Tumor associated antigen PRAME is a marker of favorable prognosis in childhood acute myeloid leukemia patients and modifies the expression of S100A4, Hsp 27, p21, IL-8 and IGFBP-2 in vitro and in vivo

Abstract

Preferentially expressed antigen of melanoma (PRAME) is expressed in a wide variety of tumors, but in contrast with most other tumor associated antigens, it is also expressed in leukemias. In a previous study, we showed that overexpression of PRAME induced apoptosis, inhibited cell proliferation and reduced tumorigenicity of leukemic cells in vivo. We also demonstrated that PRAME overexpression induced the repression of three genes (Hsp27, S100A4 and p21) associated with an unfavorable prognosis in leukemia. Here, we further investigated the mechanisms of PRAME-induced tumor suppression in vitro and in vivo. We performed a gene profiling study by analysing PRAME shRNA-silenced leukemic cells on high-density micro-arrays (Affymetrix) and found that PRAME altered the expression of two additional genes potentially involved in cancerogenesis and cancer progression: IL-8 and IGFBP-2. In a series of 28 acute myeloid leukemia pediatric patients, we observed that PRAME expression was associated with an increased leukemia-free survival. Importantly, the correlation between PRAME expression in leukemic cell lines and the decreased expression of Hsp27, S100A4, p21, IL-8 and the increased expression of IGFBP-2 was also observed in vivo, in leukemic patients. Our results suggest that the favorable prognosis of PRAME could be mediated, at least in part, by the modified expression of those genes.