Wogonin induces the granulocytic differentiation of human NB4 promyelocytic leukemia cells and up-regulates phospholipid scramblase 1 gene expression

Leukemia Chemoprevention and Therapeutic Potentials: Selected Medicinal Plants with Anti-Leukemic Activities

Haematological malignancies account for more than one million cases of all cancers yearly worldwide. While survival has improved due to newer drugs used in their management, relapsed/refractory disease remains a challenge, and treatment modalities come with side effects and morbidities. The management of leukaemias with medicinal plants and their natural products remain a viable option. Numerous studies have shown the potentials and viability of medicinal plants and their natural products as good options against leukaemias. However many of these natural products face peculiar challenges such as low systemic bioavailability, hydrophobic nature and displayed toxicities when given at different pharmacologic doses, while the medicinal plants face the threat of extinction. The development of semi-synthetic analogues and better regulations have helped overcome some of these challenges. This review briefly analyzes four medicinal plants and their different natural products that are used traditionally in the management of cancers, and have been scientifically proven to have some form of activity against leukemia. These plants include Tanacetum parthenium, Garcinia hanburyi, Scutellaria baicalensis, and Combretum caffrum. This review discusses these medicinal plants and their natural products under the following headings: ethnobotany, phytochemistry, mechanism of action, antileukaemic activity and toxicity.

Oroxylin A, a natural compound, mitigates the negative effects of TNFα-treated acute myelogenous leukemia cells

Tumor necrosis factor alpha (TNFα) is a complicated cytokine which is involved in proliferation and differentiation of acute myelogenous leukemia (AML) cells through a poorly understood mechanism. Mechanistic studies indicate that TNFα induced binding of PI3K subunit p85α to N-terminal truncated nuclear receptor RXRα (tRXRα) proteins, and activated AKT. The activated PI3K/AKT pathway negatively regulated differentiation of AML cells through the upregulation of c-Myc. In addition, TNFα also induced activation of nuclear factor κB (NF-κB), a nuclear transcription factor which was shown to promote cell proliferation. The present study demonstrates that oroxylin A, a natural compound isolated from Scutellariae radix, sensitizes leukemia cells to TNFα and markedly enhances TNFα-induced growth inhibition and differentiation of AML cell including human leukemia cell lines and primary AML cells. Activation of PI3K/AKT pathway could be inhibited by oroxylin A through inhibiting expression of tRXRα in NB4 and HL-60-resistant cells. Furthermore, we found that oroxylin A inhibited the activation of NF-κB and the DNA binding activity by TNFα proved by EMSA in these two AML cell lines. Moreover, in vivo studies showed that treatment with oroxylin A in combination with TNFα decreased AML cell population and prolonged survival in NOD/SCID mice with xenografts of primary AML cells. Overall, our results indicate that oroxylin A is able to inhibit the negative effects of TNFα for AML therapy, suggesting that combination of oroxylin A and TNFα have the potential to delay growth or eliminate the abnormal leukemic cells, thus representing a promising strategy for AML treatment.

New synergistic combinations of differentiation-inducing agents in the treatment of acute promyelocytic leukemia cells

Acute promyelocytic leukemia (APL) was considered to be one of the most lethal forms of leukemia in adults before the introduction of the vitamin A metabolite all-trans retinoic acid (ATRA). Surprisingly, it has been confirmed that FICZ (6-Formylindolo (3, 2-b) carbazole) enhances ATRA-induced differentiation. Moreover, a number of studies have demonstrated that anti CD44 monoclonal antibody (mAb) induces to bring back differentiation blockage the leukemic stem cells. The level of differentiation markers including CD11b and CD11c in NB4 cells was assessed by flow cytometry. The induction of apoptosis was also evaluated. We estimated the induction potential of a triple compound of ATRA-FICZ, anti-CD44 maps. The cells showed the gradually increased expression levels of CD11b and CD11c. A mixture of a "CD44 mAb, ATRA and FICZ effectively promoted granulocytic maturation resulting in increased rates of apoptosis. The differences in expression of CD11b and CD11c at 5 μg/ml and 10 μg/ml were significant. These phenomena were highest at 10 μg/ml CD44 mAb concentrations. Synergistic induction differentiation and apoptosis of APL cells by using a co-treatment with novel triple compound are more effective for eradicating blasts and controlling the metastasis. Our results show that the addition of anti-CD44 mAb improves "ATRA-FICZ"-induced differentiation and has potential to reduce usual chemotherapy based treatments. Taken together, this compound may lead to novel clinical applications of differentiation-based approaches for APL and other types of leukemia. Further clinical studies would be recommended to clarify the clinical efficacy.

