PROM1 and glioblastoma: We observed that the mean expression of the suppressor protein PROM1 (CD133) in the mesenchymal GBM subtype was lower than its mean expression level in the other three subtypes (mean expression levels in mesenchymal, classical, neural and proneural subtypes are 6.46, 7.13, 7.37 and 8.09, respectively).