PIP5K1A and posterior cortical atrophy: To further examine the subcellular localization of PIP5K1α and monitor the dynamics of cell–cell interaction between PCa cells and U-937 cells during the co-culture, we used 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindodicarbocyanine perchlorate (DiD) in red, a membrane tracer to label U-937 cells before subjecting them to mono-culture or co-culture with unstained PC-3 cells for 24 h.