Caspase-mediated cell death in hematological malignancies: theoretical considerations, methods of assessment, and clinical implications

Nexus Between Immune Responses and Oxidative Stress: The Role of Dietary Hydrolyzed Lignin in ex vivo Bovine Peripheral Blood Mononuclear Cell Response

The control of immune responses is particularly critical when an increase of oxidative stress occurs, causing an impairment of immune cell response and a condition of systemic inflammation, named oxinflammation. Nutritional strategies based on the use in the diet of phytochemicals extracted from plants, rich in antioxidants, could help restore the antioxidant/oxidant balance and obtain a modulation of immune response. Lignin represents a valuable resource of phenolic compounds, which are characterized by a corroborated antioxidant effect. To date, there are no studies reporting the effects of lignin in the diet on immune responses and oxidative stress in ruminants. The objective of the present experiment was the evaluation of the dietary inclusion of Pinus taeda hydrolyzed lignin on the ex vivo immune responses and oxidative stress biomarkers by peripheral blood mononuclear cells (PBMCs) isolated from beef steers. In order to test the effect during oxidative stress exposition, cells were treated with hydrogen peroxide (H₂O₂). The proliferation test and the viability assay were carried out on cells, whereas, on supernatants, the cytokine profile and the oxidative stress biomarkers were evaluated. The dietary inclusion with P. taeda hydrolyzed lignin resulted in cytoprotection after H₂O₂ exposition, increasing the number of viable monocytes and decreasing the reactive oxygen/nitrogen species production in supernatants. The cytokine profile indicated the modulatory role of hydrolyzed lignin on immune response, with a concomitant decrease of TNF-α and increase of IL-8 production, which are strictly connected with monocyte activation and antioxidant response pathway. These results demonstrated that hydrolyzed lignin may provide a modulation of oxidative stress and inflammatory response in PBMCs; thus, the P. taeda hydrolyzed lignin could be suggested as an innovative phytochemical in ruminant feed.

Apoptosis and beyond: cytometry in studies of programmed cell death

A cell undergoing apoptosis demonstrates multitude of characteristic morphological and biochemical features, which vary depending on the inducer of apoptosis, cell type and the "time window" at which the process of apoptosis is observed. Because the gross majority of apoptotic hallmarks can be revealed by flow and image cytometry, the cytometric methods become a technology of choice in diverse studies of cellular demise. Variety of cytometric methods designed to identify apoptotic cells, detect particular events of apoptosis and probe mechanisms associated with this mode of cell death have been developed during the past two decades. In the present review, we outline commonly used methods that are based on the assessment of mitochondrial transmembrane potential, activation of caspases, DNA fragmentation, and plasma membrane alterations. We also present novel developments in the field such as the use of cyanine SYTO and TO-PRO family of probes. Strategies of selecting the optimal multiparameter approaches, as well as potential difficulties in the experimental procedures, are thoroughly summarized.

Cytotoxic effect of R-etodolac (SDX-101) in combination with purine analogs or monoclonal antibodies on ex vivo B-cell chronic lymphocytic leukemia cells

R-etodolac (SDX-101) is an isoform of the non-steroidal anti-inflammatory drug, etodolac, and is currently being tested in phase II clinical trials for the treatment of refractory B-cell chronic lymphocytic leukemia (B-CLL). The aim of this study was to evaluate the cytotoxicity of SDX-101 combined with agents proven to be effective as first-line treatment of B-CLL: the purine nucleoside analogs, fludarabine (FA) and cladribine (2-CdA), and the monoclonal antibodies, anti-CD52 (alemtuzumab; ALT) and anti-CD20 (rituximab; RIT). The cytotoxicity and specific pro-apoptotic effects of the study drugs on B-CLL cells were assessed in vitro in samples from overall 37 untreated patients. The combinations of SDX-101 with 2-CdA, FA or RIT exerted additive effects in B-CLL cells, with the following combination indices (CI): 0.89 for SDX-101 + 2-CdA, 0.95 for SDX-101 + RIT, and 1.17 for SDX-101 + FA. The main mechanism of these interactions was caspase-mediated apoptosis. The SDX-101 plus ALT combination resulted in only sub-additive cytotoxicity (CI = 1.25). In conclusion, these data obtained in vitro indicate that addition of 2-CdA, FA or RIT to SDX-101 significantly enhance cytotoxicity in B-CLL cells.

