Tumor Metastasis Model

Model Introduction

This model involves constructing xenograft models by transplanting human-derived tumor cell lines or primary tumor tissues into immunodeficient mice (e.g., BALB/c nude, SCID, or NOD/scid mice). Based on the site of inoculation, it can be categorized into subcutaneous transplantation, orthotopic transplantation, and special-site transplantation. Among these, the orthotopic model, by inoculating the tumor into the primary organ, more realistically simulates the local microenvironment, invasion, and distant metastatic behavior (e.g., liver, lung, and lymph node metastasis), serving as a core tool for studying tumor metastasis mechanisms and evaluating anti-metastatic drugs.

Research Applications

1. Efficacy Screening: Subcutaneous xenograft models are commonly used for tumor growth inhibition assays and preliminary drug screening.
2. Metastasis Mechanism Research: Orthotopic models (e.g., pancreatic cancer orthotopic models, colorectal cancer liver metastasis models) are used to simulate tumor invasion processes and multi-organ metastatic pathways.
3. Specific Disease Simulation: Intracranial transplantation models are used for central nervous system tumors like gliomas; drug-resistant models are used to develop strategies for reversing tumor resistance.
4. Translational Research: Utilizing Patient-Derived Xenografts (PDX) to maintain tumor heterogeneity for studying biological characteristics closer to clinical reality.

Key Points of Experimental Design

1. Experimental Animal Selection: BALB/c nude, SCID, or NOD/scid mice are commonly used. Mice of appropriate age that are sensitive to the tumor and possess suitable immune development status must be selected.
2. Cell/Tissue Processing:
   • Cell Lines: Use cells in the logarithmic growth phase, washed with sterile PBS to remove serum. The inoculation density is typically $5 \times 10^6$ to $1 \times 10^7$ cells per animal.
   • Primary Tissue: Fresh surgical specimens must be cut into $1–2 \text{ mm}^3$ fragments for inoculation.
3. Modeling Procedures:
   • Subcutaneous Transplantation: Injection volume is 0.1–0.2 mL; a “four-point, two-block” trocar inoculation method may be employed.
   • Orthotopic Transplantation: Such as surgical transplantation of tumor tissue into the pancreas or inoculation onto the cecal wall to induce liver metastasis.
   • Special Sites: Precise intracranial injection using a stereotaxic instrument.
4. Environmental Quality Control: The entire experiment must be performed in an SPF barrier environment with strict control over temperature, humidity, feed, and water.

Key Monitoring Indicators

1. Tumor Growth Curve: Periodic measurement of the long and short diameters of the tumor to calculate tumor volume.
2. Pathological Characteristics: HE staining to observe whether the histomorphological structure is consistent with the primary tumor.
3. Immunophenotype: Use of Immunohistochemistry (IHC) to detect epithelial markers like Cytokeratin (CK) and other specific tumor markers.
4. Biochemical Indicators: Detection of characteristic tumor markers secreted by the xenograft (e.g., hCG) using ELISA technology.
5. Cell Kinetics: Use of Flow Cytometry to detect cell cycle and apoptosis rates.
6. Metastasis Rate Assessment: For orthotopic models, the incidence of metastasis in distant organs (liver, lungs, lymph nodes) must be monitored and statistically analyzed.