Journal Article Repeated photon and C-ion irradiations in vivo have different impact on alteration of tumor characteristics.

佐藤, 克俊  ,  新田, 展大  ,  青木, 伊知男  ,  今井, 高志  ,  下川, 卓志

Precise characterization of tumor recurrence and regrowth after radiotherapy are important for prognostic understanding of the therapeutic effect. Here, we established a novel in vivo mouse model for evaluating the characteristics of regrown tumor after repeated photon and carbon ion (C-ion) irradiations. The results showed that tumor growth rate, lung metastasis, shortening of the survival of the tumor-bearing mice, and tumor microvessel formation were promoted 2- to 3-fold, and expression of angiogenic and metastatic genes increased 1.5- to 15-fold in regrown tumors after repeated photon irradiations, whereas repeated C-ion irradiations did not alter these characteristics. Interestingly, both repeated photon and C-ion irradiations did not generate radioresistance, which is generally acquired for in vitro treatment. Our results demonstrated that the repetition of photon, and not C-ion, irradiations in vivo alter the characteristics of the regrown tumor, making it more aggressive without acquisition of radioresistance.

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