Fludarabine-induced apoptosis of B chronic lymphocytic leukemia cells includes early cleavage of p27kip1 by caspases

Formaldehyde exacerbates inflammation and biases T helper cell lineage commitment through IFN-γ/STAT1/T-bet pathway in asthma

The correlation between formaldehyde (FA) exposure and prevalence of asthma has been widely reported. However, the underlying mechanism is still not fully understood. FA exposure at 2.0 mg/m3 was found to exacerbate asthma in OVA-induced murine models. IFN-γ, the cytokine produced by T helper 1 (Th1) cells, was significantly induced by FA in serum and bronchoalveolar lavage fluid (BALF) of asthmatic mice, which was different from cytokines secreted by other Th cells. The observation was also confirmed by mRNA levels of Th marker genes in CD4+ T cells isolated from BALF. In addition, increased production of IFN-γ and expression of T-bet in Jurkat T cells primed with phorbol ester and phytohaemagglutinin were also observed with 100 μM FA treatment in vitro. Upregulated STAT1 phosphorylation, T-bet expression and IFN-γ production induced by FA was found to be restrained by STAT1 inhibitor fludarabine, indicating that FA promoted Th1 commitment through the autocrine IFN-γ/STAT1/T-bet pathway in asthma. This work not only revealed that FA could bias Th lineage commitment to exacerbate allergic asthma, but also identified the signaling mechanism of FA-induced Th1 differentiation, which may be utilized as the target for development of interfering strategies against FA-induced immune disorders.

Ceragenins exhibit antiviral activity against SARS-CoV-2 by increasing the expression and release of type I interferons upon activation of the host's immune response

The COVID-19 pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) heavily burdened the entire world socially and economically. Despite a generation of vaccines and therapeutics to confront infection, it remains a threat. Most available antivirals target viral proteins and block their activity or function. While such an approach is considered effective and safe, finding treatments for specific viruses of concern leaves us unprepared for developed resistance and future viral pandemics of unknown origin. Here, we propose ceragenins (CSAs), synthetic amphipathic molecules designed to mimic the properties of cationic antimicrobial peptides (cAMPs), as potential broad-spectrum antivirals. We show that selected CSAs exhibit antiviral activity against SARS-CoV-2 and low-pathogenic human coronaviruses 229E, OC43, and NL63. The mechanism of action of CSAs against coronaviruses is mainly attributed to the stimulation of antiviral cytokines, such as type I interferons or IL-6. Our study provides insight into a novel immunomodulatory strategy that might play an essential role during the current pandemic and future outbreaks.

FDA-approved pyrimidine-fused bicyclic heterocycles for cancer therapy: Synthesis and clinical application

Considerable progress has been made in the development of anticancer agents over the past few decades, and a lot of new anticancer agents from natural and synthetic sources have been produced. Among heterocyclic compounds, pyrimidine-fused bicyclic heterocycles possess a variety of biological activities such as anticancer, antiviral, etc. To date, 147 pyrimidine-fused bicyclic heterocycles have been approved for clinical assessment or are currently being used in clinic, 57 of which have been approved by FDA for clinical treatment of various diseases, and 22 of them are being used in the clinic for the treatment of different cancers. As the potentially privileged scaffolds, pyrimidine-fused bicyclic heterocycles may be used to discover new drugs with similar biological targets and improved therapeutic efficacy. This review aims to provide an overview of the anticancer applications and synthetic routes of 22 approved pyrimidine-fused bicyclic heterocyclic drugs in clinic.

Role of ZNF224 in cell growth and chemoresistance of chronic lymphocitic leukemia

Chronic lymphocytic leukaemia (CLL) is associated with apoptosis resistance and defective control of cell growth. Our study describes for the first time a critical role in CLL for the KRAB-zinc finger protein ZNF224. High ZNF224 transcript levels were detected in CLL patients with respect to control cells. Moreover, ZNF224 expression was significantly lowered after conventional chemotherapy treatment in a subset of CLL patients. By in vitro experiments we confirmed that ZNF224 expression is suppressed by fludarabine and demonstrated that ZNF224 is involved in apoptosis resistance in CLL cells. Moreover, we showed that ZNF224 positively modulates cyclin D3 gene expression. Consistently, we observed that alteration of ZNF224 expression leads to defects in cell cycle control. All together, our results strongly suggest that in CLL cells high expression level of ZNF224 can lead to inappropriate cell growth and apoptosis resistance, thus contributing to CLL progression. Targeting ZNF224 could thus improve CLL response to therapy.

