Absorption, Distribution and Excretion of 14C-Probimane in Mice Bearing Lewis Lung Carcinoma 449 (formed metastatic foci) [15] and nevertheless Pro can be more effective in the inhibition of neoplasm metastasis than Raz in formed metastatic foci through stronger antiproliferative effect [8, 9] and drug accumulation. From this data of 14C-Pro tracing, an obvious greater accumulation of Pro was found in tumor tissues, especially in metastatic foci. It can help to explain why Pro might effectively inhibit pulmonary metastases of Lewis lung carcinoma by its higher accumulation and affinity to metastatic nodules which lead further into higher cytotoxicity against formed metastatic foci in living-bodies. This work shows that Pro can hardly penetrate into the blood-brain-barrier, and it suggests Pro might be less effective to brain tumors or against those other tumors which have been metastasized into the brains. This result is very similar with previously reported data of Raz by Greig N et al determined by a HPLC assay [16]. Acknowledgements We are thankful to Prof Xin Zhang’s lab, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, PR China for providing us with purified 14C-probimane. We are also grateful for Senior Technicians Fu-Geng Wu and Ze Hua at Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, PR China for assisting us determination of radioactivity of all tested tubes. Authors’ Statement Competing Interests The authors declare no conflict of interest. Animal Rights References The institutional and (inter)national guide for the care and use of laboratory animals was followed. See the material and methods part for details. [1] [2] [3] [4] Taraboletti G. Margosio B. Antiangiogenic and antivascular therapy for cancer. Curr Opin Pharmacol. 2001; 1: 378–384. doi:10.1016/S1471-4892(01)00065-0 Sava G, Bergamo A. Drug control of solid tumour metastases: a critical view. Anticancer Res. 1999; 19: 1117–1124. PMid:10368662 Lu DY, Huang M, Zhou J, Ding J. Recent advances in anti-metastatic drug development. Acta Pharmacol Sin. 2006; 27 (Suppl): 66–67. Hellmann K, Burrage K. Control of malignant metastases by ICRF-159. Nature. 1969; 224: 273–275. doi:10.1038/224273a0 Sci Pharm. 2010; 78: 445–450.