Canthin-6-one induces cell death, cell cycle arrest and differentiation in human myeloid leukemia cells.

BACKGROUND: Canthin-6-one is a natural product isolated from various plant genera and from fungi with potential antitumor activity. In the present study, we evaluate the antitumor effects of canthin-6-one in human myeloid leukemia lineages. METHODS: Kasumi-1 lineage was used as a model for acute myeloid leukemia. Cells were treated with canthin-6-one and cell death, cell cycle and differentiation were evaluated in both total cells (Lin+) and leukemia stem cell population (CD34+CD38-Lin-/low). RESULTS: Among the human lineages tested, Kasumi-1 was the most sensitive to canthin-6-one. Canthin-6-one induced cell death with apoptotic (caspase activation, decrease of mitochondrial potential) and necrotic (lysosomal permeabilization, double labeling of annexin V/propidium iodide) characteristics. Moreover, canthin-6-one induced cell cycle arrest at G0/G1 (7µM) and G2 (45µM) evidenced by DNA content, BrdU incorporation and cyclin B1/histone 3 quantification. Canthin-6-one also promoted differentiation of Kasumi-1, evidenced by an increase in the expression of myeloid markers (CD11b and CD15) and the transcription factor PU.1. Furthermore, a reduction of the leukemic stem cell population and clonogenic capability of stem cells were observed. CONCLUSIONS: These results show that canthin-6-one can affect Kasumi-1 cells by promoting cell death, cell cycle arrest and cell differentiation depending on concentration used. GENERAL SIGNIFICANCE: Canthin-6-one presents an interesting cytotoxic activity against leukemic cells and represents a promising scaffold for the development of molecules for anti-leukemic applications, especially by its anti-leukemic stem cell activity.

Expression of adhesion molecules on CD34+ cells from steady-state bone marrow before and after mobilization and their association with the yield of CD34+ cells.

BACKGROUND: Cell adhesion molecules (CAMs) expressed on hematopoietic progenitor cells (HPCs), endothelial cells, and stromal cells play a pivotal role in the mobilization of CD34+ cells. Herein, we conducted a non-randomized peripheral blood stem cell (PBSC) mobilization study aimed to compare the potential differences in the expressions of several CAMs and chemokines on CD34+ cells obtained from bone marrow aspirate before and after HPC mobilization from patients with hematologic malignancies and healthy donors. METHODS: Three-color cytofluorometric analysis was used to compare the expressions of CAMs and chemokines in the bone marrow before and after mobilization. RESULTS: For all studied groups, CAM expression among those with good and poor yields of CD34+ cells was significantly correlated with VCAM-1 (P=0.007), CD44 (P=0.027), and VLA-4 (P=0.014) expressions. VCAM-1 (P=0.001), FLT-3 (P=0.001), CD44 (P=0.011), VLA-4 (P=0.001), and LFA-1 (P=0.001) expressions were higher before HPC mobilization than after HPC mobilization. By contrast, the expression of CXCR4 significantly varied before and after mobilization only among those with successful PBSC mobilization (P=0.002). CONCLUSION: We attempted to identify particular aspects of CAMs involved in CD34+ cell mobilization, which is a highly complex mechanism that involves adhesion molecules and matrix metalloproteases. The mechanism by which CD34+ cell mobilization is activated through proteolytic enzymes is not fully understood. We believe that CXCR4, VLA-4, CD44, and VCAM-1 are the most important molecules implicated in HPC mobilization, particularly because they show a correlation with the yield of CD34+ cells collected via large volume leukapheresis.

Possible influence of clinical stage and type of treatment in the persistence of residual circulating t(14;18)-positive cells in follicular lymphoma patients.

Many patients with follicular lymphoma (FL) achieve response after treatment but complete remission (CR) rates are very low. Thus the majority of them will relapse, mainly those in advanced stage disease, due to the persistence of residual disease. Therefore, this study had the following aims: to determine the presence of bcl-2/IgH rearrangement in peripheral blood of early and advanced stage FL patients after treatment and to correlate it with their clinical situation at the same moment. We obtained 100 consecutive peripheral blood samples from 30 FL cases and conducted molecular studies using two separate semi-nested PCRs for MBR and mcr rearrangements. These semi-nested PCRs for bcl-2/IgH rearrangement were able to detect one positive cell among 10,000 normal cells. Clinical and molecular evolution of patients diagnosed as early stage disease suggested that molecular response could be obtained even with conventional chemotherapy or radiotherapy. In this group of patients, 64% achieved molecular response in some point during follow-up. However, only 23% of patients diagnosed as advanced stage disease reached molecular response when treated with chemotherapy (with or without radiotherapy). Due to the low number of subjects assessed in this study, we only found a tendency to significance when clinical stage at the diagnosis was associated to molecular response (P = 0.095). We observed 100% of concordance between clinical remission and molecular response in patients after bone marrow transplantation or in those cases treated with monoclonal antibody anti-CD20. This retrospective study, performed in a restricted number of patients, suggests that molecular response can be obtained in FL patients diagnosed at early stage disease, even with conventional chemotherapy and radiotherapy. In advanced stage disease, concordance between clinical remission and molecular response was observed in the majority of patients after bone marrow transplantation or in those cases treated with monoclonal antibody anti-CD20. The prognostic significance of this data should be confirmed with extended follow-up and in a larger number of patients.

2-Chloro-deoxyadenosine induces durable complete remission in Castleman's disease but may accelerate its transformation to non-Hodgkin's lymphoma.

There is currently no consensus on the best treatment for unresectable hyaline-vascular variant or for multicentric Castleman's disease (MCD), because none of the reported regimens have consistently produced complete response or durable remission in the majority of patients In the present study, we report on the use of 2-CdA (2-chloro-deoxyadenosine) in three patients, two of them with MCD and one with unresectable hyaline-vascular type disease. Relapse-free survival of the responding patients was 24 and 20 months. Later, both patients evolved to non-Hodgkin's lymphoma (NHL) (diffuse large B-cell lymphoma and peripheral T-cell NHL, respectively). 2-CdA typically causes a long-lasting state of immunodeficiency and the profound influence of this drug on the immune system has raised questions concerning the emergence of secondary neoplasms after its use. Therefore, it is reasonable to conclude that: 1) 2-CdA can induce durable complete remission in MCD patients but unfortunately it cannot cure the disease; 2) the possibility that 2-CdA may accelerate the transformation of MCD to NHL cannot be ruled out.