TEL is one of the targets for deletion on 12p in many cases of childhood B-lineage acute lymphoblastic leukemia

Abnormalities of the short arm of chromosome 12 including loss of heterozygosity (LOH) and TEL/AML-1 fusion resulting from a t(12;21)(p13;q22) translocation are frequently observed in childhood acute lymphoblastic leukemia (ALL). We investigated 21 DNA samples of childhood ALL which had LOH at 12p13. Rearrangement of TEL was observed in eight cases and another case showed a homozygous deletion of TEL. Two informative samples with TEL rearrangement had a deletion localized to the 5' region of this gene. The deletion in these two cases includes the helix-loop-helix (HLH) domain. This is consistent with the hypothesis that the normal tel can heterodimerize with the TEL/AML-1 gene product and inhibit the transforming capacity of the chimeric protein. Presumably, loss of the HLH of the normal remaining TEL allele abrogates this tumor suppressor-like function. The case with homozygous deletion of TEL is also consistent with this gene having qualities of a tumor suppressor. One unusual case had T-ALL rather than B-lineage ALL and the leukemic cells had rearrangement of TEL, but they did not have an alteration of the remaining TEL allele suggesting that the etiology of this disease may be different. This analysis further emphasizes the importance of loss of the normal TEL allele in childhood precursor B-lineage ALL.

Yolk sac angiogenic defect and intra-embryonic apoptosis in mice lacking the Ets-related factor TEL

The TEL gene, which is frequently rearranged in human leukemias of both myeloid and lymphoid origin, encodes a member of the Ets family of transcription factors. The TEL gene is widely expressed throughout embryonic development and in the adult. To determine the requirement for the TEL gene product in development we generated TEL knockout mice (TEL-/-) by gene targeting in embryonic stem cells. TEL-/- mice are embryonic lethal and die between E10.5-11.5 with defective yolk sac angiogenesis and intra-embryonic apoptosis of mesenchymal and neural cells. Two-thirds of TEL-deficient yolk sacs at E9.5 lack vitelline vessels, yet possess capillaries, indicative of normal vasculogenesis. Vitelline vessels regress by E10.5 in the remaining TEL-/- yolk sacs. Hematopoiesis at the yolk sac stage, however, appears unaffected in TEL-/- embryos. Our findings demonstrate that TEL is required for maintenance of the developing vascular network in the yolk sac and for survival of selected cell types within the embryo proper.

Molecular biology of acute myeloid leukemia

Clonal chromosome translocations, deletions, and inversions have been repeatedly observed for decades in approximately two thirds of all cases of acute myeloid leukemia (AML). With the dramatic advances in molecular biology that have occurred during the past two decades, these structural cytogenetic abnormalities have now provided invaluable clues as to the location of genes known or suspected of inducing leukemia. In most instances, leukemogenesis in AML results from gene fusion, when segments from two different genes are fused together to give rise to a chimeric structure consisting of the 5' end of one gene and the 3' end of another. Exceptions to this, however, do exist. In cases of AML that lack cytogenetic abnormalities, investigators are now also beginning to elucidate the genes involved in malignant transformation. Together, these observations support the notion that AML is heterogeneous at the molecular level, and suggest that clinicians will need to continue to take cytogenetic and molecular characteristics into consideration to optimize patient therapy.

Idiopathic thrombocytopenic purpura following allogeneic bone marrow transplantation--treatment with anti-D immunoglobulin

A 38-year-old man developed idiopathic thrombocytopenic purpura (ITP) 8 months following allogeneic BMT while being treated for cGVHD with corticosteroids and tacrolimus (FK506). He received two courses of high-dose intravenous immunoglobulin (IvIG) which resulted in transient improvement. A single dose of intravenous anti-D immunoglobulin induced a durable response. Anti-D immunoglobulin is better tolerated, less complicated to administer, and less expensive than a course of IvIG.

The TEL/platelet-derived growth factor beta receptor (PDGF beta R) fusion in chronic myelomonocytic leukemia is a transforming protein that self-associates and activates PDGF beta R kinase-dependent signaling pathways

The TEL/PDGF beta R fusion protein is the product of the t(5;12) translocation in patients with chronic myelomonocytic leukemia. The TEL/PDGF beta R is an unusual fusion of a putative transcription factor, TEL, to a receptor tyrosine kinase. The translocation fuses the amino terminus of TEL, containing the helix-loop-helix (HLH) domain, to the transmembrane and cytoplasmic domain of the PDGF beta R. We hypothesized that TEL/PDGF beta R self-association, mediated by the HLH domain of TEL, would lead to constitutive activation of the PDGF beta R tyrosine kinase domain and cellular transformation. Analysis of in vitro-translated TEL/ PDGF beta R confirmed that the protein self-associated and that self-association was abrogated by deletion of 51 aa within the TEL HLH domain. In vivo, TEL/PDGF beta R was detected as a 100-kDa protein that was constitutively phosphorylated on tyrosine and transformed the murine hematopoietic cell line Ba/F3 to interleukin 3 growth factor independence. Transformation of Ba/F3 cells required the HLH domain of TEL and the kinase activity of the PDGF beta R portion of the fusion protein. Immunoblotting demonstrated that TEL/PDGF beta R associated with multiple signaling molecules known to associate with the activated PDGF beta R, including phospholipase C gamma 1, SHP2, and phosphoinositol-3-kinase. TEL/PDGF beta R is a novel transforming protein that self-associates and activates PDGF beta R-dependent signaling pathways. Oligomerization of TEL/PDGF beta R that is dependent on the TEL HLH domain provides further evidence that the HLH domain, highly conserved among ETS family members, is a self-association motif.

