De novo pyrimidine biosynthetic complexes support cancer cell proliferation and ferroptosis defence.

De novo pyrimidine biosynthesis is achieved by cytosolic carbamoyl-phosphate synthetase II, aspartate transcarbamylase and dihydroorotase (CAD) and uridine 5'-monophosphate synthase (UMPS), and mitochondrial dihydroorotate dehydrogenase (DHODH). However, how these enzymes are orchestrated remains enigmatical. Here we show that cytosolic glutamate oxaloacetate transaminase 1 clusters with CAD and UMPS, and this complex then connects with DHODH, which is mediated by the mitochondrial outer membrane protein voltage-dependent anion-selective channel protein 3. Therefore, these proteins form a multi-enzyme complex, named 'pyrimidinosome', involving AMP-activated protein kinase (AMPK) as a regulator. Activated AMPK dissociates from the complex to enhance pyrimidinosome assembly but inactivated UMPS, which promotes DHODH-mediated ferroptosis defence. Meanwhile, cancer cells with lower expression of AMPK are more reliant on pyrimidinosome-mediated UMP biosynthesis and more vulnerable to its inhibition. Our findings reveal the role of pyrimidinosome in regulating pyrimidine flux and ferroptosis, and suggest a pharmaceutical strategy of targeting pyrimidinosome in cancer treatment.

Matrine, a potential c-Myc inhibitor, suppresses ribosome biogenesis and nucleotide metabolism in myeloid leukemia.

Previous studies have shown that matrine, a natural compound extracted from the herb Sophora flavescens, has a good anti-leukemia effect, but its key target and mechanism remains unclear. Here, we found that only c-Myc could respond rapidly to matrine treatment in three myeloid leukemia cell lines, and matrine inhibited both transcription and translation of c-Myc. Ribosome biogenesis and nucleotide metabolism, the key downstream of c-Myc, were significantly suppressed after matrine treatment. Therefore, our results confirmed that matrine is a special c-Myc inhibitor which suppresses ribosome biogenesis and nucleotide metabolism by inhibiting c-Myc in myeloid leukemia. This study provides scientific basis for the development of matrine derivatives to c-Myc-driven cancers.

Identification of purine biosynthesis as an NADH-sensing pathway to mediate energy stress.

An enhanced NADH/NAD+ ratio, termed reductive stress, is associated with many diseases. However, whether a downstream sensing pathway exists to mediate pathogenic outcomes remains unclear. Here, we generate a soluble pyridine nucleotide transhydrogenase from Escherichia coli (EcSTH), which can elevate the NADH/NAD+ ratio and meantime reduce the NADPH/NADP+ ratio. Additionally, we fuse EcSTH with previously described LbNOX (a water-forming NADH oxidase from Lactobacillus brevis) to resume the NADH/NAD+ ratio. With these tools and by using genome-wide CRISPR/Cas9 library screens and metabolic profiling in mammalian cells, we find that accumulated NADH deregulates PRPS2 (Ribose-phosphate pyrophosphokinase 2)-mediated downstream purine biosynthesis to provoke massive energy consumption, and therefore, the induction of energy stress. Blocking purine biosynthesis prevents NADH accumulation-associated cell death in vitro and tissue injury in vivo. These results underscore the pathophysiological role of deregulated purine biosynthesis in NADH accumulation-associated disorders and demonstrate the utility of EcSTH in manipulating NADH/NAD+ and NADPH/NADP+.

Compound 968 reverses adriamycin resistance in breast cancer MCF-7ADR cells via inhibiting P-glycoprotein function independently of glutaminase.

Adriamycin (ADR) is a chemotherapeutic drug widely utilized to treat multiple types of cancers; however, the clinical efficacy of ADR is compromised due to the development of drug resistance in patients. The combination of drugs with ADR may provide a better therapeutic regimen to overcome this obstacle. Glutaminase (GLS) has been explored as a therapeutic cancer target, and its inhibition also results in increased sensitivity of tumor cells to chemotherapeutic agents. This study aimed to investigate whether GLS inhibition could reverse ADR resistance. We treated the ADR-resistant MCF-7 (MCF-7ADR) cells with a GLS inhibitor, compound 968 or CB-839, in combination with ADR. We found that compound 968, rather than CB-839, together with ADR synergistically inhibited the cell viability. These results indicated that compound 968 reversed ADR resistance in MCF-7ADR cells independently of GLS. Moreover, we modified the structure of compound 968 and finally obtained a compound 968 derivative, SY-1320, which was more potent than compound 968 in eliminating the drug resistance in MCF-7ADR cells. Furthermore, using drug affinity responsive target stability and streptavidin-biotin immunoprecipitation assays, we demonstrated that SY-1320 could specifically target P-glycoprotein (P-gp) and increase ADR accumulation through inhibition of P-gp, thereby resulting in cell death in MCF-7ADR cells. Together, our findings indicate that compound 968 or SY-1320 might be a promising drug for new combination chemotherapy in breast cancer to overcome the drug resistance.

