Gambogic Acid is a natural small molecule that induces apoptosis by potently inhibiting anti-apoptotic Bcl-2 family proteins (Bcl-2, Bcl-XL, Mcl-1, etc.) and activating caspases (EC50 0.78-1.64 µM). It is widely used in cancer research, demonstrating antitumor activity in both cellular and animal models.