Overexpression of FoxM1 offers a promising therapeutic target in diffuse large B-cell lymphoma

Background

FoxM1 has been shown to play a critical role in the pathogenesis of various epithelial malignancies. However, its role in lymphoid malignancies has not been fully clarified. We, therefore, investigated the role of FoxM1 expression in a large cohort of diffuse large B-cell lymphoma samples and panel of cell lines.

Design and Methods

FoxM1 expression was investigated in a large series of diffuse large B-cell lymphoma tissues in a tissue microarray format by immunohistochemistry. Apoptosis was measured by flow cytometry and protein expression was detected by immunoblotting using diffuse large B-cell lymphoma cell lines following treatment with either pharmacological inhibitor of FoxM1 or small interference RNA knockdown strategy. Invasion/migration and soft agar colony assays were also performed following treatment with FoxM1 inhibitor.

Results

FoxM1 expression was detected in 84.6% of diffuse large B-cell lymphoma tumors and found to be significantly associated with proliferative tumor marker Ki67 (P<0.0001), matrix metalloproteinases-2 (P=0.0008), matrix metalloproteinases-9 (P=0.0002), S-phase kinase associated protein-2 (P<0.0001) and inversely associated with p27 expression (P=0.0215). Expression of small interference RNA targeted against FoxM1 or treatment of diffuse large B-cell lymphoma cells with thiostrepton caused its downregulation accompanied by decreased expression of matrix metalloproteinases-2 and matrix metalloproteinases-9. Inhibition of FoxM1 in diffuse large B-cell lymphoma cells also decreased invasive and migratory capability, and induced caspase dependent apoptosis via activation of the mitochondrial apoptotic pathway. Finally, combined thiostrepton and bortezomib at sub-toxic doses led to efficient apoptosis in diffuse large B-cell lymphoma cells.

Conclusions

Altogether, these results suggest that FoxM1 is over-expressed in the majority of diffuse large B-cell lymphoma samples. These data also indicate that targeting FoxM1 signaling can serve as a potential therapeutic modality in the management of diffuse large B-cell lymphoma.     

A case report of cecal plasmablastic lymphoma in a HIV-negative patient

Plasmablastic lymphoma (PBL) is a unique type of diffuse proliferation of large neoplastic lymphoid cells most of which resemble B immunoblasts, but all tumor cells show the immunophenotype of plasma cells. It has a strong predilection for jaw and oral cavity in HIV-positive patients. Incidences of extraoral location of this tumor is increasingly being recognized especially in HIV-negative patients for example, stomach, jejunum, omentum, anorectum, lungs, testes, soft tissues, lymph nodes, bone marrow, skin, and central nervous system. We present a case of PBL found in cecum in an HIV-negative patient. It was accompanied by lung and lymph node involvement and presented as abdominal mass. This is only the second reported case of PBL originating in cecum.     

Universal Adhesive for Fixed Retainer Bonding: In Vitro Evaluation and Randomized Clinical Trial

This study aims to assess the efficacy of a universal adhesive (Scotchbond Universal, 3M ESPE) (SB) in total-etch mode, compared to a traditional orthodontic primer (Transbond XT Primer, 3M ESPE) (XT Primer), to perform bonding of orthodontic fixed retainers along with the Transbond XT Light Cure Adhesive Paste (3M ESPE). For the in vitro study, a round section wire (Ortosmail Krugg) was bonded using XT Primer for 20 bovine incisors (Group 1) and SB for other 20 (Group 2). Samples were debonded in a universal testing machine applying a tangential force to specimens (crosshead speed of 1 millimeter per minute). Shear bond strength (SBS) and adhesive remnant index (ARI) scores were calculated. For the in vivo study, 100 patients needing upper and lower canine-to-canine fixed retainers after orthodontic treatment were randomly assigned to two groups of 50 participants each, i.e., group 1 (retainer bonding with XT Primer) and group 2 (retainer bonding with SB). Over two years, examinations were carried out monthly, and detachments were registered by considering the teeth and arches affected. In vitro, no statistically significant differences in SBS and ARI scores were demonstrated between the two groups, both showing a mean bond strength of about 12 MPa and major frequency of ARI “2” (>50% remnant adhesive on the enamel). Conversely, a significantly lower failure rate over 2 years was assessed clinically for group 2 in both arches. Independently of the adhesive and arch, incisors reported a significantly higher failure rate than canines. Scotchbond Universal used in total-etch mode could be a valid alternative to the traditional orthodontic Transbond XT Primer.     

