Transplantation Mouse Models
Transplantation models offer another strategy for cancer researchers. These methods include various systems and techniques to propagate tumor tissues in different hosts for controlled studies in vivo. Some of these methods have been used for decades and are well-established models, others are more recent and continue to develop. As with any method, the interpretations of the outcomes should consider the benefits and limitations of the particular strategy and model system.
Allograft transplantation models
Allograft mouse tumor systems, also known as syngeneic models, consist of tumor tissues derived from the same genetic background as a given mouse strain. Cancerous cells or solid tumors are transplanted into a host mouse. Because the cancer tissues and the recipient share ancestry, the transplant is not rejected by the host’s immune system. Researchers may then monitor the tissues for changes such as growth or shrinkage, metastasis, and survival rate. Therapeutic interventions can be performed and the results are assessed to understand the treatment potentials. An advantage of syngeneic models is that the host immune system is normal, which may more closely represent the real life situation of the tumor’s micro-environment. A disadvantage is that the transplanted mouse tissue may not fully represent the complexity of human tumors in clinical situations.
Xenograft transplantation models
Another transplantation model is called a xenograft. This method involves actual human cancer cells or solid tumors which are transplanted into a host mouse. The host mice are special, though—they have impaired immune systems and the foreign cells will not be rejected by the host. These transplants may be orthotopic, meaning that the tumor is placed in the site it would be expected to arise naturally in the host: human liver tumor cells placed in the mouse’s liver. Or they may be subcutaneous, or placed just beneath the host’s skin. An advantage of xenografting is that the studies of the cancerous tissue employ real human cancers. Because the cancer carries human genetic material it may be more representative of the properties and mutations of the human cancer. On the other hand, because of the changes to the host immune system, it may not mimic the situation in actual patients. Ongoing studies to “humanize” the host mice may overcome some of the challenges of xenografting strategies.
The complexities and strategies of xenograft studies are beyond the scope of this site. The main focus here is the exploration cancer mechanisms in animal model systems as a means to learn about the parallels to human biology, and thereby leading to the treatment of human cancers. But for some investigations these valuable methods may be an appropriate choice.
For additional details on the process of utilizing transplantation methods, explore the Generating Cell or Tissue transplants area of this site.