OBJECTIVETo investigate the relationship between the expression of murine double minute 2 (MDM2) oncogene and non-Hodgkin lymphoma (NHL) in childhood.

METHODSThirty-one cases of NHL were enrolled in this study as patient group and 8 cases of lymphadenitis as control group. (1) Immunohistochemistry ultrasensitive S-P assay was used to detect the expression of MDM2 protein in pathological tissues in all cases. Positive cells were dyed yellow or brown in nuclei. MDM2 positive cell was defined as >/= 10% of the tumor cells were positive, which was overexpression of MDM2 protein. (2) RT-PCR (reverse transcription-polymerase chain reaction) was performed to value the overexpression of MDM2 mRNA in the pathological tissues and mononuclear cells in peripheral blood. While the ratio of MDM2/beta-actin was >16% was defined as overexpression of MDM2 mRNA.

RESULTS(1) Rates of overexpression of MDM2 protein and MDM2 mRNA were 64.5% and 61.3%, respectively, which were significantly different as compared to that of control group (P < 0.05 and P < 0.01, respectively). (2) The relationship analysis among subgroups in the experiment group showed that the overexpression of MDM2 protein did not correlate with classifications of working formulation, cellular origin, sex, clinical stage and involved extranodal sites (P > 0.05), but significantly correlated with classifications of B status and the increased serum LDH level (P < 0.05). It was shown that the overexpression of MDM2 mRNA did not correlate with classifications of working formulation, cellular origin, sex and clinical stage (P > 0.05), significantly correlated with B status (P < 0.05), and was remarkably significantly correlated with the involved extranodal sites and the increased serum LDH level (P < 0.01). (3) It was demonstrated that the overexpression of MDM2 mRNA in the pathological tissues was similar to the overexpression of MDM2 protein in the pathological tissues and MDM2 mRNA in peripheral blood (P > 0.05, kappa = 0.655 and 0.571), and the overexpression of MDM2 protein in the pathological tissues was similar to that of MDM2 mRNA in peripheral blood (P > 0.05, kappa = 0.609).

CONCLUSIONS(1) The rate of MDM2 oncogene overexpression was quite high. (2) The overexpression of MDM2 protein in pathological tissues determined by using immunohistochemistry ultrasensitive S-P assay was similar to that of MDM2 mRNA in pathological tissues detected by using RT-PCR method. Both methods might be used to detect the overexpression of MDM2 oncogene in the cases of childhood NHL. (3) The overexpression of MDM2 oncogene related to the poor status and poor prognosis of patients with childhood NHL.