Silencing of GATA3 defines a novel stem cell-like subgroup of ETP-ALL

Background

GATA3 is pivotal for the development of T lymphocytes. While its effects in later stages of T cell differentiation are well recognized, the role of GATA3 in the generation of early T cell precursors (ETP) has only recently been explored. As aberrant GATA3 mRNA expression has been linked to cancerogenesis, we investigated the role of GATA3 in early T cell precursor acute lymphoblastic leukemia (ETP-ALL).

Methods

We analyzed GATA3 mRNA expression by RT-PCR (n = 182) in adult patients with T-ALL. Of these, we identified 70 of 182 patients with ETP-ALL by immunophenotyping. DNA methylation was assessed genome wide (Illumina Infinium® HumanMethylation450 BeadChip platform) in 12 patients and GATA3-specifically by pyrosequencing in 70 patients with ETP-ALL. The mutational landscape of ETP-ALL with respect to GATA3 expression was investigated in 18 patients and validated by Sanger sequencing in 65 patients with ETP-ALL. Gene expression profiles (Affymetrix Human genome U133 Plus 2.0) of an independent cohort of adult T-ALL (n = 83) were used to identify ETP-ALL and investigate GATA3^low and GATA3^high expressing T-ALL patients. In addition, the ETP-ALL cell line PER-117 was investigated for cytotoxicity, apoptosis, GATA3 mRNA expression, DNA methylation, and global gene expression before and after treatment with decitabine.

Results

In our cohort of 70 ETP-ALL patients, 33 % (23/70) lacked GATA3 expression and were thus defined as GATA3^low. DNA methylation analysis revealed a high degree of GATA3 CpG island methylation in GATA3^low compared with GATA3^high ETP-ALL patients (mean 46 vs. 21 %, p < 0.0001). Genome-wide expression profiling of GATA3^low ETP-ALL exhibited enrichment of myeloid/lymphoid progenitor (MLP) and granulocyte/monocyte progenitor (GMP) genes, while T cell-specific signatures were downregulated compared to GATA3^high ETP-ALL. Among others, FLT3 expression was upregulated and mutational analyses demonstrated a high rate (79 %) of FLT3 mutations. Hypomethylating agents induced reversal of GATA3 silencing, and gene expression profiling revealed downregulation of hematopoietic stem cell genes and upregulation of T cell differentiation.

Conclusions

We propose GATA3^low ETP-ALL as a novel stem cell-like leukemia with implications for the use of myeloid-derived therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0324-8) contains supplementary material, which is available to authorized users.

Systematic chemical and molecular profiling of MLL-rearranged infant acute lymphoblastic leukemia reveals efficacy of romidepsin

To address the poor prognosis of mixed lineage leukemia (MLL)-rearranged infant acute lymphoblastic leukemia (iALL), we generated a panel of cell lines from primary patient samples and investigated cytotoxic responses to contemporary and novel Food and Drug Administration-approved chemotherapeutics. To characterize representation of primary disease within cell lines, molecular features were compared using RNA-sequencing and cytogenetics. High-throughput screening revealed variable efficacy of currently used drugs, however identified consistent efficacy of three novel drug classes: proteasome inhibitors, histone deacetylase inhibitors and cyclin-dependent kinase inhibitors. Gene expression of drug targets was highly reproducible comparing iALL cell lines to matched primary specimens. Histone deacetylase inhibitors, including romidepsin (ROM), enhanced the activity of a key component of iALL therapy, cytarabine (ARAC) in vitro and combined administration of ROM and ARAC to xenografted mice further reduced leukemia burden. Molecular studies showed that ROM reduces expression of cytidine deaminase, an enzyme involved in ARAC deactivation, and enhances the DNA damage-response to ARAC. In conclusion, we present a valuable resource for drug discovery, including the first systematic analysis of transcriptome reproducibility in vitro, and have identified ROM as a promising therapeutic for MLL-rearranged iALL.

A novel BRD4-NUT fusion in an undifferentiated sinonasal tumor highlights alternative splicing as a contributing oncogenic factor in NUT midline carcinoma

NUT midline carcinoma (NMC) is a fatal cancer that arises in various tissues along the upper midline of the body. The defining molecular feature of NMC is a chromosomal translocation that joins (in the majority of cases) the nuclear testis gene NUT (NUTM1) to the bromodomain protein family member 4 (BRD4) and thereby creating a fusion oncogene that disrupts cellular differentiation and drives the disease. In this study, we report the case of an adolescent NMC patient presenting with severe facial pain, proptosis and visual impairment due to a mass arising from the ethmoid sinus that invaded the right orbit and frontal lobe. Treatment involved radical resection, including exenteration of the affected eye with the view to consolidate treatment with radiation therapy; however, the patient experienced rapid tumor progression and passed away 79 days post resection. Molecular analysis of the tumor tissue identified a novel in-frame BRD4-NUT transcript, with BRD4 exon 15 fused to the last 124 nucleotides of NUT exon 2 (BRD4-NUT ex15:ex2_Δnt1–585). The partial deletion of NUT exon 2 was attributed to a mid-exonic genomic breakpoint and the subsequent activation of a cryptic splice site further downstream within the exon. Inhibition of the canonical 3′ acceptor splice site of NUT intron 1 in cell lines expressing the most common NMC fusion transcripts (PER-403, BRD4-NUT ex11:ex2; PER-624, BRD4-NUT ex15:ex2) induced alternative splicing from the same cryptic splice site as identified in the patient. Detection of low levels of an in-frame BRD4-NUT ex11:ex2_Δnt1–585 transcript in PER-403 confirmed endogenous splicing from this alternative exon 2 splice site. Although further studies are necessary to assess the clinical relevance of the increasing number of variant fusions described in NMC, the findings presented in this case identify alternative splicing as a mechanism that contributes to this pathogenic complexity.

Novel CT domain-encoding splice forms of CTGF/CCN2 are expressed in B-lineage acute lymphoblastic leukaemia

INTRODUCTION

Connective tissue growth factor (CTGF/CCN2) has been shown previously to be aberrantly expressed in a high proportion of paediatric precursor B cell acute lymphoblastic leukaemia (pre-B ALL), suggesting a potential oncogenic role in this tumour type. We therefore assessed CTGF mRNA transcript diversity in B-lineage ALL using primary patient specimens and cell lines.

METHODS

CTGF mRNA expression was evaluated by quantitative real-time PCR and Northern blotting. We performed a structural analysis of CTGF mRNA by nested reverse-transcriptase PCR and examined CTGF protein diversity by immunoblotting.

RESULTS

Northern blot analysis of pre-B ALL cell lines revealed short CTGF transcripts that were expressed in association with the active phase of cellular growth. Structural analysis confirmed the synthesis of several novel CTGF mRNA isoforms in B-lineage ALL cell lines that were uniformly characterised by the retention of the coding sequence for the C-terminal (CT) domain. One of these novel spliceforms was expressed in a majority (70%) of primary pre-B ALL patient specimens positive for canonical CTGF mRNA. Evidence that these alternative transcripts have coding potential was provided by cryptic CTGF proteins of predicted size detected by immunoblotting.

