Fludarabine induces apoptosis in chronic lymphocytic leukemia--the role of P53, Bcl-2, Bax, Mcl-1, and Bag-1 proteins

Autophagy in Hematological Malignancies

Simple Summary

Autophagy is a dynamic and tightly regulated process that seems to have dual effects in cancer. In some contexts, it can induce carcinogenesis and promote cancer cell survival, whereas in others, it acts preventing tumor cell growth and tumor progression. Thus, autophagy functions seem to strictly depend on cancer ontogenesis, progression, and type. Here, we will dive into the current knowledge of autophagy in hematological malignancies and will highlight the main genetic components involved in each cancer type.

Abstract

Autophagy is a highly conserved metabolic pathway via which unwanted intracellular materials, such as unfolded proteins or damaged organelles, are digested. It is activated in response to conditions of oxidative stress or starvation, and is essential for the maintenance of cellular homeostasis and other vital functions, such as differentiation, cell death, and the cell cycle. Therefore, autophagy plays an important role in the initiation and progression of tumors, including hematological malignancies, where damaged autophagy during hematopoiesis can cause malignant transformation and increase cell proliferation. Over the last decade, the importance of autophagy in response to standard pharmacological treatment of hematological tumors has been observed, revealing completely opposite roles depending on the tumor type and stage. Thus, autophagy can promote tumor survival by attenuating the cellular damage caused by drugs and/or stabilizing oncogenic proteins, but can also have an antitumoral effect due to autophagic cell death. Therefore, autophagy-based strategies must depend on the context to create specific and safe combination therapies that could contribute to improved clinical outcomes. In this review, we describe the process of autophagy and its role on hematopoiesis, and we highlight recent research investigating its role as a potential therapeutic target in hematological malignancies. The findings suggest that genetic variants within autophagy-related genes modulate the risk of developing hemopathies, as well as patient survival.

Clinical significance of bax/bcl-2 ratio in chronic lymphocytic leukemia

In chronic lymphocytic leukemia the balance between the pro-apoptotic and anti-apoptotic members of the bcl-2 family is involved in the pathogenesis, chemorefractoriness and clinical outcome. Moreover, the recently proposed anti-bcl-2 molecules, such as ABT-199, have emphasized the potential role of of bcl-2 family proteins in the context of target therapies. We investigated bax/bcl-2 ratio by flow cytometry in 502 patients and identified a cut off of 1.50 to correlate bax/bcl-2 ratio with well-established clinical and biological prognosticators. Bax/bcl-2 was 1.50 or over in 263 patients (52%) with chronic lymphocytic leukemia. Higher bax/bcl-2 was associated with low Rai stage, lymphocyte doubling time over 12 months, beta-2 microglobulin less than 2.2 mg/dL, soluble CD23 less than 70 U/mL and a low risk cytogenetic profile (P<0.0001). On the other hand, lower bax/bcl-2 was correlated with unmutated IGHV (P<0.0001), mutated NOTCH1 (P<0.0001) and mutated TP53 (P=0.00007). Significant shorter progression-free survival and overall survival were observed in patients with lower bax/bcl-2 (P<0.0001). Moreover, within IGHV unmutated (168 patients) and TP53 mutated (37 patients) subgroups, higher bax/bcl-2 identified cases with significant longer PFS (P=0.00002 and P=0.039). In multivariate analysis of progression-free survival and overall survival, bax/bcl-2 was an independent prognostic factor (P=0.0002 and P=0.002). In conclusion, we defined the prognostic power of bax/bcl-2 ratio, as determined by a flow cytometric approach, and highlighted a correlation with chemoresistance and outcome in chronic lymphocytic leukemia. Finally, the recently proposed new therapies employing bcl-2 inhibitors prompted the potential use of bax/bcl-2 ratio to identify patients putatively resistant to these molecules.