Peroxisome Proliferator-Activated Receptor-γ Agonist Rosiglitazone– Induced Apoptosis in Leukemia K562 Cells and Its Mechanisms of Action

This study investigates the ability of a synthetic PPAR-γ agonist, rosiglitazone (RGZ), to induce apoptosis in leukemia K562 cells. The results revealed that RGZ (>40 mmol/L) inhibits the growth of K562 cells and causes apoptosis in a time and dose-dependent manner. Apoptosis is observed clearly by Hoechst 33258 staining. Western blotting analysis demonstrates the cleavage of caspase-3 zymogen protein with the appearance of its 17-kD subunit and a dose-dependent cleavage of poly (ADP-ribose) polymerase. Furthermore, RGZ treatment down-regulates anti-apoptotic protein Bcl-2 and up-regulates pro-apoptotic protein Bax in a dosedependent manner after the cells are treated for 48 hours. Telomerase activity is decreased concurrently in a dosedependent manner. We therefore conclude that RGZ induces apoptosis in K562 cells in vitro, and that RGZ-induced apoptosis in K562 cells is highly correlated with activation of caspase-3, decreasing telomerase activity, down-regulation of the anti-apoptotic protein Bcl-2, and up-regulation of the pro-apoptotic protein Bax.

Downregulation of cyclooxygenase-2 expression and activation of caspase-3 are involved in peroxisome proliferator-activated receptor-gamma agonists induced apoptosis in human monocyte leukemia cells in vitro

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a transcription factor important in fat metabolism and PPAR-gamma agonists were recently demonstrated to affect proliferation, differentiation, and apoptosis of different cell types. In the present study, two PPAR-gamma agonists, 15-deoxy-delta (12,14)-prostaglandin J2 (15d-PGJ2) and a synthetic PPAR-gamma agonist troglitazone (TGZ), were used to investigate activated PPAR-gamma-induced apoptosis on human monocyte leukemia U937 and Mono Mac 6 cells in vitro. The results showed that both U937 and Mono Mac 6 cells demonstrated constitutive activation of COX-2 expression; treatment by 15d-PGJ2 and TGZ could induce apoptosis remarkably in human monocyte leukemia cells by disruption of mitochondrial membrane potential, activation of caspase-3, and causing cleavage of the caspase substrate poly (ADP-ribose) polymerase (PARP). Further studies revealed that treatment by both 15d-PGJ2 and TGZ remarkably downregulated COX-2 expression in these two kind of monocyte leukemia cells as measured by reverse transcriptase PCR (RT-PCR) and Western blot. Furthermore, the expression of Bcl-2 and Bcl-Xl and Mcl-1 was downregulated while Bax expression was upregulated concurrently after the cells were treated by these two agonists, and no variations were found in other Bcl-2 family members such as Bak, Bid, and Bad. Taken together, our results demonstrate for the first time that downregulation of cyclooxygenase-2 expression, disruption of mitochondrial membrane potential, activation of caspase-3, downregulation of Bcl-2, Bcl-Xl, and Mcl-1, and upregulation of Bax are involved in PPAR-gamma agonists-induced apoptosis in these two human monocyte leukemia cells.

Induction of apoptosis and inhibition of cell adhesive and invasive effects by tanshinone IIA in acute promyelocytic leukemia cells in vitro

Tanshinone IIA, a diterpene quinone extracted from the traditional herbal medicine, Salvia miltiorrhiza Bunge, is used widely and successfully in clinics in China for treating inflammatory diseases. Recently tanshinone IIA has been reported to have apoptosis inducing effects on a large variety of cancer cells. In this study, the anti-proliferation and apoptosis inducing effects of tanshinone IIA as well as its influence on cell adhesion to and invasion through the extracellular matrix (ECM) on acute promyelocytic leukemia (APL) NB4 cells in vitro were studied. Cell proliferation was assessed by MTT assay, cell apoptosis was observed by Hoechst 33258 staining and flow cytometry (FCM); The variation of caspase-3 and apoptotic related genes were assayed by Western blotting, cell mitochondrial membrane potential as well as cell adhesive and invasive effects were also investigated by using standard methods. The results showed that tanshinone IIA exhibited induction of apoptosis by activation of caspase-3, downregulation of anti-apoptotic protein bcl-2 and bcl-xl and upregulation of pro-apoptotic protein bax, as well as disruption of the mitochondrial membrane potential. Furthermore, treatment by tanshinone IIA could reduce cell adhesion to and invasion through ECM in leukemia NB4 cells. These data provide a potential mechanism for tanshinone IIA-induced apoptosis and cell growth inhibition in leukemia NB4 cells, suggesting that tanshinone IIA may serve as an effective adjunctive reagent for the treatment of APL.

