Photobiomodulation with blue light is used for several treatment paradigms such as neonatal jaundice, psoriasis and back pain. However, little is known about possible side effects concerning melanoma cells in the skin. The aim of this study was to assess the safety of blue LED irradiation with respect to proliferation of melanoma cells. For that purpose we used the human malignant melanoma cell line SK-MEL28. Cell proliferation was decreased in blue light irradiated cells where the effect size depended on light irradiation dosage. Furthermore, with a repeated irradiation of the melanoma cells on two consecutive days the effect could be intensified. Fluorescence-activated cell sorting with Annexin V and Propidium iodide labeling did not show a higher number of dead cells after blue light irradiation compared to non-irradiated cells. Gene expression analysis revealed down-regulated genes in pathways connected to anti-inflammatory response, like B cell signaling and phagosome. Most prominent pathways with up-regulation of genes were cytochrome P450, steroid hormone biosynthesis. Furthermore, even though cells showed a decrease in proliferation, genes connected to the cell cycle were up-regulated after 24h. This result is concordant with XTT test 48h after irradiation, where irradiated cells showed the same proliferation as the no light negative control. In summary, proliferation of melanoma cells can be decreased using blue light irradiation. Nevertheless, the gene expression analysis has to be further evaluated and more studies, such as in-vivo experiments, are warranted to further assess the safety of blue light treatment.
Blue light is known for its anti-microbial, anti-proliferative and anti-inflammatory effects. Furthermore, it is already used
for the treatment of neonatal jaundice and acne. However, little is known about the exact mechanisms of action on gene
The aim of this study was to assess the impact of blue LED irradiation on the proliferation and gene expression in
immortalized human keratinocytes (HaCaT) in vitro. Furthermore its safety was assessed.
XTT-tests revealed a decrease in cell proliferation in blue light irradiated cells depending on the duration of light
irradiation. Moreover, gene expression analysis demonstrated deregulated genes already 3 hours after blue light
irradiation. 24 hours after blue light irradiation the effects seemed to be even more pronounced. The oxidative stress
response was significantly increased, pointing to increased ROS production due to blue light, as well as steroid hormone
biosynthesis. Downregulated pathways or biological processes were connected to anti-inflammatory response.
Interestingly, also the melanoma pathway contained significantly downregulated genes 24 hours after blue light
irradiation, which stands in accordance to literature that blue light can also inhibit proliferation in cancer cells. First tests
with melanoma cells revealed a decrease in cell proliferation after blue light irradiation. In conclusion, blue light
irradiation might open avenues to new therapeutic regimens; at least blue light seems to have no effect that induces
cancer growth or formation.