Clinical Study Of Abnormal Methylation Of P15 And SOCS-1 Genes In Patients With Myelodysplastic Syndrome

Objective: To investigate the occurrence and clinical significance of abnormal methylation of p15 and SOCS-1 gene promoter in MDS patients.Methods: The methylation specific polymerase chain reaction (MSP) and fluorescence quantitative PCR (qRT-PCR) method was used to detect the 70 cases of MDS patients and 40 cases of normal human bone marrow p15 and SOCS-1 gene promoter methylation status , moreover their mRNA expression level, at the same time we analyze the relationship with MDS patients with the clinical data.Result: ( I ) Expression and clinical significance of P15 in MDS.1. The incidence of abnormal methylation of p15 gene promoter region in 70 patients with MDS was significantly higher than that in control group (57.14%vs 0%), and there was significant difference between the two groups (P<0.001).2. The incidence of abnormal methylation in p15 promoter region was significantly higher in RAEB-1 and RAEB-2 patients in WHO than in patients with other subtypes of MDS.3. In 60 patients who grouped according to IPSS ,the p15 gene promoter region methylation rate in low risk group was 0% (0/3), in intermediate-1 group was 47.22% (17/36) , in intermediate-2 group was 76.47% (13/17) and in high-risk group was 100% (4/4), each packet methylation occurs is statistically significant differences (P=0.008).4. Among 55 MDS patients who had been detected by FISH, there were 19 cases (28.72%) with abnormal or only -Y, -5/5q- and 20q-, in 39 cases who had abnormal methylation of P15 gene. P15 gene abnormal methylation occurred in5 (62.5%) of 8 patients with only +8 chromosome abnormality. There were 7 cases (87.5%) of 8 patients who had -7/7q- or more than one chromosomal abnormality .The difference was not statistically significant (P=0.159). In 46 MDS patients with chromosome culture, the incidence of abnormal methylation of p15 in MDS patients with abnormal karyotype was significantly. higher than that in patients with normal karyotype ( 80.95% vs 48%, P=0.032 ).5. The relative expression of p15 mRNA in bone marrow cells of 70 patients with MDS was significantly lower than that in normal people (1.41±1.03 vs 2.63 ±1.67,P<0.001) . The relative expression of mRNA in bone marrow cells of MDS patients with abnormal methylation of p15 promoter was significantly lower than that of MDS patients without abnormal methylation(1.19±1.02 vs 1.72±0.99, P=0.037).(II) Expression and clinical significance of SOCS-1 in MDS.1. The incidence of abnormal methylation of SOCS-1 gene promoter region in 70 patients with MDS was significantly higher than that in control group(25.71% vs 0%) , and there was significant difference between the two groups(P<0.001).2. There was a significant difference in the incidence of abnormal methylation of SOCS-1 promoter region in MDS patiens who grouped by WHO(P=0.003 ) , and positively correlated with the proportion of the bone marrow cells (r=0.528, P<0.001).3. In 60 patients who grouped according to IPSS ,the SOCS-1 gene promoter region methylation rate in low risk group was 0% (0/3), in intermediate-1 group was 11.11% (4/36) , in intermediate-2 group was 47.06%(8/17) and in high-risk group was 75% (3/4), each packet methylation occurs is statistically significant differences(P=0.002).4. Among 55 MDS patients who had been detected by FISH , there were 8 cases (20.51%) with abnormal or only -Y, -5/5q- and 20q-, in 39 cases who had abnormal methylation of SOCS-1 gene. The SOCS-1 gene abnormal methylation occurred in 1 (12.5%) of 8 patients with only +8 chromosome abnormality. There were 4 cases (50%) of 8 patients who had -7/7q- or more than one chromosomal abnormality .The difference was not statistically significant (P=0.205) . In 46 MDS patients with chromosome culture, the incidence of abnormal methylation of SOCS-1 in MDS patients with abnormal karyotype was significantly higher than that in patients with normal karyotype(47.62% vs 16%, P=0.027).5. The relative expression of SOCS-1 mRNA in bone marrow cells of 70 patients with MDS was significantly lower than that in normal people (1.00±0.72 vs 2.55±2.47,P<0.001) . The relative expression of mRNA in bone marrow cells of MDS patients with abnormal methylation of SOCS-1 promoter was significantly lower than that of MDS patients without abnormal methylation(0.76 ±0.72 vs 1.16 ± 0.68,P=0.042).(ⅢI) Through Spearman correlation analysis, the results showed that the expression level of mRNA of gene SOCS-1 and the expression level of mRNA gene p15 were positively correlated (r=0.467,P<0.001) . 13 patients with p15 and SOCS-1 were simultaneously present in tow genes, the incidence rate in IPSS group was high-risk group> intermediate-2 group>intermediate-1 group,the difference was statistically significant(P<0.001).(IV) 6 .patients with MDS who had been chemotherapy with Decitabine,the relative expression levels of p15 and SOCS-1 mRNA gene were increased compared with those before treatment.Conclusion: 1. The abnormal high methylation rate of p15 and SOCS-1 gene promoter in bone marrow cells of MDS patients was higher than that of normal persons.2. The frequency of methylation of p15 and SOCS-1 gene promoter was higher in high risk MDS patients which suggests that the prognosis of MDS may be closely related to the methylation of these two genes.The MDS ,patients with abnormal chromosome karyotype, the incidence of abnormal methylation of p15 and SOCS-1 genes was higher,which suggests that correlation between methylation of p15 and SOCS-1 gene and chromosomal abnormality.3. Aberrant methylation of p15 and SOCS-1 gene in bone marrow cells of MDS patients resulted in the decrease of these two genes’s mRNA expression level. Further more, the relative expression level of these, two gene’s mRNA in bone marrow cells of MDS patients may have correlated relationship,which suggests that there may be a synergistic effect of the two tumor suppressor genes.