Morinda citrifolia (Noni) Juice Suppresses A549 Human Lung Cancer Cells via Inhibiting AKT/Nuclear Factor-κ B Signaling Pathway.

OBJECTIVE: To study the mechanism of the anti-tumor effect of Morinda citrifolia (noni). METHODS: The influences of noni juice on cell proliferation, apoptosis, invasion, migration and the activity of AKT/nuclear factor- κ B (NF- κ B) signaling pathway in A549 human lung cancer cells were detected by MTT, cell counting kit-8, colony formation, Annexin V/PI double labeling, transwell, scratch test and immunoblotting assay, respectively. A549 cells were inoculated into the right axilla of nude mice, followed by noni juice treatment. The body weight of the nude mice was weighed, and the tumor volume and weight were measured. Cell proliferation and expression of apoptosis-related proteins were measured by immunohistochemistry, and the activity of NF- κ B signaling pathway was measured by immunoblotting. RESULTS: The in vitro studies showed that noni juice inhibited the A549 cells proliferation, migration and invasion. Noni juice also promoted cells apoptosis in A549 cells. Immunoblotting assay showed that the phosphorylation level of AKT, p50, and STAT3 proteins was inhibited to different extents after noni juice treatment. The in vivo studies showed that noni juice effectively suppressed tumor formation of A549 cells in nude mice. Noni juice treatment inhibited the expression of Ki67, PCNA, and Bcl-2 protein in the tumor; while promoted the expression of caspase-3 protein. Additionally, we also found that noni juice treatment could restrain the activity of AKT/NF- κ B signaling pathway in the tumor tissue. CONCLUSION: Noni juice inhibited the proliferation of A549 lung cancer cells, induced apoptosis, and inhibited cell invasion and migration via regulating AKT/NF- κ B signaling pathway.

Rapid mycoplasma culture for the early diagnosis of Mycoplasma pneumoniae infection.

Early diagnosis of Mycoplasma pneumoniae (Mp) plays a pivotal role in its management. We evaluated the role of rapid culture method in early diagnosis of Mp infection and discussed the potential impact factors. A total of 2,600 patients with acute respiratory infection were included, and their pharyngeal swab samples were prepared for Mp rapid culture based on selective Mp fluid culture medium. The clinical contributing factors related to Mp infection were also explored. The positive rate of Mp culture in females was 41.75%, which was higher than that for males (37.63%). Mp infections were incidental to the children and elderly. The positive rates of Mp culture were higher in children aged 3-5 years and adults older than 70 years (54.05 and 31.48%, respectively), compared with other ages. In addition, Mp infection frequently occurred in winter (December-February) and spring (March-May), with significantly higher positive rates of Mp culture by 40.02 and 42.89 vs. 32.15 and 33.50% in summer (June-August) and autumn (September-November), respectively. The positive rate of rapid culture for Mp was slightly higher than that by Mp antibody assay, but the diagnostic accordance was well between these two methods (P>0.05). Furthermore, clinical common symptoms of respiratory tract infection, such as fever, cough, and expectoration, were not found specific in Mp infection, suggesting that they were not independent prognostic predictors for Mp infection. Therefore, rapid culture based on the Mp pathogen detection would have important clinical application for the early diagnosis of Mp infection.

Assessment of CAR- or CD46-dependent adenoviral vector-mediated TRAIL gene therapy in clinical adenocarcinoma lung cancer cells.

