Preferentially Expressed Antigen of Melanoma (PRAME) and Wilms’ Tumor 1 (WT 1) Genes Expression in Childhood Acute Lymphoblastic Leukemia, Prognostic Role and Correlation with Survival

BACKGROUND: Acute lymphocytic leukemia (ALL) is the most common hematologic malignancy in children. In young children it is also largely curable, with more than 90% of afflicted children achieving long-term remission. PRAME (Preferentially expressed antigen of melanoma) gene belongs to Group 3 class I HLA-restricted widely expressed antigens in which genes encoding widely expressed tumor antigens have been detected in many normal tissues as well as in histologically different types of tumors with no preferential expression on a certain type of cancer. It has been found to be expressed in a variety of cancer cells as leukemia & lymphoma. PRAME monitoring can be useful for detection of minimal residual disease and subsequent relapses particularly those leukemias in which specific tumor markers are unavailable. Wilms’ tumor1 (WT1) gene was identified as a gene that plays an important role in normal kidney development and inactivation of its function was shown to result in the development of Wilms’ tumors in paediatric patients. Disruption of WT1 function has been implicated in the formation of many different tumor types. AIM: to study how PRAME & WT 1 genes expression patterns influence cancer susceptibility & prognosis. PATIENTS & METHODS: 50 patients with denovo childhood acute lymphoblastic leukemia, as well as 50 age and sex matched apparently healthy volunteers were genotyped for PRAME and WT1 genes expression by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: PRAME gene was expressed in 34 of the patients (68%) and WT1 gene was expressed in 26 of the patients (52%). Expression of both genes was significantly higher compared to controls (P < 0.0001). Analysis of relapse free survival among our patients revealed that patients expressing PRAME gene or WT1 gene had better relapse free survival (p value=0.02 and 0.01 respectively). Relapse free survival increased significantly among patients coexpressing PRAME and WT 1(p value =0.001). CONCLUSION: It is concluded that the expression of PRAME and WT1 genes are indicators of favorable prognosis and can be useful tools for monitoring minimal residual disease (MRD) in acute leukemia especially in patients without known genetic markers. Differential expression between acute leukemia patients and healthy volunteers suggests that the immunogenic antigens (PRAME and WT1) are potential candidates for immunotherapy in childhood acute leukemia.