Wogonin induces retinal neuron-like differentiation of bone marrow stem cells by inhibiting Notch-1 signaling

Age-related macular degeneration and retinitis pigmentosa are major causes of irreversible vision loss in the elderly and, despite sustained efforts, current treatments are largely ineffective. Wogonin is a bioactive plant flavonoid possessing a range of beneficial properties, including neuroprotective effects. We investigated the ability of wogonin to promote retinal neuron-like differentiation of bone marrow stem cells (BMSCs) and assessed the involvement of Notch-1 signaling in this process. Cultured mouse BMSCs were left untreated or exposed to neurotrophic factors in the presence or absence of wogonin, and western blotting, RT-PCR and immunofluorescence were used to identify changes in molecular markers of stemness and neuroretinal differentiation. Proteins in the Notch-1 signaling pathway, a main negative regulator of neurogenesis, were also examined by western blotting. We found that expression of stem cell markers was reduced, while markers of mature retinal neurons, bipolar cells and photoreceptors were increased in wogonin-treated BMSCs. Wogonin also dose-dependently decreased expression of Notch-1 signaling proteins. Moreover, blockade of Notch-1 both mimicked and enhanced the effect of wogonin to facilitate BMSC differentiation into retinal neuron-like cells. Wogonin thus appears to promote retinal neuron-like differentiation of BMSCs by antagonizing the inhibitory actions of Notch-1 signaling on neurogenesis and may be useful in the treatment of retinal degenerative diseases.

BM microenvironmental protection of CML cells from imatinib through Stat5/NF-κB signaling and reversal by Wogonin

Constitutive Stat5 activation enhanced cell survival and resistance to imatinib (IM) in chronic myelogenous leukemia (CML) cells. However, the mechanism of Stat5 activation in mediating resistance to IM in bone marrow (BM) microenvironment has not been evaluated precisely. In this study, we reported HS-5-derived conditioned medium (CM) significantly enhanced IM resistance in K562 and KU812. Interestingly, upregulation of the proportion of CD34+ subpopulation was found in CML cells. Subsequently, the BCR/ABL-independent activation of Stat5 increased P-glycoprotein (P-gp) activity in CM-mediated protection of CML stem cells (LSCs) from IM. Further research revealed Stat5 activation increased the DNA binding activity of NF-κB though binding of p-Stat5 and p-RelA in nucleus. Moreover, highly acetylated RelA was required for Stat5-mediated RelA nuclear binding. The study further confirmed that Wogonin potentiated the inhibitory effects of IM on leukemia development by suppressing Stat5 pathway both in CM model and the K562 xenograft model. In summary, results clearly demonstrated BCR/ABL-independent Stat5 survival pathway could contribute to resistance of CML LSCs to IM in BM microenvironment and suggested that natural durgs effectively inhibiting Stat5 may be an attractive approach to overcome resistance to BCR/ABL kinase inhibitors.

