An Immune Risk Score Predicts Survival of Patients with Acute Myeloid Leukemia Receiving Chemotherapy.

PURPOSE: Prediction models for acute myeloid leukemia (AML) are useful, but have considerable inaccuracy and imprecision. No current model includes covariates related to immune cells in the AML microenvironment. Here, an immune risk score was explored to predict the survival of patients with AML. EXPERIMENTAL DESIGN: We evaluated the predictive accuracy of several in silico algorithms for immune composition in AML based on a reference of multi-parameter flow cytometry. CIBERSORTx was chosen to enumerate immune cells from public datasets and develop an immune risk score for survival in a training cohort using least absolute shrinkage and selection operator Cox regression model. RESULTS: Six flow cytometry-validated immune cell features were informative. The model had high predictive accuracy in the training and four external validation cohorts. Subjects in the training cohort with low scores had prolonged survival compared with subjects with high scores, with 5-year survival rates of 46% versus 19% (P < 0.001). Parallel survival rates in validation cohorts-1, -2, -3, and -4 were 46% versus 6% (P < 0.001), 44% versus 18% (P = 0.041), 44% versus 24% (P = 0.004), and 62% versus 32% (P < 0.001). Gene set enrichment analysis indicated significant enrichment of immune relation pathways in the low-score cohort. In multivariable analyses, high-risk score independently predicted shorter survival with HRs of 1.45 (P = 0.005), 2.12 (P = 0.004), 2.02 (P = 0.034), 1.66 (P = 0.019), and 1.59 (P = 0.001) in the training and validation cohorts, respectively. CONCLUSIONS: Our immune risk score complements current AML prediction models.

Rapidly Progressive, Fata Infection Caused by Bacillus Cereus in a Patient with Acute Lymphoblastic Leukemia.

BACKGROUND: We herein report a fatal case of fulminant septicemia caused by Bacillus cereus in a 49-year-old female with T-cell acute lymphoblastic leukemia receiving chemotherapy. METHODS: Her two blood culture sets were positive for Gram-positive, rod-shaped bacterium. Bacillus cereus was identified by high-throughput MALDI-TOF mass spectrometry and 16S ribosomal RNA gene sequencing. RESULTS: The patient died within 12 hours from the onset of B cereus infection. CONCLUSIONS: Patients with acute leukemia presented with fever and unexplained multiple organ lesions, especially accompanied by CNS symptoms, should alert to the possibility of Bacillus cereus infection.

ATO/ATRA/anthracycline-chemotherapy sequential consolidation achieves long-term efficacy in primary acute promyelocytic leukemia.

The combination of all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3, ATO) has been effective in obtaining high clinical complete remission (CR) rates in acute promyelocytic leukemia (APL), but the long-term efficacy and safety among newly diagnosed APL patients are unclear. In this retrospective study, total 45 newly diagnosed APL patients received ATRA/chemotherapy combination regimen to induce remission. Among them, 43 patients (95.6%) achieved complete remission (CR) after induction therapy, followed by ATO/ATRA/anthracycline-based chemotherapy sequential consolidation treatment with a median follow-up of 55 months. In these patients, the estimated overall survival (OS) and the relapse-free survival (RFS) were 94.4% ± 3.9% and 94.6 ± 3.7%, respectively. The toxicity profile was mild and reversible. No secondary carcinoma was observed. These results demonstrated the high efficacy and minimal toxicity of ATO/ATRA/anthracycline-based chemotherapy sequential consolidation treatment for newly diagnosed APL in long-term follow-up, suggesting a potential frontline therapy for APL.

Inhibition of c-Myc overcomes cytotoxic drug resistance in acute myeloid leukemia cells by promoting differentiation.

Nowadays, drug resistance still represents a major obstacle to successful acute myeloid leukemia (AML) treatment and the underlying mechanism is not fully elucidated. Here, we found that high expression of c-Myc was one of the cytogenetic characteristics in the drug-resistant leukemic cells. c-Myc over-expression in leukemic cells induced resistance to chemotherapeutic drugs, enhanced colony formation capacity and inhibited cell differentiation induced by all-trans retinoic acid (ATRA). Meanwhile, inhibition of c-Myc by shRNA or specific c-Myc inhibitor 10058-F4 rescued the sensitivity to cytotoxic drugs, restrained the colony formation ability and promoted differentiation. RT-PCR and western blotting analysis showed that down-regulation of C/EBPß contributed to the poor differentiation state of leukemic cells induced by c-Myc over-expression. Importantly, over-expression of C/EBPß could reverse c-Myc induced drug resistance. In primary AML cells, the c-Myc expression was negatively correlated with C/EBPß. 10058-F4, displayed anti-proliferative activity and increased cellular differentiation with up-regulation of C/EBPß in primary AML cells. Thus, our study indicated that c-Myc could be a novel target to overcome drug resistance, providing a new approach in AML therapy.