CONCLUSION

This study identifies for the first time alternative splicing of the CTGF gene and shows that a short CTGF splice variant associated with cell proliferation is expressed in most cases of primary CTGF-positive pre-B ALL. This novel variant encoding only the CT domain may play a role in pre-B ALL tumorigenesis and/or progression.

The evolution of clinical trials for infant acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) in infants has a significantly inferior outcome in comparison with older children. Despite initial improvements in survival of infants with ALL since establishment of the first pediatric cooperative group ALL trials, the poor outcome has plateaued in recent years. Historically, infants were treated on risk-adapted childhood ALL protocols. These studies were pivotal in identifying the need for infant-specific protocols, delineating prognostic categories and the requirement for a more unified approach between study groups to overcome limitations in accrual because of low incidence. This subsequently led to the development of collaborative infant-specific studies. Landmark outcomes have included the elimination of cranial radiotherapy following the discovery of intrathecal and high-dose systemic therapy as a superior and effective treatment strategy for central nervous system disease prophylaxis, with improved neurodevelopmental outcome. Universal prospective identification of independent adverse prognostic factors, including presence of a mixed lineage leukemia rearrangement and young age, has established the basis for risk stratification within current trials. The infant-specific trials have defined limits to which conventional chemotherapeutic agents can be intensified to optimize the balance between treatment efficacy and toxicity. Despite variations in therapeutic intensity, there has been no recent improvement in survival due to the equilibrium between relapse and toxicity. Ultimately, to improve the outcome for infants with ALL, key areas still to be addressed include identification and adaptation of novel prognostic markers and innovative therapies, establishing the role of hematopoietic stem cell transplantation in first complete remission, treatment strategies for relapsed/refractory disease and monitoring and timely intervention of late effects in survivors. This would be best achieved through a single unified international trial.

Glucocorticoid resistance in T-lineage acute lymphoblastic leukaemia is associated with a proliferative metabolism

Glucocorticoids (GCs) are among the most important drugs for acute lymphoblastic leukaemia (ALL), yet despite their clinical importance, the exact mechanisms involved in GC cytotoxicity and the development of resistance remain uncertain. We examined the baseline profile of a panel of T-ALL cell lines to determine factors that contribute to GC resistance without prior drug selection. Transcriptional profiling indicated GC resistance in T-ALL is associated with a proliferative phenotype involving upregulation of glycolysis, oxidative phosphorylation, cholesterol biosynthesis and glutamate metabolism, increased growth rates and activation of PI3K/AKT/mTOR and MYC signalling pathways. Importantly, the presence of these transcriptional signatures in primary ALL specimens significantly predicted patient outcome. We conclude that in lymphocytes the activation of bioenergetic pathways required for proliferation may suppress the apoptotic potential and offset the metabolic crisis initiated by GC signalling. It is likely that the link between GC resistance and proliferation in T-ALL has not been fully appreciated to date because such effects would be masked in the context of current multiagent therapies. The data also provide the first evidence that altered expression of wild-type MLL may contribute to GC-resistant phenotypes. Our findings warrant the continued development of selective metabolic inhibitors for the treatment of ALL.

Authenticity and drug resistance in a panel of acute lymphoblastic leukaemia cell lines

Cell lines are important models for drug resistance in acute lymphoblastic leukaemia (ALL), but are often criticised as being unrepresentative of primary disease. There are also doubts regarding the authenticity of many lines. We have characterised a panel of ALL cell lines for growth and drug resistance and compared data with that published for primary patient specimens. In contrast to the convention that cell lines are highly proliferative, those established in our laboratory grow at rates similar to estimates of leukaemic cells in vivo (doubling time 53–442 h). Authenticity was confirmed by genetic fingerprinting, which also demonstrated the potential stability of long-term cultures. In vitro glucocorticoid resistance correlated well with that measured ex vivo, but all lines were significantly more sensitive to vincristine than primary specimens. Sensitivity to methotrexate was inversely correlated to that of glucocorticoids and L-asparaginase, indicating possible reciprocity in resistance mechanisms. A cell line identified as highly methotrexate resistant (IC₅₀ >8000-fold higher than other lines) was derived from a patient receiving escalating doses of the drug, indicating in vivo selection of resistance as a cause of relapse. Many of these lines are suitable as models to study naturally occurring resistance phenotypes in paediatric ALL.

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.

The nuclear oncoprotein TLX1/HOX11 associates with pericentromeric satellite 2 DNA in leukemic T-cells

TLX1/HOX11, a DNA-binding homeodomain protein, was originally identified by virtue of its aberrant expression in T-cell leukemia and subsequently found to be crucial for normal spleen development. The precise mechanism of TLX1 function remains poorly understood, although it is known that it can act as both a transcriptional activator and repressor and can downregulate the Aldh1a1 gene in embryonic mouse spleen. Using a whole-genome PCR approach, we show here that TLX1 protein directly interacts with pericentromeric human satellite 2 DNA sequences. Such DNA is known to localize to heterochromatin, which among other roles has been implicated in gene silencing. The interaction was confirmed in vitro and in vivo by gel retardation and chromatin immunoprecipitation assays involving satellite 2 DNA, which contained sequences resembling TLX1 binding sites. Using immunofluorescence microscopy, TLX1 demonstrated a punctate pattern of staining in the nuclei of leukemic T-cells (ALL-SIL). Double labelling indicated that TLX1 colocalized with the centromeric protein CENP-B, demonstrating that the TLX1 foci corresponded to clusters of centromeric DNA. The novel interaction of TLX1 with constitutive heterochromatin adds an additional level of complexity to the intracellular functions of this transcriptional regulator and may have relevance to its roles in transcriptional repression and T-cell immortalization.

Expression profiles of acute lymphoblastic and myeloblastic leukemias with ALL-1 rearrangements

The ALL-1 gene is directly involved in 5-10% of acute lymphoblastic leukemias (ALLs) and acute myeloid leukemias (AMLs) by fusion to other genes or through internal rearrangements. DNA microarrays were used to determine expression profiles of ALLs and AMLs with ALL-1 rearrangements. These profiles distinguish those tumors from other ALLs and AMLs. The expression patterns of ALL-1-associated tumors, in particular ALLs, involve oncogenes, tumor suppressors, antiapoptotic genes, drug-resistance genes, etc., and correlate with the aggressive nature of the tumors. The genes whose expression differentiates between ALLs with and without ALL-1 rearrangement were further divided into several groups, enabling separation of ALL-1-associated ALLs into two subclasses. One of the groups included 43 genes that exhibited expression profiles closely linked to ALLs with ALL-1 rearrangements. Further, there were evident differences between the expression profiles of AMLs in which ALL-1 had undergone fusion to other genes and AMLs with partial duplication of ALL-1. The extensive analysis described here pinpointed genes that might have a direct role in pathogenesis.

