Fluacrypyrim, a novel STAT3 activation inhibitor, induces cell cycle arrest and apoptosis in cancer cells harboring constitutively-active STAT3.

STAT3 protein has an important role in oncogenesis and is a promising anticancer target. Herein, we demonstrate that a novel small molecule fluacrypyrim (FAPM) inhibits the growth of leukemia cells by a predominant G1 arrest with significant decrease of the protein and mRNA levels of cyclin D1. As cyclin D1 is transcriptionally regulated by STAT3, FAPM is then shown to markedly inhibit the STAT3 phosphorylation with marginal effect on the other signal transducers and activators of transcription, and without effect on phosphoinositide-3-kinase and mitogen-activated protein kinase pathways. Further analysis shows that FAPM significantly increases the protein tyrosine phosphatases (PTPs) activity in a dose-dependent manner, and the inhibition of PTP activation by sodium pervanadate reverses FAPM-induced suppression of STAT3 tyrosine phosphorylation, indicating an important role of PTP in the action of FAPM. Finally, FAPM treatment results in selective suppression of STAT3-mediated transcriptional activity and its downstream effectors, and subsequent induction of growth arrest and apoptosis in STAT3-dependent cancer cell lines. This study therefore identifies FAPM as a potent STAT3 activation inhibitor with possible therapeutic potential against malignancies with constitutive STAT3 activation.

Single-Dose Administration of Recombinant Human Thrombopoietin Mitigates Total Body Irradiation-Induced Hematopoietic System Injury in Mice and Nonhuman Primates.

PURPOSE: Recombinant human thrombopoietin (rhTPO) has been evaluated as a therapeutic intervention for radiation-induced myelosuppression. However, the immunogenicity induced by a repeated-dosing strategy raises concerns about the therapeutic use of rhTPO. In this study, single-dose administration of rhTPO was evaluated for efficacy in the hematopoietic response and survival effect on mice and nonhuman primates exposed to total body irradiation (TBI). METHODS AND MATERIALS: Survival of lethally (9.0 Gy) irradiated C57BL/6J male mice was observed for 30 days after irradiation. Hematologic evaluations were performed on C57BL/6J male mice given a sublethal dose of radiation (6.5 Gy). Furthermore, in sublethally irradiated mice, we performed bone marrow (BM) histologic evaluation and evaluated BM-derived clonogenic activity. Next, the proportion and number of hematopoietic stem cells (HSCs) were analyzed. Competitive repopulation experiments were conducted to assess the multilineage engraftment of irradiated HSCs after BM transplantation. Flow cytometry was used to evaluate DNA damage, cell apoptosis, and cell cycle stage in HSCs after irradiation. Finally, we evaluated the efficacy of a single dose of rhTPO administered after 7 Gy TBI in male and female rhesus monkeys. RESULTS: A single administration of rhTPO 2 hours after irradiation significantly mitigated TBI-induced death in mice. rhTPO promoted multilineage hematopoietic recovery, increasing peripheral blood cell counts, BM cellularity, and BM colony-forming ability. rhTPO administration led to an accelerated recovery of BM HSC frequency and multilineage engraftment after transplantation. rhTPO treatment reduced radiation-induced DNA damage and apoptosis and promoted HSC proliferation after TBI. Notably, a single administration of rhTPO significantly promoted multilineage hematopoietic recovery and improved survival in nonhuman primates after TBI. CONCLUSIONS: These findings indicate that early intervention with a single administration of rhTPO may represent a promising and effective radiomitigative strategy for victims of radiation disasters.

Succinate ester derivative of δ-tocopherol enhances the protective effects against 60Co γ-ray-induced hematopoietic injury through granulocyte colony-stimulating factor induction in mice.