ZGDHu-1 and fludarabine have a synergistic effect on apoptosis of chronic lymphocytic leukemia cells

Previously, it was demonstrated that the novel proteasome inhibitor N,N'-di-(m-methylphenyi)-3,6-dimethyl-1,4-dihydro-1,2,4,5-tetrazine-1,4-dicarboamide (ZGDHu‑1) possesses activity against chronic lymphocytic leukemia (CLL). In the present study, we attempted to assess whether this drug has a synergistic effect with fludarabine on the apoptosis of CLL cells. Annexin V/PI staining, mitochondrial membrane potential (ΔΨm) and reactive oxygen species (ROS) levels were examined by flow cytometry in short-term cell culture of blood cells from untreated newly diagnosed patients ex vivo. Expression of active caspase-3 and the Bcl-2/Bax ratio for determination of apoptosis were also investigated by flow cytometry and western blot analysis. Our results revealed that the ZGDHu-1 may induce the apoptosis of CLL cells through the mitochondrial pathway and its pro-apoptotic effect is CLL-specific, not affecting normal lymphocytes. Most importantly, a combination of ZGDHu-1 and a non-cytotoxic dose of fludarabine had a synergistic apoptotic effect. To some extent, caspase-3 activation may be involved in the mechanism of the ZGDHu-1 synergistic cytotoxic effect with fludarabine, as well as the cleavage of PARP, consequently leading to apoptosis. Notably, the rate of apoptosis caused by ZGDHu-1 alone or in combination with fludarabine was independent of prognostic markers of CLL disease such as ZAP-70 and CD38 expression or clinical Rai classification stage. In conclusion, ZGDHu-1 exhibited a significant synergistic effect with fludarabine to induce the apoptosis of CLL cells, which implies a possible clinical application.

High p27 protein levels in chronic lymphocytic leukemia are associated to low Myc and Skp2 expression, confer resistance to apoptosis and antagonize Myc effects on cell cycle

Myc (c-Myc) counteracts p27 effects, and low p27 usually correlates with high Myc expression in human cancer. However there is no information on the co-expression of both genes in chronic lymphocytic leukemia (CLL). We found a lack of correlation between RNA and protein levels of p27 and Myc in CLL cells, so we determined the protein levels by immunoblot in 107 cases of CLL. We observed a high p27 protein expression in CLL compared to normal B cells. Ectopic p27 expression in a CLL-derived cell line resulted in cell death resistance. Surprisingly, Myc expression was very low or undetectable in most CLL cases analyzed, with a clear correlation between high p27 and low Myc protein levels. This was associated with low Skp2 expression, which is consistent with the Skp2 role in p27 degradation and with SKP2 being a Myc target gene. High Myc expression did not correlate with leukemia progression, despite that cell cycle-related Myc target genes were upregulated. However, biochemical analysis showed that the high p27 levels inhibited cyclin-Cdk complexes even in Myc expressing CLL cells. Our data suggest that the combination of high p27 and low Myc is a marker of CLL cells which is mediated by Skp2.

Alterations in TP53, cyclin D2, c-Myc, p21WAF1/CIP1 and p27KIP1 expression associated with progression in B-CLL

