IGFBP4 and glioblastoma: Interestingly, we found that, in GBM, the IGFBP4 expression level had a significant positive correlation with the level of infiltrating dendritic cells (r = 0.423, P=1.29e − 19) and a significant negative correlation with the level of tumor purity (r = –0.166, P=6.35e − 04), B cells (r = –0.108, P=2.66e − 02), and CD8+ T cells (r = –0.16, P=1.05e − 03).