SPP1 and posterior cortical atrophy: However, in PCa tissues, CSF factor and IL34 secreted by FAP+ fibroblasts together act on the CSF1R of SPP1+ and C1QC+ macrophages (Figure 5D), suggesting that in PCa, the interaction between FAP+ fibroblasts and SPP1+ macrophages through the CSF pathway are significantly enhanced and altered.