ALBERT

Beschreibung: p53 overexpression has been found to be a fairly common feature in high grade lymphomas in the majority of tumoral cells. The results vary from series to series, from 25% to 33% of cases. To assess whether immunohistochemical positivity for p53 correlated with the presence of structural gene abnormalities, DNA from 16 non-Hodgkin's lymphomas with high and low p53 values was amplified and sequenced to determine the existence of point mutations in the highly conserved regions of the p53 gene. In the group of 8 cases containing high levels of protein, 3 cases showed missense point mutations at the codons mapping between exons 5 through 8. Of the 8 cases of tumors containing undetectable or low levels of p53 protein, 1 case presented a nonsense point mutation giving a stop codon. No missense mutations were detected in this group. The finding of p53 mutations in 4 of 16 cases confirms the presence of p53 gene mutations in high grade lymphomas distributed over different histologic groups. These include Burkitt's lymphoma, together with centroblastic, immunoblastic, and large cell lymphoma of mucosa origin. Nevertheless, the absence of mutations in 5 of the 8 cases that overexpressed p53 suggests that the nuclear or cytoplasmic stabilization of p53 protein could also depend on other factors. The absence of detectable levels of p53 protein cannot discount the existence of p53 mutations, as is shown by a case of Burkitt's lymphoma in which a nonsense mutation was detected. The impact of this range of p53 alterations on clinical course and treatment response of the patients deserves to be explored, in an attempt to differentiate the specific consequences of each one.

Beschreibung: The transcription factor PLZF is expressed in hematopoietic development and rearranged in t(11;17) acute promyelocytic leukemia (APL). PLZF expression is high in the quiescent progenitor CD34+ cell, and declines during differentiation along myeloid and erythroid lineages. PLZF encodes a BTB-Zinc finger transcriptional repressor that inhibits the cell cycle through inhibition of targets genes such as cyclin A and c-myc through the recruitment of histone deacetylase complexes. However, PLZF itself is regulated by acetylation. In a separate study we demonstrate that acetylation of PLZF by p300/CBP enhances the transcriptional repression activity of PLZF. Through a yeast two-hybrid study we found that PLZF associates with the protein deacetylase SIRT1. SIRT1 is a member of the sirtuin family of class III histone deacetylases. In model organisms such as yeast, worms and flies, sirtuins play a common role in lifespan extension. The interaction between PLZF and SIRT1 was confirmed by co-precipitation of endogenous proteins and localized to the zinc fingers of PLZF, the region targeted for acetylation by p300/CBP. Acetylation of PLZF mediated by p300/CBP was reversed by SIRT1. Furthermore while acetylation of PLZF enhances its ability to repress transcription, co-expression of SIRT1 decreased PLZF transcriptional repression activity, consistent with loss of acetylation. Conversely, inhibition of SIRT1 activity with nicotinamide enhanced both PLZF acetylation and transcriptional repression of PLZF on its endogenous target gene c-myc. Further, increasing PLZF acetylation by inhibition of SIRT1 was associated with decreased PLZF stability. Acetyl-PLZF levels were stabilized by inhibition of the proteosomal degradation machinery, together implying that PLZF acetylation and activation results in increased protein turnover. These data point to the increasing complexity of the role of acetylation in transcriptional regulation and stand in contrast with data for the related Bcl6 repressor where acetylation of the protein inhibits repression. These data also indicate a novel function for sirtuins in regulation of transcriptional repression.