B-cell chronic lymphocytic leukaemia (B-CLL) originates from B lymphocytes that may differ in the activation level, maturation state or cellular subgroups in peripheral blood. Tumour progression in CLL B cells seems to result in gradual accumulation of the clone of resting B lymphocytes in the early phases (G0/G1) of the cell cycle. The G1 phase is impaired in B-CLL. We investigated the gene expression of five key cell cycle regulators: TP 53, c-Myc, cyclin D2, p21WAF1/CIP1 and p27KIP1, which primarily regulate the G1 phase of the cell cycle, or S-phase entry and ultimately control the proliferation and cell growth as well as their role in B-CLL progression. The study was conducted in peripheral blood CLL lymphocytes of 40 previously untreated patients. Statistical analysis of correlations of TP53, cyclin D2, c-Myc, p21WAF1/CIP1 and p27KIP1 expressions in B-CLL patients with different Rai stages demonstrated that the progression of disease was accompanied by increases in p53, cyclin D2 and c-Myc mRNA expression. The expression of p27KIP1 was nearly statistically significant whereas that of p21 WAF1/CIP1 showed no such correlation. Moreover, high expression levels of TP53 and c-Myc genes were found to be closely associated with more aggressive forms of the disease requiring earlier therapy.

The B lineage transcription factor E2A regulates apoptosis in chronic lymphocytic leukemia (CLL) cells

Chronic lymphocytic leukemia (CLL) is a common malignancy characterized by the accumulation of B lymphocytes with an antigen-experienced activated CD19(+)CD5(+) clonal phenotype. Clinically, ∼50% of cases will behave more aggressively. Here, we investigate the role of the major B-cell transcription factor E2A, a known regulator of B-cell survival and proliferation, to CLL persistence. We show that E2A is elevated at the mRNA and protein levels relative to normal B-cell subsets. E2A silencing in primary CLL cells leads to a significant increase in spontaneous apoptosis in both CD38(+) (aggressive) and CD38(-) (indolent) cases. Moreover, E2A knockdown synergizes with the immunomodulatory drug lenalidomide to reduce CLL viability. E2A is known to restrain the proliferation of primary B and T lymphocytes at multiple stages of maturation and we report that targeted E2A disruption increases the frequency of Ki-67(+) CLL cells in the absence of effects on de novo proliferation. At the molecular level, E2A siRNA-treated CLL cells display reduced expression of key genes associated with survival and cell cycling including p27, p21 and mcl-1, of which the former two are known E2A target genes. Thus, E2A, a key transcription factor associated with the B-cell activation profile, regulates apoptosis in CLL and may contribute to disease pathology.

Circulating Ki-67 index in plasma as a biomarker and prognostic indicator in chronic lymphocytic leukemia

Ki-67 is a nuclear antigen that is expressed in all stages of the cell cycle, except G(0), and is widely used as a marker of cellular proliferation in human tumors. We recently showed that elevated levels of Ki-67 circulating in plasma (cKi-67) are associated with shorter survival in patients with acute lymphoblastic leukemia. The current study included 194 patients with CLL and 96 healthy control subjects. cKi-67 levels in plasma were determined using an electrochemiluminescent immunoassay. We normalized the cKi-67 level to the absolute number of lymphocytes in the patient's peripheral blood to establish the plasma cKi-67 index. The cKi-67 index showed significant correlation with lymph node involvement and Rai stage (P=0.05). Higher cKi-67 index values were significantly associated with shorter survival. Multivariate Cox proportional hazards regression analysis demonstrated that the association of the cKi-67 index with shorter survival was independent of IgV(H) mutation status. In a multivariate model incorporating the cKi-67 index with B2M and IgV(H), only cKi-67 index and B2M levels remained as independent predictors of survival. The results of this study suggest that the plasma cKi-67 index, along with B2M level, is a strong predictor of clinical behavior in CLL.

Low-dose fludarabine increases rituximab cytotoxicity in B-CLL cells by triggering caspases activation in vitro

Rituximab maintenance therapy provides a significant benefit in patients with indolent B-cell non-Hodgkin lymphoma (NHL). Based on its efficacy in improving response to chemotherapy, the anti-CD20 antibody is currently under evaluation as maintenance therapy also in patients with B-CLL. We evaluated rituximab-mediated cytotoxicity in 10 B-CLL cases pretreated in vitro with non-cytotoxic concentrations of fludarabine. This combination induced a synergic cytotoxic effect in 8 out of 10 patients at a mean level of 26.15 +/- 13.9%, compared to 8.05 +/- 5.3% cytotoxicity observed with rituximab alone. Consistent with the viability assay, we found an increased caspase-3 activity together with activation of caspase-9 in B-CLL cells sensitive to sequential non-cytotoxic fludarabine and rituximab exposure. Non-cytotoxic fludarabine concentrations may sensitize B-CLL cells to rituximab-mediated cytotoxicity via caspase-3 activation.

