Objective To create a mouse model of colorectal polyps with Apc-Kras-Cre gene mutations using the tamoxifen induction method.Methods Mice with Apc-Kras-Cre mutations were divided into four groups and injected intraperitoneally with different concentrations and dosages of tamoxifen for different durations,with group 1 injected with low dosage tamoxifen(5 mg/kg)for 1 day,group 2 injected with low dosage tamoxifen(5 mg/kg)for 3 days,group 3 injected with high dosage tamoxifen(50 mg/kg)for 1 day,group 4 injected with high dosage tamoxifen(50 mg/kg)for 3 days.C57BL/6J mice were used as a healthy control group and survival and changes in body weight were observed.All mice were euthanized 4 weeks post-tamoxifen induction and the colon length and number and size of intestinal polyps were observed.Histological changes in the intestinal tissue and polyps were detected by hematoxylin and eosin staining.Results The survival rate of male mice was higher(P＜0.001)and the morbidity rate of male mice was lower compared with female mice(P＜0.05).The survival rate differed significantly among the four groups(P＜0.01).All groups showed significant changes in body weight compared with the healthy control group(P＜0.001).There were also significant differences in weight changes between tamoxifen-induced groups 1 and 2,between groups 2 and 3,and between groups 1 and 4(P＜0.001,P＜0.01,P＜0.05,respectively).There were no significant differences in colon length between any treated group and the healthy control group(P＞0.05),but colon length did differ between tamoxifen-induced groups 1 and 3(P＜0.05).Polyp size varied in each group of tamoxifen-treated mice,with most polyps occuring at the distal end of the colon,while mice in groups 3 and 4 had more and larger polyps.Histopathological examination showed intestinal polyps with uneven and misaligned glandular and epithelial arrangements,a loosely-packed intestinal mucosal barrier,and irregularly-distributed crypts in tamoxifen-induced mice compared with the healthy control group,while mice in tamoxifen-induced groups 3 and 4 showed signs of inflammation and mice in group 4 showed necrosis of cells in some regions.Conclusions Tamoxifen-induced Apc-Kras-Cre model mice were successfully established,with the group 3 induction method being the most suitable.

OBJECTIVETo establish the ADAR1 (adenosine deaminase that act on RNA 1) knockout MLL-AF9 acute myeloid leukemia (AML) mouse model, and to preliminarily investigate the effects of ADAR1 deletion on the development of AML.

METHODSThe lineage⁻ (Lin⁻) cells of ER-CreADAR1(lox/lox) mice and their ADAR1(lox/lox) counterparts were enriched by magnetic activated cell sorting (MACS) and then transduced with retrovirus carrying MSCV- MLL/AF9-IRES-GFP fusion gene. The efficiency of transduction was detected by flow cytometry, and equal number of GFP⁺ cells were transplanted into lethally irradiated recipient mice. The recipient mice were treated with tamoxifen at 48 hours after transplantation to induce ADAR1 knockout and divided into following groups: experimental group (ER-Cre;ADAR1(lox/lox)+tamoxifen), control groups ((1)ER-Cre;ADAR1(lox/lox)+vechile, (2)ADAR1(lox/lox)+tamoxifen, (3)ADAR1(lox/lox)+vechile). The percentage of GFP⁺ cells in peripheral blood was examined at 10, 15 and 20 days respectively after transplantation and the survival of the recipient mice was observed. In vitro study, ER-Cre;ADAR1(lox/lox) and ADAR1(lox/lox) AML cells were cultured and the apoptosis rates of these cells 48 hours after 4-hydroxytamoxifen treatment were examined.

RESULTSThe ADAR1 deletion MLL-AF9 AML mouse model was successfully established. Deletion of ADAR1 could decrease the percentage of GFP⁺ cells in the peripheral blood and significantly prolong the survival rate of recipient mice（P<0.05）. In vitro study showed that the cultured total cell number, percentage of GFP⁺ cells decreased and the apoptosis rate of AML cells increased.

CONCLUSIONAblation of ADAR1 could delay the progression of AML in recipient mice. ADAR1 plays a critical role in the development and maintenance of murine MLL-AF9 AML.

Adenosine Deaminase ; Animals ; Apoptosis ; Disease Models, Animal ; Leukemia, Myeloid, Acute ; Mice ; Myeloid-Lymphoid Leukemia Protein ; Tamoxifen ; analogs & derivatives