Xenograft models are a type of preclinical research model used in cancer research to study the behavior of human tumors in living organisms. In a xenograft model, human tumor cells are transplanted into an animal (typically a mouse) to create a tumor that can be studied and manipulated in vivo.

The most common type of xenograft model involves injecting human tumor cells subcutaneously or orthotopically (into the tissue where the tumor originates) into immunodeficient mice. These mice lack an immune system that would reject the human tumor cells, allowing the tumor to grow and be studied. Other types of xenograft models involve transplanting human tumor tissue or patient-derived xenografts (PDX) into mice.

Xenograft models have several advantages for cancer research. They can provide insights into tumor growth, invasion, and metastasis in a more complex and dynamic environment than traditional cell culture models. They can also be used to test the efficacy of new cancer drugs and therapies in vivo before moving on to clinical trials in humans. Additionally, xenograft models can be used to study tumor heterogeneity and identify potential biomarkers for cancer diagnosis and treatment.

However, there are also limitations to using xenograft models. Human tumors transplanted into animals may not accurately recapitulate the complex biology and microenvironment of the original human tumor. Furthermore, the use of immunodeficient mice may not fully capture the role of the immune system in cancer development and progression. Nonetheless, xenograft models remain an important tool for cancer research and drug development.