Ponicidin, an ent-kaurane diterpenoid derived from a constituent of the herbal supplement PC-SPES, Rabdosia rubescens, induces apoptosis by activation of caspase-3 and mitochondrial events in lung cancer cells in vitro

Ponicidin, an ent-kaurane diterpenoid derived from a constituent of the herbal supplement PC-SPES, Rabdosia rubescens, is recently reported to have anti-tumor effects on a large variety of cancers. In this study, we demonstrate that ponicidin exhibits cytotoxicity, induces apoptosis, disrupts the mitochondrial membrane potential, and triggers the activation of caspase-3, -8 and -9 in lung cancer A549 and GLC-82 cells. Ponicidin treatment of lung cancer cells caused downregulation of anti-apoptotic protein Bcl-2 and survivin as well as upregulaton of pro-apoptotic protein Bax in a time dependent manner when apoptosis ocurred. Ponicidin induced activation of caspase-3 can be blocked by a caspase-3-specific inhibitor z-DEVD-FMK Furthermore, the caspase-8-specific inhibitor z-IETD-FMK could block the ponicidin-induced activation of caspase-3, PARP cleavage, and prevented the release of cytochrome c from mitochondria into the cytoplasm. This indicate that activated caspase-8 initiates the release of cytochrome c during ponicidin-induced apoptosis. We therefore conclude that ponicidin has significant apoptosis-inducing effects by activation of caspase-3 -8, and -9 as well as downregulation of anti-apoptotic protein Bcl-2, survivin and upregulation of pro-apoptotic protein Bax, with caspase-8 acting as an upstream activator. The data offer a potential mechanism for ponicidin-induced apoptosis in lung cancer cells, suggesting that ponicidin may severve as an effective reagent for the treatment of lung cancer, and that in vivo anti-cancer effects as well as its potential clinical effectiveness need further investigation.

Antiproliferation effects of oridonin on HPB-ALL cells and its mechanisms of action

Oridonin, an ent-kaurane diterpenoid derived from the herbal Rabdosia rubescens, has been recently reported to have antitumor effects on a large variety of cancer cells. The present study was undertaken to investigate the in vitro antiproliferation and apoptosis inducing effects of oridonin on HPB-ALL cell lines and its mechanisms of action. HPB-ALL cells in culture medium in vitro were treated with different concentrations of oridonin (16-56 micromol/L). MTT assay was used to detect the cell growth inhibitory rate, and the cell viability was assessed by the trypan blue dye-exclusion method. Cell apoptosis and the mitochondrial membrane potential (delta psi m) were investigated by flow cytometry (FCM), Hoechst 33258 staining, and DNA fragmentation analysis. The expression of caspase-3 and different apoptosis modulators, including Fas and Bcl-2 family members, was analyzed by Western blotting. The results revealed that oridonin could significantly inhibit the growth of HPB-ALL cells and cause apoptosis, and the suppression was both time- and dose-dependent. After treatment with oridonin for 48 hr, the percentage of disruption of delta psi m gradually increased in a dose-dependent manner along with marked changes of cell apoptosis, and necrotic cells increased remarkably after the cells were treated with oridonin for 72 hr; Western blotting showed cleavage of the caspase-3 zymogen protein (32 kDa) with the appearance of its 20-kDa subunit when apoptosis occurred; expression of Bcl-2 and Bcl-XL was downregulated remarkably while expression of Bax and Bid was upregulated concurrently after the cells were treated with oridonin for 24 hr. Of note, the expressions of Fas and other Bcl-2 family members including Bak and Bad remained constant before and after apoptosis occurred. We therefore conclude that oridonin has significant antiproliferation effects on HPB-ALL cells by induction of apoptosis as well as directly causing cell necrosis and that oridonin-induced apoptosis on HPB-ALL cells is mainly related to the disruption of delta psi m and activation of caspase-3 as well as downregulation of anti-apoptotic protein Bcl-2, Bcl-XL, and upregulation of pro-apoptotic proteins Bax and Bid. The results indicate that oridonin may serve as a potential antileukemia reagent.

A probable role for trail-induced apoptosis in the pathogenesis of marrow failure. Implications from an in vitro model and from marrow of aplastic anemia patients

Aplastic anemia (AA) is a syndrome of hematopoietic failure involving increased apoptosis of stem cells. In order to investigate the molecular mechanisms participated in the process of marrow failure, we created an in vitro model of hematopoietic cell suppression, by continuous addition of TNF-alpha and IFN-gamma in an vitro long-term bone marrow culture system. An up-regulation of Fas expression was observed in CD34+ cells in cytokine treated cultures, compared to controls. This was accompanied by significant TRAIL and decreased caspase 3 mRNA expression, whereas the expression of Bcl-2 family members was low (Bcl-xl) or absent (Bcl-2, Bax). The expression of these apoptotic genes was also investigated in aplastic anemia patients. Apart from Fas mRNA expression in total marrow and/or CD34+ cells, TRAIL mRNA expression was found only in CD34+ cells in active disease while in total marrow cell compartment this remains a constant finding even in patients in remission. The above data are in agreement with previous studies proposing a major role for the extrinsic apoptosis pathway in the pathogenesis of aplastic anemia and additionally introduce TRAIL as a probable important molecule in the process.

