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@# Objective: To investigate the correlation between the expression of E2F1 and growth arrest and DNA damage inducible protein 45g (GADD45g) in patients with acute myeloid leukemia (AML), and to explore whether GADD45g exerts its induction of DNA damage, cell apoptosis, senescence, cell cycle arrest and drug sensitivity in AML through inhibition of E2F1. Methods: A total of 32 cases of bone marrow specimens from patients initially diagnosed asAML in Hospital of Blood DiseasesAffiliated to ChineseAcademy of Medical Sciences from January 2013 to December 2016, were selected for this study; In addition, AML cell lines (U937, HL60, THP-1, Molm-13) were also collected for this study. The mRNAexpression of GADD45g and E2F1 in above mentioned specimens and cell lines by qPCR,andtheircorrelationwasalsoanalyzed.Thelentiviral vector over-expressing E2F1 (pLV-E2F1-RFP) was constructed to prepare recombinant lentivirus, which was then transfected Molm-13 and THP-1 cells that over-expressing GADD45g. Whether GADD45g exerts tumor inhibition effect on AML cells through inhibition of E2F1 was determined by comet assay, Annexin V/7AAD flow cytometry, β-galactosidase staining and PI staining flow cytometry etc. Results: The mRNA expression of GADD45g was negatively correlated with E2F1 in bone marrow of AML patients and AML cell lines (r=–0.663, P<0.01). Over-expression of GADD45g significantly inhibited the expression of E2F1 in AML cell lines (all P<0.01). Molm-13 and THP-1 cells that simultaneously over-expressing GADD45g and E2F1 were successfully constructed. Compared with the control group, the protein expressions of GADD45g and E2F1 in over-expression groups were significantly increased (all P<0.01). Compared with cells over-expressing GADD45g alone, simultaneous over-expression of both GADD45g and E2F1 significantly reduced the apoptosis, senescence and DNA damage (all P< 0.01), and rescued cell cycle arrest in Molm-13 and THP-1 cells (all P<0.01), thus further reduced the chemo-sensitivity of AML cells caused by GADD45g over-expression (all P<0.01). Conclusion: GADD45g exerts anti-tumor effect inAMLvia inhibition of E2F1.
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@#[Abstract] Objective: To quantify the expression of growth arrest and DNA damage inducible protein 45g (GADD45g) gene in the bone marrow samples of patients withAML (acute myeloid leukemia) and inAML cell lines, as well as to study the correlation between the GADD45g expression and prognostic outcome in patients withAML and investigate the role of GADD45g over-expression in proliferation, apoptosis, senescence, differentiation, cell cycle arrest, and drug sensitivity in AML cell lines. Methods: In the study, a total of 27 cases of bone marrow specimens were selected from patients initially diagnosed as AML in Hospital of Blood Diseases affiliated to Chinese Academy of Medical Sciences from January 2013 to December 2016. mRNA and protein expression levels of GADD45g in BMMNCs (Bone marrow mononuclear cells) from patients with AML and healthy donors and in AML cell lines were quantified by quantitative real-time PCR and Western blotting. The correlation between GADD45g expression and overall survival (OS), coupled with event-free survival (EFS) in patients with AML was analyzed in two gene expression datasets (GSE10358, GSE425-GPL317). Lentiviral vectors over-expressing GADD45g were constructed and transfected into AML cell lines (U937, THP-1 and Molm-13 cell lines). The role of GADD45g over-expression in cell proliferation, colony formation, senescence, apoptosis, cell cycle arrest, differentiation and drug sensitivity of U937, THP-1 and Molm-13 cells were detected by cell counting, colony-forming assay, β-galactosidase staining and flow cytometric analysis of Annexin V/7AAD staining, PI staining and so on, respectively. Results: Expression of GADD45g was dramatically down-regulated in BMMNCs in AML patients and AML cell lines compared to that from healthy donors (all P<0.01). The OS (P<0.05) and EFS (P<0.05) of AML patients with low GADD45g expression were significantly shorter that those of AML patients with higher GADD45g level. Enforced expression of GADD45g could inhibit cell growth and colony formation, promote senescence and apoptosis, induce cell cycle arrest and differentiation and enhance drug sensitivity in AML cell lines (P<0.05 or P<0.01). Conclusion: GADD45g expression was remarkably silenced in marrow tissues of patients withAML andAML cell lines; it showed remarkable and all-around inhibiting effect onAMLcell lines, indicating that GADD45g expression has prognostic value inAML.
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Objective: To investigate the effect of Gadd45G (growth arrest and DNA-damage-inducible 45 gamma) overexpression on cell proliferation of colon cancer cells and the possible related mechanism. Methods: To explore whether Gadd45G functions in regulating cell proliferation of colon cancer cells, a lentiviral Tet (tetracycline)-inducible expression system was used for ectopic Gadd45G expression in colon cancer HCT116 and SW480 cells. The effects of Gadd45G over-expression on cell proliferation, cell cycle distribution, apoptosis and cellular senescence were analyzed by MTT method, FCM (flow cytometry) and senescence-associated beta-galactosidase assay, respectively. The expression of senescenceassociated secrete phenotype IL-8 (interleukin 8) and cell cycle-regulators were measured by RFQ-PCR (real-time fluorogenic quantitative-PCR) and Western blotting, respectively. Results: After doxycycline induction, Gadd45G expression was validated in HCT116 and SW480 cells. Gadd45G overexpression significantly inhibited the proliferation of HCT116 and SW480 cells (P < 0.001), and resulted in cell cycle arrest at G2/M phage. Intriguingly, Gadd45G over-expression efficiently elicited cellular senescence (P < 0.001) but not apoptosis. Moreover, the protein levels of cell cycle regulators p53, p21/CDKN1a, p16INK4a and Rb were not significantly altered in the colon cancer cells upon Gadd45G induction, while the expressions of IL-8 mRNA and senescence marker γ-H2A protein were significantly increased. Conclusion: The over-expression of stress sensor Gadd45G inhibits the proliferation of colon cancer cells through inducing cellular senescence. Copyright © 2013 by TUMOR.