TEL/AML-1 dimerizes and is associated with a favorable outcome in childhood acute lymphoblastic leukemia

Polymerase chain reaction-based screening of childhood acute lymphoblastic leukemia (ALL) samples showed that a TEL/AML1 fusion transcript was detected in 27% of all cases, representing the most common known gene rearrangement in childhood cancer. The TEL/AML1 fusion results from a t(12;21)(p13;q22) chromosomal translocation, but was undetectable at the routine cytogenetic level. TEL/AML1-positive patients had exclusively B-lineage ALL, and most patients were between the ages of 2 and 9 years at diagnosis. Only 3/89 (3.4%) adult ALL patients were TEL/AML1-positive. Most importantly, TEL/AML1-positive children had a significantly lower rate of relapse compared with TEL/AML1-negative patients (0/22 v 16/54, P = .004). Co-immunoprecipitation experiments demonstrated that TEL/AML-1 formed homodimers in vitro, and heterodimerized with the normal TEL protein when the two proteins were expressed together. The elucidation of the precise mechanism of transformation by TEL/AML1 and the role of TEL/AML1 testing in the treatment of childhood ALL will require additional studies.

p210BCR/ABL, p190BCR/ABL, and TEL/ABL activate similar signal transduction pathways in hematopoietic cell lines

The Philadelphia chromosome translocation generates a chimeric oncogene, BCR/ABL which causes chronic myelogenous leukemia. Two different fusion proteins can be produced, p190BCR/ABL and p210BCR/ABL, depending on the location of the breakpoint in BCR. Although the ABL tyrosine kinase activity of the resulting oncoprotein is essential for transformation, the exact functional contribution of BCR to transformation is unclear. A novel oncogene containing ABL is formed by the (9;12) translocation which fuses part of the ets-family member TEL to c-ABL in patients with acute leukemia. In an effort to compare the biological effects of various ABL oncogenes, we transformed two different factor-dependent murine hematopoietic cell lines with cDNA's encoding p210BCR/ABL, p190BCR/ABL, or TEL/ABL. Transfection of each of the three activated ABL oncogenes resulted in rapid emergence of growth factor-independence, and 2-4 sublines from each cell line with each oncogene were further studied. Each oncogene induced an increase in the tyrosine phosphorylation of cellular proteins and autophosphorylation of the oncoprotein itself. Overall, the pattern of increased tyrosine phosphorylation was similar in the cell lines, suggesting that many of the major substrates were identical. We specifically examined a series of proteins known to be p210BCR/ABL substrates, including rasGAP, Shc, SH-PTP2, SH-PTP1, CRK-L, CBL, paxillin, and STATs, and found that each were also tyrosine phosphorylated in response to p190BCR/ABL and TEL/ABL. These results suggest that the function of BCR can be largely replaced by the unrelated protein TEL with regards to transformation of murine hematopoietic cell lines to factor-independence, and support the hypothesis that a major contribution of both fusion partners is to activate the ABL tyrosine kinase.

Oligomerization of the ABL tyrosine kinase by the Ets protein TEL in human leukemia

TEL is a member of the Ets family of transcription factors which are frequently rearranged in human leukemia. The mechanism of TEL-mediated transformation, however, is unknown. We report the cloning and characterization of a chromosomal translocation associated with acute myeloid leukemia which fuses TEL to the ABL tyrosine kinase. The TEL-ABL fusion confers growth factor-independent growth to the marine hematopoietic cell line Ba/F3 and transforms Rat-1 fibroblasts and primary murine bone marrow cells. TEL-ABL is constitutively tyrosine phosphorylated and localizes to the cytoskeleton. A TEL-ABL mutant containing an ABL kinase-inactivating mutation is not constitutively phosphorylated and is nontransforming but retains cytoskeletal localization. However, constitutive phosphorylation, cytoskeletal localization, and transformation are all dependent upon a highly conserved region of TEL termed the helix-loop-helix (HLH) domain. TEL-ABL formed HLH-dependent homo-oligomers in vitro, a process critical for tyrosine kinase activation. These experiments suggest that oligomerization of TEL-ABL mediated by the TEL HLH domain is required for tyrosine kinase activation, cytoskeletal localization, and transformation. These data also suggest that oligomerization of Ets proteins through the highly conserved HLH domain may represent a previously unrecognized phenomenon.