Wogonin enhances intracellular adiponectin levels and suppresses adiponectin secretion in 3T3-L1 adipocytes

As an insulin sensitizer and modulator of inflammatory responses, adiponectin has become a therapeutic target for insulin resistance, diabetes, and diabetes-related complications. Wogonin possesses anti-oxidative, anti-inflammatory, and anti-diabetic abilities. However, its effect on generation and secretion of adiponectin is ill-defined in adipocytes. Here, we demonstrated that wogonin administration augmented intracellular adiponectin levels and attenuated adiponectin release in a dose- and time-dependent manner in mature 3T3-L1 adipocytes, along with a suppression of PKCδ phosphorylation. Wogonin treatment also prevented PKCδ overexpression-induced reduction of intracellular adiponectin levels and enhancement of adiponectin release. In addition, wogonin supplementation dramatically increased AMPK phosphorylation and SirT1 expression. Inhibition of either AMPK or SirT1 mitigated wogonin action on adiponectin production and release. Furthermore, inhibition of AMPK by its specific inhibitor markedly reduced wogonin-enhanced mRNA and protein expressions of SirT1. These results suggested that wogonin regulated expression and secretion of adiponectin via PKCδ/AMPK/SirT1 signaling pathway in mature 3T3-L1 adipocytes.

Established Human Cell Lines as Models to Study Anti-leukemic Effects of Flavonoids

Despite the extensive work on pathological mechanisms and some recent advances in the treatment of different hematological malignancies, leukemia continues to present a significant challenge being frequently considered as incurable disease. Therefore, the development of novel therapeutic agents with high efficacy and low toxicity is urgently needed to improve the overall survival rate of patients. In this comprehensive review article, the current knowledge about the anticancer activities of flavonoids as plant secondary polyphenolic metabolites in the most commonly used human established leukemia cell lines (HL-60, NB4, KG1a, U937, THP-1, K562, Jurkat, CCRF- CEM, MOLT-3, and MOLT-4) is compiled, revealing clear anti-proliferative, pro-apoptotic, cell cycle arresting, and differentiation inducing effects for certain compounds. Considering the low toxicity of these substances in normal blood cells, the presented data show a great potential of flavonoids to be developed into novel anti-leukemia agents applicable also in the malignant cells resistant to the current conventional chemotherapeutic drugs.

Latest research progress in the correlation between baicalein and breast cancer invasion and metastasis

Breast cancer is one of the most commonly occurring female malignant tumors. According to the 2012 GLOBOCAN statistics, produced by the International Agency for Research On Cancer ('IARC'), nearly 1.7 million women were diagnosed with breast cancer, with 522,000 related deaths: An increase in the incidence of breast cancer and associated mortality by nearly 18% from 2008. Metastasis is the final step in breast cancer progression, and represents the most common cause of mortality in patients with breast cancer. Therefore, a search for low-toxicity, safe and effective anti-breast cancer drugs in the form of natural compounds has become an intense focus of research. Baicalein, a widely used Chinese herbal medicine, has extensive antitumor activity. The present review briefly describes the research that has been performed on the association between baicalein and breast cancer metastasis, and further illustrates the influence of baicalein on the underlying mechanisms of breast cancer metastasis, adding a novel theory basis for baicalein antitumor research. In conclusion, baicalein may represent a promising target for the prevention and therapy of breast cancer.

Natural compounds and pharmaceuticals reprogram leukemia cell differentiation pathways

In addition to apoptosis resistance and cell proliferation capacities, the undifferentiated state also characterizes most cancer cells, especially leukemia cells. Cell differentiation is a multifaceted process that depends on complex regulatory networks that involve transcriptional, post-transcriptional and epigenetic regulation of gene expression. The time- and spatially-dependent expression of lineage-specific genes and genes that control cell growth and cell death is implicated in the process of maturation. The induction of cancer cell differentiation is considered an alternative approach to elicit cell death and proliferation arrest. Differentiation therapy has mainly been developed to treat acute myeloid leukemia, notably with all-trans retinoic acid (ATRA). Numerous molecules from diverse natural or synthetic origins are effective alone or in association with ATRA in both in vitro and in vivo experiments. During the last two decades, pharmaceuticals and natural compounds with various chemical structures, including alkaloids, flavonoids and polyphenols, were identified as potential differentiating agents of hematopoietic pathways and osteogenesis.

