[Effects of PIM1 Gene on Proliferation, Apoptosis and JAK2/STAT3 Signaling Pathway of Acute Myeloid Leukemia U937 Cells].

OBJECTIVE: To investigate the effects of the serine/threonine kinase family member 1 (PIM1) gene on the proliferation and apoptosis of acute myeloid leukemia (AML) U937 cells, and the regulation effect on Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway. METHODS: Bone marrow mononuclear cells from newly diagnosed adult AML patients and patients with iron deficiency anemia were collected and PIM1 mRNA expression was detected by RT-qPCR. AML cell line U937 cells were divided into U937 group (U937 cells were cultured normally), Si-PIM1 group (U937 cells were transfected with low expression adenovirus vector containing PIM1 mRNA), Si-NC group (U937 cells were transfected with low expression adenovirus vector without PIM1 mRNA), coumermycin A1 (CoA1) group (JAK2 activator CoA1 was added to U937 cells at a concentration of 20 µmol/L), and Si-PIM1+CoA1 group (U937 cells were transfected with adenoviral vector containing low expression of PIM1 mRNA and added with CoA1 at a concentration of 20 µmol/L). After culture for 24 h, the expressions of PIM1 mRNA and protein, JAK2/STAT3 pathway, cell cycle and apoptosis-related proteins in U937 cells were detected by RT-qPCR and Western blot, the cell proliferation activity was detected by MTT assay, and flow cytometry was used to detect cell cycle changes and apoptosis rate. RESULTS: The PIM1 mRNA expression level in bone marrow mononuclear cells in AML patients was higher than that in patients with iron deficiency anemia (P < 0.05). Compared with U937 group, PIM1 mRNA and protein, phosphorylated JAK2 (p-JAK2)/JAK2, phosphorylated STAT3 (p-STAT3)/STAT3, Cyclin D1, cyclin-dependent kinase 2 (CDK2) protein, cell proliferation activity, S phase and G 2/M phase proportions were decreased in Si-PIM1 group (all P < 0.05), while p27, Caspase-3 protein, G0/G1 phase proportion and apoptosis rate were increased (all P < 0.05). However, the changes of above indicators in CoA1 group were just opposite to those in Si-PIM1 group, indicating that CoA1 could reverse the effect of Si-PIM1 on U937 cells. There were no significant differences in above indexes of U937 cells between U937 group, Si-PIM1+CoA1 group and Si-NC group (P >0.05). CONCLUSION: Knockdown of PIM1 gene expression can inhibit U937 cell proliferation and promote apoptosis, in order to alleviate ALM process, which may be related to the inhibition of JAK2/STAT3 pathway activation.

[Influence of TLR2- and TLR4-activated Mesenchymal Stem Cells on Migration of Cord Blood CD34+ Cells].

OBJECTIVE: This study was aimed to investigate the possible effect of Toll-like receptors 2 (TLR2) and Toll-like receptors 4 (TLR4) on the migration function of umbilical cord blood (UCB) CD34+ hematopoietic stem/progenitor cells induced by bone marrow-derived mesenchymal stem cells (MSCs) and to explore the underlying mechanism. METHODS: The expression of TLR2 and TLR4 on MSC was detected with flow cytometry. After the MSC were pretreated with TLR2 agonist (PAM3CSK4) and/or TLR4 agonist (LPS), the supernatants were collected. The effect of the supernatants on the migration of CD34+ cells was evaluated with chemotaxis assays. Alterations of chemokine (SDF-1) secreted by MSC in the supernatants were assayed by ELISA. RESULTS: The expression levels of TLR2 and TLR4 were (31.5±4.6)% and (85.6±6.7)% respectively. Compared with the blank group, the migration ability of CD34+ cells increased significantly in control, LPS and/or PAM3CSK4 groups (P<0.01). Further study found that LPS and/or PAM3CSK4 enhanced the chemotactic ability of CD34+ cells (P<0.05), but the concentration of SDF-1 was not changed significantly in all of LPS and/or PAM3CSK4 groups (P>0.05) in comparison with the control group. CONCLUSION: TLR2 and TLR4 signalings may indirectly increase the migration of CD34+ hematopoietic stem/progenitor cells by modulating BM-MSC functions, which may not significantly correlate with the production of chemokine SDF-1 by MSCs.