α-tocopherol succinate (α-TOS), γ-tocotrienol (GT3) and δ-tocotrienol (DT3) have drawn large attention due to their efficacy as radioprotective agents. α-TOS has been shown to act superior to α-tocopherol (α-TOH) in mice by reducing lethality following total body irradiation (TBI). Because α-TOS has been shown to act superior to α-tocopherol (α-TOH) in mice by reducing lethality following total body irradiation (TBI), we hypothesized succinate may be contribute to the radioprotection of α-TOS. To study the contributions of succinate and to identify stronger radioprotective agents, we synthesized α-, γ- and δ-TOS. Then, we evaluated their radioprotective effects and researched further mechanism of δ-TOS on hematological recovery post-irradiation. Our results demonstrated that the chemical group of succinate enhanced the effects of α-, γ- and δ-TOS upon radioprotection and granulocyte colony-stimulating factor (G-CSF) induction, and found δ-TOS a higher radioprotective efficacy at a lower dosage. We further found that treatment with δ-TOS ameliorated radiation-induced pancytopenia, augmenting cellular recovery in bone marrow and the colony forming ability of bone marrow cells in sublethal irradiated mice, thus promoting hematopoietic stem and progenitor cell recovery following irradiation exposure. δ-TOS appears to be an attractive radiation countermeasure without known toxicity, but further exploratory efficacy studies are still required.

Natural Product Vibsanin A Induces Differentiation of Myeloid Leukemia Cells through PKC Activation.

All-trans retinoic acid (ATRA)-based cell differentiation therapy has been successful in treating acute promyelocytic leukemia, a unique subtype of acute myeloid leukemia (AML). However, other subtypes of AML display resistance to ATRA-based treatment. In this study, we screened natural, plant-derived vibsane-type diterpenoids for their ability to induce differentiation of myeloid leukemia cells, discovering that vibsanin A potently induced differentiation of AML cell lines and primary blasts. The differentiation-inducing activity of vibsanin A was mediated through direct interaction with and activation of protein kinase C (PKC). Consistent with these findings, pharmacological blockade of PKC activity suppressed vibsanin A-induced differentiation. Mechanistically, vibsanin A-mediated activation of PKC led to induction of the ERK pathway and decreased c-Myc expression. In mouse xenograft models of AML, vibsanin A administration prolonged host survival and inhibited PKC-mediated inflammatory responses correlated with promotion of skin tumors in mice. Collectively, our results offer a preclinical proof of concept for vibsanin A as a myeloid differentiation-inducing compound, with potential application as an antileukemic agent. Cancer Res; 76(9); 2698-709. ©2016 AACR.

The protein kinase C agonist prostratin induces differentiation of human myeloid leukemia cells and enhances cellular differentiation by chemotherapeutic agents.

As acute myeloid leukemia (AML) cells are characterized by uncontrolled self-renewal and impaired cellular differentiation, induction of terminal differentiation of leukemia cells by differentiating agents has been proposed as an attractive therapeutic strategy to treat AML. Here, we demonstrated that prostratin, a potent protein kinase C (PKC) activator, inhibited the growth of myeloid leukemia cells by a predominant G1 arrest with variable induction of apoptosis. Conversely, prostratin induced significant differentiation of AML cell lines and primary AML blasts as evidenced by morphology and immunophenotyping. The effects of prostratin were PKC dependent, and activation of mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK) 1/2 by PKC was required for prostratin-induced cell differentiation. Consequently, prostratin reprogrammed transcriptional factor expression, and ectopic expression of c-Myc in HL-60 cells significantly eliminated prostratin-mediated cellular differentiation and cell cycle arrest, indicating an essential role for c-Myc suppression in the differentiation-inducing effects of prostratin. Finally, prostratin was able to potentiate cellular differentiation induced by chemotherapeutic agents such as Ara-C. Together, we proposed that prostratin alone or administered with other anticancer agents may be effective in differentiation therapy of AML.

[Identification of differentially expressed genes of acute hypoxia-treated HepG2 cells and hypoxia-acclimatized HepG2 cells].