Adenoviral vector-mediated transfer of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can be a powerful approach to lung cancer therapy. However, the efficiency of adenoviral vector gene transfer and the sensitivity to TRAIL-induced apoptosis in the context of adenoviral vector gene transfer have yet to be characterized in primary lung cancers. In this study, we investigated the expression of adenoviral receptor CD46 expression in primary lung cancer cells. In contrast to previous reports on enhanced CD46 expression in various types of cancer cells, we show a significantly higher CD46 expression in lung adenocarcinomas compared to lung squamous cell carcinomas. Using Ad5-GFP and Ad5F35-GFP vectors, we demonstrated an improved gene transfer efficiency in primary lung cancer cells by the Ad5F35 vector. The apoptosis induction effect mediated by Ad5-TRAIL and Ad5F35-TRAIL vector gene transfer was compared in cells from 10 lung adenocarcinomas. Of 5 lung cancers in which apoptosis was induced, 2 had an enhanced effect by Ad5F35-TRAIL vector gene transfer compared to Ad5-GFP. Thus, these results indicate a method to identify TRAIL-sensitive primary lung cancers, which will also facilitate the analysis of resistance mechanisms in lung cancers.

Matrine Promotes Human Myeloid Leukemia Cells Apoptosis Through Warburg Effect Mediated by Hexokinase 2.

Matrine, an alkaloid compound isolated from the medicinal plant Sophora flavescens, inhibits many types of cancer proliferation. However, the precise mechanism of the matrine antihuman chronic myeloid leukemia remains unclear. In this study, we showed that matrine significantly inhibited the cell proliferation and induced apoptosis by regulating Warburg effect through controlling hexokinases 2 (HK2) expression in myeloid leukemia cells. Interestingly, matrine inhibited the expression of HK2 mediated by reduction in c-Myc binding to HK2 gene intron and led to downregulation of HK2, which upregulated proapoptotic protein Bad and then induced apoptosis. We further demonstrated that matrine could synergize with lonidamine, an inhibitor of HK2, for the treatment of myeloid leukemia, both in vitro and in vivo. Taken together, our findings reveal that matrine could promote human myeloid leukemia cells apoptosis via regulating Warburg effect by controlling HK2.

[Enhancing effect of matrine on the tumor-inhibition by TIM2 gene-modified hepatocarcinoma H22 cells in mice].

OBJECTIVE: To investigate the effects of matrine on the anti-tumor efficiency of TIM2 gene-modified murine hepatocarcinoma H22 cells. METHODS: A combined eukaryotic expression vector pIRES2-EGFP-TIM2 was constructed and transfected into H22 cells by lipofectamin. The monoclone of positive H22-TIM2 cells and negative control H22-EGFP cells transfected with pIRES2-EGFP vector were selected by G418 pressure and limited dilution method in turn and were inoculated to establish the tumor-bearing mouse model. Next, matrine was administered to the tumor-bearing mice and the inhibitory effect of matrine was determined. RESULTS: The co-expression of EGFP protein and TIM2 gene was detected in H22 cells selected after TIM2 gene transfecion. After subcutaneous injection of H22-TIM2 cells, the rate of tumor formation (41%) was lower than that of H22 cells and H22-EGFP cells injection (92%) in mice. The tumor growth was significantly inhibited in mice vaccinated with H22-TIM2 cells. After the experiment was completed, the volume of tumors in mice of H22-TIM2 group was 31.34 +/- 9.21 mm3, smaller than those in H22-EGFP group (98.25 +/- 25.23)mm3 and H22 cells group (114.08 +/- 36.45)mm3 (P < 0.01). Matrine dramatically enhanced the anti-tumor efficiency of TIM2 gene-modified H22 cells, with the highest tumor inhibitory rate (IR) 90.6% among the H22-TIM2 group, matrine treatment group and H22-EGFP cells combined with matrine treatment group (69.2%, 67.5% and 70.8%, respectively) in the experimental mice. CONCLUSION: The tumorigenesity of H22 cells has been markedly impaired after modification by TIM2 gene. Matrine can enhance its inhibitory effect on tumors of H22-TIM2 cells in vivo. These data indicate importance to further study on the biological role of TIM2 gene in tumor immunity and explore the molecular mechanism of matrine in suppressing of tumor growth.

[Effects of matrine on oncogenicity of H22 cells modified by TIM2 gene in vivo].

