Yuling Qiu

Stellettin B Induces G1 Arrest, Apoptosis and Autophagy in Human Non-small Cell Lung Cancer A549 Cells via Blocking PI3K/Akt/mTOR Pathway

Until now, there is not yet antitumor drug with dramatically improved efficacy on non-small cell lung cancer (NSCLC). Marine organisms are rich source of novel compounds with various activities. We isolated stellettin B (Stel B) from marine sponge Jaspis stellifera, and demonstrated that it induced G1 arrest, apoptosis and autophagy at low concentrations in human NSCLC A549 cells. G1 arrest by Stel B might be attributed to the reduction of cyclin D1 and enhancement of p27 expression. The apoptosis induction might be related to the cleavage of PARP and increase of ROS generation. Moreover, we demonstrated that Stel B induced autophagy in A549 cells by use of various assays including monodansylcadaverine (MDC) staining, transmission electron microscopy (TEM), tandem mRFP-GFP-LC3 fluorescence microscopy, and western blot detection of the autophagy markers of LC3B, p62 and Atg5. Meanwhile, Stel B inhibited the expression of PI3K-p110, and the phosphorylation of PDK1, Akt, mTOR, p70S6K as well as GSK-3β, suggesting the correlation of blocking PI3K/Akt/mTOR pathway with the above antitumor activities. Together, our findings indicate the antitumor potential of Stel B for NSCLC by targeting PI3K/Akt/mTOR pathway.

IVSE, isolated from Inula japonica,suppresses LPS-induced NO production via NF-κB and MAPK inactivation in RAW264.7 cells.

AIMS Our previous study showed that the extract of Inula japonica Thunb. (I. japonica) has anti-inflammatory and anti-asthmatic activities. In an attempt to find anti-inflammatory compounds from I. japonica, we recently isolated 1,6α-dihydroxy-4αH-1,10-secoeudesma-5(10),11(13)-dien-12,8β-olide (SE), 6α-isobutyryloxy-1-hydroxy-4αH-1,10-secoeudesma-5(10),11(13)-dien-12,8β-olide (IBSE), and 6α-isovaleryloxy-1-hydroxy-4αH-1,10-secoeudesma-5(10),11(13)-dien-12,8β-olide (IVSE) from the extract of I. japonica, and investigated their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. MAIN METHODS The inhibitory effect of IVSE, SE and IBSE on NO production in LPS-induced RAW264.7 cells was examined using Griess reagent, and the effects of IVSE on the expressions of inducible nitric oxide synthase (iNOS) and its upstream signal proteins including IκB kinase (IKK)/inhibitor kappa B (IκB)-α/nuclear factor κB (NF-κB) and mitogen-activated protein kinases (MAPKs) were investigated by Western blot. KEY FINDINGS Among the 3 compounds isolated, SE, IBSE, and IVSE inhibited NO production at 2.5 μM with 5.1%, 40.4%, and 52.8%, respectively. IVSE displayed the most potent inhibition of NO production. Mechanism analysis indicated that IVSE dramatically decreased the expression of iNOS, reduced the translocation of the NF-κB subunit p65 into the nucleus by interrupting the phosphorylation and degradation of IκB-α, and inhibited the activation of the upstream mediator IKK α/β. Furthermore, our results showed that IVSE inhibited the phosphorylation of MAPKs including extracellular regulated kinases (ERK1/2), c-Jun N-terminal kinases (JNK) and p38. SIGNIFICANCE IVSE exhibited anti-inflammatory activity by inhibiting NO production, in which inactivation of NF-κB and MAPKs might be involved. Our results suggest that IVSE might become an anti-inflammatory drug candidate.

ZSTK474, a specific class I phosphatidylinositol 3-kinase inhibitor, induces G1 arrest and autophagy in human breast cancer MCF-7 cells

Multifaceted activities of class I phosphatidylinositol 3-kinase (PI3K) inhibitor ZSTK474 were investigated on human breast cancer cell MCF-7. ZSTK474 inhibited proliferation of MCF-7 cells potently. Flow cytometric analysis indicated that ZSTK474 induced cell cycle arrest at G1 phase, but no obvious apoptosis occurred. Western blot analysis suggested that blockade of PI3K/Akt/GSK-3β/cyclin D1/p-Rb pathway might contribute to the G1 arrest induced. Moreover, we demonstrated that ZSTK474 induced autophagy in MCF-7 cells by use of various assays including monodansylcadaverine (MDC) staining, transmission electron microscopy (TEM), tandem mRFP-GFP-LC3 fluorescence microscopy, and western blot detection of the autophagy protein markers of LC3B II, p62 and Atg 5. Inhibition of class I PI3K and the downstream mTOR might be involved in the autophagy-inducing effect. Combinational use of ZSTK474 and autophagy inhibitors enhanced cell viability, suggesting ZSTK474-induced autophagy might contribute to the antitumor activity. Our report supports the application of ZSTK474, which is being evaluated in clinical trials, for breast cancer therapy.