Acute pleural and pericardial effusion induced by chemotherapy in treating chronic myelocytic leukemia.

BACKGROUND: Report of a rare and serious complication of chemotherapy with daunorubicin and cytarabine (DA regimen). METHODS: We report a special case of a patient diagnosed chronic myeloid leukemia (CML) with accelerated phase, who simultaneously suffered from acute pleural and pericardial effusion while receiving chemotherapeutic treatment with DA regimen. RESULTS: Following treatment with DA regimen, the patient had the symptoms of chest distress and shortness of breath, followed by respiratory failure and pericardial tamponade. The patient's condition was improved when treated with the puncturation through the pericardium and pleural cavity, coupled with glucocorticosteroid treatment. CONCLUSIONS: Physicians should be made aware of the potential for emergency pleural and pericardial effusion caused by daunorubicin and cytarabine in order to accurately diagnose and treat these conditions and thereby decrease mortality related to chemotherapy.

Diagnosis of Felty's syndrome, distinguished from hematological neoplasm: A case report.

Felty's syndrome (FS) is characterized by the three conditions of rheumatoid arthritis (RA), neutropenia and splenomegaly, and occurs in few cases of longstanding erosive RA. Discriminating between rare occurrences of autoimmune diseases and malignancies is crucial. The present study describes the case of a 17-year-old female with a two-year history of RA, presenting with an irregular fever, hepatosplenomegaly and enlarged lymph nodes. The antinuclear antibody titer was 1:320, while antibody results for anti-dsDNA, anti-Sm and rheumatoid factor were negative. The clinical presentation was similar to that of lymphoma. However, the fluorodeoxyglucose-positron emission tomography and biopsy examinations of the liver and cervical lymph node did not support the diagnosis of lymphoma. According to the laboratory results and clinical symptoms, the differential diagnosis indicated FS, and immunosuppressive agents were administered. Two weeks later, the patient no longer had a fever, and the transaminase levels were normal, associated with shrinkage of the liver and spleen.

Inhibition of autophagy augments the anticancer activity of α-mangostin in chronic myeloid leukemia cells.

Natural products possessing anticancer activity have been extensively studied because of their low toxicity and potential effect. α-Mangostin, a component of Garcinia mangostana Linn, is a xanthone derivative shown to have antioxidant and antitumor properties. This study was carried out to investigate how to improve the anticancer effects of α-mangostin in chronic myeloid leukemia (CML) cell lines bearing wild-type BCR-ABL or BCR-ABL-T315I mutation. We showed that α-mangostin inhibited cell proliferation of K562, KBM5 and KBM5-T315I cells in both a time- and dose-dependent manner. Significantly, α-mangostin increased the number of apoptotic cells and induced DNA fragmentation compared to control cells. Moreover, α-mangostin selectively inhibited proliferation in primary CML cells, while showing limited lethality in normal hematopoietic progenitors. Additionally, α-mangostin induced not only apoptosis but also autophagy in CML cells. α-Mangostin dramatically increased the expression levels of LC-3II, an autophagosome marker in mammals, and the accumulation of autophagic vacuoles (AVs). Inhibition of autophagy by chloroquine enhanced α-mangostin-mediated cytotoxicity through increasing apoptosis. Taken together, our data suggest that targeting the autophagy pathway is a promising therapeutic strategy to enhance α-mangostin-induced apoptosis. Our study provides an approach for future studies to explore this combination for the treatment of CML.

Antibody-directed double suicide gene therapy targeting of MUC1- positive leukemia cells in vitro and in vivo.

