Biomedical subjects

J H Kersey

Publications and source records attributed to J H Kersey.

At least 19 recordsLinked to original sources

PubMed1995

Molecular analysis of infant acute lymphoblastic leukemia: MLL gene rearrangement and reverse transcriptase-polymerase chain reaction for t(4; 11)(q21; q23).

Molecular techniques to detect MLL (11q23) and AF-4 (4q21) gene rearrangements are being evaluated for use in stratification of patients into prognostic groups. We studied 15 cases of infant acute lymphoblastic leukemia (ALL) with Southern blotting for MLL gene rearrangement and reverse transcriptase-polymerase chain reaction (RT-PCR) for t(4;11) fusion transcripts and compared the results to cytogenetic and clinical data. Our results indicate that classic t(4;11)(q21;q23) translocations are detected by RT-PCR; however, unusual 4;11 translocations still require additional investigation. We also extended and updated our original study of MLL gene rearrangement in infant ALL to 40 patients with longer follow-up and show that the group with germline configuration of the MLL gene continues to have an excellent outcome. The results of salvage therapy (bone marrow transplantation or chemotherapy) suggest that transplant may show advantage. Preliminary results of the use of RT-PCR to assess minimal disease are also reported.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1995

Acute lymphoblastic leukemias with deletion of 11q23 or a novel inversion (11)(p13q23) lack MLL gene rearrangements and have favorable clinical features.

Balanced translocations affecting the 11q23 region are among the most frequent chromosomal abnormalities in childhood acute lymphoblastic leukemia (ALL), comprising 5% to 6%. These cases consistently have a rearranged MLL gene and are associated with high-risk presenting features, hyperleukocytosis and younger age, and a poor treatment outcome. To assess the clinical and biologic significance of 11q23-associated structural chromosomal abnormalities other than translocations, we studied 17 cases of childhood ALL [14 with del(11)(q23) and 3 with inv(11)(p12q23)] that were identified among 785 cases with successful chromosome analysis. In contrast to reported cases with 11q23 and MLL gene rearrangement, our series was characterized by relatively low leukocyte counts (median, 15.1 x 10(9)/L), expression of CD10 antigen but not myeloid-associated CD15 and CDw65 antigens, a relatively high frequency of T-cell immunophenotypes, and a generally favorable prognosis. All 13 cases with interpretable molecular analysis lacked MLL gene rearrangements. We suggest that most cases with deletions or inversions affecting the 11q23 region represent clinically and biologically different entities as compared with those defined by 11q23 translocation.

Adolescent↗

PubMed1995

Unrelated donor bone marrow transplantation: influence of HLA A and B incompatibility on outcome.

We have studied the outcome of 211 consecutive unrelated donor (URD) bone marrow transplants (BMT) performed at the University of Minnesota (Minneapolis, MN) between May 1985 and December 1992. Ninety patients (43%) received marrow matched serologically at HLA A, B, and DR loci; 86 (41%) received marrow with a major and 32 (15%) marrow with a minor serologic mismatch at the HLA A or B locus. Multivariate analysis revealed that older age had an adverse effect on survival. In younger (age less than 18 years) recipients, survival after fully matched (A, B, and DR sub-type) or major mismatched (A or B locus), DR subtype-matched donor BMT was not significantly different (P = .4; survival: 53% v 41%, respectively, at 3 years). For adults, survival after matched donor BMT was significantly better than that with mismatched donors (P < .01; survival: 30% v 10%, respectively, at 3 years). Formal quality of life assessment by telephone interview demonstrated similar functional status in survivors of URD and related donor (RD) BMT at least 2 years post-BMT. URD BMT provides effective therapy for a variety of lethal hematopoietic diseases that rivals outcome of RD transplant in some cases. Use of URD marrow with a major mismatch at one HLA A or B locus is well tolerated in young, but not in older, recipients. These observations should be used to improve donor selection and counseling for URD BMT candidates.

