A new anticancer toxin based on HER2/neu-specific DARPin and photoactive flavoprotein miniSOG

Area of Science:

• Biochemistry
• Cell Biology
• Oncology

Background:

• Targeted photodynamic therapy offers a promising approach for cancer treatment.
• Developing novel photosensitizers with specific targeting capabilities is crucial for improving therapeutic efficacy and reducing side effects.

Purpose of the Study:

• To investigate the cytotoxic effects of the novel targeted phototoxin DARPin-miniSOG on cancer cells in vitro.
• To elucidate the mechanism of action underlying DARPin-miniSOG-induced cell death.

Main Methods:

• In vitro experiments were conducted using HER2/neu-positive cancer cells.
• Cytotoxicity was assessed by measuring cell viability (IC50).
• Mechanisms of cell death were analyzed through DNA fragmentation assays, caspase-3 activity assays, and propidium iodide (PI) staining. Oxidative stress involvement was probed using ascorbic acid treatment. Subcellular localization was determined via co-localization studies.

Main Results:

• DARPin-miniSOG demonstrated significant light-induced cytotoxicity against HER2/neu-positive cancer cells with an IC50 of 0.8 μM.
• The cytotoxic effect was abrogated by ascorbic acid, indicating the involvement of oxidative stress.
• Phototoxin treatment under blue light illumination induced necrotic cell death, confirmed by DNA fragmentation, caspase-3 activity, and PI staining.
• Co-localization analysis revealed that DARPin-miniSOG primarily accumulates in endosomes and lysosomes.

Conclusions:

• DARPin-miniSOG is an effective targeted phototoxin inducing light-activated necrotic cell death in HER2/neu-positive cancer cells.
• The mechanism of action involves oxidative stress and results in the accumulation of the phototoxin within cellular endosomes and lysosomes.
• These findings support the potential of DARPin-miniSOG as a therapeutic agent in targeted photodynamic cancer therapy.