Relationship between DNMT1 and Methylation of SHP-1 Promoter 2 in K562 Cells / 中国实验血液学杂志

<p><b>OBJECTIVE</b>To investigate the relationship of DNA methyltransferase 1 ( DNMT1 ) with hematopoietic cell phosphatase (SHP-1) gene expression and promoter 2 methylation status in cell line K562.</p><p><b>METHODS</b>The promoter sequence of SHP-1 gene promoter 2 in NCBI database was analyzed, the K562 cells were transfected with the lentiviral plasmids-the specified retroviral vector psiHIV-mU6-shDNMT1 and psiHIV-mU6-mcherryFP-control. The methylation status of SHP-1 gene promoter 2 in K562 cells was detected by methylation-specific polymerase chain reaction (MSP) and bisulfite-modified sequencing (BSP). Western blot was used to detect the protein expression level of SHP-1 and DNMT1, the SYBR Green fluorescence quantitative PCR was used to detect the expression of SHP-1 mRNA.</p><p><b>RESULTS</b>It was found that the promoter 2 of SHP-1 gene located between -577 bp to +300 bp, and 22 CpG sites contained between -353 bp-+182 bp were aberrantly hypermethylated and the SHP-1 could not be detected in K562 cells. In vitro, the detection demonstrated that the expression level of DNMT1 in K562 cells transfected with psiHIV-mU6-shDNMT1 was 0.48±0.06 significantly lower than that of psiHIV-mU6-control group (1.33±0.19)(t= 4.18, P<0.05). The expression of SHP-1 mRNA in K562 cells transfected with psiHIV-mU6-shDNMT1 was significantly higher than that in K562 cells transfected with psiHIV-mU6-shDNMT1 (14.23±3.83 vs 1.031±0.156)(P<0.01). DNMT1 silencing induced demethylation of the 22 CpG sites located in the SHP-1 promoter 2, and SHP-1 gene was re-expression in K562 cells.</p><p><b>CONCLUSION</b>The DNMT1 in K562 cells relates with the hypermethylation and silencing of SHP-1 promoter in K562 cells.</p>

Overexpression of SHP-1 Enhances the Sensitivity of K562 Cells to Imatinib / 中国实验血液学杂志

<p><b>OBJECTIVE</b>To explore the effect of overexpression of SH2-containing tyrosine phosphatase 1 (SHP-1) on sensitivity of chronic myelogenous 1eukemia (CML) K562 cell line to imatinib and its related mechamism.</p><p><b>METHODS</b>K562 cells were infected with the lentiviral plasmids containing the specified retroviral vector (pEX-SHP-1-puro-Lv105) or the mock vector (pEX-EGFP-puro-Lv105). The expression of SHP-1 in K562 cells treated with 0.2 µmol/L imatinib (IM) for 72 h was determined by Western blot. After transfection the CCK-8 assay was used to determine the proliferation of the tramfected K562 cells (K562(SHP-1) and K562(EGFP) cells) at 72 h after exposure to different doses of IM, the half inhibitary concentration (IC50) was calculated. The mechanisms of the overexpression effects of SHP-1 and IM on the proliferation in K562 cells was investigated, the BCR-ABL1 activity and the level of tyrosine phosphorylation of CrkL (pCrkL) was measured by flow cytometry; the Western blot was used to detect the expression and activity of these molecules controlling cell growth, including MAPK, AKT, STAT5 and JAK2.</p><p><b>RESULTS</b>After exposure of K562 cells to 0.08 µmol/L IM for 72 h, there was no significant change of SHP-1 expression in K562 cells. After exposure to 0.2 µmol/L of IM for 72 h, the inhibitory rate of K562(SHP-1) group was higher than that of K562(EGFP) group (P < 0.05), indicating that overexpression of SHP-1 in K562 cells could enhance the proliferation inhtibition effect of IM on K562 cells. The IC50 of IM in K562(SHP-1) cells was the lower as compared with that of K562(EGFP) cells (P < 0.05) after exposure to different concentrations of IM for 72 h. The slope of K562(SHP-1) cells was the largest ranging 0.02 - 0.16 µmol/L of IM. Overexpression of SHP-1 and IM could inhibit the activity BCR-ABL1, MAPK, AKT, STAT5 and JAK2 signaling pathways in the K562 cell line and displayed a synergistic effect.</p><p><b>CONCLUSION</b>SHP-1 inhibits BCR-ABL1, MAPK, AKT, STAT5 and JAK2 signaling pathways in K562 cells, the overexpression of SHP-1 can enhance the sensitivity of K562 cells to IM.</p>

Expression and Clinical Significance of DNMT in Patients with Chronic Myeloid Leukemia / 中国实验血液学杂志

<p><b>OBJECTIVE</b>To investigate the expression and clinical significance of DNA methyltransferases (DNMT) mRNA in patients with chronic myeloid leukemia (CML).</p><p><b>METHODS</b>The expression levels of DNMT mRNA in mononucllear cells (MNC) of bone marrow or in peripheral blood of 93 CML patients in 3 different phases and 10 normal controls (NC) were detected by SYBR Green flurescent quatitative PCR.</p><p><b>RESULTS</b>The relative expression levels of DNMT1 mRNA in NC, chronic phase CML (CML-CP), accelerated phase (CML-AP) and blastic phase (CML-BP) were 1.45 ± 0.22, 1.83 ± 0.63, 2.95 ± 0.87 and 3.24 ± 1.39 resectively. The expression of DNMT1 mRNA showed no statistically significant difference between CML-CP and NC (P = 0.28). The expression of DNMT1 mRNA in advanced stages (including CML-AP and CML-BP) of CML obviously increased in comparison with CML-CP and NC (P < 0.05). The expression of DNMT1 mRNA in CML-AP was not significantly different from that in CML-BP (P = 0.336). The relative expression levels of DNMT3a mRNA in NC, CML-CP, CML-AP and CML-BP groups were 1.29 ± 0.34, 1.34 ± 0.46, 2.33 ± 1.05 and 3.18 ± 1.23 resectively. And the expression levels of DNMT3a mRNA were not statistically significantly different between CML-CP and NC (P = 0.844). The results showed that the expression of DNMT3a mRNA in the advanced phase of CML significantly increased in comparison with that in CML-CP and NC (P < 0.05). Meanwhile, the expression of DNMT3a mRNA in CML-AP was not different from that in CML-BP (P = 0.304). The relative expression levels of DNMT3b mRNA in NC, CML-CP, CML-AP and CML-BP groups were 1.37 ± 0.31, 16.41 ± 22.50, 9.36 ± 5.50 and 12.17 ± 13.44 resectively. It was also found that the level of DNMT3b mRNA in CML significantly increased in comparison with NC (P < 0.05), and that the between the 3 different phase of CML was not statistically significantly different (P >0.05).</p><p><b>CONCLUSION</b>The expression of DNMT mRNA increases in advanced CML as compared with normal controls and CML-CP, and the increased levels of DNMT mRNA probably correlate with disease progression in CML.</p>