OBJECTIVETo elucidate the roles of JAK/STATs signal pathway on anti-proliferative effects induced by IFN-alpha in MHCC97.

METHODSAn IRF9 expression vector was transfected into MHCC97 with Dosper. The expression of IRF9, cycle regulating proteins and the forming of ISGF3 complex were detected using Western blot and EMSA, respectively. Cell proliferation and distribution were monitored using MTT and flow cytometry.

RESULTSHigh expression of IRF9 restored the anti-proliferative response of MHCC97 on IFN-alpha treatment and delayed the cell transition from S phase to G2 phase induced by IFN-alpha.

CONCLUSIONThe integrity and functions of JAK/STATs signal pathway played an important role in mediating the anti-proliferative effects of IFN-alpha in MHCC97.

Carcinoma, Hepatocellular ; genetics ; metabolism ; pathology ; Cell Line, Tumor ; Cell Proliferation ; Humans ; Interferon-Stimulated Gene Factor 3, gamma Subunit ; genetics ; Interferon-alpha ; metabolism ; pharmacology ; Janus Kinases ; genetics ; physiology ; Liver Neoplasms ; genetics ; metabolism ; pathology ; STAT Transcription Factors ; genetics ; physiology ; Signal Transduction ; Transfection

Objective: To investigate the prognostic significance of interferon regulatory factor 9 (IRF9) expression and identify its role as a potential therapeutic target in acute promyelocytic leukemia (APL) . Methods: The gene expression profile and survival data applied in the bioinformatic analysis were obtained from The Cancer Genome Atlas and Beat acute myeloid leukemia (AML) cohorts. A dox-induced lentiviral system was used to induce the expression of PML-RARα (PR) in U937 cells, and the expression level of IRF9 in U937 cells treated with or without ATRA was examined. We then induced the expression of IRF9 in NB4, a promyelocytic leukemia cell line. In vitro studies focused on leukemic phenotypes triggered by IRF9 expression. Results: ①Bioinformatic analysis of the public database demonstrated the lowest expression of IRF9 in APL among all subtypes of AML, with lower expression associated with worse prognosis. ②We successfully established a PR-expression-inducible U937 cell line and found that IRF9 was downregulated by the PR fusion gene in APL, with undetectable expression in NB4 promyelocytic cells. ③An IRF9-inducible NB4 cell line was successfully established. The inducible expression of IRF9 promoted the differentiation of NB4 cells and had a synergistic effect with lower doses of ATRA. In addition, the inducible expression of IRF9 significantly reduced the colony formation capacity of NB4 cells. Conclusion: In this study, we found that the inducible expression of PR downregulates IRF9 and can be reversed by ATRA, suggesting a specific regulatory relationship between IRF9 and the PR fusion gene. The induction of IRF9 expression in NB4 cells can promote cell differentiation as well as reduce the colony forming ability of leukemia cells, implying an anti-leukemia effect for IRF9, which lays a biological foundation for IRF9 as a potential target for the treatment of APL.
Cell Differentiation ; Humans ; Interferon-Stimulated Gene Factor 3, gamma Subunit/metabolism* ; Leukemia, Myeloid, Acute/drug therapy* ; Leukemia, Promyelocytic, Acute/genetics* ; Oncogene Proteins, Fusion/metabolism* ; Phenotype ; Tretinoin/therapeutic use* ; U937 Cells

OBJECTIVETo study the mechanism of signal transduction in anti-HBV action of IFN-alpha.

METHODSThe HBV DNA in HepG 2.2.15 cell line supernatant with/without IFNalpha-2b were monitored by fluorescence real-time quantitive PCR. STAT1, STAT2, ISGF3-gamma, PKR, 2'5'-OAS mRNA levels from HepG 2 and HepG 2.2.15 cell lines that were treated with/without IFNalpha-2b at different times were detected by semi-quantitive RT-PCR. And the ISGF3-gamma protein was detected by Western blot. Then, these items were detected again after inhibiting the JAK-STAT pathway with genistein.

RESULTSThe HBV DNA in 2215 supernatant that were treated with IFNalpha-2b for 8 hours decreased 0.72 log 10 copies/ml. But the basal levels of DNA in cells pretreated with genistein? followed by IFNalpha-2b did not decrease. The STAT1, STAT2, ISGF3-gamma, 2'5'-OAS, PKR mRNA levels were upregulated by IFNalpha-2b. The same phenomena were observed with STAT1, STAT2, ISGF3-gamma mRNA when pretreated with genistein then treated with IFNalpha-2b, but the levels of 2'5'-OAS, PKR mRNA were decreased in this situation. The expression of the protein of ISGF3-gamma was also augmented by IFNalpha-2b, and was blocked by genistein.