High expression of AID and active class switch recombination might account for a more aggressive disease in unmutated CLL patients: link with an activated microenvironment in CLL disease

Interaction of chronic lymphocytic leukemia (CLL) B cells with tissue microenvironment has been suggested to favor disease progression by promoting malignant B-cell growth. Previous work has shown expression in peripheral blood (PB) of CLL B cells of activation-induced cytidine deaminase (AID) among CLL patients with an unmutated (UM) profile of immunoglobulin genes and with ongoing class switch recombination (CSR) process. Because AID expression results from interaction with activated tissue microenvironment, we speculated whether the small subset with ongoing CSR is responsible for high levels of AID expression and could be derived from this particular microenvironment. In this work, we quantified AID expression and ongoing CSR in PB of 50 CLL patients and characterized the expression of different molecules related to microenvironment interaction. Our results show that among UM patients (1) high AID expression is restricted to the subpopulation of tumoral cells ongoing CSR; (2) this small subset expresses high levels of proliferation, antiapoptotic and progression markers (Ki-67, c-myc, Bcl-2, CD49d, and CCL3/4 chemokines). Overall, this work outlines the importance of a cellular subset in PB of UM CLL patients with a poor clinical outcome, high AID levels, and ongoing CSR, whose presence might be a hallmark of a recent contact with the microenvironment.

MicroRNA and proliferation control in chronic lymphocytic leukemia: functional relationship between miR-221/222 cluster and p27

We investigated functional relationships between microRNA 221/222 (miR-221/222) cluster and p27, a key regulator of cell cycle, in chronic lymphocytic leukemia (CLL). The enforced expression of miR-221/222 in the CLL cell line MEC1 induced a significant down-regulation of p27 protein and conferred a proliferative advantage to the transduced cells that exhibited faster progression into the S phase of the cell cycle. Accordingly, expression of miR-221/miR-222 and p27 was found to be inversely related in leukemic cells obtained from peripheral blood (PB) of 38 patients with CLL. Interestingly, when miR-221/222 and p27 protein were evaluated in different anatomic compartments (lymph nodes or bone marrow) of the same patients, increased expression of the 2 miRNAs became apparent compared with PB. This finding was paralleled by a low expression of p27. In addition, when CLL cells were induced in vitro to enter cell cycle (eg, with cytosine phosphate guanine oligodeoxynucleotide), a significant increase of miR-221/222 expression and a marked down-regulation of p27 protein were evident. These data indicate that the miR-221/222 cluster modulates the expression of p27 protein in CLL cells and lead to suggest that miR-221/222 and p27 may represent a regulatory loop that helps maintaining CLL cells in a resting condition.

High Mda-7 expression promotes malignant cell survival and p38 MAP kinase activation in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL)-B-cells are quiescent differentiated cells that produce interleukin (IL)-10 and accumulate due to resistance to apoptosis. The mechanisms underlying such resistance are poorly understood. Herein we show that all CLL B-cells tested (30/30) display high mRNA and protein expression of the tumor suppressor Mda-7/IL-24, an IL-10 family member, in comparison to normal B cells. A downstream Mda-7 signaling target, p38 mitogen-activated protein kinase (MAPK) was highly phosphorylated in all CLL cells but not in normal B-cells. Mda-7 expression and p38 MAPK phosphorylation diminished in culture and the latter could be reinduced by recombinant (r)-IL-24 or LPS and Mda-7 transfection. Mda-7/IL-24 siRNA specifically inhibited p38 MAPK phosphorylation in CLL without affecting p38 MAPK, bcl2, or Lyn expression, further demonstrating the direct role of Mda-7/IL-24 in p38 MAPK activation. Both pharmacological inhibition of p38 MAPK and Mda-7 silencing augmented spontaneous apoptosis by three-fold in CLL cells cultured in autologous serum, which was reversed by LPS and r-IL-24. We established the role of p38 MAPK in CLL cell survival and demonstrated a paradoxical effect, whereby Mda-7 and IL-24, inducers of apoptosis in diverse cancer cells, promote the survival of CLL B-cells through p38 MAPK activation.