In Vitro Antitumor Activity of Stellettin B, a Triterpene from Marine Sponge Jaspis stellifera, on Human Glioblastoma Cancer SF295 Cells

Stellettin B was isolated from marine sponge Jaspis stellifera. In vitro antitumor activities were investigated on 39 human cancer cell lines. Stellettin B exhibited highly potent inhibition against the growth of a human glioblastoma cell line SF295, with a GI50 of 0.01 μM. In contrast, stellettin B showed very weak inhibitory activity on normal cell lines including HMEC, RPTEC, NHBE and PrEC, with GI50s higher than 10 μM, suggesting its relatively selective cytotoxicity against human cancer cells compared to normal human cell lines. We then focused on the antitumor activity of this compound on SF295 cells. Flow cytometric analysis indicated that stellettin B induced apoptosis in SF295 cells in a concentration-dependent manner. Further study indicated that stellettin B increased the production of ROS, the activity of caspase 3/7, as well as the cleavage of PARP, each of which is known to be involved in apoptosis. To investigate the molecular mechanism for cell proliferation inhibition and apoptosis induction, effect on the phosphorylation of several signal proteins of PI3K/Akt and RAS/MAPK pathways was examined. Stellettin B inhibited the phosphorylation of Akt potently, with no activity on p-ERK and p-p38, suggesting that inhibition of PI3K/Akt pathway might be involved in the antiproliferative and apoptosis-inducing effect. However, homogenous time-resolved fluorescence (HTRF) assay indicated that stellettin B did not inhibit PI3K activity, suggesting that the direct target might be signal protein upstream of Akt pathway other than PI3K.

In Vitro Antimetastatic Effect of Phosphatidylinositol 3-Kinase Inhibitor ZSTK474 on Prostate Cancer PC3 Cells

Tumor metastasis is the main cause of lethality of prostate cancer, because conventional therapies like surgery and hormone treatment rarely work at this stage. Tumor cell migration, invasion and adhesion are necessary processes for metastasis. By providing nutrition and an escape route from the primary site, angiogenesis is also required for tumor metastasis. Phosphatidylinositol 3-kinases (PI3Ks) are well known to play important roles in tumorigenesis as well as metastasis. ZSTK474 is a specific PI3K inhibitor developed for solid tumor therapy. In the present report, antimetastatic activities of ZSTK474 were investigated in vitro by determining the effects on the main metastatic processes. ZSTK474 exhibited inhibitory effects on migration, invasion and adhesive ability of prostate cancer PC3 cells. Furthermore, ZSTK474 inhibited phosphorylation of Akt substrate-Girdin, and the secretion of matrix metalloproteinase (MMP), both of which were reported to be closely involved in migration and invasion. On the other hand, ZSTK474 inhibited the expression of HIF-1α and the secretion of vascular endothelial growth factor (VEGF), suggesting its potential antiangiogenic activity on PC3 cells. Moreover, we demonstrated the antiangiogenesis by determining the effect of ZSTK474-reduced VEGF on tube formation of human umbilical vein endothelial cells (HUVECs). In conclusion, ZSTK474 was demonstrated to have potential in vitro antimetastatic effects on PC3 cells via dual mechanisms: inhibition of metastatic processes including cell migration, invasion and adhesion, and antiangiogenesis via blockade of VEGF secretion.

Inhibitory Effects of JEUD-38, a New Sesquiterpene Lactone from Inula japonica Thunb, on LPS-Induced iNOS Expression in RAW264.7 Cells

ABSTRACTWe isolated JEUD-38, a new sesquiterpene lactone from Inula japonica Thunb. JEUD-38 dramatically attenuated lipopolysaccharide (LPS)-induced nitric oxide (NO) production. Consistent with this finding, the protein expression of inducible nitric oxide synthase (iNOS) was blocked by JEUD-38 in a concentration-dependent manner. To elucidate the mechanism, we examined the effect of JEUD-38 on LPS-stimulated nuclear factor-κB (NF-κB) nuclear translocation, inhibitory factor-κB (IκB) phosphorylation, and degradation. JEUD-38 reduced the translocation of p65, via abrogating IκB-α phosphorylation and degradation. In addition, JEUD-38 inhibited LPS-stimulated phosphorylation of mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38. Since iNOS as well as the upstream NF-κB and MAPKs are known to be closely involved in inflammation, these results suggest that JEUD-38 is a promising candidate for prevention and therapy of inflammatory diseases.

