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Biomedical subjects

B Varet

Publications and source records attributed to B Varet.

At least 55 records · Page 3Linked to original sources
PubMed1997

Peptides derived from the whole sequence of BCR-ABL bind to several class I molecules allowing specific induction of human cytotoxic T lymphocytes.

Chronic myeloid leukemia (CML) is characterized cytogenetically by a t(9;22) translocation which generates a hybrid bcr-abl gene, encoding a p210(bcr-abl) fusion protein. The induction in vitro of leukemia-specific T cells reactive with p210(bcr-abl) is a strategy developed for an immunological therapeutic approach in CML. Peptides from the junction region of this chimeric protein have been considered as potential targets for a cytotoxic response against leukemic cells. However, only a few peptides encompassing the two p210(bcr-abl) breakpoints have been shown to bind to the most common HLA class I molecules, which limits the number of patients who could benefit from this approach. We assume that the presence of chimeric BCR-ABL protein in leukemic cells may affect processing and delivery of peptides, possibly giving rise to new epitopes at the cell surface. We selected 162 peptides from the whole sequence of this protein, including 14 peptides of the b2a2 and b3a2 junctions, which had an anchor motif for a common HLA class I molecule. We tested their ability to bind to eight HLA class I molecules (HLA-A1, -A2, -A3, -A11, -B7, -B8, -B27, -B44). We identified 48 peptides from outside the junction region, with intermediate or strong binding capacities to these HLA class I molecules contrasting with only six junction peptides with a moderate binding capacity to HLA-A3/A11, -B8, or -B44 molecules. Moreover, cytotoxic T lymphocyte lines specific for various peptides outside the junction were generated from peripheral blood mononuclear cells of HLA-A2 or -B7 healthy donors and from one CML patient. These results contribute to evaluation of immunity to the BCR-ABL chimeric protein. Further studies are required to investigate whether such epitopes are correctly processed and presented by leukemic cells.

Amino Acid Sequence↗
PubMed1997

Early allogeneic transplantation favorably influences the outcome of adult patients suffering from acute myeloid leukemia. Société Française de Greffe de Moelle (SFGM).

Allogeneic BMT for patients with acute myeloid leukemia (AML) is presently a reference therapy. The indications for this therapy mainly rely upon prognostic factors, and their importance is constantly reassessed. To examine the impact of time from diagnosis to transplant on survival and leukemia-free survival (LFS), we analyzed 109 patients from the database of the SFGM comprising patients who had all received an HLA-identical allogeneic BMT for a diagnosis of AML in first complete remission (CR1) between January 1987 and December 1992. All patients were conditioned with cyclophosphamide (CY) and total body irradiation (TBI) (CYTBI), and methotrexate (MTX) + cyclosporin A (CsA) were used as graft-versus-host disease (GVHD) prophylaxis. Patient characteristics were: age = 33 +/- 9, M/F = 64/45, white blood cell count (WBC) at diagnosis = 27 +/- 42 x 10(9)/l, FAB distribution: M1 and M2 = 55; M3 = 15, M4 and M5 = 33, M0, M6 and M7 = 6. Karyotyping was carried out for 64 patients: 32 had a normal karyotype, 16 had good prognosis abnormalities (t(8;21), t(15;17), inv 16) and 16 patients had other abnormalities. Eleven patients needed two courses of induction to achieve CR. Time between diagnosis and BMT was 120 (64-287) days. Forty-nine patients developed grade > or = 2 acute GVHD (actuarial probability = 46%). With a median follow-up of 50 months (27-100), the 5-year probabilities for transplant-related mortality (TRM), relapse, overall survival and LFS are respectively 25%, 26%, 59% and 55%. A multivariate analysis showed that survival is adversely influenced by three independent factors: time to transplant (> 120 days vs < or = 120 days), acute GVHD (grade 2-4 vs grade 0-1) and age (> 33 vs < or = 33). LFS is only influenced by the first two of these factors. The favorable impact of a shorter time from diagnosis to transplant should lead to performing the transplant as early as possible. Practically speaking, this means that when such therapy is chosen for a patient with CR1 AML, the search for an allogeneic donor should begin immediately and transplant be performed as soon as possible.

Acute Disease↗
PubMed1997

Alternative origin of p13MTCP1-encoding transcripts in mature T-cell proliferations with t(X;14) translocations.

The MTCP1 gene is involved in the t(X;14)(q28;q11) translocation associated with T-cell prolymphocytic leukemia and related conditions. This gene is unusual in that it codes for two distinct proteins: a small mitochondrial protein, p8MTCP1, and a putative oncogenic protein, p13MTCP1. Scarcity of material from t(X;14)-associated proliferations and very low levels of mRNA expression have so far prevented a thorough description of p13MTCP1-encoding transcripts. Here, we characterize two additional t(X;14) bearing leukemias allowing this analysis. In one case, with a breakpoint located 5' to the MTCP1 gene, the level of transcription of previously described p13MTCP1-encoding transcripts is enhanced. In the second case, with a breakpoint within the MTCP1 intron I, an alternative transcription initiation site is demonstrated in the tumor cells at 229 bp upstream to exon II. The identification of this internal promoter, together with the similarity between TCL1 and MTCP1 genomic structures, allow us to propose a model in which the duplication of an ancestral gene was followed by the insertion of one copy within the intron of a p8-encoding gene, accounting for the unusual feature of the MTCP1 gene.

