Betulinic Acid a Radiosensitizer in Head and Neck Squamous Cell Carcinoma Cell Lines

Background and Purpose: Betulinic acid, a pentacyclic triterpene, is a new cytotoxic compound active on melanoma, neuroblastoma, glioblastoma and head and neck squamous cell carcinoma (HNSCC) cells. In combination with irradiation it has been shown to have an additive effect on growth inhibition in melanoma cells. In this study, the radiosensitizing effect of betulinic acid on sequential irradiation was investigated in HNSCC cell Lines. Material and Methods: Two HNSCC cell Lines, SCC9 and SCC25, were treated with increasing doses of betulinic acid and sequentially irradiated with a single boost of 4 Gy from a conventional radiation source. The cells were counted, the surviving fraction was determined, and colony-forming assays were performed. Results: It could be shown that betulinic acid atone inhibits cell survival, affects cell survival additively in combination with irradiation and decreases clonogenic survival in both cell tines when applied atone. Conclusion: Betulinic acid could be a promising treatment agent in radioresistant head and neck cancer. A combination of betulinic acid with radiotherapy seems to be beneficial.