[Clinical significance of mdm2 and p53 expression in orbital rhabdomyosarcoma].

Objective: To evaluate the role of oncogene mdm2 and p53 in the development of orbital rhabdomyosarcoma (ORMS) and demonstrate the feasibility of mdm2 and p53 as biological characteristic markers and prognostic indicators.

Methods: Immunostainings of mdm2, p53 and Ki-67 antigen were performed on archival paraffin-embedded tissues taken from 31 ORMS patients. In situ hybridization was used to demonstrate the expression of mdm2 and p53 on the mRNA level. The correlations between the two genes and the clinical histopathologic parameters including age, gender, cells subtype, differentiation grade and proliferation index were analyzed.

Results: The positive expressions of mdm2 and p53 were 77.4% (24/31) and 71.0% (22/31) respectively; and the co-expression of mdm2 and p53 was 61.3%. The expressions of mdm2 and p53 on the protein level were in coincidence with that on the mRNA level. (1)The poorly and moderately differentiated group showed significantly higher expression of mdm2 and co-expression of mdm2-p53 than the well-differentiated group (P = 0.007; P = 0.009, respectively). (2) The samples were divided into actively-proliferating group and inactively-proliferating group in accordance with the expression of Ki-67 protein. The positive expression of p53 was significantly higher in actively-proliferating group than inactively-proliferating group. No statistic correlation of the positive expression of mdm2 and p53 with the other histopathologic parameters was observed.

Conclusions: mdm2 and p53 were significantly correlated with the differentiation and proliferation of ORMS. The co-expression of mdm2 and p53 expression suggested that mdm2 might play a role in deactivation of p53. The overexpression of mdm2 and p53 leaded to the loss of cell cycle control and may contribute to the tumorigenesis and tumor progression of ORMS. Mdm2 and p53 may be prognostic indicators of the tumor.