Nonrandom X-inactivation patterns in normal females: lyonization ratios vary with age

The utility of X-inactivation based clonality assays for evaluation of human neoplasia is well-documented. However, excessive Lyonization is a potential limitation of these assays, because it mimics clonal derivation of cells. The incidence of excessive Lyonization in healthy females is controversial, with reported incidence varying from 4% to 33%. Several explanations have been offered for the observed variation, including different criteria for excessive Lyonization, diversity of X-linked clonality assays, small population sizes and more recently, tissue specificity of X-inactivation patterns. However, it is also possible that stem cell depletion, clonal hematopoiesis, or selection pressures on blood cells results in an increased incidence of excessive skewing. If any of the latter is true, then the incidence of excessive skewing should increase with age in blood cells. To test this hypothesis, we determined X-inactivation ratios at the human androgen receptor locus of 295 normal females from three age groups: (1) neonates, (2) females 28 to 32 years old and, (3) females aged > or = 60 years. The incidence of skewing (allele ratios > or = 3:1) was 8.6% (14 of 162) in neonates (P = .104 v 28 to 32); 16.4% (11/67) in 28 to 32 y.o. (P = .0064 v > or = 60), and 37.9% (25 of 66) in women > or = 60 y.o. (P < .0001 v neonates). When a more stringent criterion for skewing was used (allele ratios > or = 10:1), the incidence was 1.9% (3 of 162) in neonates (P = .362 v 28 to 32), 4.5% (3 of 67) in 28 to 32 y.o. (P = .0022 v > or = 60), and 22.7% (15 of 66) in > or = 60 y.o. group (P < .0001 v neonates). Results have been confirmed at the phosphoglycerate kinase locus for 48 heterozygous females. The incidence of excessive skewing increases with age. In neonates, the incidence is low and may correspond to true excessive Lyonization. Acquired skewing occurs with aging in normal females and is present in 38% of females over the age of 60. Further studies are needed to determine whether acquired skewing is a consequence of stem cell depletion, true clonal hematopoiesis, growth advantage conferred by parental-specific X-chromosomes, or other causes. These data provide an explanation for variation in reported incidence of excessive skewing in normal females. Furthermore, these findings suggest that any study of clonality using X-inactivation based assays should incorporate age-matched controls for Lyonization.

Linkage of a familial platelet disorder with a propensity to develop myeloid malignancies to human chromosome 21q22.1-22.2

Linkage analysis was performed on a large pedigree with an autosomal dominant platelet disorder and a striking propensity in affected family members to develop hematologic malignancy, predominantly acute myelogenous leukemia. We report the linkage of the autosomal dominant platelet disorder to markers on chromosome 21q22. Four genetic markers completely cosegregate with the trait and yield maximum logarithm of difference scores ranging from 4.9 to 10.5 (theta = .001). Two flanking markers, D21S1265 and D21S167, define a critical region for the disease locus of 15.2 centimorgan. Further analysis of this locus may identify a gene product that affects platelet production and function and contributes to the molecular evolution of hematologic malignancy.

The PGK-PCR clonality assay (PPCA)

The PGK-PCR assay offers an accurate method for determination of clonal derivation of cells in females who are heterozygous for the PGK BstXI polymorphism. Techniques to screen for heterozygosity and determine clonality using polymerase chain reaction based techniques are provided.

The t(12;21) translocation converts AML-1B from an activator to a repressor of transcription

The t(12;21) translocation is present in up to 30% of childhood B-cell acute lymphoblastic and fuses a potential dimerization motif from the ets-related factor TEL to the N terminus of AML1. The t(12;21) translocation encodes a 93-kDa fusion protein that localizes to a high-salt- and detergent-resistant nuclear compartment. This protein binds the enhancer core motif, TGTGGT, and interacts with the AML-1-binding protein, core-binding factor beta. Although TEL/AML-1B retains the C-terminal domain of AML-1B that is required for transactivation of the T-cell receptor beta enhancer, it fails to activate transcription but rather inhibits the basal activity of this enhancer. TEL/AML-1B efficiently interferes with AML-1B dependent transactivation of the T-cell receptor beta enhancer, and coexpression of wild-type TEL does not reverse this inhibition. The N-terminal TEL helix-loop-helix domain is essential for TEL/AML-1B-mediated repression. Thus, the t(12;21) fusion protein dominantly interferes with AML-1B-dependent transcription, suggesting that the inhibition of expression of AML-1 genes is critical for B-cell leukemogenesis.

Analysis of meningiomas by methylation- and transcription-based clonality assays

The clonal derivation of tumors can be determined by X chromosome inactivation analysis based on differential expression of genes or differential methylation of cytosine residues in CpG islands near polymorphic loci. In this report, we compared a transcription-based RNA analysis with a methylation-based DNA assay to determine clonality of meningiomas. Both clonality assays use PCR-based analysis at the hunan androgen-receptor gene (HUMARA) on the X chromosome. Among 23 meningiomas from female patients, 19 were informative heterozygotes at this locus (83%). The patterns of X chromosome inactivation in four patients were extremely skewed towards one allele in blood (unequal Lyonization), which precluded clonality determination in the tumor samples. Concordant clonality results with methylation- and transcription-based clonality assays were demonstrated in 9 of 13 informative tumors expressing the androgen receptor. Seven meningiomas were monoclonal, but surprisingly, two pathologically documented cases of meningiomas were polyclonal. There was disparity in 4 of 13 tumor specimens that were polyclonal by the methylation-based assay but monoclonal by the transcription assay. Clonality examination of these tumors by the methylation-based phosphoglycerate kinase assay provided identical results to the methylation-based analysis at the HUMARA locus. In addition, loss of heterozygosity (LOH) studies of chromosome 22, which is frequently deleted in meningiomas, showed that four of four informative samples of the six polyclonal tumors had partial LOH in tumor tissues. However, complete LOH was observed in primary cultured cells, which were also monoclonal by the methylation assay. Taken together, these data suggest that the disparity of the two assays in these four cases may be due to differences in the level of expression of the androgen receptor gene in tumors. Therefore, we conclude that: (a) clonal derivation of meningiomas determined by both transcription- and methylation-based clonality assays are in full agreement in many (9 of 13) but not all cases (4 of 13); and (b) most meningiomas (9 of 15) are monoclonal in origin, whereas some meningioma samples (6 of 15) are polyclonal or may contain heterogeneous components.