In Vitro Antileukemia Activity of ZSTK474 on K562 and Multidrug Resistant K562/A02 Cells

Chronic myelogenous leukemia (CML) is a malignant hematological disorder mainly caused by the Bcr-Abl tyrosine kinase. While Bcr-Abl inhibitors including Imatinib showed antitumor efficacy on many CML patients, resistance was frequently reported in recent years. Therefore, novel drugs for CML are still expected. ZSTK474 is a specific phosphatidylinositol 3-kinase (PI3K) inhibitor that we identified. In the present study, the efficacy of ZSTK474, alone or in combination with Imatinib, on K562 CML cells as well as on its multidrug resistance counterpart K562/A02 cells, was investigated. ZSTK474 inhibited the cell proliferation with an IC50 of 4.69 μM for K562 and 7.57 μM for K562/A02 cells, respectively. Treatment by ZSTK474 resulted in cell cycle arrest in G1 phase, which might be associated with upregulation of p27, and downregulation of cyclin D1. ZSTK474 also inhibited phosphorylation of Akt and GSK-3β, which might be involved in the effect on the above cell cycle-related proteins. Moreover, combination of ZSTK474 and Imatinib indicated synergistic effect on both cell lines. In conclusion, ZSTK474 exhibited antileukemia activity alone, and showed synergistic effect when combined with Imatinib, on CML K562 cells as well as the multidrug resistant ones, providing a potential therapeutic approach for CML patients.

Stellettin B induces apoptosis in human chronic myeloid leukemia cells via targeting PI3K and Stat5

Novel agents are still urgently expected for therapy of chronic myeloid leukemia (CML). The in vitro anti-leukemia activity of Stellettin B (Stel B), a triterpenoid we isolated from marine sponge Jaspis stellifera, on human CML K562 and KU812 cells was recently investigated. Stel B inhibited K562 and KU812 cell proliferation with IC50 as 0.035 μM and 0.95 μM respectively. While no obvious cell cycle arrest was observed, apoptosis was induced in K562 cells after Stel B treatment. The Stel B-induced apoptosis might be in mitochondrial pathway, with increase of Bad and Bax, decrease of Bcl-2 and activation of caspase-9. In addition, dose-dependent increase of reactive oxygen species (ROS) and loss of mitochondrial membrane potential (MMP) occurred. Meanwhile, Stel B inhibited phosphorylation of Stat5, expression of 4 PI3K catalytic isoforms, and phosphorylation of the downstream effectors including PDK1 and Akt, suggesting that inhibition against Stat5 and PI3K might be involved in the apoptosis-inducing effect. Combination of Stel B with Imatinib with ratio as IC50 Stel B: 5×IC50 Imatinib led to synergistic effect. Stel B might become a promising candidate for CML therapy alone or together with Imatinib.

Roburic Acid Suppresses NO and IL-6 Production via Targeting NF-κB and MAPK Pathway in RAW264.7 Cells

In the present study, we investigated the anti-inflammatory effect of roburic acid on production of nitric oxide (NO) and interlukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. We found that roburic acid reduced production of NO and IL-6, and the expression of inducible nitric oxide synthases (iNOS). Meanwhile, phosphorylation of inhibitor of κBα (IκBα) and IκB kinase α/β (IKKα/β), as well as translocation of nuclear factor-κB (NF-κB) to the nucleus, was suppressed by roburic acid treatment. In addition, phosphorylation of mitogen-activated protein kinase (MAPKs) including p38 and c-Jun-NH2-terminal kinase (JNK) was inhibited. Roburic acid exhibited inhibitory activities on production of NO and IL-6 via blocking IKK/IκB/NF-κB and MAPKs pathway, suggesting the potential application as a drug candidate for therapy of inflammatory diseases.

Discovery of two Bombinin peptides with antimicrobial and anticancer activities from the skin secretion of Oriental Fire-bellied toad, Bombina orientalis

Amphibian skin secretions are known to contain numerous peptides with a large array of biological activities. Bombinins are a group of amphibian‐derived peptides with broad spectrum antimicrobial activities that have been only identified from the ancient toad species, Bombina. In this study, we described the identification and characterization of a novel bombinin precursor which encoded a bombinin‐like peptide (BLP‐7) and a novel bombinin H‐type peptide (named as Bombinin H‐BO) from the skin secretion of Oriental fire‐bellied toad, Bombina orientalis. The primary structures of both mature peptides were determined by combinations of molecular cloning of peptide precursor‐encoding cDNAs and mass spectrometry techniques. Secondary structure prediction revealed that both peptides had cationic amphipathic α‐helical structural features. The synthetic replicate of BLP‐7 displayed more potent antimicrobial activity than Bombinin H‐BO against Gram‐positive and Gram‐negative bacteria and yeast. Also, in vitro antitumour assay showed that both peptides possessed obvious antiproliferative activity on three human hepatoma cells (Hep G2/SK‐HEP‐1/Huh7) at the non‐toxic doses. These results indicate the peptide family of bombinins could be a potential source of drug candidates for anti‐infection and anticancer therapy.