Qi-Dan Fang ameliorates adriamycin-induced nephrotic syndrome rat model by enhancing renal function and inhibiting podocyte injury

ETHNOPHARMACOLOGICAL RELEVANCE

Nephrotic syndrome (NS) is a clinical syndrome with a variety of causes, mainly characterized by heavy proteinuria. Podocyte injury plays a key role in proteinuria, one of the principal means for the control of NS is to prevent podocyte injury. Qi-Dan Fang consists of two of the most extensively applied herbal remedies among Traditional Chinese Medicine (TCM) (Radix Astragali Mongolici and Radix Salviae Miltiorrhizae, with a weight ratio of 5:1) which are specifically used for the treatment of various kidney diseases. In previous studies, we found that Qi-Dan Fang provides improvement to patients with adriamycin-induced nephrotic syndrome by alleviating proteinuria and serum lipid. The aim of this study is to study the efficiency of Qi-Dan Fang on NS model rat with renal dysfunction and podocyte injury, something which has not been carried out yet.

MATERIALS AND METHODS

The rats were divided into Normal, Model, Jin Gui Shen Qi Pill (4.12 g/kg), Qi-Dan Fang (3.09, 6.17 and 12.34 g/kg/d) groups, they were each given a single tail intravenous injection of Adriamycin (6.0 mg/kg) except for the Normal group and were orally administered dosages of Qi-Dian Fang and Jin Gui Shen Qi pills once daily for 7 weeks. Following the treatment, the content of cystation C (CysC), blood urea nitrogen (BUN), serum creatinine (Scr) were measured with an autobiochemical analyser. The pathomorphological changes to the glomeruli, the mRNA expressions of nephrin, podocin, CD2AP genes and p53, bax, bcl-2 proteins expressions were also carried out to probe the effects of Qi-Dan Fang.

RESULTS

(1) Qi-Dan Fang treatment raised the level of CysC in blood serum while lowering the content of BUN and Scr in the adriamycin-induced nephrotic syndrome rat model; (2) Long-term administration of Qi-Dan Fang was able to ameliorate pathomorphological change of glomeruli and repair the organization structure of Glomerulus; (3) Qi-Dan Fang could increase the mRNA expression of nephrin, podocin and CD2AP genes, down-regulate the expression of p53, bax proteins, while increased bcl-2 protein to protect the podocyte and restore Glomerular selective filtration function.

CONCLUSIONS

Results of our present studies reveal that Qi-Dan Fang is able to enhance renal function, inhibit podocyte injury to provide improvements to the Adriamycin-induced nephrotic syndrome.

The histone deacetylase inhibitor SAHA sensitizes acute myeloid leukemia cells to a combination of nucleoside analogs and the DNA-alkylating agent busulfan

Fludarabine (Flu), clofarabine (Clo) and busulfan (Bu) are used in allogeneic hematopoietic stem cell transplant (allo-HSCT). We reported that combining [Flu + Clo + Bu] had a synergistic cytotoxicity in AML cells. We hypothesized that combining [Flu + Clo + Bu] with the histone deacetylase inhibitor SAHA will further enhance cytotoxicity. We exposed the acute myeloid leukemia (AML) cell lines KBM3/Bu250(6) and OCI-AML3 to Flu, Clo, Bu and SAHA alone and in various combinations. [Flu + Clo + Bu + SAHA] resulted in synergistic cytotoxicity, which can be attributed to (1) activated DNA-damage response and cell cycle checkpoint activation through the ATM-CHK2-P53 (or P73) pathway or ATM-CHK2-cdc25-cdc2 pathway, (2) histone modifications and (3) activated apoptosis pathway. The [Flu + Clo + Bu + SAHA] combination causes mitochondrial outer membrane permeabilization, leakage of cytochrome c and Smac/Diablo into the cytosol with caspase activation, and release of apoptosis-inducing factor (AIF) into the nucleus resulting in nuclear fragmentation and cell death. These results provide a mechanistic basis for using SAHA in future clinical trials with double nucleoside analog-busulfan combinations in pretransplant conditioning therapy.

