SK-216

Tail-vein experimental metastasis xenograft models assess the ability of injected tumor cells to survive circulation, arrest in vascular beds, extravasate, and colonize distant organs, most commonly lung after lateral tail-vein injection; this model bypasses primary-tumor formation, local invasion, and intravasation, so the readout reflects late metastatic colonization rather than the full metastatic cascade. The main readouts are metastatic burden measured by bioluminescence imaging, gross metastatic nodules, histology, organ weight, survival, or ex vivo tumor-cell quantification; luciferase-labeled tumor cells permit longitudinal noninvasive monitoring, while histology confirms organ colonization and tissue localization.

Orthotopic cell-line xenograft models involve implantation of human cancer cell lines into the anatomically corresponding organ of immunodeficient mice to reproduce tumor growth within a native microenvironment, enabling more clinically relevant tumor behavior compared with subcutaneous models. These models are widely used because orthotopic placement better recapitulates tumor progression, including invasion and metastatic spread, which are often underrepresented in heterotopic implantation systems. Compared with conventional xenografts, orthotopic implantation is described as more technically complex but provides improved simulation of tumor-microenvironment interactions and metastatic behavior, making it particularly valuable for translational oncology research. Surgical orthotopic implantation approaches have been emphasized as enabling faithful reproduction of clinical cancer features, including metastasis and disease progression patterns that align with the tumor’s organ of origi