Adolescent↗

PubMed1995

Hematopoietic growth factors for graft failure after bone marrow transplantation: a randomized trial of granulocyte-macrophage colony-stimulating factor (GM-CSF) versus sequential GM-CSF plus granulocyte-CSF.

Delay in hematologic recovery after bone marrow transplantation (BMT) can extend and amplify the risks of infection and hemorrhage, compromise patients' survival, and increase the duration and cost of hospitalization. Because current studies suggest that granulocyte-macrophage (GM) colony-stimulating factor (CSF) may potentiate the sensitivity of hematopoietic progenitor cells to G-CSF, we performed a prospective, randomized trial comparing GM-CSF (250 micrograms/m2/d x 14 days) versus sequential GM-CSF x 7 days followed by G-CSF (5 micrograms/kg/d x 7 days) as treatment for primary or secondary graft failure after BMT. Eligibility criteria included failure to achieve a white blood cell (WBC) count > or = 100/microL by day +21 or > or = 300/microL by day +28, no absolute neutrophil count (ANC) > or = 200/microL by day +28, or secondary sustained neutropenia after initial engraftment. Forty-seven patients were enrolled: 23 received GM-CSF (10 unrelated, 8 related allogeneic, and 5 autologous), and 24 received GM-CSF followed by G-CSF (12 unrelated, 7 related allogeneic, and 5 autologous). For patients receiving GM-CSF alone, neutrophil recovery (ANC > or = 500/microL) occurred between 2 and 61 days (median, 8 days) after therapy, while those receiving GM-CSF+G-CSF recovered at a similar rate of 1 to 36 days (median, 6 days; P = .39). Recovery to red blood cell (RBC) transfusion independence was slow, occurring 6 to 250 days (median, 35 days) after enrollment with no significant difference between the two treatment groups (GM-CSF: median, 30 days; GM-CSF+G-CSF; median, 42 days; P = .24). Similarly, platelet transfusion independence was delayed until 4 to 249 days (median, 32 days) after enrollment, with no difference between the two treatment groups (GM-CSF: median, 28 days; GM-CSF+G-CSF: median, 42 days; P = .38). Recovery times were not different between patients with unrelated donors and those with related donors or autologous transplant recipients. Survival at 100 days after enrollment was superior after treatment with GM-CSF alone. Only 1 of 23 patients treated with GM-CSF died versus 7 of 24 treated with GM-CSF+G-CSF who died 16 to 84 days (median, 38 days) after enrollment, yielding Kaplan-Meier 100-day survival estimates of 96% +/- 8% for GM-CSF versus 71% +/- 18% for GM-CSF+G-CSF (P = .026). These data suggest that sequential growth factor therapy with GM-CSF followed by G-CSF offers no advantage over GM-CSF alone in accelerating trilineage hematopoiesis or preventing lethal complications in patients with poor graft function after BMT.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1995

Development and characterization of three recombinant single chain antibody fragments (scFvs) directed against the CD19 antigen.

Antibodies that recognize antigens restricted to leukemia, lymphoma, and normal hematopoietic cells represent a unique opportunity to develop therapeutics, because they have the potential for relatively selective treatment of these diseases. Antibodies that recognize the CD19 antigen found on normal and malignant B cells, but not on stem cells, have been used to develop immunoconjugates. However, these conjugates are large and might be suboptimal in tumor penetration when compared to molecules using smaller single chain Fv (scFv) antibody fragments. scFv has the advantage of being a molecularly engineered homogeneous molecule. In this report, we demonstrate the cloning, expression, and binding of three anti-CD19 antibodies as scFvs. All three scFvs were successfully cloned and expressed. FVS191, derived from cell line B43, and FVS192, derived from SJ25C1, were properly refolded and bound CD19 antigen in FACS competition assays. These anti-CD19 scFv should be useful in the further development of diagnostic and therapeutic molecules.

Antibody Specificity↗

PubMed1995

Randomized comparison of cyclophosphamide-total body irradiation versus busulfan-cyclophosphamide conditioning in autologous bone marrow transplantation for acute myeloid leukemia.