CONCLUSIONThe JAK-STAT pathway seems to be a critical pathway in IFNalpha-2b action against HBV? and ISGF3 is most probably a key factor of the route.

Antiviral Agents ; pharmacology ; Blotting, Western ; Cell Line, Tumor ; DNA, Viral ; genetics ; isolation & purification ; Gene Expression Regulation, Neoplastic ; drug effects ; Hepatitis B virus ; drug effects ; genetics ; growth & development ; Humans ; Interferon-Stimulated Gene Factor 3 ; genetics ; metabolism ; Interferon-Stimulated Gene Factor 3, gamma Subunit ; genetics ; metabolism ; Interferon-alpha ; pharmacology ; Polymerase Chain Reaction ; RNA, Messenger ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; STAT1 Transcription Factor ; genetics ; metabolism ; STAT2 Transcription Factor ; genetics ; metabolism ; Signal Transduction

OBJECTIVETo investigate the molecular mechanisms by which IFN-alpha regulated retinoic acid-induced gene G (RIG-G) expression.

METHODSThe expression of STAT1, p-STAT1 and RIG-G in IFN-alpha-treated NB4 cells was detected by Western blot. The roles of STAT1, STAT2 and IRF-9 in IFN-alpha-induced RIG-G expression were analyzed in STAT1-null U3A cells by cell transfection, reporter gene assay, co-immunoprecipitation and chromatin immunoprecipitaion.

RESULTSIn U3A cells, only when STAT2 and IRF-9 were co-transfected, the luciferase activities of RIG-G promoter-containing reporter gene could be highly increased about 8-fold compared with that in the control group. Moreover, in the absence of IFN-alpha, similar effects were observed in either IRF-9 co-transfected with wild type or mutant form of STAT2, whereas IFN-alpha could increase the transactivation activity of wild type STAT2 and IRF-9 by 6-fold compared with that without IFN-alpha, but had no effect on mutant STAT2. In addition, STAT2 could interact with IRF-9 and bind to the RIG-G promoter.

CONCLUSIONSTAT2 may interact with IRF-9 in a STAT1-independent manner. The complex STAT2/IRF-9 is the key factor mediating the expression of RIG-G gene regulated by IFN-alpha. This is a novel signal transduction cascade for IFN which is different from the classical JAK-STAT pathway.

Cell Line, Tumor ; Fibrosarcoma ; metabolism ; pathology ; Gene Expression Regulation, Neoplastic ; Humans ; Immunoprecipitation ; Interferon-Stimulated Gene Factor 3, gamma Subunit ; genetics ; metabolism ; Interferon-alpha ; pharmacology ; Intracellular Signaling Peptides and Proteins ; genetics ; metabolism ; Leukemia, Promyelocytic, Acute ; metabolism ; pathology ; Phosphorylation ; Plasmids ; STAT1 Transcription Factor ; genetics ; metabolism ; STAT2 Transcription Factor ; genetics ; metabolism ; Signal Transduction ; Transfection

To investigate the molecular mechanisms of all-trans retinoic acid (ATRA)-induced rig-g gene expression and to better understand the signal transduction of ATRA during acute promyelocytic leukemia (APL) cell differentiation, the luciferase reporter assay, co-immunoprecipitation and chromatin immunoprecipitation were used to clarify the basic transcriptional factors, which directly initiated the expression of rig-g gene. The results showed that the expression of STAT2, IRF-9 and IRF-1 could be upregulated by ATRA with different kinetics in NB4 cells. IRF-9 was able to interact with STAT2 to form a complex, which could bind the rig-g gene promoter and trigger the rig-g expression. IRF-1 alone could also activate the reporter gene containing rig-g gene promoter, but C/EBPalpha could strongly inhibit this transcription activity of IRF-1. It is concluded that during ATRA-induced APL cell differentiation, IRF-1 is first upregulated by ATRA, and then IRF-1 increases the protein levels of IRF-9 and STAT2 with the downregulation of C/EBPalpha. The complex of IRF-9 and STAT2 is the primary transcriptional factor for rig-g gene induction. This study will be helpful for better understanding the signal transduction networks of ATRA during the course of APL cell differentiation.
CCAAT-Enhancer-Binding Protein-alpha ; metabolism ; Gene Expression Regulation, Leukemic ; drug effects ; Genes, Regulator ; drug effects ; Humans ; Interferon Regulatory Factor-1 ; metabolism ; Interferon-Stimulated Gene Factor 3, gamma Subunit ; metabolism ; Intracellular Signaling Peptides and Proteins ; genetics ; Leukemia, Promyelocytic, Acute ; genetics ; STAT2 Transcription Factor ; metabolism ; Signal Transduction ; Tretinoin ; pharmacology ; Tumor Cells, Cultured