[Hsa-let-7b-5p Inhibits Proliferation of Human Leukemia THP-1 Cells via FTO/m6A/MYC Signaling Pathway].

OBJECTIVE: To investigate the down-regulation effect of let-7b-5p on the expression of FTO in acute myeloid leukemia cell line THP-1 and inhibitory effect on THP-1 proliferation via m6A/MYC signaling pathway. METHODS: The acute myeloid leukemia cell line THP-1 and the normal human peripheral blood mononuclear cells (PBMNC) were selected as subjects. The expression of let-7b-5p and FTO mRNA in those cells was detected by qPCR, further the expression of FTO protein in those cells was detected by Western blot. And, the luciferase reporter gene assay was used to verify the targeting effect of let-7b-5p on FTO. Finally, THP-1 cells were transfected respectively with let-7b-5p mimic, and PBMNC with let-7b-5p inhibitor, there after the C-MYC mRNA m6A enrichment level in transfected cells was analyzed by dot blot, the expression levels of let-7b-5p, FTO and c-MYC were assayed by RT-PCR, the expressions of FTO and c-MYC protein were verified by Western blot, and the proliferation level of cells after transfection was detected by MTT assay. RESULTS: Compared with PBMNC, the expression of let-7b-5p in THP-1 significantly decreased, while the expression of FTO was significantly increased (P<0.05). After transfection with let-7b-5p mimic combined with FTO 3'-UTR, the luciferase activity of transfected THP-1 cells significantly decreased, but the luciferase activity significantly increased after transfection with mutant 3'-UTR, which was significantly different from the negative control group(blank vector) (P<0.05). Let-7b-5p inhibitor down-regulated c-MYC mRNA m6A enrichment, and then up-regulated the expression of FTO in transfected PBMNC cells, the effects of which were significant (P<0.05). However, let-7b-5p mimic up-regulated c-MYC mRNA m6A enrichment level and down-regulated the expression of FTO in the transfected THP-1 cells, and the cell proliferation rate was significantly lower than that in the negative control group (blank vector) (P<0.05). CONCLUSION: Human acute myeloid leukemia cell line THP-1 low expresses the let-7b-5p, which regulates c-MYC expression through let-7b-5p-/FTO-/m6A axis and promotes the proliferation of leukemia cell line THP-1.

[A case-control study on the risk factors for lower respiratory tract infection by Stenotrophomonas maltophilia in a medical intensive care unit].

OBJECTIVE: To explore the risk factors for lower respiratory tract infection by Stenotrophomonas maltophilia in the medical intensive care unit (MICU) in Fujian Provincial Hospital. METHODS: A 1:4 matched case-control study was carried out in the MICU in Fujian Provincial Hospital. Thirty-five patients with hospital-acquired lower respiratory tract infection by Stenotrophomonas maltophilia from 2007 to 2010 were included as cases, and 140 patients without lower respiratory tract infection served as controls. The case group included 22 cases with respiratory diseases, 4 with cerebrovascular diseases, 4 with cardiovascular diseases, 1 with hemorrhage of the digestive tract, 1 with acute pancreatitis, 1 with chronic kidney disease, 1 with cervical cancer and 1 with Alzheimer's disease. While the control group included 30 cases with respiratory diseases, 44 with cerebrovascular diseases, 14 with cardiovascular diseases, 2 with malignant tumors and 50 with others. Patients' information, general situation before being admitted to MICU, drug therapy, invasive procedures and hospital-acquired infection were analyzed. Conditional logistic regression was performed to identify independent risk factors. RESULTS: Univariate analysis showed that factors such as more than 4 underlying diseases (OR = 4.63), APACHE-II score ≥ 20(OR = 10.29), stay in the general ward more than 1 week before being admitted to MICU, treatment with more than 3 kinds of antibiotics (OR = 8.03), endotracheal intubation (OR = 4.10) or tracheotomy (OR = 50.29) and mechanical ventilation (OR = 7.95) were risk factors for hospital-acquired lower respiratory tract infection by Stenotrophomonas maltophilia. Multivariate logistic regression showed that variables such as APACHE-II score (OR = 8.39), kinds of antibiotics used (OR = 5.96) and tracheotomy (OR = 28.92) were independent risk factors (P < 0.01). CONCLUSIONS: Underlying diseases, the severity of diseases, tracheotomy, mechanical ventilation, and the use of wide-spectrum antibiotics are important risk factors for lower respiratory tract infection by Stenotrophomonas maltophilia in MICU. To identify these factors and take preventive measures earlier may be useful for decreasing Stenotrophomonas maltophilia infection-related mortality.