PURPOSE: This prospective trial of autologous bone marrow transplantation for acute myeloid leukemia was undertaken to compare the outcome using two different preparative regimens. METHODS AND MATERIALS: Between October 1987 and April 1993, 35 patients with acute myeloid leukemia in first (n = 12) or greater (n = 23) remission were stratified by remission status and randomized to undergo 4-hydroperoxycyclophosphamide purged autologous bone marrow transplantation after either cyclophosphamide (120 mg/kg) and total body irradiation (1320 Gy in eight fractions over 4 days) (CY/TBI), or busulfan (16 mg/kg) and cyclophosphamide (200 mg/kg) (BU/CY) conditioning. RESULTS: At 2 years, overall survival and disease-free survival were 39% (95% confidence intervals (CI) 22-57%) and 36% (95% CI 19-52%), respectively. Patients in first complete remission had a significantly better outcome with a 2-year disease free survival of 57% (95% CI 28-86%) compared to others at 24% (95% CI 6-43%, log rank p = 0.048). For patients conditioned with CY/TBI, the estimated 2-year disease-free survival was 50% compared to 24% for patients conditioned with BU/CY (log rank p = 0.12). Estimated 2-year relapse rates were 43% vs. 70% (log rank p = 0.17), respectively. For patients in first complete remission no differences in disease-free survival (2-year estimates 67% vs. 50%, log rank p = 0.69), between the two regimens were observed. For patients in greater than first complete remission there was a trend towards improved disease-free survival in the CY/TBI arm (2-year estimates 42% vs. 9%, log rank p = 0.06). There were no differences in time to white blood cell count (WBC) engraftment, absolute neutrophil count of > 500, incidence of bacteremias, or median time to hospital discharge between the two regimens. Acute toxicities were similar. Interstitial pneumonitis developed in two patients (one on each arm), while veno occlusive disease developed in three BU/CY patients, but none of the CY/TBI patients (log rank p = 0.07). CONCLUSIONS: Cyclophosphamide-total body irradiation provided an equivalent or better outcome to BU/CY, particularly in advanced patients, and should remain the standard by which new regimens are judged. The high relapse rate with both regimens, especially patients who were in greater than in first complete remission, emphasizes the need for early transplant and for new strategies to improve outcome.

Adolescent↗

PubMed1995

A mapping study of 13 genes on human chromosome bands 4q11-->q25.

A chromosome band 4q21 gene (MLLT2, formerly called AF-4/FEL) involved in a reciprocal translocation with chromosome band 11q23 in t(4;11) acute leukemia has been cloned. To provide better definition of gene order and relationships in this region where MLLT2 resides, we used pulsed field gel electrophoresis (PFGE) to investigate 13 genes (including MLLT2) with physical locations in bands 4q11-->q25. Somatic cell hybrids derived from RS4;11, a leukemic cell line carrying the t(4;11)(q21;q23), were also used to localize genes in relation to MLLT2. Linkage of the interleukin 8 (IL8), albumin (ALB), and platelet factor 4 (PF4) genes was confirmed by NotI, SalI and SacII digests. The maximum distance between PF4 and ALB is 210 kb and between ALB and IL8 is 420 kb. The alcohol dehydrogenase, class I (ADH2, ADH3) gene cluster can be linked to the alcohol dehydrogenase, class III gene (ADH5) by SacII, NruI, and EagI digests. The maximum distance between them is 590 kb. Our study indicated that ALB, alpha-fetoprotein (AFP), PF4, beta-thromboglobulin (PPBP), GRO1 (encoding a cytokine also called melanoma growth-stimulatory activity), and IL8 genes can be physically linked. In this study the gamma-interferon induced protein 10 (INP10), bone morphogenetic protein 3 (BMP3), annexin III (ANX3), KIT, amphiregulin (AREG), immunoglobulin J polypeptide (IGJ), deoxycytidine kinase (DCK) and MLLT2 genes were not linked to one another or to the above two groups of genes. Our analysis using somatic cell hybrids combined with previous reports demonstrated that the ADH gene cluster is telomeric to MLLT2 and KIT, ALB, AFP, PF4, beta TG, GRO1, IL8, ANX3, AREG and DCK are centromeric to MLLT2.