Gambogic acid induces growth inhibition and differentiation via upregulation of p21waf1/cip1 expression in acute myeloid leukemia cells

Gambogic acid (GA) is the major active ingredient of gamboges, a brownish to orange resin product from Garcinia hanburyi tree in Southeast Asia. This compound exhibits anti-cancer effect on solid tumors. In this study, we investigated the effects of GA on the growth and differentiation of acute myeloid leukemia cells by growth-inhibition detection, morphological changes observation, nitroblue tetrazolium reduction, and the expression of the relative cell-surface differentiation markers. The results showed that GA could inhibit cell growth and promote differentiation in U937 and HL-60 cells. In addition, GA upregulated the expression of p21waf1/cip1 in the two cell lines. Finally, downregulating the p21waf1/cip1 expression with small interfering RNA partially blocked GA-induced cell growth inhibition and differentiation. These results of this study revealed that GA may be used as one of the investigational drugs for acute myeloid leukemia.

Wogonin induces cell cycle arrest and erythroid differentiation in imatinib-resistant K562 cells and primary CML cells

Wogonin, a flavonoid derived from Scutellaria baicalensis Georgi, has been demonstrated to be highly effective in treating hematologic malignancies. In this study, we investigated the anticancer effects of wogonin on K562 cells, K562 imatinib-resistant cells, and primary patient-derived CML cells. Wogonin up-regulated transcription factor GATA-1 and enhanced binding between GATA-1 and FOG-1, thereby increasing expression of erythroid-differentiation genes. Wogonin also up-regulated the expression of p21 and induced cell cycle arrest. Studies employing benzidine staining and analyses of cell surface markers glycophorin A (GPA) and CD71 indicated that wogonin promoted differentiation of K562, imatinib-resistant K562, and primary patient-derived CML cells. Wogonin also enhanced binding between GATA-1 and MEK, resulting in inhibition of the growth of CML cells. Additionally, in vivo studies showed that wogonin decreased the number of CML cells and prolonged survival of NOD/SCID mice injected with K562 and imatinib-resistant K562 cells. These data suggested that wogonin induces cycle arrest and erythroid differentiation in vitro and inhibits proliferation in vivo.

Wogonin induced cytotoxicity in human hepatocellular carcinoma cells by activation of unfolded protein response and inactivation of AKT

AIM

To investigate the potential anticancer effects of the natural flavonoid wogonin on human hepatocellular carcinoma (HCC) cells and tumor xenografts and the contribution of the unfolded protein response (UPR) and AKT pathways to the cytotoxicity of wogonin.

METHODS

The HCC cell lines HepG2, SMMC-7721 and Hep3B were treated with wogonin. 3-(4 5-Dimethylthiazol-2-yl)-2 5-diphenyltetrazolium bromide assays were used to evaluate the cell viability. Flow cytometry assays were used to identify the cell death types and measure the concentrations of intracellular H2 O2 and Ca(2+) . Western blotting assays were used to detect the protein expression levels of members in the UPR and AKT pathways. Relative quantitative real-time polymerase chain reaction assays were used to analysis the mRNA expression levels of chop and trb3. Furthermore, the male BALB/c nude mice with SMMC-7721 xenografts were treated with wogonin. The tumor volume, tumor weight and bodyweight were monitored during the tumorigenicity assays.

RESULTS

Wogonin significantly inhibited the viability of HCC cells by inducing apoptosis and necrosis. This cytotoxicity was at least partially attributed to the activation of the UPR pathway and consequent inactivation of AKT signaling, which resulted from the production of intracellular H2 O2 and causal release of endoplasmic reticulum Ca(2+) . Moreover, wogonin evidently repressed the growth of xenografts but slightly influenced the bodyweight of mice.

CONCLUSION

Wogonin is a prospect for improving the systemic chemotherapy strategy on HCC by concurrently rectifying the aberrant UPR and AKT signaling pathways, which are crucial to the biology of HCC.

Wogonoside induces cell cycle arrest and differentiation by affecting expression and subcellular localization of PLSCR1 in AML cells

Wogonoside induces cell cycle arrest and differentiation. Wogonoside acts by changing PLSCR1 expression and subcellular localization in the nucleus and by PLSCR1-related molecular events.

