TABLE 1.

Comparison between the different mouse models, with advantages and drawbacks

Animal model	Advantages	Drawbacks
Sporadic/chemical induced	✓Easy to perform ✓Similar to the carcinogenic process in human	✓Low tumor development ✓Wide variability in location, diffusion and differentiation ✓Long time for tumor development
Carcinogens in situ	✓Similar to the carcinogenic process in human ✓Bypasses enzymatic alterations	✓Low tumor development ✓Long time for tumor development
Peritoneum models	✓Easy to perform ✓Quick results ✓Good for antitumoral drugs tests	✓Biological behavior does not mimic/replicate human tumors ✓Biological behavior difficult to predict, usually with disseminated and advanced disease
Subcutaneous xenografts	✓Use of human cancer cells ✓Quick and easy to use	✓Heterotopic inoculation of the tumor is not a physiologic process ✓Low immune system activity ✓Tumoral cancer cells and stromal cells are from different species ✓Nonmetastatic ✓Difficult to predict the response to antitumoral drugs
Orthotopic xenografts	✓Use of human cancer cells ✓Histology is similar to the human tumors ✓Metastatic potential ✓Replicates the local invasion process by the tumor, with lymphovascular invasion ✓Allows genetic manipulation	✓Low immune system activity ✓Tumoral cancer cells and stromal cells are from different species ✓Unable to replicate the initial steps of disease ✓Less tumor formation than subcutaneous xenografts ✓Difficult to predict the response to antitumoral drugs
Syngenic	✓Tumor cells and stroma are from the same specie ✓Intact immune system	✓Endogenic animals does not allow the study of genetic modifiers ✓Low number of metastases
Genetic engineered mouse models	✓Genetic event is known ✓In situ tumor development ✓Reproduces early stages of oncogenesis ✓Modified gene is expressed on physiologic level ✓Tumor cells and stroma are from the same specie ✓Intact immune system ✓Used for chemoprevention studies	✓Only partial replication of the human tumoral morphology and physiology ✓Secondary mutations are different from the human tumors ✓Rarely metastatic ✓Response capacity to antitumoral drugs still unknown