TEL and KIP1 define the smallest region of deletions on 12p13 in hematopoietic malignancies

Unbalanced translocations as well as interstitial deletions of the short arm of chromosome 12 [del(12p)] are found as recurring chromosomal changes in a broad spectrum of hematopoietic malignancies. These changes result in the hemizygous deletion of genetic material from 12p. We mapped a yeast artificial chromosome containing the TEL gene, a cosmid contig containing part of TEL and a P1 contig containing the KIP1 gene to 12p13. These probes were used for fluorescence in situ hybridization to analyze samples from 47 patients with various hematologic malignancies who had unbalanced translocations (25 patients) leading to loss of 12p or deletions (22 patients) involving 12p13. The patients had acute lymphoblastic leukemia (8 cases), myelodysplastic syndrome (MDS; 11 cases), acute myeloid leukemia (AML; 10 cases), myeloproliferative disorders (4 cases), therapy-related MDS or AML (7 cases), non-Hodgkin's lymphoma (2 cases), and other hematopoietic malignancies (5 cases). All three probes were hemizygously detected in 26 cases and were completely retained in only 9 cases. In 12 cases probes for one of the two genes were deleted, allowing us to map the smallest region of overlap of these deletions to a small genomic region that is bordered on the telomeric side by the TEL gene and on the centromeric side by KIP1. The genomic distance between TEL and KIP1 is estimated to be about 1 to 2 Mbp.

Myelodysplastic syndrome

Myelodysplastic syndrome continues to present a formidable clinical challenge. Despite considerable effort, no therapy apart from allogeneic bone marrow transplantation has been shown to prolong survival. Lack of effective therapy for myelodysplastic syndrome is of further concern given recent reports on the high incidence of myelodysplastic syndrome in patients undergoing intensive chemotherapy and radiation therapy for other malignancies. However, significant strides have been made in the past year toward understanding the molecular pathogenesis of some forms of myelodysplastic syndrome, as well as developing new approaches for therapy of myelodysplastic syndrome. This review highlights recent advances in the molecular genetics of myelodysplastic syndrome, including clonality analysis and identification of genes that are causally implicated in the pathogenesis of myelodysplastic syndrome; results from recent clinical trials for therapy of myelodysplastic syndrome using growth factors, chemotherapy or both; and recent literature on therapy-related myelodysplastic syndrome in intensively treated patients.

Fusion of the TEL gene on 12p13 to the AML1 gene on 21q22 in acute lymphoblastic leukemia

Chromosomal rearrangements involving band 12p13 are found in a wide variety of human leukemias but are particularly common in childhood acute lymphoblastic leukemia. The genes involved in these rearrangements, however, have not been identified. We now report the cloning of a t(12;21) translocation breakpoint involving 12p13 and 21q22 in two cases of childhood pre-B acute lymphoblastic leukemia, in which t(12;21) rearrangements were not initially apparent. The consequence of the translocation is fusion of the helix-loop-helix domain of TEL, an ETS-like putative transcription factor, to the DNA-binding and transactivation domains of the transcription factor AML1. These data show that TEL, previously shown to be fused to the platelet-derived growth factor receptor beta in chronic myelomonocytic leukemia, can be implicated in the pathogenesis of leukemia through its fusion to either a receptor tyrosine kinase or a transcription factor. The TEL-AML1 fusion also indicates that translocations affecting the AML1 gene can be associated with lymphoid, as well as myeloid, malignancy.

Clonality in juvenile chronic myelogenous leukemia

Juvenile chronic myelogenous leukemia (JCML) is a myeloproliferative disease in which morbidity and mortality are primarily caused by nonhematopoietic organ failure from myelomonocytic infiltration or by failure of the normal bone marrow. Morphologic evidence of maturation arrest, karyotypic abnormalities, and progression to blast crisis are infrequent events. Viral infections and other reactive processes can initially mimic the clinical course of JCML, creating diagnostic problems. Because of the rarity of JCML and technical limitations, formal clonality studies have not been reported previously. Nine female JCML patients were identified by clinical criteria, characteristic 'spontaneous' in vitro cell growth, and negative cultures and titers for various viral agents. Peripheral blood and bone marrow samples were obtained at the time of diagnosis for cell separation and RNA and DNA isolation. To assess clonality, X-chromosome inactivation patterns were evaluated using three different, recently developed polymerase chain reaction-based clonality assays. All nine female JCML patients showed evidence for monoclonal origin of mononuclear cells at the time of diagnosis. Cell separation studies further traced the monoclonal origin back to at least the most primitive myeloid progenitor cell. Reversion to a polyclonal state was demonstrated after bone marrow transplant and also in one patient following treatment with 13-cis retinoic acid. This demonstration of clonality in JCML delineates it from the reactive processes and provides a basis for molecular genetic strategies to identify causally associated mutations.

