Identification of the post-polyketide synthase modification enzymes for fostriecin biosynthesis in Streptomyces pulveraceus.

Fostriecin (FST, 1) is a natural product with promising antitumor activity produced by Streptomyces pulveraceus. Its antitumor activity is associated with the selective inhibition of protein phosphatase activities. The biosynthetic gene cluster for FST has recently been cloned and sequenced. To better understand the post-polyketide synthase (PKS) modification steps in the biosynthetic pathway of FST, we constructed and characterized three post-PKS modification gene mutants of fosG, fosK, and fosM by knockout inactivation in S. pulveraceus. As a result, we determined that a fosK-encoded cytochrome P450 monooxygenase is responsible for C-18 hydroxylation, formation of an unsaturated lactone is dependent upon FosM, and the fosG gene product is involved in hydroxylation at C-4 after the action of FosM to yield PD 113,271 from FST. The accumulated analogues from the ΔfosK and ΔfosM mutant strains possessed a malonyl ester moiety that suggested that all the post-PKS modification steps in FST biosynthesis occur with the polyketide chain bearing a malonyl ester at the C-3 position, with formation of the unsaturated six-membered lactone as the last step in FST biosynthesis.

[Role of Ca2+-NFAT Signaling Pathway in Ph+ ALL Drug-resistance Mediated by Bone Marrow Stromal Cells].

OBJECTIVE: To explore the role of Ca2+-NFAT signaling pathway in Ph+-ALL drug resistance mediated by bone marrow stromal cells. METHODS: The transcription level of NFAT mRNA in Sup-B15 cells and Ph+ ALL primary cells was detected by polymerase chain reaction. The expression of P-glycoprotein in Sup-B15 cells was detected by flow cytometry. The change of NFAT protein in Sup-B15 cells was detected by Western blot. AnnexinV/7-AAD was used to label cells. Flow cytometry was used to detect cell apoptosis; Fluo 3-AM dye was used to label cells, and flow cytometry used to detect changes of Ca2+ concentration in leukemia cells. RESULTS: NFAT expression could be detected in both Sup-B15 and Ph+ ALL primary cells; P-glycoprotein could not be detected by flow cytometry; CAS could significantly inhibit NFAT protein expression in clinically applied drug concentrations (2.5, 5 µmol/L); Clinically applied concentration of CAS (2.5, 5 µmol / L) has no significant effect on the apoptosis of Sup-B15 cells, while higher concentration of CAS (10 µmol / L) could induce apoptosis of Sup-B15 cells. Bone marrow stromal cells OP9 could, decrease the sensitivity of Sup-B15 cells and Ph+ ALL primary cells to imatinib (IM); After co-culture with bone were marrow stromal cells, the Ca2+ concentration in Sup-B15 cells was enhanced, the levels of NFAT protein and nullear protein in sup-B15 cells also were enhanced. The addition of CAS in co-culture system could inlibit the Ca2+-NFAT signaling pathway, reduce the protective effect of OP9 on Sup-B15 cells.Conclution:The Ca2+-NFAT sigualing pathway, contributes to the survival of Ph+ ALL cells. Bone marrow stromal cells can mediate the resistance of Ph+ ALL cells to IM by activating Ca2+-NFAT signaling pathway.

[Statins Regulate the Proliferation and Apoptosis of T-ALL Cells through the Inhibition of Akt Pathway].

