Table 1. Attractive features and potential pitfalls of drug-loaded nanoparticle systems incorporated in stem cell carriers.

Attractive Features	Potential Pitfalls
Sustained drug release to tumor cells	Low intratumoral distribution
Targeted incorporation in neoplastic cells	Drugs must be stably loaded into the stem cell carrier
Accepts incorporation of potent chemotherapeutic agents	Allorejection of heterologous stem cell carriers
High loading capacity per nanocarrier	Non-representative animal models
Oncotropic properties	Difficulties in controlling off-target toxicity
Able to reach invasive tumor areas	Difficulty in achieving controlled drug release