Mechanisms underlying the effect of 5-aminolevulinic acid photodynamic therapy on cutaneous squamous cell carcinoma in SKH-1 mice / 中华皮肤科杂志

ABSTRACT

Objective To investigate the mechanisms underlying the effect of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) on cutaneous squamous cell carcinoma (SCC) in mice.Methods A model of cutaneous SCC was established in 21 SKH-1 hairless mice,which were treated with topical ALA 8％ cream followed by single irradiation with He-Ne laser at a total dose of 30 J/cm2 (ALA-PDT).Three mice were sacrificed before and at 1,3,6,12,24 hours and 7 days after the irradiation,separately,and SCC tissue was taken from the mice.Transmission electron microscopy (TEM) and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) were performed to determine the pattern of tumor cell death(necrosis,apoptosis and autophagy) during 1-24 hours after ALA-PDT,and immunohistochemical techniques were used to estimate the expressions of LC3B and CD34 on SCC cells,as well as the quantity of CD1a+ cells,CD4+ T and CD8+ T lymphocytes in SCC tissue 7 days after the irradiation.Statistical analysis was done by two-sample t test using SPSS 17.0 software.Results TEM showed gradual necrosis and apoptosis (especially necrosis) of tumor cells and formation of autophagosomes in macrophages within 24 hours after ALA-PDT.The number of apoptotic cells per high power field (× 400) in SCC tissue significantly increased at 24 hours compared with that before ALA-PDT (7.30 ± 2.18 vs.2.00 ± 0.69,P ＜ 0.05).As immunohistochemistry revealed,there was a significant decrease in the number of CD34+ cells (1.33 ± 0.58 vs.19.00 ± 2.66,P＜ 0.01),but a marked increase in that of CD1a+ ce1ls (23.01 ± 2.04 vs.10.33 ± 1.88,P＜ 0.05),CD4+ T cells (28.67 ± 1.76 vs.12.40 ± 2.27,P＜ 0.05),CD8+ T cells (25.79 ± 2.37 vs.11.67 ± 1.45,P ＜ 0.05) and LC3B+ interstitial cells (30.6 ± 3.21 vs.21.44 ± 4.3,P ＜ 0.05) per high power field (× 400) in SCC tissue on day 7 compared with that before ALA-PDT.Conclusions ALA-PDT may directly kill SCC cells by inducing cell necrosis and apoptosis rather than autophagy.Additionally,ALA-PDT can injure microvascular endothelial cells and cause the aggregation of dendritic cells,CD4+ T cells and CD8+ T cells in SCC tissue.