PCSK9 and cancer: PCSK9 deficiency seems to inhibit cancer cell proliferation and promote apoptosis through various pathways, including activating caspase-3 and caspase-9, altering the Bcl-2-associated X protein (BAX) / B-cell lymphoma 2 (Bcl-2) ratio to engage mitochondrial apoptotic signaling, and deactivating anti-apoptotic proteins like survivin, X-linked inhibitor of apoptosis protein (XIAP), and phospho-protein kinase B (p-Akt).