Improve efficacy of topical ALA-PDT by calcipotriol through up-regulation of coproporphyrinogen oxidase

• ALA-PDT could be improved by calcipotriol for oral cancer cells.
• Topical ALA-PDT could be improved by calcipotriol for oral precancers in vivo.
• Coproporphyrinogen oxidase level elevated significantly at 10−8 M calcipotriol.

SummaryBackgroundTopical 5-aminolevulinic acid-mediated photodynamic therapy (topical ALA-PDT) is effective for treating oral precancerous lesions. The aim of this in vivo and in vitro study was to examine whether the efficacy of topical ALA-PDT could be further improved by calcipotriol (CAL).MethodsPrecancerous lesions in the buccal pouch of hamsters were induced by dimethylbenz(a)anthracene (DMBA). Lesions were treated with multiple topical ALA-PDT with or without CAL pretreatment. ALA-induced protoporphyrine IX (PpIX) was monitored by in situ fluorescence measurement. The effect of CAL on heme-related enzymes (CPOX, PPOX, and FECH) were examined in an in vitro model using human squamous cell carcinoma (SCC) cells (SCC4, SAS) using Western blots.ResultsFluorescence spectroscopy revealed that PpIX reached its peak level in precancerous epithelial cells of buccal pouch at 2.5 or 3.5 h without or with CAL pretreatment, respectively. Both treatment regimens showed similar response rates, but the complete response was achieved after 5 times of ALA-PDT and 3 times of CAL-ALA-PDT (p < 0.001). Pretreatment of SCC cells with 10−8 or 10−7 M CAL could result in a significant cell death (p < 0.05) and an elevation of CPOX protein level.ConclusionTopical CAL can improve the efficacy of ALA-PDT in treating precancerous lesions, likely through the increase in CPOX level and in PpIX production.