Beschreibung: Multiple myeloma (MM) remains as an incurable disease although new therapies can achieve a high rate of complete remissions (CR). Unfortunately, most patients ultimately relapse due to the persistence of minimal residual disease (MRD), and only a minority could be cured. Detection and quantification of these cells is an important tool for monitoring these patients and predicting a potential relapse. Here we analyze by RQ-PCR the MRD in MM patients achieving CR in order to classify them into different risk categories. MATERIAL AND METHODS: 38 MM patients uniformly treated according to the GEM-2000 (Spanish group for Myeloma) protocol, and that have achieved CR following PBSCT were included in the study. 22 were IgG, 9 IgA, 6 B-J and 1 non-secretory (κ/λ 21/16). 27 were male & 11 female with a median age of 58 (range 48–65). Bone marrow samples obtained at diagnosis and 3 months after transplant were analyzed. Complete (VDJH) and incomplete (DJH) Ig rearrangements were amplified with the Biomed-2 strategy (Leukemia2003;17:2257). PCR clonal products were sequenced on an ABI Prism 377 Sequence detector. VH, DH and JH segments were identified by comparing with germinal sequences on V-Base and BLAST databases. An ASO primer at the N-region was designed for each patient with the OLIGO 6.0 software. RQ-PCR was then performed on an ABI Prism 7700 using the ASO specific forward primer, a JH reverse intronic primer (JH1–6) and a TaqMan probe (JH1,2,4,5, JH3 or JH6) to amplify the patient specific rearrangement. Sample quality and quantity was controlled evaluating the standard curve of the albumin gene amplification. MRD was calculated according to ΔCT method. RESULTS: In 14 out of the cases included in the study, MRD investigation was not possible because the N-region was not longer enough to design the ASO primer (n=3), poor quality in the diagnostic sample to obtain the standard curve (n=8) or low plasma cell infiltration at diagnosis to obtain correct dilutions (n=3). The remaining 24 patients were classified into different risk groups according to the MRD level obtained 3 months after transplantation with a cut-off point of 0.01% tumor cells. Thus, progression free survival (PFS) was longer in those patients with MRD〈 10−4 (p=0.03, figure 1A). By contrast, upon comparing the impact on PFS of immofixation (IFX) in these 24 patients that were in CR (defined by conventional electrophoresis criteria), it was observed that patients with IFX (−) didn’t showed a different outcome from those IFX (+) (figure 1B). CONCLUSION: In summary, although RQ-PCR is a labor and time-consuming technique, it is an useful tool for monitoring MRD in MM. The level of 10−4 can contribute to classify patients into 2 groups (high and low MRD) with different risk of relapse that can be used to design specific therapies.

Beschreibung: p53 overexpression has been found to be a fairly common feature in high grade lymphomas in the majority of tumoral cells. The results vary from series to series, from 25% to 33% of cases. To assess whether immunohistochemical positivity for p53 correlated with the presence of structural gene abnormalities, DNA from 16 non-Hodgkin's lymphomas with high and low p53 values was amplified and sequenced to determine the existence of point mutations in the highly conserved regions of the p53 gene. In the group of 8 cases containing high levels of protein, 3 cases showed missense point mutations at the codons mapping between exons 5 through 8. Of the 8 cases of tumors containing undetectable or low levels of p53 protein, 1 case presented a nonsense point mutation giving a stop codon. No missense mutations were detected in this group. The finding of p53 mutations in 4 of 16 cases confirms the presence of p53 gene mutations in high grade lymphomas distributed over different histologic groups. These include Burkitt's lymphoma, together with centroblastic, immunoblastic, and large cell lymphoma of mucosa origin. Nevertheless, the absence of mutations in 5 of the 8 cases that overexpressed p53 suggests that the nuclear or cytoplasmic stabilization of p53 protein could also depend on other factors. The absence of detectable levels of p53 protein cannot discount the existence of p53 mutations, as is shown by a case of Burkitt's lymphoma in which a nonsense mutation was detected. The impact of this range of p53 alterations on clinical course and treatment response of the patients deserves to be explored, in an attempt to differentiate the specific consequences of each one.

Beschreibung: Background. In the World Health Organization classification system (WHO), Splenic Marginal Zone B-cell Lymphoma (SMZBCL) is described as an indolent B-cell lymphoma, which generally presents as splenomegaly with involvement of the bone marrow and peripheral blood. The immunophenotype is usually IgM+, IgD+/−, cytoplasmic-Ig−/+, pan B antigens+, CD5−, CD10−, CD23−, CD43−/+ and cyclin D1−. A minority of cases (〈 20%) express CD5 antigen. The most frequent cytogenetic aberrations are deletions at 7q22–q32, gains of chromosome 3/3q and involvement of chromosomes 1 and 8. The objective of this study is the genetic characterization of SMZBCL by conventional cytogenetics and FISH. Patients and methods. We present 92 patients with SMZBCL from a multicenter study after being diagnosed morphologically and immunologically. Conventional cytogenetic studies were carried out on lymphoid cells from 72 hour-peripheral blood and/or spleen cultures stimulated with TPA. FISH was performed with centromeric probes from chromosome 3 and 12 and locus specific probes from P53 gene and 7q31 loci. Cross-species color banding FISH (RxFISH) probe was applied in 11 patients and SKY in 4 patients to redefine/confirm G-banding karyotype. Results. A clonal chromosome abnormality was found in 62/92 patients (67%) being identified in 37 (60%) as a complex karyotype. The most frequent recurrent abnormalities were deletions of 7q (30 cases) and gains of chromosome 3 (20 cases). 6/20 cases with gains #3, were gains of 3q arm, in three of them resulting from an unbalanced translocation. Thirteen cases showed rearrangements of 3q without gain of material. The chromosomes most frequently involved were: 7q, 3q, 14q, 8q and 1q (in more than 10 cases). Four cases presented gain of chromosome 3/3q and 7q deletion in the same karyotype. Four novel cytogenetic aberrations involving 14q32 were found in this series: t(6;14)(p12;q32) in two cases, t(14;19)(q32;q13) in two cases and t(10;14)(q24;q32), t(1;14)(q21;q32) and t(9;14)(pter-p22::14q32-14q11::9q22) in one case respectively. Conclusions. -In our series, the most frequent cytogenetic aberration in SMZBCL is a deletion at 7q (48%) and could be considered as a cytogenetic marker of these entity. -Gains of chromosome 3 or partial gains affecting only 3q arm are frequently observed in SMZBCL (32%) being chromosome 3 commonly rearranged. -RxFISH ans SKY techniques help us to define new aberrations not detected by conventional cytogenetics. -We describe translocations involving 14q32 that could help us to identify novel oncogenes related to SMZBCL.

