Generating Cell or Tissue Transplants in Mice
The study of cancer is complicated for many reasons. The challenges include the variability of primary cancers which originate from different tissues, the heterogeneity within tumors, as well as from the problems of metastatic cancer. Cancer that has originated in one tissue but has spread to another tissue is particularly challenging to understand, in part because of the possible complexities of the tissue micro-environment in the new location. Further, the immune system may affect the biology of tumors, and species variations in that system may impact our understanding. Utilizing cell or tissue transplants in controlled background environments may help us to evaluate the behavior and characteristics of the tumors.
Cell or Tissue Transplants
Among the earliest major projects to better understand cancer biology included transplants of leukemia cells into inbred mice, to examine the effects of possible treatment agents. Blood cancers were particularly suited to this type of examination. Sarcoma, melanoma, lung cancer and adenocarcinoma models and others had also been established. These well-studied transplant defined mouse tumor models became foundational tools for assessing behaviors of tumors and of therapeutics. These types of syngenic models (mouse tumors in mice) offered valuable insights, and continue to be used. In addition, mice can also be used as hosts for other types of animal tumors.
However, as with all animal model systems, there are potential concerns about the fidelity of the model to human cancers and their treatments. Some researchers choose to study human tumors which are placed into mouse models, called xenograft experiments. Special immune-compromised mice have been developed to accommodate these studies. Athymic (nude) mice may be used, and mice with "humanized" immune system components have been generated.
The experimental goals will determine the appropriateness of the model to use. Both transplanted tumor models and genetically engineered mice are available for researchers, and can be used effectively to learn more about human cancer biology. The particular cancer type to be studied, and the appropriate model system for the investigation, need to be carefully considered to determine the suitable model system and tools.
Stem cells for treatments
Another aspect of investigation underway for cancer treatment involves transplantation of stem cells as vectors for anti-tumor therapies. Currently being studied in a wide array of mouse models, these methods could yield great benefits especially for tumor situations that have been less amenable to chemotherapies.