GPC3 and hepatocellular carcinoma: Table 1 shows the quality assurance characteristics of the 89Zr-Df-H3K3 tracer (n = 3). The 89Zr-Df-H3K3 tracer demonstrated 69.6 ± 3.2% (mean ± SD) immunoreactivity towards HCC PDX622 cells that express GPC3 (Figure S4). These data confirmed the high quality and specificity of 89Zr-Df-H3K3, which makes it a suitable immunoPET tracer for targeting human GPC3 expressed in orthotopic HCC PDX mouse models.