Our aim was to specifically transfer the cytosine deaminase (CD) and thymidine kinase (TK) genes into mucin 1 (MUC1)-positive leukemia cells by anti-MUC1 antibody directed infection of replication-defective lentivirus and to evaluate the targeted cytotoxicity of double suicide genes to leukemia. The target gene vector (containing CD and TK) and envelope (containing GFP and anti-MUC1) and packaging plasmids were cotransfected into 293T cells to produce the recombinant lentivirus. Suicide genes in virus-infected leukemia cells (U937, Jurkat, and K562) were detected by western blot. The cytotoxicity and bystander effect in vitro and the therapeutic effect in vivo were detected after treatment with the prodrugs. The results revealed that combined treatment with prodrug 5-fluorocytosine (5-FC) and ganciclovir (GCV) inhibited leukemia cell growth and caused significant bystander effect than treatment with either prodrug alone. TK/GCV treatment alone induced degeneration and cell death while the effect of CD/5-FC alone mainly caused vacuolar degeneration and necrosis. The addictive effects of combinatorial use of GCV and 5-FC mainly induced swelling of the mitochondria followed by necrosis of the leukemia cells. In vivo experiments revealed that both single and combinatorial prodrug treatments could prolong the survival time of leukemic mice. In summary, anti-MUC1 antibody directed lentiviral vector successfully transduced dual suicide genes and exerted targeted cytotoxicity against MUC1 positive leukemia cells. This targeted lentiviral dual suicide gene delivering system provides a promising approach for clinical treatment of leukemia in future.

Diagnosis and treatment of a patient with isolated spinal granulocytic sarcoma: A case report.

A previously healthy 34-year-old female presented with a 5-month history of progressive backache and weakness in the left fingers. Magnetic resonance imaging (MRI) showed soft tissue masses in the spinal canal distributed along the nerve course. The patient's baseline laboratory data were normal. Surgical intervention was performed and histological examination identified isolated spinal granulocytic sarcoma (GS). A bone marrow biopsy also presented normal findings. However, the patient developed numbness and pain in the right lower limb two months later. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) showed FDG uptake in the left trapezius muscle, cervix uteri, iliac bone, lymphadenectasis of the pelvic wall and left axillary fossa. Cerebrospinal fluid (CSF) examination allowed a diagnosis of central nervous system leukemia (CNSL). The patient underwent chemotherapy and intrathecal injection, resulting in the elimination of the residual lesion. Correct diagnosis and adequate treatment are essential to achieve optimal results in patients with isolated spinal GS.

Inhibition of extracellular signal-regulated kinase activity by sorafenib increases sensitivity to DNR in K562 cells.

The mitogen-activated protein kinase (MAPK) pathway has a protective function on the management of hematologic malignancies. The aim of this study was to assess whether the induction of MAPK-mediated effects contributes to the therapeutic value of combination sorafenib and daunorubicin (DNR) treatment. Herein, we found that DNR increased phosphorylation of extracellular signal-regulated kinases (ERK1/2) in K562 cells. ERK1/2 activity was blocked by either the mitogen-induced extracellular kinase (MEK) inhibitor U0126 or a multi-kinase inhibitor sorafenib. Of note, sorafenib sensitized K562 to DNR by inhibiting proliferation and inducing apoptosis in a dose-dependent manner which was through blocking the RAF/MEK/ERK pathway. Moreover, K562 cells transfected with a constitutively active MEK2DD plasmid showed increasing IC50 values following DNR treatment compared with control cells. Combination of DNR with MEK inhibitor U0126 synergistically inhibited K562 cell growth. In conclusion, our results indicated that sorafenib sensitized K562 cells to DNR-induced cytotoxicity by downregulating p-ERK1/2 expression. DNR in combination with sorafenib may represent a new and potential therapeutic strategy in treating acute leukemia with high p-ERK1/2 levels.

[Decitabine inhibits cell proliferation and induces apoptosis of all-trans retinoid acid-resistant acute promyelocytic leukemia NB4-R2 cell line].

The aim of this study was to investigate the proliferation-inhibitory and inducing apoptotic effects of decitabine (DAC) on acute promyelocytic leukemia NB4-R2 cells. Cell inhibitory rate was determined by cell proliferation and cytotoxicity assay (WST-1 assay) after NB4-R2 cells were treated with 0.01 - 0.5 µmol/L DAC for 24, 48 and 72 h. Apoptosis of NB4-R2 cells treated with 0.05 - 5 µmol/L DAC for 48 h was detected by flow cytometry with PI staining and AnnexinV/PI staining. Reverse transcription-PCR (RT-PCR) was used to determine the mRNA expression level of MDR1 gene encoding P-glycoprotein (P-gp). The results indicated that DAC (0.01 - 0.5 µmol/L) inhibited the proliferation of NB4-R2 cells in both time- and concentration-dependent manners. The IC(50) of DAC on the viability of NB4-R2 cells after treatment for 48 and 72 h were 0.089 and 0.064 µmol/L respectively. DAC (0.05 - 5 µmol/L) induced NB4-R2 cell apoptosis in dose-dependent manner with down-regulation of MDR 1 gene expression. It is concluded that a low concentration of DAC (< 0.5 µmol/L) inhibits cell proliferation, while higher concentration of DAC (1 or 5 µmol/L) induces apoptosis on NB4-R2 cells, accompanied with reduction of MDR1 levels.