Expression of HOX11 in childhood T-lineage acute lymphoblastic leukaemia can occur in the absence of cytogenetic aberration at 10q24: a study from the Children's Cancer Group (CCG)

Clonal genetic aberrations in tumour cells provide critical information for the development of new diagnostic and therapeutic strategies for patients. In paediatric T-cell acute lymphoblastic leukaemia (T-ALL) chromosomal translocations are present in 30-35% of cases. HOX11 and the closely related HOX11L2 genes play a key role in T-ALL. HOX11 is aberrantly activated by either of the two chromosomal translocations, t(7;10) and t(10;14). In this study, HOX11 expression levels were measured by real-time quantitative reverse-transcriptase polymerase chain reaction. We show that leukaemic blasts from 15/76 (19.7%) paediatric T-ALL patients expressed the HOX11 gene at high level and 22/76 (28.9%) at low level, yet the reported frequency for chromosomal rearrangement of 10q24 is 4-7%. Direct cytogenetic analysis revealed that only 2/16 specimens that showed HOX11 expression exhibited abnor-malities at 10q24. These results confirm and extend our previously published findings, and implicate mechanisms other than gross chromosomal translocations for the deregulation of HOX11. Analysis of clinical outcome for the whole study group showed a trend for better outcome for patients with leukaemic blasts expressing HOX11 at high level. A statistically significant difference in clinical outcome was found in a subgroup of 20 patients treated for high-risk disease on CCG-1901 from the Children's Cancer Group, where HOX11 expression in leukaemic blasts conferred a prognostic advantage (P=0.01).

A complex containing PBX2 contributes to activation of the proto-oncogene HOX11

Ectopic expression of the homeobox gene HOX11 is associated with a significant proportion of childhood T-cell acute lymphoblastic leukaemias (T-ALLs). We hypothesise that one mechanism of gene deregulation involves overcoming the silencing mechanism(s) of gene expression present in normal cells. Here, we describe a search for trans-acting factors that control transcriptional activity from a distal 5' region of the HOX11 promoter. We have identified a region of this promoter which contributes significantly to HOX11 activation and two distinct regulatory elements are involved. First, a PBX2 Regulatory Element PRE-1048 has been identified which contains a novel DNA-binding sequence and mediates significant activation of the HOX11 gene in K562 cells. This is the first report of a homeobox gene being specifically regulated by PBX2 and the second report of a vertebrate homeobox target gene of a PBX protein. The PREP1 protein was also shown to be part of the PRE-1048-binding complex. The other regulatory element we describe here RE-1019 contains little sequence conservation to known transcription control elements. It appears that this element is a novel sequence that binds an as yet unidentified factor, mediating significant activation of the HOX11 gene in K562 cells. This is the first detailed report of elements that mediate regulation of the proto-oncogene HOX11.

Novel alternative PBX3 isoforms in leukemia cells with distinct interaction specificities

PBX3 is a member of the PBX family of TALE homeobox genes. The prototypic member, PBX1, was first identified in chromosomal translocations in B-lineage leukemia and is required for normal hematopoiesis. PBX2 and PBX3 were later identified as members of this highly conserved family by their strong homology to PBX1. While the expression pattern of PBX1 is restricted, PBX2 and PBX3 are ubiquitously expressed. Little is known about the functional role of PBX3. Our studies identified two PBX3 transcripts alternative to the canonical forms, PBX3A and PBX3B, resulting from a novel splice in PBX3. These new isoforms, named PBX3C and PBX3D, have been detected in all tissues and cell lines tested. Intriguingly, expression of PBX3D is favored in normal cells, whereas PBX3C expression is favored in leukemia cells. Functional studies showed that PBX3C and PBX3D proteins were unable to interact with the PBX-interacting factor PREP1 and weakly interacted with MEIS proteins. We propose that PBX3C and PBX3D may affect PBX3-mediated transcriptional regulation by acting in opposition to the known PBX proteins through alternative PBX3 complex formation. The identification and characterization of these novel PBX3 isoforms provide a foundation for a better understanding of the biological role of PBX3.

INK4A/ARF deletions are acquired at relapse in childhood acute lymphoblastic leukaemia: a paired study on 25 patients using real-time polymerase chain reaction

Current risk-adjusted intensive therapies for childhood acute lymphoblastic leukaemia (ALL) are expected to result in an event-free survival of greater than 75%. In sharp contrast, relapsed paediatric ALL is a difficult disease to treat. In this study, 25 paediatric patients with ALL were analysed at diagnosis and relapse for their p16 (exon 2) status using the most accurate method of detection, real-time polymerase chain reaction (PCR). The median time to relapse for the group was 27 months. At diagnosis, the incidence of p16 homozygous and hemizygous deletion in this group was 32% and 20% respectively. The incidence of homozygous p16 deletion at relapse was 64%. A large number of patients, eight of 16 (50%), developed p16 homozygous deletion at relapse. Of those eight patients, four were hemizygous and four were germline at diagnosis. At diagnosis, those patients with a homozygous or hemizygous p16 deletion relapsed sooner than those germline for p16. We have shown that p16 alterations are frequently present in relapsed lymphoblastic leukaemia in children.

Medulloblastoma/primitive neuroectodermal tumour studied as a Matrigel enhanced subcutaneous xenograft model

An important role for pre-clinical models of medulloblastoma/primitive neuroectodermal tumour (MB/PNET) is inhibited by the limitations of conventional heterotransplantation. Nine cohorts of MB/PNET were studied for subcutaneous engraftment in nude mice by both conventional and Matrigel supplemented methods. While no subcutaneous tumours resulted from 63 conventional attempts, an aggregate 41 xenografts from 72 injections (57%) were produced when Matrigel was added to the cell suspension. In subsequent passage, engraftment rate approached 100%. To study the response to chemotherapeutic agents in the model, a total of 221 tumours in 3 cohorts were treated using one of the following: cisplatin, carboplatin, vincristine, cyclophosphamide, diaziquone, or saline control. While all agents demonstrated statistically significant activity, cyclophosphamide proved to be particularly effective. The potential applications of this xenograft model in the biologic as well as therapeutic study of MB/PNET deserve continuing investigation.

Hemizygous p16(INK4A) deletion in pediatric acute lymphoblastic leukemia predicts independent risk of relapse

The genes at the INK4A/ARF locus at 9p21 are frequently involved in human cancer. Virtually all p16(INK4A) exon 2 (henceforth called p16) inactivation in pediatric acute lymphoblastic leukemia (ALL) occurs by gene deletion. The results of this study illustrate that real-time quantitative polymerase chain reaction is capable of detecting gene deletion in primary patient specimens with a precision not previously achieved by conventional methods. Importantly, this assay includes the detection of hemizygous deletions. The study revealed, strikingly, that the risk ratio for relapse for hemizygous deletion compared with no deletion was 6.558 (P =.00687) and for homozygous deletion was 11.558 (P =.000539). These results confirm and extend the authors' previous findings that homozygous deletion of p16 in pediatric ALL patients is an independent prognostic indicator of outcome from therapy.

MYCN amplification and 17q in neuroblastoma: evidence for structural association

MYCN oncogene amplification in neuroblastoma is statistically associated with gain of chromosome segment 17q21-qter. In neuroblastoma cell lines and primary tumors with MYCN amplification in the form of homogeneously staining regions (hsrs), juxtaposition of chromosome 17 material with MYCN sequences has occasionally been reported, raising the possibility of a physical affinity between MYCN and chromosome arm 17q. We used FISH to test for association between chromosome 17 segments and MYCN in eight neuroblastoma cell lines and two neuroblastoma primary tumors known to include hsrs. Evidence of an association was found in the chromosomes of both primary tumors; in one, a MYCN hsr was inserted into a structurally abnormal chromosome 17, in the other, an hsr in 16p was shown to be flanked by 17 material. In cell line NCG, hsrs in 4q and 16p were flanked by 17q material. These observations confirm the juxtaposition of 17q material with MYCN sequences in some neuroblastomas, and imply that there may be a physical or functional relationship between these two features in MYCN amplified neuroblastoma.

