GDF15 and meningioma: In meningioma patients, DJ-1, GDF15, and MFGE8 gene expression levels were significantly elevated in tumours with Ki-67 Pi > 5% compared to those with Ki-67 Pi ≤ 5% (DJ-1, GDF15, and MFGE8; p = 0.015, p = 0.003, and p = 0.012, respectively).