Histological analyses revealed that the mixed-tumor group exhibited greatly increased numbers and sizes of lung metastases compared to the VHL-WT group (Fig. 2d).35 The in vivo growth and metastatic behavior of the RC tumors were further verified in the CAM tumor system,36,37 substantiating the poor growth of VHL-KO tumors (Fig. 2e) and the heightened metastatic spread of the mixed tumors with increased circulating tumor cells (Fig. 2f). This evidence concerns the gene VHL and neoplasm.