The partial nontandem duplication of the MLL (ALL1) gene is a novel rearrangement that generates three distinct fusion transcripts in B-cell acute lymphoblastic leukemia

A partial nontandem duplication (PNTD) of mixed lineage leukemia (MLL) gene is described in B-cell acute lymphoid leukemia without structural cytogenetic abnormalities at 11q23 and 9p22. A duplicated portion of MLL is interrupted by the insertion of a region of 9p22 that includes the 3'-end of the AF9 gene. The PNTD encodes: (a) a PNTD transcript; (b) a partial tandem duplication of MLL; and (c) a chimeric transcript fusing MLL to the 3'-end of AF9, mimicking the t(9;11)(p22;q23) and expressed 1024-fold higher than the other two. The MLL PNTD, therefore, contributes toward leukemogenesis through simultaneous production of fusion transcripts that are otherwise encoded by three distinct genetic defects.

Promoter demethylation accompanies reactivation of the HOX11 proto-oncogene in leukemia

Despite considerable work on the epigenetic control of tumor suppressor genes, little is known about the potential role of promoter CpG demethylation in the activation of oncogenes in lymphoid tumors. The HOX11 proto-oncogene is frequently activated in T-cell acute lymphoblastic leukemia (T-ALL). HOX11 activation can occur in the absence of translocation of the gene to the T-cell receptor locus (Salvati et al., 1995), implying that activation mechanisms must be involved other than the juxtaposition of the gene to adjacent enhancing sequences. We tested whether the methylation status of the proximal promoter was correlated with expression status in T-ALL and found that, in all cases, expression of HOX11 in T-ALL was associated with extensive demethylation of the proximal HOX11 promoter, regardless of whether or not translocation was involved. In contrast, cells that did not express HOX11 showed a more methylated pattern of CpG residues in the proximal promoter. Methylation of this sequence in vitro was sufficient to silence the proximal promoter. We propose a model in which the selection of leukemia clones via a pathway involving HOX11 expression requires the demethylation of its promoter as a prerequisite for additional gene activation mechanisms.

A human T-cell line with inducible production of interleukins 5 and 4. A model for studies of gene expression

The production of interleukin-5 (IL5) and interleukin-4 (IL4) by activated T-cells is important in the pathogenesis of helminth infections and allergy. Human Jurkat cells express IL4 but one of the main factors restricting studies of human IL5 expression has been the lack of human T-cell lines which express significant levels of IL5 in an inducible fashion. We report that the human T-cell leukemia cell line (PER-117), previously shown to produce IL2, also produces IL5 and IL4, and is a useful model for the study of the regulation of IL5 and IL4 gene expression. We show that expression of IL5 and IL4 mRNAs in PER-117 cells is stimulation dependent. IL5 and IL4 reporter constructs are also transiently expressed in these cells in an inducible fashion. IL5 production in the PER-117 cell line can be activated by phorbol 12-myristate 13-acetate alone and further enhanced by calcium ionophore A23187, cyclic adenosine 3', 5'-monophosphate or anti-CD28 antibodies. The conditions used to stimulate the PER-117 cells determined whether IL5 production was inhibited by cyclosporin A or dexamethasone. These data indicate that the PER-117 cell line is a model to study signal transduction and transcriptional activation of the human IL5 gene in human T-cells.

The total care unit for pediatric hematology and oncology, Princess Margaret Hospital for Children, Perth, Australia

The total care unit for the treatment of pediatric hematology/oncology in Perth, Australia is so named to embody the philosophy of multidisciplinary care of children and their families. Where possible, patients are treated according to randomized controlled trials of the large cooperative Children's Cancer Group. There is a seamless association of clinical and laboratory research. Hemopoietic stem cell transplantation is managed within the unit, as well as treatment of a range of non-malignant hematological disorders. Long-term follow-up of survivors of childhood cancer is coordinated from the unit.

Sequence of 10q24 locus surrounding the HOX11 oncogene reveals a new gene HUG1 expressed in a T-ALL cell line

HOX11 is a gene encoding a homeobox protein which is found to be deregulated in T-cell acute lymphoblastic leukaemia (T-ALL). As a basis for studying the mechanism of deregulation of HOX11 expression in leukaemia, the locus containing the HOX11 proto-oncogene at 10q24 was cloned from a genomic P1 Artificial Chromosome (PAC) library. The PAC clone with an insert size of 120kb was isolated and mapped by restriction analysis. A series of contiguous subclones were then obtained which span 20kb surrounding the HOX11 gene. These subclones were used to sequence across the entire 20kb region to the 3' boundary of the PAC insert. This work provides for the first time the full intron and 5' non-coding sequences of the HOX11 gene which will aid the identification of novel transcriptional control elements which may be involved in silencing HOX11 expression in normal cells. The sequence information was also used to search for novel large open reading frames (ORFs). One such ORF (1.1kb) would encode a protein of at least 39kDa. This basic protein (pI, 12.5) would be very proline rich and could potentially encode a novel transcription factor. In order to establish if this ORF corresponds to a bona fide transcribed gene, RT-PCR analysis was performed. The mRNA for this protein is expressed in the T-ALL cell line Jurkat and has been designated HUG1, for HOX11 Upstream Gene.

Molecular characterization of a complex chromosomal translocation breakpoint t(10;14) including the HOX11 oncogene locus

Based on cytogenetic studies, non-random chromosomal translocations which involve the HOX11 gene at locus 10q24 and the TCR genes at loci 7q35 or 14q11 have been reported to occur in 5% of T-ALL. HOX11, a member of the homeobox family of genes, has been shown to play a role in T-ALL. The activation of the HOX11 gene by translocations to the TCR locus results in the inappropriate expression of a 2.3 kb transcript. In this paper we describe a t(10;14)(q24;q11) breakpoint from a T-ALL patient specimen. The breakpoint appears to be mediated by errors in the TCR/V(D)J recombination system, but is more complex than commonly described reciprocal translocations between the HOX11 and TCR genes, since it involves an inversion event of the TCRdelta genes. In addition, the breakpoint was characterised to a previously unsequenced area of the 10q24 locus, 3.4 kb upstream of the HOX11 gene. This breakpoint is more centromeric than the breakpoint cluster region previously shown to be involved in the majority of reported t(10;14)(q24;q11) translocations. Hence, our investigations of the translocation breakpoint in this patient identify another breakpoint region in the 10q24 locus and may define a novel recombination 'hot spot'. Surprisingly, our studies provide a mechanism for a previously unexplained complex translocation described by another group which involves the same region of the HOX11 promoter.