To provide necessary information for further understanding of molecular mechanism of hypoxia acclimatization, the differentially expressed genes of HepG2 cells exposed to normoxia, acute hypoxia-treated cells which were exposed to 1% oxygen for 48 h, and hypoxia-acclimatized HepG2 cells which were cultured for 6 circles of alternate low oxygen (1% oxygen for 24 h) and normal oxygen (21% oxygen for 24 h), were identified respectively by combining the suppression subtractive hybridization (SSH) and cDNA microarray. Thirty-seven genes were expressed differentially in cells exposed to 1% oxygen for 48 h compared with those in cells exposed to normoxia. The expression of all these 37 genes was down-regulated, including the genes participating in cell cycle, cell response to stimulus, and cell signal transduction, and cell cytoskeleton formation, the genes associated with transcription and cell metabolism, 4 expressed sequence tags (ESTs), and 12 genes of which the functions are not known. There is a novel gene sequence, which has not been found in existing databases. There were only 6 genes differentially expressed in the hypoxia-acclimatized cells compared with cells exposed to normoxia, including two mitochondrion genes, metalloprotease-1 gene, ferritin gene, thymosin beta-4 and TPT1 genes. The expressions of mitochondrion ND4, ferritin, thymosin beta-4 and TPT1 were up-regulated, while the expressions of mitochondrion ND1 gene and metalloproease-1 gene were down-regulated. Cell tolerance to hypoxia increased after the cells were hypoxia-acclimatized. The different gene expression patterns of the acute hypoxia-treated cells and the hypoxia-acclimatized cells may be related to the increased tolerance of the cells to hypoxia.

[Study on the effect of vibsane-type diterpenoids of Viburnum odoratissimum on human HepG2 cell growth and its underlying mechanism].

OBJECTIVE: To study the antiproliferation effect on HepG2 cells and its underlying mechanism of the active chemical composition of the Viburnum Odoratissimum. METHODS: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction assay and trypan blue dye exclusion assay were used to assess the effect of vibsane-type diterpenoids on the proliferation of various tumor cells. Alterations in cell cycle and apoptosis were determined by flowcytometry. The enzymatic activity of caspase-3/7 was measured by Apo-ONE homogeneous Caspase-3/7 Assay kit. RESULTS: Compound 1 #, a vibsane-type diterpenoid, was found to significantly inhibit the growth of HepG2 cells by anticancer proliferation activity screening. It was demonstrated that the modified groups on side chain coupled to C11 site affected the cell growth-inhibition activity of compounds by structure-activity analysis. In addition, HepG2 cell line was most sensitive to compound 1 #, which induced growth arrest of HepG2 cells in a dose- and time-dependent manner. Study on the mechanisms underlying these effects indicated that compound 1 # induced significant G0/G1 phase arrest of HepG2 cells in a time- and concentration-dependent manner. Meanwhile, It was found that higher concentrations of compound (5-10 micromol/L) caused evident increase in the unmber of apoptotic cells and dose-dependent activation of caspase-3/7. CONCLUSION: Vibsane-type diterpenoids could significantly inhibit the growth of HCC HepG2 cells. Induction of cell cycle arrest and apoptosis may play important roles in their anticancer effects.

[Protective effects of WR2721 on early bone marrow hematopoietic function in mice exposed to 6.5 Gy of (60)Co γ-rays].

The aim of this study was to investigate the effect of WR2721(amifostine) against bone marrow hematopoietic damage of mice exposed to 6.5 Gy of (60)Co-γ ray. A total of 60 C57/BL6J mice was divided into 3 groups:normal group (mice were injected with physiological salt solution), irradiation group (mice were injected with physiologic salt solution before irradiation) and WR2721 group (mice were injected with WR2721 before irradiation). The WBC, neutrophil (Neut), Plt and RBC levels in peripheral blood of 3 group mice were counted within 60 days after irradiation; the bone marrow nuclear cells (BMNC) were counted at 2 and 24 hours after irradiation; the hematopoietic stem/progenitor cell (LK/LSK) level and colony formation capability were detected by flow cytometry at 2 and 24 hours after irradiation. The results indicated that the counts of WBC and neut at 4 and 18 days, Plt at 7-18 days and RBC at 10-30 day after irradiation in WR2721 group were higher than those in irradiation group (P < 0.05); the BMNC, LSK and LK levels obviously increased at 24 hours after irradiation (P < 0.05), the CFU-GEMM, CFU-GM, CFU-MK BFU-E and CFU-E all significantly increased at 2 and 24 hours after irradiation (P < 0.01), as compared with irradiation group. It is concluded that WR2721 can effectively alleviate early hematopoietic damage and promote the fast recovery of peripheral blood cells in mice exposed to γ-ray, suggesting that the WR2721 has significant radioprotective effect on hematopoietic system.