Gan-Lu-Yin Inhibits Proliferation and Migration of Murine WEHI-3 Leukemia Cells and Tumor Growth in BALB/C Allograft Tumor Model

The aim of this study was to explore the antitumor effect of Gan-Lu-Yin (GLY), a traditional Chinese herbal formula, on leukemia. Ethanolic extract of GLY was applied to evaluate its regulatory mechanisms in proliferation, migration, and differentiation of WEHI-3 leukemic cells as well as antitumor effect on BALB/c mice model. The results showed that GLY markedly reduced cell proliferation and migration with induced differentiation of WEHI-3 cells. The expression level of phosphorylated FAK, Akt, ERK1/2, and Rb was decreased p21 expression while level was increased in WEHI-3 treated with GLY. The results of cell cycle analysis revealed that GLY treatment could markedly induce G1 phase arrest and decrease cell population in S phase. Moreover, experimental results demonstrated that GLY decreased the protein expression and enzyme activity of MMP-2 and MMP-9. GLY treatment also reduced WEHI-3 leukemic infiltration in liver and spleen and tumor growth in animal model. Accordingly, GLY demonstrated an inhibitory effect on tumor growth with a regulatory mechanism partially through inhibiting FAK, Akt, and ERK expression in WEHI-3 cells. GLY may provide a promising antileukemic approach in the clinical application.

Inhibition of the receptor tyrosine kinase Axl impedes activation of the FLT3 internal tandem duplication in human acute myeloid leukemia: implications for Axl as a potential therapeutic target

Approximately 20% to 25% of patients with acute myeloid leukemia (AML) have a constitutively activated FLT3-internal tandem duplication (FLT3-ITD), and these patients exhibit a poor prognosis. Here, we report that Axl, a receptor tyrosine kinase (RTK) overexpressed and constitutively active in human AML, targets the RTK FLT3 in FLT3-ITD(+) AML. Abrogation of Axl activation by soluble Axl chimeric protein (Axl-Fc) or small interfering RNA (siRNA) diminishes constitutive FLT3 phosphorylation in FLT3-ITD(+) AML. In addition, inhibition of Axl activation by Axl-Fc interferes with the physical interaction between Axl and FLT3. We found that Axl-Fc, a pharmacologic Axl inhibitor, or siRNA targeting Axl inhibits cell growth, induces cell-cycle arrest and apoptosis, and relieves a block in myeloid differentiation of FLT3-ITD(+) AML in vitro. Axl-Fc also suppresses the growth of human FLT3-ITD(+) AML in vivo. Collectively, our data suggest that Axl contributes to the pathogenesis of FLT3-ITD(+) AML through, at least in part, positive regulation of constitutive FLT3 activation. This also suggests that Axl should be pursued as a potential target for the treatment of FLT3-ITD(+) AML.

LYG-202 inhibits the proliferation of human colorectal carcinoma HCT-116 cells through induction of G1/S cell cycle arrest and apoptosis via p53 and p21(WAF1/Cip1) expression

We recently established that LYG-202, a new flavonoid with a piperazine substitution, exerts an anti-tumor effect in vivo and in vitro. In the present study, we demonstrate that LYG-202 induces G1/S phase arrest and apoptosis in human colorectal carcinoma HCT-116 cells. Data showed that the blockade of the cell cycle was associated with increased p21(WAF1/Cip1) and Rb levels and reduced expression of cyclin D1, cyclin E, and CDK4. Moreover, PARP cleavage, activation of caspase-3, caspase-8, and caspase-9, and an increased ratio of Bax/Bcl-2 were detected in LYG-202-induced apoptosis. Additionally, activation of p53 resulted in the up-regulation of its downstream targets PUMA and p21(WAF1/Cip1), as well as the down-regulation of its negative regulator MDM2, suggesting that the p53 pathway may play a crucial role in LYG-202-induced cell cycle arrest and apoptosis. Furthermore, siRNA knockdown of p53 attenuated the G1 cell cycle arrest and apoptosis induced by LYG-202, as the effects of LYG-202 on up-regulation of p21(WAF1/Cip1) and down-regulation of Bcl-2 and pro-caspase-3 were partly inhibited in p53 siRNA transfected cells compared with control siRNA transfected cells. Collectively, these data indicate that LYG-202 exerts its anti-tumor potency by activating the p53-p21 pathway for G1/S cell cycle arrest and apoptosis in colorectal cancer cells.

