pre-B-cell leukemia

A late pre-B-cell leukemia model in the rat, the LAMA tumor, is described. A mouse monoclonal antibody (HIS30) was developed against LAMA cells. HIS30 reacts with a membrane antigen in tumor tissue, whereas its reactivity with normal tissues is limited to the zona glomerulosa of the adrenal cortex and to the adrenal medulla. HIS30 was used for both the immunohistological detection of tumor cells in tissue sections and the immunolocalization of tumor cells in vivo. To enable in vitro studies with the LAMA model, an in vitro growing cell line (LAMA-K1) was established from the LAMA tumor. LAMA-K1 is immunophenotypically similar to the original tumor. Two tumor transplantation models were characterized. In the first model LAMA was implanted s.c., and local tumor growth occurred at the injection site, which was then followed by lymphatogenic and subsequently hematogenic tumor spread. In the second model i.v. transplantation caused direct hematogenic tumor dissemination. In both models early dissemination was especially prominent to the bone marrow, spleen, and liver. Later in the disease most visceral organs became involved, and partial paralysis of the animal was observed in the end stage of the disease. In combination with HIS30, the LAMA pre-B-cell tumor offers a model for both the investigation of in vivo transplanted tumor cells and for the in vivo detection of tumor cells by HIS30 in LAMA tumor-bearing rats.

Characterization of cytoplasmic and nuclear polypeptides induced by interferon-gamma in a murine pre-B cell leukemia

The effects of interferon-gamma (IFN-gamma) on protein synthesis of a pre-B cell leukemia, L1210, have been studied by two-dimensional gel electrophoresis. In total cell extracts, at least ten proteins were induced de novo, or increased in their expression, after an 18-h IFN-gamma treatment, whereas in the nuclear extracts eight proteins were specifically induced. Of these, increased synthesis of a 40-kDa/pI 5.9 cytoplasmic protein was the most prominent and reproducible. Most of these proteins appear to be specific for a defined step of differentiation, since they are not found in other B cell leukemias upon IFN-gamma treatment. Others appear to be tissue specific, since they are not induced in fibroblasts nor in T cells. In addition, synthesis of some of the induced proteins appeared to require rapid transcription of new mRNA, because actinomycin D markedly inhibited their formation when added immediately before IFN-gamma. In keeping with this finding, in vitro translation of mRNA from IFN-gamma-treated L1210 cells into a rabbit reticulocyte lysate system, followed by analysis of the labeled proteins by two-dimensional gel electrophoresis, revealed the appearance of at least seven proteins. Taken as a whole, these results demonstrate that in leukemic pre-B cells IFN-gamma induces the transcriptional activation of genes coding for cytoplasmic and nuclear proteins, some of which could be employed as specific cell activation markers.