Genomic structure, tissue expression and chromosomal location of the LIM-only gene, SLIM1

Human SLIM1 is a recently described gene of the LIM-only class encoding four and a half tandemly repeated LIM domains. LIM domains are double zinc finger structures which provide an interface for protein/protein interactions and are conserved in a variety of nuclear and cytoplasmic factors important in cell fate determination and cellular regulation. Here we report the structural organization, expression pattern and chromosomal localization of the human SLIM1 gene. SLIM1 was found to contain at least five exons with all four introns disrupting the coding region at a similar position relative to the respective complete LIM domains. Northern blot analysis confirmed strikingly high expression of SLIM1 in skeletal muscle and heart, with much lower expression observed in several other tissues including colon, small intestine and prostate. The SLIM1 gene was assigned to human chromosome Xq26 using fluorescence in situ hybridization.

Synergistic action of stem-cell factor and interleukin-7 in a human immature T-cell line

The thymus provides the microenvironment that is optimal for T-cell differentiation. The most immature cells in the human thymus express the stem-cell marker CD34 and they respond to cytokines, including stem-cell factor (SCF) and interleukin-7 (IL-7). For the normal progression of T-cell development these two cytokines appear to be vital. We have established and characterized a human pre-T-cell line, PER-487, which mirrors this requirement. This study shows that the simultaneous presence of IL-7 and SCF produces a proliferative response far exceeding additive effects. Furthermore, providing these signals in succession did not achieve the effect observed when they were provided simultaneously. This finding suggests that the effect was not mediated via secretion of molecules or modulation of surface expression. The convergence of the signal transduction pathways of the two cytokines is not known, thus cell line PER-487 provides a unique model for studying the synergistic interaction of IL-7 and SCF.

Multiple negative elements contribute to repression of the HOX11 proto-oncogene

The HOX11 proto-oncogene is normally expressed in embryogenesis where it directs the synthesis of the spleen. In adult tissues, HOX11 expression is silenced by an unknown mechanism. Aberrant expression of HOX11 occurs in T-cell acute lymphoblastic leukaemia (T-ALL), where it is thought to be involved in T-cell immortalization. The deregulated expression of HOX11 is frequently associated with chromosomal translocations which juxtapose a T-cell receptor (TCR) gene upstream of the HOX11 gene. In these cases, it is presumed that the activation of HOX11 expression results from bringing the gene under the control of TCR enhancer elements. However, activation of HOX11 also occurs in the absence of an associated translocation in both T-ALL and erythroleukaemia cells, implying that an alternative activation mechanism may exist. We hypothesized that HOX11 may be repressed in normal T-cells and erythroid cells by the action of negative elements which may be deleted or mutated in leukaemia. We therefore conducted a search for negative elements in the human HOX11 promoter which may function to silence its expression in normal cells of the haematopoietic lineages. Since little sequence of the HOX11 promoter was available, we began our investigation by sequencing over 4.5 kilobases of untranslated DNA from upstream of HOX11. The human sequence that overlaps with the 2.1 kb of murine Hox11 is highly conserved, suggesting that a large region of DNA upstream of HOX11 may have a regulatory function. We then used transfection assays to test the ability of portions of the promoter to drive transcription of a reporter gene. These studies identified four negative elements. Two of them (NRE2 and NRE4) function in all cell lines tested, while the remaining two (NRE1 and NRE3) appear to be cell-type specific. The DNA sequences of three elements are conserved between the human and mouse HOX11/Hox11 promoters. We propose a model in which the combined action of these negative elements contributes to the overall repression of HOX11 expression in normal blood cells.

Macrophage-derived nitric oxide regulates T cell activation via reversible disruption of the Jak3/STAT5 signaling pathway

Nitric oxide (NO) has been invoked as an important pathogenic factor in a wide range of immunologically mediated diseases. The present study demonstrates that macrophage-derived NO may conversely function to fine tune T cell-mediated inflammation via reversible dephosphorylation of intracellular signaling molecules, which are involved in the control of T cell proliferation. Thus, T cells activated in the presence of alveolar macrophages are unable to proliferate despite expression of IL-2R and secretion of IL-2. This process is reproduced by the NO generator S-nitroso-N-acetylpenicillamine and is inhibitable by the NO synthase inhibitor N(G)-methyl-L-arginine. Analysis of T cell lysates by immunoprecipitation with specific Abs and subsequent immunoblotting indicated marked reduction of tyrosine phosphorylation of Jak3 and STAT5 mediated by NO. Further studies indicated that NO-mediated T cell suppression was reversible by the guanylate cyclase inhibitors methylene blue and LY-83583 and was reproduced by a cell-permeable analogue of cyclic GMP, implicating guanylate cyclase activation as a key step in the inhibition of T cell activation by NO.

A new pineoblastoma cell line, PER-480, with der(10)t(10;17), der(16)t(1;16), and enhanced MYC expression in the absence of gene amplification

Pineoblastoma is a rare, but highly malignant tumor of the central nervous system (CNS) in children and is classified as a central primitive neuroectodermal tumor (PNET). Despite notable recent advances in understanding the molecular genetic basis of malignancies, the pathogenesis of PNETs remains enigmatic. There is scant information on the cytogenetics of PNETs arising in the pineal gland and the only three reported cases did not show any common aberrations. Here we report the establishment and characterization of a new pineoblastoma cell line, PER-480. The biopsy material and the cell line were characterized using light and electron microscopy and immunohistochemical analyses. The cell line was examined for expression of cell surface markers using a panel of monoclonal antibodies and by cytogenetic analysis. MYC family genes were studied at the DNA, RNA, and protein level. Cell line PER-480 showed neuronal differentiation and the karyotype demonstrated two abnormalities, a der(10)t(10;17) and a der(16)t(1;16). An intriguing finding is that all three pineoblastoma cell lines established in our laboratory, PER-452, PER-453, and PER-480, showed enhanced expression but not amplification of a member of the MYC family of proto-oncogenes. Cell line PER-480 reported here will be useful for the further investigation of the molecular genetic basis of central PNETs.

Homozygous deletion of the p16/MTS1 gene in pediatric acute lymphoblastic leukemia is associated with unfavorable clinical outcome

The p16 gene (MTS1, CDKN2, p16INK4A, CDKI) encoding an inhibitor of cyclin-dependent kinase 4 (cdk4) has been found to be deleted in various types of tumors, including leukemia, and is thought to code for a tumor suppressor gene. Our preliminary findings on eight pediatric patients with acute lymphoblastic leukemia (ALL) suggested that the survival of patients carrying a homozygous p16 gene deletion was significantly inferior to that of those without a deletion. The present study on 48 patients tested the hypothesis that the clinical outcome for pediatric ALL patients is correlated with the presence or absence of the p16 gene. Overall, nine of 48 children (18.3%) carried a homozygous p16 deletion. Such deletions were significantly more common (P = .003) among T-ALL patients (five of eight, 62.5%) than among precursor-B-ALL patients (four of 40, 10.0%). Of nine patients exhibiting p16 deletions, eight (88.9%) were classified as high-risk patients by the recognized prognostic factors of age, white blood cell count, and T-cell phenotype. The 4-year event-free survival in the study population as a whole was 72.7%. Without adjustment for other risk factors (univariate model), the presence of a homozygous p16 deletion was associated with a markedly increased probability of both relapse (P = .0003) and death (P = .002). These findings raise the question of whether the p16 deletion itself confers an increased risk of relapse after adjusting for the known risk factors. In this analysis, the estimated risk multiplier factor for relapse in patients carrying the p16 deletion was 14.0 (P = .0004) and for the risk of death 15.6 (P = .0008). We therefore conclude that the presence of a homozygous p16 deletion may well be an important risk factor for both relapse and death in childhood ALL, and that its prognostic effect is not a consequence of confounding by other factors already known to influence outcome in this disease.