Phytochemicals: cancer chemoprevention and suppression of tumor onset and metastasis

Carcinogenesis is a multi-step process which could be prevented by phytochemicals. Phytochemicals from dietary plants and other plant sources such as herbs are becoming increasingly important sources of anticancer drugs or compounds for cancer chemoprevention or adjuvant chemotherapy. Phytochemicals can prevent cancer initiation, promotion, and progression by exerting anti-inflammatory and anti-oxidative stress effects which are mediated by integrated Nrf2, NF-kappaB, and AP-1 signaling pathways. In addition, phytochemicals from herbal medicinal plants and/or some dietary plants developed in recent years have been shown to induce apoptosis in cancer cells and inhibition of tumor growth in vivo. In advanced tumors, a series of changes involving critical signaling molecules that would drive tumor cells undergoing epithelial-mesenchymal transition and becoming invasive. In this review, we will discuss the potential molecular targets and signaling pathways that mediate tumor onset and metastasis. In addition, we will shed light on some of the phytochemicals that are capable of targeting these signaling pathways which would make them potentially applicable to cancer chemoprevention, treatment and control of cancer progression.

Wogonin induces G1 phase arrest through inhibiting Cdk4 and cyclin D1 concomitant with an elevation in p21Cip1 in human cervical carcinoma HeLa cells

Wogonin, a naturally occurring flavonoid, has been shown to have tumor therapeutic potential both in vitro and in vivo. To better understand its anticancer mechanism, we examined the effect of wogonin on human cervical carcinoma HeLa cells. In this study, we observed that G1 phase arrest was involved in wogonin-induced growth inhibition in HeLa cells. Over a 24 h exposure of HeLa cells to 90 µmol·L–1 wogonin, the promoters of G1–S transition, including cyclin D1/Cdk4 and pRb, decreased within 12 h and E2F-1 depleted in the nucleus at the same time. As the G1 phase arrest developed, p53 and the Cdk inhibitor p21Cip1 elevated both at protein and mRNA levels. Furthermore, the up-regulation of p21Cip1 induced by wogonin was dramatically inhibited by siRNA-mediated p53 gene silencing. Collectively, our data suggested that wogonin induced G1 phase arrest in HeLa cells by modulating several key G1 regulatory proteins, such as Cdk4 and cyclin D1, as well as up-regulation of a p53-midiated p21Cip1 expression. This mechanism of wogonin may play an important role in the killing of cancerous cells and offer a potential mechanism for its anticancer action in vivo.

Subchronic toxicity and plasma pharmacokinetic studies on wogonin, a natural flavonoid, in Beagle dogs

AIM OF THE STUDY

To investigate subchronic toxicity and pharmacokinetic of wogonin using Beagle dog and to provide foundation for clinical applications of this promising anticancer agent.

MATERIALS AND METHODS

Wogonin was administered via intravenous infusion at dosages of 60, 30 and 15 mg/kg per day for 90 days followed by subchronic toxicity studies including general body parameters, hematological, plasma biochemical, histopathological, and viscera examinations. Dogs were given single intravenous injection of 20mg/kg wogonin followed by pharmacokinetic parameters estimating.

RESULTS

Dogs treated with wogonin showed no significant changes in organs compared with controls in the toxicological study. An innocuous dose was established to be 60 mg/kg, which was approximately 38.5 (body surface area) times higher than the dose (50mg/60 kg) used for human trials. The area under concentration-time curve (AUC(infinity)) was estimated to be 2137.9+/-231.4 ngh/ml, while the elimination half-life (t(1/2)) was 1.51+/-0.43 h in dogs treated with 20mg/kg wogonin.

CONCLUSIONS

Wogonin offered a wide margin of safety and had no organ toxicity for a long time intravenous administration in dogs.