Ataxia telangiectasia mutated (ATM) kinase plays an essential role in the maintenance of genomic stability. ATM-deficient (ATM(-/-)) mice exhibit hematopoietic stem cell (HSC) dysfunction and a high incidence of lymphoma. Gadd45a controls cell cycle arrest, apoptosis and DNA repair, and is involved in the ATM-p53 mediated DNA damage response. However, the role of Gadd45a in regulating the functionality of ATM(-/-) HSCs is unknown. Here we report that Gadd45a deletion did not rescue the defects of T-cells and B-cells development in ATM(-/-) mice. Instead, ATM and Gadd45a double knockout (ATM(-/-) Gadd45a(-/-)) HSCs exhibited an aggravated defect in long-term self-renewal capacity compared to ATM(-/-) HSCs in HSC transplantation experiments. Further experiments revealed that the aggravated defect of ATM(-/-) Gadd45a(-/-) HSCs was due to a reduction of cell proliferation, associated with an accumulation of DNA damage and subsequent activation of DNA damage response including an up-regulation of p53-p21 signaling pathway. Additionally, ATM(-/-) Gadd45a(-/-) mice showed an increased incidence of hematopoietic malignancies, as well as an increased rate of metastasis than ATM(-/-) mice. In conclusion, Gadd45a deletion aggravated the DNA damage accumulation, which subsequently resulted in a further impaired self-renewal capacity and an increased malignant transformation in ATM(-/-) HSCs.
Animals ; Ataxia Telangiectasia Mutated Proteins ; genetics ; B-Lymphocytes ; pathology ; Cell Cycle Proteins ; genetics ; Cell Proliferation ; Cyclin-Dependent Kinase Inhibitor p21 ; metabolism ; DNA Damage ; Hematopoietic Stem Cell Transplantation ; Hematopoietic Stem Cells ; metabolism ; pathology ; Leukemia ; genetics ; pathology ; Lymphoma ; genetics ; pathology ; Mice, Knockout ; Neoplasm Metastasis ; Nuclear Proteins ; genetics ; T-Lymphocytes ; pathology ; Tumor Suppressor Protein p53 ; metabolism

Objective:To investigate the effects of matrine on proliferation, apoptosis and radiotherapy sensitivity of uveal melanoma cells.Methods:An animal experiment study. In vitro experiment: MuM2B cells of human choroidal melanoma were randomly divided into control group and matrine 0.25, 0.50, 1.00, 2.00 g/L groups. The cell morphology was observed by transmission electron microscope. Cell proliferation was detected by thiazole blue colorimetry. The mRNA and relative expression levels of CyclinD D (CyclinD), B lymphoblastoma-2 (Bcl-2) and Bcl2-associated X protein (Bax) were detected by real-time polymerase chain reaction and Western blot. In vivo experiment: BALB/C mice were injected with MuM2B cell suspension subcutaneously on the back of forelimb to prepare transplanted tumor model. After successful modeling, they were randomly divided into blank group and matrine treatment group with different concentrations. Mice in blank group were injected with phosphate buffer subcutaneously. Mice in different matrine treatment groups were injected with 15, 25, 50, 100 mg/kg matrine subcutaneously, respectively, for 7 consecutive days. The tumor was weighed and its volume was measured after the last administration. Single factor analysis of variance was used to compare different groups. The t test was used for pairwise comparison between groups. Results:In the control group, the cell structure was normal, the distribution was uniform, and no or rare nuclear pyknosis was seen. With the increase of matrine dosage, the nuclear pyretosis increased gradually and cell morphology changed obviously. Compared with the control group, the cell survival rate in 0.50, 1.00 and 2.00 g/L groups gradually decreased with matrine concentration increasing and treatment time prolongating, the relative expression levels of CyclinD and Bcl-2 mRNA and protein gradually decreased, and the relative expression levels of Bax mRNA and protein gradually increased. Under the same radiation dose X-ray irradiation, the cell survival rate of 0.50, 1.00 and 2.00 g/L groups gradually decreased, and the differences were statistically significant ( P<0.05). Compared with blank group, the tumor weight and volume of mice in different doses of matrine group were significantly decreased, and the differences were statistically significant ( P<0.05). Conclusion:Matrine can down-regulate the expression of CyclinD and Bcl-2, up-regulate the expression of Bax, promote the apoptosis of MuM2B human melanoma cells, inhibit cell proliferation, and enhance cell radiosensitivity.