Procathepsin D and cancer: From molecular biology to clinical applications

Figure 3 Proposed mechanism of procathepsin D/cathepsin D function in cancer progression. The over-expressed procathepsin D (pCD) escapes the physiological intracellular targeting pathways and is secreted by the cancer cells. Small part of secreted pCD is bound and internalized via M6PR pathway, the rest by a yet unidentified receptor. The receptor-pCD interaction activates mitogen-activated protein kinases (MAPK) pathway with subsequent changes in expression of numerous cancer-promoting genes including NFKB2 and some cytokines. Interaction of pCD with endothelial and stromal cells is also involved.