OBJECTIVE: To investigate the effects of matrine on the anti-tumor efficiency of H22 murine hepatocarcinoma cell-based vaccine modified by TIM2 gene in vivo. METHOD: The combinant eukaryotic expression vector pIRES2-EGFP-TIM2 was constructed and transfected into H22 cells by lipofectamin. The monoclone of the positive H22-TIM2 cells and negative control H22-EGFP cells were selected by G418 pressure and limited dilution method in turn. The H22 whole-cell-based vaccine were inoculated to establish the tumor-bearing mouse model, and its oncogenicity and immunogenicity were observed in vivo. Then the matrine was administered to the tumor-bearing mice inoculated by H22-TIM2 cells, H22-EGFP cells and H22 cells, and the inhibitory effect of matrine on tumor was studied. RESULT: The co-expression of EGFP protein and TIM2 mRNA were detected in H22-TIM2 cells. The rate of tumor formation in mice injected of H22-TIM2 cells was 41%, lower than that of H22 cells and H22-EGFP cells injection (92%) in mice. The growth of tumor were significantly inhibited vaccinated with H22-TIM2 cells in mice. The inhibitory rate of tumor (IR) was 69.2% in mice of H22-TIM2 group, higher than that of mice treated with matrine and H22 cells injection, the later was 67.5%. Matrine could dramatically strengthen the anti-tumor efficiency of H22 cells modified by TIM2 gene, with the highest tumor inhibitory rate (IR) (90.6%) in all the experimental mice. The spleen index, populations of CD4-positive lymphocytes and the ratio of CD4-positive to CD8-positive lymphocytes of spleen in mice vaccinated of H22-TIM2 cells were obviously higher than those in the other groups. CONCLUSION: The oncogenicity of H22 cells is markedly impaired after modified by TIM2 gene. Matrine can strengthen the inhibitory effect of H22-TIM2 cells on tumor in mice. These data give us important clues to further study the biological role of TIM2 gene in tumor immunity and explore the molecular mechanism of matrine in suppressing tumor.

Matrine inhibits BCR/ABL mediated ERK/MAPK pathway in human leukemia cells.

The BCR/ABL fusion gene and its downstream signaling pathways such as Ras/Raf/MAPK, JAK/STAT3, and PI3K/AKT pathways play important roles in malignant transformation of leukemia, especially chronic myelogenous leukemia (CML). Our previous study showed that matrine, an alkaloid extracted from a Chinese herb radix sophorae, significantly inhibited the proliferation of human CML K562cells, induced cell cycle arrest in G0/G1, and promoted cell apoptosis. In the present study, we investigated the molecular mechanism of matrine in the growth inhibition of leukemia cells using K562 and HL-60 cell lines. RT-PCR and Western blot assay demonstrated that the expression of BCR/ABL in K562 and HL-60 cells was significantly inhibited by matrine treatment. Phosphorylation of MEK1, ERK1/2, and their upstream adaptor molecules Shc and SHP2 were significantly downregulated. The protein and mRNA expression of components of the ERK/MAPK signal pathway, and Bcl-xL, Cyclin D1, and c-Myc, were dramatically reduced. Conversely, the expression of p27, a negative regulator of cell cycle progression, increased after matrine treatment. These results indicated that the inhibition of ERK/MAPK and BCR/ABL signaling pathway was associated with matrine's suppressive effects on the growth of K562 and HL-60 cells. In in vivo study, matrine significantly decreased the mortality rate of tumor-baring mice and suggested that matrine could exert its anti-leukemia effect in vivo.

[Inhibition of tumor growth in tumor-bearing mice treated with matrine].

OBJECTIVE: To investigate the inhibitory effect of matrine on tumor growth in tumor-bearing mice and explore its possible mechanisms of anti-tumor action in vivo. METHODS: Hepatocellular carcinoma cells H(22) were subcutaneously injected into BALB/c mice and matrine was administered to the tumor-bearing mice. The kinetics of tumor formation and tumor growth were measured, tumor growth inhibition rate (IR) was calculated, and tumor tissue samples were taken and examined by light and electron microscopy to assess the inhibitory effects of matrine on tumor growth in the mice. RESULTS: Marked inhibitory effect of matrine on the transplanted hepatocellular carcinoma H(22) was observed in the tumor-bearing mice. The inhibitory rates were 62.5% and 60.7% in the groups treated with high and low dosage of matrine, respectively (P < 0.01 vs. control group). The tumor formation was significantly retarded and tumor growth was inhibited in matrine-treated groups compared with those in control mice. Histopathological examination revealed widespread necrosis with massive accumulation of infiltrating lymphocytes and plasmacytes in the tumors. Numerous apoptotic cells and apoptotic bodies were observed in the tumors under the electron microscope. CONCLUSION: Matrine has marked inhibitory effects on tumor growth in vivo, which is probably related to inhibition of cell division and tumor cell proliferation, directly killing of tumor cells and/or induction of apoptosis and modulation of anti-tumor immune responses.

