FGFR1 and osteosarcoma: We elected to use U2OS cells as a model to identify the desired adaptor protein, as we found this human osteosarcoma cell line endogenously expressed FGFR1, 2, and 4 but had no detectable FGFR3 expression (Supplemental Figure 1; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.171257DS1).