Aged↗
PubMed1997

Simultaneous SIL-TAL1 RT-PCR detection of all tal(d) deletions and identification of novel tal(d) variants.

Site-specific deletions of the 5' part of the TAL1 gene (tal(d)) are among the most frequent non-random genetic abnormalities in T-cell acute lymphoblastic leukaemia (T-ALL). They are usually detected by PCR from DNA with several primer pairs or by Southern blot analysis. Since tal(d) lead to expression of a SIL-TAL1 fusion transcript, irrespective of the genomic breakpoint, we have used a single monoplex RT-PCR reaction to screen 55 T-ALL patients at diagnosis. SIL-TAL1 transcripts were demonstrated in 12 (22%) cases, including 7/27 (26%) children <15 years of age, 2/8 (25%) adolescents and 2/17 (12%) adults aged >20 years. SIL-TAL1 RT-PCR was preferrable to tal(d) DNA PCR since it allowed the simultaneous detection of tal(d), tal(d2) and two previously undescribed tal(d) variants. SIL-TAL1 RT-PCR screening should therefore increase the detection rate of tal(d) by approximately 15-20%, with an at least comparable sensitivity to tal(d) genomic PCR, and represents a more practical and economic alternative to multiple DNA PCRs or Southern blotting when incorporated into molecular screening for multiple transcripts at diagnosis.

Adolescent↗
PubMed1997

Molecular analysis of clonality in Kaposi's sarcoma.

BACKGROUND: Kaposi's sarcoma is considered to be an angioproliferative disease associated with a novel herpesvirus (KSHV/HHV8), but the precise pathophysiology of the lesion remains unclear. The study of clonality in Kaposi's sarcoma using X linked DNA polymorphism has been difficult so far, because of a very strong prevalence of the disease in males. AIMS: To study the clonality of Kaposi's sarcoma lesions. METHODS: An assay based on a methyl sensitive restriction digest followed by polymerase chain reaction (PCR) amplification of the highly polymorphic human androgen receptor (HUMARA) gene was used. Tissues from Kaposi's sarcoma lesions and control tissues from the same patients were obtained from seven females, four with classic Kaposi's sarcoma and three with AIDS associated Kaposi's sarcoma. A cutaneous angiosarcoma was also analysed, for comparative purposes, and showed evidence of clonality after HpaII digestion. RESULTS: All patients were heterozygous for the HUMARA polymorphism and informative for analysis. In all patients, including four with a nodular form of Kaposi's sarcoma and more than 70% spindle cells in the lesion, a polyclonal pattern of inactivation could be demonstrated. CONCLUSIONS: The Kaposi's sarcoma lesion is first of all a polyclonal cell proliferation.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Molecular detection of t(8;21)/AML1-ETO in AML M1/M2: correlation with cytogenetics, morphology and immunophenotype.

The t(8;21) identifies a subgroup of acute myeloid leukaemia (AML) with a relatively good prognosis which may merit different treatment. It is associated predominantly, but not exclusively, with AML M2, and corresponds to rearrangements involving the AML1 and ETO genes. AML1-ETO positive, t(8;21) negative cases are well recognized but their incidence is unknown. In order to determine optimal prospective AML1-ETO RT-PCR screening strategies, we analysed 64 unselected AML M1 and M2 cases and correlated the results with other biological parameters. Molecular screening increased the overall detection rate from 8% to 14%. AML1-ETO was found in 3% (1/32) of AML M1 and 25% (8/32) of M2, including three patients without a classic (8;21) but with chromosome 8 abnormalities. It was more common in younger patients. Correlation with morphology enabled development of a scoring system which detected all nine AML1-ETO-positive cases with a false positive rate of 7% (4/55). Although certain AML1-ETO-positive cases demonstrated characteristic immunological features (CD19 and CD34 expression, CD33 negativity), each of these markers was insufficiently specific to permit prediction in an individual case. We conclude that initial routine prospective molecular screening for AML1-ETO in all AMLs, combined with standardized morphological and immunological analysis, is desirable in order to produce improved prognostic stratification and to determine whether screening can ultimately be restricted to appropriate subgroups.

Adolescent↗
PubMed1996

Sustained complete cytologic and molecular remission induced by donor leucocyte infusions alone in an acute myeloblastic leukaemia in relapse after bone marrow transplantation.

Therapeutic options for treatment of recurrence of leukaemia after allogeneic bone marrow transplantation (BMT) are limited. A beneficial effect of donor lymphocyte infusions (DLI) has not previously been described in acute myeloid leukaemia (AML) relapse. We report a case of AML with t(8;21), relapsing 3 months after BMT, who received DLI without adjuvant chemotherapy or growth factors. The patient developed acute GVHD and achieved a rapid complete remission of his AML by both cytologic and molecular criteria of at least 14 months duration, thereby showing that DLI for AML in relapse after BMT is an alternative therapeutic option.