[Construction of eukaryotic expression vector of unknown KH gene and its effect on cell proliferation].

OBJECTIVE: To construct an eukaryotic expression vector of open reading frame of unknown KH gene (KH-ORF), and investigate its effect on cell proliferation. METHODS: The pCI-neo-KH-ORF expression vector was constructed by DNA recombinant technique and was introduced into COS-7 cells and K562 cells by lipofectactin-mediated DNA transfection. Expression of KH-ORF mRNA was detected by RT-PCR. The effect of KH-ORF on cell cycle of COS-7 cells and K562 cells was evaluated by flow cytometry (FCM). Effect on cell proliferation of COS-7 cells was tested by MTT assay and that on K562 cells was analyzed by growth curves and LDH activity measurement. RESULTS: (1) KH-ORF mRNA was expressed both in COS-7 cells and K562 cells. (2) The cell cycle and cell proliferation of COS-7 cells were unaffected significantly. (3) The proportion of cells in S phase was increased in pCI-neo-KH-ORF-transfected K562 cells; and growth curves and LDH activity indicated enhanced cell proliferation. CONCLUSION: KH gene may be a leukemia gene related to proliferation of K562 cells.

STAT3 signaling pathway is involved in decitabine induced biological phenotype regulation of acute myeloid leukemia cells.

OBJECTIVE: This study aimed to investigate the role of signal transduction and transcriptional activator STAT3 and relevant signaling pathway in the DAC regulated biological phenotype of AML cells. METHODS: The effect of DAC at different concentrations on the proliferation of HL-60 cells was determined. After DAC treatment for 48 h, the killing capability of NK cells against HL-60 cells and the protein expressions of STAT3, JAK1, JAK2, SOCS-1 and SOCS-3 were evaluated. RESULTS: DAC markedly inhibited the proliferation of HL-60 cells. After the treatment of 48 hr with 0.2, 0.5 and 1.0 mol/L DAC, the HL-60 viability was reduced by 25±13%, 39±8% and 50±7% (P<0.01), respectively, and the early apoptosis rate was increased to 24.77±7.5%, 27.1±4.48% and 30.53±3.93%, respectively (control: 3.11±0.12%, P<0.01). DAC up-regulated the expression of MICA/B, ULBP-1 and ULBP-3 in HL-60 cells, and increased the killing activity of NK cells to HL-60 cells. DAC significantly induced the apoptosis of HL-60 cells and up-regulated the expression of NKG2D ligands in a dose dependent manner. Western blot assay showed the protein expression of STAT3, JAK, JAK2, phosphorylated STAT3, phosphorylated JAK1 and phosphorylated JAK2 decreased, while that of SOCS-1 and SOCS-3 increased in HL-60 cells after DAC treatment. CONCLUSION: In HL-60 cells, DAC can markedly inhibit their proliferation and up-regulate the expression of NKG2D ligands, and DAC also increase the cytotoxicity of NK cells to HL-60 cells, which may be related to the STAT3 related signaling pathway.

Matrine increases NKG2D ligand ULBP2 in K562 cells via inhibiting JAK/STAT3 pathway: a potential mechanism underlying the immunotherapy of matrine in leukemia.

PURPOSE: The study aimed to investigate the role of the JAK/STAT3 pathway in the matrine induced ULBP2 expression on the human chronic myelogenous leukemia K562 cells. METHODS: K562 cells were cultured, and the relevant mRNA expressions were detected. RESULTS: Matrine induced the expression of four NKG2D ligands on K562 cells, of which ULBP2 had the highest increase. After treatment with 0.8 mg/mL matrine for 24 h, the mean fluorescence intensity (MFI) of ULBP2 increased. After matrine treatment, the sensitivity of K562 cells to NK cell-mediated killing increased significantly. After treatment with 0.2, 0.5 and 0.8 mg/ mL matrine, the percentage of K562 cells killed by NK cells was significantly higher than that of untreated cells (29.2%) (P<0.05). Matrine significantly inhibit the protein expression of phosphorylated STAT 3 and JAK2. Matrine markedly inhibited the IL-6 expression of K562 cells, and antagonized the IL-6 mediated STAT3 and JAK2 phosphorylation. In addition, matrine enhanced the inhibitory effect of STAT 3 inhibitor on STAT 3 activity. The silencing of STAT expression and inhibition of STAT3 activity significantly up-regulated the ULPB2 expression. Matrine had no effect on the expression of IL-6R and gp130 on K562 cells, the mRNA expression of IL-6R and gp130 increased slightly and the sgp 130 in cell supernatant significantly increased. CONCLUSIONS: Our findings reveal IL-6 and IL-6 receptor-mediated JAK/STAT3 pathway is involved in the matrine induced up-regulation of NKG2D ligands ULBP2 on K562 cells. Matrine might inhibit IL-6 expression and then suppress the activation of IL-6 receptor-mediated JAK/STAT3 pathway.