OBJECTIVE: To investigate the effect of Statins on proliferation and apoptosis in human acute T lymphocytic leukemia (T-ALL) cells and its possible mechanism. METHODS: Jurkat and CCRF-CEM cells were cultured in different concentrations of Fluvastatin and Simvastatin for 24 h respectively. Then, the cell growth inhibition level was defected by CCK-8; the DNA replication was analyzed by EdU; the cell apoptosis was analyzed by Annexin V/7-AAD double labeling; the cell cycle changes were analyzed by flow cytometry; the expressions of Cyclin D1, p21, p27, BAX, BCL-2 and p-Akt were determined by Western blot. RESULTS: Fluvastatin and Simvastatin both significantly inhibited the growth of Jurkat and CCRF-CEM cells in a dose-dependent manner. The inhibitory rate of Jurkat and CCRF-CEM cells at 0.2 mmol/L Fluvastatin was 41.14% and 57.08% respectively, while the 0.2 mmol/L Simvastatin could supress 68.42% of Jurkat and 77.10% of CCRF-CEM cells. Half or more than half of cell inhibition were observed in Statins-treated groups with significantly statistical differences, compared with the control groups (P<0.05). After the Jurkat and CCRF-CEM cells were treated with Fluvastation and Simvastation of different concentrations for 24 hours, the proportion of early and later apoptotic cells both increased; moreover, the total apoptotic rate increased significantly(P<0.05) at 0.2 mmol/L and 0.3 mmol/L concentration of Fluvastatin and Simvastatin. The detection of cell cycle showed that both of Jurkat and CCRF-CEM cells were arrested in G1 phase. Western blot revealed that, in comparison with the control group, the expressions of BAX, p21 and p27 in cells treated with Statins were up-regulated, while Cyclin D1, BCL-2 and p-Akt expressions were down-regulated. CONCLUSION: Statins can suppress T-ALL cell proliferation and induce cell apoptosis through the inhibition of Akt pathway.

CUEDC2, a novel interacting partner of the SOCS1 protein, plays important roles in the leukaemogenesis of acute myeloid leukaemia.

Downregulation of suppressor of cytokine signalling-1 (SOCS1) is one of the vital reasons for JAK1-STAT3 pathway activation in acute myeloid leukaemia (AML). CUE domain-containing 2 (CUEDC2) was a novel interacting partner of SOCS1 and a positive correlation between the expression of CUEDC2 and SOCS1 was confirmed in primary AML cells and AML cell lines without SOCS1 promoter methylation. We aimed to explore roles of CUEDC2 in regulating ubiquitin-mediated degradation of SOCS1 in the leukaemogenesis of AML.According to in vitro experiments, CUEDC2 overexpression increased the level of SOCS1 protein, suppressed JAK1-STAT3 pathway activation. The suppression of this pathway inhibited AML cells' proliferation by causing G1 arrest and enhanced AML cells' sensitivity to cytarabine and idarubicin. Similarity, downregulation of CUEDC2 produced opposite results. Knockout or low expression of CUEDC2 in mouse or AML patients displayed lower overall survival and event-free survival rates, compared with these mouse and AML patients had high-CUEDC2 expression. Mechanistic studies revealed that CUEDC2 overexpression attenuated SOCS1 ubiquitination, facilitated its stabilisation by enhancing SOCS1, Elongin C and Cullin-2 (CUL2) interactions, thus inhibited JAK1-STAT3 pathway and leukaemogenesis of AML. Therefore, our novel findings indicated that CUEDC2 interacted with SOCS1 to suppress SOCS1's ubiquitin-mediated degradation, JAK1-STAT3 pathway activation and leukaemogenesis of AML.

Homoharringtonine combined with aclarubicin and cytarabine synergistically induces apoptosis in t(8;21) leukemia cells and triggers caspase-3-mediated cleavage of the AML1-ETO oncoprotein.

Homoharringtonine combined with aclarubicin and cytarabine (HAA) is a highly effective treatment for acute myeloid leukemia (AML), especially for t(8;21) AML. However, the underlying mechanisms by which HAA kills t(8;21) AML cells remain unclear. In this study, SKNO-1 and Kasumi-1 cells with t(8;21) were used. Compared with individual or pairwise administration of homoharringtonine, aclarubicin, or cytarabine, HAA showed the strongest inhibition of growth and induction of apoptosis in SKNO-1 and Kasumi-1 cells. HAA caused cleavage of the AML1-ETO (AE) oncoprotein to form truncated AE (ΔAE). Pretreatment with the caspase-3 inhibitor caspase-3 inhibitor Q-DEVD-OPh (QDO) not only suppressed HAA-induced apoptosis but also abrogated the cleavage of AE and generation of ΔAE. These results suggest that HAA synergistically induces apoptosis in t(8;21) leukemia cells and triggers caspase-3-mediated cleavage of the AML1-ETO oncoprotein, thus providing direct evidence for the strong activity of HAA toward t(8;21) AML.

[Effect of Alantolactone on Proliferation of RPMI-8226 Cells and Its Possible Mechnism].