Deletions of the p16 gene in pediatric leukemia and corresponding cell lines

The p16 gene (MTS1 or CDK4I) encoding an inhibitor of cyclin-dependent kinase 4 (cdk4), has been reported to be deleted in various tumor cell lines, including lines derived from leukemic cells. The reported frequency of p16 gene loss is much higher in established cell lines than in primary tumor specimens. We investigated the status of the p16 gene in pediatric leukemias using 12 established cell lines of differing phenotypes and their corresponding primary leukemic cells. Six of 12 cell lines, including acute lymphoblastic leukemia (ALL) lines of T-cell (three of four), of precursor-B cell (two of four) and of mixed phenotype (one of four), showed homozygous deletion of the p16 gene using PCR and Southern blotting. Comparison of the cell lines with their corresponding primary leukemic cells clearly showed that in all 12 paired samples there were identical findings with respect to the presence or absence of the p16 gene, demonstrating that loss of the gene was a feature of the primary leukemic cells. This is the first study to show this correlation using a panel of paired samples, indicating that p16 gene deletions were not an artifact of in vitro cell culture. Furthermore, the survival of ALL patients with p16 gene deletions was significantly inferior to those without deletions, suggesting that this genetic alteration may be a clinical prognostic factor.

Regulation of T-cell activation in the lung: isolated lung T cells exhibit surface phenotypic characteristics of recent activation including down-modulated T-cell receptors, but are locked into the G0/G1 phase of the cell cycle

Peripheral lung tissue contains large numbers of T cells, strategically located for immune surveillance at the blood-air interface. Given the intensity of antigenic exposure at this site, it is clear that local T-cell activation events require strict control, in order to maintain tissue homeostasis. How this control is achieved in this unique tissue microenvironment is unknown, and the present study sought to elucidate the process via detailed analysis of the surface phenotypic characteristics of freshly isolated lung T cells. We report below that these cells display typical characteristic of 'postactivation', notably elevated basal Ca2+ concentrations, down-modulated T-cell receptors, expression of Ia and 'late' activation antigens and concomitant CD4/CD8. However, levels of interleukin-2 receptor and CD2 expression were below those expected of 'activated' T-cell populations, and virtually all of the cells were found to be in the G0/G1 phases of the cell cycle. These properties bear a remarkable similarity to those of T cells activated in the presence of endogenous tissue (alveolar) macrophages from the lung (see accompanying paper). We hypothesize that they reflect the in vivo operation of an endogenous macrophage-mediated T-cell anergy-induction process, the function of which is to limit the local clonal expansion of T cells in peripheral lung tissue after in situ activation.

Regulation of T-cell activation in the lung: alveolar macrophages induce reversible T-cell anergy in vitro associated with inhibition of interleukin-2 receptor signal transduction

Alveolar macrophages (AM) are recognized as archetypal 'activated' macrophages with respect to their capacity to suppress T-cell responses to antigen or mitogen, and this function has been ascribed an important role in the maintenance of local immunological homeostasis at the delicate blood:air interface. The present study demonstrates that this suppression involves a unique form of T-cell anergy, in which 'AM-suppressed' T cells proceed normally through virtually all phases of the activation sequence including Ca2+ flux, T-cell receptor (TCR) modulation, cytokine [including interleukin-2 (IL-2)] secretion and IL-2 receptor (IL-2R) expression. However, the 'suppressed' T cells fail to up-regulate CD2, and do not re-express normal levels of TCR-associated molecules after initial down-modulation; moreover, they are unable to transduce IL-2 signals leading to phosphorylation of IL-2R-associated proteins, and remained locked in G0/G1. The induction of this form of anergy is blocked by an NO-synthase inhibitor, and is reversible upon removal of AM from the T cells, which then proliferate in the absence of further stimulation. We hypothesize that this mechanism provides the means to limit the magnitude of local immune responses in this fragile tissue microenvironment, while preserving the capacity for generation of immunological memory against locally encountered antigens via clonal expansion of activated T cells after their subsequent migration to regional lymphoid organs. In an accompanying paper, we demonstrate that a significant proportion of T cells freshly isolated from lung exhibit a comparable surface phenotype.

HOX11 expression in pediatric acute lymphoblastic leukemia is associated with T-cell phenotype

Based on cytogenetic analysis, chromosomal translocations involving band 10q24 occur in 4-7% of T-cell acute lymphoblastic leukemia (T-ALL). The HOX11 gene is located in this chromosomal band and is activated by translocations t(10;14) (q24;q11) and t(7;10) (q35;q24). Ectopic expression of the HOX11 gene appears to be involved in the development of T-cell tumors. The aim of this study was to determine the frequency of HOX11 activation in pediatric ALL patients and to correlate gene expression with ALL immunophenotype. None of 53 B-lineage ALLs was positive for HOX11 expression, however, Northern blot and RT-PCR analysis revealed that four of 12 T-ALLs (33%) showed expression of the gene. In order to assess whether HOX11 expression is present in other pediatric malignancies we examined a panel of 20 tumor cell lines established from solid tumors and leukemias, but none of them showed expression of HOX11. Using our RT-PCR method we confirmed that HOX11 expression is not detectable in normal T-cells. These findings indicate that HOX11 expression in pediatric ALL is exclusive to T-ALL and does not occur in B-lineage ALL. The frequency detected by molecular techniques was significantly higher than the frequency reported in the literature based on cytogenetic analysis. These results support the notion that ectopic expression of the HOX11 homeobox gene is a crucial step in T-cell tumorigenesis.

Synergistic action of interleukin-2 and Steel factor (SLF) on a human T lymphoblastoid cell line

Ten cell lines recently established from paediatric patients with acute lymphoblastic leukaemia (ALL) were examined for expression of P145c-kit, the growth factor receptor encoded by the c-kit proto-oncogene, by immunofluorescence and flow cytometry using monoclonal antibody YB5.B8. Three of five T-ALL cell lines, but none of five B lineage ALL cell lines displayed significant binding of the antibody. The cell line with the highest level of binding was PER-423 (Kees et al, Leukemia Res 1993; 17: 51-59 which has the phenotype CD7+, CD56bright, CD2-, CD4-, CD5-, CD8-, CD16-, has rearranged T cell receptor beta-chain genes, expresses cytoplasmic CD3 and is strictly dependent on interleukin 2 (IL-2) for proliferation. Recombinant to act in synergy with IL-2 to promote proliferation of PER-423 cells. In five experiments, SLF increased the maximal amount of proliferation by 105 +/- 15%, and decreased the level of IL-2 required for a half-maximal response by 43 +/- 7%. The cells constitutively express the intermediate affinity IL-2 receptor (beta/gamma), but can be induced in the presence of phorbol ester to express the alpha chain (CD25, Tac) which confers high affinity binding of IL-2. In contrast, the alpha chain was not induced by SLF. The enhancement of proliferation of PER-423 cells by SLF could be prevented by inclusion in the assay of a blocking monoclonal antibody to P145c-kit. These experiments demonstrate that SLF/P145c-kit can provide a significant growth stimulus for ALL cells, and PER-423 cells may be a useful system for investigating the mechanism of synergy between SLF and IL-2.

