ABSTRACT
<p><b>OBJECTIVE</b>To investigate the methylation status of zonula occludens-1 (ZO-1) gene promoter and its clinical significance in children with stage IV non-Hodgkin lymphoma (NHL) and to provide a basis for further etiological study and early diagnosis of this disease.</p><p><b>METHODS</b>Fifty-five children with a confirmed diagnosis of stage IV NHL (40 cases of T-NHL and 15 cases of B-NHL) were selected as the case group, and 20 children with diseases other than hematologic malignancies were selected as the control group. Bone marrow samples were collected from these subjects. Methylation-specific PCR (MS-PCR) was applied to evaluate the methylation status of ZO-1 gene promoter, and the integrated optical density (IOD) was determined. RT-PCR was used to measure the mRNA expression of ZO-1.</p><p><b>RESULTS</b>MS-PCR showed that the methylated bands of ZO-1 gene promoter were found in 39 (70.9%) of 55 patients in the case group before treatment, while no ZO-1 gene promoter methylation was detected in the control group. With close tracking of 47 cases in the study group, consisting of 32 cases of T-NHL and 15 cases of B-NHL, the rates of ZO-1 gene promoter methylation prior to treatment were 72% and 67%, respectively, (P>0.572). The cases of T-NHL and B-NHL showed no significant changes in methylation rate in the early and middle phases of chemotherapy (P>0.05), but they showed significant changes in methylation rate in the late phase of chemotherapy (P<0.05). RT-PCR showed that the NHL cases carrying methylated ZO-1 gene had no mRNA expression of ZO-1, while all children in the control group had mRNA expression of ZO-1. There was no linear relationship between the total number of peripheral blood leukocytes and ZO-1 gene IOD (r=0.093, P=0.575); a positive correlation was found between the number of malignant cells in bone marrow and ZO-1 gene IOD (r=0.669, P<0.001).</p><p><b>CONCLUSIONS</b>ZO-1 gene shows a hypermethylation status in children with NHL, and the methylation level is positively correlated with the number of malignant cells in bone marrow. ZO-1 may be used as a novel molecular marker in early diagnosis, outcome assessment, prognostic evaluation, and detection of minimal residual disease.</p>