Recombinant human interleukin-1 receptor antagonist in the treatment of steroid-resistant graft-versus-host disease

Acute graft-versus-host disease (GVHD) that is resistant to therapy is a highly lethal complication of marrow transplantation. Inflammatory cytokines such as interleukin-1 (IL-1) may be critical mediators of this process. If so, specific inhibition of IL-1 activity with recombinant human IL-1 receptor antagonist (IL-1Ra), a naturally occurring competitive inhibitor of IL-1, may ameliorate acute GVHD. We performed an open-label, phase I/II trial to evaluate the safety and efficacy of IL-1Ra in 17 patients with steroid-resistant GVHD. The IL-1Ra was administered as a 24-hour continuous infusion over 7 days. The dose was escalated in cohorts of patients from 400 to 3,200 mg/d. Acute GVHD was evaluated in each affected organ and as an overall grade. Stage-specific improvement of acute GVHD occurred in the skin (8 of 14, 57%), gut (9 of 11, 82%), and liver (2 of 11, 18%). Overall, acute GVHD improved by at least one grade in 10 of 16 (63%) patients. Response to therapy was associated with a reduction of tumor necrosis factor-alpha (TNF-alpha) mRNA levels in blood mononuclear cells (P = .001). The only toxicity attributable to IL-1Ra was reversible transaminase elevation in two patients. Inhibition of IL-1 activity with IL-1Ra is safe and has demonstrable efficacy in acute GVHD that failed to respond to conventional treatment. These data provide further evidence that IL-1 is a mediator of GVHD.

Langerhans'-cell histiocytosis (histiocytosis X)--a clonal proliferative disease

BACKGROUND

The lesions of Langerhans'-cell histiocytosis (histiocytosis X), a proliferative histiocytic disorder of unknown cause, contain histiocytes similar in phenotype to dendritic Langerhans' cells. The disease ranges in severity from a fatal leukemia-like disorder to an isolated lytic lesion of bone. Intermediate forms of the disease are usually characterized by multiorgan involvement, diabetes insipidus, and a chronic course.

METHODS

To determine whether Langerhans' histiocytosis is a polyclonal reactive disease or a clonal disorder, we used X-linked polymorphic DNA probes (HUMARA, PGK, M27 beta[DXS255], and HPRT) to assess clonality in lesional tissues and control leukocytes from 10 female patients with various forms of the disease. Lymphoid clonality was also assessed by analysis of rearrangements at immunoglobulin and T-cell-receptor gene loci.

RESULTS

The HUMARA assay detected clonal cells in the lesions of 9 of the 10 patients: 3 patients had acute disseminated disease, 3 had unifocal disease, and 3 had intermediate forms. The percentage of clonal cells closely approximated the percentage of CD1a-positive histiocytes in each lesion. Clonality was also confirmed in two of nine cases with the PGK or M27 beta probe. Extreme constitutional lyonization precluded assessment of clonality in the 10th case. Lymphoid clonality was ruled out in all cases.

CONCLUSIONS

The detection of clonal histiocytes in all forms of Langerhans'-cell histiocytosis indicates that this disease is probably a clonal neoplastic disorder with highly variable biologic behavior. Thus, genetic mutations that promote clonal expansion of Langerhans' cells or their precursors may now be identified.

Fusion of PDGF receptor beta to a novel ets-like gene, tel, in chronic myelomonocytic leukemia with t(5;12) chromosomal translocation

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome characterized by abnormal clonal myeloid proliferation and by progression to acute myelogenous leukemia (AML). CMML thus offers an opportunity to study early genetic events in the transition to AML. A recently recognized subgroup of CMML has a t(5;12)(q33;p13) balanced translocation. We report that the consequence of the t(5;12) translocation is expression of a fusion transcript in which the tyrosine kinase domain of the platelet-derived growth factor receptor beta (PDGFR beta) on chromosome 5 is coupled to a novel ets-like gene, tel, on chromosome 12. The tel-PDGFR beta fusion demonstrates the oncogenic potential of PDGFR beta and may provide a paradigm for early events in the pathogenesis of AML.

Human pituitary adenomas show no loss of heterozygosity at the retinoblastoma gene locus

The retinoblastoma tumor suppressor gene (RB1) is inactivated in hereditary and sporadic forms of retinoblastoma as well as in a number of other sporadic tumors. The majority of human pituitary tumors have been shown to be monoclonal neoplasms, suggesting that 1 or more somatic mutations are involved in the clonal expansion of a single progenitor cell. Recently, a high percentage of transgenic mice containing a disrupted RB1 allele have been shown to develop pituitary tumors. To investigate whether RB1 inactivation contributes to the development of human pituitary adenomas, we searched for loss of heterozygosity (LOH) within the RB1 gene locus in a variety of human pituitary adenomas. We screened 34 adenomas for LOH using a polymerase chain reaction (PCR)-based microsatellite polymorphic marker at the RB1 gene locus. In addition, a variable number of tandem repeat markers from within the RB1 gene was also used to search for LOH in 14 tumors. We found no LOH or microsatellite instability at the RB1 locus in any of the informative cases (30 of 34). Additionally, we showed that 4 representative adenomas from female patients are monoclonal in origin using a PCR-based clonality analysis assay. We conclude that the RB1 gene shows no LOH in a variety of human pituitary adenomas and that PCR-based microsatellite markers can serve as a useful tool for LOH analysis in human pituitary tumors.

