Apoptosis
Programmed cell death — an orderly, genetically controlled process by which damaged or unnecessary cells self-destruct without triggering inflammation. Dysregulated apoptosis contributes to both cancer (too little) and tissue degeneration (too much).
Apoptosis (from Greek: “falling off”) is the process by which cells undergo controlled self-destruction. Unlike necrosis — uncontrolled cell death from injury that spills cellular contents and triggers inflammation — apoptosis is orderly. The cell shrinks, fragments its DNA, packages its contents into membrane-bound vesicles (apoptotic bodies), and signals neighboring immune cells to engulf the debris quietly.
Why Apoptosis Matters
Every day, billions of cells in a dog’s body undergo apoptosis as part of normal tissue maintenance. This controlled turnover serves critical functions:
- Removing damaged cells before they accumulate mutations that could lead to cancer
- Eliminating cells infected by viruses to contain the infection
- Sculpting tissues during development (the webbing between embryonic digits is removed by apoptosis)
- Maintaining immune tolerance by deleting self-reactive immune cells
Apoptosis and Cancer
Cancer cells characteristically evade apoptosis. Mutations in tumor suppressor genes (p53) or overexpression of anti-apoptotic proteins (BCL-2 family) allow damaged cells to continue dividing. This evasion of programmed cell death is one of the defining hallmarks of cancer.
In dogs, cancers such as lymphoma and hemangiosarcoma frequently involve dysregulated apoptotic pathways. Many chemotherapy drugs work by triggering apoptosis in cancer cells — their selectivity depends on cancer cells being more susceptible to apoptotic signals than healthy cells.
Apoptosis and Aging
With age, the balance between apoptosis and cellular senescence shifts. Cells that should undergo apoptosis may instead enter senescence — remaining alive but dysfunctional and secreting inflammatory signals. Conversely, excessive apoptosis in tissues with limited regenerative capacity (neurons, cardiomyocytes) contributes to age-related functional decline.
Senolytics and Apoptotic Pathways
Senolytic drugs work by reactivating apoptosis in senescent cells. Dasatinib + quercetin and fisetin target the anti-apoptotic survival mechanisms that keep senescent cells alive, tipping them toward programmed cell death and clearance. This targeted reactivation of apoptosis is a key strategy in longevity pharmacology.