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A suppository kit for metronomic photodynamic therapy: The elimination of rectal cancer in situ

Shi, X.F., Jin, W.D., Gao, H., Yin, H.J., Li, Y.X., Huang, H., Ma, H., Dong, H.J.
Journal of photochemistry and photobiology 2018 v.181 pp. 143-149
apoptosis, carcinoma, colorectal neoplasms, encapsulation, epoxides, fatty acids, histopathology, magnetic resonance imaging, models, neoplasm cells, photochemotherapy, rabbits, staining
Metronomic photodynamic therapy (mPDT) was developed to improve tumor-specific responses through cell death by apoptosis. We developed an mPDT suppository kit including ALA and LED suppositories and analyzed its killing effect on rectal tumors in rabbits. Methods: The ALA (10 wt%) suppository was prepared using ALA powder, type 36 semi-synthetic fatty acid glyceride, and azone. The LED suppository was constructed by encapsulating LED units and a circuit in transparent epoxy resin. VX2 cells were injected into the rectal submucosa of rabbits to establish a carcinoma model in situ. The ALA suppository was inserted into the rectal cavity for 30 min of uptake and activated for 1 h by the LED suppository at a power density of 20 mW/cm2. The mPDT process was repeated three times once a day. MRI was used to monitor tumor growth, histopathology and TUNEL staining were performed at 14 days after mPDT. Results: The overall response rate was 60% in the mPDT group using the kit in which the tumor size was decreased up to about 50% at 7 days post-mPDT and almost eliminated at 14 days. HE staining showed that only 6.16% of the tumor tissue remained after mPDT treatment. TUNEL detection showed that the apoptosis rate was 18.9%. Conclusion: We verified the killing effect of the mPDT suppository kit on rectal tumors in rabbits based on mPDT that induced tumor cell apoptosis.