Pepper Alkaloid Piperine Increases Radiation Sensitivity of Cancer Cells from Glioblastoma and Hypopharynx In Vitro

In our study, our aim was to examine the cytotoxic and radio-sensitizing effect of the alkaloid piperine, a major pungent of black pepper, on two different human epithelial tumor cell lines in vitro. The growth of the human cell lines T98G (glioblastoma) and FaDu (hypopharyngeal carcinoma) was examined under the influence of piperine in different concentrations. In addition, after combined treatment with ionizing radiation, long-term survival was investigated with a colony formation assay. The proliferation was analyzed using the BrdU-assay, while the DNA repair capacity was examined via the gamma H2AX assay. Piperine reduced the growth of both cell lines in a concentration-dependent manner as well as a time-dependent one. After combined treatment with piperine and ionizing radiation, an inhibition of clonogenic survival could be proven. A reduced proliferation capacity and an additive effect on DNA damage 24 h after irradiation are possible causal mechanisms, which were also demonstrated for both cell lines. Based on the results presented in this study, piperine was shown to have cytotoxic antitumor activity and a radio-sensitizing effect in micromolar concentrations in the human tumor cells that were tested. Based on these results piperine represents a potential therapeutic option in radio-oncological treatment.