Beschreibung: Stage of the disease at transplant is critical for outcome after unrelated donor umbilical cord blood transplantation (UD-UCBT). The results of UD-UCBT in adults transplanted early in the course of their disease are unclear. Thus, UD-UCBT remains as the last resort for most patients. The major aim of this report was to study the outcome of a series of adult patients with hematologic malignancies undergoing UD-UCBT early in the course of their disease in a single institution. From May 1997 to May 2004, 40 patients in early disease stages underwent UD-UCBT. All patients received thiotepa, busulfan (orally in 29, intravenously in 11), cyclophosphamide, and antithymocyte globulin (Lymphoglobulin in 24 and Thymoglobulin in 16) as conditioning, cyclosporine and prednisone for graft-versus-host disease (GVHD) prophylaxis, and filgrastim to fasten engraftment. Diagnosis were chronic myeloid leukemia in chronic phase in 14 cases, high-risk acute lymphoblastic leukemia in 14 (12 in CR1, 1 in CR2, and 1 in CR3), high-risk acute myeloblastic leukemia in 8 (7 in CR1 and 1 in CR2), and high-risk myelodysplastic syndrome in 4 (3 untreated and 1 in CR1). Median age was 27 years (range, 16–46). The degree of HLA match (HLA-A and -B by serology and -DRB1 by high-resolution DNA typing) was 6/6 in 2 (5%), 5/6 in 18 (45%), and 4/6 in 20 cases (50%). The median number of nucleated and CD34+ cells infused was 1.8 x 107/kg (range, 0.9–4) and 0.8 x 105/kg (range, 0.1–5.7) respectively. Median time to PMN above 0.5 x 109/L and to platelets above 20 x 109/L was 22 days (range, 13–44) and 69 days (range, 32–188), and the cumulative incidence of myeloid and platelet engraftment was 90% (95% CI, 81–99%) and 70% (95% CI, 57–86%), respectively. Time to myeloid engraftment showed a direct relationship with the number of CFU-GM and CD34 cells cryopreserved (P = .02 and .01 respectively) and infused (P = .0001 and .0004 respectively). Platelet engraftment was faster in patients receiving grafts with a higher number of CFU-GM (P = .005) and CD34+ cells (P = .04), in those receiving Thymoglobulin (P = .02) and in those not developing acute GVHD above grade II (P = .04). Eight patients (20%) developed acute GVHD above grade II, and 9 of 25 patients at risk had extensive chronic GVHD. Patients receiving Thymoglobulin had a lower risk of acute GVHD (P = .0003). With a median follow-up of 33 months (range, 3–87), the probability of disease-free survival (DFS) at 3 years was 48% (95% CI, 30–66%) and was related directly to age (P = .004) and inversely to the development of acute GVHD above grade II (P = .004). The probability of DFS at 3 years was 66 % for patients younger than 31 years and 54% for those not developing acute GVHD above grade II. Cell dose, degree of HLA mismatch, and diagnosis did not clearly influence DFS. These results compare to those obtained after matched unrelated donor bone marrow transplantation, and suggest that UD-UCBT is a reasonable first-line option for adults with hematologic malignancies requiring transplantation and lacking a HLA-matched sibling donor.