Matrine suppresses cell growth of human chronic myeloid leukemia cells via its inhibition of the interleukin-6/Janus activated kinase/signal transducer and activator of transcription 3 signaling cohort.

Matrine, alkaloid isolated from Sophora flavescens, is known to be pleiotropic by exerting anti-inflammatory, anti-oxidation, as well as anti-cancer effects. However, the precise molecular targets or pathways responsible for its activities still remain unclear. The present study aimed to determine the underlying mechanisms of matrine in inhibiting the chronic myeloid leukemia cells (CML). It was observed that matrine treatment significantly suppressed CML cells proliferation, induced apoptosis and resulted in the accumulation of cells in the G0/G1 phase, accompanied by a significant decrease in Bcl-xL, Cyclin D1, and c-Myc expression. Western blot analyses revealed that matrine treatment resulted in the down-regulation in phospho-STAT3 and phospho-JAK2 without significantly effects on STAT3 and JAK2 protein levels. Matrine significantly reduced the expression of IL-6, a potent upstream activating factor of STAT3. These results strongly suggested the IL-6/JAK/STAT3 pathway play an important role in matrine's anti-leukemia effects in K562 cells.

STAT3 contributes to NK cell recognition by modulating expression of NKG2D ligands in adriamycin-resistant K562/AO2 cells.

Leukemic cells can survive after chemotherapy by acquisition of multidrug resistance genes, but other phenotypes related to escape from immune recognition remain elusive. Adriamycin-resistant K562/AO2 cells are less susceptible to elimination by NK cells compared with wild type K562 cells due to lower expression of NKG2D ligands. Treatment of K562/AO2 cells with STAT3 inhibitor VII resulted in reduced expression of multidrug resistance gene P-glycoprotein, and up-regulation of NKG2D ligands on K562/AO2 cells. Meanwhile, K562/AO2 cells treated with STAT3 inhibitor proliferated less and were more susceptible to killing by NK cells than untreated K562/AO2 cells. The enhanced cytotoxicity of NK cells against K562/AO2 cells was partly blocked by treatment of NK cells with anti-NKG2D antibodies. These data suggest that STAT3 contributes to NK cell recognition by modulating NKG2D ligands in K562/AO2 cells, which may a mechanism by which cells survive and cause relapse of leukemia.

[Growth inhibition effect of matrine on K562 cells mediated by IL-6/JAK/STAT3 signaling pathway].

OBJECTIVE: To investigate the molecular mechanism of the growth inhibitory effect of matrine on K562 cells in JAK/STAT3 mediated signal pathway. METHODS: Western blot analyses were performed to investigate the differential expression of JAK2, STAT3, phosphor-STAT3 (Tyr705 & Ser727) and phosphor-JAK2 proteins after matrine treatment in K562 cells with or without human recombinant interleukin 6 (IL-6) pretreatment. The expression of STAT3 response gene products such as Bcl-xL, Cyclin D1 and c-Myc, were investigated by Western blot and quantitative real time RT-PCR (qRT-PCR). Expression of IL-6, a potent upstream activating factor of JAK/STAT3 pathway, was analyzed by both real time qRT-PCR and ELISA. RESUTLS: Western blot revealed that matrine treatment resulted in a strong down-regulation of phosphor-STAT3 both in Tyr705 and Ser727 sites or phosphor-JAK2 proteins expression without significant effects on the total STAT3 and JAK2 proteins. The expression of phosphor-Tyr705 STAT3 and phosphor-Ser727 STAT3 was decreased to 0.370 ± 0.172 in K562 cells treated with 0.5 mg/ml matrine for 48 h, respectively, from 0.690 ± 0.119 and 1.150 ± 0.263 in control cells, accompanied with a dramatical down-regulation of phosphor-JAK2 from 0.670 ± 0.137 to 0.049 ± 0.057 (P<0.05). In addition, it was found that the expression of Bcl-xL, Cyclin D1, c-Myc was decreased both at the transcription and protein level in K562 cells after matrine treatment. Matrine treatment resulted in a significant decrease in the expression level of IL-6 in K562 cells from (35.1 ± 1.93) to (10.74 ± 1.83) and (8.66 ± 1.24) pg/ml at the dose of 0.5 and 0.8 mg/ml, respectively (p<0.05). Matrine treatment could diminish the up-regulation of STAT3, JAK2, phosphor-STAT3 and phosphor-JAK2 protein following pretreatment with IL-6 in K562 cells. CONCLUSION: Matrine exerts its anti-leukemia effect by interfering with the JAK2/STAT3 signaling pathway. The inhibition of IL-6 expression may play a pivotal role in the disruption of JAK/STAT pathway by matrine.