Adult↗
PubMed1996

Aggressive acute CD3+, CD56- T cell large granular lymphocyte leukemia with two stages of maturation arrest.

In the majority of clonal expansions of CD3+ large granular lymphocytes (LGL), referred to as T-LGL leukemia, patients have a chronic disease, often manifested by severe neutropenia, rheumatoid arthritis, and mild to moderate splenomegaly. The characteristic leukemic phenotype is CD3+, CD8+, CD16+, CD57+ and CD56-. Here we report an unusual case of T-LGL (CD3cyt+, CD3surface-, CD16+, CD56-) with clinicopathological features (acute presentation, large tumor mass, and systemic illness with highLGL counts at diagnosis) similar to those described for patients with CD3-natural killer (NK)-LGL leukemia. Two distinct stages of maturation arrest were observed: in the lymph node abnormal cells were CD4+, CD8+ whereas the majority of circulating leukemic cells expressed only CD8. TCR gamma (TCR gamma) gene configuration demonstrated that these originated from the same T cell clone, suggesting a maturation process between the two populations, or preferential passage of CD8 single positive cells into the blood.

Adolescent↗
PubMed1995

Detection of clonal CD34+19+ progenitors in bone marrow of BCL2-IgH-positive follicular lymphoma patients.

The frequent occurrence of BCL2-IgH rearrangements in follicular lymphoma (FL) makes detection of low numbers of tumor cells possible by polymerase chain reaction (PCR). The presence of BCL2-IgH in the bone marrow (BM) and peripheral blood of many FL patients at the time of autografting has led to the suggestion that selection of the CD34-enriched fraction may lead to reinfusion of lower numbers of tumor cells. To address this issue, we PCR-amplified BCL2-IgH from fluorescence-activated cell sorting (FACS)-purified BM CD34+ and CD34- fractions in seven FL patients showing a PCR-detectable translocation in the major breakpoint region of BCL2, five of which showed morphological BM involvement. The total CD34+ fraction showed diminished but residual positivity in the first two cases tested. Therefore, BM cells from the remaining five patients were sorted for the CD34+19- immature population, the CD34+19+ B-cell precursors, and the CD34-19+ mature B-cell fraction. The CD34+19- subpopulation was negative in four of five, despite evident BM infiltration in three cases. In contrast, the CD34+19+ fraction was positive in all three cases tested. These cells represented 0% to 50% (mean, 18%) of the total CD34+ population, suggesting that, if reinfusion of BCL2-IgH-positive cells plays a role in postautograft relapse in FL, therapeutic CD34 selection procedures should include additional purging of the CD34+19+ B-cell precursors or, at least, assessment of the proportion of CD19+ cells in the CD34+ fraction and its correlation with clinical outcome postreinfusion.

Adult↗
PubMed1995

Highly purified primitive hematopoietic stem cells are PML-RARA negative and generate nonclonal progenitors in acute promyelocytic leukemia.

The hierarchical level of stem cell involvement in acute promyelocytic leukemia (APL) characterized by the pathognomonic PML-RARA fusion gene is unknown. To determine if the cells of the primitive hematopoietic stem cell compartment are involved in the leukemic process, we have used molecular and cell sorting techniques in peripheral blood and bone marrow (BM) cells at diagnosis from three patients with APL and t(15; 17). In two of them, clonality analysis was also possible using the BstXI polymorphic site of the PGK gene. The PML-RARA fusion gene was readily identified by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of BM cells obtained at diagnosis in all three patients. These same samples were then used to sort CD34+ cells and their CD38+ and CD38- subsets by fluorescence-activated cell sorting. In both female patients, CD34+/CD38+ and CD34+/CD38- cell fractions were polyclonal using PCR, whereas a monoclonal pattern was identified at the BM sample obtained at diagnosis either by Southern blotting or by PCR. Because of the high sensitivity of the PCR analysis, the polyclonal pattern of these cell populations could mask the presence of a minor clone. To detect this clone, we preformed RT-PCR analysis for t(15; 17). In one female patient, the abnormal PML-RAR fusion gene was found only in the more mature CD34+/CD38+ cell fraction using a nested PCR approach, whereas the polyclonal CD34+/CD38- fraction was PML-RARA negative. These findings were confirmed in a third patient with APL in whom the PML-RARA transcripts were absent in the CD34+/CD38- cell fraction. To study the clonality at the level of clonogenic progenitors, we used in one patient PGK analysis by PCR of individual burst-forming units-erythroid and colony-forming units-granulocyte-macrophage obtained from the CD34+/CD38- and CD34+/CD38+ cell populations at diagnosis and from the BM sample obtained during remission. The two highly purified cell populations gave rise to morphologically normal colonies clonal for both the BstXI site containing (A) and the BstXI site lacking (B) PGK allelles, indicating their polyclonal content, a pattern that was also found in clonogenic progenitors obtained at remission. These findings strongly suggest that the primitive hematopoietic stem cells as defined by the CD34+/CD38- antigens are not involved by the neoplastic process in APL. These results may have important implications for autografting strategies of retinoic acid/chemotherapy-resistant or relapsed patients.

ADP-ribosyl Cyclase↗