Activation of the PI3K/AKT pathway by microRNA-22 results in CLL B-cell proliferation.

Chronic lymphocytic leukemia (CLL) is characterized by accumulation of clonal B cells arrested in G0/G1 stages that coexist, in different proportions, with proliferative B cells. Understanding the crosstalk between the proliferative subsets and their milieu could provide clues on CLL biology. We previously identified one of these subpopulations in the peripheral blood from unmutated patients that appears to be a hallmark of a progressive disease. Aiming to characterize the molecular mechanism underlying this proliferative behavior, we performed gene expression analysis comparing the global mRNA and microRNA expression of this leukemic subpopulation, and compared it with their quiescent counterparts. Our results suggest that proliferation of this fraction depend on microRNA-22 overexpression that induces phosphatase and tensin homolog downregulation and phosphoinositide 3-kinase (PI3K)/AKT pathway activation. Transfection experiments demonstrated that miR-22 overexpression in CLL B cells switches on PI3K/AKT, leading to downregulation of p27(-Kip1) and overexpression of Survivin and Ki-67 proteins. We also demonstrated that this pathway could be triggered by microenvironment signals like CD40 ligand/interleukin-4 and, more importantly, that this regulatory loop is also present in lymph nodes from progressive unmutated patients. Altogether, these results underline the key role of PI3K/AKT pathway in the generation of the CLL proliferative pool and provide additional rationale for the usage of PI3K inhibitors.

Post-transcriptional regulation of inducible nitric oxide synthase in chronic lymphocytic leukemia B cells in pro- and antiapoptotic culture conditions.

Functional inducible NOS (iNOS) may be involved in the prolonged lifespan of chronic lymphocytic leukemia cells (B-CLL), although the exact mechanisms implicated remain elusive as yet. In this work, we have examined iNOS expression in normal B lymphocytes and B-CLL cells in pro- and antiapoptotic conditions. Our results demonstrate: (1) The existence of a new splice variant characterized by a complete deletion of exon 14 (iNOS 13-16(14del)), which was preferentially detected in normal B lymphocytes and may represent an isoform that could play a role in the regulation of enzyme activity. (2) The existence of another alternatively spliced iNOS mRNA transcript involving a partial deletion of the flavodoxin region (iNOS 13-16(neg)) was correlated to a decreased B-CLL cell viability. The 9-beta-D-arabinofuranosyl-2-fluoradenine or fludarabine (F-ara) treatment induced iNOS 13-16(neg) transcript variants, whereas IL-4 enhanced both the transcription of variants, including these exons (iNOS 13-16(pos)), and the expression of a 122 kDa iNOS protein. These results suggest that in B-CLL, a regulation process involving nitric oxide (.- NO) levels could occur by a post-transcriptional mechanism mediated by soluble factors. Our results also provide an insight into a new complementary proapoptotic action of F-ara in B-CLL by the induction of particular iNOS splice variants, leading to the activation of a caspase-3-dependent apoptotic pathway.

Simultaneous PML/RARalpha and AML1/ETO expression with t(15;17) at onset and relapse with only t(8;21) in an acute promyelocytic leukemia patient.

We report a patient with acute promyelocytic leukemia with the common translocation (15;17) and PML-RARAalpha fusion gene. In relapse, blasts showed typical FAB M2 morphologic features, and the karyotype was 45,X, -Y,t(8;21). A reexamination of the leukemic cells at diagnosis revealed that an AML1-ETO fusion gene was also present at that time without cytogenetic evidence of t(8;21). In relapse, only t(8;21) was detected. Two different clones were identified by cytogenetic standard techniques. The association of two common translocations supervening in the same time in the same cells could not be established.

Evaluation of hematopoietic progenitors in hematopoietic progenitor cell transplants. CD34+ dose effect in marrow recovery. Retrospective analysis in 38 patients.

Our main goal was to evaluate the CD34+ dose in patients undergoing haemotopoietic stem celltransplantation and its results in terms of recovery of neutrophile and platelet counts, transfusion requirements, days of fever, antibiotic requirements and length of hospital stay. We studied 38 consecutive patients with haematological malignancies transplanted at our Department, from Feb. 96 through Sept. 98. The CD34+ cell quantification technique was standardized, using a modification of the ISAGHE 96 protocol. Patients were sorted into three groups according to the CD34+ count administered: a) between 3 and 5 x 10(6) cells/kg; b) between 5 and 10 x 10(6) cells/kg; c) > 10 x 10(6) CD34+ cells/kg. As a secondary end point, results were assessed according to the number of aphereses required to arrive at the target count of CD34+, separating those patients that required only 1 or 2 aphereses versus those requiring 3 or more. Finally, an analysis was made of the results of transplantation comparing the different sources of stem cells (PBSC versus PBSC + B.M.). The best results were obtained in the group with cells between 3 and 5 x 10(6) CD34+. No statistically significant advantages were found in the group with cells over 5. The supra-optimal dose of more 10 x 10(6) would yield no additional beneficial results, while they can imply a greater infusion of residual tumor cells. The number of aphereses had no impact on engraftment. Results obtained with PBSC transplants were better than those with BM+PBSC in terms of neutrophile and platelet recovery. The number of CD34+ cells remains the main element in stem cell transplantation to evaluate the haematopoietic recovery after engraftment. Minimum and optimum yields remain unclear. Centers should establish their own optimal dose based on local methodologies and outcomes, maximizing costs and benefits.

Heterogeneity of human T lymphocytes to bind sheep red blood cells in multiple sclerosis patients and controls.

The present studies were performed as a result of the report that the human T-cells may be composed of heterogeneous subpopulation in the sense of their ability to bind SRBC. In this paper, the diversity of human peripheral lymphocytes in M.S. patients, other neurological diseases and controls were investigated by means of an interesting approach based on the heterogeneity of humnan T-lymphocytes examined by the rosette formation of SRBC (E rosette) in two different reaction media.