DPP4 and neoplasm: In addition, we surprisingly found that expressions of angiogenesis-related gene HIF1α and metastasis-related gene CD26 were significantly suppressed or lost by carbon ion beam combined with CDDP, whereas carbon ion beam alone or X-ray combined with CDDP increased HIF1α, implying that carbon ion beam in combination with CDDP may effectively inhibit tumor angiogenesis and metastasis (Fig. 4d).