Particle
radiotherapy such as
proton and
carbon ion has been producing promising clinical results worldwide. The purpose of this study was to compare metastatic capabilities of malignant
tumor cells after irradiation with photon,
proton, and
carbon ion beams to clarify their ion beam-specific biological effects. We examined the biological properties of highly aggressive HT1080 human
fibrosarcoma cells to assess their metastatic processes in terms of cell adhesion capability to extracellular matrix, expression of
integrins, cell migration, cell invasive capability, and
matrix metalloproteinase-2 activity in vitro. We then assessed the metastatic capabilities of LM8 mouse
osteosarcoma irradiated with
carbon ion or photon beam in the syngeneic mice. Both
proton and
carbon ion irradiation decreased cell migration and invasion in a dose-dependent manner and strongly inhibited
matrix metalloproteinase-2 activity. On the other hand, lower X-ray irradiation promoted cell migration and invasion concomitant with up-regulation of
alphaVbeta3 integrin. For
cancer cells treated with
carbon ion irradiation, the number of pulmonary
metastasis was decreased significantly in vivo. These findings suggest that particle irradiation suppresses metastatic potential even at lower dose, whereas photon irradiation promotes cell migration and invasive capabilities at lower dose level, and provide preclinical evidence that ion beam
radiotherapy may be superior to conventional photon beam
therapy in possible preventive effects on
metastases of irradiated malignant
tumor cells.