Apoptotic effect of oridonin on NB4 cells and its mechanism

The anti-proliferation effects of oridonin on acute promyelocytic leukemia (APL) cells and its mechanisms were studied in vitro. NB4 cells as well as fresh leukemia cells obtained from APL patients in culture medium were treated with different concentrations of oridonin. Cell growth inhibition, apoptosis and related pathways were assessed by MTT assay as well as flow cytometry (FCM) and western blot analysis. The data revealed that oridonin (over 16 micromol/L) could inhibit the growth of NB4 cells by induction of apoptosis. Marked changes of cell apoptosis were observed very clearly by using electron microscopy and DNA fragmentation analysis after the cells exposed to oridonin for 48 h; Western blotting showed cleavage of the caspase-3 zymogen protein (32-kDa) with the appearance of its 20-kDa subunit as well as a cleaved 89-kDa fragment of 116-kDa PARP when apoptosis occurred. The expression of Bcl-2 was down-regulated remarkably accompanied by the disruption of the mitochondrial membrane potential (delta(psi)m). The anti-proliferative and apoptosis-inducing effects by oridonin in fresh APL cells were also found remarkably using Trypan Blue dye exclusion method and Wright's staining. We concluded that oridoning has significant anti-proliferative and apoptosis-inducing effects on NB4 cells by activation of caspase-3 and cleavage of PARP as well as by down regulation of Bcl-2 and disruption of the delta(psi)m. Furthermore, oridonin demonstrated apparent cell growth inhibition effects on fresh APL cells in vitro. The results indicated that oridonin may serve as a potential anti-leukemia reagent.

Proapoptotic activity of alemtuzumab alone and in combination with rituximab or purine nucleoside analogues in chronic lymphocytic leukemia cells

Proapoptotic activity of anti-CD52 monoclonal antibody, alemtuzumab (ALT) as well as ALT-affected apoptosis-regulatory mechanisms were assessed in tumor cells from 36 patients with chronic lymphocytic leukemia (CLL). Cells were treated in vitro for 24-48 h with ALT alone or in combination with rituximab (RTX), or purine nucleoside analogues (PNA), fludarabine and cladribine. Moreover, eight ALT-treated patients were examined in vivo. In 22/36 patients with the pre-treatment overexpression of Bax, Bak and Bid proteins, ALT induced a distinct (more than 50% from the baseline) increase in the incidence of apoptosis after 24 h of in vitro treatment. ALT-attributed CLL cell apoptosis was also detected after 24 h from in vivo ALT administration, with significantly downregulated Bcl-2 (P = 0.012) and Mcl-1 (P = 0.031). ALT combined with PNA or RTX exerted significantly higher proapoptotic effect in vitro than single agents, downregulating FLIP and Bcl-2 (ALT + PNA) or significantly increasing Bax expression (ALT + RTX; P = 0.007). In conclusion, the evidence of apoptotic CLL cells death in response to ALT, with deregulation of intrinsic apoptotic pathway, is presented. ALT and PNA or RTX trigger complementary changes in expression of proteins regulating cell propensity to undergo apoptosis, what provides molecular rationale for combining ALT with those agents.

Alemtuzumab in the Treatment of Chronic Lymphocytic Leukemia

Alemtuzumab is a humanized therapeutic monoclonal antibody (MAb) that recognizes the CD52 antigen, expressed on normal and neoplastic lymphocytes, monocytes, and natural killer cells. In 2001, alemtuzumab was approved in the US and Europe to treat B-cell chronic lymphocytic leukemia (CLL) that had been treated previously with alkylating agents and was refractory to fludarabine. In heavily pretreated patients this MAb is able to produce response rates of about 40%, and in symptomatic, previously untreated patients response rates of more than 80% can be achieved. Alemtuzumab can also be used in patients with CLL as a preparative regimen for stem cell transplantation (SCT) and to prevent graft versus host disease. Moreover its in vivo use before or after SCT may also potentially result in depletion of residual leukemia cells, especially in the autologous setting. Adverse events associated with alemtuzumab include acute first-dose reaction, hematologic toxicity, and infectious complications. Usually they are predictable, manageable, and acceptable in the context of CLL. However, in a significant percentage of patients, cytomegalovirus reactivation occurs during alemtuzumab therapy, and routine weekly monitoring with the polymerase chain reaction methodology is indicated. Moreover, antiviral and antibacterial prophylaxis is mandatory.