An expression based clonality assay at the human androgen receptor locus (HUMARA) on chromosome X

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Clonality analysis of childhood ALL in remission: no evidence of clonal hematopoiesis

We studied 98 female patients in remission (2-240 months) from childhood ALL to determine the clonality status of their hematopoiesis. Thirty-one (31.6%) were heterozygous at the PGK locus for the BstX1 endonuclease restriction site, permitting X-linked clonality assays to be performed. Two patients were in relapse at the time of study and were excluded. We used the PGK-PCR clonality assay (PPCA) to analyze DNA from PMN and mononuclear cells of the remaining 29 female patients. All (29/29) patients demonstrated polyclonal hematopoiesis. These data show that remission from childhood ALL involves reestablishment of polyclonally derived hematopoiesis in all patients studied.

Bone marrow dysplasia in patients with newly diagnosed acute myelogenous leukemia does not correlate with history of myelodysplasia or with remission rate and survival

BACKGROUND

The records and initial bone marrow studies of 106 patients with newly diagnosed acute myelogenous leukemia (AML) were analyzed retrospectively to determine whether bone marrow dysplasia was predictive of a previous myelodysplastic disorder or correlated with remission rate and survival.

METHODS

Bone marrow aspirates and biopsy specimens were reviewed in a blinded fashion; dysplasia was assessed in as objective a manner as possible by numerically scoring nine specific findings: erythrocyte multinuclearity, nuclear fragmentation, megaloblastic characteristics, leukocyte granulation abnormalities and nuclear malformations, Pelger-Huet cells, and megakaryocytic dysplasia (mononuclear megakaryocytes, micromegakaryocytes, and megakaryocytes with multiple distinct nuclei).

RESULTS

Dysplasia of the megakaryocytic line was seen in 34% of patients; 70% of the patients had erythrocyte dysplasia; and 68% had leukocyte dysplasia. Pelger-Huet cells were seen in bone marrow of 35% of the patients. Overall dysplasia score and specific dysplastic findings such as Pelger-Huet cells did not correlate with a known history of myelodysplasia (P = 0.47), cytogenetic abnormalities (P = 0.35), prior chemotherapy treatment with or without alkylating agents (P = 1.00), previous malignant disorders such as polycythemia vera (P = 1.00), remission rate (P = 0.93), or survival (P = 0.42). Multivariate analysis confirmed known independent risk factors for remission in this patient population, including age (P = 0.04), history of prior chemotherapy (P = 0.04), abnormalities in chromosomes 5, 7, or 8 (P = 0.02), and type of antileukemia therapy (P < 0.001).

CONCLUSIONS

Bone marrow dysplasia is common in patients with AML and does not correlate with a history of myelodysplasia or predict outcome when patients are treated with standard intensive AML therapy.

Interleukin-1 is a critical effector molecule during cytokine dysregulation in graft versus host disease to minor histocompatibility antigens

Cytokines are believed to cause a number of inflammatory diseases. We have investigated the role of 3 inflammatory cytokines, IL-1, IL-2, and TNF alpha, during graft-versus-host disease (GVHD), a paradigm disease of cytokine dysregulation in vivo. Measuring cytokine mRNA transcripts with a quantitative polymerase chain reaction technique, we demonstrate that IL-1 transcript levels are increased several hundred-fold in GVHD target organs, whereas TNF alpha transcripts increase only 4- to 6-fold. Kinetic studies during the first month after transplant unexpectedly show that GVHD never induces IL-2 transcripts in the skin and only induces IL-2 transcripts in the spleen during the first week, whereas levels of IL-1 transcripts continue to increase throughout the entire 4 weeks. Administration of an IL-1 receptor antagonist after the termination of the IL-2 response and after the establishment of GVHD significantly increases long-term survival, confirming the central role of IL-1 as an effector molecule of GVHD and suggesting new therapeutic strategies for this disorder.

Prognostic factors for treatment outcome in autotransplantation of intermediate-grade and high-grade non-Hodgkin's lymphoma with cyclophosphamide, carmustine, and etoposide

PURPOSE

We examined a consecutive series of 78 patients with non-Hodgkin's lymphoma treated on prospective protocols with high-dose cyclophosphamide, carmustine (BCNU), and etoposide (CBV) plus autotransplantation to determine prognostic factors for time to treatment failure.

PATIENTS AND METHODS

Patients with relapsed, refractory, or poor-risk intermediate- and high-grade non-Hodgkin's lymphoma were treated with CBV with autologous marrow or peripheral-blood progenitor cell support. Patient characteristics before transplantation were examined in univariate analyses by the log-rank test and simultaneously in a Cox proportional hazards regression analysis. A best-predictive model was determined from those variables significant (P < .10) in the univariate test.

RESULTS

In univariate analysis, intermediate-grade and immunoblastic lymphoma, responsiveness to pretransplant salvage chemotherapy, and transplantation after primary therapy (first complete response [CR] or partial response [PR]) were associated with prolonged time to treatment failure. In proportional hazards multiple regression analysis, intermediate-grade and immunoblastic histology, responsive disease, and autotransplantation in first CR or PR were positive prognostic factors, and these characteristics are the basis of the best-predictive model for prolonged time to failure. Actuarial 3-year failure-free survival of patients with stable or responding disease at autotransplant was 54%.