Biochemical pharmacology and DNA methylation studies of arabinosyl 5-azacytidine and 5,6-dihydro-5-azacytidine in two human leukemia cell lines PER-145 and PER-163

1-beta-D-arabinofuranosyl-5-azacytosine (ara-AC) and 5,6-dihydro-5-azacytidine (DHAC) are two new antitumor agents under clinical investigations, which exhibit the chemical similarities found in the tumoricidal drug cytosine arabinoside (ara-C) and the nitrogen substitution in the 5 position of the pyrimidine ring found in 5-azacytidine (5-aza-C). The cellular anabolism of ara-AC and DHAC and their effect on DNA methylation have been examined in two new human leukemia cell lines, which are sensitive (PER-145) and resistant (PER-163) to ara-C. The triphos-phate anabolite of ara-AC, ara-ACTP, was the major cellular anabolite in the cellular extracts of the PER-145 cells, reaching a cellular saturation concentration of 64.1 +/- 3.2 microM using 25 microM of the drug. Only trace levels of ara-ACTP were detected in the PER-163 cell line, which lacks deoxycytidine kinase, after exposure to a similar concentration. Notably, after 1 mM, the ara-ACTP concentration averaged 12 +/- 3 microM. DHAC was anabolized by both cell lines to a similar degree but required much higher nucleoside concentrations (100 microM or higher) to achieve similar cellular concentrations of its triphosphate, DHACTP. Although the deoxy-derivative, DHAdCTP, was detected in both cell lines, it was detected at 1-2 log10 lower concentrations than DHACTP. DNA methylation studies showed that DHAC had a profound effect in inducing DNA hypomethylation in both cell lines, with nadir values of 27.3 and 29.2% of control.(ABSTRACT TRUNCATED AT 250 WORDS)

New translocation t(2;13)(p12;q34) and rearrangement of the MLL gene in a childhood leukemia cell line

Here we report the case of a 7-month-old boy who presented with biphenotypic acute leukemia, but with leukemia cells of B-cell phenotype present at the time of relapse. Two cell lines were derived from bone marrow specimens obtained at relapse, and immunophenotyping and analysis of antigen receptor gene configuration revealed concordance between the patient's leukemic cells and the cell lines. Cell line PER-377 shows a new chromosomal abnormality, t(2;13)(p12;q34), a molecular rearrangement at chromosome band 11q23 in the absence of a cytogenetically detectable abnormality of this band, and deletion of the genes for IGK.

Suppression of T-cell activation by pulmonary alveolar macrophages: dissociation of effects on TcR, IL-2R expression, and proliferation

Suppression of local T-cell activation in the lower respiratory tract by resident pulmonary alveolar macrophages (PAMs) is believed to play an important role in the maintenance of local immunological homeostasis. However, the mechanism(s) by which pulmonary alveolar macrophages regulate T-cell responses are poorly characterized. The present study examines early events during the activation process in mitogen-stimulated T-cell cultures, in which proliferation was completely blocked by the presence of pulmonary alveolar macrophages. Despite inhibition of proliferation, the T-cells demonstrated normal Ca++ flux, normal modulation of surface expression of CD3 and T-cell receptor alpha/beta (TCR alpha/beta), upregulation of interleukin-2 receptors alpha and beta (IL-2R alpha and IL-2R beta), and secretion of high levels of interleukin-2 (IL-2). Thus, pulmonary alveolar macrophage regulation of T-cell activation appears to permit initial expression of effector function, but selectively inhibits further amplification of the overall T-cell response by limiting clonal expansion of the activated effector T-cell.

Enhanced MYCN expression and isochromosome 17q in pineoblastoma cell lines

We have established two cell lines, PER-452 and PER-453, from an 8-month-old girl with an extensive pineoblastoma. Characterization of these lines revealed that the proto-oncogenes MYC and MYCN were not amplified, but both cell lines showed MYCN expression comparable to a cell line with 200-fold MYCN amplification. Both cell lines contained an i(17q). These results support the concept that pineoblastomas belong to a larger group of primitive neuroectodermal tumors of the central nervous system. These two cell lines provide a unique opportunity to investigate the molecular genetic mechanisms underlying these neoplasms further.

A new human cell line for the molecular dissection of the requirement for interleukin-1 in the production of interleukin-2 by immature T cells

An immature human T cell line, PER-117, can be induced to secrete interleukin-2 (IL-2). In contrast to mature T cells or the Jurkat cell line, PER-117 cells require interleukin-1 (IL-1) for optimal IL-2 secretion, in addition to calcium ionophore and phorbol 12-myristate 12-acetate (PMA). These requirements mirror the conditions reported to be optimal for normal immature T cell receptor (TCR) negative thymocytes. IL-1 did not substitute for either of the other signals required for IL-2 production, i.e., calcium ionophore or PMA, suggesting that IL-1 activates pathways different from those elicited by the two other stimuli. For optimal effect, IL-1 needed to be provided at the same time as the two other signals. Significantly, a signal provided by a low concentration of PMA (not leading to IL-2 induction by itself in the presence of calcium ionophore) was necessary. The studies reported here provide the first evidence that three signals are required for optimal IL-2 production in a human immature T cell line. PER-117 cells produce substantial levels of IL-2 and thus provide a model to study stage-specific signal transduction and transcriptional activation of the IL-2 gene in IL-1 responsive immature thymocytes.

Regulation of T-cell function in lung tissue by pulmonary alveolar macrophages

Collagenase digestion of perfused, lavaged rat lung yields a large population of CD5+ T cells, which on current evidence appear to be recently derived from the peripheral blood pool. Two-colour cytofluorographic analysis indicates that approximately 65% are CD4+ T cells, which are predominantly of the activated/memory phenotype. By limiting dilution analysis, these peripheral lung wall T cells and their airway counterparts isolated by bronchoalveolar lavage, exhibit markedly reduced capacity to proliferate by comparison to peripheral blood T cells. However, intratracheal inoculation of liposomes containing dichloro-methylene-diphosphonate at a dosage shown to eliminate the majority of resident alveolar macrophages (AM) rapidly restores the immunocompetence of these lung T-cell populations. These results are discussed in relation to recent reports that in vivo elimination of AM from rats and mice greatly amplifies immune responses to inhaled antigens, in particular T-memory cell-dependent secondary antibody responses.

Requirements for the induction of the interleukin-2 receptor complex in a human pre-T-cell line

Cell line PER-117 is a T-cell receptor negative human T-cell line that can be induced to express a functional interleukin-2 receptor (IL-2R). Recombinant interleukin-1 (IL-1) as well as certain combinations of inducer substances could be shown to stimulate the expression of the p55 (alpha)-chain of the IL-2R in PER-117 cells. The synergistic increases in IL-2R alpha expression were demonstrated at the cell surface as well as at the mRNA level. The results suggested that in PER-117 cells IL-1 appears to induce expression of the alpha-chain by pathways that are different to activation via protein kinase C (PKC), and that drug-induced cyclic AMP (cAMP) activation did not substitute for IL-1. We found that the regulation of mRNA for IL-2R beta (p75) differed significantly from that seen for IL-2R alpha. Moreover, the requirements for IL-2R alpha induction determined for this cell line differ from other human cell lines, which may reflect that there are distinct requirements for activation depending on the stage of differentiation and/or lineage of the cells. The PER-117 cell line provides a unique model to examine further the mechanism leading to induction of a functional IL-2R at an early stage of human T-cell differentiation.

