[Effect of AML1-ETO fusion protein on the expression of BCL-2].

This study was aimed to investigate the effect of AML1-ETO fusion protein on the anti-apoptotic gene BCL-2 in leukemic cells and to explore its role in leukemogenesis. The apoptotic levels of U937-WT, U937-Mock and U937-A/E1-4 cells were examined by flow cytometry. And cleaved caspase-3 protein expression was detected by Western blot. BCL-2 gene expression both in AML1-ETO-expressing cells or U937 nonexpressing cells and in leukemia cells of AML patients with or without t(8;21) was assessed by quantitative PCR. The chromatin immunoprecipitation (ChIP)-based PCR was used to investigate the direct interaction between the AML1-ETO and BCL-2 promoter in AML1-ETO positive leukemia cell line. The results indicated that in U937-A/E cells but not in U937-WT or U937-Mock cells, apoptotic cells statistically significantly increased, and AML1-ETO expression also significantly enhanced activation of caspase-3. AML1-ETO-expressing cell subclones displayed significantly low levels of BCL-2 mRNA in comparison with the non-transfected U937. In primary bone marrow cells of acute myeloid leukemia containing AML1-ETO, levels of BCL-2 mRNA were markedly lower as compared with other acute myeloid leukemias lacking this translocation. The enriched regions in transfected cells were located within BCL-2 promoter. It is concluded that BCL-2 is the direct target gene of AML1-ETO. AML1-ETO can down-regulate the expression of BCL-2.

Rapamycin induces differentiation of glioma stem/progenitor cells by activating autophagy.

Glioma stem/progenitor cells (GSPCs) are considered to be responsible for the initiation, propagation, and recurrence of gliomas. The factors determining their differentiation remain poorly defined. Accumulating evidences indicate that alterations in autophagy may influence cell fate during mammalian development and differentiation. Here, we investigated the role of autophagy in GSPC differentiation. SU-2 cells were treated with rapamycin, 3-methyladenine (3-MA) plus rapamycin, E64d plus rapamycin, or untreated as control. SU-2 cell xenografts in nude mice were treated with rapamycin or 3-MA plus rapamycin, or untreated as control. Western blotting and immunocytochemistry showed up-regulation of microtubule-associated protein light chain-3 (LC3)-II in rapamycin-treated cells. The neurosphere formation rate and the number of cells in each neurosphere were significantly lower in the rapamycin treatment group than in other groups. Real-time PCR and immunocytochemistry showed down-regulation of stem/progenitor cell markers and up-regulation of differentiation markers in rapamycin-treated cells. Transmission electron microscopy revealed autophagy activation in rapamycin-treated tumor cells in mice. Immunohistochemistry revealed decreased Nestin-positive cells and increased GFAP-positive cells in rapamycin-treated tumor sections. These results indicate that rapamycin induces differentiation of GSPCs by activating autophagy.

[Inhibition of hypoxia-inducible factor-1 alpha in RPMI8226 myeloma cells results in reduced tumor growth in nude mice].

OBJECTIVE: To explore the influence of inhibition of hypoxia-inducible factor-1 alpha (HIF-1 alpha) by RNA interference (RNAi) on tumorigenesis of human myeloma cell line (HMCL) RPMI8226 cells in nude mice. METHOD: RNAi vector of HIF-1 alpha was constructed with commercial shRNA expression vector pSilencer 2. 1-U6 hygro. RT-PCR and western blot were used to detect HIF-1 alpha mRNA and protein expression respectively. Vascular endothelial growth factor (VEGF) secretion and cell cycle changes were detected by ELISA and flow cytometry respectively. Expression of target gene of HIF-1 alpha, VEGF and Glut-1 were tested under hypoxia condition. Tumorigenesis was observed after transfected cells were injected subcutaneously in nude mice. RESULTS: After interference, expression of HIF-1 alpha decreased significantly at both mRNA and protein level. Under normoxia condition, VEGF concentrations in HIF-la inhibited cells (RPMI8226-il and RPMI8226-i2) and non-inhibited cells (RPMI8226-c and RPMI8226) showed no differences. While under hypoxia condition, VEGF concentration in the above four cells was (506.0 +/- 53.2), (494.7 +/- 63.1), (984.4 +/- 61.9) and (938.2 +/- 62.2) pg/ml, respectively, being significantly lower in RPMI8226-il and RPMI8226-i2 cells than in RPMI8226-c and RPMI8226 cells (P <0.05). HIF-1 alpha interference was found to suppress the cells shift from S-phase to G1 induced by hypoxia. VEGF and Glut-1 expressions were markedly attenuated (P <0.05). The growth rate of HIF-1 alpha inhibition tumors in subcutaneous xenograft model decreased drastically. CONCLUSIONS: RNAi inhibits HIF-1 alpha expression. Reduced tumor growth by HIF-1 alpha inhibition may partly through inhibiton of angiogenesis and glycolysis metabolism.

[Effects of RNA interference targeting hypoxia-inducible factor-1alpha (HIF-1alpha) on chemosensitivity of leukemia K562 cells towards homoharringtonine].

BACKGROUND & OBJECTIVE: Hypoxia-inducible factor-1alpha (HIF-1alpha) is a key transcription factor under anoxic circumstances. Little is known about changes in biological characters of hematological malignancies, especially leukemia. This study was to explore the influence of RNA interference (RNAi) targeting HIF-1alpha on sensitivity of human chronic myelogeneous leukemia (CML) K562 cells towards homoharringtonine (HHT). METHODS: HIF-1alpha short hairpin RNA (shRNA) was constructed using pSilencer 2.1-U6 hygro vector and transfected into K562 cells. Positive clones were screened using hygromycin. After inhibition of HIF-1alpha, expressions of its target genes such as vascular endothelial growth factor (VEGF), glucose transporter-1 (Glut-1), phosphoglycerate kinase (PGK), and P-glycoprotein (P-gp) were detected by real-time reverse transcriptase polymerase chain reaction (RT-PCR). Sensitivity of K562 cells to HHT was detected by MTT assay. RESULTS: HIF-1alpha expression was inhibited at both mRNA and protein levels after transfection of RNAi HIF-1alpha, which subsequently caused a dramatic decrease in VEGF, Glut-1, PGK, and P-gp under hypoxic conditions. In addition, HIF-1alpha inhibition was found to increase drug sensitivity of K562 cells to HHT. CONCLUSION: HIF-1alpha inhibition may result in a decrease of genes related to angiogenesis and glycolysis metabolism and an increase of drug sensitivity to HHT in K562 cells.

Generation and characterization of antibody against paf1 complex in Drosophila melanogaster.

Paf1 complex was identified in yeast and characterized to function in transcription and its related events. We identified the Drosophila homological components of paf1, CDC73 and RTF1 of paf1 complex. The genes encoding Drosophila paf1, CDC73 and RTF1 were cloned and expressed. With the purified recombinant proteins of truncated components of paf1 complex, antibodies against the Drosophila paf1, CDC73 and RTF1 were generated. These antibodies have been shown to be able to detect the endogenous paf1 subunits as well as their human counterparts in the HeLa extract. On Drosophila polytene chromosomes, these antibodies have been demonstrated to locate the paf1 complex at actively transcribing sites, which co-localized with phosphorylated RNA polymerase II, indicating that paf1 complex in Drosophila is involved in transcription or the events coupling with transcription.