CONCLUSION

CBV is an effective conditioning regimen in intermediate-grade and immunoblastic non-Hodgkin's lymphoma. Patients with these histologies transplanted while responding to primary therapy, or those with stable disease or disease responding to salvage therapy at the time of autotransplant, are most likely to benefit. Patients with lymphoblastic lymphoma or diffuse undifferentiated lymphoma did poorly with CBV and should be offered alternative therapy.

Clonality in myeloproliferative disorders

The myeloproliferative disorders are a group of hematologic diseases that are believed to arise from somatic mutations in an early hematopoietic stem cell. This statement is based on the demonstration of monoclonal involvement of terminally differentiated myeloid and lymphoid elements. The techniques for establishing clonal derivation of cells are discussed and the application of these techniques to myeloproliferative diseases is reviewed. The evidence for limited myeloid involvement, lineage heterogeneity, in some patients with myeloproliferative disorders is summarized.

Clonality in myeloproliferative disorders: analysis by means of the polymerase chain reaction

The myeloproliferative syndromes are acquired disorders of hematopoiesis that provide insights into the transition from somatic cell mutation to neoplasia. The clonal origin of specific blood cells can be assessed in patients with X chromosome-linked polymorphisms, taking advantage of random inactivation of the X chromosome. We have adapted the PCR for determination of clonality on as few as 100 cells, including individual colonies grown in culture. Amplifying a polymorphic portion of the X chromosome-linked phosphoglycerate kinase (PGK) gene after selective digestion of the active X chromosome with a methylation-sensitive restriction enzyme gave results fully concordant with standard Southern blotting of DNA samples from normal (polyclonal) polymorphonuclear cells (PMN) as well as clonal PMN from patients with myelodysplastic syndrome and polycythemia vera (PCV). We have used this technique to demonstrate heterogeneity of lineage involvement in patients with PCV. The same clinical phenotype may arise from clonal proliferation of different hematopoietic progenitors.

Clonality in acquired hematologic disorders

Clonal populations of cells can be identified by a number of different independent approaches, including analyses of karyotype, gene rearrangements, deletions or point mutations, X-linked polymorphisms, and integration of virus into the genome. Assessment of clonality has yielded valuable and surprising clues to the pathogenesis of acquired hematologic disorders. In the myeloproliferative states, clonal expansion of a mutated pluripotent stem cell can induce production of blood cells having a normal phenotype. The transition to acute leukemia is often associated with additional mutations. A similar progression has also been noted in lymphoproliferative disorders, again supporting a multistep pathogenesis of malignancy. Thus, a mutation inducing clonal growth may be a necessary but not sufficient step in induction of malignancy.

Characterization of hybrid molecules containing fragment A from diphtheria toxin linked to concanavalin A or the binding subunit of ricin toxin

Earlier we described the synthesis of a toxic, disulfide-linked conjugate between Fragment A from diphtheria toxin (DTA) and the lectin concanavalin A (Con A). Here we report further characterization of this Con A-SS-DTA conjugate and of a nontoxic conjugate containing DTA linked through a disulfide bridge to the binding subunit of ricin toxin, RTB. The Con A-SS-DTA conjugate preparation was heterogeneous, and contained both divalent and tetravalent forms of Con A linked to DTA. The divalent form of the conjugate, which lacked hemagglutination activity, was as toxic as the tetravalent form for 3T3 cells. Consistent with this result, Con A-SS-DTA analogs prepared with the chemically modified dimeric derivatives of Con A, succinyl-Con A and acetyl-Con A, were as toxic as DTA disulfide linked to tetravalent Con A. Two analogs of Con A-SS-DTA containing nonreducible intermolecular linkages between DTA and Con A were at least 1000-fold less toxic than Con A-SS-DTA, although they were indistinguishable from unmodified Con A in binding to 3T3 cells. This suggests that reduction of the disulfide bridge between Con A and DTA may be necessary for conjugate toxicity. Con A-SS-DTA was equally toxic for a variety of cell lines varying in sensitivity to diphtheria toxin, including Vero, CHO, HeLa, and 3T3. The conjugate was also toxic for a diphtheria toxin-resistant variant of V79 cells (V79 Dtxr-3) that has lower affinity than wild type cells for diphtheria toxin. Chloroquine, colchicine, cytochalasin B, and ammonium chloride had no effect on Con A-SS-DTA toxicity for Vero cells, although ammonium chloride and chloroquine inhibited diphtheria toxin action.

A hybrid toxin containing fragment A from diphtheria toxin linked to the B protomer of cholera toxin

We have constructed and characterized a hybrid toxin containing the A chain of diphtheria toxin linked via a disulfide bridge to the B protomer of cholera toxin. Cholera toxin B protomer, previously derivatized with 4-5 cystaminyl groups per pentameric protomer, was reacted with reduced diphtheria toxin chain A to give the desired hybrid, containing an average of 2 molecules of diphtheria toxin chain A per cholera toxin B protomer. A concentration of 0.3 nM hybrid inhibited protein synthesis by 50% in 24 h in several cultured cell lines; thus the hybrid was about 10-fold more toxic than of a (diphtheria toxin chain A)-SS-(concanavalin A) conjugate described previously. Evidence was obtained that toxicity of the hybrid was dependent on the functional contributions of both the diphtheria toxin chain A and cholera toxin B protomer moieties.