Beschreibung: Genomic aberrations in a series of paired biopsy samples from patients who presented initially with follicle center lymphoma (FCL) and subsequently transformed to diffuse large B-cell lymphoma (DLBCL) were measured by array comparative genomic hybridization (CGH). The consequences of these aberrations on gene expression were determined by comparison with expression analysis on these specimens using cDNA microarrays. A heterogeneous pattern of acquired genomic abnormalities was observed upon transformation, some of which were recurrent in small subsets of patients. Some of the genomic aberration acquired upon transformation, such as gain/amplification of 1q21-q24, 2p16 (REL/BCL11A gene loci), 3q27-q29 (including theBCL6 locus), 7q11.2-q22.1, 12pter-q12, 18q21 (including theBCL2 locus) and Xq, and deletion of 6q22-q24, 13q14-q21 and 17p13 (P53 locus) have been previously implicated in the FCL/DLBCL pathogenesis. In addition, novel genomic imbalances not previously reported in association with FCL transformation, such as overrepresentation of 4p12-pter, 5p12-p15, 6p12.3-p21, 9p23, 9q13-q31, 16q, 17q21, and loss of 1p36.3, 4q21-q23, 5q21-q23, 9q31-qter, 11q24-q25, and 15q23, were identified. We observed a differential expression profile of many genes within regions of gain and deletion upon transformation, including novel target genes associated with FCL transformation. However, other genes did not show deregulated expression despite their location within these areas. In summary, the combination of array CGH and expression analysis provides a more comprehensive picture of the transformation of FCL to DLBCL. This process is associated with the acquisition of a variable spectrum of genomic imbalances affecting recurrent chromosomal areas that harbor overexpressed or underexpressed genes targeted upon transformation.

Beschreibung: Homing of blood-borne lymphocytes to peripheral lymph nodes (PLNs) is a multistep process dependent on the sequential engagement of L-selectin, which mediates lymphocyte rolling along the luminal surface of high endothelial venules (HEVs), followed by activation of lymphocyte integrins and transmigration through HEVs. Within lymphoid tissue, B and T lymphocytes then migrate toward specific microenvironments such as B-cell follicles and the paracortex, respectively. The lymphocyte-expressed chemokine receptor CCR7 is playing an important role during this process, as its HEV-presented ligands CCL19 and CCL21 can trigger rapid integrin activation under flow in addition to inducing a chemotactic response, which may participate in transmigration and/or interstitial migration. Here, we report that Tyrphostin (Tyr) AG490, a pharmacological inhibitor of Janus family tyrosine kinases (Jaks), blocked the chemotactic response of primary mouse lymphocytes to CCL19 and CCL21 in a dose-dependent manner. Furthermore, Tyr AG490 inhibited rapid CCL21-mediated up-regulation of α4 and β2 integrin adhesiveness in static adhesion assays and under physiological flow, whereas adhesion induced by phorbol myristate acetate remained unaltered. Using intravital microscopy of subiliac PLNs in mice, we found that adoptively transferred Tyr AG490–treated lymphocytes adhered significantly less in HEVs compared with control cells, although L-selectin–mediated rolling was similar in both samples. Finally, we observed rapid Jak2 phosphorylation in CCL21-stimulated primary mouse lymphocytes. Thus, our study suggests a role for Jak tyrosine kinases during CCR7-mediated lymphocyte recirculation.

Beschreibung: p27 is a cyclin-dependent kinase inhibitor that plays a critical role in regulating G1/S progression, and whose activity is, in part, regulated through interactions with D-type cyclins. Mantle cell lymphoma (MCL) is characterized by the t(11;14) translocation resulting in deregulated cyclin D1. We previously showed that p27 expression in MCL, as assessed by immunohistochemistry (IHC), does not show the usual inverse relationship to proliferate seen in most other lymphomas that do not overexpress cyclin D1. This suggested that the normal expression or control of p27 activity on cell growth might be altered through potential interactions with cyclin D1. Using Western blot and coimmunoprecipitation studies, we assessed the interrelationship between cyclin D1 and p27 in several cyclin D1+ cell lines and primary MCL cases. Similar to our previous results by IHC, typical MCLs showed lower expression of p27 when compared to the more highly proliferative blastic cases or cell lines (mean arbitrary units: 58 versus 236 versus 120). Cyclin D1 was expressed at variable levels in both typical and blastic MCLs. p27 protein could be consistently coimmunoprecipitated with cyclin D1 from both cell lines and cases. Using techniques of exhaustive immunoprecipitation, we could demonstrate that most p27 protein was sequestered into complexes containing cyclin D1. We hypothesize that mantle cell lymphomagenesis results not only from direct consequences of inappropriate cyclin D1 expression, but also from the ability of overexpressed cyclin D1 to buffer physiologic changes in p27 levels, thereby rendering p27 ineffective as an inhibitor of cellular growth.