Inhibition of lymphoma cell proliferation by peroxisomal proliferator-activated receptor-γ ligands via Wnt signaling pathway.

Peroxisome proliferator-activated receptor gamma (PPARγ) plays an important role in regulating energy balance, glucose and lipid metabolisms and inflammation. PPARγ also exerts multiple anti-cancer effects including tumor growth and angiogenesis inhibition, induction of cell differentiation, and apoptosis. Perturbed Wnt/ß-catenin signaling likely plays a key role in tumorigenesis and the interaction between PPARγ and the transcriptional regulator ß-catenin maybe important in this process. Phosphorylation of ß-catenin by GSK-3ß inactivates it and suppresses tumor cell proliferation and self-renewal of tumor stem cells. In combination with Frizzled, Wnt suppresses GSK-3ß and causes degradation of ß-catenin and activation of many tumor proliferation factors. In the present study, we investigated the effects of PPARγ agonist rosiglitazone (RGZ) and PPARγ antagonist GW9662 on the growth, mitotic cycle, and apoptosis of human lymphoma cell line, Raji cells. We also studied the influence of PPARγ ligands on the expression of ß-catenin and GSK-3ß in Raji cells to reveal whether Wnt/GSK-3ß/ß-catenin signaling pathways are involved in PPARγ ligands triggered Raji cell apoptosis. Results showed that both RGZ and GW9662 can inhibit the growth of Raji cells by inducing apoptosis and arresting cell cycle; however, there was no correlation between these effects and expression of PPARγ. Both the PPARγ ligands, RGZ and GW9662, appear to reciprocally regulate the mRNA and protein expressions of GSK-3ß, which promotes apoptosis, and of ß-catenin, which blocks apoptosis. These results suggest that PPARγ ligands mediate their effects via Wnt/GSK-3ß/ß-catenin signaling on Raji cell proliferation and survival.

[Sorafenib induces apoptosis of U937 cells via inhibiting WNT signal pathway].

This study was aimed to investigate the effect of multikinase inhibitor sorafenib on the proliferation and apoptosis of U937 cells and its possible mechanism. U937 cells were treated with different concentrations of sorafenib for 48 hours. Cell viability was determined by Cell Counting Kit-8; cell apoptosis and cell ratio in cell cycle were detected by flow cytometry with Annexin V/PI staining and PI staining respectively; expressions of GSK-3ß, ß-catenin and cyclin-D1 were assayed by Western blot. The results showed that the proliferation of U937 cells was inhibited by sorafenib in a dose-dependent manner (p < 0.05). Sorafenib induced cell apoptosis and cell cycle G(1)/G(0) arrest. Compared with results of Western blot before treatment, expression of inactivated GSK-3ß, ß-catenin and Cyclin-D1 down-regulated in a dose-dependent manner after treatment with sorafenib, this same changes were observed after up-regulation of inactivated GSK-3ß by LiCl (p < 0.05). It is concluded that sorafenib inhibits the proliferation of U937 cells and induces cell apoptosis through reducing negative regulation of WNT signal pathway on inactivated GSK-3ß and down-regulating ß-catenin and cyclin-D1 level, which result in U937 cell cycle G(1)/G(0) arrest.

PPARγ agonist suppresses TLR4 expression and TNF-α production in LPS stimulated monocyte leukemia cells.

It has been well established that inflammation plays a critical role in cancer. Chronic inflammation promotes tumorgenesis and metastasis, which suggests that anti-inflammation drugs could act as a tumor suppressor. It is known that the peroxisome proliferator-activated receptor γ (PPARγ) has been implicated in anti-inflammatory responses; however, the anti-tumor effects of PPARγ have not been intensively investigated. In this study, we examined the effects of PPARγ in cancer. We show that the activation of PPARγ by its agonist rosiglitazone (RGZ) reduces cell proliferation rate in inflammatory and tumor-derived U937 cells. Treatment of RGZ suppresses the expression Toll-like receptor 4 (TLR4) and decreases the production of TNF-α in LPS treated U937 cells. This suggests that NF-κB signaling may be involved in anti-tumor effect of RGZ. Our results demonstrate a role of PPARγ in regulation of NF-κB signaling by modulating TLR4 expression and TNF-α production.