Perturbations in the erythroid marrow progenitor cell pools may play a role in the augmentation of HbF by 5-azacytidine

In vivo observations on the kinetics of F cells and of fetal hemoglobin (HbF) synthesis and in vitro studies of erythroid progenitors, their number, and the gamma-gene expression in their progeny were carried out in baboons (Papio cynocephalus) treated with 5-azacytidine. Maximum effect on the increase of HbF production in vivo was observed only when an expanded erythroid marrow population was present. In these animals, as well as in normal animals, treatment resulted in a significant reduction of the late erythroid progenitor cell pools (erythroid clusters and erythroid colony-forming units, CFU-E) in the marrow. This reduction was more pronounced among those progenitors grown in the absence of added erythropoietin, and it was followed by a rebound a few days after treatment cessation, reflecting the accumulation of regenerating progenitors. An early increase in the in vitro synthesis of HbF in erythroid clusters and CFU-E colonies was observed. This increase was further documented at the cellular level, with immunofluorescent labeling of colonies with monoclonal anti-gamma- globin chain antibodies. In contrast to the findings in late progenitors, the number of erythroid burst-forming unit (BFU-E) colonies and the synthesis of HbF in these colonies was not influenced significantly by 5-azacytidine treatment. It is proposed that the toxic effects of 5-azacytidine on late progenitors, leading to faster mobilization of earlier progenitors to the next more mature compartment, play a role in the in vivo augmentation of HbF synthesis by this drug. This perturbation in the progenitor cell population kinetics and the presumed hypomethylation of the surviving differentiating cells may act synergistically to produce a maximum HbF response after 5-azacytidine treatment.     

Effects of human FLT3 ligand on myeloid leukemia cell growth: heterogeneity in response and synergy with other hematopoietic growth factors

A novel hematopoietic growth factor for primitive hematopoietic progenitor cells, the ligand for the flt3/flk2 receptor, (FL), has been recently purified and its gene has been cloned. In the present study, we investigated the effects of FL on the proliferation and differentiation of normal and leukemic myeloid progenitor cells. We demonstrate that FL is a potent stimulator of the in vitro growth of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin- 3 (IL-3), or G-CSF-dependent granulocyte-macrophage committed precursors from Lin- CD34+ bone marrow cells of normal donors. By contrast, FL does not affect the growth of erythroid-committed progenitors even in the presence of erythropoietin. The effect of FL on the proliferation and on the in vitro growth of clonogenic leukemic precursor cells was studied in 54 acute myeloid leukemia (AML) cases. Fresh leukemia blasts from 36 of 45 patients with AML significantly responded to FL without any relation to the French-American-British (FAB) subtype. FL stimulated the proliferation of leukemic blasts in a dose-dependent fashion. Synergistic activities were seen when FL was combined with G-CSF, GM-CSF, IL-3, or stem cell factor (SCF). FL as a single factor induced or increased significantly colony formation by clonogenic precursor cells from 21 of 24 patients with AML. In the presence of suboptimal and optimal concentrations of G-CSF, GM-CSF, IL3, SCF, or a combination of all factors, FL strongly enhanced the number of leukemic colonies (up to 18-fold). We also evaluated the induction of tyrosine phosphorylated protein on FL stimulation in fresh AML cells. We demonstrate that, on FL stimulation, a band of phosphorylated protein(s) of about 90 kD can be detected in FL- responsive, but not in FL-unresponsive cases. This study suggests that FL may be an important factor for the growth of myeloid leukemia cells, either as a direct stimulus or as a synergistic factor with other cytokines.