Animals↗

PubMed1995

Comparison of treatment regimens for pediatric lymphoblastic non-Hodgkin's lymphoma: a Childrens Cancer Group study.

PURPOSE: Patients with lymphoblastic non-Hodgkin's lymphoma (LB NHL) were randomized to treatment with either modified LSA2L2 or ADCOMP, which added daunorubicin (DAUN) and asparaginase (L-ASP) to the methotrexate (MTX), cyclophosphamide (CYT), vincristine (VCR), and prednisone (PRED) (COMP) regimen, in a clinical trial to determine the relative effectiveness and toxicity of the two regimens. PATIENTS AND METHODS: Patients with LB NHL were eligible for this randomized study if they were less than 22 years of age at diagnosis and had < or = 25% blasts in the bone marrow. Of 307 patients registered, 281 were fully eligible and assessable. Patients were stratified by extent of disease at diagnosis. RESULTS: The 5-year event-free survival (EFS) rate for patients with localized disease was 84%, and for patients with disseminated disease, 67%. There were four relapses in 28 patients with localized disease. Two hundred six patients had mediastinal primary tumors and despite local radiation, 34 of 63 failures in these patients involved the primary tumor site with or without other involvement. After adjusting for extent of disease at diagnosis, the regimens did not differ significantly with respect to risk for adverse events. The acute toxicity was primarily neutropenia and thrombocytopenia, with greater initial toxicity in patients on the LSA2L2 regimen. Three patients developed acute myelogenous leukemia. CONCLUSION: Long-term EFS in children with LB NHL can be achieved in the majority of patients. Disease progression, which includes recurrence at the primary tumor site, is a major cause of treatment failure in patients with mediastinal presentations. Addition of DAUN and L-ASP to the COMP regimen does not produce a more effective treatment than LSA2L2.

Adolescent↗

PubMed1995

Autologous stem cell transplantation for refractory and relapsed Hodgkin's disease: factors predictive of prolonged survival.

We analyzed patient, disease, and treatment related factors associated with long-term disease-free survival (DFS) in 62 patients with refractory or recurrent Hodgkin's disease treated with high-dose cyclophosphamide (6000 mg/m2), carmustine (BCNU; 300 mg/m2), and etoposide (900 mg/m2) (CBV) followed by autologous stem cell transplantation. There were no deaths resulting from toxicity of the preparative regimen, and all patients survived the peritransplant period. At 28 days post-transplant, the complete response (CR) rate was 76%. Patients who achieved a CR had a 50% estimated 3-year DFS (95% CI, 35-64%). Twenty-three (37%) patients remain in continuous clinical remission 1.3 to 7.7 years (median 3.8 years) after transplantation. In a univariate analysis, factors significantly associated with improved DFS included absence of B symptoms (fever, night sweats and unexplained weight loss) at transplant, response to pre-transplant salvage chemotherapy, less tumor bulk at time of transplant, and fewer prior treatment regimens. Stepwise multivariate analysis showed that the absence of B symptoms at time of transplant was independently and significantly associated with improved DFS after transplantation. CBV with autologous stem cell support can produce durable remissions with acceptable toxicity in a substantial proportion of patients who are asymptomatic at time of transplant. Earlier application of transplantation or development of additional effective antineoplastic modalities will be required to improve the results of transplantation for patients with advanced Hodgkin's disease.

Adolescent↗

PubMed1994

Treatment of moderate and severe acute GVHD after allogeneic bone marrow transplantation.

