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.

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.

Treatment of chronic myelogenous leukemia with interleukin-2: a phase II study in 21 patients.

We designed a phase II study to assess the activity of recombinant interleukin-2 (rIL-2) in patients with chronic myelogenous leukemia (CML). Study population included 11 patients in the chronic phase of CML (6 in hematologic remission and 5 with active disease), 6 patients in the accelerated phase, and 4 in blastic phase of CML. Patients received three 5-day cycles administrated every other week. rIL-2 was given as intravenous bolus infusions of 8 x 10(6) IU/m2 three times a day during cycle 1 and twice a day during cycles 2 and 3. Response to rIL-2 was assessed on day 45. No hematologic response was achieved in the patients with evaluable disease. One patient in hematologic remission with rIL-2 achieved a major response (from 72% to 9% Ph+ metaphases), and two patients had some degree of reduction of Ph+ metaphases. Responses were short-lived (< 6 months), but two of these three patients achieved a new cytogenetic response with interferon given post-rIL-2. A significant immune activation was achieved with rIL-2 including a marked increase in CD3+/CD25+ cells, CD56+ cells, and in natural killer/lymphokine activated killer cell cytotoxic activity. These results confirm preclinical studies, which showed that IL-2 has antileukemic activity in CML. However, the responses observed were short lived and restricted to a subgroup of patients with low disease burden. This invites further studies testing its impact in situations of minimal disease or in combination with other cytokines.

The use of a sequential high dose recombinant interleukin 2 regimen after autologous bone marrow transplantation does not improve the disease free survival of patients with acute leukemia transplanted in first complete remission.

We report the outcome of 50 consecutive patients with CR1 acute leukemia (AML = 22; ALL = 28) treated with autologous BMT, after cyclophosphamide and TBI, followed with a sequential high dose rIL2 regimen. rIL-2 (RU 49637 from Roussel-Uclaf, Romainville, France) was started after hematological reconstitution an average of 72 +/- 22 days post transplant. The schedule consisted of a continuous infusion over 5 cycles (Cycle 1: 5 days starting on day 1; cycle 2-5: 2 days starting on day 15, 29, 43 and 57). Patients were treated at 4 different dosages (12 (N = 40), 16 (N = 3), 20 (N = 2), 24 (N = 5) x 10(6) IU/m2/day). Toxicities were mainly related to capillary leak syndrome and thrombocytopenia. Patients received an average of 122 +/- 49 10(6) IU/m2. Two patients with AML died from toxicity. rIL-2 infusion was associated with very a high level of immune stimu-lation of both T-cells (P < 0.05) and natural killer (NK) cells (P < 0.05) and associated cytolytic functions (P < 0.05). With a minimal and median follow-up of 21 and 46 months, 3 year leukemia free survival is 41 +/- 6% overall, 39 +/- 10% and 43 +/- 8% for AML and ALL respectively. Relapse probabilities at 3 years are 59 +/- 11% for AML and 57 +/- 8% for ALL. We conclude that this short infusion of rIL-2 over 2 months, resulting in an increased immune stimulation, is not associated with a better leukemic control for patients with acute leukemia transplanted early after reaching first complete remission.

A pilot study of autologous bone marrow transplantation followed by recombinant interleukin-2 in malignant lymphomas.

In this study, we investigated the impact of recombinant interleukin-2 (rIL-2) after high dose chemotherapy and autologous bone marrow transplantation (ABMT) in 25 patients with refractory or relapsed Hodgkin's disease (HD) (11 patients) and non Hodgkin's lymphoma (NHL) (14 patients). 48% of patients had resistant disease, 84% achieved complete remission after ABMT. rIL-2 was started at a median of 54 days post-transplant and consisted of a first cycle of 5 days followed by 4 cycles of 2 days every other week. Patients received a mean of 160 x 10(6) IU/m2 rIL-2 and hematological toxicity was moderate and transient. None of the 5 evaluable patients with measurable disease responded to rIL-2. After a 5 year median follow-up, the probability of survival and DFS is 72% (HD: 73% and NHL: 70%, p = NS) and 45% (HD: 36% and NHL: 48%, p = NS) respectively. These somewhat encouraging results warrant further evaluation of rIL-2 after ABMT in controlled studies, especially in NHL patients stratified for previous chemosensitivity.