[Pro-apoptotic effect of ciglitazone in leukemic HL-60 cells via PPARγ and P38 MAPK signaling pathway].

OBJECTIVE: To investigate the apoptosis-inducing effect of peroxisome proliferator-activated receptor γ (PPARγ) agonist ciglitazone (CGZ) on leukemic HL-60 cells and its mechanisms of action. METHODS: HL-60 cells in vitro culture medium were subject to different concentrations of CGZ (10-50 µmol/L) for 24, 48 and 72 h. MTT assay was used to detect the cell inhibitory rate and agarose gel electrophoresis to observe DNA fragmentation. Flow cytometry (FCM) and Annexin V/PI staining were used to detect CGZ and/or GW9662 (PPARγ antagonist)-induced cell apoptosis. The expression of PPARγ was examined by RT-PCR and Western blotting. The caspase-3 and protein levels in mitogen-activated protein kinase signaling pathways (MAPKs, p-P38, p-ERK and p-JNK) were also detected. RESULTS: CGZ (over 30 µmol/L) could inhibit the growth of HL-60 cells in both time- and dose-dependent manner. After treatment for 72 h, the cell growth inhibitory rate in 50 µmol/L CGZ (84% ± 11%) treated cells was found more higher than that in both 40 µmol/L and 30 µmol/L CGZ treated cells (72% ± 13%, 59% ± 13%, P < 0.01) and a typical DNA ladder was also observed by agarose gel electrophoresis. The expression of PPARγ was gradually up-regulated by CGZ treatment and could be down-regulated partially by PPARγ antagonist GW9662. The results also revealed that CGZ-induced cell apoptosis (49.7%, 72 h) could not be inhibited thoroughly by GW9662 (36.2%, control:3.2%). It indicated that the CGZ-induced cell apoptosis was partially PPARγ-independent. Western blotting showed a cleavage of caspase-3 zymogen protein and up-regulation of p-P38 protein. Thus it indicated that the activations of caspase-3 and P38 MAPK were involved in CGZ-induced cell apoptosis. CONCLUSION: CGZ inhibits cell growth by induction of cell apoptosis in HL-60 cells via PPARγ dependent and independent signaling pathways. The activations of caspase-3 and P38 MAPK may be one of the important mechanisms in CGZ in treated HL-60 cells.

Down-regulation of telomerase activity and activation of caspase-3 are responsible for Tanshinone I-induced apoptosis in monocyte leukemia cells in vitro.

Tanshinone I (Tan-I) is a diterpene quinone extracted from the traditional herbal medicine Salvia miltiorrhiza Bunge. Recently, Tan-I has been reported to have anti-tumor effects. In this study, we investigated the growth inhibition and apoptosis inducing effects of Tan-I on three kinds of monocytic leukemia cells (U937, THP-1 and SHI 1). Cell viability was measured by MTT assay. Cell apoptosis was assessed by flow cytometry (FCM) and AnnexinV/PI staining. Reverse transcriptase polymerase chain reaction (RT-PCR) and PCR-enzyme-linked immunosorbent assay (ELISA) were used to detect human telomerase reverse transcriptase (hTERT) expression and telomerase activity before and after apoptosis. The activity of caspase-3 was determined by Caspase colorimetric assay kit and Western blot analysis. Expression of the anti-apoptotic gene Survivin was assayed by Western blot and Real-time RT-PCR using the ABI PRISM 7500 Sequence Detection System. The results revealed that Tan-I could inhibit the growth of these three kinds of leukemia cells and cause apoptosis in a time- and dose-dependent manner. After treatment by Tan-I for 48 h, Western blotting showed cleavage of the caspase-3 zymogen protein with the appearance of its 17-kD subunit, and a 89-kD cleavage product of poly (ADP-ribose) polymerase (PARP), a known substrate of caspase-3, was also found clearly. The expression of hTERT mRNA as well as activity of telomerase were decreased concurrently in a dose-dependent manner. Moreover, Real-time RT-PCR and Western blot revealed a significant down-regulation of Survivin. We therefore conclude that the induction of apoptosis by Tan-I in monocytic leukemia U937 THP-1 and SHI 1 cells is highly correlated with activation of caspase-3 and decreasing of hTERT mRNA expression and telomerase activity as well as down-regulation of Survivin expression. To our knowledge, this is the first report about the effects of Tan-I on monocytic leukemia cells.

[Effect of sorafenib combined with daunorubicin on K562 cell line].