High dose granulocyte colony-stimulating factor enhances survival and hematopoietic reconstruction in canines irradiated by 2.3 Gy mixed fission neutron and gamma ray.

This study was purposed to evaluate the effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on hematopoietic reconstruction and survival in beagles exposed to mixed fission neutron and γ-ray. 13 beagles were unilaterally exposed to single dose of 2.3 Gy 90% neutrons. The experiments were divided into 3 groups: irradiation control group (no any treatment, n = 4), supportive care group (n = 5) and rhG-CSF plus supportive care group (n = 4, abbreviated as rhG-CSF group) in which the beagles were subcutaneously injected with 200 µg/kg of rhG-CSF early at half an hour and 24 hours post-irradiation respectively. The results showed that 2.3 Gy 90% neutron irradiation induced a severe acute radiation sickness of bone marrow type. The administration of rhG-CSF increased the survival rate from 60% in supportive care group to 100%. Twice injection of rhG-CSF in the first 24 hours reduced duration of neutropenia, enhanced neutrophil nadir and promoted neutrophil recovery when compared with control cohort administered clinical support. The number of colony-forming cells (CFU-GM, CFU-E, and BFU-E) in peripheral blood of rhG-CSF treated canines increased 2-to 5-fold relative to those of the supportive care group on day 3. All canines treated with rhG-CSF achieved hematopoietic reconstruction as evidenced by the pathological section of sternum while severe shortage of hemopoietic cells remained in the cohorts given supportive care alone. It is concluded that the combination of supportive care and high-dose rhG-CSF can accelerate hematopoietic recovery and enhance survival of dogs exposed to 2.3 Gy mixed neutron and gamma ray.

RhG-CSF improves radiation-induced myelosuppression and survival in the canine exposed to fission neutron irradiation.

Fission-neutron radiation damage is hard to treat due to its critical injuries to hematopoietic and gastrointestinal systems, and so far few data are available on the therapeutic measures for neutron-radiation syndrome. This study was designed to test the effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in dogs which had received 2.3 Gy mixed fission-neutron-γ irradiation with a high ratio of neutrons (~90%). Following irradiation, rhG-CSF treatment induced 100% survival versus 60% in controls. Only two of five rhG-CSF-treated dogs experienced leukopenia (white blood cells [WBC] count < 1.0 × 10(9)/L) and neutropenia (neutrophil [ANC] count < 0.5 × 10(9)/L), whereas all irradiated controls displayed a profound period of leukopenia and neutropenia. Furthermore, administration of rhG-CSF significantly delayed the onset of leukopenia and reduced the duration of leucopenia as compared with controls. In addition, individual dogs in the rhG-CSF-treated group exhibited evident differences in rhG-CSF responsiveness after neutron-irradiation. Finally, histopathological evaluation of the surviving dogs revealed that the incidence and severity of bone marrow, thymus and spleen damage decreased in rhG-CSF-treated dogs as compared with surviving controls. Thus, these results demonstrated that rhG-CSF administration enhanced recovery of myelopoiesis and survival after neutron-irradiation.

Structural requirement of spirostanol glycosides for rat uterine contractility and mode of their synergism.

