Hesperidin structurally modified by gamma irradiation induces apoptosis in murine melanoma B16BL6 cells and inhibits both subcutaneous tumor growth and metastasis in C57BL/6 mice.

Hesperidin is a flavonoid which occurs in citrus fruits. Hesperidin was gamma-irradiated at doses of 0, 30, 70, and 150 kGy. Gamma irradiation induced a decreased hesperidin peak, and a new radiolytic peak that gradually increased up to 150 kGy. The new radiolytic peak was fractionated, and the fractionated hesperidin derivative was used for subsequent experiments. Hesperidin gamma-irradiated at 150 kGy was toxic toward B16BL6 cells, but not toward bone marrow-derived macrophages. This cytotoxicity was exerted via induction of apoptosis, as reflected by the high population of double-positive cells, increased sub-G1 phase cells, depolarization of matrix metalloproteinase, production of reactive oxygen species, weakness of cell adhesion, changes in cell morphology, and inhibition of B16BL6 cell migration. Furthermore, 150 kGy gamma-irradiated hesperidin decreased the expression of Bcl-2 and pro-caspases-3 and -9, increased the expression of Bax and cytosolic cytochrome c, and increased the cleavage of poly ADP ribose polymerase. In vitro mechanistic study revealed that 150 kGy gamma-irradiated hesperidin achieved significantly greater inhibition of lung metastasis and growth of melanoma B16BL6 cells in C57BL/6 mice than non-irradiated intact hesperidin did. These results suggest that the structural modification of hesperidin induced by gamma irradiation could facilitate the development of anti-cancer drugs.