Interleukin-21 receptor (IL-21R) is up-regulated by CD40 triggering and mediates proapoptotic signals in chronic lymphocytic leukemia B cells

Interleukin-21 (IL-21) is a member of the IL-2 cytokine family, which mediates proliferation or growth arrest and apoptosis of normal B cells, depending on their activation state. Here we demonstrate that surface IL-21 receptor (R) is expressed at variable levels by chronic lymphocytic leukemia (CLL) B cells freshly isolated from 33 different patients. IL-21R expression was up-regulated following cell stimulation via surface CD40. Therefore, IL-21 effects were more evident in CD40-activated CLL B cells. IL-21 induced an early signaling cascade in CLL B cells, which included JAK-1 and JAK-3 autophosphorylation and tyrosine phosphorylation of STAT-1, STAT-3, and STAT-5. IL-21 signaling failed to stimulate CLL B-cell proliferation, but induced their apoptosis. In addition, IL-21 counteracted the proliferative and antiapoptotic signals delivered by IL-15 to CLL B cells. IL-21-mediated apoptosis involved activation of caspase-8 and caspase-3, cleavage of Bid to its active form t-Bid, and cleavage of PARP and of p27Kip-1. Recent data indicate that CLL B cells require interaction with the microenvironment for their survival and expansion. The present findings thus provide a set of new mechanisms involved in the balance between cell-survival and apoptotic signals in CLL B cells.

Effect of fludarabine on leukocyte functions

BACKGROUND

Fludarabine induces leukemic cell apoptosis and is highly efficient in chronic lymphocytic leukemia. However, fludarabine therapy causes severe leukopenia. Leukocyte myeloperoxidase (MPO) catalyzes the formation of HOCl, and this is the main microbicidal function in phagocytes. The aim of our study was to evaluate the effect of fludarabine on leukocytes, i.e. their degranulation capacity, MPO activity and HOCl production.

METHODS

Peripheral blood leukocytes were incubated for 48 h with fludarabine. Degranulation was measured using a flow-cytometric method. MPO activity and HOCl production were measured spectrophotometrically.

RESULTS

The degranulation capacity of fludarabine-treated leukocytes was significantly elevated compared to untreated controls. MPO activity and HOCl production were also increased in parallel. A possible direct activating effect of fludarabine was tested on the MPO activity of HL60 cells. Fludarabine did not affect MPO activity at concentrations ranging from 10 microM to 2 mM.

CONCLUSION

Fludarabine had no inhibitory effect on the microbial killing of leukocytes.

Prognostic impact of p27KIP1 expression in cyclin D1 positive lymphoproliferative disorders

Nodal mantle cell lymphoma (MCL) is a well-defined entity, but non-nodal leukemic cyclin D1 positive lymphoproliferative disorders have been reported and their relationship with MCL remains controversial and their prognosis heterogeneous. We prospectively studied the expression of cyclin D1 in CD5 positive leukemic B lymphoproliferative disorders at diagnosis and identified 65 cases overexpressing cyclin D1. We did not distinguish any clinical or biological criteria allowing one to identify a non-MCL group. Multivariate analysis identified age, anemia and p27kip1 expression as independent prognostic factors of survival. By univariate analysis, p27kip1 high expression proved to be the strongest predictor of prolonged survival. The median survival of p27 low expressors was 30 months, while it was not reached for p27 high expressors. A high level of p27 expression was often found associated with the absence of nodal involvement and the presence of somatic mutations, but neither of them was restricted to the p27 high expression group. In conclusion, we hypothesize that MCL and these cyclin D1 positive leukemic lymphoproliferative disorders represent a continuous spectrum of diseases. Determination of p27 expression level appears as a routine applicable test allowing identification of a subset of patients who could be considered for different therapeutic approaches.