The Early Diagnostic Significance Of Detecting Plasma Free DNA Of Malignant Lymphoma Patients

Objective:To evaluate the early diagnostic significance of detecting plasma free DNA of diffuse large B-cell lymphoma (DLBCL) patients.Methods:1. Plasma free DNA were extracted in 20 primary or relapse cases of DLBCL,10 cases of T-NHL,10 cases of lymphonodes inflammatory and 20 healthy controls. The Bcl-2/IgH and IgH gene rearrangments in plasma were assayed by polymerase chain reaction (PCR) and compared with that in peripheral blood mononuclear cells (PBMNC) or bone marrow mononuclear cells (BMMNC).2. Plasma free DNA were extracted in 22 primary or relapse cases of DLBCL,10 of lymphonodes inflammatory and 10 healthy controls. Methylation state of CpG island in SHP-1 and P16 genes were detected by methylation specific polymerase chain reaction (MSP) and unmethylation-specific polymerase chain reaction (Un-MSP). The expression level of SHP-1 and P16 genes were detected by reverse transcriptase polymerase chain reaction (RT-PCR).Results:1. The positive rate of plasma free IgH and Bcl-2/IgH gene rearrangements in DLBCL were 60%(12/20) and 50%(10/20), respectively. However, we did not find free DNA in plasma of 10 cases of inflammatory lymph and 20 healthy controls. IgH gene rearrangement was not found in 5 cases of DLBCL in remission while Bcl-2/IgH gene rearrangement was not found in 4 cases of DLBCL in remission. The positive rate of IgH and Bcl-2/IgH gene rearrangements in DLBCL were higher in plasma than in PBMNC or BMMNC,but they were not a remarkable difference (P> 0.05)2. The frequency of methylation in plasma free SHP-1 and PI 6 gene promoter in DLBCL were 91%(21/22) and 71%(16/22) respectively. The expression of SHP-1 and PI 6 gene in DLBCL were disappeared and less in DLBCL because of gene silence than in lymphonodes inflammatory cases and healthy controls. Methylation state of plasma free SHP-1 and P16 gene promoter can be detected consistly in the cases of DLBCL in remission.Conclusions:1. Plasma free IgH or Bcl-2/IgH rearrangement in DLBCL may be a novel parameter for clinical early diagnosis without the restriction of the position of enlarged lymph node. Also, it can be served as a source for biomarkers of a potential prognostic marker in DLBCL.2. SHP-1 or P16 gene silence with CpG methylation may be one of the critical events to the onset of DLBCL, which is important implications for the diagnosis and target of the gene therapy.