The aim of this study was to investigate the effect of sorafenib combined with daunorubicin on leukemic k562 cell line. The inhibitory effect of sorafenib alone and its combination with daunorubicin on K562 cell proliferation was detected by MTT method; the synergistic effect was measured by CDI (coefficient of drug interaction); the apoptosis of K562 cells was observed by flow cytometry with Hoechst 33258 staining. The results showed that the sorafenib alone or its combination with daunorubicin could significantly inhibit K562 cell proliferation and the combination of both drugs displayed synergistic effect on K562 cells, meanwhile the apoptotic cells increased. It is concluded that the combination of sorafenib and daunorubicin has a obviously synergistic inhibitory effect on leukemic cell line K562.

Inactivation of PI3k/Akt signaling pathway and activation of caspase-3 are involved in tanshinone I-induced apoptosis in myeloid leukemia cells in vitro.

Tanshinone I (Tan I), a diterpene quinone extracted from herbal medicine Salvia miltiorrhiza Bunge, has recently been reported to have antitumor effects. As the mechanism of its proapoptotic effects on human myeloid leukemia cells has not been extensively studied, we performed an in-depth evaluation of the effects of Tan I on apoptosis in human K562 and HL-60 cells. The results revealed that Tan I could inhibit the growth of leukemia cells and cause apoptosis in a time- and dose-dependent manner. Apoptosis was observed clearly by flow cytometry and Hoechst 33258 staining, as well as DNA fragmentation analysis. After treatment by Tan I for 48 h, the percentage of disruption of mitochondrial membrane potential (Δψm) was increased in a dose-dependent manner. Western blotting analysis demonstrated the cleavage of caspase-3 zymogen protein and a dose-dependent cleavage of poly-(ADP-ribose) polymerase. Tan I-induced apoptosis was accompanied by a significant decrease in survivin and an increase in Bax. Moreover, Tan I treatment remarkably downregulated the phosphorylation of both P85/PI3K and Akt in a time-dependent manner, and the PI3K/AKT-specific inhibitor (LY294002) mimicked the apoptosis-inducing effects of Tan I. We therefore conclude that the induction of apoptosis by Tan I in these leukemia cells is mainly related to the disruption of Δψm, the upregulation of Bax expression, and the activation of caspase-3. This process is highly correlated with the inactivation of PI3K/Akt/survivin signaling pathways. The results indicate that Tan I may serve as an effective adjunctive reagent in the treatment of leukemia.

Activation of peroxisome proliferator-activated receptor-gamma induces apoptosis on acute promyelocytic leukemia cells via downregulation of XIAP.

In the present study we investigated the in vitro apoptosis inducing effects of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand ciglitazone (CGZ) on acute promyelocytic leukemia (APL) NB4 cells and its mechanisms of action. The results revealed that CGZ (10-50 micromol/l) inhibited the growth of leukemia NB4 cells and caused apoptosis in a time- and dose-dependent manner. Apoptosis was observed clearly by flow cytometry (FCM) and DNA fragmentation analysis. After treatment by CGZ for 48 h, the percentage of disruption of mitochondrial membrane potential (Deltapsim) was increased in a dose-dependent manner. Western blotting demonstrated the cleavage of caspase-3 zymogen protein and a time-dependent cleavage of poly (ADP-ribose) polymerase (PARP). The results also demonstrated that PPAR-gamma expression was increased concomitantly when apoptosis occurred, and that CGZ-induced apoptosis was inhibited by the PPAR-gamma antagonist GW9662, suggesting a PPAR-gamma dependent signaling pathway in CZG-induced cell death. Moreover, CGZ treatment remarkably downregulated the expression of the X-linked inhibitor of apoptosis protein (XIAP), which was inhibited by GW9662. Of note, a small-molecule XIAP antagonist (1396-12) mimicked the effect of CGZ-induced apoptosis via activation of caspase-3, 7 and 9. The apoptosis-inducing effects by CGZ on fresh APL cells were also found to be remarkable by using FCM and Wright's staining observation. Taken together, our results suggest that downregulation of XIAP and activation of capase-3 play an important role in mediating the PPAR-gamma-dependent cell death induced by CGZ in APL cells. These data provide a novel insight into potential therapeutic strategies for treatment of leukemia.

Peroxisome proliferator-activated receptor-gamma agonist rosiglitazone--induced apoptosis in leukemia k562 cells and its mechanisms of action.

This study investigates the ability of a synthetic PPAR-gamma 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.