The Role of BCL2 Family of Apoptosis Regulator Proteins in Acute and Chronic Leukemias

The disturbance of apoptosis molecular signaling pathways is involved in carcinogenesis. BCL2 family of proteins is the hallmark of apoptosis regulation. In the last decade, new members of BCL2 gene family were discovered and cloned and were found to be differentially expressed in many types of cancer. BCL2 protein family, through its role in regulation of apoptotic pathways, is possibly related to cancer pathophysiology and resistance to conventional chemotherapy. It is well known that leukemias are haematopoietic malignancies characterized by biological diversity, varied cytogenetics, different immunophenotype profiles, and diverse outcome. Current research focuses on the prognostic impact and specific role of these proteins in the pathogenesis of leukemias. The understanding of the molecular pathways that participate in the biology of leukemias may lead to the design of new therapies which may improve patients' survival. In the present paper, we describe current knowledge on the role of BCL2 apoptosis regulator proteins in acute and chronic leukemias.

Small molecule inhibitors of Wnt/beta-catenin/lef-1 signaling induces apoptosis in chronic lymphocytic leukemia cells in vitro and in vivo

BACKGROUND

Lymphoid enhancer factor-1 (lef-1) is overexpressed in B-cell chronic lymphocytic leukemia (CLL) when compared with normal B cells and transcribes several genes implicated in the pathogenesis of CLL. We therefore hypothesize that antagonism of lef-1 might lead to killing of CLL cells. We used two small molecule inhibitors of Wnt/beta-catenin/lef-1 signaling (CGP049090 and PKF115-584) to test our hypothesis.

DESIGN AND METHODS

Enriched CLL cells and healthy B cells were used in this study. Small interfering RNA (siRNA)-mediated knockdown of lef-1 in primary CLL cells was done using nucleofection, and 50% lethal concentration (LC(50)) of two small molecules was assessed using ATP-based cell viability assay. Apoptotic response was investigated in time course experiments with different apoptotic markers. Specificity of the small molecules was demonstrated by coimmunoprecipitation experiments for the lef-1/beta-catenin interaction. In vivo studies were done in JVM-3 subcutaneous xenograft model.

RESULTS

Inhibition of lef-1 by siRNA leads to increased apoptosis of CLL cells and inhibited proliferation of JVM-3 cell lines. The two small molecule inhibitors (CGP049090 and PKF115-584) efficiently kill CLL cells (LC(50)<1 microM), whereas normal B cells were not significantly affected. Coimmunoprecipitation showed a selective disruption of beta-catenin/lef-1 interaction. In vivo studies exhibited tumor inhibition of 69% with CGP049090 and 57% with PKF115-584 when compared with vehicle-treated controls, and the intervention was well tolerated.

CONCLUSIONS

We have demonstrated that targeting lef-1 is a new and selective therapeutic approach in CLL. CGP049090 or PKF115-584 may be attractive compounds for CLL and other malignancies that deserve further (pre)clinical evaluation.

Effective elimination of fludarabine-resistant CLL cells by PEITC through a redox-mediated mechanism

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia, and resistance to fludarabine-based therapies is a major challenge in CLL treatment. Because CLL cells are known to have elevated levels of reactive oxygen species (ROS), we aimed to test a novel ROS-mediated strategy to eliminate fludarabine-resistant CLL cells based on this redox alteration. Using primary CLL cells and normal lymphocytes from patients (n = 58) and healthy subjects (n = 12), we showed that both fludarabine-resistant and -sensitive CLL cells were highly sensitive to beta-phenylethyl isothiocyanate (PEITC) with mean IC(50) values of 5.4 microM and 5.1 microM, respectively. Normal lymphocytes were significantly less sensitive to PEITC (IC(50) = 27 microM, P < .001). CLL cells exhibited intrinsically higher ROS level and lower cellular glutathione, which were shown to be the critical determinants of CLL sensitivity to PEITC. Exposure of CLL cells to PEITC induced severe glutathione depletion, ROS accumulation, and oxidation of mitochondrial cardiolipin leading to massive cell death. Such ROS stress also caused deglutathionylation of MCL1, followed by a rapid degradation of this cell survival molecule. Our study demonstrated that the natural compound PEITC is effective in eliminating fludarabine-resistant CLL cells through a redox-mediated mechanism with low toxicity to normal lymphocytes, and warrants further clinical evaluation.