Epidermal growth factor-toxin A chain conjugates: EGF-ricin A is a potent toxin while EGF-diphtheria fragment A is nontoxic

We have prepared a 2-pyridyl-dithiopropionate derivative of epidermal growth factor (EGF) and conjugated the derivative by disulfide interchange to the A chain of ricin (RTA) or to fragment A of diphtheria toxin (DTA). The EGF-RTA conjugate was toxic to 3T3 cells at concentrations (10(-9)--10(-11) M) similar to those at which EGF exerts its biological activity and within an order of magnitude of the toxicity of ricin. Ricin A chain alone only exerted toxic effects at concentrations (10(-6)--10(-7) M) three to four orders of magnitude higher than required for the activity of the EGF-RTA conjugate or ricin. An unconjugated mixture of RTA and EGF had no greater effect than RTA alone. Toxicity of the EGF-RTA conjugate on 3T3 cells was competed by EGF and was blocked by antibodies to RTA, but not by lactose or antibodies to the ricin B chain (RTB). In contrast to the EGF-RTA conjugate, the EGF-DTA conjugate proved virtually nontoxic at concentrations as high as 3 X 10(-8) M. Control experiments showed that the EGF-DTA conjugate retained EGF receptor binding activity; the DTA moiety of the hybrid retained ADP-ribosyltransferase activity; and the disulfide bridge linking DTA to EGF was readily reducible.

A model system involving anti-concanavalin A for antibody targeting of diphtheria toxin fragment A1

Results obtained in a model system strongly suggest that antibodies to cell surface determinants may be used to direct the toxic potential of the A chain of diphtheria toxin (DTA). The A chain (M.W. 21,000) was covalently attached to antibody against concanavalin A (anti-Con A) by means of a disulfide-containing cross-bridge. This DTA-SS-(anti-Con A) conjugate was toxic for 3T3 cells containing Con A on their surface but was not toxic in the same concentration range for: (a) cells lacking Con A; (b) Con A-treated cells washed with buffer containing alpha-methyl-D-mannoside; (c) cells containing wheat germ agglutinin on their surface; or (d) Con A-treated mutant Chinese hamster ovary cells containing altered, toxin-insensitive elongation factor 2. Conjugates containing DTA disulfide linked to anti-wheat germ agglutinin antibody or to nonspecific rabbit immunoglobulin G were not toxic for cells coated with Con A. The results suggest a new approach to the construction of antibody-directed, tumor-specific chemotherapeutic agents. Conjugates containing DTA disulfide linked to antibody against specific cell surface antigens may also be generally useful as specific selective agents for the isolation of mutant cell lines.

Antibody-directed cytotoxic agents: use of monoclonal antibody to direct the action of toxin A chains to colorectal carcinoma cells

We have constructed cell-specific cytotoxic agens by covalently coupling the A chain from diphtheria toxin or ricin toxin to monoclonal antibody directed against a colorectal carcinoma tumor-associated antigen. Antibody 1083-17-1A was modified by attachment of 3-(2-pyridyldithio)propionyl or cystaminyl groups and then treated with reduced A chain to give disulfide-linked conjugates that retained the original binding specificity of the antibody moiety. the conjugates showed cytotoxic activity for colorectal carcinoma cells in culture, but were not toxic in the same concentration range for a variety of cell lines that lacked the antigen. Under defined conditions virtually 100% of antigen-bearing cultured cells were killed, whereas cells that lacked the antigen were not affected. Conjugates containing toxin A chains coupled to monoclonal antibodies may be useful in studying functions of various cell surface components and, possibly, as tumor-specific therapeutic agents.

Chimeric toxins: toxic, disulfide-linked conjugate of concanavalin A with fragment A from diphtheria toxin

A disulfide-linked conjugate of concanavalin A (Con A) and fragment A from diphtheria toxin has been synthesized and shown to be toxic for HeLa (human), Chinese hamster ovary (CHO), and SV3T3 (murine) cells. The conjugate was constructed by first coupling cystamine to Con A with a carbodiimide reagent and then reacting the modified Con A with reduced fragment A under conditions promoting disulfide interchange. The desired conjugate, obtained in nearly 50% yield relative to input of fragment A, was purified by affinity chromatography on Sephacryl S-200 and NAD-Sepharose; on analysis, it gave an average of 1.4 molecules of fragment A per tetrameric Con A molecule. The conjugate proved to be about equally active in inhibiting protein synthesis in HeLa, CHO, or SV3T3 cells in culture but was inactive relative to controls in a toxin-resistant strain of CHO cells containing altered elongation factor 2, the target protein of fragment A. With toxin-sensitive strains the conjugate was 100- to 1000-fold more active than controls, including fragment A, cystaminyl-Con A, and mixtures thereof, but was 1/50th to 1/500th as toxic as diphtheria toxin itself. Similar activity relative to controls was observed after intradermal inoculations in rabbits, and intravenous injections of the conjugate were lethal for mice. The activity of the conjugate in tissue culture was inhibited by Con A or alpha-methylmannoside but not by galactose. This and similar conjugates should be useful in studying mechanisms of entry of biologically active proteins into cells.