We analyzed the treatment of acute GVHD following allogeneic, related or unrelated donor bone marrow transplantation (BMT). Of 510 patients transplanted between January 1986 and July 1991, 272 (53.0%) developed acute GVHD. Patients (n = 240) received treatment with either corticosteroids (n = 209), antithymocyte globulin (ATG)/prednisone (n = 26), or an anti-T cell immunotoxin (n = 5). After 28 days, 33% (79/240) had achieved a response to primary therapy; 24% a complete response. Ninety-five patients received 1 or more courses of salvage immunotherapy and 26 (27%) responded. In multivariate analysis, a response to primary therapy was the single most important factor independently predicting a lower risk of subsequent chronic GVHD (P < .0001) and improved long-term survival (P = .01). The GVHD clinical stage score, which we previously described, had significant predictive value for response to therapy and freedom from chronic GVHD. The conventional clinical grade had no such predictive value. In multivariate analysis, transplantation from a mismatched or an unrelated donor was not of independent importance in predicting either acute GVHD treatment response or chronic GVHD. However, these alternative donor transplants led to poorer survival. This analysis identifies patient subsets having GVHD with a low likelihood of response to conventional immunosuppressive treatment and may be used to indicate those needing early application of more intensive therapy. More important, however, the overall low response rates observed suggest that more effective treatment for acute GVHD is still required to improve the results of transplantation therapy.

Acute Disease↗

PubMed1994

Allogeneic bone marrow transplantation for acute lymphoblastic leukaemia: risk factors and clinical outcome.

We report 12 years' experience with histocompatible, related donor marrow transplantation for 123 patients with acute lymphoblastic leukaemia; 104 > or = second remission. Four regimens were studied: cyclophosphamide (Cy)-+total body irradiation (TBI) (n = 35); Cy+fractionated TBI (n = 45); TBI+high-dose cytarabine (n = 15); and hyperfractionated TBI+Cy (n = 28). 45 patients survive (34 +/- 9%; 95% confidence interval) between 1 and 12.7 years (median 7.8 years) following BMT and 29 +/- 8% survive leukaemia-free. Significantly improved disease-free survival was observed in patients with an initial WBC < 50 x 10(9)/l (P = 0.02). Conditioning regimens tested yielded similar outcomes, though TBI/cytarabine led to greater treatment-associated mortality. Leukaemia relapse was the most frequent cause of failure in 56 +/- 11%; median time of relapse 8 months following BMT, none beyond 2.2 years. Relapse was more frequent with higher WBC, shorter initial remission and previous CNS leukaemia. Acute and/or chronic GVHD was associated with a strong trend (P = 0.06) towards less relapse. Allogeneic BMT may be curative for a substantial fraction of patients with ALL, but additional anti-leukaemic measures beyond these conditioning modifications tested will be required to prevent post-transplant leukaemia recurrence.

Adolescent↗

PubMed1994

The MLL (11q23) and AF-4 (4q21) genes disrupted in t(4;11) acute leukemia: molecular and clinical studies.

Recurring chromosomal translocations involving chromosome band 11q23 have been observed in acute lymphocytic leukemia (ALL) and acute myeloid leukemia (AML), especially AML with FAB M4 or M5 phenotype. Though numerous partner chromosomes have been documented, the t(4;11) is the translocation seen most commonly in infant ALL. t(4;11) leukemia, associated with hyperleukocytosis, hepatosplenomegaly, and central nervous system (CNS) disease, has a dismal prognosis. Leukemia with 11q23 rearrangement often shows both lymphoid and myeloid characteristics, leading to speculation that the disrupted gene is involved in lymphoid and myeloid differentiation. The genes at 11q23 and 4q21 have been cloned and sequenced; the data is consistent with a role for these genes in transcriptional regulation. Absence of molecular rearrangement of 11q23 identifies a group of infants with a good prognosis.

Acute Disease↗

PubMed1994

Second infusion of bone marrow for treatment of graft failure after allogeneic bone marrow transplantation.