OBJECTIVE: To investigate the effect of alantolactone on perliferation and apoptosis of multiple myeloma (MM) RPMI-8226 cells, and to explore its possible mechism in vitro and in vivo. METHODS: The RPMI-8226 cells were treated with alantolactone (1, 2.5, 5, 7.5 and 10 µmol/L) for 48 h, cell viability was detected by CCK-8 assay and the value of IC50 was calculated; The RPMI-8226 cells were treated with alantolactone (2.5, 5 and 7.5 µmol/L) for 48 h, the apoptotic rate was detected by flow cytmetry with Annexin V/PI staining; the expression level of cleaved caspase-3 and phosphorylation of ERK were measured by Western blot; the nude mice was used to further confirm the proapoptotic effect of alantolactone on MM cells in vivo. RESULTS: The alantolactone inhibited RPMI-8226 cell viability remarkably with a dose-dependent manner; the IC50 value of RPMI-8226 cells at 48 h was 4.32 ± 0.15 µmol/L; the apoptotic rate increased observably with a dose-dependent manner; the levels of cleaved-caspase-3 increased and the phosphorylation of ERK decreased significantly; as compared to control, the volum of tumor was much smaller, the expression levels of Ki67 and p-ERK decreased. CONCLUSION: The alantolactone can efficiently inhibit the proliferation and induce the apoptosis of multiple myeloma RPMI-8226 cells in vitro and in vivo through inhibiting the activation of ERK signal pathway.

Antithymocyte globulin combined with cyclosporine A down-regulates T helper 1 cells by modulating T cell immune response cDNA 7 in aplastic anemia.

Antithymocyte globulin (ATG) combined with cyclosporine A (CsA) has been widely used as a standard regimen in the treatment of aplastic anemia (AA), especially in severe aplastic anemia (SAA). Abnormally activated T cells might be the immune pathogenesis of AA. T cell immune response cDNA 7 (TIRC7) has been demonstrated its essential role in T cell activation; however, little is known about the role of TIRC7 in AA. In this study, we documented that TIRC7 levels in CsA group were higher than that in ATG + CsA (AC) group only in the follow-up phase (P < 0.05; P < 0.05); nevertheless, TIRC7 levels in SAA group were elevated than non severe aplastic anemia group not only in the treatment phase (P < 0.05; P < 0.05) but also in the follow-up phase (P < 0.05; P < 0.01). The trend of changes of T helper (Th) 1, Th17 and Th22 levels before and after treatment was similar to the changes of TIRC7 levels in either AC group or CsA group. Thus, TIRC7 might be involved in the pathogenesis of AA and AC might down-regulate Th1 cells by modulating the expression of TIRC7 in AA.

[Effect of AZD8330 on proliferation and apoptosis of multiple myeloma cells].

This study was aimed to investigate the effect of MEK inhibitor AZD8330 on proliferation and apoptosis of multiple myeloma IM9 and NCI-H929 cell lines and its possible mechanism. These two cell line cells were exposed to different concentrations of AZD8330 for 48 h. The CCK-8 assay was used to detect cell viability and the IC50 value at 48 h. These above-mentioned IM9 and NCI-H929 cells were treated with 5,10 and 100 nmol/L of AZD8330, then the change of cell cycle was analysed by flow cytometry with PI staining. The Wester blot was used to detect the expression levels of cyclin D and cyclin E, and multiple myeloma cells were treated with 10, 100, 1000 and 2000 nmol/L of AZD8330, the AnnexinV/7-AAD double staining was used to analyse cell apoptosis and the Western blot was used to detect the expression level of caspase-3. The results showed that AZD8330 could significantly inhibit the cell viability of IM9 and NCI-H929 cell lines in a time-and dose-dependent manner, the IC50 value (48 h) of IM9 and NCI-H929 were 19.88 ± 2.7 nmol/L and 29.3 ± 2.03 nmol/L respectively, these two cell lines were arrested on G1 phase of cell cycle, the apoptosis cells increased along with enhancement of AZD8330 concentration, and the expression level of cleaved caspase-3 protein was up-regulated. It is concluded that AZD8330 can efficiently inhibit the proliferation of NCI-H929 and IM9 cell lines, and induce apoptosis, suggesting that the AZD8330 may be a potential chemotherapeutic candidate for multiple myeloma therapy.