Table 1.

The three most common types of PDX models for cancer research (modified from Byrne et. al. 2017) [11].

PDX Models	Advantages	Disadvantages
(1) Primary tumor specimens implanted subcutaneously (PDX-SC)	Intact primary tumor tissue and architecture Captures clonal diversity Easy to measure tumor responses Intravital tumor imaging	No proper anatomical niche Only suitable for higher grade, more aggressive tumors
(2) Primary tumor specimens implanted orthotopically (PDOX)	Intact primary tumor tissue and architecture Matching primary tumor in context Metastasis assessment from primary tumor Both primary and metastatic tumor niche Recapitulates metastatic process Ability to mimic clinical scenarios	Need extra technology to visualize tumor Challenging microsurgical skills Impossible for large collections and high throughput engraftment
(3) Humanized mouse (HM) models	Recapitulates human immune system in mice	Lengthy mouse humanization procedures Hurdles to achieve complete human immunity reconstitution