Matrine regulates immune functions to inhibit the proliferation of leukemic cells.

AIMS: To investigate the roles of matrine in regulating immune functions and its effect on the proliferation of leukemic cells. METHODS: Human leukemia K562, OUN-1, HL-60, U937, K562/AO2 cell lines and primary leukemic cells were used to detect the NKG2D ligands (NKG2DL) expression such as MICA/B, ULBP-1, ULBP-2, ULBP-3, and NK cells receptor NKG2D, CD158a, CD158b were detected by flow cytometry. Cell cytotoxic activity of human NK cells and CIK cells against K562 leukemia cells was detected using CFSE/PI double staining. Pro-inflammatory cytokines and adhesion molecules in K562 or NK cells supernatant after matrine treatment were detected. RESULTS: Matrine could upregulate the expression of NKG2DL on leukemic cell lines, and primary leukemic cells and enhance the NK and CIK cytotoxicity targeted to K562 cells. After matrine treatment, pro-inflammatory cytokines and adhesion molecular such as IL-6, IL-1, IL-2, IL-4, IL-5, GRO and TNF-α in K562 cells supernatant were significantly decreased (P < 0.05). Flow cytometry analysis showed that the NKG2D expression was up-regulated significantly as well as the CD158a and CD158b expression decreased after treatment with different concentration of matrine in a dose-dependent manner in K562 cells. A significant decrease of supernatant concentrations of IL-1α, IL-5, IL-6, IL-10, IFN-γ, GRO and TNF-α in NK cells was also observed after exposure to the matrine. CONCLUSION: Matrine regulates immune functions to inhibit the proliferation of leukemic cells.

[Up-regulation of NKG2D ligand ULBP2 by matrine in K562 cells and the underlying molecular mechanisms].

OBJECTIVE: To probe matrine acting on natural killer cell (NK) activating receptor NKG2D ligands expression in CML cell line K562 and its underlying molecular mechanism. METHODS: The expression of NKG2D ligands (major histocompatibility complex class I chain-related molecule A or B (MICA/B), UL16-binding proteins (ULBP) 1, 2, and 3 on K562 cells were analyzed before and after treated with matrine by FCM. The cytotoxic sensitivity of K562 to NK cell was detected by FCM after CFSE staining at different effect-to-target (E/T) cell ratios. The expression of signal transduction and transcriptional activator 3 (STAT3) protein as well as phosphorylated STAT3 (p-STAT3) were detected by western blot. RESULTS: After treatment with matrine, ULBP1 and ULBP2 expression, especially ULBP2 on K562 cells significantly increased, with mean fluorescence intensity (MFI) increasing to 615 and 1614 by 220 and 615 in the untreated cells, respectively. There was no significant change for MICA or ULBP3 expression. Matrine enhanced the susceptibility of K562 cells to NK-mediated cell lysis. At the ratio of E/T with 5:1, the proportion of the killed K562 cells increased to 32.8%, 38.1% and 40.5%, respectively (after 0.2, 0.5 and 0.8 mg/ml matrine treatment) by 29.2% in the untreated cells. The phosphorylated STAT3 protein, but not STAT3 protein, was significantly inhibited by matrine treatment in K562 cells. CONCLUSION: Matrine induced the expression of NKG2D ligands in K562cells and enhanced the cytotoxicity of NK cells against K562, which was closely related to the inhibition of STAT3 activity in K562 cell.