OBJECTIVES: Total steroidal saponins extracted from the rhizome of Paris polyphylla (TSSP) have been used in China for the treatment of abnormal uterine bleeding. The aim of this study was to analyse the structure-activity relationship of steroidal saponins purified from P. polyphylla Sm. var. yunnanensis on rat myometrial contractions, and investigate the synergism among themselves as well as with known inherent agonists, such as Prostaglandin F(2alpha) (PGF-2alpha). METHODS: In this study, 22 steroidal saponins purified from TSSP were screened for their contractile activity in isolated uterine strips from estrogen-primed rats. KEY FINDINGS: It was shown that spirostanol glycosides exhibited inducible or inhibitory activity in rat uterine contraction based on the difference of their structures, which was not only attributed in part to the number, the length and the position of sugar side chains attached by a glycoside, but also related to the structure of the aglycone. Furthermore, synergistic actions were observed among pennogenin or diosgenin glycosides as well as with the known inherent agonist PGF-2alpha, indicating they may share, at least in part, similar pathways with PGF-2alpha in stimulating myometrial contractions. Finally, the contractile response of rat myometrium to spirostanol glycosides was significantly enhanced with advancing pregnancy. CONCLUSIONS: Together, these data support the possibility that some spirostanol glycosides may represent a new type of contractile agonist for the uterus and their synergism may be responsible for the therapeutic effect of TSSP on abnormal uterine bleeding.

Melissoidesin G, a diterpenoid purified from Isodon melissoides, induces leukemic-cell apoptosis through induction of redox imbalance and exhibits synergy with other anticancer agents.

Melissoidesin G (MOG) is a new diterpenoid purified from Isodon melissoides, a plant used in Chinese traditional medicine as antitumor and anti-inflammatory agents. In our study, MOG was shown to specifically inhibit the growth of human leukemia cell lines and primary acute myeloid leukemia (AML) blasts via induction of apoptosis, with the evidence of mitochondrial DeltaPsim loss, reactive oxygen species production, caspases activation and nuclear fragmentation. Furthermore, it was shown that thiol-containing antioxidants completely blocked MOG-induced mitochondrial DeltaPsim loss and subsequent cell apoptosis, while the inhibition of apoptosis by benzyloxy-carbonyl-Val-Ala-Asp-fluoromethylketone only partially attenuated mitochondrial DeltaPsim loss, indicating that MOG-induced redox imbalance is an early event upstream to mitochondrial DeltaPsim loss and caspase-3 activation. Consistently, it was found that MOG rapidly decreased the intracellular glutathione (GSH) content in a dose-dependent manner and the significance of GSH depletion in MOG-induced apoptosis was further supported by the protective effects of tert-butylhydroquinone (tBHQ) and the facilitative effects of DL-buthionine (S,R)-sulfoximine (BSO). Furthermore, it was showed that GSH depletion induced by MOG rendered some leukemia cell lines more sensitive to arsenic trioxide (As2O3), doxorubicin or cisplatin. Additionally, the synergistic apoptotic effects of MOG with As2O3 were detected in HL-60 and primary AML cells, but not in normal cells, suggesting the selective toxicity of their combination to the malignant cells. Together, we proposed that MOG alone or administered with other anticancer agents may provide a novel therapeutic strategy for leukemia.

Molecular cloning and characterization of cDNA encoding fibrinolytic enzyme-3 from earthworm Eisenia foetida.

The earthworm fibrinolytic enzyme-3 (EFE-3, GenBank accession No: AY438622), from the earthworm Eisenia foetida, is a component of earthworm fibrinolytic enzymes. In this study, cDNA encoding the EFE-3 was cloned by RT-PCR. The cDNA contained an open reading frame of 741 nucleotides, which encoded a deduced protein of 247 amino acid residues, including signal sequences. EFE-3 showed a high degree of homology to earthworm (Lumbricus rebullus) proteases F-III-1, F-III-2, and bovine trypsin. The recombinant EFE-3 was expressed in E. coli as inclusion bodies, and the gene encoding the native form of EFE-3 was expressed in COS-7 cells in the medium. Both the refolding product of inclusion bodies and the secreted protease could dissolve the artificial fibrin plate.