Monoterpenes enhanced the sensitivity of head and neck cancer cells to radiation treatment in vitro

Background: Perillyl alcohol (POH) elicited anticarcinogenic effects in a number of cancer models and pharmacokinetic studies in humans revealed that PA is the major circulating metabolite following POH administration. Materials and Methods: Effects of PA or POH alone, or in combination with radiation, on human head and neck squamous cell carcinoma cell lines (HNSCC), were investigated using cytotoxicity and flow cytometry assays. HNSCC cells were pretreated with 1.0 mM PA or 0.5 mM POH for 72 h before exposure to 1 or 2 Gy dose of radiation. Results: Pretreatment of the cells with 1.0 mM PA or 0.5 mM POH prior to irradiation, caused the following growth inhibition: HTB-43 (50% or 71%), SCC-25 (55% or 68%), and BroTo (18% or 53%). PA and POH induced cell-cycle arrest and apoptosis. Conclusion: PA and POH have potential for use as radiosensitizers in chemo-radiation therapy of head and neck cancers and should be further studied.