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Updated: Apr 21, 2026
An In Vitro Approach to Photodynamic Therapy
Published on: August 17, 2018
Blue light activates phase 2 response proteins and slows growth of a431 epidermoid carcinoma xenografts
Alpesh D Patel1, Shaun Rotenberg2, Regina L W Messer3
1Department of Oral Biology, Georgia Regents University, Augusta, GA, U.S.A. Division of Orthodontics, The Ohio State University, Columbus, OH, U.S.A.
Background:
Recent studies suggest that light in the UVA range (320-400 nm) activates signaling pathways that are anti-inflammatory, antioxidative and play a critical role in protection against cancer. These effects have been attributed to NF-E2-related factor (NRF2)-mediated up-regulation of 'phase 2' genes that neutralize oxidative stress and metabolize electrophiles. We had previously shown that small doses of blue light (400-500 nm) had selective toxicity for cultured oral tumor cells and increased levels of peroxiredoxin phase 2 proteins, which led to our hypothesis that blue light activates NRF2 signaling.
Materials And Methods:
A431 epidermoid carcinoma cells were treated in culture and as nude mouse xenografts with doses of blue light. Cell lysates and tumor samples were tested for NRF2 activation, and for markers of proliferation and oxidative stress.
Results:
Blue light activated the phase 2 response in cultured A431 cells and reduced their viability dose dependently. Light treatment of tumors reduced tumor growth, and levels of proliferating cell nuclear antigen (PCNA), and oxidized proteins.
Discussion:
Cellular responses to these light energies are worth further study and may provide therapeutic interventions for inflammation and cancer.
Insights
Blue light therapy activates the NRF2 pathway, reducing tumor cell viability and growth. This research suggests potential new treatments for inflammation and cancer using specific light wavelengths.
Area of Science:
- Biomedical Optics
- Photomedicine
- Cancer Research
Background:
- UVA light (320-400 nm) shows anti-inflammatory and antioxidative effects.
- These effects are linked to NRF2-mediated upregulation of 'phase 2' genes.
- Previous work indicated blue light (400-500 nm) selectively harms oral tumor cells.
Purpose of the Study:
- To investigate if blue light activates NRF2 signaling.
- To determine the effects of blue light on A431 epidermoid carcinoma cells and tumors.
Main Methods:
- A431 cells were treated with blue light in culture and as mouse xenografts.
- NRF2 activation, proliferation markers (PCNA), and oxidative stress were assessed.
Main Results:
- Blue light dose-dependently activated the phase 2 response in A431 cells, reducing viability.
- Tumor growth, PCNA levels, and oxidized proteins were decreased by blue light treatment.
Conclusions:
- Cellular responses to blue light warrant further investigation.
- Blue light may offer therapeutic potential for inflammation and cancer treatment.
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