Patient-derived xenograft mice are supposed to recapitulate patients' tumors so researchers can better model tumors or even so clinicians use them to choose a treatment approach. But as Nature News reports, these models have some limitations.
For instance, the tumors begin to diverge from their source tumors over time, which could mean they respond differently to treatments than the patients would, Nature News says. One study tested different treatments on 250 patient-derived xenograft mice to find that all responded as predicted based on human data, though another research group found three cases in that dataset where genomic alterations could have affected their responses.
Another limitation, Nature News says, is the approach's reliance on mice that lack an immune system — that is the only way to get the xenografts to take root. But it also prevents researchers from testing immunotherapies on them. It notes, however, that researchers at the Jackson Lab are working on getting stem cells from human umbilical cords to develop into immune cells in these mice.