Functional interleukin-2 receptor on a Tac negative human leukaemia T-cell line

Cell line PER-423 was derived from the cells of a patient with an immature acute T-lymphoblastic leukaemia and the growth of this human cell line is strictly dependent on interleukin-2 (IL-2). PER-423 cells express the p75 (beta) subunit of the IL-2 receptor (IL-2R beta), while the p55 chain (IL-2R alpha) is not detectable by immunofluorescence. The analysis of the IL-2R revealed that it is of intermediate affinity and the median effective IL-2 concentration for PER-423 cells (EC50 value) was determined to be 1.44 +/- 0.29 nM. Chemical crosslinking studies showed that the receptor consists of one polypeptide of approximately 95 kDa as well as a doublet of 70 kDa and 60 kDa and does not include the IL-2R alpha-chain. The steady-state mRNA level for the p75 subunit was similar to that present in a cell line expressing an IL-2R alpha+ beta+, while only traces for the alpha-chain were detectable. PER-423 cells can be induced to express the alpha-chain of the IL-2R on the cell surface, concomitant with a much reduced EC50 level. Since cell line PER-423 is functionally dependent on IL-2, it provides an ideal model for IL-2 signal transduction studies and for investigations focusing on the requirements for ligand binding vs activation.

Late leukemic relapse 10 years from diagnosis in a child on recombinant human growth hormone

A 12 year-old girl developed a late relapse of acute lymphoblastic leukaemia (ALL) 10 years from first presentation. Initial chemotherapy included vincristine, methotrexate, prednisolone, and L-asparaginase with cranial radiotherapy (18 Gy) for central nervous system prophylaxis. Documented growth failure led to recombinant human growth hormone (rhGH) replacement therapy being instituted in May 1989, 6 years from end of therapy and 2 years prior to relapse. Three independent experiments demonstrated no increased cell proliferation in vitro when the patient's thawed cryopreserved fresh leukemic cells were incubated with rhGH. However, a pre-T ALL cell line (PER-255) consistently demonstrated enhanced proliferation when incubated with rhGH (132.1 +/- 13.4%, P < 0.01). Growth hormone has been associated with an increased incidence of leukemia and may be implicated in the late relapse of this child. The use of growth hormone in children with a past history of ALL needs to be examined critically in the light of the potential risk of inducing leukemic relapse.

Detection of MYCN amplification in three neuroblastoma cell lines by non-radioactive chromosomal in situ hybridization

A non-radioactive chromosomal in situ hybridization technique utilizing a biotin-streptavidin-polyalkaline-phosphatase complex was successfully applied to three neuroblastoma cell lines for detection of MYCN amplification. These cell lines, designated PER-106, PER-107, and PER-108, were derived from consecutive bone marrow samples taken from a patient with stage IV neuroblastoma. The cell line derived at diagnosis (PER-106) exhibited MYCN amplification in the form of variable numbers of double-minute chromosomes, small fragments, and rings of varying sizes. This observed variability of MYCN amplification may explain the reported heterogeneity of both MYCN mRNA and protein expression among individual cells of some neuroblastomas. The cell lines derived from subsequent samples (PER-107 and PER-108) contained amplified MYCN as two consistent homogeneously staining regions in every cell. These were located on the short arms of chromosomes 6 and 14. Thus, amplified MYCN was identified in each cell line and demonstrated the concurrent evolution of amplification with cytogenetic abnormalities.

Two malignant peripheral primitive neuroepithelial tumor cell lines established from consecutive samples of one patient: characterization and cytogenetic analysis

A 6-year-old girl presented with a tumor of the right shoulder involving bone, adjacent soft tissue, and regional lymph nodes. The conventional histologic diagnosis was ambiguous, initially suggesting lymphoma. After relapse on lymphoma therapy, reevaluation with additional multiple diagnostic techniques performed on the biopsy tissue and on two cell lines derived from the biopsies established the diagnosis of a primitive neuroepithelial tumor of bone and soft tissue. This was strongly supported by 1) focal rosette formation by the tumor cells and positive immunostaining for neuron-specific enolase and synaptophysin, with absent staining for leukocyte common antigen; 2) at the ultrastructural level, formation of cellular processes containing microtubules, a paucity of neurosecretory granules, absence of synaptic junctions, formation of long "intermediate" junctions between cells, and, in culture, widespread development of rosettes; 3) marked surface positivity to W 6/32 and negativity to HSAN 1.2 antibodies; and 4) elevated expression of MYC and lack of overexpression of MYCN oncogenes. Numerical and structural abnormalities were present in the karyotype, but the expected t(11;22)(q24;q12) was not present in the tumor-involved marrow or in either of the established tumor cell lines, although there was an interstitial deletion of 11q involving breakpoints in q21 and q23.

Three neuroblastoma cell lines established from consecutive samples of one patient which show distinct morphologic features, MYCN amplification, and surface marker expression

Three neuroblastoma cell lines established from tumor samples obtained from one patient are described. The three lines were derived from bone marrow aspirates taken at diagnosis, and 13 and 15 months later. The origin of the cell lines PER-106, PER-107, and PER-108 from malignant neuroblasts was confirmed by electron microscopy studies, surface marker analysis, and assessment of MYCN amplification. Cell lines PER-107 and PER-108, which were established from tumor samples obtained at the time of progressive disease, have significantly shorter doubling times than PER-106 and grow mainly substrate-adherent, while cell line PER-106 (established from sample obtained at diagnosis) consists of small round neuroblastic cells which form large aggregates in suspension culture. The electron microscopy studies revealed distinctive neuroblast-like ultrastructure in all cell lines. The MYCN copy number was amplified (greater than 10 copies) in the established cell lines and in the fresh tumor samples and the relative abundance of MYCN RNA in the cell lines correlated roughly with the extent of the MYCN gene amplification. However, distinct phenotypic differences can be demonstrated among these three lines, which provide a model for the further examination of this highly malignant tumor. Detection of MYCN amplification by chromosomal in situ hybridization was performed on this set of cell lines, as reported by McRobert et al. (this issue, pages 128-134).

HOX11, a homeobox-containing T-cell oncogene on human chromosome 10q24

A common chromosomal abnormality in childhood T-cell acute leukemia is a translocation, t(10;14) (q24;q11), that together with the variant t(7;10)(q35;q24) is present in up to 7% of this tumor type. The gene adjacent to the 10q24 region is transcriptionally activated after translocation to either TCRD (14q11) or TCRB (7q35). It encodes a homeobox gene closely related to the developmentally regulated homeotic genes of flies and mammals. The coding capacity of this activated gene, designated HOX11, is undisturbed in a T-cell line carrying the translocation t(7;10)(q35;q24). Therefore, the HOX11 homeobox gene seems to be involved in T-cell tumorigenesis.