The availability of hematopoietic growth factors has introduced a new therapeutic modality to the treatment of graft failure after bone marrow transplantation (BMT). However, the clinical value of other therapeutic approaches to graft failure has not been reported in detail. We have studied the outcome of second infusions of BM for treatment of primary and secondary graft failure in 33 patients who received an allogeneic BMT at our institution between 1974 and 1992. Patients had received BM from a related (n = 28) or unrelated (n = 5) donor for hematological malignancy or BM failure. After primary graft failure, 57% (12 of 21) of reinfused patients engrafted and the Kaplan-Meier estimate of survival at 1 year is 24% (CI 6-42%). After secondary graft failure, 33% (4 of 12) of reinfused patients engrafted and survival is 25% (CI 0-50%) at 1 year. Infection, predominantly fungal, was the most frequent cause of death. Acute or chronic graft-versus-host disease (GVHD) developed in 52% of evaluable reinfused patients. We conclude that reinfusion of donor marrow can be an effective intervention in the treatment of primary and secondary graft failure. These data can serve as a comparative historical experience for the assessment of hemopoietic growth factors in the treatment of graft failure.

Acute Disease↗

PubMed1994

Comparison of engraftment in recipients of matched sibling of unrelated donor marrow allografts.

Bone marrow transplantation (BMT) from unrelated donors (URD) is being increasingly used as a treatment modality for patients with hematological malignancy and graft failure. We hypothesized that use of unrelated donors with increased degrees of histoincompatibility, as determined by standard serological techniques, would be associated with increased difficulty in achieving engraftment and more frequent graft failure. Engraftment was analyzed in 108 patients with hematologic disease who underwent BMT from a fully serologically HLA-matched unrelated donor (n = 40) or a partially serologically HLA-matched unrelated donor (n = 68). These patients were compared with 236 patients who received BMT from matched sibling donors (MSD group) over the same time period. Primary graft failure occurred in 5% of the MSD group, 6% of the serologically matched URD group and 15% of the partially serologically matched URD group (p = 0.06). Univariate and multivariate analysis of factors relating to primary graft failure showed the only significant variable to be full or partial serological HLA-matching in the URD group. Secondary graft failure occurred in 0.7% of the MSD group, 15% of the serologically matched URD group and 25% of the partially serologically matched URD group (p < 0.0001). Univariate and multivariate analysis of secondary graft failure showed the only significant variable to be a related or unrelated donor. We conclude that primary graft failure is a significantly more frequent event in recipients of bone marrow from partially serologically matched URD than in recipients of MSD or fully serologically matched URD marrow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Predictive factors for chronic graft-versus-host disease after histocompatible sibling donor bone marrow transplantation.

We analyzed factors associated with the development of chronic graft-versus-host disease (GVHD) in 469 consecutive patients receiving matched sibling allogeneic bone marrow transplantation (BMT). Overall, 41 +/- 6% (95% confidence interval) developed chronic GVHD between 2 and 50 months after BMT. Multivariate analysis showed that previous acute GVHD was the dominant independent risk factor predisposing to chronic GVHD (Relative Risk 4.82, p < 0.0001). In addition, recipient age of > or = 18 years and male recipient with female donor were also independent predictive factors for development of chronic GVHD. When acute GVHD and recipient age were considered, groups with distinctive risks of chronic GVHD were identified. Patients under 18 without previous grade II-IV acute GVHD had only a 10 +/- 5% risk of chronic GVHD. Patients over 18 with no prior grade II-IV acute GVHD had a 31 +/- 12% risk while patients with advanced acute GVHD, regardless of age, had the highest risk and 70 +/- 8% developed chronic GVHD. It is important to consider these factors when designing and assessing clinical trials of chronic GVHD prophylaxis and treatment.

Adolescent↗

PubMed1994

Lymphoproliferative disorders and other tumors complicating immunodeficiencies.

