Effects of photodynamic therapy on the proliferation and apoptosis of human papillomavirus type 16 E7 protein-expressing HaCaT cells

Abstract

Objective To explore the effects of aminolevulinic acid-based photodynamic therapy (ALA-PDT) on the proliferation and apoptosis of HaCaT cells stably expressing human papillomavirus type 16 E7 protein (HaCaT/HPVl6 E7 cells) . Methods Cultured HaCaT/HPV16 E7 cells were divided into several groups: blank control group receiving no treatment, ALA group treated with ALA alone, irradiation group irradiated with 630-nm red laser (30 mW/cm2, 12 J/cm2) , ALA-PDT groups pretreated with ALA for 5 hours followed by 630-nm red laser radiation at 4, 8, 12 J/cm2 respectively. CCK8 assay was performed to determine the survival rate of cells at 24 hours after PDT, and flow cytometry and confocal microscopy were conducted to detect cell apoptosis and observe cell morphology respectively at 3 hours. Results At 24 hours, the survival rate of cells was 68.98% ± 1.03%, 46.03% ± 2.96% and 23.57% ± 3.83% in the 4-, 8- and 12-J/cm2 ALA-PDT groups respectively, significantly lower than that in the blank control group, ALA group and irradiation group (99.15% ± 0.64%, 98.13% ± 0.83% and 96.85% ± 1.37% respectively, all P< 0. 05). With the increase in radiation dose, cell apoptosis was accelerated with obvious morphological changes and shrinkage of cells in the ALA-PDT groups. Conclusion ALA-PDT can inhibit the proliferation, and promote the apoptosis of HPV-infected HaCaT cells in a dose-dependent manner within a certain range of radiation dose. Key words: Aminolevulinic acid; Photochemotherapy; Cell proliferation; Apoptosis; Alphapapillomavirus; HPV16 E7