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Patient-derived xenograft (PDX) models are generated by engrafting primary human tumor tissue directly into immunodeficient mice, allowing in vivo propagation of patient tumor biology without initial in vitro adaptation. These models are used to preserve key histopathological and molecular characteristics of the original tumor and enable assessment of tumor growth dynamics and therapeutic response in a living organism. The biological readout is tumor engraftment and subsequent growth in the murine host, which reflects the ability of human tumor cells to survive, vascularize, and expand in an immunocompromised microenvironment.

Splenic and portal-vein liver metastasis xenograft models deliver tumor cells into the portal circulation so that cells reach the liver first and form hepatic metastatic lesions; splenic injection uses the spleen as an access route to the portal system, while direct portal-vein injection introduces cells into the portal vein without requiring splenectomy. The assay detects liver colonization, intrahepatic tumor growth, tumor distribution, treatment response, survival, and liver-metastasis microenvironment changes; readouts include bioluminescence or fluorescence imaging, gross liver nodule counts, liver weight or tumor burden, histology, and survival.

Subcutaneous cell-line-derived xenograft (CDX) models are established by implanting cultured human cancer cell lines into immunodeficient mice, where the injected cells form localized tumors that can be monitored in vivo as a measure of tumorigenic potential, growth kinetics, and treatment response. These models are widely used in oncology research because they allow reproducible tumor formation and enable comparative assessment of tumor growth between different cell lines or genetic manipulations in a controlled in vivo microenvironment. Subcutaneous implantation of cancer cells in immunodeficient mice is a standard approach for evaluating tumor growth behavior and therapeutic response across multiple cancer types, including prostate, esophageal, pancreatic, and colon cancer models.

Breast cancer is a heterogeneous cancer, and it has been distinguished into four subtypes: luminal A, luminal B, HER2-positive and basal-like. Molecular mutations, epigenetic alterations, hormone exposure and immune microenvironment are related to the progression of breast cancer.

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

Intraperitoneal (IP) or peritoneal dissemination xenograft models are based on the introduction of human cancer cells into the peritoneal cavity of immunodeficient mice, where they attach to peritoneal surfaces, form multicellular aggregates or spheroids, and progressively generate disseminated tumor nodules that mimic advanced peritoneal metastatic disease. These models are widely used to study ovarian cancer progression, tumor-microenvironment interactions, and intraperitoneal therapeutic responses, often incorporating bioluminescence or fluorescence imaging to longitudinally monitor tumor burden in vivo. The biological principle relies on the capacity of tumor cells such as SKOV3 or related ovarian carcinoma lines to survive in suspension, aggregate within ascites-like fluid, adhere to mesothelial surfaces, and invade peritoneal organs, thereby recapitulating human peritoneal carcinomatosis patterns observed in advanced disease.