Lymphoproliferative disorders and selected carcinomas which occur as complications of primary or secondary immunodeficiencies are frequently fatal. The incidence rates of these cancers vary from 1% to as high as 25% among specific groups of persons with primary (genetically-determined) immunodeficiencies as well as acquired immunodeficiencies, including immunosuppressed organ transplant recipients and individuals infected with HIV. Lymphoproliferative disorders including Epstein Barr virus (EBV) associated B cell lymphoproliferative disease (BLPD) and Hodgkin's disease represent the predominant category of tumors in both primary and acquired immunodeficiencies. EBV is an important cofactor common to many, but not all, B cell "lymphomas." Immunodeficient individuals who are at risk for developing EBV BLPD may demonstrate both inadequate immune responses to the virus as well as generalized immunoregulatory dysfunction reflected as imbalances in cytokine production favoring the proliferation of transformed B lymphocytes. Historically, the success of treatment of lymphoproliferative disorders in immunodeficiencies with conventional multi agent chemotherapies and/or radiation has been limited by unfavorable tumor response rates and high morbidity and mortality related to intercurrent opportunistic infections. With improvements in supportive care and the use of recombinant biologic response modifiers such as alpha interferon and/or other immunotherapies to treat EBV BLPD, survival of immunodeficient hosts following tumor diagnosis may improve. In addition to lymphoproliferative disorders, patients with congenital immunodeficiencies associated with IgA deficiency (including ataxia telangiectasia and Common Variable Immunodeficiency) are at increased risk for gastrointestinal carcinomas. Early detection and surgical excision of such tumors can result in prolonged survival in such patients.

Humans↗

PubMed1993

Acute mixed-lineage leukemia t(4;11)(q21;q23) generates an MLL-AF4 fusion product.

A chromosomal translocation, t(4;11)-(q21;q23), is associated with an aggressive mixed-lineage leukemia. A yeast artificial chromosome was used to clone the chromosomal breakpoint of this translocation in the RS4;11 cell line. The breakpoint sequences revealed an inverted repeat bordered by a consensus site for topoisomerase II binding and cleavage as well as chi-like elements. The der(11) chromosome encodes a fusion RNA and predicted chimeric protein between the 11q23 gene MLL and a 4q21 gene designated AF4. The sequence of the complete open reading frame for this fusion transcript reveals the MLL protein to have homology with DNA methyltransferase, the Drosophila trithorax gene product, and the "AT-hook" motif of high-mobility-group proteins. An alternative splice that deletes the AT-hook region of MLL was identified. AF4 is a serine- and proline-rich putative transcription factor with a glutamine-rich carboxyl terminus. The composition of the complete MLL-AF4 fusion product argues that it may act through either a gain-of-function or a dominant negative mechanism in leukemogenesis.

Amino Acid Sequence↗

PubMed1993

Characterization of CD7+CD19+ lymphoid cells after Epstein-Barr virus transformation.

The early stages of lymphoid differentiation preceding T and B lineage commitment remain poorly defined. We hypothesized that early lymphoid precursor cells are possibly common progenitors and would express a very early T cell-associated Ag (CD7) and a very early B cell-associated Ag (CD19) simultaneously. We therefore transformed CD7+CD19+ fetal bone marrow lymphoid cells using EBV. Extensive characterization of the resulting cell lines indicated that two cell lines corresponded to pre-B and early B cells co-expressing CD7. The third cell line resembled a thymocyte, which co-expressed a number of B cell-associated Ag including CD19 and the stem cell Ag CD34. The two predominantly B lineage cell lines have their Ig genes rearranged, whereas the predominantly T lineage cell line has TCR and Ig H chain genes rearranged. Cross-lineage Ag were not expressed any more after culturing for a prolonged period of time, i.e., B lineage cells became CD7 negative and the thymocyte lineage became negative for the B cell-associated Ag. However, in all three cell lines TCR and/or Ig gene rearrangements remained unchanged. These observations support the existence of a common lymphoid precursor co-expressing CD7 and CD19 that gives rise to either T or B cells.

Antigens, CD↗