Abstract
To investigate whether a carbon ion beam has beneficial effects compared to X-rays by targeting putative cancer stem cells, human liver cancer stem-like cells sorted from HepG2 and Huh7 cells were treated with or without carbon ion or X-ray irradiation and then colony formation assay, spheroid formation assay, FACS analysis, as well as in vivo tumorigenesis analyses were performed. FACS analysis showed that the proportion of CD133+/CD90+, CD44+/ESA+ cells were 6.4% and 1.5 % in Huh7, whereas only 0.6% and 0.2% in HepG2 cells. The proportion of CD133+/CD90+, CD44+/ESA+ was more significantly enriched by X-rays compared to carbon-ion beam. CD133+/CD90+ and CD44+/ESA+ cells significantly have higher number of colony and spheroid compared to CD133-/CD90- and CD44-/ESA- cells. In addition, CD133+/CD90+ and CD44+/ESA+ cells have shown more potential to form tumors in SCID mice than CD133-/CD90- and CD44-/ESA- cells. Colony assay showed that CD133+/CD90+ and CD44+/ESA+ cells appeared to be radioresistant to both X-ray and carbon ion beam, but carbon beam was more effective at killing those of cancer stem-like cells. In conclusion, CD133+/CD90+ and CD44+/ESA+ cells are putative liver cancer stem cells, and carbon ion beam potentially benefit for targeting liver cancer stem-like cells compared to X-rays.
