Purpose: The tumor-associated antigen PRAME, a potential candidate for immunotherapeutic targeting, is frequently expressed in a variety of cancers. However, no information about its presence in neuroblastoma is available to date. We therefore evaluated and quantified PRAME expression in a considerable number of neuroblastoma tumors and assessed its impact on the outcome of patients.
Experimental design: Qualitative analysis of PRAME expression was assessed by reverse transcription (RT)-PCR screening of 94 patients with primary neuroblastoma. The same cohort was used for semiquantitative determination of transcript levels by Northern blotting, comparing the signal intensities of patients with those of testis total RNA. For more precise quantification of PRAME expression, real-time RT-PCR was performed in 88 patients of the above cohort and 7 additional patients, thus leaving a total of 101 patients that were analyzed with either method. Furthermore, association with tumor stage, age of patients at diagnosis, and MYCN amplification was determined as well as the prognostic impact of PRAME expression.
Results: RT-PCR screening detected PRAME expression in 93% of primary neuroblastoma and 100% of patients with advanced disease. Furthermore, RT-PCR and Northern blot analysis showed a highly significant association of PRAME expression with both higher tumor stage (P < 0.01) and the age of patients at diagnosis (P < 0.01). Finally, precise quantification of PRAME expression by quantitative real-time reverse transcription-PCR displayed significant impact on the outcome of patients.
Conclusions: PRAME expression in neuroblastoma is extraordinarily common and was universally seen in patients with advanced-stage disease in our study. Furthermore, significant impact of PRAME expression on the outcome of patients was shown. Thus, PRAME may present a particularly attractive target for immunotherapeutic strategies in neuroblastoma.