Abstract
The effects of high LET carbon-ion (C290, 50keV/um, 6-cm SOBP) irradiation on tumor control and cancer stem cells of HCT116 xenograft tumors were investigated. The tumor growth delay (TGD) was 5 and 28 days after irradiated with15 and 30 Gy X-ray, whereas the TGD was 12 and 82 days after irradiated with 5 or 15 days carbon ion. The tumors were eradicated without relapse when irradiated with 60 Gy X-ray or 30 Gy carbon ion. The relative biological effects (RBE) value of carbon-ion relative to X-rays was 3.82. Carbon-ion irradiation predominantly induced tumor cell cavitation, fiborosis and completely disrupted the duct-like architecture. Tumor-supplying vessels were reduced in carbon-ion irradiated mice compared to those of X-ray irradiated mice. Expression of VEGF, HIF-1a, and cancer stem cell marker CD133, EpCAM was markedly suppressed by 30 Gy carbon-ion irradiation, whereas 30 Gy X-ray increased the expression of these proteins. In conclusion, heavy-ion irradiation can more effectively control xenograft tumors than X-ray through suppression of angiogenesis and disruption of cancer stem cells.
