Table 1: Main advantages and disadvantages of GEM, XG, and PDX mouse models.

AdvantagesDisadvantages

Genetically engineered mice
(GEM)
(i) Studies on defined mutations
(ii) Possibility to follow tumor development from early time points
(iii) Tumor microenvironment is representative of the studied tumor
(iv) Potential analysis of effects of mutations in many genetic backgrounds by using a variety of mouse strains
(i) Limited number of genes (usually not representative of the heterogeneity of the tumor)
(ii) Development costly and time consuming
(iii) Tumor development in animals slow and variable
(iv) Both, tumor and microenvironment are murine

Xenograft
(XG)
(i) Allows a rapid analysis of response to a therapeutic regimen
(ii) Source of material virtually unlimited for immortal cell lines
(iii) Can predict drug response of human patient’s tumor
(i) Human tumor microenvironment is not represented
(ii) Orthotopic implant is often technically complicated
(iii) Cells can undergo genetic modification as well as subpopulation rearrangements when cultured

Patient-derived xenograft
(PDX)
(i) Provides a realistic representation of the heterogeneity of tumor cell subpopulations
(ii) Can predict drug response of human patient’s tumor
(iii) Stromal component is representative of the parental tumor in the initial passages
(i) Orthotopic implant is often technically complicated
(ii) Surgical fragments must be processed rapidly
(iii) Limited source of original material