Many studies have demonstrated the importance of spontaneous metastases in cancer research. Until now, we still had only a few spontaneous metastatic models with high occurrence rate of metastasis in distant lymph and visceral tissues. We report a syngeneic heterotopic metastatic model using the Lewis lung cancer cell line with high metastatic ratio in C57BL/6 mice after transplantation by injection of cancer cells and without surgical intervention. Metastatic process was declared for each mouse in two groups ?sacrificed 3 or 5 weeks after subcutaneous (s.c.) injection of the tumor cells into the dorsal side of the tail. The total number of metastases was counted as the sum of observed macrometastases. Our model produced produced a 100% rate of spontaneous lymphatic and visceral metastases after a simple injection transplantation into the heterotopic site. In mice with large primary tumors which are non-lethal, visceral and lymph macrometastases were observed. Tumor volume correlated linearly not only with the tumor growth time, but also with the number of metastases in lymph nodes and organs. This new metastatic model could be useful for studying the metastasis mechanism and for developing therapy for lymph and visceral metastases.

Department of Tumor Biology Charles University Prague Czech Republic

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